May Be Caused by

 Common

Hydronephrosis

Obstruction of infundibulum

Pyelonephritis

Renal papillary necrosis

Tuberculosis

Vesicopelvic reflux

Xanthogranulomatous pyelonephritis

 Uncommon

Abscess

Fungal disease

Neoplasm of kidney

Postoperative scarring

Transitional cell carcinoma