Cause:Unknown, perhaps bowel motility deficits, perhaps psychiatric/stress
Pathophys:Probably a heterogeneous mix of disorders; psychiatric dx's seem to increase reporting of sx but not disease prevalence
10-20% prevalence; female > male; associated w sexual abuse in women; and w other functional gi disorders (Ann IM 1995;123:688); adult onset, almost all before age 50 yr
Sx:Alternating constipation and diarrhea; and/or abdominal pain × 12+ wk, w mucus stools but no blood; bloating and sense of incomplete emptying; in women, irritable bowel or dyspeptic sx are associated w a h/o sexual abuse in over 50% (Ann IM 1991;114:828)
Si:Usually normal exam; no wgt loss, fever or gi bleeding
r/o giardia, IBD, colon cancer, bowel ischemia, impaction, laxative abuse, malabsorption
Lab:
Chem:TSH, chemistry profile
Endo:EGD, colonoscopy
Hem:CBC, ESR
Stool:Commercial screens to r/o laxative abuse; O+P; Sudan stain for fat; leukocytes
Rx:
(Am J Gastroenterol 2002;97:S7-26)
Bran or other bulking agents, Al(OH)3 antacids; psychiatric care (GE 1991;100:450); antibiotics to alter bowel flora: neomycin, tetracycline, rifaximin (Ann IM 2006;145:557 vs 626); or probiotics to do the same, like lactobacillus? (no evidence basis, ACP J Club 2010;153(3):7)
if predominantly diarrhea present: low-dose tricylic antidepressants; loperamide (Imodium) 2-4 mg po qid or diphenoxylate (Lomotil). If sx still persist, get giardia antigen on stool and consider bile salt binding. Perhaps alosetron (Lotronex) 1 mg po bid (Med Let 2002;44:67; 2000;42:53), pulled from mkt in 2000 due to ischemic colitis but back at lower doses for severe cases, 1 mg po qd-bid w special monitoring;
if predominantly constipation: SSRIs, if pain: antispasmodics like dicyclomine (Bentyl) 10-20 mg po t-qid; Donnatal tid-qid
? rifaximin (Nejm 2011;364:22, 81)