Background: Gallbladder agenesis is an extremely rare, usually asymptomatic anatomic variation. Enterogastric reflux (EGR) in a patient with gallbladder agenesis was not reported previously. We report a rare case of EGR in a patient with gallbladder agenesis, diagnosed on 99mTc HIDA (hepatobilliary iminodiacetic acid) SPECT-CT (single-photon emission computed tomography-computed tomography) scintigraphy. Case Presentation: A 35-year-old female was referred to Nuclear Medicine Department for Tc99m HIDA scan. She had history of surgical exploration to remove the gallbladder due to suspicion of chronic cholecystitis. But intraoperatively gallbladder was not localized and the patient was referred for Tc99m HIDA scan. Tc99m HIDA scan along with SPECT-CT showed reflux of tracer into the stomach and non-visualized gallbladder. Further imaging by magnetic resonance cholangiopancreatography confirmed the diagnosis of congenital absence of the gallbladder. Conclusion: We conclude that 99mTc HIDA SPECT-CT scintigraphy is helpful in evaluating the true etiology of biliary colic. It should be cautiously reported, mentioning the EGR if present as it may be the true etiology of biliary colic in patients with and without gall bladder. It prevents the added morbidity of surgery, performed with the suspicion of cholecystitis.

Keywords: Gallbladder agenesis, enterogastric reflux, Tc99m HIDA scan, SPECT-CT