Efficiency and Diagnostic Utility of CO2 Cystoscopy After Laparoscopic Gynecologic Surgery.

Background and Objectives: This study aimed to compare the efficiency and diagnostic performance of carbon dioxide (CO2) versus saline as a distension medium during routine cystoscopy performed after laparoscopic gynecologic surgery.

We conducted a prospective, comparative study involving patients undergoing total laparoscopic hysterectomy for benign indications. Participants were randomly assigned to undergo diagnostic cystoscopy using either CO2 or saline for bladder distension. Primary outcomes included total cystoscopy duration and time to visualize bilateral ureteral jets. Secondary outcomes were intraoperative detection rates of lower urinary tract injuries and any postoperative urinary complications.

A total of 529 patients were included (CO2 group: 270; 51.1%; saline group: 259; 48.9%). Cystoscopy duration was significantly shorter in the CO2 group compared to the saline group (150 vs 120 seconds; P < .001). Time to visualize ureteral jets was also reduced in the CO2 group (43 seconds; P < .001). One bladder injury and 1 ureteral obstruction were identified intraoperatively and successfully repaired in the same surgical session. The use of CO2 eliminated the need for diuretics or chromatic dyes, streamlining the diagnostic process and potentially reducing costs.

CO2 cystoscopy is a safe, efficient, and diagnostically effective alternative to conventional saline cystoscopy following gynecologic laparoscopy. Its use significantly reduces procedural time without compromising the detection of urinary tract injuries and avoids the need for additional agents such as dyes or diuretics. These findings support the integration of CO2 cystoscopy into routine intraoperative surveillance protocols during minimally invasive gynecologic surgery.

CO2 cystoscopy, Diagnostic efficiency, Gynecologic laparoscopy, Saline distension, Ureteral jet, Urinary tract injury

Lower urinary tract injuries, particularly to the ureters and bladder, represent a significant source of morbidity in gynecologic laparoscopic surgery.1,2 These injuries are especially relevant during complex procedures such as laparoscopic hysterectomy or endometriosis surgery, where anatomical boundaries may be obscured due to prior pelvic surgeries, adhesions, or intraoperative bleeding.3–5 Under such conditions, visual identification of critical structures becomes challenging, increasing the risk of unrecognized damage. Failure to detect these injuries intraoperatively can result in delayed diagnosis, prolonged recovery, and serious medicolegal consequences.6 Conversely, timely identification and repair during surgery can significantly reduce complication rates and improve clinical outcomes.2,7 Although the utility and cost-effectiveness of routine diagnostic cystoscopy remain subjects of debate, evidence from Gilmour et al8 indicates that in the absence of intraoperative cystoscopy, 50% of ureteral injuries and 25% of bladder injuries go undetected during the procedure.9 Diagnostic cystoscopy enables the identification of intravesical bleeding, mucosal lacerations, inadvertent suturing, and—most importantly—the visualization of ureteral jet flow, all within a matter of minutes.10 Despite these benefits, several factors have limited its widespread adoption in gynecologic practice. These include concerns over increased operative time, limited access to dyes for saline-based cystoscopy, and insufficient training in cystoscopic techniques.11 The use of carbon dioxide (CO2) as a distension medium offers a promising alternative. CO2 provides a clear field of view, eliminates the need for dye instillation, and allows real-time evaluation of ureteral jet flow.12 Its ease of use and favorable visualization properties make it particularly suitable for routine use, especially in resource-limited settings. This prospective case-control study aims to compare the operative duration and diagnostic effectiveness of saline versus CO2 as distension media in routine diagnostic cystoscopy performed after benign gynecologic laparoscopic surgery.

This study was designed as a prospective case-control study. Ethical approval was obtained from the relevant institutional Clinical Research Ethics Committee (protocol number and date available upon request). The study was also registered in a publicly accessible clinical trial registry prior to patient enrollment. Written informed consent was obtained from all participants before inclusion. Sample Size Calculation Sample size calculation was performed using G*Power 3.1, assuming a moderate effect size (Cohen’s d = 0.5), 80% power, and a 5% α error. The calculation indicated that a minimum of 128 participants per group would be required. This threshold was exceeded in both groups. Study Population and Exclusion Criteria Between September 2021 and January 2024, a total of 1,260 patients who underwent laparoscopic hysterectomy for benign indications at our tertiary hospital were screened. After applying the predefined exclusion criteria such as incomplete follow-up, histopathological malignancy, or conditions interfering with accurate cystoscopic evaluation, 731 patients (58%) were excluded. The remaining 529 patients (42%) were included in the final analysis (Figure 1). Patients were allocated to 1 of 2 groups based on the distension medium used during diagnostic cystoscopy: the saline group (n = 259; 48.9%) and the CO2 group (n = 270; 51.1%). Allocation was performed preoperatively via a computer-assisted algorithm independent of the surgical team, minimizing selection bias. Baseline and Intraoperative Variables Demographic, clinical, and perioperative data were collected using standardized forms at the time of admission, during surgery, and postoperatively. These included age, parity, previous delivery type and number (categorized as vaginal delivery, 1 cesarean, or 2 or more cesareans), body mass index (BMI), surgical indication, histopathological diagnosis (preoperative and postoperative), estimated blood loss, hemoglobin levels, operation duration, and length of hospital stay. The use of intravenous furosemide was documented when employed to enhance ureteral visualization. It was selectively used during cystoscopy when ureteral jets could not be clearly visualized within the 1-minute observation window, which was based on previous studies indicating that ureteral peristalsis typically occurs 2–6 times per minute under normal physiological conditions to facilitate peristalsis and improve detection.13,14 The complexity of pelvic dissection was assessed intraoperatively and categorized based on predefined criteria. “Low-complexity dissection” was defined as procedures completed using blunt dissection without significant bleeding or anatomical distortion. “High-complexity dissection” referred to cases requiring sharp dissection with cold or electrosurgical instruments, often due to adhesions or distorted pelvic anatomy. Surgeons recorded the classification immediately postoperatively. Surgical Technique All laparoscopic hysterectomies were performed by 3 senior gynecologic surgeons (A.H.I., A.G.K., and E.T.). A standardized lateral approach for bladder dissection was applied in every case. All surgeries aimed for an intraperitoneal approach, with the retroperitoneum opened only when necessary. In patients with suspected endometriosis or significant adhesions, ureterolysis was performed beginning from the lateral peritoneum and progressing medially to protect the ureters. Following laparoscopic hysterectomy, cystoscopic evaluation was performed using either CO2 or saline as the bladder distension medium, depending on group allocation. In both protocols, the bladder was emptied and the Foley balloon deflated prior to instrumentation. Bladder insufflation was performed using a 5-mm suprapubic trocar and a Foley catheter to ensure adequate distension and optimal visualization during CO2 cystoscopy (Figure 2). In the CO2 group, the catheter was connected to a CO2 insufflator set at 8 mmHg pressure and 3 L/min flow. Once the desired pressure was reached, the flow was stopped and the catheter removed. In the saline group, 250 cc of sterile saline was instilled into the bladder via gravity through the Foley catheter before removal. In both groups, a 5-mm optic was introduced transurethrally to inspect the bladder mucosa and observe ureteral jets, starting with the right orifice followed by the left. Each ureter was monitored for a maximum of 1 minute to detect jet flow. If no jet was visualized within this period and the patient had no contraindications, intravenous furosemide was administered to enhance ureteral peristalsis. Following jet assessment, the bladder was systematically evaluated for trauma, bleeding, or mucosal abnormalities. Once inspection was complete, the optic was withdrawn, the Foley catheter reinserted, and the bladder decompressed. To facilitate visualization of ureteral jets, no dyes or contrast agents were used during cystoscopy, ensuring that the observation relied solely on natural urine flow. Statistical Analysis All analyses were conducted using IBM SPSS Statistics v29 (IBM Corp., Armonk, NY). Descriptive statistics were presented as mean ± standard deviation, median (min–max), or frequency (%). Normal distribution of numerical variables was assessed via the Shapiro-Wilk test, and variance homogeneity with Levene’s test. Between-group comparisons were made using independent samples t test or Mann-Whitney U test, depending on distribution. χ2 tests (Pearson’s χ2, Yates correction, Fisher-Freeman-Halton exact test) were used for categorical variables. Significant results in χ2 analyses were followed by pairwise comparisons using Bonferroni-corrected z-tests. A P-value < .05 was considered statistically significant.

A total of 529 patients undergoing laparoscopic hysterectomy were included in the final analysis, with 259 (48.9%) assigned to the saline cystoscopy group and 270 (51.1%) to the CO2 cystoscopy group. Baseline characteristics—including age, parity, BMI, and previous delivery type—were comparable between the 2 groups (all P > .05). Vaginal delivery was recorded in 70.6% of patients in the saline group and 70.3% in the CO2 group. The proportion of women with more than 2 prior cesarean sections was low and statistically similar (2.3% vs 3.7%; P = .600). Surgical indications were evenly distributed (P = .662), with uterine fibroids being the most common diagnosis in both groups, followed by abnormal uterine bleeding, endometriosis or chronic pelvic pain, endometrial hyperplasia, and pelvic organ prolapse. Preoperative pathological assessments revealed no significant difference in the incidence of premalignant lesions (P = .403), and the presence and severity of intraoperative adhesions were also similar between groups (P = .467) (Table 1). Table 1. | Variable | Saline Group (n = 259) | CO2, Group (n = 270) | P-Value | |---|---|---|---| | Age (years), mean ± SD | 50.2 ± 7.1 | 51.2 ± 8.6 | .156 | | Parity, median | 2 (0–5) | 2 (0–4) | .810 | | BMI (kg/m²), mean ± SD | 24.80 ± 2.18 | 24.51 ± 2.26 | .132 | | Delivery type | .600 | || | Vaginal delivery, n (%) | 183 (70.6%) | 190 (70.3%) | | | 1 Cesarean sections, n (%) | 70 (27.0%) | 70 (25.9%) | | | 2 or more Cesarean sections, n (%) | 6 (2.3%) | 10 (3.7%) | | | Surgery indications | .662 | || | Myoma uteri, n (%) | 130 (50.2%) | 133 (49.3%) | | | AUB, n (%) | 48 (18.5%) | 39 (14.4%) | | | Endometriosis/CPP, n (%) | 36 (13.9%) | 45 (16.7%) | | | Hyperplasia, n (%) | 26 (10.0%) | 30 (11.1%) | | | Prolapse, n (%) | 19 (7.3%) | 23 (8.5%) | | | Preop benign pathology, n (%) | 210 (81.1%) | 211 (78.1%) | .403 | | Preop premalignant pathology, n (%) | 49 (18.9%) | 59 (21.9%) | | | Intraoperative adhesions | .467 | || | None, n (%) | 237 (91.5%) | 240 (88.9%) | | | Mild, n (%) | 11 (4.2%) | 18 (6.2%) | | | Severe, n (%) | 11 (4.2%) | 12 (4.4%) | Table 2 summarizes intraoperative and postoperative outcomes. The use of diuretics during cystoscopy was significantly higher in the saline group than in the CO2 group (12.4% vs 3.3%; P < .001). Estimated blood loss and hemoglobin levels, both pre and postoperatively, did not differ significantly between groups (P = .091, P = .228, and P = .498, respectively). Table 2. | Variable | Saline Group (n = 259) | CO2, Group (n = 270) | P-Value | |---|---|---|---| | Diuretic use, n (%) | 32 (12.4%) | 9 (3.3%) | <.001 | | Estimated blood loss (mL), median (min–max) | 75 (30–240) | 80 (20–240) | .091 | | Preoperative Hb (g/dL), mean ± SD | 12.38 ± 1.46 | 12.54 ± 1.51 | .228 | | Postoperative Hb (g/dL), mean ± SD | 10.95 ± 1.49 | 11.05 ± 1.52 | .498 | | Ureteral jet visualization time (seconds), median (min–max) | 85 (30–240) | 43 (22–220) | <.001 | | Cystoscopy duration (seconds), median (min–max) | 150 (60–270) | 120 (50–250) | <.001 | | Total operative time (minutes), median (min–max) | 130 (27–300) | 120 (25–260) | .019 | | Length of hospital stay (hours), median (min–max) | 52 (12–240) | 52 (10–100) | .841 | The median time to visualize ureteral jets was significantly longer in the saline group (85 seconds) compared to the CO2 group (43 seconds; P < .001) (Figure 3). Similarly, total cystoscopy duration was longer in the saline group (150 vs 120 seconds; P < .001) (Figure 4). Operative time was also significantly greater in the saline group (130 vs 120 minutes; P = .019). However, the length of hospital stay was similar between the 2 groups (P = .841). In terms of procedural complications, 1 patient in the saline group was found to have a suture located away from the trigone within the bladder. Laparoscopic re-exploration revealed that the stitch had inadvertently penetrated the vaginal cuff during closure. The cuff was reopened, inspected, and resutured. This event was categorized as a Clavien-Dindo grade IIIb complication. In the CO2 group, 1 patient failed to exhibit a left ureteral jet despite intravenous furosemide administration. Urology consultation revealed a focal narrowing of the distal ureter approximately 3–4 cm from the bladder wall. Laparoscopic reassessment identified a hemostatic suture causing partial ureteral kinking. The suture was revised, and the event was similarly classified as a Clavien-Dindo grade IIIb complication.

Cystoscopy following laparoscopic surgery especially gynecologic procedures is a valuable tool for the early detection of lower urinary tract injuries, particularly ureteral or bladder trauma, which may otherwise go unnoticed intraoperatively.15 Timely diagnosis is critical in preventing long-term morbidity and avoiding costly, delayed interventions. In this study, we demonstrated that CO2 cystoscopy is a faster and potentially more cost-effective alternative to conventional saline cystoscopy. The significantly shorter time required to visualize ureteral jets and complete the procedure using CO2 supports its feasibility and efficiency as a diagnostic adjunct. Numerous studies have advocated for routine cystoscopy following gynecologic surgery to enhance the intraoperative detection of urinary tract injuries.15–17 For instance, Teeluckdharry et al,18 in a 2015 meta-analysis, emphasized that routine cystoscopy significantly increases the detection rate of such injuries during surgery. Despite these benefits, some authors argue that routine cystoscopy does not necessarily improve the overall detection rate of urinary tract injuries and therefore question its inclusion in all gynecologic endoscopic procedures.16,17 These critics often support a more selective approach, especially in low-risk patients or in cases of less complex surgeries. Nonetheless, although the reported incidence of ureteral and bladder injuries remains relatively low (approximately 0.7% and 0.9%, respectively), the clinical consequences of missed injuries can be severe, including fistula formation, urinary tract infections, and irreversible renal damage.5–10 In our cohort, only 1 bladder injury and 1 ureteral complication were identified—both detected intraoperatively and corrected in the same surgical session without the need to awaken the patient. Given its high sensitivity and ease of integration into the laparoscopic workflow, diagnostic cystoscopy—particularly when CO2 is used as a distension medium—remains a valuable adjunct to ensure patient safety without significantly prolonging operative time or increasing procedural complexity. Moreover, the transition from a 10-mm laparoscope to a 5-mm cystoscope through the urethra can be performed rapidly, minimizing additional anesthesia time and avoiding increased resource utilization. Simple intraoperative adjustments, such as draining residual urine via Foley catheter or elevating the vaginal cuff using ring forceps, can further facilitate optimal visualization of the ureteral orifices and contribute to a more efficient cystoscopic evaluation. A key advantage of CO2 cystoscopy is that it eliminates the need for additional agents such as intravenous diuretics or chromatic dyes, which are often employed to facilitate ureteral jet visualization in fluid-based systems.7,9,12 Agents like indigo carmine, phenazopyridine, or sodium fluorescein not only introduce added costs and potential allergic risks but may also be unavailable due to supply chain issues.11 Moreover, with increasing surgical duration, patients typically receive larger volumes of intravenous fluids, leading to diluted urine that becomes visually indistinguishable from the instilled saline—thereby making ureteral jet observation more challenging. In contrast, the use of a gaseous medium such as CO2 provides a clear visual interface unaffected by urine clarity or color, enhancing diagnostic accuracy.12 Consistent with these theoretical advantages, our study demonstrated that both the time required for ureteral jet visualization and overall cystoscopy duration were significantly shorter in the CO2 group compared to the saline group. However, it is important to acknowledge that the presence of a ureteral jet does not entirely rule out partial obstructions or thermal injuries, and not all bladder injuries may be visible—except those that are readily identifiable intraoperatively. Nonetheless, in our study, aside from the 2 documented cases, no additional late-onset lower urinary tract complications were observed among the remaining patients. This finding further supports the utility and clinical value of even a brief cystoscopic evaluation using CO2 as a distension medium. Beyond improved visualization, CO2 is widely regarded as a safe medium when used in controlled volumes.19 Its high solubility compared to ambient air significantly reduces the risk of embolic events.20 This property has led to its widespread use in laparoscopy and hysteroscopy, and even in intravesical procedures.16,17 In our study, no signs of gas-related complications, including embolism or hemodynamic instability, were observed, reinforcing its safety profile when applied in short-duration cystoscopic evaluations following gynecologic surgery. This study presents several strengths. First, it is among the few prospective comparative analyses evaluating the efficacy of CO2 versus saline as a distension medium for routine diagnostic cystoscopy following surgery. The standardized surgical technique and consistent intraoperative protocol, carried out by a single experienced surgical team, minimized variability and enhanced the reliability of the findings. However, the study is not without limitations. The sample size, although sufficient to detect statistically significant differences in procedural durations, limits the generalizability of findings regarding rare complications. Furthermore, while patients with distorted pelvic anatomy or a history of complex pelvic surgery were excluded to preserve group homogeneity, this exclusion may limit the applicability of our findings to higher-risk surgical populations. In conclusion, CO2 cystoscopy appears to be a safe, efficient, and cost-effective alternative to conventional diagnostic cystoscopy procedures following gynecologic surgery. Its use significantly reduces visualization time and eliminates the need for additional agents such as dyes or diuretics, all while maintaining diagnostic accuracy. Although lower urinary tract injuries are relatively rare, their early detection and prompt intraoperative correction—as demonstrated in our cohort—emphasize the clinical relevance of even brief cystoscopic evaluations. Given its seamless integration into the surgical workflow and favorable safety profile, CO2 cystoscopy may serve as a valuable adjunct for enhancing intraoperative surveillance in selected gynecologic procedures. Future multicenter trials involving larger and more heterogeneous populations, along with extended follow-up, are warranted to confirm these findings and guide broader implementation. Footnotes Disclosure: All authors contributed to the study design and methodology. A.H.İ. conceived and designed the study, supervised the entire research process, oversaw data analysis, and thoroughly revised the manuscript for scientific accuracy and content. A.G.K. coordinated the ethics approval and patient selection process, contributed to study planning, participated in data interpretation, and led the critical revision of the manuscript. S.K. assisted with data collection and preliminary analysis and contributed to manuscript drafting. A.K. supported study planning and provided technical input during the writing process. O.C. offered urological expertise for the evaluation of cystoscopic findings and assisted in the clinical interpretation of the data. E.T. contributed to language editing and formatting of the manuscript and participated in the final review and approval. Data availability: The data which support the fndings of our study are not openly available due to reasons of privacy restrictions and sensitivity. The data are available from the corresponding author upon reasonable request. Ethical approval: Ethical approval was obtained from the Clinical Research Ethics Committee of Izmir Tepecik Training and Research Hospital (Protocol Number: 2021/0502, date: 11/6/2021), and was registered at ClinicalTrials.gov (Identifier: NCT06278753) prior to patient enrollment. Informed consent was obtained from all participants before inclusion. Conflict of interests: none. Funding sources: none.

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