Swollen Kidney and Hydronephrosis

Symptoms, Risk Factors, Causes, Diagnosis, Treatments, and Prognosis

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Hydronephrosis, or swollen kidney, occurs when urine backs up into one or both of the kidneys. Usually, urine can flow from the kidneys to the bladder. But when a blockage or obstruction impedes it, hydronephrosis can develop.

What Is Hydronephrosis?

The urinary tract consists of two, distinct parts. The function of the kidneys is to filter out extra water, salt, and waste. The purpose of the second part is to serve as a collection and excretion system for urine. If the urine collection system becomes blocked, urine can accumulate—which results in the swelling of the kidney. When the condition impacts one kidney, it’s called unilateral hydronephrosis; when both are affected it’s called bilateral hydronephrosis. 

Initially, a person with hydronephrosis may not experience any noticeable signs suggesting there’s a problem. But over time, signs and symptoms may gradually arise, causing discomfort and compelling them to see a doctor. The extent of the symptoms patients are likely to experience depends on the reason for the blockage and its severity.  

To maximize recovery outcomes, the sooner a person can seek treatment for hydronephrosis, the better. As a result of untreated hydronephrosis, kidney function may lessen, and lasting damage could occur to one or both of the kidneys, which could lead to kidney failure later on down the road.

Risk Factors

There are no known risk factors associated with a diagnosis of hydronephrosis. Hydronephrosis can affect people of all ages, from before birth to adulthood. If hydronephrosis happens before birth, it’s known as antenatal hydronephrosis or fetal hydronephrosis.

Boys are four to five times more likely to experience hydronephrosis than girls, according to the Department of Urology at the University of North Carolina (UNC) School of Medicine. However, UNC School of Medicine notes the condition isn’t linked to family history. In the case of fetal hydronephrosis, they emphasize the condition isn’t preventable, and its onset isn’t caused by something the parents did or didn’t do something during pregnancy.  

Signs and Symptoms

A person with hydronephrosis may not be aware they have the condition. When symptoms are present, they may show up within a range of time that could span hours to weeks, even months. Symptoms can include:

  • Pain in the abdomen, side, or back (flank pain)
  • Pain during urination
  • Blood in the urine (hematuria)
  • Nausea
  • Vomiting
  • Urinary tract infection (UTI)
  • Fever
  • A more intense urge to urinate
  • Changes in urinary frequency, either more or less
  • Unable to void completely
  • Weak urine stream
  • A general feeling of tiredness
  • Incontinence
  • Infants may demonstrate a failure to thrive
  • In extreme cases, kidney swelling may be detectable by looking at it or touching the kidney region.


There are many reason hydronephrosis may occur in people. Some of those reasons include:

  • Kidney stones that get stuck in the or urinary tract
  • A tumor situated in the abdomen or pelvis that interferes with the flow of urine
  • In men, benign prostate hypertrophy (BPH), or an enlarged prostate, may make it difficult to urinate.
  • Urinary retention
  • Narrowing of the structures of the urinary tract
  • Prolapsed organs of the pelvis
  • Pregnancy, where the uterus can put pressure on the urinary tract as it grows bigger.
  • Nerve damage to the nerves that go to the bladder
  • Problems with the muscles supporting the urinary tract
  • Vesicoureteral reflux, where urine flows in a backward direction from the bladder into the kidneys.
  • Blood clots
  • Less commonly, endometriosis and ovarian cysts may be contributing factors.


To diagnose the condition, you may be referred to a urologist. Some of the methods used to determine whether or not you have hydronephrosis are:

  • Physical Assessment: The physician will take a detailed account of your symptoms and look at the kidney area. They might palpate the area for signs of swelling or tenderness.
  • Imaging: The doctor may use ultrasound, x-rays, or other forms of imaging to determine if your kidney is swollen.
  • Lab Work: Lab work might include a blood test to evaluate your kidney function and check to see if you could have an infection. You may also be asked to provide a urine specimen for a urinalysis to check for signs of an infection or kidney stones.


Although the treatment for hydronephrosis varies depending on the reason for the condition, in some cases, the situation resolves without the need for medical intervention. In mild to moderate cases, your physician may choose to wait and see if the condition improves on its own.

In severe cases of hydronephrosis, treatment may include surgery to remove blockages or correct reflux so that the urine can flow in its usual direction. 

If your physician suspects you have a urinary tract infection or if you are at risk of developing one, they may prescribe you a course of antibiotics. If pain is an issue, you may also receive a prescription for medication to relieve it; these might include an over-the-counter drug or a prescription medication for pain management.

As stated earlier, when severe hydronephrosis cases are left untreated, or the condition doesn’t resolve by itself, it could result in irreversible damage to the kidney. But the Mayo Clinic reports hydronephrosis is most likely to affect one kidney, rather than two. Kidney’s are powerful organs in the body, and, if necessary, one kidney is capable of doing the work of two. Fortunately, the good news is that with proper treatment, the condition is likely to improve.


When the cause of hydronephrosis is determined, there may be certain lifestyle modifications patients can implement to lessen the chances of it happening again. For example, if a person is prone to kidney stones, a specialized diet may help to avoid a recurrence of them.

As another example, if hydronephrosis is caused by urinary retention, muscle and nerve problems in the pelvis, or organ prolapse, pelvic floor therapy from a trained physical therapist can assist with retraining the bladder to work in a more normal way.

A Word From Verywell

Any medical diagnosis can be scary, but thankfully, the prognosis for hydronephrosis is good when you seek appropriate medical treatment. If you develop a fever, sudden pain in the abdomen, side, or back, or any other symptoms of hydronephrosis, don’t wait to get the care you need; see your doctor as soon as possible.

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