EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Ureteral obstruction is one of the most common urological complications after kidney transplant. The definitive treatment of ureteral obstruction has been surgical revision. Because of the increased morbidity of surgery, minimally invasive percutaneous procedures have gained more acceptance in recent years. Presently, interventional radiological procedures are recommended as the first step in treatment of ureteral obstructions. Ureteral occlusions or near-occlusion high-grade stenoses require greater catheter backup force. Antegrade interventions generally prefer upper-to-middle calyx puncture. Cranial/superior proximal ureter stenoses cause severe angulations. Steep angulations of proximal ureter and ureteropelvic tight stenoses may require direct puncture of the renal pelvis or another calyx to achieve a less difficult angle. The double-puncture technique may help to manage severe angulations of proximal ureter and near-occlusion tight stenosis of the ureteropelvic junction.

Key words : Stent, Ureter

Ureteral obstruction is the most common urological complication after renal transplant.¹ The most common site of obstruction is the ureterovesicular anastomosis.^2-4 Ureteropelvic strictures are less common, and treatment of these strictures is more difficult. The definitive treatment of ureteral obstruction has been surgical revision.⁵ As a result of the high risk of morbidity associated with surgery, minimally invasive percutaneous procedures have gained acceptance in recent years. Presently, interventional radiological procedures are recommended as the first step in treatment of ureteral obstructions.⁶

A 22-year-old woman with renal failure received a kidney transplant from a living donor (her mother). We used a multiple-stitch technique (Lich-Gregoir) to implant the ureter to the bladder. Renal allograft function after transplant was normal for the first 3 weeks. After the first 3 weeks, blood urea nitrogen increased to 108 mg/dL and creatinine level was 5.26 mg/dL. Diagnostic ultrasonography imaging revealed hydronephrosis without ureteral dilatation. Native ureter ureteropelvic reimplant was performed as a definitive reconstructive surgery.

Two weeks after surgical revision, ureteral obstruction recurred. Primary management with percutaneous nephrostomy enabled urinary drainage and rapid recovery of renal function. Antegrade nephrostograms confirmed stenosis at the ureteropelvic junction. Reobstruction was successfully managed with antegrade ureteral stent placement. The patient was followed up with stent replacement.

Twelve months later, retrograde double J stent replacement failed, and the patient was referred to the interventional radiology unit. After we accessed the upper pole calyx under ultrasonography guidance, we placed a 6-French (6F) sheath into the renal pelvis. An antegrade pyelogram revealed high-grade stenosis at the ureteropelvic junction and absence of effective peristalsis. The ureteral stump was successfully passed with a 0.035-in hydrophilic guidewire (ZIPwire, Boston Scientific) and a 5F multipurpose diagnostic Bern catheter (Boston Scientific). After we reached the bladder, a 0.035-in diameter 180-cm guidewire (Amplatz Super-Stiff, Boston Scientific) was advanced into the bladder. Over the guidewire, stenotic segments of the ureter were dilatated for 3 minutes with a 5 × 60-mm balloon dilatation catheter (Mustang, Boston Scientific) followed by placement of an 8F 35-cm nephroureterostomy catheter (multiple side-hole biliary drainage catheter; Flexima, Boston Scientific).

After 1 week, ureteral stenosis was dilatated with a 6 × 60-mm balloon dilatation catheter (Mustang, Boston Scientific), and an 8F 22-cm double J stent (Flexima, Boston Scientific) was placed antegrade.

Stent replacement was scheduled in 12 months, to avoid the risk of encrustation and stent dysfunction. The double J stent was retrieved by a cystoscopy-assisted retrograde approach, but retrograde ureteral catheterization and stent replacement failed for a second time. The patient was redirected to an interventional radiology unit for antegrade double J stent placement. We gained access via a percutaneous ultrasonography-guided upper calyx approach. Antegrade pyelogram revealed excessive hydronephrosis, and we did not observe contrast media in the ureter. We placed an 8F nephrostomy catheter in renal pelvis. Kidney functions were secured, and decompression of calyceal dilatation was ensured. Via the nephrostomy access, we placed a 6F sheath through the upper calyx; control pyelogram revealed a suspicious stump of the ureteropelvic junction (Figure 1). We attempted to cross the occlusion with a 5F multipurpose catheter and a 0.035-in hydrophilic guidewire; however, these manipulations failed. We used a coaxial 2.7F microcatheter and microwire coaxial catheter system (Progreat, Terumo) supported with a 5F multipurpose catheter combination to advance the guidewire to the proximal ureter. However, because of the upper pole approach, acute angulations, and tight stenosis, we were not able to advance the combination guidewire-catheter into the bladder.

Another calyx with an appropriate angle was punctured under ultrasonography guidance, and a 5F sheath was placed over the wire (Figure 2). A suitable direct approach enabled us to use the same catheter and coaxial microcatheter combination to obtain sufficient support to successfully catheterize the ureter and reach the bladder. The microwire was replaced by a 0.018-in stiff guidewire (V-18 ControlWire, Boston Scientific), and the 5F multipurpose catheter was advanced over the wire and into the bladder (Figure 3). After placement of a 0.035-in guidewire (Amplatz Super-Stiff), ureteral balloon dilatation was performed with a 5 × 60-mm balloon catheter. Then, a 20-cm 8F double J stent was inserted from pelvic puncture site; however, the proximal loop of the double J stent did not form properly because of the short length of the tract. To mitigate the risk of distal migration, we used grasping forceps via the upper pole access to catch and form the proximal loop (Figure 4). For safety reasons, an 8F nephrostomy catheter was placed and removed 1 day after the control nephrostogram.

On follow-up, the patient had no urinary symptoms or stent migration. No infections were recorded. For the next 6 months, renal functions remained stable (creatinine level was around 1.6 mg/dL) with mild hydronephrosis.

After kidney transplant, ureteral stricture incidence is between 1% and 4.5%. Ureteral obstruction leads to graft dysfunction. Surgical technique, retrieval technique, age, donor type, history of acute rejection, and type of immunosuppressive therapy comprise the etiology of obstruction.⁷ Because of the denervation of the transplanted kidney, symptoms are frequently unremarkable, which may lead to delayed diagnosis. Decreased urine output and increased creatinine level are early warning signs. After diagnosis of hydronephrosis, immediate placement of a nephrostomy catheter should be the primary treatment option to preserve kidney functions.

The definitive treatment of ureteral obstructions is reconstructive surgery. However, immunosuppressive therapy commonly causes fibrosis and loss of capsular vessels, which increase the difficulty of surgical revisions.⁸ In our case, the patient had reconstructive surgery; however, stenosis reoccurred in 3 weeks. Retrograde endoscopic approach failed, and hence the antegrade approach was the sole treatment option. The ureteral stent was placed with a percutaneous antegrade intervention (Figure 5). Despite the long-term follow-up with a double J stent, obstruction reoccurred and the retrograde stent replacement procedure failed again. Steep angulation of the proximal ureter and orifical preocclusive stenosis prevented our attempts to pass the catheter into the bladder. Another access point provided a proper angle and sufficient support for the catheter and guidewire combination. Close proximity of the puncture location and the ureteropelvic junction created difficulty for the task of shaping the proximal loop of the double J stent (Figure 3). The problem was managed by catching the proximal loop of the stent with forceps and pulling the stent through to the upper calyx (Figure 4 and Figure 5).

Retrograde replacement of double J stents may fail in up to 25% of cases with ureteral obstructions.⁹ In our experience, if the retrograde stent procedure fails once, then subsequent stent replacements must be via an antegrade approach. Ureteral occlusions or near-occlusion high-grade stenoses require greater catheter backup force. For antegrade interventions, we generally prefer upper-to-middle calyx puncture. Proximal ureter stenosis may cause detrimental angulations. Steep cranial angulations of proximal ureter and ureteropelvic tight stenoses may require direct puncture of the renal pelvis or another calyx to achieve a suitable angle. The double-puncture technique is a useful method with which to manage severe/hostile angulations of proximal ureter and near-occlusion tight stenosis of the ureteropelvic junction. Antegrade ureteral stent placement may fail in some cases. The extra-anatomic stent technique can be used as a salvage treatment. However, it is a difficult technique, and surgical skills are required.¹⁰ We suggest that our double-puncture technique will facilitate success in the cases of long-segment tight stenosis, steep angulation of ureteropelvic junction, and tortuous ureters. The double-puncture technique preserves the native ureter passage; also, it is a safer procedure compared with extra-anatomic stent placement. A disadvantage of the double-puncture technique is the higher risk of vascular injury; however, this problem can be mitigated by ultrasonography-guided puncture.

Volume: 20 Issue: 10 October 2022

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