Context: Gastrointestinal abnormalities in acromegaly include dolichomegacolon, slow colonic transit and increased prevalence of colonic polyps. Conversely, no data are available on the small intestine.

Objective: To investigate the orocecal transit time (OCTT) and the presence of small intestinal bacterial overgrowth (SIBO).

Patients: 41 acromegalic patients and 30 sex and age matched control subjects entered the study. Acromegalic patients were classified according to the medical treatment with somatostatin analogs as "treated" (n = 22) and "untreated" (n = 19), whereas according to the disease control, as "controlled" (n = 17), "uncontrolled" (n = 10) and "partially controlled" (n = 14). Patients and controls completed a questionnaire and underwent to a standardized 10 g lactulose hydrogen (H₂) breath test (LH-BT) to determine the OCTT and presence of SIBO. SIBO-positive patients underwent to eradication with rifaximine.

Results: An increased prevalence of SIBO (18/41 vs. 1/30, P < 0.0001) and a significantly delayed OCTT (169.53 ± 8.15 vs. 107.25 ± 6.56 min, P < 0.0001) was evidenced in patients compared with controls. No significant statistical differences were found between "treated" or "untreated" patients positive for SIBO, neither between "controlled", "partially controlled" and "uncontrolled" patients. OCTT was significantly delayed in "treated" vs. "untreated" patients (183.21 ± 9.01 and 158.89 ± 6.38 respectively, P = 0.02), and in patients compared with controls (105.75 ± 6.34, P < 0.0001). Rifaximine eradicated SIBO in more than 50% of patients underwent to treatment.

Conclusion: These data demonstrate for the first time that SIBO occurs more frequently in acromegalic patients, however, it can be successfully treated by a specific antibiotic. Medical therapy with somatostatin analogs does not affect SIBO prevalence. OCTT resulted significantly prolonged in both "treated" and "untreated" patients, suggesting that acromegaly determines per se an impairment of the intestinal motility. Indeed, disease control seems irrelevant on the delayed OCTT, suggesting that this alteration might be an irreversible complication of acromegaly, probably related to an autonomic intestinal disorder, as we have previously demonstrated at cardiac level.