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    Unilateral hydronephrosis

    Hydronephrosis; Chronic hydronephrosis; Acute hydronephrosis; Urinary obstruction

    Unilateral hydronephrosis is swelling of one kidney due to a backup of urine.

    See also: Bilateral hydronephrosis


    Hydronephrosis (kidney swelling)is a condition that occurs with a disease. It is not a disease itself. Conditions that are often associated with unilateral hydronephrosis include:

    • Acute unilateral obstructive uropathy
    • Blockage of a ureter due to scarring, tumor, urinary stones
    • Chronic unilateral obstructive uropathy
    • Vesicoureteric reflux (backflow of urine from bladder to kidney)
    • Nephrolithiasis (kidney stones)
    • Hydronephrosis that occurs without a known cause during pregnancy

    Unilateral hydronephrosis occurs in approximately 1 in 100 people.


    • Flank pain
    • Abdominal mass
    • Nausea and vomiting
    • Urinary tract infection
    • Fever
    • Painful urination (dysuria)
    • Increased urinary frequency
    • Increased urinary urgency

    Note: Sometimes unilateral hydronephrosis does not have symptoms.

    Exams and Tests

    Unilateral hydronephrosis is found on an imaging testsuch as:

    • Abdominal MRI
    • CT scan of the kidneys or abdomen
    • Intravenous pyelogram (IVP)
    • Isotope renography (kidney scan)
    • Ultrasound of the kidneys or abdomen


    Treatment and prognosis for unilateral hydronephrosis depend on what is causing the kidney swelling. Treatment may include:

    • A ureteral stent (tube that allows the ureter to drain into the bladder)
    • A nephrostomy tube (allows the blocked urine to drain through the back)
    • Antibiotics for infections

    Patients who have only one kidney, who have immune-compromising disorders such as diabetes or HIV, or who have received a transplant should be treated promptly.

    Preventative antibiotics may be prescribed to decrease the risk of urinary tract infections in patients who have long-term hydronephrosis.

    Outlook (Prognosis)

    Prolonged hydronephrosis results in the eventual loss of kidney function.

    Possible Complications

    If hydronephrosis is left untreated, the affected kidney may be permanently damaged. Kidney insufficiency or kidney failure is rare with unilateral hydronephrosis because the other kidney usually functions normally. However, if the patient has only one functioning kidney, kidney failure will occur.

    When to Contact a Medical Professional

    Call your health care provider if you have prolonged or severe flank pain, or if you suspect hydronephrosis.


    Prevention of the disorders associated with unilateral hydronephrosis will prevent this condition.


    Zeidel ML.Obstructive uropathy. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 125.

    SinghI, Strandhoy JW, Assimos DG. Pathophysiology of urinary tract obstruction. In: Wein AJ, ed.Campbell-Walsh Urology. 10th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 40.


    • Female urinary tract


    • Male urinary tract


      • Female urinary tract


      • Male urinary tract


      Tests for Unilateral hydronephrosis

        Review Date: 4/16/2012

        Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Louis S. Liou, MD, PhD, Chief of Urology, Cambridge Health Alliance, Visiting Assistant Professor of Surgery, Harvard Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

        The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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