Retained stool as a guide to the site of severe rectal bleeding.

Despite improvements in diagnostic techniques including the use of radionuclide imaging, locating the site of severe rectal bleeding is not always possible. We present two patients in whom a survey film of the abdomen showed a dense accumulation of stool in the transverse colon. Subsequent evaluation confirmed that the source of rectal bleeding was distal to this area. Accordingly, the presence of a fecal impaction in the colon strongly suggests that the site of active bleeding lies more distally. In these circumstances, diagnostic measures should be directed to the segment of the colon distal to the impaction.