Invasive assessment of fetal renal abnormalities: urinalysis, fetal blood sampling and biopsy.

There are a number of potential biochemical markers that may have some role in predicting renal function postnatally. These include urinary sodium, calcium and beta2-microglobulin. The latter may also be measured in fetal serum. However, the accuracy of these parameters at a point in time is far from perfect as urinary tract obstruction is a progressive disease which may be best defined by repeated observations throughout pregnancy.

Fetal urine biochemistry in the assessment of obstructive uropathy.

In 60 fetuses with obstructive uropathy, sodium, total calcium, urea, and creatinine were measured in samples obtained by "urodochocentesis" or pyelocentesis at 16 to 36 weeks' gestation. The patients were retrospectively assigned into two groups on the basis of outcome. Group 1 (n = 20) included infants who either had normal postnatal renal function or absence of prenatal renal dysplasia. Group 2 included infants who either had histologic evidence of renal dysplasia or subsequently developed renal failure. In group 1 the urinary sodium decreased and creatinine increased with gestation, demonstrating maturation in fetal renal function. In group 2 the urinary sodium and calcium were higher and the urinary urea and creatinine were lower than in group 1. The best predictor of outcome was the combination of either high calcium or high sodium with a positive predictive value of 91.3% and negative predictive value of 77.7%. In the antenatal evaluation of obstructive uropathy, fetal urinary biochemistry provides useful information for more accurate counseling of the parents and a rational basis for selecting patients who may benefit from intrauterine therapeutic interventions.

Dipstick urinalysis screening of asymptomatic adults for urinary tract disorders. I. Hematuria and proteinuria.

We review evidence on the value of dipstick urinalysis screening for hemoglobin and protein in asymptomatic adults. In young adults, evidence from five population-based studies indicates that fewer than 2% of those with a positive heme dipstick have a serious and treatable urinary tract disease, too few to justify screening and the risks of subsequent workup. For older populations, evidence is contradictory and no recommendation can presently be made for or against hematuria screening. A population-based randomized, controlled trial of hematuria screening in the elderly is urgently needed. Proteinuria screening is not recommended in any healthy, asymptomatic adult population, since four population-based studies have found that fewer than 1.5% of those with positive dipsticks have serious and treatable urinary tract disorders.

Current assessment of microhematuria and leukocyturia.

Technical advances in laboratory testing such as sensitive chemical tests and standardized commercial slides have significantly altered our entire approach to urinalysis. In addition, the recognition of the association of microhematuria with urologic neoplasms and the morphologically altered red blood cells with renal parenchymal bleeding is beginning to expand our knowledge of the pathogenesis of microhematuria. Future trends may include a broader range of chemical tests as well as a better understanding of disease processes associated with microhematuria.