Pneumobilia at Magnetic Resonance Cholangiography: Diagnostic Pitfalls and Solutions

Objective: To assess the diagnostic problem created by pneumobilia at magnetic resonance cholangiography performed in the supine position, and to investigate whether performing the examination in the decubitus position obviates the problem. Patients and Methods: Twelve patients with a history of recurrent pyogenic cholangitis and ultrasound diagnosis of pneumobilia were studied by means of heavily T2-weighted magnetic resonance cholangiography, with the patients lying in the supine and decubitus positions. Results: With magnetic resonance cholangiography performed in the supine position, signal void foci or segments were noted in the common duct in 8 of 12 patients with pneumobilia. There were 2 mimics of ductal calculi and 6 mimics of ductal strictures. Disappearance of the signal void or shifting of the signal void to non-dependent parts of the common duct were apparent with magnetic resonance cholangiography in the decubitus position. Conclusion: Pneumobilia can mimic common duct calculus or stricture at magnetic resonance cholangiography performed in the supine position. Decubitus magnetic resonance cholangiography aids in differentiating pneumobilia from these mimics.