Spot the diagnosis in the following IVU

Note the ectopic kidney seen in the pelvis on left side above the urinary bladder. This patient had solitary right kidney, which was normal in position. Ectopic kidneys are found in one in 1000 people, usually on the left near the pelvic brim. The other kidney is generally normal. A diseased ectopic kidney may present diagnostic problems and may be mistakenly excised as an unexplained pelvic mass.