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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.
Stricture or scarring
Bladder neck contracture
The inability to empty the bladder (urinary retention) for any reason may
cause bilateral hydronephrosis.
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.
Ovarian vein syndrome
Cancer of the cervix
Cancer of the prostate
Scarring due to radiation therapy
Prostate hypertrophy or swelling is a common cause of urinary retention and
subsequent hydronephrosis in males.
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
tumors, spinal cord injuries or tumors,
multiple sclerosis, and
Vesicoureteral reflux where urine flows backwards from the bladder into the
ureter. Prenatal hydronephrosis is an example, though it may occur at any time