The pathophysiology of faecal spotting in obese subjects during treatment with orlistat.
BACKGROUND
The intermittent loss of oil or liquid faeces ('spotting') is an adverse effect that occurs in obese patients during treatment with the lipase inhibitor orlistat; the pathophysiology is unknown.


OBJECTIVE
To investigate the effects of orlistat on anorectal sensorimotor function and continence.


METHODS
Obese subjects susceptible to spotting were identified by an unblind trial of orlistat. Obese spotters (n = 15) and non-spotters (n = 16) completed a randomized, double-blind, cross-over trial of orlistat and placebo. Anorectal function was assessed by rectal barostat and anal manometry, together with a novel stool substitute retention test, a quantitative measurement of faecal continence.


RESULTS
Orlistat increased stool volume and raised faecal fat and water. Treatment had no effect on anorectal motor function, but rectal sensation was reduced; on retention testing, the volume retained was increased. Subjects susceptible to spotting had lower rectal compliance, heightened rectal sensitivity and weaker resting sphincter pressure than non-spotters. On retention testing, gross continence was maintained; however, spotters lost small volumes of rectal contents during rectal filling.


CONCLUSIONS
Treatment with orlistat has no direct adverse effects on anorectal function or continence. Spotting occurs during treatment with orlistat when patients with sub-clinical anorectal dysfunction are exposed to increased stool volume and altered stool composition.
Department of Gastroenterology and Hepatology, University Hospital of Zürich, Zürich, Switzerland Menne Biomed, Tübingen, Germany.
M
M
Fox
M
M
Thumshirn
D
D
Menne
B
B
Stutz
M
M
Fried
W
W
Schwizer
D000328:Adult; D019440:Anti-Obesity Agents / Q000009:adverse effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005242:Fecal Incontinence / Q000139:chemically induced* / Q000503:physiopathology; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D007783:Lactones / Q000009:adverse effects*; D008297:Male; D008365:Manometry / Q000379:methods; D008499:Medical Records; D008875:Middle Aged; D009765:Obesity / Q000188:drug therapy*; D000077403:Orlistat; D011446:Prospective Studies; D015203:Reproducibility of Results
D019440:Anti-Obesity Agents; D007783:Lactones; D000077403:Orlistat