The Role Of Breath Testing In Microscopic Colitis

INTRODUCTION: Microscopic colitis (MC) is a diarrheal illness difficult to differentiate from other gastrointestinal disorders. Historical cues and understanding of disease prevalence are critical to the evaluation of MC patients experiencing continued symptoms despite adequate treatment or histologic improvement. This study examines the prevalence of concomitant small intestine bacterial overgrowth (SIBO) and carbohydrate malabsorption in a MC population. METHODS: Records were reviewed from 6/2015 to 6/2020 at a single-center private gastroenterology practice. Patients with MC were identified by ICD10 codes and grouped into either collagenous (CC) (K52.831), lymphocytic (LC) (K52.832), or other microscopic colitis (K52.839). Patient demographics, surgical history, disease activity, medications, fecal calprotectin, date of initial diagnosis, and breath testing results were recorded in a HIPAA compliant dataset. Data were analyzed using chi-squared, Fisher’s exact, Pearson correlation, and T testing where indicated. RESULTS: 223 MC patients were reviewed with 67 included based on the presence of SIBO hydrogen (H2) breath testing: 50 with LC, 10 with CC, 4 with CC and MC, and 3 indeterminate. The average age at MC diagnosis was 64.9 ± 14.6, with a higher prevalence of females (73.1%) and whites (78.9%). SIBO positive rates were 19/54 (35.2%) in the LC group and 5/14 (35.7%) in the CC group (P = 0.97) (Figure 1). There was no difference in SIBO positivity between age groups (< 70 vs > 70, P = 0.82), genders (P = 0.33), or ethnicities (P = 0.35). SIBO rates in patients with active MC (defined as > 3 watery bowel movements daily) did not differ from patients in remission (30.6% vs 28.6%, P = 0.89). The average fecal calprotectin (FC) in the SIBO positive group was 84.4 mg/mg, compared to 262.6 mg/mg in the SIBO negative group (P = 0.31) (Figure 2). Concurrent carbohydrate malabsorption was observed in 47.4% of SIBO positive patients, compared to 61.1% in the SIBO negative group (P = 0.33) (Figure 3). CONCLUSION: This retrospective cross sectional study illustrates rates of SIBO positivity in the MC population are similar to symptomatic patients in the general population (Figure 1). There was no difference in positive rates between the LC and CC groups, limited by a small CC sample size. Furthermore, carbohydrate malabsorption was frequently superimposed on the MC diagnosis, highlighting the need to consider H2 breath testing for both SIBO and carbohydrate malabsorption in symptomatic MC patients who are unresponsive to therapy.Figure 1.: Similar rates of SIBO positivity were observed between collagenous and lymphocytic colitis (35.2% vs 35.7%, P = 0.97). Rates of bacterial overgrowth in the general population are estimated 2-22%, though our study’s rates of positive SIBO breath testing correlate with rates from a Vizuete et al, which found SIBO positivity in 32.9% of patients with “flatulence, eructation, and gas pain”. No statistical difference in SIBO positivity was seen between age groups (39.1% (< 70) vs 36.4% (> 70), P = 0.82), genders (27.8% (M) vs 40.8% (F), P = 0.33), or ethnicities (43.3% (white) vs 25.0% (non-white), P = 0.35).Figure 2.: There was no difference in SIBO positive rates between patients with active microscopic colitis (described as at least 3 bowel movements per day) versus patients in remission (30.6% vs 28.6%, P = 0.89). When comparing SIBO positive to negative patients, there was no difference in the percentage of patients on steroid therapy at the time of breath testing (12.0 vs 14.3%, P = 0.79).Figure 3.: Carbohydrate malabsorption was frequently observed in all tested patients (56.4%). Positive rates of fructose/lactose/sucrose intolerance were observed more frequently in the SIBO negative group (47.4% vs 61.1%, P = 0.33). There was no observed difference between collagenous colitis patients (CC) and lymphocytic colitis patients (LC) with regard to rates of individual carbohydrate malabsorption.