Congenital absence of ganglion cells in distal bowel, beginning at the internal sphincter and extending proximally.  Fails to relax, hence functional obstruction.  Mostly present as neonates, with delayed meconium and abdo distension, else mostly under 2yr with intractable constipation, failure to thrive, repeated vomiting. Rarely soiling! 1/3 of these later presenting patients present with enterocolitis, with fever, shock, bloody stools.  Probably due to abnormal colonic mucosa, a problem that seems to persist even after surgery.

Some series describe patients without symptoms in neonatal/infancy period!

1 in 5000 births. 4:1 males:females.  FH 30%. Assoc with downs, cong deafness.

Empty rectum on AXR (ie gas pattern disappears)! [insert axr] May be forceful expulsion at PR (which may also spoil diagnostic value of barium or manometry studies). Barium enema can be useful but high false neg in first 3/12, and need to avoid PR examination and enemas for preceding 48hr else distal narrowing lost.

Treatment – resection of affected segment.  Postop do well, risk of anal hypertonicity (enterocoitis), stricture.