LAUSR

Simple renal cysts are commonly observed and asymptomatic in the majority of patients. These cysts are usually located peripherally and are unnoticed unless they grow large enough to cause pain by impinging on the kidney.1 In contrast to the simple cyst, the peripelvic renal cyst is contiguous to the renal pelvis and infrequently observed.1 Often peripelvic cysts either stem from an embryologic vestige or result from a lymphatic obstruction.2 Rarely do peripelvic cysts cause ureteropelvic junction obstruction (UPJO). UPJO most commonly occurs in childhood and adolescence. Most common causes include intrinsic stenosis, an abnormal insertion point of the ureter, or compression of the ureter by a crossing vessel.3 In the case presented, a peripelvic cyst was found to be compressing the UPJ, causing an obstruction. Due to the unusual nature of the peripelvic cyst and the resultant obstruction, we chose to report this case.