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In-utero Hydronephrosis

By Philip E. Gleason, MD

Hydronephrosis is a non-specific, pathologic finding of dilatation of the renal collecting system. It can represent either dilatation of the renal pelvis alone with a normal ureter or dilatation of both the renal pelvis and ureter. It is though to occur in approximately 1 in 500 people in the general population. It can, in fact, be normal, representing a normal anatomic variant without any physiologic abnormality or problem. However, it can also be a sign of other underlying pathology to the kidney and that is, in fact, the most common situation. The differential diagnosis, therefore, also includes vesicoureteral reflux (VUR) in which urine is abnormally refluxed backwards up to the kidney from the bladder, producing dilation of the kidney. It can also represent obstruction the kidney either at the site of drainage from the kidney into the ureter or perhaps from the ureter into the bladder or even obstruction of the bladder itself. Because it does predispose to risks of developing urinary tract infections (UTI's), patients are usually placed on prophylactic antibiotic protection to help prevent the development of UTI and subsequent radiographic evaluation is typically performed. This often includes a nuclear renal scan or possible IVP to further outline the anatomy and function of the kidney and, in particular, look for evidence of obstruction. A VCUG or bladder x-ray is also performed to evaluate for possible reflux or obstruction of the bladder. If these studies demonstrate a specific problem, then that can be addressed with further evaluation of further treatment as needed. If the studies are, in fact, benign or normal, then the hydronephrosis is considered a normal anatomic variant and it is followed conservatively with serial renal ultrasound to follow the course of the hydronephrosis. It may ultimately resolve spontaneously. It is worthwhile, however, to follow the hydronephrosis to ensure ongoing normal anatomy and function of the kidney.