Condition 101

What is the definition of Hydronephrosis?

Hydronephrosis is swelling of one kidney due to a backup of urine. This problem may occur in one kidney.

What are the alternative names for Hydronephrosis?

Hydronephrosis; Chronic hydronephrosis; Acute hydronephrosis; Urinary obstruction; Unilateral hydronephrosis; Nephrolithiasis - hydronephrosis; Kidney stone - hydronephrosis; Renal calculi - hydronephrosis; Ureteral calculi - hydronephrosis; Vesicoureteral reflux - hydronephrosis; Obstructive uropathy - hydronephrosis

What are the causes for Hydronephrosis?

Hydronephrosis (kidney swelling) occurs as the result of a disease. It is not a disease itself. Conditions that may lead to hydronephrosis include:

  • Blockage of a ureter due to scarring caused by prior infections, surgeries, or radiation treatments
  • Blockage from an enlarged uterus during pregnancy
  • Birth defects of the urinary system
  • Back flow of urine from bladder to kidney, called vesicoureteral reflux (may occur as a birth defect or due to an enlarged prostate or narrowing of the urethra)
  • Kidney stones
  • Cancers or tumors that occur in the ureter, bladder, pelvis or abdomen
  • Problems with the nerves that supply the bladder

The blockage and swelling of the kidney may occur suddenly or may develop slowly.

What are the symptoms for Hydronephrosis?

Common symptoms include:

  • Flank pain
  • Abdominal mass, especially in children
  • Nausea and vomiting
  • Urinary tract infection (UTI)
  • Fever
  • Painful urination (dysuria)
  • Increased urinary frequency
  • Increased urinary urgency

In some cases, there may be no symptoms.

What are the current treatments for Hydronephrosis?

Treatment depends on the cause of the kidney swelling. Treatment may include:

  • Placing a stent (tube) through the bladder and ureter to allow urine to flow from the kidney into the bladder
  • Placing a tube into the kidney through the skin, to allow the blocked urine to drain out of the body into a drainage bag
  • Antibiotics for infections
  • Surgery to correct the blockage or reflux
  • Removal of any stone that is causing blockage

People who have only one kidney, who have immune system disorders such as diabetes or HIV, or who have had a transplant will need treatment right away.

People who have long-term hydronephrosis may need antibiotics to reduce the risk of UTI.

What is the outlook (prognosis) for Hydronephrosis?

Loss of kidney function, UTI, and pain may occur if the condition is left untreated.

What are the possible complications for Hydronephrosis?

If hydronephrosis is not treated, the affected kidney may be permanently damaged. Kidney failure is rare if the other kidney is working normally. However, kidney failure will occur if there is only one functioning kidney. UTI and pain may also occur.

When should I contact a medical professional for Hydronephrosis?

Call your health care provider if you have ongoing or severe flank pain, or fever, or if you think you may have hydronephrosis.

How do I prevent Hydronephrosis?

Prevention of the disorders that cause this condition will prevent it from occurring.


Frøkiaer J. Urinary tract obstruction. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 37.

Gallagher KM, Hughes J. Urinary tract obstruction. In: Feehally J, Floege J, Tonelli M, Johnson RJ, eds. Comprehensive Clinical Nephrology. 6th ed. Philadelphia, PA: Elsevier; 2019:chap 58.

Latest Research

Latest Advance
  • Condition: Parapelvic Cavernous Hemangioma
  • Journal: BMC surgery
  • Treatment Used: DaVinci Robotic-assisted Surgery
  • Number of Patients: 1
  • Published —
In this case study, researchers evaluated the outcomes of undergoing a DaVinci robotic-assisted surgery for the treatment of a parapelvic cavernous hemangioma.
Latest Advance
  • Condition: Metachronous Upper Urinary Tract Urothelial Cancer (UUTUC)
  • Journal: BMC cancer
  • Treatment Used: Double J (DJ) stenting or Nephrostomy Placement During Transurethral Resection
  • Number of Patients: 637
  • Published —
This study evaluated the impact of double J (DJ) compared to nephrostomy placement during transurethral resection of a bladder tumor (TURBT) for bladder cancer (BCa) on the incidence of metachronous urinary tract urothelial cancers (UUTUCs).
Latest Advance
  • Condition: Diabetic Ketoacidosis Complicated by Emphysematous Pyelonephritis (EPN)
  • Journal: BMC urology
  • Treatment Used: Continuous Intravenous Infusion of Small Doses of Insulin and Antibiotic Treatment
  • Number of Patients: 1
  • Published —
This case report discusses a 34-year-old woman diagnosed with diabetic ketoacidosis complicated by emphysematous pyelonephritis (EPN) treated with continuous intravenous infusion of small doses of insulin and antibiotic treatment.

Clinical Trials

Clinical Trial
  • Status: Recruiting
  • Participants: 20
  • Start Date: July 9, 2019
Post-Marketing Follow-Up of Long-term Type Ureteral Stent Set
Clinical Trial
  • Status: Active, not recruiting
  • Study Type: Device
  • Participants: 170
  • Start Date: May 6, 2019
Hand-carried Ultrasound for Ruling Out Hydronephrosis in Acute Kidney Injury and Acute Kidney Disease
Clinical Trial
Diagnostic Test
  • Status: Recruiting
  • Study Type: Diagnostic Test
  • Participants: 1000
  • Start Date: October 20, 2017
Point-of-care Ultrasound in Finland