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

Objectives: 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. Methods: 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. Results: 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). Conclusions: 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.