Pathophysiological aspects of ureterorenoscopic management of upper urinary tract calculi

Clinical Efficacy Evaluation of a Novel Negative Pressure Ureteroscopic Lithotripsy for Ureteral Stones

OBJECTIVE

To evaluate the clinical efficacy of a novel negative pressure ureteroscopic lithotripsy (NP-URL) compared to standard ureteroscopic lithotripsy (S-URL) for treating ureteral stones.

METHODS

A total of 284 patients diagnosed with ureteral stones and who underwent ureteroscopic lithotripsy between December 2020 and May 2022 at our hospital were included in the study. Among them, 146 cases underwent NP-URL and 138 cases underwent S-URL. The negative pressure device used in NP-URL consists of a 5F ureteric catheter and a tee joint. We evaluated the operative duration, stone-free rate, incidence of postoperative complications, stone retropulsion rate, and adjunct procedure rate between the two groups.

RESULTS

The mean operative duration was significantly shorter in the NP-URL group compared to the S-URL group (30.17 ± 5.84 minutes vs 34.84 ± 6.62 minutes; P＜.05). Additionally, the NP-URL group had a lower incidence of postoperative fever (1.4% vs 8.7%; P＜.05), reduced stone retropulsion rate (3.4% vs 11.6%; P＜.05), and a statistically lower rate of adjunct procedures (5.5% vs 14.5%, P＜.05). The NP-URL group also demonstrated a higher primary stone-free rate (91.8% vs 81.9%; P＜.05). However, there was no significant difference in the final stone-free rate between the NP-URL and S-URL groups (P＞.05).

CONCLUSION

NP-URL potentially reduces operative duration, significantly decreases the incidence of postoperative complications, and achieves better primary stone-free rates compared to S-URL.

How to measure intra-renal pressure during flexible URS: Historical background, technological innovations and future perspectives

INTRODUCTION

High intrarenal pressure (IRP) is a potential risk factor for infectious complications related to URS. Methods to lower IRP have been described. However, it is still not possible to assess live IRP values during URS. The objective of this study was to perform a systematic review of the literature regarding endoscopic methods to measure IRP during URS.

METHODS

A systematic search and review of Medline, PubMed and Scopus was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta Analysis (PRISMA) checklist and a narrative synthesis of the study results was performed.

RESULTS

A total of 19 articles were included in the review. Four non invasive (i.e. endoscopic) methods to measure IRP were reported: ureteral catheter, sensor wire, pressure sensor proximal to an irrigation system and a novel ureteral access sheath that integrates suction, irrigation, and IRP measurement.

CONCLUSIONS

We provide here a comprehensive overview of the reported clinical measuring systems of IRP during URS. The ideal system has not been developed yet, but urologists will be able to measure IRP during their daily practice soon. The implications of having this type of data during surgery remains unknown. Systems that could integrate irrigation, suction, IRP and temperature seems to be ideal.

Clinical application of novel integrated suctioning semi-rigid ureteroscopic lithotripsy

INTRODUCTION

Urinary calculi are frequently encountered in urology. Traditionally, the lack of a perfect water injection and drainage system means the observation field is affected during ureteroscopy. Here, we explored the effect and clinical value of a new integrated suctioning semi-rigid ureteroscopic lithotripsy (URSL) for treating ureteral calculi.

MATERIAL AND METHODS

A total of 180 patients were successfully enrolled in this study (60 in each group). Group A included patients who underwent a traditional semi-rigid URSL, group B included patients who underwent a suctioning semi-rigid URSL with a sheath being connected to a vacuum device, and group C included patients who underwent a new type of suctioning integrated rigid URSL with a novel designed ureteroscope.

RESULTS

In total, 164 cases of URSL were completed in one stage. Compared with group A, group C had a higher stone-clearance rate at 30 days postoperatively, shorter operation time, and fewer hospitalization days (p < .05); compared with group B, group C had a higher one-stage operation success rate, shorter operation time, and fewer hospitalization days (p < .05).

CONCLUSIONS

Comparatively, the new suctioning integrated semi-rigid URSL is advantageous for treating upper urinary calculi, considering the reduced operation time, length of hospital stay, and low invasiveness.

In vivo ureteroscopic intrarenal pressures and clinical outcomes: a multi-institutional analysis of 120 consecutive patients

OBJECTIVES

To evaluate the pressure range generated in the human renal collecting system during ureteroscopy (URS), in a large patient sample, and to investigate a relationship between intrarenal pressure (IRP) and outcome.

PATIENTS AND METHODS

A prospective multi-institutional study was conducted, with ethics board approval; February 2022-March 2023. Recruitment was of 120 consecutive consenting adult patients undergoing semi-rigid URS and/or flexible ureterorenoscopy (FURS) for urolithiasis or diagnostic purposes. Retrograde, fluoroscopy-guided insertion of a 0.036-cm (0.014″) pressure guidewire (COMET™ II, Boston Scientific, Marlborough, MA, USA) to the renal pelvis was performed. Baseline and continuous ureteroscopic IRP was recorded, alongside relevant operative variables. A 30-day follow-up was completed. Descriptive statistics were applied to IRP traces, with mean (sd) and maximum values and variance reported. Relationships between IRP and technical variables, and IRP and clinical outcome were interrogated using the chi-square test and independent samples t-test.

RESULTS

A total of 430 pressure traces were analysed from 120 patient episodes. The mean (sd) baseline IRP was 16.45 (5.99) mmHg and the intraoperative IRP varied by technique. The mean (sd) IRP during semi-rigid URS with gravity irrigation was 34.93 (11.66) mmHg. FURS resulted in variable IRP values: from a mean (sd) of 26.78 (5.84) mmHg (gravity irrigation; 12/14-F ureteric access sheath [UAS]) to 87.27 (66.85) mmHg (200 mmHg pressurised-bag irrigation; 11/13-F UAS). The highest single pressure peak was 334.2 mmHg, during retrograde pyelography. Six patients (5%) developed postoperative urosepsis; these patients had significantly higher IRPs during FURS (mean [sd] 81.7 [49.52] mmHg) than controls (38.53 [22.6] mmHg; P < 0.001).

CONCLUSIONS

A dynamic IRP profile is observed during human in vivo URS, with IRP frequently exceeding expected thresholds. A relationship appears to exist between elevated IRP and postoperative urosepsis.

Timing of midstream urine culture before endourological procedure-can we do better?-A comparative study

Endourological procedures are the mainstay of treatment for stone disease in the upper urinary system. Infection is a common complication, and urine cultures (UC) are often obtained preoperatively. In this study, we sought to investigate the role of positive UC in the 90 days prior to surgery (90PreOp) in predicting postoperative infectious complications in comparison to a single positive preoperative UC (PreOP). We compared the correlation between positive PreOp UCs and positive 90PreOp UCs with postoperative urosepsis, and a positive UC obtain proximal to obstruction (Prox UC) during percutaneous nephrolithotomy, ureteroscopy and a placement of nephrostomy tube or ureteral stent. Data from 140 consecutive patients were collected. PreOp UCs were positive in 15 (11%) of patients versus 31 of 140 (22%) positive 90PreOp UCs. All six sepsis events had a positive 90PreOp UC, and five had a positive PreOp UC. Fourteen (93.3%) out of 15 positive Prox UC had a positive 90PreOp UC, whereas only 7 (38.9%) had a positive 90PreOp UC. Positive 90PreOp UC outperformed PreOp UC in predicting positive Prox UC, OR = 12.8 (95% CI 3.70-44.30, p < 0.001), versus OR of 88.9 (95% CI 11.0-720.7, p < 0.001); sensitivity 93%(95% CI 68-100%) versus 47%(95% CI 21-73%); as well as area under the ROC curve(AUC), 0.90 (CI 0.80-0.95) for 90PreOp versus 0.70 (CI 0.56-0.82) for positive Prox UC. Uropathogen persistence was better identified when using 90PreOp UC (27%) than using PreOp UC (12%). We suggest reviewing UCs taken within 90 days preoperatively as this was found superior to a single preoperative midstream UCs in predicting postoperative infectious sequela after stone procedure.

Effect of outflow resistance on intrarenal pressure at different irrigation rates during ureteroscopy: in vivo evaluation

To maintain visualization and control temperature elevation during ureteroscopy, higher irrigation rates are necessary, but this can increase intrarenal pressure (IRP) and lead to adverse effects like sepsis. The IRP is also dependent on outflow resistance but this has not been quantitatively evaluated in a biological system. In this study, we sought to characterize the IRP as a function of irrigation rate in an in vivo porcine model at different outflow resistances. Ureteroscopy was performed in a porcine model with a 9.5 Fr prototype ureteroscope containing a pressure sensor. A modified ureteral access sheath (UAS) (11/13 Fr, 36 cm) was configured to adjust outflow resistance. IRP-irrigation rate curves were generated at four different outlet resistances representing different outflow scenarios. At lower irrigation rates, the pressure change in response to increased irrigation was gradual and non-linear, likely reflecting a "compliant" phase of the renal collecting system. Once IRP reached the range of 35-50 cm H2O, the pressure increased in a linear fashion with irrigation rate, suggesting that the distensibility of the collecting system had become saturated. The relationship between IRP and irrigation rate becomes linear during in vivo porcine studies once the initial compliance of the system is saturated. IRP is more sensitive to changes in irrigation rate in systems with higher outflow resistance. The modified UAS is a novel research tool which allows variance of outflow resistance to mimic different clinical scenarios. Knowledge of outflow resistance may simplify the decision to use an UAS.

A Prospective Study of Renal Blood Flow during Retrograde Intrarenal Surgery

(I) Introduction: The use of Doppler ultrasound allows us to indirectly assess the effect of increased intrarenal pressure on renal blood flow during retrograde intrarenal surgery (RIRS). On the basis of vascular flow spectra from selected blood vessels in the kidney, it is possible to determine Doppler parameters that reflect the renal perfusion status, which indirectly shows the degree of vasoconstriction and reflects the resistance of kidney tissue. (II) Materials and methods: A total of 56 patients were included in the study. The study assessed the changes of three Doppler parameters of intrarenal blood flow: resistive index-RI, pulsatility index-PI, and acceleration time-AT in the ipsilateral and contralateral kidneys during RIRS. The effects of mean stone volume, energy used, and pre-stenting were examined as predictors and calculated at two time intervals. (III) Results: The mean value of RI and PI was significantly higher in the ipsilateral kidney than in the contralateral kidney just after RIRS. The mean value of the acceleration time was not significantly different before and after RIRS. The values of all three parameters 24 h after the procedure were comparable to their values immediately after the RIRS. The size of the stone exposed to laser lithotripsy, the value of the energy used, and pre-stenting are not factors that significantly influence Doppler parameters during RIRS. (IV) Conclusions: The significant increase in RI and PI after RIRS in the ipsilateral kidney suggests a vasoconstriction of the interlobar arteries generated by increased intrarenal pressure during the procedure.

Gadolinium-enhanced MRI visualizing backflow at increasing intra-renal pressure in a porcine model

INTRODUCTION

Intrarenal backflow (IRB) is known to occur at increased intrarenal pressure (IRP). Irrigation during ureteroscopy increases IRP. Complications such as sepsis is more frequent after prolonged high-pressure ureteroscopy. We evaluated a new method to document and visualize intrarenal backflow as a function of IRP and time in a pig model.

METHODS

Studies were performed on five female pigs. A ureteral catheter was placed in the renal pelvis and connected to a Gadolinium/ saline solution 3 ml/L for irrigation. An occlusion balloon-catheter was left inflated at the uretero-pelvic junction and connected to a pressure monitor. Irrigation was successively regulated to maintain steady IRP levels at 10, 20, 30, 40 and 50 mmHg. MRI of the kidneys was performed at 5-minute intervals. PCR and immunoassay analyses were executed on the harvested kidneys to detect potential changes in inflammatory markers.

RESULTS

MRI showed backflow of Gadolinium into the kidney cortex in all cases. The mean time to first visual damage was 15 minutes and the mean registered pressure at first visual damage was 21 mmHg. On the final MRI the mean percentage of IRB affected kidney was 66% after irrigation with a mean maximum pressure of 43 mmHg for a mean duration of 70 minutes. Immunoassay analyses showed increased MCP-1 mRNA expression in the treated kidneys compared to contralateral control kidneys.

CONCLUSIONS

Gadolinium enhanced MRI provided detailed information about IRB that has not previously been documented. IRB occurs at even very low pressures, and these findings are in conflict with the general consensus that keeping IRP below 30-35 mmHg eliminates the risk of post-operative infection and sepsis. Moreover, the level of IRB was documented to be a function of both IRP and time. The results of this study emphasize the importance of keeping IRP and OR time low during ureteroscopy.

Evaluation of renal oxygenation by near-infrared spectroscopy during endoscopic injection of bulking agents in children with vesicoureteral reflux

BACKGROUND

Near infrared spectroscopy (NIRS) is the measuring of regional tissue oxygenation (rSO2) by interpreting oxyhemoglobin and deoxyhemoglobin signals that come back by transmitting near infrared light to tissues. The effect of endourological interventions on renal perfusion in children is largely unknown.

AIMS

To evaluate the effects of endoscopic injection of bulking agents (EIBA) for vesicoureteral reflux (VUR) on renal oxygenation (RO) using renal NIRS monitoring, which shows renal perfusion and oxygenation changes.

STUDY DESIGN

Case-control study.

METHODS

Group I had bilateral inguinal surgery, Group II cystoscopy, and Group III, EIBA for VUR with 30 patients in each group. During the operation, vital signs, peripheral oxygen saturation, end-tidal carbon dioxide, and renal regional oxygen saturation index (rSO2) values by bilateral renal NIRS monitoring were recorded. NIRS values before induction (T0) to postoperative (Tend) were determined. A 20% or more reduction in renal rSO2 (%20↓rSO2) was considered significant. Group III was also evaluated as subgroup III-A (not having "%20↓rSO2") and subgroup III-B ("%20↓rSO2").

RESULTS

The rSO2 decrease was observed in the first 5 min for both sides in group III. The most significant drop was at T30 for the right kidney and a significant decrease in rSO2, 20% or more, was observed in 6 renal units of 4 patients having higher SFU grading and renal scar in group III.

CONCLUSION

EIBA may transitionally impair renal oxygenation. Higher SFU grading and renal scar may increase the risk of renal hypoxia during EIBA.

Monitoring renal oxygenation status by near-infrared spectroscopy during ureterorenoscopy in children

BACKGROUND

: Near-infrared spectroscopy (NIRS) monitoring demonstrates renal blood flow, perfusion, and oxygenation changes. This study aimed to evaluate the effects of pediatric endourological interventions (PEI) on regional oxygen saturation value (rSO2) usingrenal NIRS monitoring.

METHODS

Patients having bilateral inguinal surgery (group I), cystoscopy (group II), and ureterorenoscopy (group III), 20 patients in each group, were included in the study. NIRS values before induction (T0) and at 5 min (T5), 10 min (T10), 15 min (T15), 20 min (T20), 25 min (T25), 30 min (T30) of the surgical procedure, and at the postextubation (Tend) were determined. The amount of irrigation fluid was recorded in groups II and III. The ureterorenoscopy group was also evaluated as two subgroups, as group III-R with patients having a "20%↓rSO2" and as group III-NoR, not having a "20%↓rSO2".

RESULTS

The mean total volume of irrigation was higher in group III, but the difference was not significant between the subgroups III-R and III-NoR. Renal rSO2 decreased significantly in T25, T30, and T-end values in group III. "20%↓rSO2" was seen in 1 patient in group II and 7 patients in group III. In the subgroups III-R, all patients had an obstructive pathology and significant preoperative hydronephrosis with a mean renal pelvis AP diameter of 21.1 ± 16.4 mm.

DISCUSSION

Although rSO2 significantly improves postoperatively, our data may suggest that congenital and acquired obstructive pathologies with hydronephrosis, prolonged operative time with continuous irrigation, and instrument movement in a narrow lumen may increase intrarenal pressure and the risk of renal hypoxia in endourological interventions. Preoperative evaluation of kidney functions and a meticulously well-planned intervention can prevent possible complications.

Comparison of vacuum suction ureteroscopic laser lithotripsy and traditional ureteroscopic laser lithotripsy for impacted upper ureteral stones

PURPOSE

To compare a novel vacuum suction ureteroscopic laser lithotripsy (VS-URS) with traditional ureteroscopic laser lithotripsy (T-URS) for impacted upper ureteral stones and to better define the potential benefits of VS-URS.

METHODS

Between May 2019 and March 2021, 158 patients with impacted upper ureteral stones underwent ureteroscopic holmium-YAG laser lithotripsy. Of these, 76 underwent VS-URS and 82 underwent T-URS. In VS-URS procedures, the vacuum suction device is composed of a 5F ureteral catheter and a tee joint. The ureteral catheter is linked to the vacuum aspirator by the sidearm of the tee joint, and a 200 μm fiber is inserted through the tee joint and the ureteral catheter into the stone site for lithotripsy.

RESULTS

When compared to the T-URS group, the VS-URS group had a shorter mean operation time (38.18 ± 6.37 min vs. 46.65 ± 5.66 min; P = 0.000), lower fever rate (3.9% vs. 14.6%; P < 0.022), less stone retropulsion (5.3% vs. 18.3%; P = 0.012), lower extra management rate (6.58% vs. 21.95%; P = 0.006), and a higher stone-free rate of the first postoperative day (88.2% vs. 72.0%; P = 0.011). There were no significant differences in stone-free rates 1 month after surgery between groups (94.7% vs. 92.7%; P = 0.748).

CONCLUSIONS

VS-URS is an effective modality for impacted upper ureteral stones, and has a shorter operating time, lower fever rate, less stone retropulsion, and a higher primary stone-free rate compared with T-URS.

Salbutamol for analgesia in renal colic: study protocol for a prospective, randomised, placebo-controlled phase II trial (SARC)

BACKGROUND

Renal colic is the pain experienced by a patient when a renal calculus (kidney stone) causes partial or complete obstruction of part of the renal outflow tract. The standard analgesic regimes for renal colic are often ineffective; in some studies, less than half of patients achieve complete pain relief, and a large proportion of patients require rescue analgesia within 4 h. Current analgesic regimes are also associated with significant side effects including nausea, vomiting, drowsiness and respiratory depression. It has been hypothesised that beta adrenoreceptor agonists, such as salbutamol, may reduce the pain of renal colic. They have been shown to impact a number of factors that target the physiological causes of pain in renal colic (ureteric spasm and increased peristalsis, increased pressure at the renal pelvis and prostaglandin release with inflammation). There is biological plausibility and a body of evidence sufficient to suggest that this novel treatment for the pain of renal colic should be taken to a phase II clinical trial. The aim of this trial is to test whether salbutamol is an efficacious analgesic adjunct when added to the standard analgesic regime for patients presenting to the ED with subsequently confirmed renal colic.

METHODS

A phase II, randomised, placebo-controlled trial will be performed in an acute NHS Trust in the East Midlands. Patients presenting to the emergency department with pain requiring IV analgesia and working diagnosis of renal colic will be randomised to receive standard analgesia ± a single intravenous injection of Salbutamol. Secondary study objectives will explore the feasibility of conducting a larger, phase III trial.

DISCUSSION

The trial will provide important information about the efficacy of salbutamol as an analgesic adjunct in renal colic. It will also guide the development of a definitive phase III trial to test the cost and clinical effectiveness of salbutamol as an analgesic adjunct in renal colic. Salbutamol benefits from widespread use across the health service for multiple indications, extensive staff familiarity and a good side effect profile; therefore, its potential use for pain relief may have significant benefits for patient care.

TRIAL REGISTRATION

ISRCTN Registry ISRCTN14552440 . Registered on 22 July 2019.

Silodosin for Prevention of Ureteral Injuries Resulting from Insertion of a Ureteral Access Sheath: A Randomized Controlled Trial

BACKGROUND

The ureteral access sheath (UAS) is an ancillary device widely used by urologists, but acute ureter injury may occur following its insertion. Preoperative selective oral α1-blockers can reduce intraureteral pressure, and prevent ureteral wall injury during UAS insertion.

OBJECTIVE

To compare perioperative data of patients who underwent flexible ureterorenoscopy (fURS) with UAS with and without premedication with silodosin.

DESIGN, SETTING, AND PARTICIPANTS

Single-blind, 100 patients from a single institution who underwent retrograde intrarenal surgery for kidney and upper ureter stone removal were prospectively allocated from May 2018 to March 2019.

INTERVENTION

The experimental groups received silodosin for 3 d preoperatively.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint included ureteral injuries after UAS insertion that were assessed according to endoscopic classification. The secondary endpoint was an evaluation of whether premedication with silodosin had any effect on postoperative outcomes.

RESULTS AND LIMITATIONS

A total of 44 and 43 patients were randomly assigned to the control and experimental groups, respectively. Silodosin prevented significant postoperative ureteral injury involving the smooth muscle layer more successfully than in the control group (9.3% vs 27.3%; p = 0.031). There was no significant difference in the overall complication rate as determined by the modified Clavien-Dindo classification system and the computed tomography scan stone-free rate postoperatively. Patients who received silodosin before fURS reported lower pain scores than those in the control group using a visual analog scale (p = 0.009). Limitation included a lack of placebo comparison.

CONCLUSIONS

Our data suggest that preoperative silodosin protects against significant ureteral injury related to UAS insertion during fURS and decreases postoperative pain level. Silodosin premedication might be an effective and safe technique to replace prestenting.

PATIENT SUMMARY

We investigated the preventive effect of an α-blocker against perioperative complication caused by ureteral access sheath inserted during flexible ureterorenoscopy. Taking silodosin before surgery prevented ureter wall injury during surgery and immediately improved postoperative pain.

Diagnostic ureteroscopy for upper tract urothelial carcinoma: friend or foe?

Introduction

The European Association of Urology guidelines recommend offering kidney-sparing surgery (KSS) as a primary treatment option to patients with low-risk tumours. Cystoscopy, urinary cytology, and computed tomography urography (CTU) do not always allow correct disease staging and grading, and sometimes there is even a lack of certainty regarding the diagnosis of UTUC. Diagnostic ureteroscopy (d-URS) may therefore be of crucial importance within the diagnostic framework and fundamental in establishing the appropriate therapeutic approach.

Evidence acquisition and synthesis

A systematic review of the literature was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Risk of bias was assessed using Risk of Bias in Non-randomized Studies of interventions (ROBINS-I). Overall, from 3791 identified records, 186 full-text articles were assessed for eligibility. Finally, after a quantitative review of the selected literature, with the full agreement of all authors, 62 studies were considered relevant for this review.

Results

CTU has a sensitivity and specificity for UTUC of 92% and 95% respectively, but is not able to detect small or flat lesions with adequate accuracy. The sensitivity of voided urinary cytology for UTUC is around 67–76% and ranges from 43% to 78% for selective ureteric urine collection. As no technique offers a diagnosis of certainty, d-URS can allow an increase in diagnostic accuracy. In the present review the pros and cons of d-URS were analysed. This technique may provide additional information in the selection of patients suitable for neoadjuvant chemotherapy or KSS, distinguishing between normal tissue and low- and high-grade UTUC thanks to the emerging technologies.

Conclusions

Information obtainable from d-URS and ureteroscopic-guided biopsy can prove extremely valuable when the diagnosis of UTUC is doubtful or KSS is being considered. Notwithstanding concerns remain regarding the potential risk of bladder recurrence, cancer dissemination, and/or delay in radical treatment.

Abbreviations: CLE: confocal laser endomicroscopy; CSS: cancer-specific survival; CTU: CT urography; d-URS: diagnostic ureteroscopy; EAU: European Association of Urology; HR: hazard ratio; IMAGE1S: Storz professional imaging enhancement system; IVR: intravesical recurrence; KSS: kidney-sparing surgery; MFS: Metastasis-free survival; NAC: neoadjuvant chemotherapy; NBI: narrow-band imaging; OCT: optical coherence tomography; RFS: Recurrence-free survival; RNU: radical nephroureterectomy; ROBINS-I: Risk of Bias in Non-randomized Studies of interventions; URS(-GB): Ureteroscopy(-guided biopsy); UTUC: upper tract urothelial carcinoma; UUT: upper urinary tract

Flexible ureteroscopy and laser lithotripsy for renal stones 2 cm or greater: A single institutional experience

With improvements in endoscopy and laser technology, flexible ureteroscopy (FURS) has been a viable treatment option for large renal stones. Here, we share our experience of the FURS treatment for renal stones 2 cm or greater.We evaluated 251 consecutive patients who underwent FURS and holmium laser lithotripsy for renal stones 2 cm or greater between January 2015 and April 2019. Stone size was defined as the longest axis on non-contrast computed tomography. Data were retrospectively collected from electronic medical records. Patient demographics, stone clearance rates and perioperative complications were evaluated.There were 165 male patients and 86 female patients with an average age of 46.9 years (range 22-80 years). Mean stone size was 2.7 cm and the average number of procedures was 1.4 (range 1-5). The stone-free rate at the end of the first, second and third procedure was 61.9%, 82.9%, and 89.5%, respectively. The final stone-free rate decreased as stone size grows, and it was only 58.3% for kidney stones larger than 4 cm after an average of 2.3 procedures. The lowest clearance rates were observed in lower calyx calculi (87.2%) and multiple calyx calculi (83.5%). The overall complication rate was 15.1%, and the most common complication was postoperative fever (9.6%). One patient required blood transfusion, owing to postoperative coagulation disorders induced by urosepsis.Single or staged FURS is a practical treatment option for the renal stones sized 2 to 4 cm with acceptable efficacy and safety. Stone clearance rate of FURS treatment is mainly affected by stone size and location.

Holmium:Yttrium-Aluminum-Garnet Laser Pulse Type Affects Irrigation Temperatures in a Benchtop Ureteral Model

Introduction: MOSES^™ technology is a holmium:yttrium-aluminum-garnet laser pulse mode shown to minimize stone retropulsion. This may facilitate lithotripsy at higher power settings. However, power and heat production are proportional, and temperatures capable of tissue injury may occur during ureteroscopic lithotripsy. Although previous in vitro studies demonstrate the importance of irrigation and activation time on heat production, the impact of pulse type has not been evaluated. Methods: A flexible ureteroscope with a 365 μm laser fiber was placed in an 11/13 F access sheath inserted into a 50 mL saline bag to simulate a ureter, renal pelvis, and antegrade irrigant flow. A thermocouple was placed adjacent to the laser tip, and the laser fired for 30 seconds at 0.6 J/6 Hz, 0.8 J/8 Hz, 1 J/10 Hz, 1 J/20 Hz, and 0.2 J/70 Hz at irrigation pressure of 100 mmHg. Four runs were tested per setting using short pulse, long pulse (LP), MOSES-contact (MC), and MOSES-distance (MD) modes. The mean temperature changes (dT) were compared and thermal dose was calculated in cumulative equivalent minutes at 43°C (CEM43) using an adjusted baseline of 37°C. CEM43 ≥ 120 minutes was considered the tissue injury threshold. Results: At 0.8 J/8 Hz, LP produced the greatest dT, significantly higher than MC (p = 0.041). CEM43 did not exceed the injury threshold. At 1 J/10 Hz, dT was significantly higher for LP versus MC and MD (p = 0.024 and 0.045, respectively). Thermal dose remained below the injury threshold. No differences in dT were seen between pulse types at 0.6 J/6 Hz, 0.2 J/70 Hz, or 1 J/20 Hz. At 1 J/20 Hz, thermal dose exceeded the injury threshold for all pulse types within 3 seconds. Conclusions: Laser pulse type and length seemed to impact heat production in our ureteral model. LP produced significantly greater temperatures at 0.8 J/8 Hz and 1 J/10 Hz relative to MOSES settings. Fortunately, thermal dose remained safe at these settings. Both LP and MOSES technology have been shown to reduce stone retropulsion. At power ≤10 W, the latter may confer this advantage with decreased heat production.

Comparison of utilization of pressurized automated versus manual hand irrigation during ureteroscopy in the absence of ureteral access sheath

This study compared patient outcomes following irrigation applied using an automated pressure system (AP) to hand irrigation utilizing a syringe (HI) during ureteroscopy. Retrospective chart review was performed to evaluate ureteroscopy procedures without a ureteral access sheath. Procedures in which irrigation was applied by AP were compared to those with HI. Statistical analyses included chi-squared tests and Student's t tests. The AP group contained 206 procedures and the HI group, 25. The AP and HI groups were 54.9% and 36% male, respectively. Mean ages were 53.7 ± 18.9 years in the AP group and 44.0 ± 18.5 years in the HI group. Complication rates were 11.2% in the AP and 8.3% in the HI group (P > 0.99). One stone retrieval failure and one stone recurrence occurred in the HI group; one patient had residual stone in the AP group. No urinary tract infections occurred in the HI group; in the AP group, urinary tract infections occurred in 1.9% of cases. The postoperative pain incidence was equivalent (P = 0.498). The AP group had one subcapsular hematoma; no calyceal ruptures occurred in either group. In conclusion, irrigation applied by an automated setup appears safe, with similar outcomes to irrigation applied with a handheld syringe.

Clinical characteristics of postoperative febrile urinary tract infections after ureteroscopic lithotripsy

Purpose

Ureteroscopic lithotripsy (URS) is gaining popularity for the management of ureteral stones and even renal stones, with high efficacy and minimal invasiveness. Although this procedure is known to be safe and to have a low complication rate, febrile urinary tract infection (UTI) after URS is not rare. Therefore, we aimed to analyze the risk factors and causative pathogens of febrile UTI after URS.

Materials and Methods

Between January 2013 and June 2015, 304 patients underwent URS for ureteral or renal stones. The rate of postoperative febrile UTI and the causative pathogens were verified, and the risk factors for postoperative febrile UTI were analyzed using logistic regression analysis.

Results

Of 304 patients, postoperative febrile UTI occurred in 43 patients (14.1%). Of them, pathogens were cultured in blood or urine in 19 patients (44.2%), and definite pathogens were not identified in 24 patients (55.8%). In patients with an identified pathogen, Pseudomonas aeruginosa had the highest incidence. Multivariate analysis showed that the operation time (p<0.001) was an independent risk factor for febrile UTI after URS. The cut-off value of operation time for increased risk of febrile UTI was 70 minutes.

Conclusions

Overall, febrile UTI after URS occurred in 14.1% of patients, and the operation time was an independent predictive factor for this complication. Considering that more than 83.7% of febrile UTIs after URS were not controlled with fluoroquinolones, it may be more appropriate to use higher-level antibiotics for treatment, even in cases with unidentified pathogens.

Micro-ureteroscopy vs. ureteroscopy: effects of miniaturization on renal vascularization and intrapelvic pressure

PURPOSE

Ureteroscopy (URS) is related to complications, as fever or postoperative urinary sepsis, due to high intrapelvic pressure (IPP) during the procedure. Micro-ureteroscopy (m-URS) aims to reduce morbidity by miniaturizing the instrument. The objective of this study is to compare IPP and changes in renal haemodynamics, while performing m-URS vs. conventional URS.

METHODS

A porcine model involving 14 female pigs was used in this experimental study. Two surgeons performed 7 URS (8/9.8 Fr), for 45 min, and 7 m-URS (4.85 Fr), for 60 min, representing a total of 28 procedures in 14 animals. A catheter pressure transducer measured IPP every 5 min. Haemodynamic parameters were evaluated by Doppler ultrasound. The volume of irrigation fluid employed in each procedure was also measured.

RESULTS

The range of average pressures was 5.08-14.1 mmHg in the m-URS group and 6.08-20.64 mmHg in the URS (NS). 30 mmHg of IPP were not reached in 90% of renal units examined with m-URS, as compared to 65% of renal units in the URS group. Mean peak diastolic velocity decreased from 15.93 to 15.22 cm/s (NS) in the URS group and from 19.26 to 12.87 cm/s in the m-URS group (p < 0.01). Mean resistive index increased in both groups (p < 0.01). Irrigation fluid volume used was 485 mL in the m-URS group and 1475 mL in the URS group (p < 0.001).

CONCLUSIONS

m-URS requires less saline irrigation volumes than the conventional ureteroscopy and increases renal IPP to a lesser extent.

Risks of flexible ureterorenoscopy: pathophysiology and prevention

Currently, indications for flexible ureterorenoscopy (fURS) are expanding, mainly due to technological advancements. Although data from clinical series definitely presents fURS as a safe procedure, serious complications including sepsis and ureteral lesions do occur. These complications seem to be a result of the unique elements of fURS, ureteral access and irrigation, pushing normal upper urinary tract physiology into pathophysiological processes, including intrarenal/pyelo-veneous backflow and ureteral contractions, potentially resulting in septic, haemorrhagic and ureteral lesional complications. Knowledge on normal upper urinary tract physiology are crucial for understanding how these harmful effects of fURS may be avoided or minimized. The pathophysiology of intrarenal pressure increases and ureteral access will be discussed as a basis for understanding preventive measures. Role of antibiotics, ureteral access sheaths, safty guidewires, pain medication, prestenting and pharmacologic modulation of pyeloureteral dynamics are reviewed from a pathophysiological perspective.

Histopathological correlations to ureteral lesions visualized during ureteroscopy

Purpose

To correlate ureteral lesions visualized during ureteroscopy with histopathological findings.

Materials and methods

Ureteral access sheaths (UAS) sized 13/15 Fr. were inserted bilaterally in 22 laboratory pigs. During retraction of the UAS with a semirigid ureteroscope inside, ureteral lesions were evaluated and registered using the Post-ureteroscopic lesion scale (PULS). Ureters were excised in vivo between the uretero–pelvic junction and the uretero–vesical junction. Embedded in paraffin, 4-µm thick sections were step sectioned at 250–300 µm intervals and haematoxylin and eosin (HE) stained. Histopathological scoring of ureteral wall lesions was subsequently performed according to PULS.

Results

In 72.1% of ureters, the highest histopathological score was at least 1 grade higher than the highest endoscopic PULS score. For 12 (27.9%) lesions, the difference was 2 scores higher, and for 1 (2.3%), it was 3 scores higher. The histopathological PULS grade was higher than the endoscopical PULS grade at all minimum, quartile, and maximum scores. There was a significant difference in the distribution of highest lesional scores between the endoscopic and histopathological PULS (p = 0.002). The calculated mean of the highest scores was 1.49 for endoscopic PULS and 2.51 for histopathological PULS (p < 0.0001).

Conclusion

Histopathological evaluation of ureteral wall lesions after UAS placement revealed a significantly higher degree of severity than observed endoscopically. Thus, endoscopy underestimated the histopathological extent of the lesion in the majority of cases.

Ureteral Access Sheath Influence on the Ureteral Wall Evaluated by Cyclooxygenase-2 and Tumor Necrosis Factor-α in a Porcine Model

Objective: To examine the effect of ureteral access sheath (UAS) on the expression of the pro-inflammatory mediators cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNF-α) in the ureteral wall.

Material and Methods: In 22 pigs an UAS was inserted and removed after 2 minutes on one side and 2 hours on the contralateral side. Postoperatively ureters were excised in vivo, and tissue samples from the distal (2 minutes/2 hours) and proximal ureter (2 minutes/2 hours) were snap-frozen before quantitative polymerase chain reaction analysis of COX-2 and TNF-α. Five unmanipulated ureteral units from other pigs served as the control group.

Results: Compared to controls COX-2 mRNA was significantly upregulated in all UAS treated ureteral groups. Similarly, TNF-α mRNA was upregulated in all groups except the 2-minute proximal ureteral group. Both COX-2 and TNF-α expression were significantly higher in the distal than in the proximal ureter in the UAS treated ureters. After UAS insertion for 2 minutes, expression levels in the distal ureter were increased 6.5- and 8-fold for COX-2 and TNF-α, respectively; and after 2 hours of UAS placement COX-2 and TNF-α mRNA expression levels were increased 9- and 9.5-fold, respectively.

Conclusion: The pro-inflammatory mediators COX-2 and TNF-α were significantly upregulated in the ureteral wall by the influence of UAS. These findings may have implications for postoperative pain, drainage, and complications.

Pharmacological Relaxation of the Ureter When Using Ureteral Access Sheaths during Ureterorenoscopy: A Randomized Feasibility Study in a Porcine Model

Objective. High intraluminal pressure during ureterorenoscopy (URS) increases risk of infectious and haemorrhagic complications. Intrarenal pressure may be reduced by the use of ureteral access sheaths (UASs), which on the other hand may cause ureteral damage. We have previously shown that the β-agonist isoproterenol (ISO), when administered topically in the irrigation fluid, is able to inhibit ureteral muscle tone and lower intrarenal pressure during URS. The aim of this study was to examine the effect of ISO on the success rate of UAS insertion in a porcine model. Materials and Methods. 22 pigs in which a UAS could not initially be placed were randomized to endoluminal irrigation with either ISO (0.1 μg/mL) or saline before a new insertion trial. Subsequently, it was registered whether the UAS could be passed without resistance. During extraction of the sheath, any ureteral lesions were characterized ureteroscopically using the PULS classification system. Surgeons were blinded to randomization. Results. In the ISO group, the observed effect of irrigation was 63% successful UAS insertions, compared to 27% in the saline group. No serious lesions (<PULS grade 2) were observed in the ISO group. Conclusions. Endoluminal irrigation with ISO may facilitate UAS insertion and potentially decrease UAS related ureteral lesions.