Mechanisms of development and progression of cyanotic nephropathy.

Cyanotic nephropathy (CN) is often accompanied by congenital cyanotic heart diseases (CCHD). The purpose of this study was to clarify the risk factors and the mechanisms of involved in the development and progression of CN. Thirty patients with CCHD were examined. We analyzed the risk factors for the development of CN on the basis of the clinical and laboratory findings. We also examined ten renal biopsy specimens obtained from patients with CN. Patients with CN showed significantly higher hematocrit levels than those without CN (P=0.025), although there was no difference between the two groups in terms of oxygen saturation. The renal plasma flow (RPF) in patients both with and without CN was low. However, the filtration fraction (FF) was significantly lower in patients with CN than in those without CN (P=0.001). The glomeruli of biopsy specimens with significant proteinuria (n=7) were larger than those of biopsy specimens without significant proteinuria, and there were more capillaries per glomerulus in the former than in the latter (n=3) and the control specimens (n=6) (glomerular size: P<0.01; number of glomerular capillaries: P<0.01). In conclusion, hyperviscosity by polycythemia may be responsible for the development of CN. This pathological condition may induce an angiogenic increase in the glomerular capillary beds, in turn leading to glomerulomegaly. In addition, the failure of a compensatory mechanism to respond to reduced RPF by hyperfiltration may be accompanied by the development and progression of CN.