Radiology Resident Case of the Week
Clinical Sx:
Complete duplication of the ureter is the most common anomaly of the urinary tract. Patients with compete duplication of the ureter may be asymptomatic or present with symptoms that develop as complications of reflux into the lower-pole. These patients may also present with obstruction of the upper pole or a narrowed distal ureter with an ectopic orifice (dribbling of urine).
Embryology: In the normal development of the kidney, one ureteral bud arises from the wolffian duct to form a single ureter. If two buds develop from the wolffian duct a duplex kidney with complete ureteral duplication results.
Etiology/Pathophysiology
Pathology:
Miscellaneous
Imaging
Intravenous Urography. A duplex kidney is nearly always longer than the opposite (normal) kidney. This difference can be as much as 3 cm. However, normal kidneys may differ in size. The left kidney may be up to 2 cm larger than the right in 80% of normal adults. The right kidney may be up to 1.5 cm larger than the left in 20% of adults. The calyces of a duplex kidney are asymmetric in comparison with the calyces of the opposite (normal) kidney. The upper pole ureter has an ectopic distal insertion at a point lower and more medial than the lower pole ureter. The lower pole ureter inserts at the normal site in the trigone of the bladder. The upper pole ureter is susceptible to obstruction by either an aberrant artery crossing its ureteropelvic junction or as a complication of its ectopic insertion into the bladder. Ureteroceles are often seen associated with the upper ureter insertion point. Contrast can be seen in both collecting systems on these images. The presence of a ureterocele is also evident at the upper ureter insertion into the bladder.
Scintigraphy. Scintigraphy can perform two functions in the case of a complete duplication of the ureter: (1) it can confirm the diagnosis if adequate visualization of the dual collecting systems has not been achieved (unable to perform an adequate intravenous urogram or unclear sonography), or if scintigraphy is the first exam it can lead to the diagnosis. The appearance of two clearly recognizable collecting systems on the same side can be seen.
DDX
Duplex kidney with single ureter (Bifid system) - two pyelocalyceal systems that join at the ureteropelvic junction (bifid pelvis) or two pyelocalyceal systems each with a single ureter that join before emptying into the bladder (bifid ureters).
Key references
1. Pollack, Howard ed. Clinical Urography. Philadelphia: W.B. Saunders Company, 1990.
2. Barbaric, Zoran. Principles of Genitourinary Radiology. New York: Thieme Medical
Publishers, 1991. 3. Glassberg K, Braren V, Duckett J, et al. Suggested terminology for duplex systems, ectopic ureters and ureteroceles. J Urol 1984;132:1153-1154
4. Bellah R, Long F, Canning D. Ureterocele Eversion with Vesicoureteral Reflux in Duplex Kidney. AJR 1995;165:409-413
5. Daniels M, Allen T. Unsuspected ureterocele and ureteral duplication. J Urol 1994;152:179-181
6. Fernbach S, Zawin J, Lebowitz R. Complete Duplication of the Ureter with Ureteropelvic Junction Obstruction of the lower pole of the Kidney. AJR 1995;164:701-704
ACR Code
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