In silico assessment of the reliability and performance of artificial sphincter for urinary incontinence.

BACKGROUND: The standard artificial urinary sphincter (AUS) is an implantable device for the treatment of urinary incontinence by applying a pressure loading around the urethra through an inflatable cuff, often inducing no-physiological stimulation up to tissue degenerative phenomena. A novel in silico approach is proposed to fill the gap of the traditional procedures by providing tools to quantitatively assess AUS reliability and performance based on AUS-urethra interaction. METHODS: The approach requires the development of 3D numerical models of AUS and urethra, and experimental investigations to define their mechanical behaviors. Computational analyses are performed to simulate the urethral lumen occlusion by AUS inflation under different pressures, and the lumen opening by applying an intraluminal pressure progressively increased under the AUS action (Abaqus Explicit solver). The AUS reliability is evaluated in terms of tissue stimulation by the mechanical fields potentially responsible for vasoconstriction and tissue damage, while the performance by the intraluminal pressure that causes the lumen opening for a specific occlusive pressure, showing the maximum urethral pressure for which continence is guaranteed. RESULTS: The present study implemented the procedure considering the gold standard AMS 800 and a novel patented AUS. Results provided the comparison between two sphincteric devices and the evaluation of the influence of different building materials and geometrical features on the AUS functionality. CONCLUSIONS: The approach was developed for the AUS, but it could be adapted also to artificial sphincters for the treatment of other anatomical dysfunctions, widening the analyzable device configurations and reducing experimental and ethical efforts.

Ergonomic Considerations in Urologic Surgery.

PURPOSE OF REVIEW: This paper aims to discuss the various work-related musculoskeletal disorders (WRMDs) among urologists and provide an overview of the latest recommendations to improve awareness of ergonomic principles that can be applied in the operating room, with special consideration of challenges faced during pregnancy. RECENT FINDINGS: Urologists suffer from a large burden of WRMDs. The main drivers of pain associated with the various surgical approaches include repetitive movements, static and awkward body positions, and the use of burdensome equipment. Pregnant surgeons are at an even greater risk of WRMDs and face high rates of pregnancy complications. Laparoscopy, endoscopy, robot-assisted surgeries, and open surgeries present unique ergonomic challenges for the practicing urologist. Proper posture and equipment use, optimal operating room setup, intraoperative stretching breaks, and an emphasis on teaching ergonomic principles can reduce the risk of WRMDs. Surgeons are also at increased risk of WRMDs during pregnancy but may continue to operate while taking measures to limit physical exertion and fatigue. Improving awareness of and incorporating ergonomic principles early in a urologist's career may reduce the risk of injury and improve operative performance and longevity.

Patient Compliance in Assessing Electronic Patient-Reported Outcome Measures after Urologic Surgery.

INTRODUCTION: This study aimed to assess patient compliance with a newly established electronic patient-reported outcome measure (ePROM) system after urologic surgery and to identify influencing factors. METHODS: Digital surveys were provided to patients undergoing cystectomy, radical or partial nephrectomy, or transurethral resection of bladder tumor via a newly established ePROM system. Participants received a baseline survey preoperatively and several follow-up surveys postoperatively. Multivariable regression analysis was performed to identify factors predicting compliance. RESULTS: Of N = 435 eligible patients, n = 338 completed the baseline survey (78.0%). Patients who did not participate were significantly more likely male (p = 0.004) and older than 70 years (p = 0.005). Overall, 206/337 patients (61.3%) completed the survey at 1-month, 167/312 (53.5%) at 3-month, and 142/276 (51.4%) at 6-month follow-up. Lower baseline quality of life (odds ratio: 2.27; p = 0.004) was a significant predictor for dropout at 1-month follow-up. Low educational level was significantly associated with low compliance at 3- (OR: 1.92; p = 0.01) and 6-month follow-up (OR: 2.88; p < 0.001). CONCLUSION: Acceptable compliance rates can be achieved with ePROMs following urologic surgery. Several factors influence compliance and should be considered when setting-up ePROM surveys.

Robot-assisted laparoscopic varicocelectomy in a pediatric population.

PURPOSE: To present our experience with robot-assisted laparoscopic varicocelectomy in a pediatric population. METHODS: We reviewed 49 consecutive cases performed by the same experienced surgeon. One-to-four veins were ligated at the internal ring of the inguinal canal, while the testicular artery and lymphatics were spared. Information on patient characteristics, surgical time, complications, and recurrences were collected. RESULTS: Median patient age was 14 (range 10-17) years. Forty-eight had left-sided varicoceles and one had a bilateral varicocele. Forty-five were grade 3. All patients were referred due to discomfort/pain and 20 also had reduced testicular size. The median operating time from skin incision was 48 min (31-89 min) and the median console time was 18 min (7-55 min). Forty-seven patients were discharged the same day. Two patients experienced pain and problems urinating, respectively. These issues had resolved by the first post-operative day. There were no other complications, but at 6 months, eight recurrences were noted (16%). Scrotal complaints had subsided in all patients. Catch-up growth of the affected testicles was seen in 19/20 cases. CONCLUSION: Robot-assisted laparoscopic varicocelectomy is feasible and safe in a pediatric population but with a relatively high recurrence rate.

Multicenter retrospective study on benign testicular tumors in children: save as much as you can please.

BACKGROUND: Testicular tumors (TT) are infrequent in pediatric patients, representing 1% of pediatric solid tumors; benign testicular tumors (BTT) are the most common. We present a multicenter study aiming to describe the incidence, histology and surgical technique of BTT, with special emphasis on which approach could present better outcomes. METHODS: The records of pediatric patients diagnosed with BTT between 2005 and 2020 from 8 centers in 5 different countries in Latin-America, were reviewed. RESULTS: Sixty two BTTs were identified. 73% tumors presented as a testicular mass, and 97% underwent testicular ultrasound as the initial imaging study, all of them had findings suggestive of a benign tumor. 87% had preoperative tumor markers (AFP and BHCG). In 66%, an intraoperative biopsy was done and 98% of the intraoperative biopsies were concordant with the final pathology report. Tumorectomy was performed in 81% of patients and total orchiectomy in the remaining 19%. Six percentage of patients underwent a subsequent orchiectomy. Mean follow-up was 39 months (1-278 months) where no cases of atrophy were observed clinically or on ultrasound. Fertility was not evaluated in this series. CONCLUSIONS: Proper management of BTTs is essential to avoid unnecessary orchiectomies. Preoperative ultrasound associated with intraoperative biopsy seems accurate in identifying benign pathology, thus enabling conservative testicular surgery with safety margins. Based on this multicenter series, we suggest performing an intraoperative biopsy with subsequent tumorectomy preserving healthy testicular tissue in BTT.

Three-Dimensional Printed Anatomic Models Derived From Magnetic Resonance Imaging Data: Current State and Image Acquisition Recommendations for Appropriate Clinical Scenarios.

Three-dimensional (3D) printing technologies have been increasingly utilized in medicine over the past several years and can greatly facilitate surgical planning thereby improving patient outcomes. Although still much less utilized compared to computed tomography (CT), magnetic resonance imaging (MRI) is gaining traction in medical 3D printing. The purpose of this study was two-fold: 1) to determine the prevalence in the existing literature of using MRI to create 3D printed anatomic models for surgical planning and 2) to provide image acquisition recommendations for appropriate clinical scenarios where MRI is the most suitable imaging modality. The workflow for creating 3D printed anatomic models from medical imaging data is complex and involves image segmentation of the regions of interest and conversion of that data into 3D surface meshes, which are compatible with printing technologies. CT is most commonly used to create 3D printed anatomic models due to the high image quality and relative ease of performing image segmentation from CT data. As compared to CT datasets, 3D printing using MRI data offers advantages since it provides exquisite soft tissue contrast needed for accurate organ segmentation and it does not expose patients to unnecessary ionizing radiation. MRI, however, often requires complicated imaging techniques and time-consuming postprocessing procedures to generate high-resolution 3D anatomic models needed for 3D printing. Despite these challenges, 3D modeling and printing from MRI data holds great clinical promises thanks to emerging innovations in both advanced MRI imaging and postprocessing techniques. EVIDENCE LEVEL: 2 TECHNICAL EFFICATCY: 5.

Extended Reality-Assisted Surgery as a Surgical Training Tool: Pilot Study Presenting First HoloLens-Assisted Complex Penile Revision Surgery.

BACKGROUND: Extended reality-assisted urologic surgery (XRAS) is a novel technology that superimposes a computer-generated image on the physician's field to integrate common elements of the surgical process in more advanced detail. An extended reality (XR) interface is generated using optical head-mounted display (OHMD) devices. AIM: To present the first case of HoloLens-assisted complex penile revision surgery. METHODS: We describe our pilot study of HoloLens-assisted penile revision surgery and present a thorough review of the literature regarding XRAS technology and innovative OHMD devices. OUTCOMES: The ability of XRAS technology to superimpose a computer-generated image of the patient and integrate common elements of the surgical planning process with long-distance experts. RESULTS: XRAS is a feasible technology for application in complex penile surgical planning processes. CLINICAL TRANSLATION: XRAS and OHMD devices are novel technologies applicable to urological surgical training and planning. STRENGTHS AND LIMITATIONS: Evidence suggests that the potential use of OHMD devices is safe and beneficial for surgeons. We intend to pioneer HoloLens technology in the surgical planning process of a malfunctioning penile implant due to herniation of the cylinder. This novel technology has not been used in prosthetic surgery, and current data about XRAS are limited. CONCLUSION: OHMD devices are effective in the operative setting. Herein, we successfully demonstrated the integration of Microsoft HoloLens 2 into a penile surgical planning process for the first time. Further development and studies for this technology are necessary to better characterize the XRAS as a training and surgical planning tool. Quesada-Olarte J, Carrion RE, Fernandez-Crespo R, et al. Extended Reality-Assisted Surgery as a Surgical Training Tool: Pilot Study Presenting First HoloLens-Assisted Complex Penile Revision Surgery. J Sex Med 2022;19:1580-1586.

Machine learning applications to enhance patient specific care for urologic surgery.

PURPOSE: As computational power has improved over the past 20 years, the daily application of machine learning methods has become more prevalent in daily life. Additionally, there is increasing interest in the clinical application of machine learning techniques. We sought to review the current literature regarding machine learning applications for patient-specific urologic surgical care. METHODS: We performed a broad search of the current literature via the PubMed-Medline and Google Scholar databases up to Dec 2020. The search terms "urologic surgery" as well as "artificial intelligence", "machine learning", "neural network", and "automation" were used. RESULTS: The focus of machine learning applications for patient counseling is disease-specific. For stone disease, multiple studies focused on the prediction of stone-free rate based on preoperative characteristics of clinical and imaging data. For kidney cancer, many studies focused on advanced imaging analysis to predict renal mass pathology preoperatively. Machine learning applications in prostate cancer could provide for treatment counseling as well as prediction of disease-specific outcomes. Furthermore, for bladder cancer, the reviewed studies focus on staging via imaging, to better counsel patients towards neoadjuvant chemotherapy. Additionally, there have been many efforts on automatically segmenting and matching preoperative imaging with intraoperative anatomy. CONCLUSION: Machine learning techniques can be implemented to assist patient-centered surgical care and increase patient engagement within their decision-making processes. As data sets improve and expand, especially with the transition to large-scale EHR usage, these tools will improve in efficacy and be utilized more frequently.

Renal surgery in patients with a duplicated inferior vena cava: a case series and review of the literature.

Abnormal inferior vena cava (IVC) anatomy may present unique challenges for urologists when performing retroperitoneal surgery. Duplication of the IVC is one such anomalous variation and can be found in up to 3% of the population. Misunderstanding of the implications of this aberrant anatomy may lead to intraoperative or postoperative complications. Here, we present two cases of patients undergoing renal surgeries with duplicate IVC. We then review the embryologic origin and anatomic findings in those with abnormal IVC anatomy as well as discuss the surgical implications and considerations for urologists.

Detection rate and variables associated with incidental prostate cancer by holmium laser enucleation of the prostate.

OBJECTIVES: Holmium laser enucleation of the prostate is well-established and effective for bladder outlet obstruction due to benign prostatic hyperplasia. The objective of this study was to examine the detection rate of incidental prostate cancer by holmium laser enucleation of the prostate and variables associated with them. METHODS: A total of 612 patients were enrolled. We retrospectively examined the detection rate of incidental prostate cancer and perioperative variables associated with them. RESULTS: Forty-nine of 612 patients were diagnosed with incidental prostate cancer. Univariate logistic regression analysis showed that higher prostate-specific antigen density (odds ratio 3.34, 95% confidence interval 1.02-10.94, P = 0.05), higher prostate-specific antigen density of the transition zone (odds ratio 2.28, 95% confidence interval 1.02-5.09, P = 0.04), and findings of the prostate cancer on magnetic resonance imaging (peripheral zone: odds ratio 4.71, 95% confidence interval 1.70-13.1, P = 0.003; transition zone: odds ratio 3.46, 95% confidence interval 1.74-6.86, P < 0.001; peripheral and transition zones: odds ratio 6.00, 95% confidence interval 1.51-23.8, P = 0.01) were significantly associated with incidental prostate cancer. Multivariate logistic regression analysis showed that findings of the prostate cancer on magnetic resonance imaging (peripheral zone: odds ratio 4.36, 95% confidence interval 1.49-12.8, P = 0.001; transition zone: odds ratio 3.54, 95% confidence interval 1.75-7.16, P < 0.001; peripheral and transition zones: odds ratio 6.14, 95% confidence interval 1.53-24.5, P = 0.01) was an independent risk factor for incidental prostate cancer. CONCLUSION: The detection rate of incidental prostate cancer was 8.0%, and findings of the prostate cancer on magnetic resonance imaging were an independent predictive factor for incidental prostate cancer.

How I Do It: Technical report on surgically-initiated rectus sheath catheter using catheter-over-needle assembly.

Development of chronic postsurgical pain following major abdominal or pelvic surgeries is increasingly recognized. Multimodal analgesia including regional anesthesia such as rectus sheath block is growing in popularity. While the literature mainly describes ultrasound-guided rectus sheath blocks, there are many advantages to surgically-initiated rectus sheath catheter performed at the end of surgery. In this technical description, we describe the rationale and technique of surgical insertion of rectus sheath catheters following major urologic surgery with midline incision which is routinely performed by urologists at our institution. Furthermore, we would like to highlight the type of catheter used during rectus sheath catheter insertion, namely the catheter-over-needle assembly. It is simple to insert while minimizes complications such as local anesthetic leakage at the insertion site causing dressing disruption and premature catheter dislodgement, as the catheter-over-needle assembly fits snugly with the skin after insertion.

The LACE + index as a predictor of 90-day urologic surgery outcomes.

PURPOSE: This study assessed the ability of the LACE + [Length of stay, Acuity of admission, Charlson Comorbidity Index (CCI) score, and Emergency department visits in the past 6 months] index to predict adverse outcomes after urologic surgery. METHODS: LACE + scores were retrospectively calculated for all consecutive patients (n = 9824) who received urologic surgery at one multi-center health system over 2 years (2016-2018). Coarsened exact matching was employed to sort patient data before analysis; matching criteria included duration of surgery, BMI, and race among others. Outcomes including unplanned hospital readmission, emergency room visits, and reoperation were compared for patients with different LACE + quartiles. RESULTS: 722 patients were matched between Q1 and Q4; 1120 patients were matched between Q2 and Q4; 2550 patients were matched between Q3 and Q4. Higher LACE + score significantly predicted readmission within 90 days (90D) of discharge for Q1 vs Q4 and Q2 vs Q4. Increased LACE + score also significantly predicted 90D emergency room visits for Q1 vs Q4, Q2 vs Q4, and Q3 vs Q4. LACE + score was also significantly predictive of 90D reoperation for Q1 vs Q4. LACE + score did not predict 90D reoperation for Q2 vs Q4 or Q3 vs Q4 or 90D readmission for Q3 vs. Q4. CONCLUSION: These results suggest that LACE + may be a suitable prediction model for important patient outcomes after urologic surgery.

A Systematic Review of Postoperative Delirium in the Urologic Patient.

PURPOSE OF REVIEW: Postoperative delirium (POD) is a common phenomenon among general surgery patients, but it is not well described in urologic surgical patients. We sought to define the incidence and predictive risk factors for POD in patients undergoing urologic surgery. RECENT FINDINGS: Eighteen articles were included for review. The pooled incidence rate of postoperative delirium after urologic surgery was 1.69% (0.69-46.97%). Longer intraoperative time, male sex, unmarried status, and age were shown to be risk factors for POD. POD is common after many urologic surgeries and leads to worse postoperative outcomes and higher healthcare utilization. Future studies are needed to better assess for and prevent POD.

Robotic Urologic Surgery in the Infant: a Review.

PURPOSE OF REVIEW: The goal of this article is to review the current role of robotic urologic surgery in the infant population across a spectrum of diseases and procedures. RECENT FINDINGS: Robotic urological surgery has been performed in the infant population across a variety of conditions including ureteropelvic junction obstruction, vesicoureteral reflux, and duplicated and nonfunctional renal moieties. However, most of the durable evidence showing safety and success remains in the repair of the obstructed ureteropelvic junction. Included in this review are also strategies to address the limitations imposed by the unique physiology and anatomy of the infant. Robotic urologic surgery remains an alternative to other surgical approaches in the properly selected infant in the hands of experienced surgeons. As additional larger studies are performed, the utility of the robotic platform in this population will be clearer.

A Contemporary Evaluation of Peyronie's Disease During Penile Prosthesis Placement: MOST, MUST, and More.

PURPOSE OF REVIEW: The use of penile implant for the treatment of both erectile dysfunction and Peyronie's disease has changed little in the last 40 years, primarily limited to modeling and plaque incision. In the current review, I explore the history of Peyronie's treatment at the time of penile prosthesis placement and explore new surgical options that help resolve several of the issues that were not treated with the traditional approaches. RECENT FINDINGS: Advancements have been made in the area of graft material, lengthening procedures, and transcorporal techniques. The goal of these operations is not only to correct curvature, but also to restore length. Not surprisingly, the more complex and aggressive the attempt to correct the curvature, the more complications are possible. While modeling has a low rate of urethral injury, complex lengthening procedure with neurovascular bundle and urethral mobilization may lead to the dreaded complication of glans necrosis. Meanwhile, transcorporal techniques seem to offer a more modest improvement for length and curvature restoration with fewer risks than those seen in more aggressive lengthening procedures. The main limitation to the historical treatment of Peyronie's disease during penile prosthesis, modeling, and plaque incision is there is often no resolution to the penile length-as the maneuvers are made after the implant is already in place. Newer lengthening procedures are promising, however carry increased risks and complexity.

Vascular Injury During Urologic Surgery: Somebody Call My Mother.

PURPOSE OF REVIEW: To provide the critical elements to effectively manage hemorrhage from vascular injuries sustained during planned urological interventions. RECENT FINDINGS: The frequency of intraoperative vascular injuries is increasing. However, literature concerning the management of iatrogenic operative vascular injuries is scarce. Although rare, intraoperative vascular injuries may be associated with potential catastrophic complications and death. The decision-making process following a potential life-threatening intraoperative vascular injury occurs in a very short time frame. Appropriate knowledge of the critical elements to identify the source of bleeding, initiate first-line hemostatic measures, select the candidate for damage control strategies, and perform the indicated operative repairing maneuvers and techniques have been proved crucial to ensure hemodynamic stability and bleeding cessation. The key surgical principles to counteract the impact of exsanguinating bleeding, and the aim to obtain the best achievable outcomes after definitive repair, are described in detail in this review.

Pericardium in Reconstructive Urologic Surgeries: A Systematic Review and Meta-Analysis.

INTRODUCTION: The use of pericardium has been expanded into different surgical modalities; however, there are scarce data regarding the feasibility of the pericardium in reconstructive urologic surgeries. We systematically reviewed the literature on the effectiveness of the pericardial tissue for reconstructive urologic surgeries. MATERIALS AND METHODS: PubMed and Scopus were searched online for evidence on the use of the pericardium in urologic surgeries. Through the methodology recommended by the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines, 38 of 4,071 studies were identified. RESULTS: A total of 715 patients and 139 animals underwent reconstructive urologic surgeries using the pericardium. Bladder, urethral, and renal reconstructions were successful in 100% of the human cases. The rates of dissatisfaction, glans hypoesthesia, and penile shortening were comparable between the pericardial graft surgeries and the other operations during penile straightening, but there was a trend among the patients with pericardial grafts toward having a more penile curvature at follow-up (risk ratio [RR] 2.03, 95% CI 0.90-4.61, p = 0.09; I2 = 0%). Among the animal studies, there were 4 reports of penile reconstruction, 7 studies of bladder reconstruction, and 1 study of urethroplasty. Bladder reconstruction and urethroplasty were successful in 83 and 20% of the animals, respectively. The pooled result of the stimulated intracorporeal pressure 5 V significantly favored pericardial grafts during penile reconstruction (RR 2.61, 95% CI 1.26-3.97, p = 0.0002; I2 = 0%). CONCLUSIONS: Our systematic review demonstrates the feasibility of the pericardium, regardless of its type, in urologic surgeries. It, however, seems that urethral substitution needs further investigation. Given the lower cost, easier handling, and less immunogenicity of the pericardium, further studies are required to examine its pros and cons.

Intraoperative Ureter Visualization Using a Novel Near-Infrared Fluorescent Dye.

Ureters can be accidentally severed during pelvic surgeries, significantly prolonging the times in the operating room to allow for complete repair of damaged ureters and leading to significant morbidities associated with consequent ureter obstruction and possible kidney dysfunction. In an effort to prevent these complications, light-emitting stents and urine-excreted dyes have been introduced to illuminate the ureter during surgery. However, problems with mechanical insertion, ureter spasm, image contrast, and localized injection have limited interest in their clinical applications. We report here the synthesis and characterization of a new near-infrared (NIR) fluorescent dye (UreterGlow) that can be injected systemically but is excreted primarily through the renal system, allowing ureter imaging with an NIR fluorescence camera. Following intravenous injection of 0.1 mg/kg UreterGlow, we have monitored the flow of UreterGlow through the proximal, medial, and distal segments of the ureter. The timing of ureter visualization was calculated from the time of injection of the drug. The null hypothesis was that "Visualization of the ureter in pigs is possible 60 min after administration of UreterGlow using an NIR camera". UreterGlow displayed excitation and emission maxima of λex = 800 nm and λem = 830 nm in phosphate buffered saline, pH 7.4, and could be imaged in the urinary tract in mice. Shortly after injection of UreterGlow into Yorkshire pigs, peristalsis of the ureter could be observed. The distal ureter could be visualized under NIR illumination after 60 min with constant fluorescence in all five pigs for >2 h. The same ureters could not be seen using visible light ( X2, p = 0.0001). Because both excitation and emission of UreterGlow occurs at >30 nm longer wavelength than most tumor-imaging fluorescent dyes, it should be possible to distinguish ureter fluorescence from tumor fluorescence with this dye.

Urinary tract infections, urologic surgery, and renal dysfunction in a contemporary cohort of traumatic spinal cord injured patients.

AIMS: The objective of this study was to measure the incidence of urinary tract infections (UTIs), urologic reconstruction/urinary diversion, and renal dysfunction after a traumatic spinal cord injury (TSCI). METHODS: Retrospective cohort study using administrative data from Ontario, Canada. All incident adult TSCI patients (2002-2013) admitted to a rehabilitation center were included. The impact of lesion level on each outcome was assessed. The rate of outcomes was further compared to an age and sex matched sample from the general population. RESULTS: A total of 2,023 incident TSCI patients were identified (median follow-up of 4.8 years). Most patients (73%) were male and median age was 50 years. Lesion level included cervical (39%), thoracolumbar (44%), and unknown (17%). The incidence of serious UTIs (requiring emergency room visit or hospital admission) was 40%. Thoracolumbar lesion TSCI patients had significantly greater risk of serious UTIs (HR 1.3, 95%CI 1.1-1.7, P < 0.01) compared to those with a cervical lesion. Urologic reconstruction/urinary diversion was carried out on 2.4% of patients. New onset renal dysfunction was identified in 4.2% (84) TSCI patients. The rate ratios for serious UTIs (10.59, 95%CI 8.71-12.89), urologic reconstruction/urinary diversion (6.48, 95%CI 3.07-13.68), and renal dysfunction (2.55, 95%CI 1.70-3.83) were significantly increased among TSCI patients compared to matched controls. CONCLUSIONS: Urologic disease is still an important source of morbidity for contemporary TSCI patients, and is more common compared to the general population. Neurourol. Urodynam. 36:640-647, 2017. © 2016 Wiley Periodicals, Inc.

The Influence of Smoking on the Variations in Carboxyhemoglobin and Methemoglobin During Urologic Surgery.

INTRODUCTION: Surgery is supposed to modulate the production of carbon monoxide by the reduction of heme oxygenase activity or transcriptional regulation of inducible heme oxygenase. On the other hand, the inhalation of tobacco smoke can substantially raise the level of carboxyhemoglobin in the blood. Furthermore, methemoglobin is maintained at a constant level. However, excessive production of methemoglobin relative to total methemoglobin reductase activity results in methemoglobin increase. AIM: The aim of our study was to investigate the perioperative variations of carboxyhemoglobin and methemoglobin during urologic surgeries, and at the same time to evaluate the changes in methemoglobin as a possible indicator of nitric oxide generation. Our second aim was to evaluate the effect of preoxygenation on the level of carboxyhemoglobin and methemoglobin and the influence of blood transfusion on their changes. MATERIAL AND METHODS: The study included 30 patients scheduled for urologic surgery under general endotracheal anesthesia, aged 18-60 years without any history of respiratory disease, divided into two groups. The study group comprised patients who were smoking cigarettes or tobacco pipe, while the control group included non-smokers. In both groups carboxyhemoglobin (COHb) and methemoglobin (MetHb) levels were determined preoperatively, after preoxygenation, and postoperatively. RESULTS: COHb levels were decreased postoperatively in both groups. The average values of COHb between the two groups were statistically significantly different (p=0.00). MetHb levels increased postoperatively in the group of smokers and decreased in the group of non-smokers. There were no statistically significant differences in the average postoperative MetHb levels between the two groups. CONCLUSION: Changes in carboxyhemoglobin and methemoglobin concentrations in arterial blood occur during urologic surgery, although these amplitudes are small when compared with carbon monoxide intoxication and methemoglobinemia. It is likely that organ perfusion and functions are affected by these monoxide gas mediators during urologic surgery.