Introduction

Duplication of the kidney with or without the ureter is reportedly the most common congenital anomaly of the kidney and the urinary tract (CAKUT). It has an incidence rate of 0.8% in the healthy adult population and 2–4% in patients investigated for urinary tract symptoms (1,2). In 40% of cases, the duplicate kidney moieties drain through separate ureters down to the urinary bladder as a complete duplex system, while in about 60% of cases the duplicate units fuse at a point to drain through a common ureter to the urinary bladder as a partial duplex system (3,4). It is possible for a complete duplex system to exist with a partial duplex system on the contralateral side in one individual, but such discordant bilateral duplications are rare.
Generally, duplex renal systems are asymptomatic and of no grave consequence, and so are underreported (2). However, a number of disorders requiring treatment have been observed in association with duplex systems: obstruction, reflux disease, and urinary stones are not peculiar to but may be commoner in duplex systems (1,2). With respect to obstruction, the upper moiety may be at a greater risk (5). We present a case of neglected obstructed upper moiety of a right partial duplex system in an adult female with a discordant bilateral duplex renal system. The University of Nigeria Teaching Hospital Bioethics Committee approved this report (NHREC/05/01/2008B-FWA000024581RB00002323), and written informed consent for this report was obtained from the index patient.
 

Case Report

Our patient was a 49-year-old woman who presented with a 10-year history of recurrent right flank pain. The pain was dull, intermittent, non-radiating, aggravated by coughing, and relieved temporarily by analgesics. She was able to perform her activities of daily living despite the episodes of pain. In addition, she experienced recurrent fever, but had no hematuria or flank swelling.
Clinical examination upon presentation revealed her body temperature was 36.5°C, blood pressure 110/80 mmHg, heart rate 72 beats per minute, and respiratory rate 20 cycles per minute. Renal angle tenderness and urine culture were positive, but her hemogram and serum levels of sodium, potassium, chloride, bicarbonate, and creatinine, as well as blood urea nitrogen levels were within normal limits. A transabdominal ultrasound scan showed bilateral duplex renal systems with hydroureteronephrosis of the right upper moiety. Computed tomography-urography corroborated the bilateral duplex renal systems with a grossly hydronephrotic, non-functioning, right upper renal moiety and a dilated right upper moiety ureter down to its fusion with the normal caliber lower moiety ureter just proximal to the urinary bladder. The left was a complete duplex system (Fig. 1).
Cystoscopy revealed normal bladder mucosa with a single right ureteric orifice and double left ureteric orifices, confirming a complete duplex system on the left and a partial duplex system on the right.
Surgical exploration showed the renal moieties on the right were within a single capsule (Fig. 2), supplied by single renal artery and vein. The hydronephrotic upper moiety was excised and the dilated upper moiety ureter was traced down to its fusion with the lower moiety ureter, ligated and excised. Histological report on the excised specimen (Fig. 3) was in keeping with the diagnosis. Her immediate postoperative period was uneventful. She has remained symptom-free for 2 years, and the other renal moieties have remained stable clinically.

Click to view figure 1

Click to view figure 2

Click to view figure 3

 

Discussion

Duplex renal system is a recognized developmental anomaly of the upper urinary tract. Usually asymptomatic and identified incidentally, it has no prognostic implications. However, when symptoms arise, they do so due to any or a combination of recognizable complications such as obstruction, reflux, and calculus formation, or of associated anomalies such as ureterocele and ectopic ureteric insertion (6).

Bilateral duplication of the renal system is less common than unilateral duplication, and a discordant bilateral duplication is even rarer (4,7). The index patient has a discordant bilateral duplication: while there is an asymptomatic complete duplex system on the left, the right has a symptomatic partial duplex system. This is in keeping with the hypothesis that the developmental processes culminating in duplication of the kidney and ureter are localized, though most probably on a background of chromosomal defect (8).

It has been noted that non-calculous ureteric obstruction in a duplex renal system tends to occur at the confluence of the ureters or at the level of the insertion of the ureter in the urinary bladder (5). Such persistent significant obstruction usually causes progressive proximal dilation. Yo-yo refluxing between the two units of a partial duplication can also result in progressive proximal dilation (9). Absence of contrast in the ureter draining the non-functional upper renal moiety in the index patient excludes significant duplicate ureteric yo-yo refluxing. The observed obstruction in this patient must have been of long standing considering the extent of destruction of the parenchyma of the corresponding renal moiety. Such late presentations with non-functioning corresponding renal moiety necessitating heminephrectomy have been reported in our environment, but in children (10). In the absence of any significant renal tissue in the grossly hydronephrotic upper renal moiety, excision of the redundant hydronephrotic sac with the dilated ureter poses no major challenge. Recommended, this procedure is better undertaken laparoscopically (11,12), but due to absence of facility and expertise, extraperitoneal open excision is the approach adopted in this case.

Unilateral duplex renal systems are reported more commonly in females (7,13). Bilateral duplex renal systems may also be commoner in females. When duplication occurs, observations suggest that the upper moiety may be at a greater risk of developing abnormalities than the lower moiety (5,12). Had the diagnosis been made earlier, this patient may have benefitted from dismembering of the duplicate ureter and insertion of the upper moiety ureter to the urinary bladder (5). However, late presentation to appropriate care due possibly to poor index of suspicion by primary healthcare providers resulted in this unfortunate complete renal moiety parenchymal loss.

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Conclusion

Hitherto asymptomatic duplex renal system may become symptomatic later in life. When identified without symptoms and without evidence yet of renal function compromise, the integrity of the renal moieties may have to be closely observed for life. Thorough assessment with a high index of suspicion is necessary in persons presenting with flank pains so as to promptly identify missed duplex renal systems, duplex system-associated disorders and thereby forestall the attendant renal moiety parenchymal loss.

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References

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