Hirschsprung pathophysiology and surgical principles: congenital absence of ganglion cells in distal bowel (rectum ± sigmoid; long-segment 20%, total colonic 5%) causes functional obstruction. Definitive surgical procedures - 1) Soave (endorectal pull-through with mucosal stripping); 2) Swenson (full-thickness rectal resection); 3) Duhamel (retrorectal pull-through with side-to-side anastomosis); 4) Transanal endorectal pull-through (TEPT) - most common modern approach, no abdominal incision in select cases. Postoperative pathophysiology of defecation issues - persistent aganglionosis (residual aganglionic segment), transition zone pull-through, internal anal sphincter (IAS) achalasia, dysmotility of remaining colon, postoperative stricture, twist of pull-through.
Postoperative complications and evaluation: 1) Constipation/obstructive symptoms (30-50%) - causes include IAS spasm, residual aganglionosis, anastomotic stricture, retained transition zone, dysmotility; 2) Soiling/fecal incontinence (15-30%) - causes include sphincter injury, abnormal sensation, overflow constipation; 3) HAEC (10-30% lifetime risk; potentially fatal) - explosive diarrhea, fever, sepsis; treat with rectal irrigations, IV fluids, broad-spectrum antibiotics including metronidazole, NPO; 4) Anastomotic stricture - especially after Soave; manage with dilation. Systematic workup - 1) anorectal examination (sphincter tone, anastomotic stricture, prolapse); 2) contrast enema (transition zone, dilation, twist); 3) anorectal manometry (RAIR loss confirms IAS achalasia); 4) full-thickness rectal biopsy (if residual aganglionosis suspected); 5) colonic transit study; 6) MRI in complex cases.
Treatment algorithm by problem: 1) IAS achalasia - botulinum toxin injection (50-100 units transanal at 4 quadrants of internal sphincter, repeat q3-6mo) or internal sphincter myectomy (posterior strip excision); 2) Anastomotic stricture - serial dilation, dilation under anesthesia, rarely revision; 3) Residual aganglionosis - confirm with biopsy → redo pull-through; 4) Functional constipation - osmotic laxatives (PEG), stimulant laxatives, dietary fiber, behavioral therapy, antegrade enema (Malone) in refractory cases; 5) Soiling - bowel management program (daily enema, MACE), pelvic floor biofeedback, dietary modification; 6) HAEC prevention - long-term metronidazole prophylaxis in recurrent cases, education on early symptom recognition, ileostomy in severe cases. Outcomes - majority achieve social continence by age 10-12 with structured management, but ~10-15% require permanent stoma.