Non-visualization of the Gallbladder on Ultrasound: Magnetic Resonance Cholangiopancreatography (MRCP) Confirmation of Congenital Gallbladder Agenesis.

Gallbladder agenesis is a rare congenital biliary anomaly that may mimic gallbladder pathology both clinically and radiologically. On ultrasound, it may be misinterpreted as a contracted gallbladder or cholelithiasis, potentially leading to diagnostic confusion and unnecessary surgical exploration. We report the case of a 23-year-old female who presented with right upper quadrant abdominal pain and whose initial ultrasound suggested gallstones. Because the gallbladder was not clearly visualized, magnetic resonance cholangiopancreatography (MRCP) was performed for further evaluation. MRCP demonstrated the absence of the gallbladder with otherwise normal biliary anatomy, confirming congenital gallbladder agenesis. The echogenic foci initially interpreted as gallstones were later presumed to represent artifactual echoes or adjacent soft tissue/bowel interfaces rather than true cholelithiasis. The unique contribution of this case lies in highlighting a common diagnostic pitfall in which non-visualization of the gallbladder with false-positive sonographic suspicion of stones may prompt unnecessary operative planning if biliary anatomy is not clarified. This case highlights the diagnostic importance of MRCP when the gallbladder is not visualized on ultrasound and emphasizes its role in avoiding unnecessary surgical intervention in selected equivocal cases.