Microvascular changes in the early stage of reflux pyelonephritis. An experimental study in the pig kidney.

Renal microvascular changes were studied in the pig kidney during the initial stage of reflux pyelonephritis. In 10 piglets vesicoureteric reflux was surgically induced. The animals were then infected with a strain of Escherichia coli and sacrificed 2 weeks following the initiation of infection. Following injection of the kidneys with Microfil, microvascular changes were investigated by a combined stereomicroscopic, microradiographic and histological technique. Renal microcirculation was found to be impaired in the areas involved in the acute inflammatory process, owing to the compression of glomeruli, small peritubular capillaries and vasa rectae by the ensuing interstitial oedema. These findings indicate that acute focal ischaemia caused by microvascular obstruction could be an important factor in the mechanism of renal damage in reflux pyelonephritis.