Correspondence *Department of Urology, Box 43, Addenbrookes Hospital, Hills Road, Cambridge CB2 2QQ, UK

Email nimish.shah@addenbrookes.nhs.uk

The case

A 40-year old male was referred from a district general hospital with non-specific right-sided abdominal pain. Examination revealed tenderness in the right renal angle. Initial blood tests including full blood count, renal function and C-reactive protein level were all normal. An ultrasound performed at the referring hospital showed mild hydronephrosis in the right kidney and absent left kidney. A CT scan demonstrated ureteropelvic junction (UPJ) obstruction to the right kidney, with a lower pole crossing vessel as a probable contributing cause of obstruction to the UPJ (Figure 1).

Figure 1 A CT image showing the ureteropelvic junction with the lower pole-crossing vessel on the right side.

 

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The patient was discharged with outpatient investigations and follow-up planned, but was readmitted a few weeks later with similar pain. A subsequent ^99mTc-mercaptoacetyltriglycine (MAG3) scan confirmed UPJ obstruction in a solitary right kidney (Figure 2). On account of the patient's recurrent symptoms and the presence of significant UPJ obstruction, laparoscopic pyeloplasty was scheduled as an urgent elective procedure.

Figure 2 ^99mTc-MAG3 study shows a non-functioning left kidney.

The right kidney shows slow tracer uptake and virtually no excretion phase. Further, no tracer activity is visible beyond the ureteropelvic junction, suggesting outflow tract obstruction at this level. Abbreviation: MAG3, mercaptoacetyltriglycine.

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Laparoscopic pyeloplasty was performed using a transperitoneal approach. A crossing lower pole artery was confirmed intraoperatively. Dismembered Anderson–Hynes pyeloplasty was performed with preservation and posterior transposition of the crossing lower pole artery (Figures 3 and 4). A JJ stent was inserted in an antegrade fashion. The total operative time was 2 hours and intraoperative blood loss was less than 50 ml.

Figure 3 Laparoscopic view of the newly constructed ureteropelvic junction (Anderson–Hynes pyeloplasty) with the posteriorly transposed crossing vessel.

 

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Figure 4 Completion of the pyeloplasty with the transposed lower pole vessel (inferiorly) and the liver and perirenal fat (superiorly).

 

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The postoperative recovery was uneventful and the patient was discharged home on the third postoperative day. The JJ stent was removed using flexible cystoscopy at 4 weeks postoperatively. A MAG3 scan performed 3 months later showed a normal uptake and excretion pattern with resolution of the outflow tract obstruction (Figure 5). At 4-month follow-up, the patient was symptom free with no postoperative complications. A further MAG3 scan and an outpatient appointment was scheduled after 12 months.

Figure 5 The ^99mTc-MAG3 study shows normal tracer uptake and excretion consistent with normal function.

There is no current outflow tract obstruction. Abbreviation: MAG3, mercaptoacetyltriglycine.

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Discussion of diagnosis

A UPJ obstruction can be defined as a restriction to the flow of urine from the renal pelvis to the ureter that, if left uncorrected, will lead to progressive renal deterioration.¹

UPJ obstruction is the most common congenital abnormality of the ureter. Congenital causes of UPJ obstruction include a non-peristaltic segment of ureter or a true congenital stricture. Intrinsic obstruction may also occur due to valves or kinks produced by infoldings of the ureteral mucosa and musculature.

Aberrant or accessory lower pole vessels can cause extrinsic obstruction at the UPJ. Controversy persists regarding the potential role of aberrant vessels in the functional obstruction of UPJ. In many cases there can be an associated intrinsic lesion at the UPJ that causes dilatation and apparent ballooning of the renal pelvis over the polar vessel.¹ The incidence of crossing vessels as detected by Doppler ultrasound in kidneys with and without UPJ obstruction has been reported as 79% versus 39%, respectively.²

UPJ obstruction can also be caused by acquired lesions. These include benign tumors such as fibroepithelial polyps, urothelial malignancy, urolithiasis, and scarring or ischemia, which may result after inflammation or surgical intervention. In children, severe vesicoureteric reflux can result in secondary UPJ obstruction due to subsequent elongation and tortuosity of the ureter, which can cause kinking of the UPJ.¹

UPJ obstruction is often associated with other renal abnormalities such as contralateral renal agenesis as in the case described above. Other associations include duplication of the collecting system, renal ectopia, multicystic dysplastic kidney and horseshoe kidney. Bilateral UPJ obstruction occurs in 10–15% of cases.³

The widespread use of antenatal ultrasound has dramatically increased the detection rate of asymptomatic newborns with UPJ obstruction. UPJ obstruction can present clinically at any time up to adulthood even though it is generally a congenital problem. A frequent presentation in older children or adults is intermittent abdominal or flank pain, often associated with nausea and/or vomiting. The pain might become apparent during times of maximum diuresis such as after consumption of large volumes of fluid, especially alcohol.

Less common presentations include urinary tract infection (UTI), renal calculi or hematuria, which may occur after minor trauma. Azotemia may be the primary presentation in a small number of patients with bilateral obstruction or a single functioning kidney. In the case described above, renal function was normal despite the single kidney. Normal function might be explained by the intermittent and possibly partial nature of the obstruction.

UPJ obstruction is also increasingly an incidental finding in asymptomatic children or adults who undergo abdominal imaging for an unrelated reason.

Treatment and management

When UPJ obstruction is suspected, radiographic studies are required to give both anatomical and functional information. Ultrasonography and non-contrast CT are most commonly employed as the initial investigations, and these techniques demonstrate hydronephrosis with non-dilated ureter beyond the UPJ. The renal parenchyma may be thin if there has been irreversible impairment of function. Contrast CT and excretory urography with delayed imaging give more information on both obstruction and function of the kidney. It is also important to exclude other causes of obstruction such as malignancy or a calculus. Retrograde pyelography has been the procedure of choice, typically performed at the time of planned operation to confirm diagnosis and demonstrate the exact site and nature of obstruction and placement of a retrograde stent. To a large extent this has been superceded by CT for diagnostic purposes, as good quality contrast CT images, especially with 3D-reconstructive capabilities, can identify crossing vessels at the UPJ that may impact on the choice of surgical intervention, and exclude other causes.

Hydronephrosis in itself does not imply obstruction, and imaging with diuretic renography is important to confirm that obstruction is indeed present.⁴ The ^99mTc-labeled compound MAG3 is taken up by the kidney, and a gamma camera is used to detect the amount of compound in each kidney during its perfusion through the kidneys and subsequent excretion in the collecting system. With UPJ obstruction there is delayed excretion or 'washout' despite the administration of diuretic. This form of imaging has the added benefit of permitting estimation of divided function in the presence of two kidneys and is increasingly used as a diagnostic test for UPJ obstruction.

The main goals of treatment are the relief of symptoms and the preservation of renal function. Occasionally, in an asymptomatic individual with imaging that is equivocal for obstruction, careful observation with serial follow-up studies may be appropriate.

Initial management includes analgesia and treatment of UTI if present. In most cases the pain is intermittent, as described, or related to concomitant UTI. Investigation and treatment as an outpatient once the patient is clinically stabilized is, therefore, usually feasible. However, in cases of unremitting pain, urosepsis, renal stones or compromised renal function, temporary drainage with a percutaneous nephrostomy tube or cystoscopy and retrograde insertion of a JJ stent may be required until definitive surgical reconstruction can be performed.

The main surgical options for treatment of UPJ obstruction in a functioning kidney include open or laparoscopic pyeloplasty and endopyelotomy performed in an antegrade or retrograde fashion.

Open pyeloplasty has been the traditional gold standard, with long-term success rates of greater than 90%.⁵ Pyeloplasty can be performed using a variety of described techniques including the commonly used dismembered Anderson–Hynes pyeloplasty as in this case, which is accomplished by excising the abnormal UPJ segment with re-anastomosis of the ureter to the renal pelvis. Dismembered pyeloplasty allows for posterior transposition of crossing vessels and the reduction of redundant pelvis, but is not well suited to cases in which there is a lengthy stricture or a small, relatively inaccessible intrarenal pelvis. Non-dismembering procedures, which include the Foley Y-V pyeloplasty and Fenger plasty, are suitable in the absence of redundant pelvis, and the various flap techniques described can overcome relatively long areas of proximal ureteral narrowing. Several basic principles apply, whichever technique is employed. A successful outcome requires a widely patent, well-vascularized anastomosis performed in a watertight fashion and free of tension, with a funnel-shaped transition between the renal pelvis and the ureter.

Laparoscopic pyeloplasty was initially introduced by Schuessler et al. in 1993.⁶ Laparoscopy aims to duplicate the well-established principles of open surgery, which entails an initial longer operating time, but operating times become equivalent to an open procedure with experience. Numerous studies have shown equivalent success rates to open surgery but with the advantage of reduced morbidity without a flank incision, and with lower analgesic requirement and a shorter hospital stay.⁵ Conversion to open surgery is uncommon in experienced series (Table 1). Laparoscopic pyeloplasty can be performed using either a transperitoneal or retroperitoneal approach. The transperitoneal approach gives the advantage of a wider working space and allows for easier displacement of the ureter in the presence of an anterior crossing vessel, whereas the retroperitoneal approach allows for rapid access to the UPJ, and is our choice when performing non-dismembered pyeloplasty.

Table 1 Published major laparoscopic pyeloplasty series.

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One of the evolving techniques is robot-assisted laparoscopic pyeloplasty. The use of robotic arms with a greater degree of motion allows for easier intracorporeal suturing, which may be technically difficult for a novice laparoscopist.⁷ Short and intermediate term results are similar to laparoscopy without robot assistance, but the technique is less cost-effective.⁸

The technique of endopyelotomy is also a viable treatment option for UPJ obstruction. It can be performed in either antegrade or retrograde fashion using a variety of methods including electrocautery, the Acucise^® (Applied Medical Resources, Inc., Rancho Santa Margarita, CA) cutting balloon catheter, and the holmium laser. Success rates of 32–85% have been reported, which are generally lower than with open or laparoscopic pyeloplasty.⁹ There is a strong negative association between the presence of a crossing vessel and the success rate of endopyelotomy. Van Cangh et al. have shown that the success rate at 5-year follow-up in the presence of a crossing vessel was 39%, compared with 95% with no crossing vessel.¹⁰

A novel technique recently described is percutaneous endopyeloplasty. A vertical incision is made at the UPJ internally via a percutaneous nephrostomy tract. This incision is then closed horizontally by a Heineke–Mikulicz technique using a modified laparoscopic suturing device.¹¹ Initial studies have been promising (100% success in 15 patients with mean 11.6-month follow-up), but the procedure is technically difficult and longer-term data with a larger number of patients are required.¹²

Conclusions

Laparoscopic pyeloplasty is the evolving gold standard for UPJ obstruction, especially in the presence of crossing vessels. The long-term functional results are comparable to that of open surgery, and the laparoscopic technique has the advantage of being a minimally invasive procedure, resulting in shorter hospital stay and lower morbidity.

Acknowledgments

The authors would like to thank PM Ball, Senior Medical Artist, University of Cambridge for drawing Figure 4, and Dr K Balan, Consultant in Nuclear Medicine Department, Addenbrookes Hospital for his assistance with Figures 2 and 5.

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