Pathogenesis of Cysts and Cystic Kidneys

Abstract

Although the formation of fluid-filled renal cysts is a fairly common event that has received attention for more than a century, the mechanisms involved in their development are not well understood. In this chapter we consider a series of model explanations to which we add or subtract until we arrive at one with the greatest number of favorable traits. It is agreed that renal cysts develop in pre-existing nephrons and collecting ducts, and that they can develop in the absence of distal tubule obstruction, large transmural pressure or solute gradients, abnormally stretchable basement membranes, or permanent connection to their tubule of origin. It is decided, however, that there is an absolute requirement for diffuse hyperplasia of the lining epithelium that keeps pace exactly with the enlarging surface area of the cyst cavity. At the same time, the cyst cavity is always filled with fluid, and that probably requires the new development of a net secretory mechanism. As to the question of which comes first, the cellular proliferation or the accumulation of fluid, the two in fact must occur simultaneously and are perhaps consequences of the same cause.