Hirschsprung's disease

Chapter 48 Hirschsprung’s disease Anthony Stallion and Tzuyung Doug Kou HISTORY In 1886 Harald Hirschsprung gave the first comprehensive account of the condition that now bears his name. It was in 1888 that he summarized his findings in a publication entitled ‘Constipation in newborns as a consequence of dilatation and hypertrophy of the colon’, in which he gave a typical clinical presentation of the infants he had encountered. Hirschsprung suggested that the condition was congenital, but did not offer any specific etiology or therapeutic option.1 He had noted a somewhat narrow rectum in one of his early cases, but did not fully understand that the cause of the megacolon was the non-dilated distal bowel. The recognition of distal intestinal obstruction as the pathologic basis of Hirschsprung’s disease (HD) was not discovered until the early twentieth century. It was not until 1945 that a group of physicians led by Orvar Swenson at the Boston Children’s Hospital was able to determine that the disease process of HD was secondary to functional distal obstruction. The functional obstruction results from chronic contraction of the distal rectum with secondary proximal bowel dilation.2 Swenson’s group was able to document that the internal pressure of the distal segment of bowel was higher than that in the normal colon, which also had no peristalsis. Eventually it was recognized that there is an absence of ganglion cells in HD, specifically of Auerbach’s plexus in the distal segment of bowel. In addition, it was subsequently demonstrated that removal of this abnormal segment of bowel with anastomosis of the proximal bowel to the anus resulted in resolution of the problem. Swenson and Bill in 1948 were the first to advocate fullthickness rectal biopsy to make the diagnosis of HD. They subsequently developed a life-saving surgical procedure that spared patients an invariably premature death secondary to toxic megacolon and enterocolitis. This procedure involved resecting the aganglionic bowel and replacing it with normal innervated proximal intestine.3 The resulting improved patient survival and subsequent reproduction revealed a previously unsuspected familial transmission of HD.

EPIDEMIOLOGY HD is a rare disorder affecting approximately 1 in 5000 live births, showing a male : female predominance of approximately 4:1. In long-segment disease, the ratio approaches 1 : 1. The rates of distribution are equal between Caucasians and African-Americans. Most cases of HD occur in full-term infants. Less than 10% of cases occur in infants with a birthweight of less than 3 kg.

HD (non-syndromic) occurs as an isolated trait in 70% of patients. Syndromic HD occurs in 30% of cases, and 40% of these are associated with a chromosomal abnormality, representing 12% of total cases; trisomy 21 is by far the most frequent chromosomal abnormality, found in more than 90% of instances.3 Children with Down’s syndrome have an increased incidence of HD (3–10% of patients with HD) compared with the general population. In the remaining 60% of syndromic HD cases (18% of the total), there are multiple congenital anomalies or recognized genetic syndromes such as multiple endocrine neoplasia (MEN) IIA, congenital deafness, Waardenberg’s syndrome and Von Recklinghausen’s disease. Syndromic HD can be classified as a pleiotrophic syndrome with colonic aganglionosis as a mandatory feature accompanied by recognizable syndromes.3 HD is usually subdivided into short- and long-segment disease. The internal anal sphincter is the lowermost limit in both types. Some 80% of patients have short-segment HD involving the colon distal to the splenic flexure; 20% have long-segment disease involving the colon proximal to the splenic flexure. In rare cases, approximately 3–5%, there is total colonic aganglionosis, and even less common is total intestinal HD. There is also a very rare form of HD in which there is an ultra-short segment involving only the very distal 2–5cm of rectum.

GENETICS A large number of chromosomal abnormalities have been described in association with HD. The most common associated syndromic abnormality (3–10% of all ascertained cases; 90% of all chromosomal cases) is trisomy 21 (Down’s syndrome).4,5 Genetic inheritance has long been appreciated in that HD may affect more than one family member in 37% of cases, and some familial forms of HD have a 50% inheritance rate. Studies have demonstrated that the longer the segment of aganglionosis, the higher rate of familial incidence. HD is a complex multigenetic disorder in which there is significant interplay between different genes potentially resulting in multiple abnormalities. The products of different associated genes are important in the determination of the HD phenotype. Thus, there is a complex proteinomic network involved in the pathogenesis of HD. In 1967, Passarge reported 60 families with HD with autosomal recessive and autosomal dominant inheritance. It became clear that HD did not strictly follow the rules of mendelian inheritance. In syndromic forms of HD, the

736 Hirschsprung’s disease genes encoding for the proteins of the RET signalling pathway (RET, GDNF and NTN), as well as those in the endothelium (EDN) type B receptor pathway (EDNRB, EDN-3) are found in more than 50% of affected individuals (Table 48.1).4,6–12 The majority of these mutations are incompletely penetrant, so that many family members carrying them are completely asymptomatic. The interplay between the actual ligands and receptors accounting for these genetic mutations are not completely understood. Most likely, there needs to be overlapping of multiple genetic mutations, rather than a single mutation, for HD to occur.13 By the mid-1980s it was apparent that non-syndromic HD was a multifactorial disorder. Segregation studies in non-syndromic HD have shown that the recurrent risk in siblings varies from 1% to 33% depending on the sex and the length of the aganglionic segment in the affected child, as well as the sex of the sibling. The first association of a specific genetic defect in HD was reported in 1992 as a deletion in the short arm of chromosome 10.14 Further investigation revealed the location of the mutation between 10-Q 11.2 and Q-21.2. This overlapped the region of the RET proto-oncogene. Mutations of the RET gene are responsible for approximately half of familial cases, and 10% of cases of sporadic HD. In non-syndromic HD, abnormalities have been described in three loci of the RET locus, which encodes for the RET receptor. It has been postulated that different mutations in the RET proto-oncogene predispose to either HD or MENII syndrome. There is evidence that the degree of mutation in the RET proto-oncogene is associated with the severity of presentation of HD. Approximately 15% of all HD cases are accounted for by mutations in the two genes RET and EDNRB. The RET polymorphic variance may contribute to the occurrence of total intestinal aganglionosis (TIA).15 HD is one of the first polymorphic multifactorial human diseases with a defined multigenic etiology to have been identified. The authors have obtained microarray data to evaluate human colonic biopsy specimens from patients with HD and those with chronic constipation. A significant downregulation of the genes that encode molecules responsible for regulating leukocyte, epithelial, nerve and muscle cells was found in aganglionic compared with ganglionic tissue from patients with HD. In addition, a significant upregulation of genes coding for similar molecules was observed

Gene

Location

Main effect

Penetrance (%)

PMX2B RET

4p13 10q11.2

50–60 50–72

GDNF EDNRB EDN3 SOX10 NTN SIP1

5p13.1 13q22 20q13 22q13 19p13 2q22

Recessive Dominant, loss of function Dominant or recessive Recessive Recessive Dominant or recessive Unknown Sporadic

Unknown 30–85 Unknown >80 Unknown Unknown

Table 48.1 Genes associated with Hirschsprung’s disease

when aganglionic and ganglionic tissue from a patient with HD was compared with tissue from a control patient with constipation (Fig. 48.1a–c; Table 48.2). In the future, having a better understanding of the actual genetic mutations involved may lead to gene therapy for fetuses suspected of having HD based on a strong family history confirmed by the presence of one or more genetic mutations.

EMBRYOLOGY Normal ganglion cells are recognized in the esophagus at 6 weeks of gestation, in the transverse colon by 8 weeks and in the rectum by 12 weeks. The initial caudal migration of intramuscular neuroblasts is followed by intramural dispersal of neuroblasts to the superficial and deep submucosal nerve plexus. There is then concurrent and subsequent maturation of neuroblasts into ganglion cells well into infancy. Congenital intestinal aganglionosis or HD is the result of arrested fetal development of the myenteric nervous system; however, the precise pathologic mechanisms involved are not completely understood.

ETIOLOGY Classic theory regarding the embryologic development of HD is that there is failure of migration of ganglion cells along the gastrointestinal tract during the 5th through 12th weeks of embryologic development. Ganglion cells that form as the intrinsic nerves of the colon migrate caudally along the embryonic gut, originating from the vagal neural crest.16 Another theory is that there is a hostile micro-environment owing to decreased neural crest adhesion molecule (NCAM) reactivity in the aganglionic colon compared with that in normal age- and sex-matched controls. NCAM is believed to be important in neuron-site migration and localization to specific sites during embryogenesis.17,18 Although there are experimental data to support individual theories, it is likely that the cause of HD is multifactorial.

PATHOPHYSIOLOGY Aganglionosis is confined to the sigmoid colon or rectum in 75–80% of affected infants. Classically, the proximal bowel is distended with histologic evidence of muscular hypertrophy. The characteristic lesion in the distal bowel is the absence of ganglion cells in the intermuscular and submucosal plexus (Fig. 48.2). In addition, many large,

No. of genes upregulated HD aganglionic tissue vs normal tissue HD ganglionic tissue vs normal tissue HD aganglionic tissue vs HD ganglionic tissue

No. of genes downregulated

274

82

110

22

81

127

Table 48.2 Genes upregulated or downregulated in patients with HD and controls

Pathophysiology 737

Fold difference compared to control

a

20

Epithelial cells

15

Nerve cells

Leukocytes

Tissue remodeling

Figure 48.1: Microarray data on biopsy specimens from patients with HD and constipation as control. (a) Aganglionic tissue from patients with HD vs controls. (b) Ganglionic tissue from patients with HD vs controls. (c) Aganglionic and ganglionic tissue from patients with HD.

Muscle

10 5 0 −5 −10 −15 −20

Fold difference compared to control

b

20

Epithelial cells

Nerve cells

15

Leukocytes

Tissue remodeling

Muscle

10 5 0 −5 −10 −15 −20

thickened, non-myelinated nerve fibers are found within the muscularis mucosa, lamina propria, submucosa and Auerbach’s intramuscular plexus. Most of these fibers are cholinergic. Thus, an important diagnostic test involves histochemical staining for acetylcholinesterase (Fig. 48.3). HD is a form of intestinal pseudo-obstruction or functional bowel obstruction with the absence of mechanical blockage of the lumen. It is the most common form of pseudo-obstruction. Normal intestinal motility depends on a coordinated segmental contraction wave immediately preceded by smooth muscle relaxation as it propagates caudally. In HD there is a lack of a functional myenteric nervous sys-

70

67

61

Muscle

58

52 52

49

43 46

40

34 37

31

28

22 25

Leukocytes

19

Nerve cells

7 10 12 16

Epithelial cells

1 4

16 14 12 10 8 6 4 2 0 −2 −4 −6 −8 −10 −12 −14 −16

Tissue remodeling

Fold difference compared to ganglionic tissue

c

tem in the affected distal intestine, and thus ineffective distal peristalsis secondary to an inability to have smooth muscle relaxation. There are also other potential abnormalities within the more proximal transition and ganglionic bowel.19 The clinical outcome is incomplete distal bowel obstruction in neonates or chronic constipation in older children. Patients with HD do not have the normal internal sphincter relaxation that should follow rectal dilation, and thus diagnosis may be made by manometric studies. Interposed between normal ganglionic proximal bowel and the abnormal distal bowel is a transition zone characterized by hypoganglionosis and a progressive increase in

738 Hirschsprung’s disease

Serosa

Ganglionic cells in Myenteric plexus

Mucosa

Muscle layers Muscularis mucosa (no nerve fibers)

a

Muscle – circular and longitudinal

a

Myenteric plexus (no ganglion cells) Mucosa

b Figure 48.2: Hematoxylin and eosin stain of colonic biopsy showing myenteric plexus from (a) a normal subject and (b) a patient with HD (See plate section for color).

the number of thickened, non-myelinated neurons as one moves distally toward the aganglionic bowel. Correlation between the gross and microscopic anatomy is not precise, so histologic confirmation is always necessary for intraoperative decision-making. The transition zone is often obvious grossly or radiographically by a few weeks of age, as the obstruction leads to progressive proximal dilation and eventually to ‘congenital megacolon’. A normal barium enema study can never rule out the diagnosis of HD. Most evidence supports the concept that HD is a continuous disorder starting in the distal rectum and moving proximally. Although the length of involved rectal segment may be short, a correctly obtained rectal biopsy specimen showing ganglion cells precludes the existence of HD. Intestinal atresia is occasionally found in association with HD. Neural crest cells play an important role throughout the body, particularly in the gastrointestinal tract in the formation of the enteric nervous system (ENS). The complexity of the ENS rivals that of the brain, and it shares many of the neurotransmitters found in the central nervous system (CNS). The ENS also has a reflex arc that acts independently of the CNS. The ENS communicates with the CNS via the parasympathetic and sympathetic ganglia, but is capable of independently controlling the functions of

Muscularis mucosa Prominent nerve fibers

b Figure 48.3: Acetylcholinesterase staining of colonic biopsy from (a) a normal subject and (b) a patient with HD (See plate section for color).

the gastrointestinal tract. The ENS is derived from the neural crest cells that give rise to the vagal crest and subsequently the submucosal ganglia. At the completion of migration, neural crest cells differentiate into diverse cell types including neurons and glia of the sensory, sympathetic and parasympathetic ganglia, neuroendocrine cells adrenal medulla, pigmented cells and facial cartilage. Failure of the vagally derived neural crest cells to colonize the hindgut results in failure of ENS development. The earlier the migration arrest, the longer is the portion of distal aganglionic intestine. It has been demonstrated experimentally that ablation of the vagal neural crest can result in total intestinal aganglionosis. Iwashita et al.20demonstrated, by gene expression profiling combined with reversed genetic analysis of stem cell function, that HD may be caused by defects in neural crest stem cell function.

Clinical presentation 739 In summary, HD is a developmental disorder of the ENS characterized by absence of ganglion cells in the myenteric and submucosal plexuses along a variable portion of the distal intestine. The most widely accepted etiopathogenic hypothesis involves a defect of the craniocaudal migration of neuroblasts originating from the neural crest.

NEUROCRISTOPATHIES This encompasses an array of syndromes that arise from abnormalities in the development of the pluripotential neural crest cells. The diseases arising from neural crest are diverse in clinical presentation, including endocrine, cutaneous, neurologic, digestive and/or associated with syndromes. With its constellation of symptoms, in 1974, Bolande suggested the term ‘neurocristopathies’.21 The neural crest cells are important in the development of the neural and endocrine systems; thus there is a link that associates HD with abnormalities in other neural crest-derived systems. HD is classified as a simple neurocristopathy. Syndromes associated with HD include the Shah– Waardenburg syndrome, congenital central hypoventilation syndrome (CCHS), MENII and Haddad syndrome, which is short-segment HD associated with a congenital central hypoventilation syndrome. Therefore, awareness of a possible neurocristopathy associated with neurologic abnormalities should be taken into account in any patient newly diagnosed with HD. In a small study, a number of patients with HD demonstrated measurable autonomic dysfunction on pupillary and cardiovascular testing of sympathetic, parasympathetic and cardiovagal cholinergic function.22 Cheng et al.23 demonstrated moderate to severe sensory neural hearing loss, abnormal otoacoustic transmission and marked abnormalities in tests of peripheral nerve function in patients with HD compared with controls. Thus, HD may be a more generalized neuropathy than simply involving the affected bowel. There are also multiple non-neurocristopathies that are associated with HD, including the Smith–Lemli–Opitz syndrome, and distal limb anomalies that are all quite rare. Goldberg–Shprintzen syndrome, with its distinct dysmorphic facial features, microcephaly and intellectual impairment, along with agenesis of the corpus callosum and cortical malformations associated with intractable seizures, has also been associated with HD. There is a rare combination of congenital aganglionosis of the intestine and CCHS (Ondine’s curse).21,23,24 Currarino’s triad is a form of caudal regression syndrome that is a rare complex of congenital caudal anomalies that include anorectal malformations, sacral bone deformity and presacral tumor. This has been described in association with HD by Baltogiannis et al.25

INTESTINAL AGANGLIONOSIS Absence of ganglion cells in the small intestine is a rare form of HD. It is a condition found in the newborn and is associated with increased morbidity and mortality compared with the more common rectosigmoid disease. There

may be histopathologic differences between total colonic aganglionosis and rectosigmoid HD. Total colonic HD demonstrates a lack of neuronal nitric oxide synthesis and peripherin immunoreactivity. In addition, in total colonic HD there is a lack of interstitial cells of Cajal (ICCs), which act as pacemakers within the myenteric plexus, thus playing a role in bowel motility.26 Puri27 demonstrated that ICCs, which also play a role in development of the gastrointestinal tract, have an altered distribution in the entire resected bowel of patients with HD. This may suggest that the persistent dysmotility problems after pull-through operations in patients with HD may be due to altered distribution and impaired function of these ICCs.26,28 Puri also described carbon monoxide as a proposed endogenous messenger molecule for ICCs and smooth muscle cells in the gastrointestinal tract that may be altered along with heme oxygenase 2 (HO2), which is the main physiologic mechanism for generating carbon monoxide in human cells. He further demonstrated the presence of HO2 immunoreactivity in the ICCs of normal human colon and the absence of HO2 immunoreactivity in sparsely appearing ICCs in the bowel of patients with HD.27 This lack of HO2 in the ICCs may result in impaired intracellular communication between the ICCs and smooth muscle cells, causing motility dysfunction. Wedel et al.18 demonstrated structural abnormalities in the basal lamina of patients with HD. The observed ultrastructural alterations in the basal lamina of both neural and nonneural cells, as well as the increased amount of perineural and endoneural collagen, provided further evidence that the extracellular matrix components are abnormally distributed and overproduced within the bowel wall of patients affected by HD.18

CLINICAL PRESENTATION HD often presents in newborns as distal intestinal obstruction with or without sepsis. The incidence of enterocolitis is variable and always a concern. Thus, the diagnosis must be undertaken with some degree of urgency. The newborn may present as acutely ill secondary to the distal bowel obstruction. Other findings may include abdominal distention and bilious or feculent vomiting associated with failure to pass meconium. In the most severe cases, the patient may present with overwhelming sepsis and/or peritonitis secondary to intestinal perforation. At times, the delayed passage of meconium more than 48h after delivery is the mode of presentation. Between 40% and 95% of patients have been reported to have failure of passage of meconium by 48 h. However, it must be understood that the passage of meconium within 48 h does not exclude the diagnosis of HD. A high index of suspicion must be maintained for the neonate with an abnormal presentation. Age at diagnosis can vary widely, with approximately 50% of patients being diagnosed in the neonatal period and the vast majority of the remainder before the age of 2 years. Occasionally a patient will make it to later childhood or as a young adult before diagnosis. Usually they are

740 Hirschsprung’s disease suffering from severe constipation with intermittent chronic abdominal distention. A younger child may present with malnutrition and failure to thrive associated with developmental delay. Enterocolitis remains a major cause of significant morbidity and mortality. It usually manifests as explosive diarrhea, abdominal distention and fever. Diarrhea is a presenting symptom in 30–40% and is the hallmark of supervening enterocolitis. Enterocolitis may be fatal when it progresses to toxic megacolon and systemic sepsis. The rectal examination is often accompanied by a sudden explosive expulsion of meconium or stool and gas with relief of obstruction for hours to days. The treatment is aggressive hydration, parenteral antibiotics and careful bowel washout and decompression with a rectal tube. If this is ineffective, the patient may require a decompressive ostomy. Various other conditions may cause chronic constipation and intestinal obstruction in infants and children. These include inadequate dietary fluid and fiber, psychologic disorders, hypomotility caused by medications, and metabolic and endocrine conditions such as uremia and hypothyroidism. Megacystis microcolon intestinal hypoperistaltis syndrome is a rare entity that also causes intestinal obstruction. Variants of HD are also an important cause of refractory constipation. Intestinal neuronal dysplasia (IND) has been found in 25–30% of patients with HD.27 The diagnosis is based on histochemical and immunocytochemical staining. Suction rectal biopsy shows minimal or absence of submucosal ganglion cells with no or extremely low acetylcholinesterase activity in the lamina propria or muscularis mucosa.29 Hypoganglionosis is the most consistent finding in IND; other criteria include giant ectopic ganglia. Hypoganglionosis is also a rare isolated condition in which the child presents with constipation. These entities should be considered in patients with constipation who do not respond to standard surgical repair for HD. Short-segment HD is easily missed and may present with a rectal biopsy that shows ganglion cells in a child who has chronic constipation. The anorectal manometry shows no relaxation of the internal anal sphincter in response to rectal dilation. Anorectal myectomy is the preferred treatment. At the other end of the spectrum is total colonic aganglionosis, occurring in 3–10% of cases. There is no transition zone on barium enema. The diagnosis is generally made at the time of laparotomy for suspected intestinal obstruction or perforation while doing a colostomy.

DIFFERENTIAL DIAGNOSIS Differential diagnosis in the newborn period includes conditions that cause mechanical intestinal obstruction such as meconium ileus, meconium plug syndrome, small left colon syndrome, malrotation, necrotizing enterocolitis and various intestinal atresias. Patients with colonic atresia should generally be screened for HD by performing a rectal biopsy prior to reanastomosis. Functional obstructions include sepsis, hypermagnesemia and hypokalemia, to name a few.

DIAGNOSIS HD is the most common cause of lower intestinal obstruction in neonates and is a rare cause of intractable constipation in toddlers and school-aged children. When the clinical suspicion of HD has been raised, plain radiography may demonstrate signs of bowel obstruction. If there is suspicion for HD, the next appropriate study is an unprepped barium enema or anorectal manometry, potentially followed by full-thickness or suction rectal biopsy.30 The mean age at diagnosis decreased from 18 months in the 1960s to 2.6months in the 1980s as a result of physicians’ vigilance, early biopsy and anorectal manometry. However, some 8–20% of children with HD remain unrecognized after the age of 3 years. The classic triad of symptoms is delayed passage of meconium, vomiting and abdominal distention, present in 82% of cases. One or more of these symptoms is present in 98% of patients with HD. A history of delayed passage of meconium, abdominal distention, vomiting or the results of a contrast enema identify the majority of patients with HD. Physical examination reveals a distended abdomen and a contracted sphincter and rectum in most children with HD. The rectum is devoid of stool, except in the case of short-segment HD. As the finger is withdrawn on rectal examination, there is an explosive discharge of foulsmelling liquid stool with decompression of the proximal normal bowel. In older children with constipation, a careful history and thorough physical examination are often sufficient to differentiate HD from functional constipation. HD evaluation includes films of the abdomen with evidence of fecal impaction, or of distal bowel obstruction with a transition zone. In rectosigmoid HD, the location of the radiologic transition zone correlates accurately with the level of aganglionosis in 90% of cases. The funnelshaped transition zone is best demonstrated on a carefully performed, unprepped barium enema. The contrast enema demonstrates an abnormal rectosigmoid index (maximum width of the rectum compared with maximum width of the sigmoid) (Fig. 48.4). Prolonged retention of barium may be seen on delayed radiographs, together with irregular contractions in the distal aganglionic segment, a mucosal cobblestoning pattern and mucosal irregularity. The reported diagnostic accuracy of a barium enema in the first month of life varies from 20% to 95%. There have been questions regarding the accuracy of these figures due to the common absence of a transition zone. The barium enema can be diagnostic if a transition zone is demonstrated. Radiologic studies are not sensitive enough to exclude HD. Contrast enemas have been reported to be inconclusive in 10% of children with confirmed HD and in 30% of cases of HD associated with IND.31 The radiologic findings of total colon aganglionosis, hypoganglionosis and immature ganglionosis are similar in neonates. Most often these are distinguishable only after multiple biopsies and extensive histopathologic evaluation of the tissue. In addition, barium enema should not be undertaken in a patient with suspected enterocolitis as it may cause perforation. Colonic

Diagnosis 741 Figure 48.4 Contrast enema of a patient with HD. (a) Lateral view. (b) Anteroposterior view.

perforation is not uncommon in patients with HD, occurring in 3–5% of patients. Patients with total aganglionosis may present with microcolon. Swenson established the full-thickness rectal as a standard for diagnosis in 1955, reporting a 98% accuracy. Rectal biopsy is now the ‘gold standard’ for diagnosis of HD. The normal anus has a paucity or absence of ganglion cells at the level of the anal verge. To avoid missing a case of ultra-shortsegment HD, it is recommended to perform rectal biopsy at 2–3 cm above the anal verge. Histopathologic absence of ganglion cells and the presence of hypertrophied nerve fibers in the lamina propria and muscularis propria are the hallmark of the disease. The biopsy can be obtained by a suction technique at the bedside or in the office, or a full-thickness biopsy can be performed. The use of suction rectal biopsy has several advantages, including simplicity, absence of need for anesthesia, and performance at the bedside as well as in an outpatient setting with minimal complications. The most common problem is obtaining an inadequate specimen. Rarely, rectal biopsy may result in perforation or bleeding. In infants who require a laparotomy and stoma formation, serial, progressively proximal, full-thickness biopsies are obtained to determine the level at which the ganglionic bowel begins (levelling procedure). The transition zone can often be identified. If, after multiple biopsies, no clear transition zone is seen, many surgeons perform an appendectomy with frozen-section evaluation for ganglion cells. If the appendix is positive for ganglion cells, further biopsy specimens are obtained, either more proximally or more distally to establish the point of histologic transition. Laproscopically assisted full-thickness biopsy can be performed for initial diagnosis during a primary pull-through, or as repeat evaluation after definitive surgical intervention.32 There is a high rate of incorrect diagnosis of HD when a frozen-section analysis is used. Thus, frozen section is not recommended as an initial diagnostic procedure for HD.33

HD can also be diagnosed from an increased submucosal nerve plexus. The use of acetylcholinesterase, a histochemistry technique, requires only the lamina propria of the mucosa, which can further limit the difficulty of inadequate biopsy specimens, especially those obtained by the suction technique. The presence of increased acetylcholinesterase-stained nerve fibers of the lamina propria and muscularis mucosa in patients with HD is the basis of this test with the pattern of distribution of the nerve stain for acetylcholinesterase. Chemical staining for acetylcholinesterase has proved to be one of the most accurate diagnostic tools for the diagnosis of HD. The specificity of acetylcholinesterase staining is 100%, with a sensitivity of approximately 91%.34–37 The use of histochemical staining on frozen section may be a more accurate way of determining the level of ganglionic bowel during surgery, especially during the one-stage pull-through procedure. The amount of acetylcholinesterase staining in the proximal resection margins of patients with HD may have some correlation with postoperative bowel function.38 Serial biopsies proximal to the aganglionic zone may be considered for rapid acetylcholinesterase staining to ensure normal innervation and to help rule out IND.29 The diagnosis of IND, as well as other forms of dysganglionosis, should be considered when biopsies are performed to determine the level of ganglionic bowel for single-stage or one-stage pull-through. The presence of abnormalities other than HD may account for many postoperative complications of constipation and enterocolitis. The radiologic findings of total colon aganglionosis, hypoganglionosis and immature ganglionosis are similar in neonates. Most often, they are distinguishable only after multiple biopsies and extensive histopathologic evaluation of the tissue. In the myenteric plexus, the number of ganglion cells per millimeter of colon decreases. This is the most characteristic parameter for hypoganglionosis.

742 Hirschsprung’s disease Other markers such as the neuronal marker, Neu-N, also have been used to increase the accuracy of diagnosis, especially in newborns, in whom ganglion cells may be sparse and immature.39 Other antibodies that have been proposed for use in immunohistochemical staining for the diagnosis of HD include 6-antineural markers, peripherin, cathepsin, PGP9.5, synaptophysin and chromogranins 100 protein, with peripherin being the most accurate.34 Anorectal manometry is an accurate non-invasive test that can screen for the presence of HD.40 Anorectal manometry evaluates the response of the internal anal sphincter to inflation of a balloon in the rectum. When the rectal balloon is inflated, there is normally a reflex relaxation of the internal anal sphincter. In HD, this anorectal inhibitory reflex is absent. There is no relaxation, or there may be paradoxical contraction, of the internal anal sphincter. In the cooperative child, anorectal manometry represents a sensitive and specific diagnostic test for HD. It is particularly useful when the aganglionic segment is short and the results of radiologic or pathologic studies are equivocal. When sphincter relaxation is normal, HD can be reliably excluded. The accuracy of the study depends on factors such as the examination technique, the cooperation of the child during the study and the age group of the patient.41 Many investigators have used anorectal manometry in establishing the definitive diagnosis of HD. The presence of a rectal sphincteric reflex (RSR) by anorectal manometry was 100% reliable in excluding HD. This technique has the advantage of bedside performance and immediate availability of results. The study is minimally invasive and can be done in an outpatient setting. Having a negative manometry study is useful for excluding the diagnosis of HD. Anorectal manometry in the neonatal period demonstrates a sensitivity of 92%, specificity of 96%, positive predictive value of 85% and negative predictive value of 92%. In the neonate, the accuracy of manometry is questionable because of technical constraints. It has been suggested that the anorectal reflex is not completely developed in a pre-term infant or neonate younger than 12 days, so the test is unreliable when performed in these patients. It is difficult to perform anorectal manometry on a patient of less than 39 weeks’ gestation at birth or weighing less than 2.7 kg, for technical reasons. Otherwise, anorectal manometry is potentially an adequate screening test in patients suspected of HD in the neonatal period. Rectal biopsy with histopathologic examination and rectal manometry are the only tests that can reliably exclude HD. With the correct equipment and experienced personnel, there is rarely a false-negative or falsepositive result when using radiography coupled with histopathology and anal manometry. Thus, a barium enema followed by anorectal manometry and subsequently a suction or full-thickness rectal biopsy subjected to hematoxylin and eosin staining, as well as a acetylcholinesterase stain prior to proceeding with definitive surgery, appears to be a reasonable sequence of diagnostic events.

MANAGEMENT The basic principle remains the same in all approaches to management: removal of the diseased colon. Initial management includes stabilization of the patient with hydration, parenteral antibiotics, and rectal irrigations that decompress the colon and aid in evacuation of toxic waste. The safest approach in an unstable patient is to perform a leveling colostomy. The colostomy is then pulled through at the time of the definitive operation without performing a backup colostomy. This is now the most commonly practised method of surgical management. It is becoming rare that a surgeon will perform a three-stage procedure by protecting the pull-through with a transverse colostomy. The decision to perform a primary pull-through when the diagnosis has been established depends on the condition of the child and the response to initial treatment. Preoperative preparation includes the need for saline rectal washouts to keep the colon decompressed. The use of intermittent or continuous rectal irrigation aids in preparing the bowel for a pull-through procedure. Repeat rectal irrigations may be used to stimulate bowel movement during the preoperative period, which can be anywhere from 1 to 8weeks after birth. The tolerance of rectal irrigations can be used to indicate which patients will best tolerate a one-stage pullthrough. Patients that do well functionally with this regimen are discharged home and return for surgery at 2–8 weeks of age for an elective, laparoscopically assisted, endorectal pull-through procedure. Infants who do not improve functionally with rectal irrigations are treated by means of a colostomy and subsequent definitive endorectal pull-through. After removal of the diseased colon, the surgical options include four basic procedures that bring normal innervated colon down to the anal canal, with sparing of the external sphincters. The choice of the procedure is surgeon preference: all procedures have a similare incidence of complications and long-term results.

Swenson technique Swenson and Bill performed the first resection of an aganglionic segment in 1948. The Swenson procedure removes the non-functioning spasmodic segment, leaving the pelvic nerves and anal sphincter intact by not performing an extensive pelvic dissection. The subsequent colorectal anastomosis is performed 3–5cm above the dentate line.

Modified Duhamel procedure Duhamel introduced the retrorectal pull-through technique in 1956. In this procedure, the pelvic dissection is limited to the retrorectal space where the dissection is carried down to the pectinate line remaining behind the rectum, avoiding potential injury to the pelvic nerves. Thus, this is a retrorectal transanal pull-through in which the aganglionic rectum is bypassed. A neorectum is formed consisting of anterior aganglionic rectum sutured to ganglionic bowel that is tunneled posterior to the residual

Management 743 aganglionic rectum. In the most modern version of this procedure, the septum between the original aganglionic rectum and the posterior pulled-through colon is divided to make a common channel, resulting in a pouch or neorectum. To minimize pelvic dissection, however, a relatively long rectal stump is left predisposing to stool retention, in part due to the retained septum superiorly between the aganglionic bowel anterior and the pulledthrough ganglionic bowel posterior. The later Martin modification attempts to deal with this in part by opening the retained septum in the most superior aspect of the pouch or neorectum, thus avoiding retention of stool.

Soave–Bolle procedure The Soave or endorectal pull-through procedure was introduced by Soave in 1960. This procedure consists of removing the mucosa and submucosa of the rectum, and pulling ganglionic bowel through a short aganglionic muscular cuff. There is no intrapelvic dissection as the pulled-through colon is brought down through intact rectal walls that have been denuded of mucosa, leaving no possibility of damaging the pelvic autonomic nerve system. By remaining within the muscular cuff of the aganglionic segment, important sensory fibers and the integrity of the internal sphincter are preserved. Although leaving behind aganglionic muscle surrounding normal bowel conceptually might lead to a high incidence of constipation, this has not been the experience clinically. The muscular cuff is incised posteriorly to prevent a constricting effect after surgery. Initially the anal anastomosis was not performed at the time of pullthrough. Bolle modified this procedure by performing anastomosis at the anus at the time of the pull-through. This procedure is now performed commonly as a primary pullthrough in neonates, without the need for an initial leveling colostomy. The endorectal pull-through can be done as a transabdominal approach with a Duhamel, Soave or Swenson procedure. A laparoscopically assisted approach can also be used for the Duhamel and Soave procedures.42,43

Single-stage procedure The previously described procedures were performed as a two- or three-stage process in which a leveling colostomy was performed initially. This is followed by the pullthrough with a potential protecting colostomy that would then have to be taken down as the third procedure prior to having normal passage of stool per anus. Most surgeons have stopped performing a protective colostomy after the pull-through, thus eliminating the need for a third procedure. In many centers, these operations have all been replaced by the performance of a one-stage pullthrough.44–48 Either a Swenson or a Soave procedure is performed in most cases. The primary neonatal pull-through depends on complete preoperative decompression of the rectum. The procedure can be performed with laparoscopic assistance or as a perineal dissection only. A disadvantage of the perineal-alone procedure is that it may be difficult to perform for long-segment disease.

In 1999, it became popular to perform the Soave endorectal pull-through without a colostomy as a singlestage procedure earlier in the child’s life, and this operation is now being performed in the neonatal period. The singlestage transanal Soave pull-through procedure can be performed successfully in infants. The transanal one-stage endorectal pull-through is a modification of the Soave procedure.44–46,48 It has been demonstrated to have comparable outcomes to the transabdominal approach, without compromise to sphincteric integrity.44,49 Complication rates are 6% for enterocolitis and 4% for stricture, comparable to those of a multiple-stage pull-through procedure.44 Both the Soave and Duhamel procedures are performed as a single-stage procedure with minimal complications and a decreased hospital stay, and demonstrate good functional results in comparisons to delayed one- or two-stage procedures, avoiding a stoma. Performing a primary pull-through in the neonatal period is not associated with increased episodes of enterocolitis compared with the multiple-stage pull-through procedure. The early single-stage procedure has the potential advantages of lower cost, less risk of damage to pelvic structures, absence of abdominal incision, lower incidence of intraperitoneal bleeding and adhesion formation, and toilet training may be facilitated if primary endorectal pull-through is performed early in infancy.50 To perform a single-stage procedure safely, one must have the availability of a pediatric or gastrointestinal pathologist experienced in HD and comfortable with analyzing frozensection specimens as the surgeon seeks out the transition zone intraoperatively. The diagnosis should be established by permanent section of a rectal biopsy specimen before starting the pull-through procedure. Many authors have advocated the single-stage pullthrough as an adequate and safe treatment of HD that has excellent early results with a shorter length of hospital stay than the open procedure.48,50–54 The long-term complication rate and functional results have been comparable to those of open multiple-stage approaches. Georgenson has advocated not only the use of a laparoscopically assisted one-stage pull-through procedure but also that the transition zone be determined by laparoscopically obtained biopsies prior to mobilization of the colon.54a The anal anastomosis can be either hand-sewn or stapled. Laparoscopically assisted pull-through can also be performed as a staged procedure in patients who have received a diverting colostomy for enterocolitis. It is the present authors’ preference to perform a onestage pull-through within the first several weeks of life, depending on the patient’s response to intestinal decompression. If the infant does not respond to rectal irrigations, a leveling colostomy is performed prior to discharge from the neonatal nursery. If the infant responds to rectal irrigations, a primary pull-through is performed at any point during the first several weeks of life. Patients have been discharged successfully with the parents performing rectal irrigations and patients feeding nicely with adequate weight gain. The use of laparoscopy has allowed an intraoperative decision to be made regarding which type of pull-through procedure is to be performed in the event

744 Hirschsprung’s disease that the patient has total colonic HD. It is the authors’ belief that patients with long-segment disease are better served in the short term with a Duhamel-type procedure to help decrease the initial frequency of bowel movements. Although long-term results with regard to stool frequency are comparable between the different types of pull-through procedure, the initial 6–18 months involve difficult perineal care and constant soiling and irritation to the patient. This is lessened with the modified Martin–Duhamel procedure vs the Soave endorectal pull-through. The primary endorectal pull-through is generally reserved for stable infants. The proximal colonic dilation is a relative or absolute contraindication to a primary anastomosis. In addition to a markedly dilated colon, several other factors are contraindications to a primary pullthrough, including preoperative enterocolitis, total colonic aganglionosis, sepsis, marked malnutrition, hemodynamic instability and coexisting extracolonic disease states such as congenital heart disease. These patients are better served by a diverting colostomy and a deferred staged repair. There has been a dramatic reduction in the mortality rate of HD over the past several decades due to improvements in patient diagnosis, newborn intensive care, surgical technique, expertise and treatment of HD-associated enterocolitis. Patients with primary endorectal pull-through may have a slightly higher risk for developing enterocolitis. Despite the surgical advances in the treatment of HD, a two-stage surgical repair involving a temporary diverting colostomy is still necessary in up to one-third of patients, especially those who do not tolerate preoperative decompression and washout. Thus, two- or three-stage surgery is generally reserved for sicker infants with long-segment or total colonic aganglionosis. The accumulated data indicate that primary endorectal pull-through procedures have a similar longterm complication rate to staged repairs. The most crucial fact remains that the most suitable operation depends on the individual patient. Primary endorectal pull-through can be performed in up to two-thirds of patients with HD.

LONG-SEGMENT DISEASE Radiographic studies are diagnostic in only 20–30% of patients with total colonic aganglionosis. The male to female ratio is also decreased to almost equal proportion. Many infants with total colonic HD require parenteral nutrition, so that catheter sepsis along with failure to thrive, stoma dysfunction, and electrolyte imbalance and dehydration are commonly encountered complications. The mortality rate in this group of infants is also generally higher, probably related to the increased incidence of enterocolitis at the time of diagnosis. The mortality rate is as high as 40% in patients with this severe variant of HD. Delay in diagnosis is more common in long-segment disease or total colonic aganglionosis, and leads to an increased incidence of enterocolitis and a resultant increased mortality rate. Total colonic aganglionosis can be managed by colectomy with ileoanal pull-through or the Martin–Duhamel procedure.

The incidence of total colonic aganglionosis with ileal involvement is estimated as 1 in 50 000 live births. This disorder has a variable prognosis.55,56 The major prognostic factor is the length of the small bowel involved in association with total colonic aganglionosis. Those with ileal involvement greater than 500 cm most often require long-term nutritional assistance. The management of near-total or total intestinal aganglionosis requires conservative resection of the intestine and a diverting ostomy.55,57 One should resist massive bowel resections in total intestinal aganglionosis. Conservative management with total parenteral nutrition, antikinetic agents and limited feeds to prevent the development of end-stage liver disease may be associated with the best long-term outcome.

ULTRA-SHORT-SEGMENT HD The major problem with ultra-short-segment HD is the fact that the ‘gold standard’ for making the diagnosis of HD – the rectal biopsy – may show ganglion cells. In general, ultra-short-segment HD consists of a 2–4-cm segment of distal aganglionic bowel. Thus, the diseased segment may be missed on rectal biopsy when the biopsy is obtained proximal to the short affected area of aganglionosis. In addition, the contrast enema may not show a transition zone. These factors may all lead to a delay in diagnosis. Anal manometry may be the most sensitive diagnostic modality. It will demonstrate an absence of anorectal reflex relaxation. The preferred treatment for a patient with definitive ultra-short-segment HD is anorectal myectomy, provided that ganglion cells have been confirmed from a previous biopsy specimen at 4 cm or more above the dentate line.

OUTCOMES Delayed diagnosis places a child at increased risk of developing complications of the disease, including enterocolitis and perforation of the intestine. In more recent reviews, more than 45% of all patients with HD were diagnosed in the neonatal period. The trend is evident in the striking decline in mortality associated with the disease. In 1954, Klein and Scarborough58 reported a 70% mortality rate. In 1966, Rehbein et al.59,60 reported a 28% mortality rate, and in 1966 Shim and Swenson61 reported a mortality rate of 33%. Although the treatment of HD is to ensure that the patient survives and does not succumb to the complications of enterocolitis, it also is to achieve normal bowel function and overall good quality of life if possible.62,63 The hallmark of success of any pull-through procedure is the development of a normal bowel habit. The outcome of patients with HD can be highly variable. Thus, treatment of the patient does not end with surgery. The bowel function and quality of life of patients is poorer than that of healthy children. Fecal soiling is common and affects the patient’s socialization and self-esteem. As the patient matures, attempts should be made to minimize the number of bowel movements to aid

Outcomes 745 in improving the overall quality of life. Despite corrective surgery, defecation difficulties may occur for long periods in children with HD, often requiring medical therapy. Approximately 15–20% have a satisfactory functional outcome following operative repair that persists into young adulthood. Soiling and increased stool frequency persist and cause significant postoperative morbidity in 10–30% of patients. In the long term, this problem improves with age, provided the child is not intellectually impaired and had no major complications or recurrent enterocolitis. Regular long-term follow-up is required, implementing strategies, both behavioral and medical, as needed to aid in resolving this problem. Although soiling may have a significant social impact in the early years after surgery, most parents are satisfied with their child’s outcome and adapt to the functional abnormalities that they encounter. Constipation is the most common complaint after a pull-through, occurring in up to 85% of patients less than 5 years after surgery but tending to improve with age. Most children show significant improvement with respect to fecal incontinence, but this may not happen until adolescence. After corrective surgery, 50–70% of children remain constipated. As many as 30% have continued fecal soiling and one-quarter have recurrent enterocolitis.49 The evaluation of either persistent constipation or fecal incontinence in the post-repair patient should consist of routine physical examination, contrast radiography, colonic biopsy, and rectal and colonic manometry. Although the majority of patients with fecal incontinence or constipation after the pull-through procedure improve over time, most may benefit from minimally invasive evaluation of anorectal function. Detailed information about sphincteric function and colonic motility may aid in devising a medical intervention for the patient’s symptoms prior to embarking upon surgical intervention. Zaslavsky and Loening-Baucke64 demonstrated that as long as 4 years after surgery patients continued to have absence of the reflux sphincter relaxation regardless of the type of operation performed. Among the various complications such as wound infections, dehiscence, anastomotic leak, postoperative enterocolitis, bowel obstruction, intra-abdominal abscess, mucosal prolapse, anastomotic stricture and fistulae, only anastomotic stricture was significantly more common in patients who had undergone the Swenson procedure compared with those having the Duhamel. When urinary incontinence, total episodes of enterocolitis, soiling and constipation were considered, there was no significant difference between these two groups. The incidence of recurrent symptoms is 10–20% for all the procedures. The cause may be an inadequate pullthrough secondary to absence of ganglionic cells in the bowel that has been advanced.65 Ischemia-induced aganglionosis secondary to the pull-through can result in constipation. In up to one-third of patients who have had a transitional zone pull-through there may be intractable postoperative symptoms that may require repeat surgery.66 Enterocolitis and intractable constipation were found to be significantly higher in patients who had transitional zone pull-through procedures.

Enterocolitis remains a major cause of morbidity and mortality in 10–40% of patients, most commonly presenting following pull-through. The development of strictures or retained aganglionic segments is a significant risk factor for the development of postoperative enterocolitis. The incidence of HD-associated enterocolitis is inversely proportional to the age and weight of the patient. In patients with HD that is sufficiently mild for survival with no difficulties until the age of 15 months, or a weight of more than 10 kg at diagnosis, the risk of postoperative enterocolitis is lower. HD-associated enterocolitis can occur as early as the first month after surgery, or as late as 1–2 years postoperation. Recurrent episodes of enterocolitis are common and usually improve over time following pull-through. Enterocolitis requires hospitalization in 10–20% of cases, usually in the first few months after definitive surgery, and decreasing significantly thereafter. A higher incidence is seen in patients with total colonic aganglionosis. The diagnosis of enterocolitis is made on the basis of a clinical history of explosive diarrhea and distention, vomiting, fever, often lethargy and sepsis. Along with the history and physical examination, radiographic findings may demonstrate an intestinal cut-off sign. There is an acute inflammatory infiltrate into the crypts and mucosa of the colonic or small intestinal epithelium. If the process is left to proceed without treatment, perforation of the intestine may occur. The pathophysiology of enterocolitis is not completely understood, although contributing factors such as intestinal stasis with bacterial invasion of the lumen wall and translocation, decrease in intestinal defense mechanisms and abnormal mucins all contribute to its onset.67 Approximately one in four infants with HD will develop colorectal mucosal inflammation of variable clinical severity. Patients with trisomy 21 are known to have an increased risk of developing enterocolitis. Preoperative HD-associated enterocolitis was an important factor in relation to functional outcome after endorectal pullthrough.68 It is unclear whether this is related to variations in patients with HD, as this may predispose to the preoperative enterocolitis and overall poor long-term outcome. The treatment for HD-associated enterocolitis begins with a series of aggressive washouts using a largecaliber rectal tube to decompress the colon above the anal sphincter. Intravenous antibiotics including metronidazole should be used. Intractable constipation and recurrent enterocolitis may lead to the need for further surgical intervention. Patients who develop symptoms such as failure to thrive, intractable abdominal distention or multiple episodes of enterocolitis deserve further investigation to determine the cause of their recurrent symptoms. Contrast enemas are quite helpful in demonstrating the presence or absence of a strictured segment. Rectal strictures occur due to inadequate anastomosis and postoperative leak. Anal manometry can be quite useful.69 Simple strictures may be amenable to serial dilations. More persistent strictures, which may be secondary to a previous history of anastomotic leak, may require more extensive intervention such as resection.

746 Hirschsprung’s disease Calibration and subsequent dilation starting in the early postoperative period will usually prevent these complications. If the patient is having difficulties and there is no stricture present, repeat biopsy is warranted to rule out a retained segment of aganglionic bowel. Other diagnoses such as neuronal dysplasia or hypoganglionosis should also be ruled out. Myectomy may be useful in patients who have persistent enterocolitis or constipation with failed medical treatment, and who have been shown by biopsy not to have an aganglionic segment. In addition, myectomy may be helpful in the patient who has been demonstrated to have a retained length of aganglionic bowel of less than 5 cm. Its success has been attributed to the use of a lateral sphincter myotomy including the external sphincter in patients with severe outlet obstruction and constipation.70 This has resulted in significant symptomatic relief in two-thirds of patients. The use of botulism toxin (botox) injections into the internal anal sphincter in patients with severe constipation or recurrent enterocolitis has demonstrated good results. Patients with a good response are those who may benefit most from a myectomy. There may also be lasting effects of the botox injection, so that the patient may not need any further intervention. Indications for repeat pull-through may be retained aganglionosis, severe stricturing, dysfunctional bowel or neuronal dysplasia, severe enterocolitis, anastomotic stricture, leaking anastomosis and persistent rectal septum.66,71 Additionally, there are patients with marked dilation of the rectosigmoid secondary to years of constipation and loss of muscular tone of the bowel. In patients who have had an endorectal pull-through, either transabdominal or laparoscopic, an attempt at a repeat endorectal pull-through may be possible. If not, a decision should be made whether to perform a Duhamel- or Swenson-type procedure. Patients with a failed pull-through procedure may do best with a Duhamel pull-through performed as a secondary procedure, owing to its lower risk for injury to pelvic structures and preservation of a previously dissected sphincter complex. Patients who have a Swenson or Duhamel procedure will require a transabdominal repeat of either of those procedures. An endorectal pull-through gives similar results to Duhamel and Swenson procedures for repeat pull-through operations, as long as there is an adequate rectal cuff for repeat anastomosis.72 The posterior sagittal approach is a useful alternative in difficult repeat pull-through surgery with maintenance of continence and minimal complications.73

gastrointestinal motor dysfunction in the majority of children with HD long after surgical treatment of the aganglionic segment. The objective abnormalities include abnormal colonic transit, delayed total gut transit and previously unrecognized delays in gastric emptying. Transit abnormalities are also found in more than half of asymptomatic children, suggesting that additional factors are required to induce the symptomatic state. Thus, those caring for patients with HD must be aware that the manifestations of the disease are not localized only to the aganglionic colonic segment, and that once the disease has been treated surgically there may be postoperative symptoms. Intestinal neuronal dysplasia (IND) associated with HD may also result in persistence of symptoms. IND was initially described by Meier-Ruge in 1971 and was classified as a colonic dysplasia. IND has a varied histologic appearance with hyperplasia of the enteric ganglia; increased acetylcholinesterase staining is characteristic. The typical presentation of IND is variable. Most children complain of abdominal distention; some have constipation and develop enterocolitis. The extent of IND may range from a short colonic segment to the entire length of the gastrointestinal tract. In contrast to HD, the internal sphincteric relaxation reflex is absent or atypical in only 75% of patients. HD-associated IND was found in 40% of cases.27,57 There are two types of IND: A and B. Type B is seen much more commonly, yet type A presents at a younger age. Initial symptoms are related to the length of the aganglionic segment, but not to the presence of HD-associated IND. After surgery, the presence of long-segment aganglionosis or associated IND implies a delay in the restoration of normal defecation.76 Persistent constipation is found in 40% of patients with associated disseminated IND at 6-month follow-up, compared with 20% in patients with isolated HD. These children need secondary intervention more often than those with associated localized IND or isolated HD. Thus, HD-associated IND has clinical implications for the postoperative period if IND is disseminated. Intraoperative histochemical examination could be of importance in looking for dysganglionic and hypoganglionic segments that may be responsible for postoperative bowel dysfunction.

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Serosa Muscle – circular and longitudinal

Ganglionic cells in Myenteric plexus

Muscle layers

a

Myenteric plexus (no ganglion cells)

b

Figure 48.2: Hematoxylin and eosin stain of colonic biopsy showing myenteric plexus from (a) a normal subject and (b) a patient with HD.

Mucosa

Mucosa

Muscularis mucosa (no nerve fibers) Muscularis mucosa Prominent nerve fibers

a

b

Figure 48.3: Acetylcholinesterase staining of colonic biopsy from (a) a normal subject and (b) a patient with HD.