DUPLICATION ANOMALIES OF THE KIDNEYS 

Duplication anomalies are one of the most common congenital abnormalities of the urinary tract, occurring in 1% of live births (1).

80-93% are unilateral (1,2), the upper segment is involved in 85% of cases, and ureterocele is present in 24-47% of cases (3-5).
 

PATHOGENESIS

 

Link to Pathogenesis

 

 

ULTRASOUND



  • Vergani and co-workers suggest that there is no single ultrasonographic feature that is pathognomonic for the diagnosis. The diagnosis is based on a combination of ultrasound patterns (6). The three most significant signs are; eccentric hydronephrosis, ureterocele and ureteric dilatation.
  • Increased renal length in a sagittal plane (including the upper pole). ³ 95% for gestational age.
  • Kidney with two separate renal pelveses that do not communicate. Eccentric hydronephrosis, involving the upper pole in the majority of cases is present in up to 91% of cases (6). Concomitant hydronephrosis of the lower pole moiety may be present when a ureterocele draining the upper segment distorts the distal orifice of the lower renal segment (6).

 

Non-obstructed duplex collecting system

Obstructed upper pole moiety of a duplex collecting system

       ectopic ureterocele into urethra

(not demonstrated sonographically)

 

  • Obstruction of the upper pole moiety presents as a cyst like structure surrounded by a rim of renal parenchyma in the upper pole of the kidney.

 

Obstructed upper pole moiety of a duplex collecting system

 

 

  • Dilated ureter, usually draining the upper pole. (64% in reference 6). This is either due to stenosis at the ureterovesical junction or reflux.
  • The ureter may drain ectopically e.g. into urethra.
  • Ureterocele in the bladder. This may be found in 55% of cases (6).

 

Dilated ectopic ureter

Ectopic ureter

Ureterocele in bladder

Post-natal ultrasound of bilateral ureteroceles.

Note patency of both distal ureters (“ureteric jets” on color Doppler)

 

 

COMPLICATIONS

 

Link to Complications

 

 

 

REFERENCES

  1. Privett JTJ, Jeans WD, Roylance J. The incidence and importance of renal duplication. Clin Radiol 1976;27:521-530.
  2. Jee LD, Rickwood AMK, Williams MPL et.al. Experience with duplex system anomalies detected by prenatal ultrasonography. J Urol 1993;149:808.
  3. Winters WD, Lebowitz RL. Importance of prenatal detection of hydronephrosis of the upper pole. AJR 1990;155:125.
  4. Van Savage JG, Mesrobian HGJ. The impact of prenatal sonography on the morbidity and outcome of patients with renal duplication anomalies. J Urol 1995;153:768.
  5. Vergani P, Ceruti P, Locatelli A et.al. Accuracy of prenatal Ultrasonographic diagnosis of duplex renal system. J Ultrasound Med 1999;18:463-467.
  6. Abuhamad AZ, Horton Jr CE, Horton SH et.al. Renal duplication anomalies in the fetus: clues for prenatal diagnosis. Ultrasound Obstet Gynecol 1996;7:174-177.