May Be Caused by

 Common

Acute pyelonephritis

Arterial branch occlusion

Autosomal dominant polycystic kidney disease

Cyst

Infarction

Renal cell carcinoma

Renal contusion

Renal laceration

Renal sinus lipomatosis

Sarcoma

Transitional cell carcinoma

Trauma

Wilms tumor

 Uncommon

Abscess

Angiomyolipoma

Arteriovenous malformation

Intrarenal hematoma

Localized hydronephrosis

Lymphoma

Medullary cystic kidney disease

Metastasis

Renal artery aneurysm

Tuberculosis

Xanthogranulomatous pyelonephritis