Intraluminal renal metastasis from colon cancer simulating a fungus ball.

Reports of renal metastasis from colon cancer are unusual, and none have described intraluminal renal metastasis. We describe a patient with a radiolucent filling defect in the renal pelvis that was discovered by percutaneous nephrostomy during prophylactic nephrostomy tube change. Imaging and laboratory results indicated a fungus ball, but pathologic diagnosis of the percutaneously extracted mass was metastatic colonic adenocarcinoma.