Prevention of Pyelonephritis by Water Diuresis: Evidence for the Role of Medullary Hypertonicity in Promoting Renal Infection.

The medulla of the kidney is much more susceptible to infection than the cortex (1-5). The unique vulnerability of the renal medulla has been ascribed in the past to its anatomical location (6), to its relatively poor circulation (7), and to its chemical composition, in particular to its content of ammonia and ammonia-producing enzymes that inhibit the action of complement (8). The present experiments suggest that the susceptibility of the medulla to infection is determined at least in part by another of its properties, namely, its habitual hypertonicity. A simple method for inducing chronic water diuresis in rats has provided a model for studying many aspects of experimental pyelonephritis. Renal infection in rats can be prevented by decreasing the normally hypertonic environment of the renal medulla through sustained water diuresis.