Distension and dilation of the renal pelvis and calyces, usually caused by obstruction of the free flow of urine.KidneyEncyclopedia Entry for Hydronephrosis :Hydronephrosis of one kidney. 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.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.The condition is found on an imaging test such as: MRI of the abdomen CT scan of the kidneys or abdomen Intravenous pyelogram (IVP) Kidney scan Ultrasound of the kidneys or abdomen.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.Loss of kidney function, UTI, and pain may occur if the condition is left untreated.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.Call your health care provider if you have ongoing or severe flank pain, or fever, or if you think you may have hydronephrosis.Prevention of the disorders that cause this condition will prevent it from occurring.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.Female urinary tract Female urinary tract Male urinary tract Male urinary tract.Fr kiaer J. Urinary tract obstruction.