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Diagnosis Please |
1 From the Department of Radiology, Medical College of Virginia of Virginia Commonwealth University, 401 N 12th St, Rm 3-415, Richmond, VA 23298. Received September 14, 1998; revision requested October 22; final revision received March 18, 1999; accepted April 8. Address correspondence to L.D.N. (e-mail: ldnarla@hsc.vcu.edu).
Index terms: Colon, aganglionosis, 75.145 • Colon, stenosis or obstruction, 75.143 • Diagnosis Please • Infants, newborn, gastrointestinal tract, 75.145 • Radiography, in infants and children, 75.1281, 75.1283
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Initial rectal biopsy results showed no ganglion cells, which is consistent with Hirschsprung disease. At the time of surgery for ostomy placement, results of biopsy of the rectum, sigmoid colon, hepatic flexure, appendix, and terminal ileum showed no ganglion cells (Fig 4). Ganglion cells were demonstrated in the ileum 15 cm from the ileocecal valve. Appendectomy and loop ileostomy were performed.
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Since this patient was 9 days old, the diagnoses of imperforate anus and small-bowel atresia were not considered. Diagnosis of imperforate anus is made by means of physical examination, with diagnostic work-up performed to determine high or low type and any associated genitourinary anomalies. Contrast material–enhanced enema examination and clinical information are used to attempt to differentiate the remaining entities.
Evaluation of the caliber of the colon is essential in attempting to elucidate the cause of low intestinal obstruction. A microcolon shows a very small caliber, generally less than 1 cm in diameter, owing to disuse of the colon from a more proximal obstruction. Microcolon is seen in patients with meconium ileus; distal jejunal, ileal, or proximal colonic atresia; and megacystis-microcolon-intestinal hypoperistalsis syndrome. It is seen in less than one-fourth of patients with total colonic Hirschsprung disease (1). Results of examination with contrast material that show a narrow descending colon with a marked change of caliber at the splenic flexure can be seen with syndromes of neonatal functional immaturity of the large bowel (small left colon syndrome and meconium plug syndrome) or in long-segment Hirschsprung disease.
For diagnostic enema results in newborns, a relatively dilute ionic, water-soluble contrast material, such as iothalamate meglumine (Cysto-Conray [400 mOsm/kg water]; Mallinckrodt, St Louis, Mo), or a low-osmolal, nonionic, water-soluble contrast material, such as iohexol (Omnipaque [411 mOsm/kg water]; Nycomed Amersham), can be used. In neonates, water-soluble contrast materials are preferable to barium because, although it is rare, perforation due to the obstruction may not be depicted at conventional radiography and because contrast material may spill into the peritoneal cavity. Infants with either functional immaturity of the colon or meconium ileus, especially the latter, benefit from enemas with water-soluble contrast material: Therapy thus begins immediately, with the diagnostic study. There has been greater success in reducing meconium ileus by using water-soluble contrast material for the initial diagnostic enema rather than barium.
Passage of meconium after the enema does not preclude the diagnosis of Hirschsprung disease. In equivocal cases, or if persistent problems with passing stool occur, Hirschsprung disease should be considered, and rectal biopsy is indicated. Rectal biopsy is performed at the bedside, and a deep transrectal specimen to include myenteric plexus is obtained.
Hirschsprung disease is a common cause of all neonatal bowel obstruction and accounts for one-third of all cases. The incidence of Hirschsprung disease is one per 5,000 livebirths per year and increases to 3.6% in families with one affected male member and to 8.0% with one affected female member (2). Hirschsprung disease occurs three or four times more often in boys than in girls and, for unknown reasons, is rare in premature infants. In the uncommon total colonic variant, the prevalence in boys and girls is nearly equal, with a strong hereditary tendency. Patients present in the neonatal period 80% of the time, with presenting symptoms including delay in passage of meconium, abdominal distention, constipation, and bilious vomiting (3).
Twenty percent of patients have associated abnormalities, including Down syndrome (8%), cardiac defects (8%), genitourinary abnormalities (6%), and gastrointestinal anomalies (4%). Gastrointestinal anomalies can include colonic atresia, imperforate anus, and neurocristopathy. Neurocristopathies can occur singularly or in combination with neurocristopathic syndromes such as neuroblastoma; pheochromocytoma; neurofibromatosis; Waardenburg syndrome; multiple endocrine neoplasia, type 2; and congenital central hypoventilation syndrome, also known as Ondine curse (4).
The histopathologic criterion for diagnosis of Hirschsprung disease is absence of the ganglion cells of the myenteric plexus; this results in a narrowed aganglionic segment with a dilated segment proximal to this distal obstruction. The myenteric ganglion cells arise from the neural crest and migrate cephalocaudally along the vagal trunks through the intestines. An early arrest in the migration between the 7th and 12th weeks of gestation leads to Hirschsprung disease and can affect a variable length of the colon and the small bowel (5,6).
The transition zone from abnormal to normal ganglionic bowel is found in the rectosigmoid or sigmoid colon in 65% of patients, the descending colon in 14%, the rectum in 8%, and the more proximal large bowel in 10% (7). Aganglionosis affecting the small bowel is rare and occurs in approximately 3% of patients (7). Ultrashort Hirschsprung disease cannot be identified at contrast-enhanced enema examination, and it is defined by the presence of ganglion cells in rectal biopsy results, as well as failure of the internal sphincter to relax at rectal manometry (anorectal achalasia). Resolution of chronic constipation was noted in all patients after internal sphincter myomectomy (8).
Another histopathologic finding in Hirschsprung disease is increased number and size of nerve fibers within the lamina propria, muscularis mucosae, and subjacent submucosa at acetylcholinesterase staining.
In one series of 168 patients with Hirschsprung disease treated during 1974–1992, enterocolitis occurred in 34% preoperatively and in 8% postoperatively. In 5%, it occurred pre- and postoperatively (9). With small-bowel involvement (10), overall mortality has been as high as 33%. A reduced turnover of mucins, as shown by incorporation of radioactive precursors, will give rise to a defective colonic mucous defensive barrier. The lower the turnover, the more likely a patient is to develop postoperative enterocolitis. It is therefore possible that organ culture with radioactive mucin precursors of the proximal ganglionated mucosa performed at the time of the pull-through procedure has a predictive value in the development of postoperative enterocolitis (11). Enema is contraindicated in patients with signs of perforation on abdominal radiographs or signs of fulminant enterocolitis.
Another well-documented complication of Hirschsprung disease, which occurs in 4% of patients, is perforation of the bowel (12). This most commonly involves the proximal colon (68%), the appendix (17%), or the distal small bowel (6%). This complication is most commonly associated (62%) with total aganglionosis and generally occurs by 4 months of age. At the time of perforation, the neonate may have no other symptoms relating to aganglionosis, and thus the true diagnosis may not be considered. Therefore, unexplained perforation of the colon, appendix, or small bowel is another indication for biopsy to exclude Hirschsprung disease (13).
The child should not have any bowel preparation prior to contrast-enhanced enema examination, as it may interfere with demonstration of the transition zone. A rectal examination is also best avoided, although there is some evidence that it does not affect diagnostic accuracy. The enema examination is begun with the patient in the lateral position; a soft catheter should be taped in place; balloon inflation should not be used (7). The colon should be filled gradually to identify a transition zone, which is seen in approximately 80% of patients with Hirschsprung disease (2). Once the transition zone is delineated, the examination is stopped without filling the rest of the colon. Delayed radiographs may be helpful to evaluate evacuation of contrast material from the bowel; delayed radiographs may also demonstrate a transition zone not appreciated on the initial radiographs.
Radiographic findings that can be seen at contrast-enhanced enema examination in Hirschsprung disease include a transition zone, a rectosigmoid caliber ratio less than 1, denervation hyperspasticity (narrowing) of the distal segment with a sawtooth configuration due to muscular contractions (14,15), microcolon, delayed or disordered evacuation of the contrast material from the colon, and bowel shortening. Work hypertrophy of the colon may be seen in children older than 3 months, as the proximal colon develops hypertrophy of the circular and longitudinal muscle fibers in response to the obstruction of the aganglionic segment. Meconium plugs coexist in 10%–30% of cases (2,16). Frequently, a meconium plug is assumed to be the sole cause of a neonatal obstruction, and the diagnosis of concurrent Hirschsprung disease can be missed; these patients need close clinical follow-up and possibly delayed radiographs.
Diverting colostomy is traditionally the initial treatment, with the site determined by means of the documentation of ganglion cells at the time of surgery. At a later date, a pull-through procedure (Duhamel, Soave, or Swenson) is performed. Frequently now, instead of a two-step procedure, the primary pull-through procedure is performed during the newborn period. Laparoscopic pull-through procedures recently have been performed (17). The laparoscopic port releases the colonic attachments, ligates vessels, and allows caudal mobilization with removal of the aganglionic segment of the colon, which brings the normal bowel through the pelvic floor and anastomoses the bowel to the anorectal verge. Advantages of the laparoscopic approach include shorter hospital stay, fewer complications from disruption of skin integrity, and good results.
Hirschsprung disease is a common and treatable cause of neonatal low-bowel obstruction; contrast-enhanced enema examination is the initial examination of choice. In addition to the typical presentations, persistent small-bowel dilatation or unexplained perforation of the distal small bowel, colon, or appendix warrants performing biopsy to exclude Hirschsprung disease.
Our congratulations to the 46 individuals who submitted the most likely diagnosis (total colonic aganglionosis—long-segment Hirschsprung disease) for Diagnosis Please, Case 22. Credit was given for Hirschsprung disease only if "long-segment" or "total aganglionosis" was mentioned. The names and locations of the individuals, as submitted, are as follows:
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