NA;Aortograms and selective renal angiograms were performed in experimental pyelonephritis in rabbits at various stages of infection. The kidneys were then perfused with barium sulfate and sectioned and microangiographs were made. These same sections were then embedded for histologic sectioning. During acute infection, there is pronounced cortical vasoconstriction, largely localized to areas of acute inflammation. The nephrogram phase of the angiogram is delayed and protracted, reflecting sluggish flow through the peritubular capillaries clogged with neutrophils, part of the widespread capillary and tubular destruction. As acute inflammation passes, vasoconstriction remits, but as the chronic stages progress, microangiographs reveal marked spiraling of the arteriesmdash;the result of contraction of fibrous scar tissue which also obliterates many of the remaining peritubular capillaries. This is reflected in the increasingly pallid and transient nephrogram phase on angiograms, indicating greatly diminished renal blood flow. There is also marked reduction in arterial caliber related, in part, to fibrous contraction and, in part, to reduced blood flow.
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