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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 |
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).
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Non-obstructed duplex collecting system |
Obstructed upper pole moiety of a duplex
collecting system –
ectopic ureterocele into urethra (not demonstrated
sonographically) |
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- 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.
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Obstructed
upper pole moiety of a duplex collecting system |
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- 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).
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Dilated ectopic ureter |
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Ectopic ureter |
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Ureterocele in bladder |
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Post-natal ultrasound of bilateral
ureteroceles. Note
patency of both distal ureters (“ureteric jets” on color Doppler) |
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COMPLICATIONS |
REFERENCES |
- Privett JTJ, Jeans WD, Roylance J. The incidence and importance of renal duplication. Clin Radiol 1976;27:521-530.
- Jee LD, Rickwood AMK, Williams MPL et.al. Experience with duplex system anomalies detected by prenatal ultrasonography. J Urol 1993;149:808.
- Winters WD, Lebowitz RL. Importance of prenatal detection of hydronephrosis of the upper pole. AJR 1990;155:125.
- 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.
- Vergani P, Ceruti P, Locatelli A et.al. Accuracy of prenatal Ultrasonographic diagnosis of duplex renal system. J Ultrasound Med 1999;18:463-467.