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The swelling of one or both kidneys is known as hydronephrosis. When urine cannot drain from a kidney, it builds up in the kidney, causing it to swell. A blockage in the ureters (tubes that drain urine from the kidneys) or an anatomical defect that prevents urine from draining normally might cause this.


Hydronephrosis can happen to anyone at any age. Hydronephrosis in children can be detected during infancy or even before the infant is born during a prenatal ultrasound.


Urine normally flows from the kidney to the bladder through a tube called the ureter and then out through the urethra.  However, urine can sometimes back up or remain in the kidney or ureter. When this happens, hydronephrosis can develop.

The most common causes of hydronephrosis are:

Blockage of Urinary tract: Urinary tract blockages frequently occur where the kidney joins the ureter. Blockages at the junction of the ureter and the bladder are less common.

Vesicoureteral reflux: It occurs when urine runs backward from the bladder up into the kidney through the ureter. Urine normally flows in only one direction through the ureter. When urine flows in the wrong direction, it makes it difficult for the kidney to drain correctly, causing it to swell.


Kidney stones, abdominal or pelvic tumors, and nerve issues leading to the bladder are some of the other causes of hydronephrosis.

Signs and Symptoms

Symptoms of hydronephrosis are not always present. When signs and symptoms of hydronephrosis develop, they may include:

  • Side and back pain that may radiate to the lower abdomen or groin.
  • Urinary issues include urination pain or the urge to urinate urgently or frequently.
  • Nausea and vomiting
  • Fever

Risk Factors

The risk factors of hydronephrosis include:

  • Stones (Uretral, bladder, kidney)
  • Renal calculi
  • Trauma
  • Strictures
  • Neurogenic Bladder
  • Endometriosis, ovarian cysts, pelvic prolapse
  • Abdominal Malignancies
  • Prostate enlargement and cancer
  • Pelvic masses or tumors
  • Urinary tract infection
  • Congenital anomalies of urinary tract and kidneys
  • Pregnancy
  • Radiation 


You would probably be referred to a urologist (a specialist who specializes in urinary system diseases) by your primary care physician for diagnosis.

The following tests are often ordered to diagnose hydronephrosis:

  • A blood test such as renal function tests to see how well your kidneys work.
  • A urine test is used to look for signs of infection or urinary stones that could cause a blockage.
  • An ultrasound imaging test allows your doctor to look at your kidneys, bladder, and other urinary structures to see any underlying issues.
  • A specialized X-ray of the urinary tract captures images before and during urination to outline the kidneys, ureters, bladder, and urethra.
  • Ct scan or MRI: Your doctor may recommend additional imaging tests, such as a CT scan or an MRI, if necessary. A test called a MAG3 scan, which evaluates kidney function and drainage, is another option.


The underlying etiology of hydronephrosis determines the treatment. Hydronephrosis usually resolves on its own, although surgery may be required in some cases. Whether you have mild to severe hydronephrosis, your doctor may decide to wait and see if you improve on your own. Nonetheless, your doctor may advise you to take antibiotics to prevent urinary tract infections. When hydronephrosis makes it difficult for the kidney to function — as it might in more severe hydronephrosis or hydronephrosis with reflux — surgery to relieve a blockage or correct reflux may be necessary. Severe hydronephrosis, if left untreated, can result in permanent kidney damage. It can cause renal failure in some cases. However, hydronephrosis usually affects only one kidney, and the other kidney can perform the same function for both.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on April 21th, 2023.


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