Rectal distention testing in patients with irritable bowel syndrome: sensitivity, specificity, and predictive values of pain sensory thresholds.

BACKGROUND & AIMS: Visceral hypersensitivity was detected in patients with functional gastrointestinal disorders and has been proposed as a biological marker of irritable bowel syndrome (IBS). The purpose of this study was to assess the sensitivity, specificity, and the predictive values of pain thresholds evaluated by rectal distention using an electronic barostat in patients with or without IBS and in control subjects.
METHODS: Patients were diagnosed according to Rome II criteria. Rectal sensory thresholds were determined in 164 patients (86 IBS patients, 26 painless constipation, 21 functional dyspepsia, and 31 miscellaneous conditions) and in 25 normal controls. All subjects underwent a series of rectal isobaric distentions using an electronic barostat. The bag was progressively distended from 0 to 48 mm Hg and, in response to distention, subjects reported on discomfort or pain.
RESULTS: Pain thresholds were lower in IBS patients (30.4 +/- 6.7 mm Hg) compared with controls (44.5 +/- 5), painless constipated (45.4 +/- 5.3), functional dyspepsia (39.4 +/- 7.8), and miscellaneous patients (43.2 +/- 5.5). At the level of 40 mm Hg, the sensitivity of the rectal barostat to identify IBS patients from normal subjects and non-IBS patients was 95.5% and its specificity was 71.8%. The positive predictive value was 85.4%. The negative predictive value was 90.2%.
CONCLUSIONS: Lowered rectal pain threshold is a hallmark of IBS patients. Rectal barostat testing is useful to confirm the diagnosis of IBS and to discriminate IBS from other causes of abdominal pain.