Hydronephrosis | Symptoms and Causes

What are the symptoms of hydronephrosis?

Most babies with hydronephrosis have no symptoms. Older children may also have no symptoms if they have mild or moderate hydronephrosis, and the condition may disappear on its own.

If your child has moderate to severe hydronephrosis, some symptoms may include:

  • pain in the abdomen
  • pain in the side (flank pain)
  • blood in the urine (hematuria)

A child with hydronephrosis may develop a UTI.  Symptoms of a urinary tract infection can include the following:

  • strong urge to use the bathroom
  • painful urination
  • cloudy urine
  • back pain
  • fever
  • vomiting

If your infant has had multiple urinary tract infections (UTIs) with (or without) a fever, it could indicate some kind of obstruction or reflux in the urinary system. However, UTIs can be difficult to spot in infants: In many cases, multiple, unexplained fevers are the only sign.

Older children may have more recognizable symptoms of UTIs, including a strong urge to urinate, painful urination or cloudy urine. If your child tends to get repeat UTIs, you may want to have him evaluated for possible urinary tract obstruction.

What are the causes of hydronephrosis?

Two types of problems cause hydronephrosis. One is obstruction, where urine is physically prevented from draining out of the kidney. The obstruction, or blockage, can occur at any point in the urinary system from the kidney down to the urethra. The second is reflux, in which urine flows back up into the kidney.

Blockage (obstruction)

  • Ureteropelvic junction (UPJ) obstruction: A blockage at the point where the kidney joins the ureter (the thin tube that carries urine to the bladder). A narrowing at the top of the ureter is usually the cause.
  • Ureterovesical junction (UVJ) obstruction: A blockage at the point where the ureter joins the bladder.
  • Posterior urethral valves (PUV): A congenital condition, found only in boys, in which there are abnormal flaps of tissue in the urethra, causing bladder obstruction. This type of obstruction is also associated with vesicoureteral reflux. See below.
  • Ureterocele: A bulge in the ureter that can obstruct part of the kidney and sometimes the bladder.
  • Vesicoureteral reflux (VUR): A backwash of urine that happens when the muscles at the junction of the ureter and bladder aren’t working properly and allow urine to flow back up toward the kidney with bladder filling or emptying.

Other causes of hydronephrosis

  • Ectopic ureter: A rare condition where a ureter doesn’t connect to the bladder in the normal location.
  • Unknown:  In more than half of the children who are prenatally diagnosed with hydronephrosis, the condition resolves itself and the cause is never known.