HEIDI C. WERNER
HISTORY OF PRESENT ILLNESS
The patient, an 11-month-old girl with a history of chronic constipation, presented to the emergency department with her last bowel movement having been 3 weeks ago. Her regular bowel pattern has been two stools per month, which were accompanied by significant straining. No blood or mucous was noted with any of these stools. Two days prior to this visit she had fever with decreased oral intake and decreased urine output. She also seemed to be having increased abdominal distention. These symptoms did not improve with several phosphate enemas at home. Prior to this episode she had normal weight gain without vomiting or diarrhea.
The patient was delivered at term gestation and there were no complications during the pregnancy. She was evaluated at 4 days of life because she had not passed meconium. Over the next few months there were several interventions for constipation including prune juice, increased water intake, and changes in formula. Each intervention seemed to initially produce more frequent bowel movements, and then the pattern would worsen again. Bowel movements tended to be loose, watery, and small in volume. Otherwise, her review of systems was negative. The patient has been on docusate since 9 months of age. She has had two episodes of otitis media. Thyroid function tests, including thyroid stimulating hormone, were normal.
T 38.2°C; RR 36/min; HR 140 bpm; BP 90/60 mmHg
Weight 8.7 kg (25th-50th percentile); Height 74.5 cm (50th percentile); Head Circumference 45.5 cm (75th percentile)
Initial examination revealed a quiet but uncomfortable infant. Physical examination was remarkable for mild erythema of the posterior oropharynx, and erythematous tympanic membranes with decreased mobility. The abdomen was distended with distant bowel sounds. The abdominal examination also revealed palpable stool in the left quadrant. On the rectal examination, there were no fissures, the anus was patent, and there was no stool in the ampulla.
Serum chemistries revealed the following: sodium, 130 mEq/L; potassium, 5.0 mEq/L; chloride, 107 mEq/L; bicarbonate, 14 mEq/L; blood urea nitrogen, 66 mg/dL; and creatinine, 0.3 mg/dL. An abdominal obstruction series showed increased stool with dilated loops of bowel but no air-fluid levels (Figure 12-1).
FIGURE 12-1. Abdominal radiograph.
COURSE OF ILLNESS
In the emergency department she was treated for dehydration with intravenous normal saline fluid boluses. She was treated with amoxicillin for otitis media. She also received two pediatric phosphate enemas that produced small amounts of liquid stool. She subsequently had three episodes of bile-tinged emesis. Later, on the first day of admission, she became more irritable with an increasing abdominal girth. Cultures of the blood and urine were negative.
Serial abdominal obstruction series did not show any change during the first 2 days of admission. However, with continuing enemas the patient’s abdominal girth decreased (from 48 to 41 cm) as her stool-output increased. On the third day of hospitalization, radiographic barium enema was performed (Figure 12-2) that suggested the diagnosis.
FIGURE 12-2. Radiographic enema from a patient with a similar diagnosis.
DISCUSSION CASE 12-1
Based on the history, the patient has been constipated for her entire life. She also failed to pass meconium in the first 48 hours of life. Hirschsprung disease should, therefore, be at the top of a differential list. However, there are several other diagnoses to consider in the infant or child with delayed passage of meconium (Table 12-2).
TABLE 12-2.Diagnoses to consider in the patient with delayed passage of meconium.
The barium enema (Figure 12-2) revealed a funnelshaped transition zone that suggested the diagnosis of Hirschsprung disease. The transition zone probably would have been more obvious had the patient not received several phosphate enemas prior to the study. Endoscopic rectal suction biopsy was inconclusive. A full-thickness surgical biopsy showed no ganglion cells in 100 sections and was diagnostic of Hirschsprung disease. The patient underwent a successful Duhamel pull-through procedure.
INCIDENCE AND HISTORY
Hirschsprung disease, or aganglionosis of the bowel, is the most common cause of lower intestinal obstruction in neonates. It is characterized by abnormal innervation of the distal bowel, beginning at the anus and extending proximally for a variable distance. The defect results from a failure of neural crest cell caudal migration. The primary histologic finding is the absence of meissner and Auerbach plexuses, hypertrophied nerve bundles between the circular and longitudinal muscles and in the submucosa. This abnormal innervation leads to abnormal tone and motility of the bowel, and predisposes to obstruction.
Hirschsprung disease occurs in 1 per 5000 live births. The overall male to female ratio is 3:1. In 80% of patients, the aganglionic segment does not extend above the sigmoid, while the entire colon and some small bowel may be involved in 3%. Recurrent abdominal distention, emesis, failure to thrive, and acute enterocolitis allow diagnosis of 60% of patients by 3 months of age. More than 50% of affected children are diagnosed within the first year of life, and nearly all are diagnosed by within the first 2 years of life; a minority of children with Hirschsprung disease is not diagnosed until adolescence. Hirschsprung disease is associated with Down syndrome, which occurs in 9%-11% of Hirschsprung disease cases, and cardiac anomalies, which occur in 6%-8% of cases. Conditions less commonly associated with Hirschsprung disease include neuroblastoma, deafness, and central hypoventilation syndrome. Additionally, Hirschsprung disease, multiple endocrine neoplasia type 2 (MEN2A), and familial medullary thyroid cancer are all associated with germ line mutations of the RET-protooncogen; up to 5% of patients with Hirschsprung disease carry the MEN2A RET-mutations and consequently have an increased risk of developing medullary thyroid carcinoma.
Most (95%) full-term infants with Hirschsprung disease fail to pass meconium during the first 24 hours of life. Normal full-term infants pass meconium within 24 hours (90%) to 48 hours (99%) of life. Therefore, any neonate who fails to pass meconium within 48 hours should be suspected of having Hirschsprung disease. These infants may also develop vomiting and abdominal distention during the first week of life. Enterocolitis, a consequence of delayed diagnosis in a neonate with significant bowel involvement, is characterized by fever, abdominal distention, and explosive, foul-smelling, bloody diarrheal stools. Hirschsprung enterocolitis may be complicated by intestinal necrosis or perforation and sepsis.
Findings in the older child include a history of severe constipation from birth, failure to thrive, and abdominal distention. Older children may come to attention by presenting with either complete intestinal obstruction or enterocolitis. The rectal ampulla is usually empty on digital rectal examination.
Abdominal radiographs. In children with Hirschsprung disease, a plain-film of the abdomen may show distended loops of colon; air is usually present in the small bowel proximal to the obstruction.
Barium enema. Barium enema is suggestive in approximately 80% of cases. A barium enema should be performed without bowel preparation so that the large rectum dilated with stool can be appreciated. The characteristic appearance of the barium enema occurs because aganglionosis of the distal colon results in hypertonic contraction of the affected bowel. The normal proximal bowel becomes dilated. Between the two segments, a transition zone of bowel develops. This transition zone lacks innervation but partially distends under the influence of the peristaltic activity of the normal bowel pushing the bowel contents into the contracted distal segment. This transition zone is generally funnel-shaped. Variations of this appearance include an abrupt transition from dilated to narrowed bowel and, in some cases, funneling of the bowel incrementally over a long segment of bowel, making the change barely perceptible. Dilation of the rectum to the anal verge is diagnostic of functional constipation and rules out Hirschsprung disease.
Anal manometry. In older children, anal manometry may facilitate the diagnosis of Hirschsprung disease, with a reported sensitivity of 95%. Failure of the internal sphincter to relax in response to inflation of a rectal balloon suggests Hirschsprung disease.
Rectal biopsy. The absence of ganglion cells in the myenteric (Auerbach) and submucous (Meissner) plexus by rectal suction biopsy is diagnostic for Hirschsprung disease. Staining for the presence of acetylcholinesterase may be more reliable than recognizing the absence of ganglion cells. If the suction biopsy is not conclusive, a full-thickness biopsy is mandatory. Complications of mucosal suction biopsy are rare. In a review of 1340 mucosal biopsies, there were three cases of hemorrhage requiring packed red blood cell transfusion and three clinical perforations.
Other studies. In children with enterocolitis, the complete blood count frequently reveals anemia and leukocytosis.
Emergency management of intestinal obstruction or enterocolitis includes gastric decompression (e.g., nasogastric tube), initiation of parenteral nutrition, avoidance of oral intake, and, for enterocolitis, empiric antibiotic therapy to cover biliary and intestinal pathogens. Empiric antibiotics may include beta-lactam/beta-lactamase inhibitors (e.g., ampicillin-sulbactam, piperacillintazobactam) or third-generation cephalosporins in combination with metronidazole.
Operative intervention is necessary to treat Hirschsprung disease. The original operation (Swenson procedure) consisted of removing the defective distal colon and performing end-to-end anastomosis 2 cm above the anal canal. With this procedure, the defective aganglionic tissue is completely resected and the proximal ganglionated colon and anal canal are left in the normal anatomic position.
For total colonic aganglionosis, some surgeons prefer initially performing a defunctionalizing colostomy or an ileostomy to avoid the hazards of enterocolitis. Definitive surgery is usually performed 6 months to 1 year after the initial colostomy. The endorectal pull-through procedure is widely practiced. This procedure involves stripping the aganglionic rectum of its mucosa and then bringing the normally innervated colon through the rectal muscular cuff, bypassing the abnormal bowel from within. The advantage to this procedure is the preservation of rectal function with minimal risk of injury to the pelvis. The other commonly used procedure is the retrorectal transanal pull-through (Duhamel procedure). In the Duhamel procedure, the normally innervated bowel is brought behind the abnormally innervated rectum approximately 1-2 cm above the pectinate line and an end-to-side anastomosis is performed. A neorectum is created with the anterior half having normal sensory receptors and a posterior half with normal propulsion. The advantages to the Duhamel procedure are that it reduces pelvic dissection to a minimum and retains the sensory pathway of rectal reflexes.
The overall mortality rate for surgical repair is low (approximately 1%). The most common immediate postoperative complications include stricture or leakage at the anastomosis site. Some patients experience recurrent enterocolitis. The widely held view that long-term outcomes of bowel function in Hirschsprung disease are generally favorable have been challenged by recent high-quality studies. Controlled studies in which patient follow-up occurred through adolescence demonstrate a high prevalence of impaired bowel function. Long-term sequelae including fecal soiling or incontinence, constipation, and bowel obstruction occur in up to half of children with Hirschsprung disease following repair. Repeat operations are required in up to one-fourth of cases. Contrast enema findings in children with a poor functional outcome (e.g., soiling, bowel obstruction) include a distal narrowed segment due to stricture or aganglionic/transitional zone segment, dilated or hypomotile distal segment, and thickened presacral space due to compressing Soave cuff.
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