A 22-year-old man presents with worsening colicky abdominal pain and abdominal distension for one week. His last bowel movement was one day ago. His medical history is only significant for chronic constipation from childhood, which was self-medicated with over-the-counter laxatives. The constipation was never evaluated by a medical professional. His surgical and family histories are unremarkable. He has no known allergies. He only drinks socially, does not smoke, and aside from temporarily experimenting with marijuana a couple of years ago, has not used recreational drugs. He is currently an undergraduate at a nearby university. Examination reveals marked abdominal distention, mild generalized abdominal tenderness, hyperactive bowel sounds, and a high rectal fecal load. An erect x-ray of the abdomen shows the distal large bowel to be markedly distended and filled with feces. No air-fluid level is apparent. Subsequently, he is kept nil per oral, a nasogastric (NG) tube is inserted, and IV fluid resuscitation is commenced. The rectum is evacuated manually. A complete blood count, serum electrolyte assay (including calcium levels), renal profile, liver profile, thyroid profile, and random plasma glucose are all found to be within normal parameters.
The descending colon and sigmoid colon are markedly dilated and full of fecal matter. The small bowel appears normal.
You realize that a colonoscopy is not indicated here.
The rectoanal inhibitory reflex is found to be absent.
Multiple rectal biopsy specimens are obtained. All are aganglionic.