Inguinal Hernia in Infants With Very Low Birth Weight

Inguinal Hernia in Infants With Very Low Birth Weight By James M. DeCou and Michael W.L. Gauderer Greenville, South Carolina Inguinal hernias (lH) are among the most commonly encountered surgical problems in infants with very low birth weight (VLBW, <1,500 g) with a reported incidence of 16%. A trend toward earlier operation has emerged in recent years, with most now being repaired before discharge from the neonatal intensive care unit. The authors review the many special concerns regarding the management of IH in this patient population, including the timing of repair, the risk of incarceration, anesthetic management, the frequency of bilaterality, the high incidence of undescended testes, and the technical aspects and complications associated with IH repair in the VLBW infant. Copyright © 2000 by W.B. Saunders Company

I

MPROVEMENTS in neonatal care over recent decades has greatly increased the survival rate of infants with very low birth weight (VLBW), defined as those weighing less than 1,500 g. Because the likelihood of an inguinal hernia (lH) developing is inversely proportional to birth weight, the number of small babies with IH has increased significantly. Multiple factors make IH a challenge in these patients. These include the presence of comorbid disease, the risk of incarceration, anesthetic risks, the frequencies of bilaterality and undescended testis, optimal timing of the operation, and the technical difficulties of the repair. PATHOPHYSIOLOGY

Indirect IH in the newborn is caused by persistence of the processus vaginalis, a diverticulum of peritoneum, that in boys follows the testis as it descends into the scrotum. I In girls, the processus follows the round ligament through the inguinal canal to the labia majora. Between the 36th and 40th weeks of gestation, obliteration of the processus vaginalis typically occurs. Failure of the processus to close at the level of the internal ring leads to development of a communicating hydrocele or an indirect IH. When infants are born prematurely «36 weeks' gestation), an increase in intraabdominal pressure after birth tends to keep the processus open. This is felt to explain the higher incidence of IH in premature versus full-term infants. In addition, descent of the testis typically is not complete until full term or later, thus, frequently

From the Department of Pediatric Surgery, The Children's Hospital of Greenville Hospital System. Greenville, Sc. Address reprint requests 10 Michael WL. Gal/derer, MD, Chief, Department of Pediatric Surgery, The Children's Hospital of Greenville Hospital System, 890 W Faris Rd, MMOB Suite 440, Greenville, SC 29605-4253. Copyright © 2000 by WB. Saunders Company 1055 -8586/00/0902-0007$1 O. 00/0 84

adding the problem of an undescended or poorly fixed testis to a difficult hernia repair. EPIDEMIOLOGY

The incidence of IH in premature infants ranges from 6% to 30% compared with 1 % to 5% in full-term infants.l-4 For the specific subset of VLBW infants, a prior study by one of the authors found the incidence to be 16%.4 The rate of 30% was in babies weighing less than 1,000 g,2 supporting the hypothesis that incidence is inversely related to birth weight. Male infants are affected with IHs up to 9 times more frequently than girls, 1,4-6 although the study of infants less than 1,000 g reported a 2:1 female to male ratio.2 In addition to low birth weight and male gender, bronchopulmonary dysplasia and a high neonatal risk score have been shown to be risk factors for development of IH. 3,4 PRESENTATION

IH in VLBW infants commonly present during the neonatal period, but many also frequently become apparent shortly after discharge home and can occur at any age. Hernias are bilateral on examination in approximately half of cases and unilateral in half, with the majority of unilateral hernias on the right side.2.4. 7 Incarceration occurs in 18 % to 31 % of infant IH, 71 % to 97% of which can be reduced. 2.4,5,7 PREOPERATIVE CONSIDERATIONS

VLBW infants frequently have comorbid factors that must be considered before IH repair. The coexistence of conditions such as bronchopulmonary dysplasia, apnea and bradycardia (A&B), patent ductus arteriosus, intraventricular hemorrhage, hydrocephalus requiring ventriculoperitoneal shunting, cardiac and other congenital malformations, and connective tissue disorders, must be taken into account before planning the repair. Steroids preferably should be minimized to decrease wound healing problems. Antibiotics typically are only administered in cases of congenital heart disease or incarceration. The optimal timing of IH repair sometimes is difficult to determine. Before recent advances in anesthetic and neonatal care, the majority of VLBW infants with IH were discharged home from the neonatal intensive care unit (NlCU), then returned for IH repair when they reached a certain age or weight or when their lung disease stabilized. In addition to an increased risk of incarceration with this approach, many of these hernias reached a very large size (Fig 1), making eventual herniorrhaphy Seminars in Pediatric Surgery, Vol 9, No 2 (May), 2000: pp 84-87

85

INGUINAL HERNIA

babies very closely after reduction and to consider operation if there is any question of necrotic intestine. An incarcerated ovary, however, even if irreducible, is usually not an urgent problem.s,lo In a series containing 22 girls with incarceration treated nonurgently, Moss and HatchS found no necrotic or severely ischemic ovaries at the time of repair. ANESTHETIC CONSIDERATIONS

The anesthetic management of these small infants often is difficult, usually because of lung disease and their propensity for A&B. A variety of anesthetic modalities have been used for VLBW patients, including local, spinal, caudal, epidural, and general techniques. Most of the debate centers on spinal versus general anesthesia. Spinal block without sedation is associated with the lowest incidence of postoperative A&B.12-14 Spinal plus sedation yields an incidence of A&B that is equal to or worse than that with general anesthesia. I3 The disadvantages of spinal anesthesia for IH include the following: the spinal is placed in an awake, unsedated, usually

Fig 1. A former VLBW infant with a huge inguinal hernia, which at the time of his very delayed repair, was problematic because of a loss of domain in the abdominal cavity.

even more difficult. A trend toward IH repair before discharge from the NICU began in the 1980s, and now clearly seems to be the consensus. 4-IO In a 1996 survey of the Section on Surgery of the American Academy of Pediatrics, 71 % of responders report that they perform the repair before NICU discharge. Io This approach has several advantages, including a decreased risk of incarceration, continuity of care by neonatologists and NICU nurses, and avoidance of the problem of achieving close outpatient follow-up in this patient population. Our approach now is to wait until the infant is otherwise ready for discharge home, which typically means that any comorbid conditions have stabilized and that his or her weight is at least 1,800 g. Incarceration continues to be a concern while awaiting herniorrhaphy. As noted above, the majority of incarcerations can be reduced, and our feeling is that as long as the infant is in the NICU, we can repeatedly reduce the incarceration as necessary. The use of a truss made from a piece of foam material and Duoderm (ConvaTec; BristolMyers Squibb Co, Princeton, NJ) has been reported as a possible way to maintain hernia reduction until the infant is ready to undergo repair. II An IH with irreducible intestine, of course, would require immediate operation. And contrary to popular belief, recently we experienced that it is possible to reduce necrotic intestine in a VLBW infant (Fig 2). Therefore, it is important to watch these

Fig 2. (A) Incarcerated right inguinal hernia before reduction. (B) This is the same patient immediately after reduction. He later underwent an emergency celiotomy and was found to have a reduced segment of necrotic small intestine.

86

DECOU AND GAUDERER

crying infant; there is a time limit within which the surgeon must complete an often difficult, frequently bilateral repair; and because the peritoneum is poorly anesthetized, very large hernias are difficult to reduce. Grosfeld 1 stated a preference for general anesthesia for IH repairs when a skilled pediatric anesthesiologist is available, reserving local or spinal techniques for situations when such personnel are not available. In a study by Krieger et al 6 of 52 premature infants who underwent IH repair under general anesthesia, 75% were extubated immediately and another 15% were extubated the next day. Thirty-one percent experienced mild to moderate apnea postoperatively (75% had apnea preoperatively), but none required reintubation. Our preference is general anesthesia plus injected local bupivacaine before skin incision, which allows complete avoidance of narcotics, thus minimizing postoperative respiratory complications. Another area of controversy relates to whether overnight postoperative A&B monitoring is necessary for premature infants in whom IH develop after discharge. Although studies by Melone et aP5 and Allen et aP6 concluded that outpatient IH repairs can be performed safely in this patient population, the consensus is that infants below a certain postconceptual age should be monitored overnight in the hospital because of the risk of A&B.l,7,1O,13,17 A combined analysis of several studies of postoperative apnea concluded that to have 95% statistical confidence of no apnea, former preterm infants must be at least 48 weeks' postconceptual age. 17 It is our practice to admit all patients less than 50 postconceptual weeks for A&B monitoring overnight. SURGICAL MANAGEMENT

These are challenging operations. Several anatomic factors in the VLBW infant are involved. First, the babies are small and the structures of the groin are even smaller. Loupe magnification is recommended. The hernia sacs can be relatively large and extremely thin (Fig 3) with splaying of the delicate cord structures. The testis frequently is undescended or is fixed poorly in the scrotum, in which case it comes up easily with the hernia sac. The options for orchiopexy in this setting include creation of a standard dartos pouch versus simply securing the testis with absorbable sutures placed in the apex of the inverted scrotum or with trans scrotal sutures tied on the outside. A sliding component to the IH is often present, especially in girls with ovary or tube and occasionally uterus in the sac. These sacs usually are closed with a purse-string suture that is then secured deep to the transversalis fascia. Typically, the IH is approached via an inguinal incision, the sac is separated from the cord structures, and high suture ligation is performed. We feel that silk sutures should not be used in the repair because of a risk of late

Fig 3.

Large, extremely thin hernia sac (5) with adjacent testis (T).

infection. We agree with the majority of investigators who recommend contralateral inguinal exploration in VLBW infants because of the high rate of contralateral hernia or patent processus vaginalis. 1-8,10 The incidence of contralateral IH or patent processus in 3 different series was 85% to 88%.5-7 Several studies on contralateral IH development after unilateral repair have recommended against routine contralateral exploration in essentially all children except premature infants.18-2o Laparoscopic exploration of the contralateral groin via the open ipsilateral sac is a good alternative in older infants and children, but in the VLBW infant it risks tearing the fragile sac. We agree with Grosfeld, l however, that in cases of incarceration, contralateral exploration generally is not done. We also feel that additional noncritical procedures, such as circumcision, generally should be performed at a later date. A few techniques recently have been described for use in special circumstances. Applebaum et aFl has detailed an alternative method for high ligation of especially large or difficult sacs. In this technique, the hernia sac is purposefully opened, the edges retracted, and a pursestring suture is run around the inner surface of the opened sac at the level of the internal ring, incorporating peritoneum and muscle while avoiding the cord structures. A sac that becomes tom during a conventional dissection can be repaired in a similar fashion. Misra et aF2 has described a transperitoneal technique of closing the internal ring, which is useful in treating irreducible incarcerated IH. This technique, in which a purse-string suture is placed around the internal ring from the inside, has the advantages of optimal reduction and inspection of the incarcerated intestine and avoidance of the inflamed inguinal canal. It also allows for contralateral exploration and repair, which, as noted above, generally is not done with incarceration. Schier23 has described a technique of

87

INGUINAL HERNIA

laparoscopic herniorrhaphy, although this was only done in girls, and none were infants. OUTCOME

The majority of VLBW infants do well after IH repair. Overall complication rates of 2% to 8% and recurrence rates of 1 % to 3% have been reported. 4-7 Rescorla and Grosfeld 7 reported a 4.5% complication rate for incarcerated hernias that had been reduced versus a rate of 33% for irreducible hernias. In a follow-up study of male infants with incarcerated IH, Puri et a1 24 documented testicular atrophy in only 2.3%, a rate much lower than the previously reported 15%. Surgical mortality has been reported rarely.2 In our experience with repair of relatively large IH in

VLBW infants, postoperative scrotal swelling is common. Because it often is mistaken for a recurrent hernia and can take up to 1 to 2 months to resolve, we find it helpful to inform parents and neonatologists about this possibility. SUMMARY

The management ofVLBW infants with IH is challenging to pediatric surgeons, anesthesiologists, and neonatologists. The trend in recent years has been toward earlier repair, preferably before discharge from the NICU. A team approach is mandatory, and the timing and performance of the repair must be individualized, utilizing a variety of strategies and techniques.

REFERENCES 1. Grosfeld JL: Current concepts in inguinal hernia in infants and children. World J Surg 13:506-515, 1989 2. Harper RG, Garcia A, Sia C: Inguinal hernia: Acommon problem of premature infants weighing 1,000 grams or less at birth. Pediatrics 56:112-115 , 1975 3. Hrabovsky EE, Sigmund WR, Mullett MK: Inguinal hernia in the stressed premature infant. Perinatol-NeonatoI7:45-51, 1983 4. Rajput A, Gauderer MWL, Hack M: Inguinal hernias in very low birth weight infants: Incidence and timing of repair. J Pediatr Surg 27:1322-1324,1992 5. Moss RL, Hatch EI: Inguinal hernia repair in early infancy. Am J Surg 161:596-599, 1991 6. Krieger NR, Shochat SJ, McGowan V, et al: Early hernia repair in the premature infant: Long-term follow-up . J Pediatr Surg 29:978-982, 1994 7. Rescorla FJ, Grosfeld JL: Inguinal hernia repair in the perinatal period and early infancy: Clinical considerations. J Pediatr Surg 19:832-837, 1984 8. Groff DB, Nagaraj HS, Pietsch JB: Inguinal hernias in premature infants operated on before discharge from the neonatal intensive care unit. Arch Surg 120:962-963, 1985 9. Misra D, Hewitt G, Potts SR, et al: Inguinal herniotomy in young infants, with emphasis on premature neonates. J Pediatr Surg 29: 14961498, 1994 10. Wiener ES, Touloukian RJ, Rodgers BM, et al: Hernia survey of the Section on Surgery of the American Academy of Pediatrics. J Pediatr Surg 31 : 1166-1169, 1996 11 . Ruderman JW, Schick JB , Sherman M, et al: Use of a truss to maintain inguinal hernia reduction in a very low birth weight infant. J PerinatoI15:143-145,1995 12. Gallagher TM, Crean PM: Spinal anaesthesia in infants born prematurely. Anaesthesia 44:434-436, 1989

13. Welborn LG, Rice LJ, Hannallah RS , et al: Postoperative apnea in former preterm infants: Prospective comparison of spinal and general anesthesia. Anesthesiology 72:838-842, 1990 14. Somri M, Gaitini L, Vaida S, et al: Postoperative outcome in high-risk infants undergoing herniorrhaphy: Comparison between spinal and general anaesthesia. Anaesthesia 53:762-766, 1998 15. Melone JH, Schwartz MZ, Tyson KR, et al: Outpatient inguinal herniorrhaphy in premature infants: Is it safe? J Pediatr Surg 27:203208, 1992 16. Allen GS, Cox CS, White N, et al: Postoperative respiratory complications in ex-premature infants after inguinal herniorrhaphy. J Pediatr Surg 33 :1095-1098, 1998 17. Cote CJ, Zaslavsky A, Downes JJ, et al: Postoperative apnea in former preterm infants after inguinal herniorrhaphy. Anesthesiology 82:809-822, 1995 18. Given JP, Rubin SZ: Occurrence of contralateral inguinal hernia following unilateral repair in a pediatric hospital. J Pediatr Surg 24:963-965, 1989 19. Surana R, Puri P: Is contralateral exploration necessary in infants with unilateral inguinal hernia? J Pediatr Surg 28:1026-1027,1993 20. Tackett LD, Breuer CK, Luks Fl, et al : Incidence of contralateral inguinal hernia: A prospective analysis. J Pediatr Surg 34:684-688, 1999 21. Applebaum H, Bautista N, Cymerman J: Alternative method of repair for the difficult infant hernia. J Pediatr Surg (in press) 22. Misra D, Hewitt G, Potts SR, et al: Transperitoneal closure of the internal ring in incarcerated infantile inguinal hernias. J Pediatr Surg 30:95-96, 1995 23. Schier F: Laparoscopic herniorrhaphy in girls. J Pediatr Surg 33 :1495-1497,1998 24. Puri P, Guiney EJ, O'Donnell B: Inguinal hernia in infants: The fate of the testis following incarceration. J Pediatr Surg 19:44-46, 1984