Overflow diarrhea

Fecal impaction is a sequela of long term constipation, whereby a hard fecal mass in the rectum prevents defecation from occurring. The resultant rectal dilatation leads to smooth muscle relaxation of the internal anal sphincter. Concurrently the obstructing stool mass leads to increased secretions in the upstream colon. This combination of secretions and particulate/fluid stool matter seeps around the rectal feces. This may be reported by the patient as diarrhea, for which the clinicians may apply the misnomer overflow diarrhea.