Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at November 20, 2016

Hydronephrosis is a condition that occurs when urine builds up in a kidney and causes it to swell. It is usually caused by an obstruction that prevents urine from draining out of the kidney and into the bladder. Sometimes hydronephrosis affects one kidney, and sometimes it affects both at the same time.


Definition & Facts

The urinary tract helps the body remove wastes and fluid. The kidneys, the bladder, the ureters, and the urethra are the components of the urinary tract.

Urine is formed in the kidneys which filters blood and removes waste materials and fluid. Urine collects in the renal pelvis, which is a section of the kidney. From there, the urine enters the ureters, which are tubes. Fluid travels through the ureters and enters the bladder, which fills up and then empties out through the urethra.

Hydronephrosis is a condition where an obstruction of some sort blocks the urine from exiting the bladder or causes urine to actually reverse directions. This then causes the kidney or kidneys to swell. In most cases, hydronephrosis is not fatal, but it can lead to serious complications such as kidney failure if left untreated. Hydronephrosis affects 1 percent of the population.

Symptoms & Complaints

Sometimes hydronephrosis doesn't cause any symptoms at all. In other cases, there may be a variety of symptoms. Often, someone with hydrophrenosis will start to feel the need to urinate more often or they may feel the need to go more urgently than they had before.

Other times, the patient will have flank pain, which is pain in the back or on the sides. Pain may also occur in the groin or abdomen. There may be pain during urination, or the patient may have trouble controlling their bladder and may have instances of urinary incontinence. This can be accompanied by nausea, vomiting, or a fever.

Symptoms vary depending on the cause of the blockage and how severe it is. Many times hydronephrosis is linked to a kidney stone. In those cases, the pain may be dense, throbbing, and extremely intense. Painful episodes can occur several times a month at first and last a few hours each time. These episodes may then increase in length and may occur more frequently. Such painful episodes require the patient to immediately seek medical attention.


Some of the most common causes of hydronephrosis include birth defects, blood clots, kidney stones, scarring from an injury or surgery, bladder cancer, colon cancer, an enlarged prostate, or a urinary tract infection. Women who are pregnant also sometimes suffer from hydronephrosis.

The most common cause of this condition is the presence of kidney stones, which form over a long period of time and often block the exit of the kidneys or travel down the urethra, which can be extremely painful. Risk factors include poor diet and obesity. People who have a family history of kidney problems are much more likely to end up with hydronephrosis than those without a family history. 

Diagnosis & Tests

If the symptoms of hydronephrosis are present, the doctor may order an ultrasound. The ultrasound will utilize sound waves to generate an image of the patient's kidneys. A physician may also want to take X-rays, a magnetic resonance imaging (MRI) scan, or a computerized tomography (CT) scan.

The doctor may order an intravenous pyelogram, which involves injecting a dye into the patient's vein and taking a series of X-rays over a period of time. This test examines how the kidneys function and usually takes an hour.

In some cases when the doctor cannot get a clear picture of what is going on, they will perform a cystoscopy. In this procedure, the doctor will use a tiny camera on a long tube to look inside the urinary tract in order to locate the blockage and determine the cause.

Often the doctor will perform blood tests or clinical urine tests. They will also check the urine and look for blood in the urine, which can indicate that there is a kidney stone or a kidney infection.

Treatment & Therapy

Medical attention needs to be pursued as soon as the patient realizes that there is a problem. Kidney issues left untreated can lead to kidney failure, which is a life-threatening condition. Treatment varies depending upon what the cause of the hydronephrosis is.

In the case of kidney stones, surgery may be involved. Other times, surgery is not required as a kidney stone can pass on its own if it is small enough. If the cause is an infection, the doctor may prescribe antibiotics. If the blockage is extreme, the doctor may use a catheter to remove urine from the bladder. A nephrostomy is a special urine-draining tube that involves the use of a catheter.

Prevention & Prophylaxis

Conditions that lead to hydrophrenosis include diabetes mellitus, cancer, and hypertension. Preventing hydrophrenosis involves preventing these risk factors and adopting an overall healthy lifestyle, including regular exercise, healthy diet, quitting smoking, and drinking alcohol in moderation or avoiding alcohol altogether.

It is recommended that everyone have regular checkups, particularly those with a family history of cardiovascular disease and kidney disease. Often, kidney issues go undetected for a long time and cause complications that could have been avoided had the underlying problem been diagnosed and treated promptly.