Hirschsprung's Pull-Through

Hirschsprung's disease is a congenital absence of ganglion cells in the distal bowel, resulting in a functional obstruction at the aganglionic segment. The aganglionic segment always begins at the internal anal sphincter and extends proximally for a variable distance — most commonly limited to the rectosigmoid (short-segment disease, ~80%) but occasionally extending to involve the entire colon (long-segment) or even the small bowel (total intestinal aganglionosis).

Presentation is typically in the newborn period with failure to pass meconium in the first 48 hours, abdominal distension, and bilious emesis. Older infants and children may present with chronic constipation, failure to thrive, or Hirschsprung-associated enterocolitis — a potentially life-threatening inflammatory complication characterized by explosive diarrhea, fever, and sepsis.

Contrast enema is the standard initial study and shows a transition zone — a caliber change between the narrowed aganglionic distal segment and the dilated ganglionated proximal bowel. Definitive diagnosis requires histologic confirmation: suction rectal biopsy (in infants) or full-thickness rectal biopsy (in older children) demonstrating absence of ganglion cells and hypertrophied nerve trunks. Acetylcholinesterase staining and calretinin immunohistochemistry are confirmatory.

The transition zone seen on contrast enema does not always correspond exactly to the histologic transition zone — intraoperative leveling biopsies (seromuscular biopsies at sequential proximal levels) are routinely performed at the time of definitive surgery to confirm the location of normally ganglionated bowel before the pull-through.

The Swenson procedure is a true rectosigmoidectomy: the aganglionic distal bowel is resected down to the level of the anal canal, and the normally ganglionated proximal bowel is anastomosed to the anus. Technical demand is high because dissection must hug the rectum to avoid injury to the pelvic nerves.

The Duhamel procedure leaves the aganglionic rectum in place and pulls normal ganglionated bowel down behind it, creating a side-to-side anastomosis between the posterior wall of the native rectum and the pulled-through bowel. The advantage is preservation of the anterior rectal wall (with its sensation and reflexes); the disadvantage is the potential for a stagnant fecaloma in the residual rectal pouch.

The Soave procedure is an endorectal pull-through: the mucosa and submucosa of the distal aganglionic rectum are stripped away, leaving a muscular cuff, and the normally ganglionated bowel is pulled through this cuff and anastomosed to the dentate line. The endorectal cuff protects against pelvic nerve injury but can constrict if it scars down.

All three operations work; outcomes are broadly comparable in experienced hands. The choice is surgeon-dependent and increasingly is performed via a transanal approach (transanal endorectal pull-through, TEPT), eliminating the need for laparotomy in short-segment disease.

TEPT has become the standard approach for short-segment Hirschsprung's. The operation is performed entirely from below: the rectal mucosa is incised circumferentially at or above the dentate line, the mucosa and submucosa are dissected free from the muscular cuff up to the peritoneal reflection, and the rectum is then everted and prolapsed through the anus. The bowel is divided at the level of normally ganglionated tissue (confirmed by frozen section), and a hand-sewn coloanal anastomosis completes the pull-through.

For longer aganglionic segments or when transanal exposure is inadequate, the procedure is converted to a combined transanal-laparoscopic or transanal-open approach to permit proximal mobilization.

Anal dilations are typically begun 2–3 weeks postoperatively and continued for several months to prevent anastomotic stricture. Long-term concerns include enterocolitis (which can occur even after a technically perfect pull-through and remains the leading cause of postoperative mortality), constipation, and incontinence.

Enterocolitis presents with fever, abdominal distension, and explosive foul-smelling diarrhea. Treatment is prompt: nasogastric decompression, IV fluids, broad-spectrum antibiotics (typically including metronidazole), and rectal irrigations. Recurrent episodes require evaluation for residual aganglionic segment, anastomotic stricture, or motility disorder of the pulled-through bowel.

Operative complications include anastomotic leak, anastomotic stricture, retraction, and injury to pelvic nerves with subsequent bladder or sexual dysfunction. Long-term complications include incontinence (particularly with Swenson), residual aganglionosis from inadequate leveling biopsies, recurrent enterocolitis, and chronic constipation.

Examiners commonly probe how you would handle the child who presents with enterocolitis after pull-through, the workup of postoperative obstruction, and the decision between transanal versus combined approaches. The most important error to avoid intraoperatively is failing to confirm normally ganglionated bowel by frozen section before completing the pull-through — pulling aganglionic bowel through fails and requires reoperation.