Small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome: Frequency and predictors

Objective and Background: Small intestinal bacterial overgrowth (SIBO) has been implicated in pathogenesis of IBS. We aimed to study frequency and predictors of SIBO in patients with IBS. Methodology: We included 59 consecutive patients of IBS & 37 healthy controls (HC). Evaluation for SIBO was done by glucose breath test (GBT) using 100 gm of glucose after an overnight fast. Breath hydrogen & methane concentration were noted at baseline & every 15 min after administration of glucose for a total of 3 h. Persistent rise in breath hydrogen or methane > 12 ppm above basal was considered diagnostic of SIBO. Results: Of 59 patients, 27 were diarrhoea predominant (D-IBS), 11 were constipation predominant (C-IBS) and 21 were mixed type (M-IBS). Median age of patients (34 [18-47] years) were comparable to controls (35 [20-48] years) (P = 0.21). Patient group was similar to HC in gender distribution (male 41/59 [69.5%] vs 25/37 [67.6%], P = 0.36). SIBO was more frequent in patients with IBS than HC (14/59 [23.7%] vs 1/37 [2.7%], P = 0.008). Patients with D-IBS more often had SIBO as compared to non-D-IBS (10/27 [37%] vs 4/32 [12.5%], P = 0.02). C-IBS had lowest frequency of SIBO (1/11 [9%]) among all IBS subgroups. Patients with history of bloating more often had SIBO as compared to those without this symptom (11/23 [47.8%] vs 3/36 [8.3%], P = 0.002). Among IBS patients, females more often had SIBO as compared to males (8/18 [44.4%] vs 6/41 [14.6%], P = 0.01). Conclusions: SIBO was more frequent in patients with IBS as compared to healthy controls. D-IBS subtype, female gender & bloating were predictors of SIBO in patients with IBS.