Short-Term Efficacy and Safety of Elobixibat for Chronic Constipation Assessed by Rectal Ultrasonography: A Retrospective Observational Study

<b>Background/Objectives:</b> Ultrasonography (US) is a non-invasive and repeatable examination for evaluating chronic constipation. However, few studies have explored treatment decisions based on rectal US findings. To date, the efficacy and safety of elobixibat have not been evaluated using rectal US classification in patients with chronic constipation. This study aimed to evaluate the short-term efficacy and safety of elobixibat in patients with chronic constipation classified as "no fecal retention" by rectal US. <b>Methods:</b> We retrospectively analyzed 32 patients with chronic constipation who underwent rectal US and received elobixibat (10 mg/day) between May 2019 and December 2024. Rectal US findings classified patients into four groups: no fecal retention, fecal retention without hard stools, fecal retention with hard stools, and gas retention. The primary endpoint was the response rate of spontaneous bowel movements (SBMs) within 3 days after starting elobixibat in the "no fecal retention" group. <b>Results:</b> Among 18 patients in the "no fecal retention" group, 94.4% achieved SBMs within 3 days, indicating a favorable short-term response. Adverse events included abdominal distension and abdominal pain, each observed in one patient (3.1%). <b>Conclusions:</b> Elobixibat was effective and well tolerated in patients with chronic constipation classified by rectal US findings.