EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Objectives: The aim of this study was to evaluate the effects of 2 types of external ureteral stents on the number of urological complications after kidney transplant.

Materials and Methods: Data were retrospectively collected from 366 consecutive transplants performed between January 2013 and January 2015 in our hospital, in which an external ureteral stent was placed during surgery and removed after 9 days. Urological complications were defined as urinary leakage or ureteral stenosis requiring percutaneous nephrostomy placement.

Results: A total of 197 patients received a straight stent with 2 larger side holes (type A; 8F “Covidien” tube; Covidien, Dublin, Ireland) and 169 patients received a single J stent with 7 smaller side holes (type B; 7F “Teleflex” single J stent; Teleflex Medical, Athlone, Ireland). We found a significantly higher number of percutaneous nephrostomy placements with type A stents, with 34 (17%) versus 16 (9%) in type B (P = .030). Reason for percutaneous nephrostomy placement, occurrence of stent dysfunction, and need for early removal (< 8 days) were equal in both groups (P = .397), whereas incidence of rejection and urinary tract infection were higher in type B stent group. Patient and graft survival did not differ between the groups.

Conclusions: Use of the type B stent was associated with less urological complications compared with the type A stent.

Key words : Complications, Renal, Transplantation

Kidney transplant is the best and most cost-effective treatment for patients with end-stage renal disease, improving both quantity and quality of life for recipients.¹ Urological complications, such as urinary leakage and ureteral strictures, can compromise graft function and are associated with patient morbidity, mortality, prolonged hospital stay, and reinterventions.^2,3 Complication rates due to failure of the ureteroneocystostomy are reported to be up to 30% and usually occur within the first 3 months after transplant.^4,5 Radiologic or surgical reinterventions are often needed if urological complications do not dissolve spontaneously. A previously conducted randomized controlled trial showed that 20% of all kidney recipients required placement of a percutaneous nephrostomy (PCN) drain.⁶ Moreover, 5% of this cohort needed ureteral reintervention, including balloon dilatation or surgical revision of the ureteroneocystostomy.⁶

Several factors are presumed to influence the number of urological complications after kidney transplant, including preemptive transplants, male sex of recipient and donor, and the presence of multiple renal arteries.^7,8 Furthermore, ureteric stenting in renal transplant is still debated. Some studies suggest that prophylactic ureteral stent insertion may reduce the risk of urological complications such as ureteral strictures and leakages.^4,9,10 However, concerns have been raised regarding potential stent-related complications, such as urinary tract infections (UTI), stent breakage or migration, reflux, stone formation, hematuria, and secondary ureter obstruction.^4,11,12 Some centers, including ours, have a prophylactic stenting policy; however, in most centers, surgeons base their choice on earlier experiences, training, and personal preferences. The Cochrane review from Wilson and associates debates which stent caliber and stent duration is best for avoidance of urological complications. Although the type of stent was mostly similar (double J stent was used in all but 1 study), the time until stent removal diverged from 7 days until 3 months and stent caliber varied from 5F to 7F between all studies.⁴ To our knowledge, no studies have been published that compared the influence of different externalized ureteric stents on the number of urological complications in kidney transplant recipients.

In our center, we prefer the use of external stents over double J stents because of several advantages, such as the possibility of monitoring urine production and the simplicity of stent removal without a cystoscopy. Furthermore, we have no double J-related complications such as “the forgotten stent” or stent encrustation.^13,14 We have used 2 different types of external ureteral stents as standard care in the past years. As guidelines in literature are not equivocal, we conducted a database analysis to evaluate the outcomes of these 2 kinds of stents used during kidney transplant.

Materials and Methods

We included all patients who received a kidney transplant with an externalized stent from January 2013 to January 2015. We considered bilateral kidney transplants and pediatric kidney transplants as exclusion criteria. From January 2013 until January 2014, patients were treated with type A stents, and the following year until January 2015 patients were treated with type B stents. Type A stents refer to 8F “Covidien” polyvinyl chloride tubes (Covidien, Dublin, Ireland) and type B stents refer to 7F polyurethane “Teleflex” single J stents (Teleflex Medical, Athlone, Ireland) (Figures 1 and 2). Kidney donors were either deceased or living. Recipient characteristics, clinical information, and follow-up data were retrospectively obtained from electronic patient records. Data regarding graft function were limited to 6 months after transplant. Data regarding rejection episodes, PCN placement, and patient and graft survival were reviewed during complete follow-up (until July 2015). Graft failure was defined as patient’s return to hemo- or peritoneal dialysis, if graft nephrectomy was performed, or if the patients received a new preemptive kidney transplant. This study received approval from our center’s medical ethics committee.

Definitions
A UTI was defined as an infection of the urinary tract with a positive bacterial culture of the urine sample for which treatment with antibiotic therapy was given. Only UTIs within the first 3 months after surgery were considered. A urological complication was defined as urinary leakage or ureteral stricture requiring PCN placement; PCN placement is considered to be the first step in the treatment of urological complications. Percutaneous nephrostomy placement was indicated when postoperative ultrasonography revealed hydronephrosis in combination with a rising serum creatinine level or a perirenal urinoma indicating urine leakage, confirmed by ultrasonography or renal MAG-3 (radioisotope renography) scanning. Stents removed before day 8 were registered as dysfunctional.

Surgical procedure
If a kidney graft had multiple renal arteries, an arterial reconstruction was made. In the recipient, the renal vein was anastomosed to the external iliac vein and the renal artery to the external iliac artery. All patients underwent an extravesical Lich-Gregoir anastomosis of the ureter with the introduction of a suprapubic externalized stent. The stent was removed manually on postoperative day 9. A transurethral catheter in the bladder was left in situ until postoperative day 7. A wound drain was placed and removed after 1 or 2 days, depending on the amount of drain production.

Immunosuppressive regimen
Almost all patients received a similar immunosuppressive regimen. This included induction therapy with basiliximab (Simulect, Novartis Pharmaceuticals, Basel, Switzerland) and maintenance therapy with tacrolimus (Prograft, Astellas Pharma, Tokyo, Japan), mycophenolate mofetil (Cellcept, Roche, Basel, Switzerland), and glucocorticoids. On days 0 to 3, all patients received 50 mg prednisolone intravenously 2 times per day. Thereafter, 20 mg of oral prednisolone was started and subsequently tapered to 5 mg at month 3. On indication, a conversion of aforementioned immunosuppressive medications was performed in individual patients, such as additional antithymocyte globulin induction therapy or belatacept (Nulojix, Bristol Myers-Squibb, New York City, NY, USA) instead of tacrolimus.

Statistical analyses
All statistical analyses were performed with SPSS software (SPSS: An IBM Company, version 21.0, IBM Corporation, Armonk, NY, USA). Categorical variables are presented as numbers with percentages and analyzed using chi-squared test. Continuous variables with normal distribution are presented as means with standard deviation and analyzed using the independent t test. Skewed distributed variables are presented as median (range) and analyzed using the Mann-Whitney U test. Graft survival was analyzed using the Kaplan-Meier method, and a log-rank test was conducted to compare survival curves. Two-tailed P values of < .05 were considered statistically significant.

Baseline characteristics
Between January 2013 and January 2015, 370 patients received kidney transplants with external stenting at our hospital. Four patients were excluded from our study: 3 patients because of bilateral kidney transplant and 1 because of a pediatric kidney graft. Our cohort consisted of 197/366 patients (54%) receiving type A stenting and 169/366 patients (46%) receiving type B stenting. Our patient group comprised 230 male patients and 136 female patients. The mean age of recipients was 55 ± 15 years. Demographic details of kidney recipients, kidney grafts, and transplants are presented in Table 1. There were no significant differences between both groups, except for the length of follow-up.

Urological complications
In our patient group, 50/366 patients (14%) required PCN placement, in which 37 patients (10%) underwent a PCN placement due to hydronephrosis and 13 patients (4%) due to urinary leakage (Table 2).

The incidence of PCN placement was significantly higher with type A stenting (17% vs 9%; P = .030). Median time between transplant and PCN placement was 17 days (range, 2-190 d) and did not differ significantly between groups; reason for PCN placement also did not differ. Urinary tract infections within the first 3 months after transplant occurred more often in patients who received type B stenting (37% vs 26%; P = .034). Three patients with type A stenting and 2 patients with type B stenting underwent balloon dilatation of the strictured segment of the ureter. Open ureter revision was performed in 7 patients with PCN in type A stenting, with 5 due to hydronephrosis and 2 due to persistent urine leakage. Only 1 patient who had type B stenting underwent surgical ureter revision. This patient was clinically suspected to have an anastomotic leak and was not treated with PCN but underwent immediate ureter revision. In Table 3, the baseline characteristics of the patients who received a PCN are documented. As shown, there were significantly more patients who were transplanted in the left fossa and more patients who received a retransplant in the patient group with type A stent who received a PCN.

Stent-related complications
Ureteric stents were removed after a median of 9 days (range, 1-12 d) in patients with type A and type B stents (Table 2). Stents were equally often removed prematurely (< 8 d) in both groups (17% vs 13%; P = .261). No significant differences were found between the 2 groups regarding reason for early stent removal (hydronephrosis, obstruction, migration, spontaneously, early graft nephrectomy, or other) (P = .397).

Overall complications
Graft rejection occurred significantly more often in patients who received the type B stent than in patients who received the type A stent (37% vs. 22%; P = .002) (Table 2). Surgical reinterventions regarding the transplant were performed in 33 patients (including the previously mentioned 8 patients who underwent ureter revision) and occurred equally often in both groups (6% vs 3%; P = .055). Reasons for surgical reinterventions in the type A stenting group were graft nephrectomy, postoperative bleeding, venous thrombectomy, abdominal wall abscess, and retransplant. Reasons for surgical reinterventions in the type B stenting group were graft nephrectomy, postoperative bleeding, suspected necrotizing fasciitis, fascial dehiscence, abdominal wall hematoma, and incisional hernia. The incidence of surgical procedures not related to transplant, performed in the first year after transplant, was not significantly different between groups (11% vs 6%; P = .116).

Graft function and survival
Glomerular filtration rate and serum creatinine levels were not significantly different between the groups, except for month 6, which showed higher serum creatinine levels in the type B stenting group (median 135 vs 126 μmol/L; P = .030) (Table 4). As shown by the Kaplan-Meier curve, kidney graft survival did not differ significantly between the groups (P = .781) (Figure 3). The 3-month, 6-month, and 1-year graft survival rates in the type A stenting group were 97%, 96%, and 95%, with corresponding rates in the type B stenting group of 98%, 97%, and 95% (P = .781). The 3-month, 6-month, and 1-year patient survival rates in the type A stenting group were 99%, 98%, and 98%, with corresponding rates in the type B stenting group of 99%, 98%, and 95% (P = .093).

The aim of this retrospective study was to evaluate the influence of 2 different types of externalized ureteric stents (type A was an 8F polyvinyl chloride tube and type B was a 7F polyurethane single J stent) on the incidence of urological complications. We found a significantly higher incidence of PCN placements in patients who received the type A stent and a higher incidence of rejection and UTI in patients who received the type B stent. There were no significant differences in the reason for PCN placement or for patient or graft survival between both groups.

An explanation for the higher number of PCN placements in the type A stent group may be that this particular stent has fewer drainage holes and may therefore obstruct relatively easier. Obstructed stents can potentially cause a hydronephrosis of the kidney graft, necessitating PCN placement. However, as the median time between transplant and PCN placement was 17 days, stents were mostly already removed at the time of PCN placement. Furthermore, we found no differences between the groups regarding early stent removal due to stent obstruction. Another likely explanation for the higher number of PCN placements with type A stents could be its wider 8F caliber. This could potentially cause edema of the ureter after stent removal, which could explain a number of temporary PCN placements due to passing hydronephrosis without demanding an additional invention such as surgical reconstruction or balloon dilatation. It is possible that this larger caliber stent also caused transient ischemia of the ureter due to higher pressure on the ureteral wall, resulting in more ureteral stenosis requiring reinterventions. Although the number of surgical and balloon reinterventions was not significantly higher in type A stenting (P = .053), a trend can be detected in favor of type B stenting.

Urinary tract infections are common complications after kidney transplant with a reported incidence of 26% to 98%.^15-17 Although lower UTIs are often thought to be of a mild nature, some studies suggest that UTIs can contribute to the development of acute allograft rejection and possibly even compromise graft function in the short term.^18,19 The incidence of UTIs within the first 3 months after transplant in our study was higher in the type B stent group. This could not be explained by the type of stent material, as a study of Lopez and associates found that polyurethane catheters (stent type B) had lower Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa adherence compared with polyvinyl chloride catheters (our type A stent).²⁰ Another explanation for the higher number of UTIs could be the higher rejection rate shown in the group B stent patients. Acute rejection episodes are treated with high-dose immunosuppressive therapy, leading to increased risk of infections.²¹ Incidences of graft rejection might be increased during the past few years because of shifting boundaries for donor acceptance and because increasingly more ABO-incompatible transplants are being performed in our center.²² A causal association between stent material and rejection episodes seems highly unlikely.

One important limitation of this study was its retrospective design. Another drawback was the limited follow-up period, especially in patients who received the type B stent. However, the protective effects of the stent are expected to be the most significant during the first weeks after transplant.

To our knowledge, no other study has compared 2 different types of externalized ureteral stents used in kidney transplant. There are some studies available that have compared double J versus external ureteral stents. Vogel and associates retrospectively compared these 2 stents and concluded that the external stent had significantly more urinary leakage (14% vs 0%) and more hospitalization days for patients without immunological complications (13 vs 11 days).²³ Gomes and associates also found more urological complications with external stenting compared with double J stenting (17% vs 5%); however, this was also a retrospective study.²⁴ Another way of stenting the ureteroneocystostomy is by using an internal stent tied to a Foley catheter. This way, the stent is removed simultaneous during Foley catheter removal. This technique was described by Taghizadeh-Afshari and associates in 2014. They randomized 90 patients into 2 study groups, with 1 group having the stent attached to the Foley catheter and the group having these separated. They reported a urinary leakage rate of 3.3%, with all of these occurring in the separated stent group. Furthermore, they report 0% stent crustation in the attached group. However, a drawback of their study was the small sample size.²⁵ More prospective research is necessary to compare other ureteral stent types and to clarify which type of stent establishes the least number of urological complications and best renal outcome.

In conclusion, we found a significantly higher PCN placement rate in patients who received the type A stent versus that shown in patients who received the type B stent. The type B stent was associated with more UTIs and higher rejection rate compared with the type A stent, without influencing patient and graft survival.

Volume: 15 Issue: 2 April 2017

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