Pancreatic pseudocysts presenting as thick-walled renal and perinephric cysts

Posterior extension of a pancreatic pseudocyst should be considered in the differential diagnosis of a thick-walled renal or perinephric cyst seen on infusion pyelography with tomography. Opacification of the wall of a pancreatic pseudocyst by this technique has not been reported previously and lack of knowledge of this possibility can lead to mistaken diagnosis and the possibility of an unnecessary exploratory operation, particularly when angiography is inconclusive and a gastrointestinal series is negative or equivocal. The mechanism of opacification of the wall of a pancreatic pseudocyst is discussed. Parasitization of the renal capsular arteries by a pancreatic pseudocyst can further compound the difficulty of diagnosis.