**2.1.1 Extrinsic causes**

Extrinsic causes of urinary tract obstruction are the diseases of genitourinary system, gastrointestinal system, vascular system, retroperitoneal pathology and biologic agents such as actinomycosis. (Curhan & Zeidel, 1996)

The common causes of extrinsic processes are tumor of the kidney, ureter and bladder and other gastrointestinal pathologies such as Crohn's disease, appendicitis and diverticulitis.
