Hydronephrosis

Hydronephrosis

Signs and Symptoms
Diagnosis
Treatment

Diagnosis

Hydronephrosis usually is diagnosed in one of two ways.

1. An ultrasound during pregnancy may reveal a fetus with dilated kidneys. This occurs in 1 per 100 pregnancies.

2. An ultrasound done as part of an evaluation for another medical problem, such as a urinary tract infection or incontinence, may reveal hydronephrosis.

Once hydronephrosis is noted, whether during pregnancy or later, additional tests often are required to find out the severity. These tests are important because early diagnosis and treatment of a potential abnormality can prevent urinary tract infections and permanent kidney damage or scarring.

Tests include:

• Voiding Cystourethrogram (VCUG) -- A VCUG gives us important information about the shape and size of the bladder, the bladder neck or opening and the tubes that drain the urine from the kidneys into the bladder called ureters. It allows us to diagnose reflux -- the abnormal back-flow of urine from the bladder into the ureter and up to the kidney. It also gives us anatomic information about the urethra, the tube that takes urine from the bladder outside the body, to make sure there's no blockage, a condition called posterior urethral valves.

• Kidney (Renal) Scan -- A kidney scan may be performed depending on the history of urinary tract infections, result of VCUG and the severity of the hydronephrosis. It is used to show the function and drainage of the kidneys. A kidney scan also can show if there is kidney damage and scarring from a previous urinary tract infection or long-standing hydronephrosis. Two types of renal scans are typically performed depending on the diagnosis.

  • Lasix Renogram or MAG-III diuretic renogram: This tests for significant blockage in the urinary tract.
  • DMSA (dimercaptosuccinic acid) scan: This tests for scarring or damage to the renal tissue, which is more common in patients with vesico-ureteral reflux.

If your newborn child had hydronephrosis -- kidney, ureter or bladder dilation -- noted on a pre-natal ultrasound, another ultrasound should be conducted one to three days after birth. It is normal for a newborn to be dehydrated and produce less urine on the first day of life. It may falsely appear that your baby no longer has hydronephrosis. Certain conditions seen on the ultrasound such as severe hydronephrosis in both kidneys or a dilated bladder may warrant more tests. A VCUG will be performed within the next several weeks of life.

Hydronephrosis is graded on a scale from zero to four, with one the mildest form and four the most severe. The degree of hydronephrosis is used to help decide the treatment for the underlying cause of the hydronephrosis. More severe grades of hydronephrosis require more extensive tests. For example, grade III and IV hydronephrosis (not due to vesicoureteral reflux) typically require a renal scan.

Reviewed by health care specialists at UCSF Children's Hospital.
Last updated May 8, 2007