Distinctive ultrastructural pathology of nonulcerative interstitial cystitis: new observations and their potential significance in pathogenesis.

Ultrastructural study of the bladder in interstitial cystitis has, so far, been limited, mainly to the urothelium. The present study was conducted first to study in detail the ultrastructural features of all tissue components of the bladder wall in nonulcerative interstitial cystitis and second to derive clues from the observed changes to pathogenesis of the disease. Endoscopic biopsies of urothelium with attached suburothelium, and muscularis, were obtained from both lesional and nonlesional areas in 5 female patients with unequivocal clinical diagnosis of interstitial cystitis. The specimens were processed for electron microscopic study by standard methods and subjected to comprehensive ultrastructural study of urothelium, suburothelium, detrusor muscle cells, intrinsic blood vessels, and intrinsic nerves. A distinctive combination of peculiar muscle cell profiles, injury of intrinsic vessels and nerves in muscularis and suburothelium, and discohesive urothelium was observed in lesional and less markedly in nonlesional samples of all specimens. Marked edema of various tissue elements and cells appeared to be a common denominator of many observed changes. Edema of muscle cells resulted in characteristic querciphylloid profiles, so designated because of peripheral bosselation of cell sarcoplasm with a lobed perimeter resembling that of an oak leaf. Urothelial changes disrupted the true permeability barrier, consisting of asymmetric unit membrane and triple epithelial junctions of surface (umbrella) cells. Vascular lesions included endothelial cell injury and suggested sluggishness of intrinsic microcirculation. Neural changes included a combination of degenerative and regenerative features, some expressing neural plasticity. The observed ultrastructural changes appear to be sufficiently distinctive to be diagnostic in specimens submitted for pathologic confirmation of nonulcerative interstitial cystitis. The changes do not support a primary pathogenetic role of mast cells or a selectively deficient glycosaminoglycan layer. They do suggest, however, a pathogenesis based on a potentially self-perpetuating process of neurogenic inflammation that can trigger a biologically potent cascade of events, including a leaky urothelium and mast cell activation. As proposed, neurogenic inflammation consolidates various proposals advanced as the pathogenesis of interstitial cystitis and can readily accommodate infectious, immunologic, and autoimmunologic mechanisms as factors that contribute to development or chronicity of the disease.