Renal function in cyanotic congenital heart disease

We performed renal function tests in 18 young patients, 1.8-14.6 years of a ge, with cyanotic congenital heart disease (CCHD). Glomerular filtration ra te was normal (116 +/- 4.5 ml/min/1.73 m(2)), and renal plasma flow was dec reased (410 +/- 25 ml/min/1.73 m(2)) with a rise in the filtration fraction (29 +/- 1.1%). The suggested pathophysiologic explanation of these finding s is that the blood hyperviscosity seen in patients with CCHD causes an ove rall increase in renal vascular resistance with a rise in intraglomerular b lood pressure. Despite a sluggish flow of blood in the glomerular capillary bed, the effective filtration pressure was adjusted to conserve the glomer ular filtration rate. In addition to these renal hemodynamic parameters, we also studied renal acidification and tubular sodium and water handling dur ing a forced water diuresis. Our data indicate that children with CCHD have a mild to moderate normal ion gap metabolic acidosis due to a low proximal tubular threshold for bicarbonate. Proximal tubular sodium and water reabs orption under these conditions were somewhat increased, though not signific antly, probably due to intrarenal hydrostatic forces, in particular the ris e in the oncotic pressure in the postglomerular capillaries in patients wit h high hematocrit values. The distal tubular functions such as sodium handl ing and acidification were not affected.