Gallbladder contraction at CT and sonography secondary to bowel preparation for colonoscopy

To investigate volume changes of the gallbladder at computed tomography (CT) following bowel preparation for colonoscopy and to evaluate the incidence of gallbladder contraction at abdominal sonography performed with colonoscopy on the same day.

During a 1-year period, 222 patients underwent abdominal CT (CT₁) and colonoscopy on the same day. Among them, 123 patients had prior CT imaging without receiving colonoscopy in the past were enrolled. Manual estimates of 3D gallbladder volume were obtained from two CT scans to evaluate whether gallbladder volume changed as a result of bowel preparation for colonoscopy. During the same 1-year period, another 89 patients underwent abdominal sonography and colonoscopy on the same day (sonography group). The short-axis diameters of the gallbladder on the longitudinal scan of sonography from these patients were obtained.

Gallbladder volume was significantly larger on prior CT without colonoscopy (31.7 ± 15.4 cm³) than on CT₁ (20.3 ± 11.1 cm³) (p < 0.001). Gallbladder volume decreased by more than 50% in 41 of 123 patients (33%) who underwent abdominal CT and colonoscopy on the same day, compared with standard CT. In the sonography group (n = 89), the short-axis diameters of the gallbladder were less than 1.5 cm in 41 patients (46%) and less than 1.0 cm in 17 patients (19%).

Contracted gallbladder secondary to bowel preparation can be seen on imaging when performed with same-day colonoscopy. Such a situation may lead to the incomplete or inadequate evaluation of the gallbladder on imaging with same-day colonoscopy.