The possible role of uric acid in renal hyper-echogenicity in neonatal hypoxic acute shock.

Sonographic examinations as well as blood and urine chemistry tests were carried out in 4 neonates (3 mature, 1 premature) with transient renal failure, who were suffering from the effects of neonatal asphyxia of varying etiology. The first ultrasound examinations of the kidneys were performed within 24 hours after the hypoxic event. Simultaneously, blood and urine tests for parameters of renal function and purine metabolites were also carried out. Transient insufficiency of renal function could be detected in all cases with hyper-uricemia and hyper-uricosuria with no hypercalciuria. Ultrasonographic examinations showed hyper-echogenicity of the renal pyramids in all of the cases and hyper-reflectivity of the renal cortex in cases 2 and 4. In 3 cases, hyper-echogenicity appeared within 24 hours and disappeared in a short time, while in case 3 it could be detected from day 4 until day 14. These findings demonstrate, that the neonatal kidney is very sensitive to hypoxia and that hypoxic renal failure is accompanied by hyper-echogenicity of the kidneys. Uric acid is a possible cause of the renal hyper-echogenicity.