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Acute Appendicitis
ACUTE ABDOMEN
tends to be restricted to ‘developed regions’ of the world and is relatively uncommon in ‘developing regions’. It has been suggested that the harder, firmer stools produced as a result of a low-fibre diet make appendicular obstruction secondary to an impacted faecolith more likely. The alteration in intestinal flora secondary to an increase in transit time has also been implicated in the pathogenesis.
Acute Appendicitis John Simpson JH Scholefield
Familial: there is weak evidence of a familial tendency to develop appendicitis. Although the exact cause is unknown, hereditary anatomical anomalies, shared dietary habits and familial resistance to intestinal flora have all been suggested. Social factors such as domestic overcrowding and poor hygiene, which can lead to an increase in respiratory and enteric infections, have also been linked to the pathogenesis.
Acute appendicitis is the most common abdominal emergency and accounts for over 60,000 hospital admissions annually in England and Wales. The incidence of appendicitis is 1.5/1000 and 1.9/1000 in males and females, respectively, and the overall lifetime risk is estimated to be 6–20%. Appendicitis is uncommon before 2 years of age, and the incidence peaks in the second and third decades, but no age group is exempt.
Pathology Inflammation of the appendix ranges from minor simple acute inflammation with spontaneous resolution to suppurative necrosis and perforation. Luminal bacteria are thought to initiate infection and bacteriological cultures from inflamed appendices usually reveal a mixed growth, commonly of Escherichia coli, Klebsiella spp., Proteus spp. and bacteroides. Organisms enter the wall at the site of an ulcer, which has usually been caused by an impacted faecolith. If the inflammatory process progresses, the wall of the appendix becomes oedematous, and purulent inflammation leads to thrombosis and gangrene. The greater omentum and small intestine can adhere to the inflamed appendix and localize the sepsis forming a phlegmatous mass or abscess. However, if perforation occurs early in the inflammatory process, generalized peritonitis results. Perforation rates are between 10–33% at the time of operation in the general population, but these figures rise at the extremes of age.
Aetiology The vermiform appendix is a vestigial structure, which is 7.5–10 cm long in an adult. Morphologically, it represents the underdeveloped distal part of the large caecum that is present in many animals. The exact cause of acute appendicitis remains unclear, but several factors have been implicated and, in some cases, the aetiology may be multifactorial. Luminal obstruction: in any blind-ending structure, luminal obstruction, which prevents the escape of secretions, inevitably leads to a rise in intraluminal pressure. This increased pressure can lead to mucosal ischaemia and the stasis provides an ideal environment for bacterial overgrowth. This sequence of events may provide a plausible explanation in many cases, as some form of obstruction can be demonstrated in over half of the appendices removed for acute appendicitis. Luminal obstruction most commonly results from an impacted faecolith, but other causes include lymphoid hyperplasia, worms (most commonly roundworms or threadworms), strictures, foreign bodies, carcinoid tumour, caecal cancer and ileocaecal Crohn’s disease.
Clinical features The history and examination can vary widely and only around 50% of patients with acute appendicitis have a classical presentation (Figure 1). The age of the patient can influence the presentation and, as the appendix is a relatively mobile structure, the clinical picture is also dictated to a large degree by its anatomical position. Furthermore, if the early stages of the disease are silent, patients may present acutely unwell with generalized peritonitis.
Diet: epidemiological studies show that the geographical incidence of acute appendicitis correlates closely with the consumption of a low-residue diet. As such, appendicitis
History: the primary feature of appendicitis is abdominal pain. Initially, because of the visceral innervation of the midgut, referred pain is commonly felt in the central abdomen. If appendicular obstruction or distension is present, this is generally colicky, but otherwise the pain tends to be more constant. As the inflammatory process continues and involves the parietal peritoneum, the pain intensifies and localizes towards the right iliac fossa. This usually occurs within 24 hours by which time patients describe the pain as sharp, and aggravated by movement and coughing. Following the onset of pain, loss of appetite and constipation are common. Patients tend to be nauseated and may have vomited, though this symptom does not usually persist.
John Simpson is an MRC Clinical Training Fellow in the Department of Surgery, University Hospital Nottingham, Nottingham, UK. He qualified from the University of Leeds, UK and trained in Nottingham, UK. His current research interests include diverticular disease and postinflammatory remodelling of the enteric nervous system. J H Scholefield is Professor of Surgery at the University Hospital Nottingham, UK. He qualified from the University of Liverpool, UK, and trained in Sheffield and London, UK. His current research interests include early the diagnosis of colorectal cancer, inflammatory bowel disease and anal fissure.
SURGERY
153
© 2002 The Medicine Publishing Company Ltd
ACUTE ABDOMEN
Anatomical location of the appendix
Clinical history and signs in patients with acute appendicitis
History
Examination
Feature Reliable Less reliable • Duration 24–36 hours • Vomiting • Initial central location • Diarrhoea/ of pain and migration constipation to right iliac fossa • Anorexia • Tachycardia • Mild pyrexia • Guarding in right iliac fossa • Percussion tenderness in right iliac fossa
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• Flushed • Fetor oris • Tenderness on rectal/ vaginal examination • Rovsing’s sign • Psoas stretch sign • Obturator test
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2
Investigations • Moderate leucocytosis with neutrophilia 1
Anatomical positions of the appendix and their approximate incidence
Examination: the patient is usually flushed with a dry tongue. An associated fetor oris is often present. Patients are usually mildly pyrexial (up to 38 °C) and have a slight tachycardia. Following localization of the pain in the right iliac fossa, there is muscular rigidity and percussion tenderness. Demonstrating rebound tenderness is not advised as it is unlikely to add anything to the examination findings at this stage and, more importantly, can be extremely uncomfortable for the patient. In cases of early appendicitis, pain can often be localized to the right iliac fossa by asking the patient to hop or to cough. The site of maximal tenderness is classically described as McBurney’s point (Figure 2) which marks the base of the appendix and lies two-thirds of the way along a line drawn from the umbilicus to the anterior superior iliac spine. Palpation of the left iliac fossa may cause pain in the right iliac fossa (Rovsing’s sign). Rectal and vaginal examination can be normal, though localized tenderness may be detected on the right side, especially if the appendix lies within the pelvis.
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3
Features influencing presentation Anatomical features (Figure 3) Retrocaecal appendix – in this position, an inflamed appendix can be protected from the anterior abdominal wall by a caecum distended with gas. Muscular rigidity is often absent and tenderness to deep palpation is lacking. There may, however, be tenderness in the right loin. The patient may hold their right hip in a slightly flexed position due to psoas spasm, as the inflamed appendix lies in contact with that muscle. In this situation, passive extension or hyperextension of the right hip may increase the abdominal pain (psoas stretch sign). Post-ileal – an inflamed appendix lying behind the terminal ileum may be difficult to diagnose for several reasons. The symptoms may be vague and, because the inflamed appendix
SURGERY
���������
lies relatively protected from the anterior abdominal wall, the pain is poorly localized. Vomiting can be more persistent and, as the appendix irritates the distal ileum, diarrhoea is more common. Pelvic – if the appendix lies in contact with the rectum, diarrhoea can be a prominent feature. Similarly, contact with the bladder may lead to frequency of micturition and microscopic haematuria. Tenderness may be lacking over McBurney’s point, though rectal or vaginal examination may localize tenderness in the rectovesical pouch or the pouch of Douglas. Psoas spasm may be present and, when the appendix lies in contact with the obturator internus, passive internal rotation of the hip may aggravate the pain (obturator sign).
154
© 2002 The Medicine Publishing Company Ltd
ACUTE ABDOMEN
Age-related features Young children – acute appendicitis in young children often has a nonspecific presentation and difficulty in differentiating it from mesenteric adenitis or enteritis can result in a delay in diagnosis. This delay, together with the underdeveloped greater omentum in young children which can often fail to localize any developing sepsis, results in much higher rates of peritonitis, perforation and abscess formation, and up to 75% of young children present in this way. Elderly – symptoms are often less pronounced in the elderly, and patients may be afebrile with a normal white cell count. In addition, a diagnosis of acute appendicitis is often not considered in this age group and may be missed, resulting in a delay in treatment and higher rates of perforation (around 50%). These factors and a diminished physiological reserve contribute to the increased mortality in this age group. Pregnancy – appendicitis occurs in 1/1500–2000 pregnancies and is the most common non-obstetric indication for laparotomy during gestation. Displacement of the appendix by the uterus during the latter stages of pregnancy can result in an atypical presentation and symptoms may be confused with the onset of labour. In contrast to the classical presentation, nausea and vomiting are usually more common and, due to the upward displacement of the appendix, tenderness can be present anywhere along the right side of the abdomen. However, as the gravid uterus can protect the inflamed appendix from the anterior abdominal wall, tenderness may not be marked. Ultrasound is a useful diagnostic aid to distinguish appendicitis from obstetric pathology. Simple acute appendicitis has negligible maternal mortality, but the risk of fetal death is around 10%. Perforation, however, significantly increases the risks to both mother and fetus, and the mortality rates rise to 2% and 30%, respectively.
Most of the changes seen in some cases of acute appendicitis, such as haziness in the right iliac fossa and dilated loops of ileum, are nonspecific. However, abdominal radiographs can occasionally demonstrate an appendicular faecolith and, as up to 50% of children under 2 years old have been reported to have a visible faecolith, a plain abdominal film may be a useful in this age group. Cross reference SURGERY 2001; 19(10): 241. Ultrasonography: high resolution ultrasonography has been shown to have high sensitivity and specificity in the diagnosis of acute appendicitis. Although not advocated as a routine diagnostic test, its value lies in its ability to obtain a diagnosis in patients with an atypical history and to exclude other pathology, particularly of the female pelvis. Laparoscopy: this allows good visualization of the abdominal and pelvic organs, and is helpful in patients with an atypical presentation, especially young women. Computer-aided diagnosis: the role of computer-aided diagnosis in the management of appendicitis is still debated. Although some trials have shown it to reduce negative laparotomy rates, the incidence of perforation and mortality, others have shown clinical judgement to be just as effective.
Differential diagnosis The variability in presentation in all age groups results in a wide range of possibilities in the differential diagnosis of suspected acute appendicitis (Figure 4).
Treatment The treatment of choice for acute appendicitis is appendicectomy. The operative mortality for early operation is less than 0.2%, but this rises to around 5% in the very young and elderly patients if perforation has occurred. In all cases, patients require adequate fluid resuscitation preoperatively. This is particularly important in patients presenting late with generalized peritonitis, who may be severely dehydrated. If an appendicular mass can be felt preoperatively in an otherwise fit patient, operation may be delayed.
Investigations Although further investigations are not required in many cases of acute appendicitis (because the presentation can be variable) they are often necessary to exclude other causes of the symptoms. Haematological: although there is no single investigation which will accurately diagnose appendicitis, approximately 90% of patients have a moderate leucocytosis (about 15,000 cells/µl), predominantly neutrophils (> 75%).
Appendicectomy Classically, the appendix is approached through a musclesplitting gridiron incision (Figure 5). This is made through McBurney’s point perpendicular to a line drawn from the umbilicus to the anterior superior iliac spine. A Lanz incision, which is placed almost horizontally low in the right iliac fossa, is also commonly used (Figure 5). The muscular layers of the anterior abdominal wall are split in the line of their fibres, and the peritoneum is exposed and opened. The caecum is identified and gently eased forward using a finger. The appendix is normally found in the retrocaecal fossa and can be delivered through the wound in a similar manner with a finger hooked behind it. If there is difficulty in delivering the appendix, the abdominal wound should be extended to afford better access. Mobilization of the caecum by dividing the peritoneal reflection along its lateral border may also be required if the appendix lies in a
Urinalysis: this is usually normal, though leucocytes or red blood cells may be present in the urine of patients with retrocaecal or pelvic appendicitis, caused by irritation of the bladder or ureter by the adjacent inflammation. Urine microscopy and culture will identify a urinary tract infection if clinical signs are equivocal. Pregnancy testing: this is vital in all women of reproductive age. Imaging Plain radiographs: these are largely unhelpful in diagnosis, but are important to exclude other causes of abdominal pain.
SURGERY
155
© 2002 The Medicine Publishing Company Ltd
ACUTE ABDOMEN
Lanz and gridiron incisions for appendicectomy
Differential diagnosis of appendicitis Thorax and respiratory tract • Tonsillitis • Pneumonia Abdomen • Acute cholecystitis • Perforated peptic ulcer • Gastroenteritis • Mesenteric adenitis • Terminal ileitis • Meckel’s diverticulitis • Colonic diverticulitis/appendicular diverticulitis • Intestinal obstruction • Intussusception
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Pelvis • Ectopic pregnancy • Ruptured ovarian follicle (mittelschmerz) • Torted ovarian cyst • Salpingitis/pelvic inflammatory disease
5
5 days. Following discharge, patients should be advised to avoid physical exertion for 2–3 weeks and then to reintroduce activities gradually.
Urinary system • Right pyelonephritis • Right ureteric colic Other • Diabetic abdomen • Porphyria • Rectus sheath haematoma • Pancreatitis • Pre-herpetic pain (right lower dorsal spinal roots)
Postoperative complications Wound infection: this is the most common complication and rates vary according to the degree of operative contamination. In low-risk cases with simple acute appendicitis, the infection rate is less than 5%. If, however, the appendix is gangrenous or perforation has occurred, this can rise to around 20%. These rates can be reduced with the use of perioperative antibiotics and intraoperative peritoneal lavage. Delayed primary closure is now seldom used, but may be reserved for severely contaminated wounds.
4
high retrocaecal position. Once delivered, the appendicular mesentery is divided and the vessels ligated. The base is crushed, ligated and the inflamed appendix is removed. Whether the appendicular stump is inverted or left following ligation probably makes no difference. If free peritoneal fluid is present, lavage with warmed saline is usually performed and the wound is then closed in layers. A peritoneal drain is seldom necessary, though a corrugated or tube drain can be used if there is considerable purulent fluid in the retrocaecal space or pelvis. Perioperative broad-spectrum antibiotics (e.g. one to three doses of cefuroxime, 750 mg i.v., and metronidazole, 500 mg i.v.) should be used in all appendicectomies, as they reduce postoperative intra-abdominal abscess formation and wound infection. In early appendicitis, it is possible to remove the appendix laparoscopically. Studies have shown that postoperative pain, wound complications and length of hospital stay all tend to be lower with this technique, but the operative time is increased. Postoperatively, patients are permitted to take fluid orally and diet is normally reintroduced within 24–48 hours. In cases of perforated appendices with advanced sepsis and generalized peritonitis, intravenous antibiotics should be continued for
SURGERY
Intra-abdominal abscess: gross peritoneal contamination can lead to postoperative intra-abdominal abscess formation. The common sites are subphrenic and pelvic. Patients present with rigors and have a swinging pyrexia. Ultrasound examination is useful in diagnosis and the treatment of choice is drainage under ultrasound or computed tomography (CT) guidance. Faecal fistula: this is a relatively rare complication and occurs from the appendix stump. It can result from an insecure ligature or caecal ischaemia. Most fistulas settle with conservative management.
Appendicular mass If there is a delay in presentation, a tender mass can often be felt in the right iliac fossa. There is overlying muscular rigidity, but otherwise the abdomen is soft and non-tender. The mass consists of an inflamed or perforated appendix surrounded by greater omentum, caecum and adherent loops of small intestine. Conservative treatment is indicated for patients with
156
© 2002 The Medicine Publishing Company Ltd
ACUTE ABDOMEN
an appendicular mass who are otherwise clinically well and stable. Patients are observed closely, kept nil by mouth and treated with cefuroxime, 750 mg i.v. t.d.s., and metronidazole, 500 mg i.v. t.d.s. Operative intervention is indicated at this stage if the patient demonstrates sign of increasing peritonitis or becomes systemically unwell. However, over the next few days, the rigidity generally settles and the limits of the mass can be clearly defined. Subsequently, the mass either resolves as the inflammation settles or increases in size as an appendicular abscess develops.
Appendicular abscess Patients with an appendicular abscess have a swinging pyrexia and tachycardia. Abscesses are most commonly found in the lateral aspect of the right iliac fossa or within the pelvis. An abscess can occasionally be detected on abdominal palpation, but rectal and/or vaginal examination is essential to identify a pelvic collection. Blood tests show a polymorphonuclear leucocytosis and accurate diagnosis can be obtained using ultrasonography. The abscess can be drained radiologically with CT or ultrasound guidance, or as an open procedure which also allows an appendicectomy to be carried out at the same time.
Interval appendicectomy Following successful conservative treatment of an appendicular mass or abscess, some surgeons advocate an elective appendicectomy as this eliminates the possibility of further attacks. However, the variability in observed recurrence rates (10–35%) leaves its role in the management of acute appendicitis disputed.
Chronic appendicitis (‘grumbling appendicitis’) Whether the clinical entity of chronic appendicitis exists and its relationship to persistent right iliac fossa symptoms is controversial. Nevertheless, such symptoms should always be investigated fully and chronic appendicitis should remain a diagnosis of exclusion. In certain situations, appendicectomy can lead to the resolution of such symptoms and the appendices can be found histologically to be chronically inflamed, fibrotic or to have altered sensory neuropeptide staining. Whether these findings result from ongoing chronic inflammation or repeated bouts of acute inflammation remains controversial. u
FURTHER READING Forrest A P, Carter D C, Macleod I B. Principles and Practice of Surgery. 3rd edition. New York: Churchill Livingston, 1995. Greenfield L J, Mulholland M, Oldham K T et al. Surgery: Scientific Principles and Practice. 2nd edition. New York: Lippincott Raven, 1997. CROSS REFERENCE Burge D. Acute abdominal emergencies in early childhood. SURGERY 2001; 19(10): 241–3.
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© 2002 The Medicine Publishing Company Ltd
tends to be restricted to ‘developed regions’ of the world and is relatively uncommon in ‘developing regions’. It has been suggested that the harder, firmer stools produced as a result of a low-fibre diet make appendicular obstruction secondary to an impacted faecolith more likely. The alteration in intestinal flora secondary to an increase in transit time has also been implicated in the pathogenesis.
Acute Appendicitis John Simpson JH Scholefield
Familial: there is weak evidence of a familial tendency to develop appendicitis. Although the exact cause is unknown, hereditary anatomical anomalies, shared dietary habits and familial resistance to intestinal flora have all been suggested. Social factors such as domestic overcrowding and poor hygiene, which can lead to an increase in respiratory and enteric infections, have also been linked to the pathogenesis.
Acute appendicitis is the most common abdominal emergency and accounts for over 60,000 hospital admissions annually in England and Wales. The incidence of appendicitis is 1.5/1000 and 1.9/1000 in males and females, respectively, and the overall lifetime risk is estimated to be 6–20%. Appendicitis is uncommon before 2 years of age, and the incidence peaks in the second and third decades, but no age group is exempt.
Pathology Inflammation of the appendix ranges from minor simple acute inflammation with spontaneous resolution to suppurative necrosis and perforation. Luminal bacteria are thought to initiate infection and bacteriological cultures from inflamed appendices usually reveal a mixed growth, commonly of Escherichia coli, Klebsiella spp., Proteus spp. and bacteroides. Organisms enter the wall at the site of an ulcer, which has usually been caused by an impacted faecolith. If the inflammatory process progresses, the wall of the appendix becomes oedematous, and purulent inflammation leads to thrombosis and gangrene. The greater omentum and small intestine can adhere to the inflamed appendix and localize the sepsis forming a phlegmatous mass or abscess. However, if perforation occurs early in the inflammatory process, generalized peritonitis results. Perforation rates are between 10–33% at the time of operation in the general population, but these figures rise at the extremes of age.
Aetiology The vermiform appendix is a vestigial structure, which is 7.5–10 cm long in an adult. Morphologically, it represents the underdeveloped distal part of the large caecum that is present in many animals. The exact cause of acute appendicitis remains unclear, but several factors have been implicated and, in some cases, the aetiology may be multifactorial. Luminal obstruction: in any blind-ending structure, luminal obstruction, which prevents the escape of secretions, inevitably leads to a rise in intraluminal pressure. This increased pressure can lead to mucosal ischaemia and the stasis provides an ideal environment for bacterial overgrowth. This sequence of events may provide a plausible explanation in many cases, as some form of obstruction can be demonstrated in over half of the appendices removed for acute appendicitis. Luminal obstruction most commonly results from an impacted faecolith, but other causes include lymphoid hyperplasia, worms (most commonly roundworms or threadworms), strictures, foreign bodies, carcinoid tumour, caecal cancer and ileocaecal Crohn’s disease.
Clinical features The history and examination can vary widely and only around 50% of patients with acute appendicitis have a classical presentation (Figure 1). The age of the patient can influence the presentation and, as the appendix is a relatively mobile structure, the clinical picture is also dictated to a large degree by its anatomical position. Furthermore, if the early stages of the disease are silent, patients may present acutely unwell with generalized peritonitis.
Diet: epidemiological studies show that the geographical incidence of acute appendicitis correlates closely with the consumption of a low-residue diet. As such, appendicitis
History: the primary feature of appendicitis is abdominal pain. Initially, because of the visceral innervation of the midgut, referred pain is commonly felt in the central abdomen. If appendicular obstruction or distension is present, this is generally colicky, but otherwise the pain tends to be more constant. As the inflammatory process continues and involves the parietal peritoneum, the pain intensifies and localizes towards the right iliac fossa. This usually occurs within 24 hours by which time patients describe the pain as sharp, and aggravated by movement and coughing. Following the onset of pain, loss of appetite and constipation are common. Patients tend to be nauseated and may have vomited, though this symptom does not usually persist.
John Simpson is an MRC Clinical Training Fellow in the Department of Surgery, University Hospital Nottingham, Nottingham, UK. He qualified from the University of Leeds, UK and trained in Nottingham, UK. His current research interests include diverticular disease and postinflammatory remodelling of the enteric nervous system. J H Scholefield is Professor of Surgery at the University Hospital Nottingham, UK. He qualified from the University of Liverpool, UK, and trained in Sheffield and London, UK. His current research interests include early the diagnosis of colorectal cancer, inflammatory bowel disease and anal fissure.
SURGERY
153
© 2002 The Medicine Publishing Company Ltd
ACUTE ABDOMEN
Anatomical location of the appendix
Clinical history and signs in patients with acute appendicitis
History
Examination
Feature Reliable Less reliable • Duration 24–36 hours • Vomiting • Initial central location • Diarrhoea/ of pain and migration constipation to right iliac fossa • Anorexia • Tachycardia • Mild pyrexia • Guarding in right iliac fossa • Percussion tenderness in right iliac fossa
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• Flushed • Fetor oris • Tenderness on rectal/ vaginal examination • Rovsing’s sign • Psoas stretch sign • Obturator test
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2
Investigations • Moderate leucocytosis with neutrophilia 1
Anatomical positions of the appendix and their approximate incidence
Examination: the patient is usually flushed with a dry tongue. An associated fetor oris is often present. Patients are usually mildly pyrexial (up to 38 °C) and have a slight tachycardia. Following localization of the pain in the right iliac fossa, there is muscular rigidity and percussion tenderness. Demonstrating rebound tenderness is not advised as it is unlikely to add anything to the examination findings at this stage and, more importantly, can be extremely uncomfortable for the patient. In cases of early appendicitis, pain can often be localized to the right iliac fossa by asking the patient to hop or to cough. The site of maximal tenderness is classically described as McBurney’s point (Figure 2) which marks the base of the appendix and lies two-thirds of the way along a line drawn from the umbilicus to the anterior superior iliac spine. Palpation of the left iliac fossa may cause pain in the right iliac fossa (Rovsing’s sign). Rectal and vaginal examination can be normal, though localized tenderness may be detected on the right side, especially if the appendix lies within the pelvis.
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3
Features influencing presentation Anatomical features (Figure 3) Retrocaecal appendix – in this position, an inflamed appendix can be protected from the anterior abdominal wall by a caecum distended with gas. Muscular rigidity is often absent and tenderness to deep palpation is lacking. There may, however, be tenderness in the right loin. The patient may hold their right hip in a slightly flexed position due to psoas spasm, as the inflamed appendix lies in contact with that muscle. In this situation, passive extension or hyperextension of the right hip may increase the abdominal pain (psoas stretch sign). Post-ileal – an inflamed appendix lying behind the terminal ileum may be difficult to diagnose for several reasons. The symptoms may be vague and, because the inflamed appendix
SURGERY
���������
lies relatively protected from the anterior abdominal wall, the pain is poorly localized. Vomiting can be more persistent and, as the appendix irritates the distal ileum, diarrhoea is more common. Pelvic – if the appendix lies in contact with the rectum, diarrhoea can be a prominent feature. Similarly, contact with the bladder may lead to frequency of micturition and microscopic haematuria. Tenderness may be lacking over McBurney’s point, though rectal or vaginal examination may localize tenderness in the rectovesical pouch or the pouch of Douglas. Psoas spasm may be present and, when the appendix lies in contact with the obturator internus, passive internal rotation of the hip may aggravate the pain (obturator sign).
154
© 2002 The Medicine Publishing Company Ltd
ACUTE ABDOMEN
Age-related features Young children – acute appendicitis in young children often has a nonspecific presentation and difficulty in differentiating it from mesenteric adenitis or enteritis can result in a delay in diagnosis. This delay, together with the underdeveloped greater omentum in young children which can often fail to localize any developing sepsis, results in much higher rates of peritonitis, perforation and abscess formation, and up to 75% of young children present in this way. Elderly – symptoms are often less pronounced in the elderly, and patients may be afebrile with a normal white cell count. In addition, a diagnosis of acute appendicitis is often not considered in this age group and may be missed, resulting in a delay in treatment and higher rates of perforation (around 50%). These factors and a diminished physiological reserve contribute to the increased mortality in this age group. Pregnancy – appendicitis occurs in 1/1500–2000 pregnancies and is the most common non-obstetric indication for laparotomy during gestation. Displacement of the appendix by the uterus during the latter stages of pregnancy can result in an atypical presentation and symptoms may be confused with the onset of labour. In contrast to the classical presentation, nausea and vomiting are usually more common and, due to the upward displacement of the appendix, tenderness can be present anywhere along the right side of the abdomen. However, as the gravid uterus can protect the inflamed appendix from the anterior abdominal wall, tenderness may not be marked. Ultrasound is a useful diagnostic aid to distinguish appendicitis from obstetric pathology. Simple acute appendicitis has negligible maternal mortality, but the risk of fetal death is around 10%. Perforation, however, significantly increases the risks to both mother and fetus, and the mortality rates rise to 2% and 30%, respectively.
Most of the changes seen in some cases of acute appendicitis, such as haziness in the right iliac fossa and dilated loops of ileum, are nonspecific. However, abdominal radiographs can occasionally demonstrate an appendicular faecolith and, as up to 50% of children under 2 years old have been reported to have a visible faecolith, a plain abdominal film may be a useful in this age group. Cross reference SURGERY 2001; 19(10): 241. Ultrasonography: high resolution ultrasonography has been shown to have high sensitivity and specificity in the diagnosis of acute appendicitis. Although not advocated as a routine diagnostic test, its value lies in its ability to obtain a diagnosis in patients with an atypical history and to exclude other pathology, particularly of the female pelvis. Laparoscopy: this allows good visualization of the abdominal and pelvic organs, and is helpful in patients with an atypical presentation, especially young women. Computer-aided diagnosis: the role of computer-aided diagnosis in the management of appendicitis is still debated. Although some trials have shown it to reduce negative laparotomy rates, the incidence of perforation and mortality, others have shown clinical judgement to be just as effective.
Differential diagnosis The variability in presentation in all age groups results in a wide range of possibilities in the differential diagnosis of suspected acute appendicitis (Figure 4).
Treatment The treatment of choice for acute appendicitis is appendicectomy. The operative mortality for early operation is less than 0.2%, but this rises to around 5% in the very young and elderly patients if perforation has occurred. In all cases, patients require adequate fluid resuscitation preoperatively. This is particularly important in patients presenting late with generalized peritonitis, who may be severely dehydrated. If an appendicular mass can be felt preoperatively in an otherwise fit patient, operation may be delayed.
Investigations Although further investigations are not required in many cases of acute appendicitis (because the presentation can be variable) they are often necessary to exclude other causes of the symptoms. Haematological: although there is no single investigation which will accurately diagnose appendicitis, approximately 90% of patients have a moderate leucocytosis (about 15,000 cells/µl), predominantly neutrophils (> 75%).
Appendicectomy Classically, the appendix is approached through a musclesplitting gridiron incision (Figure 5). This is made through McBurney’s point perpendicular to a line drawn from the umbilicus to the anterior superior iliac spine. A Lanz incision, which is placed almost horizontally low in the right iliac fossa, is also commonly used (Figure 5). The muscular layers of the anterior abdominal wall are split in the line of their fibres, and the peritoneum is exposed and opened. The caecum is identified and gently eased forward using a finger. The appendix is normally found in the retrocaecal fossa and can be delivered through the wound in a similar manner with a finger hooked behind it. If there is difficulty in delivering the appendix, the abdominal wound should be extended to afford better access. Mobilization of the caecum by dividing the peritoneal reflection along its lateral border may also be required if the appendix lies in a
Urinalysis: this is usually normal, though leucocytes or red blood cells may be present in the urine of patients with retrocaecal or pelvic appendicitis, caused by irritation of the bladder or ureter by the adjacent inflammation. Urine microscopy and culture will identify a urinary tract infection if clinical signs are equivocal. Pregnancy testing: this is vital in all women of reproductive age. Imaging Plain radiographs: these are largely unhelpful in diagnosis, but are important to exclude other causes of abdominal pain.
SURGERY
155
© 2002 The Medicine Publishing Company Ltd
ACUTE ABDOMEN
Lanz and gridiron incisions for appendicectomy
Differential diagnosis of appendicitis Thorax and respiratory tract • Tonsillitis • Pneumonia Abdomen • Acute cholecystitis • Perforated peptic ulcer • Gastroenteritis • Mesenteric adenitis • Terminal ileitis • Meckel’s diverticulitis • Colonic diverticulitis/appendicular diverticulitis • Intestinal obstruction • Intussusception
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Pelvis • Ectopic pregnancy • Ruptured ovarian follicle (mittelschmerz) • Torted ovarian cyst • Salpingitis/pelvic inflammatory disease
5
5 days. Following discharge, patients should be advised to avoid physical exertion for 2–3 weeks and then to reintroduce activities gradually.
Urinary system • Right pyelonephritis • Right ureteric colic Other • Diabetic abdomen • Porphyria • Rectus sheath haematoma • Pancreatitis • Pre-herpetic pain (right lower dorsal spinal roots)
Postoperative complications Wound infection: this is the most common complication and rates vary according to the degree of operative contamination. In low-risk cases with simple acute appendicitis, the infection rate is less than 5%. If, however, the appendix is gangrenous or perforation has occurred, this can rise to around 20%. These rates can be reduced with the use of perioperative antibiotics and intraoperative peritoneal lavage. Delayed primary closure is now seldom used, but may be reserved for severely contaminated wounds.
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high retrocaecal position. Once delivered, the appendicular mesentery is divided and the vessels ligated. The base is crushed, ligated and the inflamed appendix is removed. Whether the appendicular stump is inverted or left following ligation probably makes no difference. If free peritoneal fluid is present, lavage with warmed saline is usually performed and the wound is then closed in layers. A peritoneal drain is seldom necessary, though a corrugated or tube drain can be used if there is considerable purulent fluid in the retrocaecal space or pelvis. Perioperative broad-spectrum antibiotics (e.g. one to three doses of cefuroxime, 750 mg i.v., and metronidazole, 500 mg i.v.) should be used in all appendicectomies, as they reduce postoperative intra-abdominal abscess formation and wound infection. In early appendicitis, it is possible to remove the appendix laparoscopically. Studies have shown that postoperative pain, wound complications and length of hospital stay all tend to be lower with this technique, but the operative time is increased. Postoperatively, patients are permitted to take fluid orally and diet is normally reintroduced within 24–48 hours. In cases of perforated appendices with advanced sepsis and generalized peritonitis, intravenous antibiotics should be continued for
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Intra-abdominal abscess: gross peritoneal contamination can lead to postoperative intra-abdominal abscess formation. The common sites are subphrenic and pelvic. Patients present with rigors and have a swinging pyrexia. Ultrasound examination is useful in diagnosis and the treatment of choice is drainage under ultrasound or computed tomography (CT) guidance. Faecal fistula: this is a relatively rare complication and occurs from the appendix stump. It can result from an insecure ligature or caecal ischaemia. Most fistulas settle with conservative management.
Appendicular mass If there is a delay in presentation, a tender mass can often be felt in the right iliac fossa. There is overlying muscular rigidity, but otherwise the abdomen is soft and non-tender. The mass consists of an inflamed or perforated appendix surrounded by greater omentum, caecum and adherent loops of small intestine. Conservative treatment is indicated for patients with
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an appendicular mass who are otherwise clinically well and stable. Patients are observed closely, kept nil by mouth and treated with cefuroxime, 750 mg i.v. t.d.s., and metronidazole, 500 mg i.v. t.d.s. Operative intervention is indicated at this stage if the patient demonstrates sign of increasing peritonitis or becomes systemically unwell. However, over the next few days, the rigidity generally settles and the limits of the mass can be clearly defined. Subsequently, the mass either resolves as the inflammation settles or increases in size as an appendicular abscess develops.
Appendicular abscess Patients with an appendicular abscess have a swinging pyrexia and tachycardia. Abscesses are most commonly found in the lateral aspect of the right iliac fossa or within the pelvis. An abscess can occasionally be detected on abdominal palpation, but rectal and/or vaginal examination is essential to identify a pelvic collection. Blood tests show a polymorphonuclear leucocytosis and accurate diagnosis can be obtained using ultrasonography. The abscess can be drained radiologically with CT or ultrasound guidance, or as an open procedure which also allows an appendicectomy to be carried out at the same time.
Interval appendicectomy Following successful conservative treatment of an appendicular mass or abscess, some surgeons advocate an elective appendicectomy as this eliminates the possibility of further attacks. However, the variability in observed recurrence rates (10–35%) leaves its role in the management of acute appendicitis disputed.
Chronic appendicitis (‘grumbling appendicitis’) Whether the clinical entity of chronic appendicitis exists and its relationship to persistent right iliac fossa symptoms is controversial. Nevertheless, such symptoms should always be investigated fully and chronic appendicitis should remain a diagnosis of exclusion. In certain situations, appendicectomy can lead to the resolution of such symptoms and the appendices can be found histologically to be chronically inflamed, fibrotic or to have altered sensory neuropeptide staining. Whether these findings result from ongoing chronic inflammation or repeated bouts of acute inflammation remains controversial. u
FURTHER READING Forrest A P, Carter D C, Macleod I B. Principles and Practice of Surgery. 3rd edition. New York: Churchill Livingston, 1995. Greenfield L J, Mulholland M, Oldham K T et al. Surgery: Scientific Principles and Practice. 2nd edition. New York: Lippincott Raven, 1997. CROSS REFERENCE Burge D. Acute abdominal emergencies in early childhood. SURGERY 2001; 19(10): 241–3.
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