Internal Medicine

0521779407-C03 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 20:54

Constipation and Fecal Impaction 395

➣Normal colonic transit (usually IBS): all markers absent

➣Colonic inertia: slowpassage of radiopaque markers through the

proximal colon; several markers present throughout the colon;

dysfunction in the myenteric nerve plexus

➣Outlet delay, in which markers move normally through the

colon but stagnate in the rectum; markers present in the

pelvis; Hirschsprung’s disease, fecal impaction, and in abnormal

responses of the pelvic floor muscles during defecation (pelvic

floor dyssynergia)

■Flexible sigmoidoscopy or colonoscopy: imperative to exclude

colonic obstruction

■Barium enema: less costly than colonoscopy but useful in detecting

structural causes of constipation, and for the diagnosis of mega-

colon, megarectum and diverticulosis

Other Tests

■Anorectal motility study for evaluation of rectal sensation and com-

pliance, reflexive relaxation of the internal anal sphincter, and

balloon expulsion (pseudodefecation). EMG studies of the exter-

nal sphincter and puborectalis muscles using needle or surface-

electrodes may also be useful

■Defecography with fluoroscopic monitoring of evacuation of thick-

ened barium; particularly useful in cases of pelvic floor dys-

synergia

differential diagnosis

■Colonic obstruction by anal, rectal or colonic tumor

management

What to Do First

■Exclude malignancy, usually colonic, as a cause of constipation Dis-

continue offending drug(s)

General Measures

■Treat hypothyroidism, diabetes and metabolic or electrolyte abnor-

malities if present

specific therapy

Indications

■Chronic constipation that compromises quality of life and predis-

poses to hemorrhoidal bleeding, fecal impaction, or acute colonic

pseudoobstruction requires aggressive, chronic therapy. Patients