Idiopathic retroperitoneal fibrosis (IRF) is a widespread fibrosis of the retroperitoneal connective tissue of unknown origin, which is clinically rare and easily misdiagnosed. The ratio of male to female is about 1.8-3:l, and the age is mostly 50-60 years old, and it is more common in Caucasians. Causes: Urinary extravasation; recurrent inflammatory diseases of the gastrointestinal tract and genitourinary tract; systemic sclerosis, lupus erythematosus or local manifestations of Weber-Christan disease are possible causes of the disease. Clinical features: 1. The disease starts insidiously and lacks specific clinical manifestations in the early stage. The most common one is dull pain in the low back and radiates to the lower abdomen, groin or genitals, which starts unilaterally and later appears bilaterally and does not decrease due to position change. 2. As the disease progresses, manifestations of compression of retroperitoneal tubular structures may appear. Lower limb edema may occur due to compression of the inferior vena cava, iliac vein or lymphatic vessels; ureteral dilatation and hydronephrosis or renal failure may occur due to ureteral compression. This disease accounts for 13.4% of patients with obstructive anuria, so the possibility of this disease should be considered when encountering unilateral or bilateral urinary tract obstruction of unknown origin in clinical practice. Diagnosis: The disease is almost always misdiagnosed preoperatively, and CT and urographic examinations are of great value. The typical CT picture is an irregularly shaped high-density mass located in front of and on both sides of the aorta, with no anterior displacement of the aorta and no erosion or destruction of adjacent bone or tissue. 2. There are three major signs on urography: (1) varying degrees of hydronephrosis with flexion and dilatation of the upper and middle ureter; (2) foreign compression of the ureter, thinning in the shape of a shuttle, or rigid stenosis, usually with a lesion length of 3-150 px, but the ureteral wall is still smooth; (3) displacement of the ureter to the midline. Treatment: This disease is exceptionally difficult to excise completely because of the extensive fusion of fibrous tissue with the abdominal organs. The aim of surgery is to loosen the ureter and important blood vessels, release the compression and improve the symptoms. Open the fibrous tissue, free the ureter, encase the ureter with large omentum or peritoneum, or move it to the paracolic sulcus on both sides of the abdominal cavity, and reimplant the detached ureteral bladder if necessary. For the upper and lower vena cava or skeletal arteries, vascular fibrous sheath debridement or autologous vascular dissection and grafting is feasible, but venous release of the vena cava or skeletal veins is not advisable to avoid hemorrhage from venous rupture, and the lower limbs should be elevated and wrapped with elastic bandages after surgery to wait for the establishment of collateral circulation. Prognosis: The disease has a tendency to self-limiting remission, and the prognosis is more optimistic.