The current approach to the assessment of fetal renal function: fact or fiction?

The wide use of ultrasonography during pregnancy has led to the identification of a relatively large number of renal and urinary tract abnormalities, particularly hydronephrosis. Uncertainty, however, exists regarding the indications for surgical intervention. Prominent among the variables currently used to assess fetal renal function and predict the long-term outcome are measurements of urinary concentration of electrolytes and low molecular weight proteins. It has become, therefore, imperative to examine the evidence on which the selection of these variables is based, before they become entrenched in medical practice. The analysis reveals that single measurements of any of these variables is unlikely to be reliable. Sequential measurements, albeit more dependable, are impractical due to the narrow window of opportunity for useful surgical intervention. It is therefore necessary to search for new, innovative approaches aimed at detecting changes in the kidney or urine that reflect the biological response of the developing kidney to injury. Such markers may be represented by renal metabolites or peptides involved in the maintenance of renal function under conditions of stress.