1-It could be due to intrinsic or extrinsic causes.
2-Intrinsic causes such as ureteric malignancy or presence of stone in its lumen, while extrinsic causes such as extrinsic compression due to lymphadenopathy as in metastases or lymphoma or retroperitoneal fibrosis.
3-Some inflammatory conditions such as tuberculosis or schistomiasis could cause fibrosis of the ureteric wall leading to ureteric stricture.
