Acute Renal Failure in Children

Abstract

In case of acute renal failure (ARF), the primary role of imaging is to exclude post-renal obstructive causes by demonstrating bilateral urinary tract dilatation (unilateral in case of a single kidney). The examination will aim to demonstrate the degree and level of obstruction. Whenever a mass (or a mass effect) is demonstrated, complementary evaluation through MR imaging (preferably) or CT may be necessary in order to precise the diagnosis. The use of contrast material should be carefully evaluated in children with ARF in order to avoid worsen the renal impairment.

The next role for imaging would be to demonstrate an underlying disease that has favored the occurrence of an acute episode (urinary tract infection in case of congenital uropathies, obstructive urolithiasis in case of metabolic diseases…)

A further role, would be to orient towards acquired pathologies following surgery or secondary to some specific medications (see below).

The last challenge would be to find anomalies on imaging (mainly US) that may facilitate the diagnosis of renal (or pre-renal origin for the ARF). Unfortunately, in most cases, the only anomaly that will be detected will be parenchymal hyperechogenicity (as compared to the liver or to the spleen) associated or not with increased renal size (evaluated on the longest sagittal scan of the kidney), both being non-specific findings. The final diagnosis would be ascertained for many cases only through biopsy and histology. Noteworthy, Doppler (duplex and color) may help in some entities (Hemolytic and uremic syndrome, renal vein thrombosis) to clarify or better assess the diagnosis. Norms for RI are age dependent, higher, >0.8, in younger children, around 0.7 in older children.

Finally, US may be used to guide biopsies when the diagnosis remains unclear.