The structure and ultrastructure were studied of 48 specimens from cases of congenital ureteroplevic junction obstructions and primary obstructive megaureters. Under light microscopy a spectrum of findings occurs, extending from the nearly normal to the clearly abnormal obstructive segments. However, under electron microscopy there were consistent abnormalities: 1) excessive collagen fibers between and around the muscle cells and 2) a group of compromised muscle cells proximal to the collagenous segment. These findings are responsible for functional discontinuity via the nexus and indistensibility of the pathologic areas. The high resolution of the electron microscope allows clearer definition of these obstructions and the impact of these findings on surgical remodeling is discussed.

We report a unique case of renal echinococcal disease. The patient presented with only a left renal pelvic filling defect without hepatic, pulmonary or other renal involvement. Management consisted of successful exploration and removal of the hydatid mass without sacrifice of renal tissue. The pathogenesis, diagnosis and treatment of echinococcal disease are reviewed.

Twenty-eight normal human ureters were examined under the light and electron microscope. Three uretero-trigonal units were microdissected. The ureter is a non-layered muscular tube wherein the anatomical unit is muscle bundles that contain heterogeneously oriented muscle cells. Functional continuity of muscle cells is provided through the nexus, which are clearly defined structures. A group of morphologically distinct muscle cells are identified and these may represent the ureteral pacemaker cells. The functional status of muscle cells causes certain morphologic changes and, thus, the cells fixed in contraction differ from those fixed in relaxation and in vitro testing of muscle cell contractility is feasible. The ultrastructure of the normal urothelium and the adrenergic and cholinergic components of ureteral nerves are presented briefly.

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