Unusual ureteric duplication abnormality in a child with pelvoureteric junction obstruction

Abstract

A 5-year-old girl underwent an elective left pyeloplasty for pelvoureteric junction obstruction (PUJO). At laparoscopy, two ureters were seen to be draining a left duplex kidney, with a PUJO of the lower moiety. Interestingly, however, the upper moiety ureter was bifurcating to drain both upper and lower moiety as well. All the preoperative investigations were suggestive of a single system. The ureteric bifurcation of this type has not been reported so far. It is of paramount importance to demonstrate anatomy clearly at an operation to prevent risk to the less defined ureters.

Background

​This case demonstrates that despite advances in modern imaging and contrast studies that are used to plan for surgeries as well as anticipate possible complications, there can still be surprises at the time of operation.

​The variation of anatomy seen in this patient is unique, as this has never been reported in English literature.

Case presentation

A 5-year-old girl first presented with recurrent urinary tract infections.

A routine ultrasound scan of her renal tract at one of the acute episodes of urinary tract infection (UTI) showed a significant left pelvicalyceal dilatation (anterioposterior diameter of 27 mm and a large extrarenal pelvis measuring 48 mm) with no associated left hydroureter. She was discussed in the paediatric urology multidisciplinary team meeting and further imaging was requested. While she was awaiting further images, she represented with an episode of acute pyelonephritis and sepsis requiring an emergency left-sided nephrostomy. Her urine culture grew Pseudomonas aeruginosa that was fully sensitive. She was treated with 5 days of intravenous ceftazidime and then stepped down to oral ciprofloxacin. She was discharged home on a prophylactic dose of ciprofloxacin 95 mg, two times a day. At the time of discharge, she had a nephrostogram that confirmed a left pelvoureteric junction obstruction (PUJO) with no other abnormalities noted (figure 1). As the patient was very symptomatic, and the degree of dilatation was worsening, a dimercaptosuccinic acid (DMSA) scan was organised to document any function in the kidney. However, just prior to the DMSA scan, her nephrostomy fell out. She remained clinically well with no signs of infection; therefore it was decided to continue with the prophylactic antibiotics with no need for reinsertion of the nephrostomy. The DMSA scan showed a split function of 20% on the left and 80% on the right (figures 2 and 3). Unfortunately, on the day of her DMSA, she developed another UTI that was treated with further antibiotics. A pyeloplasty was planned for a week’s time after discharge following discussion with the family, as preoperatively, there was a high suspicion of PUJO from crossing vessels.

Figure 1.

Left nephrostogram showing hold up of contrast within the left kidney indicating a left PUJO. The nephrostomy tube is seen to be entering the lower pole moiety ureter. PUJO, pelvoureteric junction obstruction.

Figure 2.

DMSA scan showing isotope distribution between left and right kidneys. DMSA, dimercaptosuccinic acid.

Figure 3.

Computated interpretation of DMSA showing split function of left=20%, right=80%. DMSA, dimercaptosuccinic acid.

At transperitoneal laparoscopy, two ureters were seen draining the left kidney (figure 4). The lower moiety ureter was dissected which clearly demonstrated a PUJ obstruction from lower pole crossing vessels (figure 5). The upper moiety ureter was displaced significantly anteriorly as compared with its usual location to the lower moiety ureter. Interestingly, the upper moiety ureter was seen to bifurcate anteriorly to the level of the lower pole crossing vessels (figure 6). The upper limb of the upper moiety ureter was dissected cranially to demonstrate its attachment to the upper pole without compromising its blood supply. The lower limb of the upper moiety ureter was attached to the lower moiety. Figure 7 illustrates the overall picture seen at laparoscopy.

Figure 4.

Laparoscopic picture showing two ureters, one from the upper moiety and one for the lower moiety of the left kidney.

Figure 5.

​Laparoscopic picture showing crossing vessels in the previously identified pelvoureteirc junction obstruction.

Figure 6.

Laparoscopic picture showing bifurcation of the upper moiety ureter at the level of the crossing vessels.

Figure 7.

Illustrative drawing of intraoperative findings. Drawing by Mr Mohammad Bader, the operating surgeon.

Given that the crossing vessels were seen to be only interfering with the lower moiety ureter, the laparoscopic lower moiety pyeloplasty was performed. A nephrostent was left in situ which was clamped after 48 hours. The patient was discharged after 48 hours and was seen as a day case for removal of the stent without general anaesthetic. As the upper moiety ureter was not causing any problem, no further intervention was required.

The anatomy seen at laparoscopy was compared with a Smith’s type 2 ureteral triplication¹; however, this anatomical variant does not fit Smith’s classification. Specifically, this patient had a duplex system with an upper moiety bifid ureter with one ureter draining the upper moiety, and one ureter draining the lower moiety. We have explained the unique anatomical variation seen in this patient to her family who were in agreement to publish this case report.

The normal embryological pathway consists of a single ureteric bud that arises from the primitive mesonephros (Wolffian duct) after about 4 weeks of fetal development²; this then migrates to meet the primitive precursor of the kidney called the metanephros. At this meeting, usually between the sixth and eighth weeks of fetal life, there is what is called reciprocal induction whereby the ureteric bud signals the metanephros to begin forming nephrons (the parenchyma of the kidney), and in turn, the metanephros signals the ureteric bud to bifurcate sequentially to form a single renal collecting system. Anomalies in this pathway can therefore cause anatomical anomalies that may or may not be symptomatic, however, the main principle is that at least one ureteric bud must reach the metanephros in order for a kidney to be formed.

A duplex kidney occurs when either a bifurcated ureteric bud (incomplete ureteral duplication) or two separate ureteric buds (complete ureteral duplication) meet the metanephros.³ Each ureter leaving the kidney would therefore drain its own moiety in this instance.

In ureteric triplication, which is a very rare phenomenon,⁴ it is possible for three ureteric buds to arise from the Wolffian duct, or two ureteric buds could arise with one of these buds undergoing bifurcation. The four variations of ureteric triplication are described by Smith’s classification.¹

• Type I: completely separate ureters where all three ureters open into the bladder or one opening may be ectopic.

• Type II: double ureters with one bifid.

• Type III: trifid ureters with one ureteric orifice.

• Type IV: inverted Y formation of one ureter with a separate ureter.

With particular emphasis on a Smith’s type 2 ureteric triplication, the bifid ureters both drain a single moiety, with a third separate ureter draining the other moiety.^{5 6}

Our case is therefore unique in that the upper moiety bifid ureters do not drain the upper moiety exclusively (as in a Smith’s type 2 triplication), but rather the upper moiety ureter is seen to bifurcate with one ureter draining the upper moiety, and the other ureter draining the lower moiety. This is in addition to a separate third ureter that drains the lower moiety.

Still the PUJ obstruction was seen in the lower moiety ureter, which is a well-known phenomenon.

Interestingly, ureteric triplication occurs more commonly in women, and also on the left side, which is the case with our patient also.^{2 5}

As this is a unique anatomical variant that has not been previously seen, it is difficult to ascertain the embryological pathway that led to this outcome. However, we theorise that one possibility is that the patient had two ureteric buds arising from the Wolffian duct which we can call ureteric bud A, and ureteric bud B. Ureteric bud A underwent incomplete duplication resulting in ureteric bud A1 and A2. Ureteric bud A1 migrated to the metanephros and formed the upper moiety of the kidney. Ureteric bud A2 travelled with the separate ureteric bud B to meet the metanephros to form the lower moiety of the kidney.

Investigations

• Ultrasound renal tract

• DMSA scan

• Nephrostogram

• Laparoscopy

Treatment

• Left-sided lower moiety laparoscopic transperitoneal dismembered pyeloplasty.

• Prophylactic and treatment dose antibiotics.

• Nephrostomy.

Outcome and follow-up

A nephrostent was left in situ which was clamped after 48 hours. The patient was discharged after 48 hours and was seen in as a day case for removal of the stent without general anaesthetic.

The patient was seen at 3 and 6 months postlaparoscopic pyeloplasty with repeat ultrasound imaging that showed a significant reduction in the degree of dilatation. She has made a good recovery with no further UTIs. She is also currently awaiting a follow-up MAG-3 scan.

Discussion

After a PubMed search for ‘duplex’, ‘kidney’ ‘ureteric’, ‘bifurcation’, there was no other recorded cases demonstrating this anatomy in the English literature. Some reference could be taken to the classification put forward by Smith on ureteric triplication; however, this classification does not address duplex systems in the same way that was seen in our patient.

Learning points.

• This is a unique anatomical variant that has not been previously documented in English literature.

• There can still be unforeseen intraoperative findings despite extensive pre-operative imaging and planning which can cause difficulty with intraoperative decision making.

• Clear anatomical identification intraoperatively is imperative in order to minimise the risk of damaging the ureters.