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A 74-year-old man presented with a 2-day history of severe, steady pain radiating down to the lower abdomen and left testicle. He has had urinary frequency, nocturia, hesitancy, and urinary dribbling for several years with slight worsening with time. CT scan revealed left-sided hydronephrosis (Figure 71-1). In this patient, an irregular mass was seen at the left ureterovesical junction compressing the bladder. Prostate cancer was found on biopsy.


Intravenous urogram showing left hydronephrosis and hydroureter. (Reproduced with permission from Schwartz DT, Reisdorff EJ. Emergency Radiology. New York, NY: McGraw-Hill Education; 2000.)


Hydronephrosis refers to distention of the renal calyces and pelvis of one or both kidneys by urine. Hydronephrosis is not a disease but a physical result of urinary blockage that may occur at the level of the kidney, ureters, bladder, or urethra. The condition may be physiologic (e.g., occurring in up to 80% of pregnant women) or pathologic.


  • Hydronephrosis with infection is also called pyonephrosis.


  • The most common cause of congenital bilateral hydronephrosis is posterior urethral valves (in males). Other causes include narrowing of the ureteropelvic or ureterovesicular junction.

  • Using a large European database for surveillance of congenital malformations (EUROCAT), authors found a prevalence of congenital hydronephrosis of 11.5 cases per 10,000 births; the majority (72%) was in males.1

  • Ureteropelvic junction obstruction is one of the most common congenital abnormalities of the urinary tract causing hydronephrosis, occurring in approximately 1 in 5000 to 8000 live births.2

  • Authors of one systematic review reported a mean prevalence of 15% for postnatal primary vesicoureteral reflux (VUR) in children after prenatally detected hydronephrosis.3 Of the remaining cases, 53% had no postnatal anomalies and 29% had other anomalies (e.g., duplicate collecting systems; Figure 71-2).

  • Among acquired causes in adults, pelvic tumors, renal calculi, and urethral stricture predominate.4 If renal colic is present, renal stone is likely present (90% in one study).5

  • Hydronephrosis is common in pregnancy because of the compression from the enlarging uterus and functional effects of progesterone.


Duplicate right ureter seen with three-dimensional rendering of a CT urogram. (Reproduced with permission from Karl T. Rew, MD.)


  • Bilateral hydronephrosis is caused by a blockage to urine flow occurring at or below the level of the bladder or urethra.

  • Unilateral hydronephrosis is caused by a blockage to urine flow occurring above the level of the bladder.

  • Multiple causes result in this condition including congenital (e.g., VUR), acquired intrinsic (e.g., calculi, inflammation, and trauma), and acquired extrinsic (e.g., pregnancy or uterine leiomyoma, retroperitoneal fibrosis). Within ...

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