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Hydronephrosis; Causes, Symptoms, Treatment & Prevention

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Hydronephrosis is a condition in which one or both kidneys become swollen due to incomplete emptying of the urinary tract. It can be sudden or chronic, partial or complete, one-sided or bilateral. It can occur anywhere along the urinary tract from the opening of the kidneys to the ureters (draining the kidneys to the bladder), the bladder, and the urethra (draining the bladder). Problems with any of these structures may cause impaired emptying of the urinary system and back up of fluid and pressure.


If only one of the kidneys is affected, the condition is called unilateral hydronephrosis. If both kidneys are affected, it is called bilateral hydronephrosis.

Hydronephrosis may result in decreased kidney function. If not treated right away, permanent damage to the kidney or kidneys may occur, resulting in kidney failure.

Who gets hydronephrosis?

Hydronephrosis can occur in people of all ages. In children it is often due to structural changes in the body (anatomic abnormalities) present since birth or before. In young people, it is often due to kidney stones.

What causes hydronephrosis?

In adults, the conditions that most often cause hydronephrosis include:

  • Kidney stones: Stones that may become lodged in the kidneys or urinary tract.
  • Cancer: Tumors in the bladder, prostate gland, uterus or other organs that are part of or near the urinary tract may cause blockages that disrupt the flow of urine.
  • Benign prostatic hyperplasia (BPH): Enlargement of the prostate gland in men can cause pressure on the urethra, the tube that urine passes through before it leaves the body.
  • Having blood clots: Blood clots can develop in the kidney or ureter.
  • Narrowing or stricture of the urinary tract: This narrowing can be due to injury, infection, birth defects or surgery.
  • Nerve or muscle problems: These problems can affect the kidneys or ureters, such as from diabetes mellitus.
  • Urinary retention: Urine may be held inside the body due to an inability to empty the bladder.
  • Vesicoureteral reflux: This is a condition when urine flows backward from the bladder to the kidneys.
  • Uterocele: This is a condition where the lower part of the ureter may protrude into the bladder.

In women, hydronephrosis may occur as a result of:

  • Pregnancy: As the uterus expands, it can press on the ureters and block the flow of urine.
  • Uterine prolapse: A condition in which a woman's uterus (womb) sags or slips out of its normal position.
  • Cystocele (fallen bladder): A condition that occurs when the wall between a woman's bladder and her vagina weakens and allows the bladder to droop into the vagina.

What are the symptoms of hydronephrosis?

Symptoms of hydronephrosis usually depend on the cause. Often there are no symptoms. When symptoms occur, they can include:

  • Sudden or intense pain in the back or side
  • Nausea
  • Vomiting
  • Frequent or painful urination
  • Blood in the urine
  • Weakness or malaise
  • Fever due to a urinary tract infection
  • No major change in urine output although it may be decreased

How is hydronephrosis diagnosed?

  • Physical examination: Your doctor will ask you about any symptoms you are having and will examine the area near the kidneys and bladder for tenderness or swelling. The doctor may ask about your medical history and your family’s medical history. Your doctor will look for pelvic swelling. Men may need to undergo a rectal exam to determine whether the prostate is enlarged. Women might require a pelvic exam to evaluate whether there are any problems with the uterus or ovaries.
  • Urine tests: A urine sample will be collected and analyzed to find out if there is blood, stone crystals or any infection and bacteria present.
  • Blood tests: A complete blood count may be performed to determine whether an infection is present. Tests of kidney function including creatinine, estimated GFR (eGFR) and blood urea nitrogen (BUN) may be done.
  • Imaging procedures: The main test done is an ultrasound. This does not require radiation. A CT scan or MRI may be necessary.

How is hydronephrosis treated?

The aim of treatment is to restore the flow of urine from the kidney and to decrease the swelling and pressure caused by urine back-up. Treatment depends on the underlying condition, as that is the primary problem. You should discuss treatment options with your healthcare provider.

If the hydronephrosis is acute or sudden, a stent or soft tube (nephrostomy tube) may be inserted through the skin into the kidney to drain off excess urine. A soft plastic tube called a ureteral stent may be placed between the kidney and bladder by a urologist during a cystoscopy to drain excess fluids.

If hydronephrosis is caused by stones in the kidneys or ureters, treatment options may include:

  • Shock wave lithotripsy: This is the most common method for treating kidney stones. High-energy shock waves are emitted by a machine outside to break up the stones into dust or smaller fragments so they can pass out of the body.
  • Ureteroscopy: A thin tube with special instruments may be placed in the urethra to allow a doctor to break up and remove the stones. This method is used most often for stones in the bladder or lower half of the ureters. Ureteroscopy may be used in combination with other techniques, such as a pulsed dye laser or electrohydraulic lithotripsy, to break up stones. This is the method of choice for pregnant women, patients with blood clotting disorders and those who are morbidly obese.
  • Surgery: When kidney stones are very large or difficult to remove, they may have to be removed surgically. Also, you might need surgery in the case of tumors or other types of blockages.

Medications used to treat hydronephrosis:

  • Antibiotics may be administered to prevent or treat urinary tract infections.
  • Analgesics may be used to relieve pain.

How can I prevent hydronephrosis?

Since hydronephrosis is caused by an underlying condition, prevention depends on avoiding or promptly treating the cause. For instance, the chance of developing a kidney stone may be reduced by going to a stone clinic to find out what is causing the stones and start treatment to prevent recurrence (repeating).

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