The association between a positive lactulose methane breath test and rectocele in constipated patients

Rectocele with constipation might be related to methane (CH4) producing intestinal bacteria. We investigated the breath CH4 levels and the clinical characteristics of colorectal motility in constipated patients with rectocele.

A database of consecutive female outpatients was reviewed for the evaluation of constipation according to the Rome III criteria. The patients underwent the lactulose CH4 breath test (LMBT), colon marker study, anorectal manometry, defecography and bowel symptom questionnaire. The profiles of the lactulose breath test (LBT) in 33 patients with rectocele (with size ≥ 2 cm) and 26 patients with functional constipation (FC) were compared with the breath test results of 30 healthy control subjects.

The mean size of rectocele was 3.52 ± 1.06 cm. The rate of a positive LMBT (LMBT+) was significantly higher in patients with rectocele (33.3%) than in those with FC (23.1%) or healthy controls (6.7%) (p = 0.04). Breath CH4 concentration was positively correlated with rectosigmoid colon transit time in rectocele patients (γ = 0.481, p < 0.01). A maximum high pressure zone pressure > 155 mmHg was a significant independent factor of LMBT+ in rectocele patients (OR = 8.93, 95% CI = 1.14-71.4, p = 0.04).

LMBT+ might be expected in constipated patients with rectocele. Moreover, increased rectosigmoid colonic transit or high anorectal pressure might be associated with CH4 breath levels. Breath CH4 could be an important therapeutic target for managing constipated patients with rectocele.