This is a patient who presented with progressively worsening left flank pain. The patient had a nephroureteral stent placed at an outisde hospital for hydroureteronephrosis. A frontal radiograph of the abdomen and pelvis was obtained which demonstrates the stent in place. In addition, the left kidney has a calcification extending from the renal collecting system into the renal pelvis consistent with staghorn calculus formation. The red arrow on the coronal CT image demonstrates the staghorn calculus. The green arrows demonstrate an abnormally enlarged and hypodense appearance of the renal medulla. This patient has a chronic condition known as xanthogranulomatous pyelonephritis. This is a rare form of chronic pyelonephritis which eventually results in a non-functioning kidney.