图示：肾盂积水（由长期尿路阻塞引起）致肾盂肾盏明显扩张。如为单侧肾脏病变阻塞部位位于输尿管及以上，如结石、肿瘤或较少见的炎症所致的狭窄。此种阻塞如发生于儿童可能提示有先天性输尿管畸形。双侧肾盂积水发生于膀胱或前列腺的病变，如膀胱移行细胞癌或前列腺增生。功能性阻塞可能见于自主神经异常，如糖尿病。如果阻塞呈慢性进行性经过，将有肾功能的持续性破坏。
The renal pelvis and calyces show marked dilation, consistent with hydronephrosis, the result of chronic urinary tract obstruction. If unilateral, it may be due to obstruction at the level of the ureteral orifice and above, as from a calculus or neoplasm, or less commonly a stricture from inflammation. Such obstruction becoming evident in childhood suggests a urinary tract anomaly. Bilateral hydronephrosis occurs from lesions within the urinary bladder or prostate, such as nodular prostatic hyperplasia or a transitional cell carcinoma of the bladder. Functional obstruction may result from autonomic neuropathy, as with diabetes mellitus. If obstruction remains chronic and progressive, there is continuing loss of renal function.