Effect of patient positioning on anesthesiologic risk in endourological procedures.

Objective: The objective is to compare supine and prone positions in terms of arterial blood gas during lithotripsy endourology procedures in different stages. Material and Methods: Cases of during lithotripsy endourology procedures in our department from March to September 2020 were included prospectively. The variables registered were body mass index, age, the American Society of Anesthesiologists (ASA) score, diabetes mellitus, positive end-expiratory pressure (PEEP), FiO2, stone size, stone location, procedural type, position, procedure duration, PaO2, SaO2, PaCO2, pH, and dynamic compliance. PaO2, SaO2, PaCO2, pH, and dynamic compliance were recorded at the beginning of the procedure, 5 min later, 15 min later, and at the end of the procedure. Results: Thirty patients in prone position and 30 in lithotomy position were included in this study. Patients in prone position underwent percutaneous nephrolithotomy, and patients in supine/lithotomy underwent retrograde intrarenal surgery or ureteroscopy. Statistically significant differences were found in PEEP, duration, PaO2 at the beginning, SaO2 at the beginning and at the end of the procedure, PaCO2 at the beginning and at minute 5 and pH at the beginning of the surgery. The saturation PaO2 increased significantly on prone position and was statistically significantly better at the end of the surgery. Conclusions: Both prone and supine positions were safe regarding anesthesiologic risk and had no clinically relevant differences in terms of individual comparisons in arterial blood gas parameters in static moments of the procedure. Prone position was related to an increase in PaO2 and a drop in PaCO2 gradually from the beginning to the end of the surgery.

Position-related anesthesiologic considerations and surgical outcomes of prone percutaneous nephrolithotomy: a review of the current literature.

The aim of the current study was to perform a critical review of existing literature and report the potential morbidity of patient positioning during urological surgeries as well as evaluate the surgical outcomes and anesthesiologic benefits and risks of prone percutaneous nephrolithotomy (PCNL). A narrative review of the current literature has been performed. Articles related to position-related injuries and complications under general anesthesia in prone positions were selected, studied, and considered for the current review. We found that under general anesthesia, the prone position improved the oxygenation of patients and increased the elimination of carbon dioxide. A potential risk for position-related anesthesiologic side effects was reported for longer spine surgeries in a prone position. The injuries and position-related side effects were extremely rare following prone PCNL since the mean duration of the procedure was significantly shorter than that of spine surgery. In conclusion, the prone PCNL remains the most often utilized and preferred approach globally with well-established success and complication rates. Clinical outcomes of prone PCNL do not demonstrate an increased rate of anesthesiologic complications compared to the supine approach. Standardization of turnover of the position, and reduction of the operative time warrant a faster and complication-free recovery.

Long-term outcomes of paclitaxel-coated balloons for non-malignant ureteral strictures.

PURPOSE: To evaluate the clinical efficacy and safety of drug-coated balloon (DCB) ureteroplasty for the management of non-malignant ureteral strictures. MATERIAL AND METHODS: A prospective "off-label" monocentric single-arm pilot study investigating the safety and efficacy of drug-coated balloon (DCB) (Lutonix®; BD, USA) was performed. Twenty-five patients with benign ureteral strictures related to uretero-enteric anastomosis (n = 13); lithiasis (n = 5), post-surgical complications (iatrogenic n = 5), transplanted kidney (n = 1) and post-radiotherapy (n = 1) were included. Following lesion crossing, predilatation was performed using 4-7 mm high-pressure balloon catheter (5-6Fr) with a balloon pressure of 6-7 atm based on the manufacturer's recommendation. In the absence of rupture of the ureteral wall, the DCB was dilated for 4 min. across the lesion. The process was repeated if deemed necessary to a maximum of three stricture dilatations. We analysed both clinical and radiological primary patency (no signs of ipsilateral hydronephrosis or improvement of the existing residual dilatation at the follow-up examinations) and secondarily safety endpoints. RESULTS: Mean lesion length was 40 ± 28.5 mm. Mean time follow up was 36 months ± 10.46 months. Strictures were located at upper ureteric (12%), lower ureteric (32%), ureterovesical anastomosis (4%) and uretero-enteric anastomosis (52%) levels. The overall radiological success at 1-year follow-up was 88% (22/25 patients). In 56% patients (14/25 patients with primary patency) the nephrostomy catheter was removed 21 days following a single DCB procedure. In 32% (8/25 patients) an additional dilatation sessions were required for maintaining the ureteral patency. The overall failure rate at 1-year follow-up was 12% (3/25 patients). Only one case of febrile urinary tract infection in a female patient (acute pyelonephritis) was encountered after the first dilatation. CONCLUSIONS: Paclitaxel-coated balloon ureteroplasty proved to be safe and effective for the treatment of non-malignant ureteral strictures. Larger studies are warranted to validate these promising initial results.

The use of 14/16Fr ureter access sheath for safe and effective management of large upper ureteral calculi.

OBJECTIVE: To evaluate the effectiveness of ureteroscopic lithotripsy for the management of large proximal ureteral stones > 10 mm using 14/16 Fr ureteral access sheath (UAS). MATERIALS AND METHODS: Patients' data from prospective database undergoing ureteroscopic laser lithotripsy with a use of 14/16Fr UAS were collected. All patients were pre-stented prior to the procedure. The fragmentation was performed with a semi-rigid ureteroscope using holmium laser energy with a power setting of 35 W (frequency-35 Hz; energy-1 J). Follow-up was scheduled at 4 weeks and 3 months postoperatively. RESULTS: In total 78 patients, 43 males and 35 females, were included in the study. The mean age of the patients was 59.5 ± 13.3 with a mean maximal stone diameter of 13.4 ± 2.1. The mean operative time was 35.7 ± 9.7 and the mean hospital stay was 2 ± 0.7 days. The primary SFR at 4 weeks was 73 patients (93.6%), while all 78 patients (100%) were stone free at 3-month follow-up, 2 of the patients receiving additional treatment. In total, 8 (10.2%) patients experienced Grade II complications. Intraoperative ureteral lesions were observed in 41 (52.6%) cases. Out of them 31 patients (39.7%) developed Grade 1, 8 patients (10.3%) Grade 2 and only 3 patients (2.6%) Grade 3 lesions. CONCLUSION: The use of 14/16Fr ureteral access sheath on pre-stented patients was associated with successful outcomes. A high stone-free rate of 93.6% was achieved at 4-week follow-up. The procedure was not associated with increased rate of postoperative complications and intraoperative ureteral injury.

Does ureteral access sheath have an impact on ureteral injury?

OBJECTIVE: To present a well-organized review about ureteral access sheath impact on ureteral injury. MATERIALS AND METHODS: Systemic search on literature was done. Total of 3766 studies observed by two urologists and results were unified. A Prisma diagram was used for eliminating irrelevant studies and at the end of elimination process 28 studies were found eligible for this review. RESULTS: Not only clinical studies but also comparative experimental animal studies show that there is no significant data to claim that ureteral access sheath insertion causes more ureteral injury. Pre-stented patients were found to be at lower risk for ureteral injury. Risk of progression to ureteral injury seems to be low even if ureteral injury occurs with insertion of ureteral access sheath. CONCLUSION: Summary of studies' results indicate that use of ureteral access sheath doesn't increase ureteral injury. This review may help understanding safety profile of ureteral access sheath on evidence-based level. There is not enough data to make a statement that ureteral access sheath prevents ureteral injury.

Could the High-Power Laser Increase the Efficacy of Stone Lithotripsy During Retrograde Intrarenal Surgery?

Objective: To compare a high-power setting in holmium: yttrium-aluminum-garnet laser lithotripsy with the established low-power setting approach during retrograde intrarenal surgery (RIRS). Materials and Methods: Our study analyzed the data of consecutive patients managed with RIRS. The patients were divided into two groups according to the employed laser settings of power, energy, and frequency; dusting (20 W = 0.5 J × 40 Hz) (group 1) and stone self-popping (60 W = 1.5-2 J × 30-40 Hz) (group 2). Perioperative outcomes, including operative time (OT) and stone disintegration time (SDT), were compared between groups. The stone-free rate (SFR) was evaluated 1 month after the surgery. Results: Overall, 174 patients with 179 renal units were included. The dusting mode was utilized in 98 patients (100 renal units), whereas 76 patients (79 renal units) underwent the stone self-popping technique. The SFR was 82.1% for both groups. The OT and SDT were 60.1 ± 18.6 and 32.6 ± 9.4 minutes, respectively, for group 1 and 44.9 ± 15.5 and 16.5 ± 4.7 minutes, respectively, for group 2. According to the final analysis, laser lithotripsy using the stone self-popping technique was significantly faster compared with the dusting technique with coefficient values of 14.12 minutes (95% confidence interval [CI] = 8.8-19.44) and 15.84 minutes (95% CI = 13.44-18.2) for OT and SDT, respectively. Conclusions: The stone self-popping technique with power at 60 W, frequency at 30 to 40 Hz, and energy at 1.5 to 2.0 J is a safe and effective modality for active treatment of renal stones. In comparison with the dusting mode, it resulted in significantly faster procedures (14.12 minutes) with similar SFRs.

Stone ablation rates using innovative pulse modulation technology: Vapor tunnel, virtual basket, and bubble blast. An in vitro experimental study.

INTRODUCTION AND OBJECTIVES: Virtual BasketTM , Bubble BlastTM , and Vapor TunnelTM are three laser pulse modulation technologies that modify the holmium: yttrium-aluminum-garnet (Ho:YAG) laser pulse transmission through the creation of bubbles emerging from the fiber tip with different effects on the target stone. The primary outcome of the current study was to test the stone ablation rates for the different pulse modulation modes, Virtual Basket, Bubble Blast, and Vapor Tunnel, using different power, energy, and frequency settings. MATERIALS AND METHODS: Quanta Cyber: Ho 150 WTM , a 365 µm PrecisionTM fiber, and hard and soft phantom BegoStonesTM were used in an in vitro experimental configuration in a saline bath. In the Virtual Basket mode, the combinations of power, energy and frequency were tested; 10 W = 0.5 J × 20 Hz, 10 W = 0.5 J × 20 Hz, 60 W = 1 J × 60 Hz and 60 W = 2 J × 30 Hz. In the Bubble Blast mode, the combinations, 12 W = 1.2J × 10 Hz, 60 W = 1.2J × 50 Hz and 60 W = 2 J × 30 Hz, were tested. Similarly, the combination of 10 W = 0.5 J × 20 Hz was tested with Vapor Tunnel mode. High-speed camera captures of the bubble formation and regular photographs of the fragmentation pattern were also taken for each mode. RESULTS: High power lithotripsy was faster and related to higher ablation rates. The Virtual Basket, Bubble Blast, and Vapor Tunnel modalities showed different ablation rates for the same energy and frequency settings. For hard stones, there was an improvement in the ablation rate using 60 W = 2 J × 30 Hz compared with 60 W = 1 J × 60 Hz and 60 W = 1.2 J × 50 Hz. The highest ablation rates were recorded using the Virtual Basket mode with the high-power settings of 2 J of energy and 30 Hz of frequency. CONCLUSIONS: The Virtual BasketTM pulse-modulation technology was related to the highest ablation rates for both hard and soft stones, compared to the Bubble BlastTM and the Vapor TunnelTM technologies in high-power and low-power lithotripsy respectively. For the same high power settings, higher energy seems to provide higher ablation rates.

The use of ureteral access sheath during mini-percutaneous nephrolithotomy with high-power holmium YAG laser.

PURPOSE: To present our preliminary results and describe a technical modification of mini-PCNL (12Fr) with the insertion of a ureteral access sheath (UAS) to facilitate the procedure. METHODS: A prospective study for the time period of January 2020 to January 2021 was conducted including patients with renal stones sized ≤ 25 mm in whom prone mini-PCNL (tract size 12Fr) together with the retrograde insertion of UAS was performed. All patients had been prestented at least 1 week prior to the planned surgery. A single-step tract dilation to 12Fr diameter was performed through a nonpapillary medial puncture. The lithotripsy was achieved using high-power holmium yttrium aluminum garnet laser (Ho:YAG) with the 60 W power setting (40 Hz and 1.5 J). The follow-up investigations were planned at 1-month after the surgery. RESULTS: In total, 32 patients with the median age and stone size of 56.5 (IQR = 53-62) years and 20.8 (IQR = 19.3-22.7) mm were included. The median operative and cumulative fluoroscopy time were 34.0 (IQR = 29.9-37.5) and 1.9 (1.8-2.1) min, respectively. The stone-free rate (SFR) at 1-month follow-up was 93.8% (30/32). Only one patient developed a fever and required prolonged antibiotic administration. None of the patients experienced clinically significant bleeding. CONCLUSION: Our preliminary results showed that the use of UASs during mini-PCNL procedures is feasible and provides directed evacuation of the stone fragments reaching 93.8% SFR at a 1-month follow-up. Future well-designed studies are necessary to prove our findings.

The best treatment approach for lower calyceal stones ≤20 mm in maximal diameter: mini percutaneous nephrolithotripsy, retrograde intrarenal surgery or shock wave lithotripsy. A systematic review and meta-analysis of the literature conducted by the European Section of Uro-Technology and Young Academic Urologists.

INTRODUCTION: The highest in quality data in the literature which compared mini percutaneous nephrolithotripsy (mPCNL), retrograde intrarenal surgery (RIRS) and shock wave lithotripsy (SWL) for the management of lower pole stone (LPS) with a maximal diameter ≤20 mm were investigated by means of systematic review (SR) and meta-analysis. EVIDENCE ACQUISITION: A SR of the literature was conducted on PubMed, Cochrane, SCOPUS and EMBASE in January 2020. The study complied with the PRISMA statement and recommendations of the EAU Guidelines office. Only randomized controlled trials (RCTs) comparing retrograde intrarenal surgery (RIRS), shock wave lithotripsy (SWL) and mini-percutaneous nephrolithotripsy (mPCNL) were selected for the meta-analysis. The endpoints were the efficacy of each modality, measured by stone-free rate (SFR), operative time and retreatment rate and the safety of each method, based on hospitalization time and complications. Subgroup analyses for stones with a maximal diameter <10 mm and 10-20 mm were performed. EVIDENCE SYNTHESIS: Twenty-one RCTs were included in the meta-analysis. mPCNL had the highest SFR and the lowest retreatment rate among the three modalities, while SWL had the lowest SFR and the highest retreatment rate. The operative and hospitalization time were shorter in the case of SWL, whereas they were similar in the case of mPCNL and RIRS. The highest complication rate was observed in mPCNL group, which accounted for 8.3-22.4%, while RIRS and SWL had similar complication rates, which ranged between 1.3-31.4% and 0-48.5%, respectively. Further classification of the complications according to Clavien-Dindo system revealed that SWL had lower grade II complication rates compared to mPCNL and RIRS. Regarding stones <10 mm, SWL and RIRS had similar SFR, complication rate, operation and hospitalization time. SWL had higher retreatment rate. CONCLUSIONS: For LPSs ≤20 mm, mPCNL provides the highest SFR and the lowest retreatment rate. This modality has a higher complication rate and longer hospital stay in comparison to the other modalities. SWL provides the lowest SFR with the highest retreatment rate. RIRS has similar complication rate to SWL and could be preferred over SWL. For stones up to 10 mm, SWL may provide a valid alternative. Despite a higher retreatment rate, its SFR is similar to RIRS.

Drug-delivering devices in the urinary tract: A systematic review.

OBJECTIVE: : To systematically review the use of drug-eluting stents (DES) and drug-coated balloons (DCB) in urology. MATERIALS AND METHODS: The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Scopus, Web of science and Cochrane Library online databases were searched in February 2019. Experimental and clinical studies, which included the placement of a DES or dilatation with DCB for investigating their potential use in the urinary tract for the management of ureteric or urethral pathologies, were included. The primary endpoint was to evaluate the current use of DES and DCB in urology. RESULTS: A total of 29 articles were included in the systematic review. A total of 10 studies tested DES or DCB containing anti-proliferative agents (paclitaxel, zotarolimus, sirolimus, halofugione). Antibiotic agent-containing DES were tested in nine studies (triclosan, quinolones, teicoplanin, nitrofurantoin, silver sulfadiazine). A total of eight studies investigated the release of anti-inflammatory agents by DES (ketorolac, indomethacin, EW-7197). Another group studied heparin-eluting stents. CONCLUSION: Despite the inconclusive outcomes of the three randomised controlled trials, drug-coated/eluting devices constitute a promising field in urology for the prevention of complications associated with conventional stents including pain and encrustation. Pre-clinical in vitro and in vivo studies have shown their ability to mitigate inflammation, inhibit re-stenosis and improve pain as indicated by declined use of anti-inflammatory drugs.Abbreviations: DES: drug-eluting stents; DCB: drug-coated balloons; DCS: drug-coated stents; HF: halofungione; MCP-1: monocyte chemoattractant protein 1; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses; PTCA: percutaneous transluminal coronary angioplasty; RANTES: regulated on activation, normal T-cell expressed and secreted; RCT: randomised controlled trial; USSQ, Ureteric Stent Symptoms Questionaire.

Comparative Evaluation Between One Ultrasonic and Two Single-Probe Dual-Energy Lithotripters: In Vitro and In Vivo Experiment in a Porcine Model.

Objective: To investigate the efficiency of three advanced lithotripters during the treatment of artificial stones (hard and soft) in an experimental in vitro and in vivo setting. Materials and Methods: An experimental configuration was created to treat artificial stones, made from BegoStone Plus in a weight ratio of 15:3 or 15:6 powder to water, replicating hard and soft urinary stones, respectively. Experimental data of three lithotripters, the Lithoclast Master, the Lithoclast Trilogy, and the ShockPulse-SE, were assessed. Experiments aimed at comparing the stone clearance times (SCTs) of the devices as well as different probe diameters, probe disposability, and hardness of the stones. The in vivo experiment was performed in a porcine model after the approval from the State Services. Before in vivo lithotripsy, stones had been placed through percutaneous access established by using the Bull's eye technique. The SCT between the Lithoclast Trilogy and the ShockPulse-SE was compared. Results: All the devices were statistically more efficient in the treatment of soft stones in both in vitro (p < 0.001) and in vivo settings (p < 0.008). The use of larger-diameter probes resulted in shorter SCT (p < 0.007). The disposable probes of the ShockPulse-SE showed higher performance than the multiple-use probes (p < 0.05). In the direct comparison between the devices, the Lithoclast Trilogy was found to be the fastest during all the in vitro (p < 0.001) and in vivo (p < 0.008) trials. Conclusion: Modern dual-energy lithotripters proved to possess high performance in the treatment of stones. Faster SCTs were observed by using the larger-diameter and disposable probes. The Lithoclast Trilogy was superior in terms of SCT over all the experimental settings compared with other lithotripters.

Non-papillary percutaneous nephrolithotomy for treatment of staghorn stones.

BACKGROUND: The aim of this study was to evaluate the non-papillary puncture for Percutaneous Nephrolithotomy (PCNL) for the treatment of staghorn stones in terms of safety and efficacy. METHODS: Data of 53 patients undergoing PCNL for staghorn stones were retrospectively collected from January 2015 to December 2019. A non-papillary puncture was performed with a two- step track dilation technique up to 30Fr. A 26 Fr semirigid nephroscope and an ultrasonic lithotripter with integrated suction (Swiss Lithoclast master, EMS S.A, Nyon, Switzerland) were used for the treatment. Demographics and perioperative data were retrospectively gathered from an institutional board approved database. RESULTS: The average stone size was 60.1±16.1 mm. Mean operative time was 54.57±14.83 minutes, while mean time using fluoroscopy was 2.67±1.02 minutes. Mean number of accesses was 1.2 (a total of 64 accesses). Flexible nephroscope was never used. Primary stone-free rate after PCNL was 81.1% (43 patients). Mean hemoglobin drop was 1.6±1.86 gr/dL. Overall patient stay was 3.94±0.82 days, while overall complication rate was 20.7% (11 patients), with only one patient requiring blood transfusion due to pseudoaneurysm. CONCLUSIONS: The use of non-papillary access for PCNL in the treatment of staghorn stones resulted in promising results in terms of stone-free rate, operating time, complication rate, hemoglobin drop and reduced the number of percutaneous tracts. These parameters of the current investigation were directly comparable to current literature. The safety and efficacy of a non-papillary approach for the treatment of staghorn stones could be advocated.

Pneumococcal Otogenic Meningitis Complicated With Pneumocephalus and Coma State.

We herein describe the unusual case of a male patient with pneumococcal otogenic meningitis, which was complicated with non-traumatic pneumocephalus and coma, in the absence of head trauma or a neurosurgical procedure. The initiation of an aggressive, empirical scheme with wide-spectrum antibiotics was achieved to stop the progression of meningitis, pneumocephalus, and their underlying causes in this patient. We propose pathogenetic mechanisms to explain this life-threatening condition.

Evaluation of the Distribution of Paclitaxel After Application of a Paclitaxel-Coated Balloon in the Rabbit Urethra.

INTRODUCTION: Urethral strictures are a common urologic problem that could require complex reconstructive procedures. Urethral dilatation represents a frequent practiced intervention associated with high recurrence rates. Drug-coated percutaneous angioplasty balloons (DCBs) with cytostatic drugs have been effectively used for the prevention of vascular restenosis after balloon dilatation. To reduce restenosis rates of urethral dilatation, these balloons could be used in the urethra. Nevertheless, the urothelium is different than the endothelium and these drugs may not be distributed to the outer layers of the urethra. Thus, an experiment was performed to evaluate the distribution of paclitaxel (PTX) in the rabbit urethra after the inflation of a PTX-coated balloon (PCB). MATERIALS AND METHODS: Eleven rabbits underwent dilatation of the posterior urethra with common endoscopic balloons after urethrography. Nine of these rabbits were additionally treated with PCB. The urethras of the two control animals were removed along with three more dilated with PCB urethras immediately after the dilatation. The remaining of the urethras were removed after 24 (n = 3) and 48 hours (n = 3). The posterior segments of the urethras were evaluated with hematoxylin and eosin staining as well as with immunohistochemistry with polyclonal anti-PTX antibody. RESULTS: The two control specimens showed denudation of the urothelium after balloon dilatations and no PTX was observed. All specimens from dilated PCB urethras showed distribution of PTX to all layers of the urethra. The specimens that were immediately removed exhibited denudation of the urothelium without any inflammation. The specimens removed at 24 and 48 hours showed mild acute inflammation. CONCLUSION: PTX was distributed to the urothelial, submucosal, and smooth muscle layers of the normal rabbit urethra immediately after dilatation with a DCB. PTX and mild inflammation were present at the site 24 and 48 hours after the dilatation.

Evaluation of the distribution of Paclitaxel by immunohistochemistry and nuclear magnetic resonance spectroscopy after the application of a drug-eluting balloon in the porcine ureter.

BACKGROUND AND PURPOSE: The urothelium represents "the tightest and most impermeable barrier in the body." We investigated the distribution of paclitaxel (PTX) in the ureteral wall after the inflation of a paclitaxel-eluting balloon (PEB) in an attempt to elucidate the possibility of clinical application of PEBs in the ureter. MATERIALS AND METHODS: Nine domestic pigs were used. Nine PEBs and nine conventional percutaneous angioplasty balloons (CB) were inflated in the right and left ureter of each animal, respectively. The ureter treated by CB was the control for the contralateral ureter. Specimens were removed: Immediately after inflation (group A), after 12 hours (group B), and after 24 hours (group C). Two samples were obtained from each ureter of groups A, B and C. One sample was investigated by nuclear magnetic resonance spectroscopy (NMR), the other by histology and immunohistochemistry (IHC) using a specific for PTX polyclonal antibody. RESULTS: Reduced inflammation was observed in the group B and C samples in comparison with their controls. PTX was distributed mostly in the urothelium and submucosal layer in group A (IHC). The agent was present in the urothelial, submucosal, and muscle layer in groups B and C. The concentration of PTX (NMR) has been reduced in group C compared with the tissue extracts of group B. CONCLUSION: The distribution of PTX includes the urothelial, submucosal, and smooth muscle layers. Inflammation was reduced in the case of drug-eluting balloons.

Evaluation of zotarolimus-eluting metal stent in animal ureters.

BACKGROUND AND PURPOSE: Drug-eluting stents proved to minimize neointimal hyperplasia in coronary vessels. Hyperplastic reaction is the most common unwelcome event related to the use of metal mesh stents in the ureter. We evaluated the effect of zotarolimus-eluting stent (ZES) Endeavor Resolute in the porcine and rabbit ureter. MATERIALS AND METHODS: A ZES and a bare metal stent (BMS) were inserted in each ureter of 10 pigs and 6 rabbits. The insertion was performed by the retrograde approach. CT was used for the evaluation of porcine ureters while intraoperative intravenous urography (IVU) was used for rabbit ureters. The follow-up included CT or IVU every week for the following 4 weeks for pigs and 8 weeks for rabbits. Renal scintigraphies were performed before stent insertion and during the third week in all animals. Optical coherence tomography (OCT) has been used for the evaluation of the luminal and intraluminal condition of the ureters with stents. Histopathologic examination of the these ureters embedded in glycol-methacrylate was performed. RESULTS: Hyperplastic reaction was present in both stent types. BMSs in seven porcine ureters were completely obstructed while porcine ureters with ZES stents had hyperplastic tissue that did not result in obstruction. Two rabbit ureters with BMS stents were occluded while no ZES was associated with ureteral obstruction. The function of the seven porcine renal units and the two rabbit units with obstructed ureters with stents was compromised. The OCT revealed increased hyperplastic reaction in the ureters with BMS stents in comparison with those with ZESs. Although, hyperplastic reaction was present in all cases, pathologic examination revealed significantly more hyperplastic reaction in BMSs. CONCLUSION: ZESs in the pig and rabbit ureter were not related to hyperplastic reaction resulting in stent occlusion. These stents were related to significantly lower hyperplastic reaction in comparison with BMSs while inflammation rates were similar for both stent types.