Urinary extravasation is found to produce perinephric fluid, which is more commonly caused by urinary obstruction, such as ureteral strictures and ureteral stones. In this case, patients should undergo urography to identify the specific site of the stricture and whether there is a foreign body stuck in a section of the ureter, resulting in increased pressure in the renal pelvis. In other cases, there is an unexplained urinary extravasation, and there are no clear factors after various examinations, so only local puncture drainage can be used to drain the extravasated urine out of the body for symptomatic treatment. In some cases, the urinary extravasation improves after multiple punctures and drains, and does not recur. It may be an exudate from local lymphatic vessels or tissue mucosa, which can be cured with symptomatic treatment. It may also be a malignant tumor or mesothelioma of the endothelium that causes urinary extravasation, a complication that should be identified for the presence of tumor factors and promptly treated with surgery to relieve it.