Benjamin Wedro, MD, FACEP, FAAEM
Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.
Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
- What is hydronephrosis?
- What causes hydronephrosis?
- What are the symptoms of hydronephrosis?
- When should I seek medical care for hydronephrosis?
- How is hydronephrosis diagnosed?
- What is the treatment for hydronephrosis?
- What are the complications of hydronephrosis?
- Can hydronephrosis be prevented?
- Hydronephrosis At A Glance
- Patient Comments: Hydronephrosis - Treatment
- Patient Comments: Hydronephrosis - Cause
What is hydronephrosis?
Hydronephrosis describes the situation where the urine collecting system of the kidney is dilated. This may be a normal variant or it may be due to an underlying illness or medical condition.
Normally, the kidney filters waste products from blood and disposes of it in the urine. The urine drains into individual calyces (single=calyx) that form the renal pelvis. This empties into the ureter, a tube that connects the kidney to the bladder. The urethra is the tube that empties the bladder.
While obstruction or blockage is the most frequent cause of hydronephrosis, it may be due to problems that occur congenitally in a fetus (prenatal) or may be a physiologic response to pregnancy.
Technically, hydronephrosis specifically describes dilation and swelling of the kidney, while the term hydroureter is used to describe swelling of the ureter. Hydronephrosis may be unilateral involving just one kidney or bilateral involving both.
A complication of hydronephrosis is decreased kidney function. The increased pressure of extra fluid within the kidney decreases the blood filtration rate and may cause structural damage to kidney cells. This decrease in function is reversible if the underlying condition is corrected but if the hydronephrosis lasts many weeks, the damage may be permanent.
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
- The inability to empty the bladder (urinary retention) for any reason may
cause bilateral hydronephrosis.
- Urethral stricture
- Urethral valves
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
- 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
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 in life.
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