Definition of Hydronephrosis

Hydronephrosis is a common prenatal and infantile condition characterized by an obstruction of urine flow somewhere along the urinary tract that is easily treatable.

The Basics

• The urinary system is composed of four main parts--the kidneys, bladder, ureters and urethra. The urine is carried from the kidneys down to the bladder through the ureters and then "voided," or emptied, through the urethra.

Significance

• Boys are four to five times more likely to develop hydronephrosis. An increased awareness has brought many more prenatal diagnoses and swifter treatment than in the past.

Diagnosis

• Diagnosing hydronephrosis generally happens during a routine prenatal ultrasound and will lead to a search for the cause of the obstruction.

Types and Treatments

• Hydronephrosis is graded on a scale of 1 to 4 in severity. Children with mild to moderate (1 to 3) hydronephrosis will likely be watched as these generally correct themselves, but children with stage 4 hydronephrosis will probably see surgery in their future to correct the obstruction.

Causes

• While vesicoureteral reflux, which occurs when urine is pushed back up the ureters into the kidney, and ureteropelvic junction obstruction, which occurs when the ureter is "kinked" or narrow where it joins the kidney, are both causes for hydronephrosis, it is unknown why some babies are born with the anomalies that lead to the condition.