Hirschsprung's Disease

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ENTEROCOLITIS
Enterocolitis in patients with Hirschsprung's disease remains the major cause of significant morbidity and mortality today. Enterocolitis is usually accompanied by explosive diarrhea, abdominal distention, and fever. Pathologically, enterocolitis is defined as an inflammation of the lining of either the colon or the small intestine. As the disease progresses, the lining erodes, and the inside of the intestine becomes filled with pus. If the process is left to proceed untreated, patients become very ill and perforation of the intestine may occur.

The causes of the enterocolitis are not fully understood. However, several contributory factors have been identified: intestinal stasis (poor movement of intestinal contents) with bacterial invasion of the intestine wall, decrease in intestinal defense mechanisms, and abnormal mucins (secretions from the intestine). Patients with trisomy 21 (Down's Syndrome) are known to have an increased risk for developing enterocolitis. The diagnosis of enterocolitis is made on the basis of a patient having diarrhea or foul smelling stool with abdominal distention (69%), vomiting (51%), fever (34%), and often sleepiness (27%). Along with the history and physical examination, specific abdominal x-ray findings may point to enterocolitis. Most commonly, enterocolitis presents in the post-pull-through period. This form of enterocolitis may be due to an excessively tight pull-through or may be related to spasm of the anal sphincter. In most cases enterocolitis resolves between the ages of three and less than three years.

The treatment of Hirschsprung's disease-associated enterocolitis begins with a series of aggressive rectal washouts using a large-site rectal tube to decompress the colon above the anal sphincter. Enemas alone are ineffective because they do not allow for adequate decompression of the colon. These serial washouts should be accompanied by either intravenous antibiotics in more severe cases or oral metronidazole (Flagyl) if the case is mild or chronic. In some cases a colostomy may be needed to adequately decompress the bowel. Recurrences of enterocolitis are common and may be due to mucosal changes that occurred early in the life of the child.

HIRSCHSPRUNG'S DISEASE IN THE OLDER OR ADULT PATIENT
Rarely, Hirschsprung's disease may present in the adolescent or adult. In general, these patients have adapted to their disease through the regular use of cathartics and enemas. In general, complication rates with most procedures on adults and adolescents seem to be higher than in children. Often a primary pull-through without colostomy cannot be performed because of the markedly enlarged colon. In order to treat this problem in older patients some have advocated the performance of a posterior anorectal myectomy where the muscle down near the anus is divided. Most surgeons recommend a standard pull-through, unless the patient has what is called ultra-short segment Hirschsprung's disease (see next section).

ULTRA-SHORT SEGMENT HIRSCHSPRUNG'S DISEASE
The term ultra-short Hirschsprung's disease has prompted a great deal of confusion among clinicians. This confusion relates to the diagnosis, treatment, and even the occurrence of this diagnosis. The major problem with ultra-short Hirschsprung's disease is the fact that the gold standard for making the diagnosis of standard Hirschsprung's disease--the rectal biopsy--may show ganglion cells. Many of these children not only have chronic constipation, often for many years, but also fecal soiling, which makes it difficult to differentiate other non-Hirschsprung's causes of constipation and soiling.

In general, ultra-short Hirschsprung's disease consists of a 2- to 4-cm segment of aganglionosis near the anus. A contrast enema may not show a transition zone. However, despite these negative findings, manometry will usually show a failure of the usual anorectal reflex relaxation with blowing up a balloon in the rectum. It is possible that several children with this diagnosis may be overlooked because many centers do not perform anorectal manometry routinely. The preferred treatment of a definitive case of ultra-short segment Hirschsprung's disease is an anorectal myectomy, provided that one has confirmed ganglion cells from a prior biopsy specimen. This operation is performed by removing a narrow strip of muscle from the posterior part of rectum near its union with the anus.

LONG SEGMENT AND TOTAL COLONIC HIRSCHSPRUNG'S DISEASE
Long segment disease represents a significant proportion of cases of Hirschsprung's disease diagnosed in newborns. The mortality in this group of infants is also generally higher and probably is related to the increased incidence of enterocolitis present at the time of diagnosis. Delay in diagnosis, which is more common in long segment disease, leads to an increased incidence of enterocolitis and a resultant increased mortality.

Total colonic aganglionosis accounts for approximately 3% to 12% of infants with Hirschsprung's disease. These patients comprise a unique subset of patients because of the increased morbidity and mortality. The diagnosis of total colonic aganglionosis can be difficult. X-ray studies may show enlarged loops of bowel, and a contrast enema may show a question mark-shaped colon owing to the rounded edges of the large intestines. X-ray studies are diagnostic, however, in only 20% to 30% of all patients with total colonic aganglionosis. The diagnosis generally is made at the time of an abdominal operation for a bowel obstruction or for a leveling colostomy for Hirschsprung's disease. Looking for ganglion cells in the appendix is almost always diagnostic. A family history of Hirschsprung's disease can be found in many of these children (12.4% to 33%). The male-to-female ratio also is decreased so that there is almost an equal number of males and females.

Complications associated with total colonic aganglionosis are considerably higher than for standard length Hirschsprung's disease. Many infants with total colonic Hirschsprung's disease require parenteral nutrition (calories by the intravenous or IV route), making catheter sepsis (infection from special IV lines), failure to grow, ostomy dysfunction, electrolyte imbalance, and dehydration commonly encountered complications. Mortality ranges from 0 to 44% depending on the series of patients, which emphasizes the severity of this variant of Hirschsprung's disease.

Conventional treatment for total colonic aganglionosis begins with the creation of a properly formed enterostomy (as ostomy formed from various parts of the bowel). More recently, a few surgeons have been successful in managing a limited number of these patients with a primary pull-through. Some surgeons believe that the performance of a pull-through procedure should be withheld until the child is toilet trained because diaper rash can be severe in this disease. Several operative approaches can be considered. In general, however a standard-length Duhamel or endorectal pull-through yields the best results compared with other methods.

OUTCOME
The outcome for each of the operations discussed can be somewhat controversial. Outcome is measured in terms of problems with constipation, soiling, enterocolitis and enuresis (urinary incontinence). Individual surgeons may have distinct preferences for one operation versus another based on their own experience and results. Various reports in the medical literature demonstrate widely variable results. This is in part because the extent to which each of these problems is reported may depend on the way in which the information was gathered or on the availability of patients for long term follow up.

In general there is a spectrum of how patients with Hirschsprung's disease will do after surgery. Some will appear to have little if any stooling abnormality. A few will need further corrective surgery at some point in their lives. What is most important is that most will do very well, but may need some manipulation of the diet or the addition of a medication to aid in the passage of stool. The operation to correct Hirschsprung's disease should not be the child's last association with the pediatric surgeon. All of these patients need to be followed closely after surgery and then ideally for years in the pediatric surgical clinic so that if problems arise, they can be dealt with before they become serious issues.

CONCLUSION
Hirschsprung's disease is an important part of the differential diagnosis of intestinal obstruction in newborns. The increased rate of diagnosis in the newborn period is the result of improvements in diagnostic techniques, including suction rectal biopsy, expertise in pathologic interpretation, increased experience with barium enema study interpretation, addition of histochemical and immunohistochemical analyses, and increased physician awareness. This increasing awareness has led to a shift in the average age of diagnosis from childhood to the newborn and infant age group. Most importantly, this increased awareness has led to prompt institution of appropriate resuscitation and treatment, resulting in a decrease in mortality. Finally, refinements in surgical technique and preoperative and postoperative care have reduced mortality and morbidity greatly and have improved significantly the long-term outcome for these patients.

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