Hydronephrosis

  • Medical Author:
    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.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    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.

Hydronephrosis facts

  • Hydronephrosis describes swelling of the kidney resulting from the inability of urine to drain from the kidney into the bladder.
  • Hydroureter describes swelling of the ureter, the tube that connects the kidney to the bladder.
  • The obstruction may occur at any level in the urinary collecting system from the kidney to the ureter to the bladder to the urethra.
  • Depending on the level of the cause, hydronephrosis may be unilateral involving one kidney or bilateral involving both.
  • The increased pressure caused by hydronephrosis potentially can compromise kidney function if it is not relieved in a reasonable period of time.
  • Symptoms of hydronephrosis depend upon whether the swelling occurs acutely or progresses more gradually. If it is an acute obstruction, symptoms may include writhing pain, nausea, and vomiting.
  • Treatment of hydronephrosis and hydroureter is aimed at restoring urine flow from the affected kidney.

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.

Picture of the kidney and urinary system
Picture of the kidney and urinary system

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. A large percentage of pregnant women develop hydronephrosis or hydroureter. Experts think this is, in part, because of the effects of progesterone on the ureters, which decreases their tone.

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 that is not physiologic 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 often reversible if the underlying condition is corrected but if the duration is prolonged, the damage is often permanent.

Medically Reviewed by a Doctor on 9/2/2016

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