Definition and Overview

Hydronephrosis is a term that translates to “water inside the kidney.” It occurs when a part of the urinary tract is blocked or narrowed. As such, the urine cannot flow out of the body. Instead, it flows right back up into the kidneys. As the urine starts to build up, the kidneys begin to swell.

The kidneys are one of the most important organs in the body. They ensure that the blood is clean and free from toxins. However, they can cause a number of problems if they become swollen.

One of the first symptoms of the condition is a mass that can be felt in the abdomen or flank area. It also causes urinary tract infections (UTI).

The condition must be treated before it gets worse. Unless a patient sees a doctor right away, he or she has an increased risk of:

  • Kidney infection - Bacterial infections can occur when urine stays in the body longer than it should. The infection can start in the bladder and then travel to the kidneys. A kidney infection is an unpleasant illness. It makes urinating very painful.

  • Blood infection - Infection from the kidneys can travel to the bloodstream. This is a serious condition and is treated as a medical emergency.

  • Kidney failure - In severe cases, the condition can cause the kidneys to fail. This means they will no longer be able to filter the blood. When this happens, the patient will need regular dialysis in which a machine is used to clean the blood. Over time, they will need a kidney transplant. Both treatments can be very expensive.

If treated early, the overall outlook is very good. Doctors will drain the urine that has built up in the kidney and remove anything that blocks the urinary tract.

Causes of Condition

The condition occurs when there is blockage anywhere from the kidneys to the urethra. This obstruction can be caused by kidney stones, blood clots, or scar tissue. Less common causes are pregnancy and enlarged prostate glands. Some cases are due to birth defects, abnormal growths, or injuries that make the ureter narrower.

Key Symptoms

The first sign of the condition is a urinary tract infection (UTI). A person with a UTI suffers from burning pain each time they pee. This infection can lead to fever. Patients also suffer from severe back pain. If left untreated, symptoms can worsen quickly. The disorder can increase the risk of kidney infection as well as blood poisoning. It can also cause the kidneys to fail.

The severity of symptoms depends on many factors. These include whether the disorder is acute or chronic. It also depends on whether the obstruction is only partial or complete and if only one or both the kidneys are affected.

Who to See and Types of Treatments Available

Patients with signs of the condition must consult a kidney specialist as soon as possible. The earlier the condition is caught, the better are the treatment outcomes. This can also prevent permanent damage to the kidneys.

During the assessment, the doctor will ask the patient about his or her symptoms. The doctor will then conduct a physical exam. Doctors will begin to suspect hydronephrosis if the patient is showing signs of a swollen kidney and UTI. Imaging tests are then used to confirm the diagnosis. These tests provide clear pictures of the organs and can show the exact location of the blockage.

Doctors treat the condition by:

  • Draining the urine that has built up in the kidneys - This is done using a catheter. The procedure causes the kidneys to return to their normal size. It also reduces the risk of infection. The catheter can also be used to remove small kidney stones as well as blood clots that may be blocking the urinary tract.

  • Surgery - Surgery is advised if the kidney stones are too big and cannot be removed with a catheter. This can be done without making a huge incision in the abdomen. Instead, the surgeon will use small but several (about four to five) cuts. A small camera and special tools are then inserted into the incisions so the surgeon can remove blood clots or kidney stones. This method reduces the many risks of open surgery and speeds up recovery.


  • Toka HR, Toka O, Hariri A, Nguyen HT (July 2010). “Congenital anomalies of kidney and urinary tract”. Semin. Nephrol. 30 (4): 374–86.

  • Carmody, JB; Carmody, RB (December 2011). “Question from the clinician: management of prenatal hydronephrosis”. Pediatr Rev. 32 (12): e110–2.

  • Kay, Robert, M.D. “Evaluation of Hydronephrosis in Children” in Urology Secrets, 2nd Ed. by Resnick & Novick; 1999, Hanley & Belfus

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