Vol 44 # 4 December 2012 - Kma.org.kw

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327 Unusual Presentation of Duplex Collecting System: A Case Report December 2012 Fig. 1: Intravenous urography showing the upper and middle calyx of the right kidney displaced in an arc-like fashion, suggestive of a cyst / mass lesion Fig. 3: Reterograde pyelogram showing upper calyx of the right kidney to be arc-like. This is besides a faintly opacified grossly dilated pelvi-calyceal system inferior to the arched upper calyx. Fig. 2: NCCT scan showing a thick walled, lobulated cystic lesion with thin peripheral calcification and few internal septa in right kidney DISCUSSION Duplicated collecting systems (also known as duplex collecting systems) can be defined as renal units containing two pyelo-caliceal systems that are associated with a single ureter or double ureters. The prevalence of partial duplication found is 0.6% [2] . When a single ureteral bud bifurcates before the ampulla bifurcates, a duplex kidney with a bifid renal pelvis or bifid ureter results [1] . Fig. 4: Intra-operative image showing the lower system having a very short ureter along with obstruction of the pelvi-ureteric junction
December 2012 KUWAIT MEDICAL JOURNAL 328 Most patients are asymptomatic, with genitourinary tract abnormalities being detected incidentally on imaging studies performed for other reasons. Urinary tract infection and parenchymal scarring is increased in patients with a duplex collecting system; patients can present with pyrexia, pain and dysuria. Ureteropelvic junction obstruction is more common when a duplex kidney exists [2] . Giant hydronephrosis in a duplex kidney can manifest as an extremely large abdominal and retroperitoneal mass; in rare cases, it can cause hypertension. During ultrasonography, the duplex kidney appears as two central echo complexes with intervening renal parenchyma. Hydronephrosis at one pole is suggestive of a duplex kidney [3] . Although hydronephrosis can occur at either pole, it is more common in the upper one. The ultrasonographic appearance of a duplex kidney is specific but not sensitive. Differentiating an atrophied lower pole moiety of a duplex kidney (nubbin) from other renal masses is difficult [4] . With excretory urography, duplex kidney is usually longer than the non-duplex kidney. Calyces are asymmetric. Ectopic, upper pole ureteric insertion can produce a non-opacified segment. This mass effect results in the “drooping lily” sign with the depression of the lower pole pelvi-caliceal system. If the lower pole of the duplex kidney is functioning poorly or not at all, the lower pole collecting system may not opacify, and no discernible parenchyma will surround it (Nubbin sign). The appearance of the kidney may consequently resemble that of a non-duplex kidney with a lower polar mass or renal infarct. In computed tomography, the intervening renal parenchyma in a duplex kidney lacks a collecting system and major vessels. It is described as having a “faceless kidney” appearance, the collecting system in the nubbin or the mass effect of tissue at the pole [4] . Additional relevant findings include focal infarcts, cortical scars and atrophic scarred kidney. CT scan is superior to ultrasonography and excretory urography in diagnosing the lower pole nubbin [5] . In addition, the modality is helpful when function is poor or absent. CONCLUSION Careful history, examination and investigation may not rule out congenital abnormality of the kidneys like duplex collecting system. It may require a high index of suspicion as well as some invasive investigation to reach a final diagnosis. However, intra-operative findings can still surprise us with an entirely different diagnosis. REFERENCES 1. Bruno D, Delvecchio FC, Preminger GM. Successful management of lower-pole moiety ureteropelvic junction obstruction in a partially duplicated collecting system using minimally invasive retrograde endoscopic techniques. J Endourol 2000; 14:727-730. 2. Glassberg KI, Braren V, Duckett JW, et al. Suggested terminology for duplex systems, ectopic ureters and ureteroceles. J Urol 1984; 132:1153-1154. 3. Horst M, Smith GH. Pelvi-ureteric junction obstruction in duplex kidneys. BJU Int 2008; 101:1580-1584 4. Morgan CL, Grossman H, Trought WS, et al. Ultrasonic diagnosis of obstructed renal duplication and ureterocele. South Med J 980; 73:1016-1019. 5. Blair D, Rigsby C, Rosenfield AT. The nubbin sign on computed tomography and sonography. Urol Radiol 1987; 9:149-151.
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