November 24, 2015
font size

Hydronephrosis (cont.)

Medical Author:
Medical Editor:

What causes hydronephrosis?

There are numerous causes of hydronephrosis that are categorized based upon the location of the swelling and whether the cause is intrinsic (located within the urinary collecting system), extrinsic (outside of the collecting system) or if it due to an alteration in function.

Examples of intrinsic causes of hydronephrosis


  • Kidney stone. Likely the most common reason to have unilateral hydronephrosis is a kidney stone that causes obstruction of the ureter. The stone gradually moves from the kidney into the bladder but if it should act like a dam while in the ureter, urine will back up and cause the kidney to swell. This would be classified as an intrinsic obstruction.
  • Blood clot
  • Stricture or scarring



Examples of extrinsic causes of hydronephrosis


  • Tumors or cancers that compress the ureter and prevent urine flow. Examples include lymphoma and sarcoma, especially if they are located in the retroperitoneum, where the kidneys and ureters are located behind the sac that contains the bowel.
  • Retroperitoneal fibrosis
  • Ovarian vein syndrome
  • Cancer of the cervix
  • Cancer of the prostate
  • Pregnancy
  • Uterine prolapse
  • Scarring due to radiation therapy


  • Prostate hypertrophy or swelling is a common cause of urinary retention and subsequent hydronephrosis in males.
  • Prostate cancer

Examples of functional causes of hydronephrosis


  • Neurogenic bladder or the inability of the bladder to function properly occurs because of damage to the nerves that supply it. This may occur in brain tumors, spinal cord injuries or tumors, multiple sclerosis, and diabetes among other causes.
  • Vesicoureteral reflux where urine flows backwards from the bladder into the ureter. Prenatal hydronephrosis is an example, though it may occur at any time in life.
Medically Reviewed by a Doctor on 2/23/2015


Women's Health

Find out what women really need.

Use Pill Finder Find it Now See Interactions

Pill Identifier on RxList

  • quick, easy,
    pill identification

Find a Local Pharmacy

  • including 24 hour, pharmacies

Interaction Checker

  • Check potential drug interactions
Search the Medical Dictionary for Health Definitions & Medical Abbreviations