Incidence of Iatrogenic Ureteral Injury During Open and Laparoscopic Colorectal Surgery: A Single Center Experience and Review of the Literature. Surg Laparosc Endosc Percutan Tech. 2016;26:513-515. [PMID: 27846171 DOI: 10.1097/sle.0000000000000335]

Iatrogenic urinary injuries in colorectal surgery: outcomes and risk factors from a nationwide cohort

BACKGROUND

Iatrogenic urinary injury (IUI) can lead to significant complications after colorectal surgery, especially when diagnosis is delayed. This study analyzes risk factors associated with IUI and delayed IUI among patients undergoing colorectal procedures.

METHODS

Adults undergoing colorectal surgery between 2012 and 2021 were identified in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP®) database. Multivariable regression analysis was used to determine risk factors and outcomes associated with IUI and delayed IUI.

RESULTS

Among 566,036 patients, 5836 patients (1.0%) had IUI after colorectal surgery, of whom 236 (4.0%) had delayed IUI. Multiple preoperative risk factors for IUI and delayed IUI were identified, with disseminated cancer [adjusted odds ratio (aOR) 1.4, 95% confidence interval (CI) 1.2-1.5; p < 0.001] and diverticular disease [aOR 1.1, 95% CI 1.0-1.2; p = 0.009] correlated with IUI and increased body mass index [aOR 1.6, 95% CI 1.2-2.1; p = 0.003] and ascites [aOR 5.6, 95% CI 2.1-15.4; p = 0.001] associated with delayed IUI. Laparoscopic approach was associated with decreased risk of IUI [aOR 0.4, 95% CI 0.4-0.5; p < 0.001] and increased risk of delayed IUI [aOR 1.8, 95% CI 1.4-2.5; p < 0.001]. Both IUI and delayed IUI were associated with significant postoperative morbidity, with severe multiorgan complications seen in delayed IUI.

CONCLUSIONS

While IUI occurs infrequently in colorectal surgery, unrecognized injuries can complicate repair and cause other negative postoperative outcomes. Patients with complex intra-abdominal pathology are at increased risk of IUI, and patients with large body habitus undergoing laparoscopic procedures are at increased risk of delayed IUI.

Utility and challenges of ureteral visualization using a fluorescent ureteral catheter in high risk surgeries for colorectal cancer

BACKGROUND

Ureteral injury occurs in 0.3-1.5% of colorectal cancer surgeries. Devices to visualize the ureteral course and avoid ureteral injury are required for minimally invasive surgery (MIS). The NIRC™ fluorescent ureteral catheter (FUC) is a versatile ureteral visualization device currently available in Japan that can be used in combination with a variety of laparoscopic and robotic systems. In this study, we examined the outcomes of high-risk patients who underwent colorectal cancer surgery with FUC insertion.

METHODS

One hundred forty-one patients who underwent MIS for colorectal cancer and colorectal cancer recurrence at our institute between January 2021 and May 2024 underwent preoperative FUC insertion because of the high risk of ureteral injury and surgical difficulty. For these patients, patient background data and short-term outcomes were examined. The results are expressed as the median and interquartile range.

RESULTS

Age, 70 [60-78]; M:F(n), 84:57; BMI, 22.1 [19.7-24.7]; T4 (TNM classification), 52 cases (36.9%); preoperative intestinal obstruction, 45 cases (31.9%); abscess formation, 30 cases (21%); surgical history, 70 cases (50%); recurrent cancer, 14 cases (9.9%); preoperative chemo-radiotherapy, 28 cases (19.9%); time required for FUC insertion, 12 [9-19] minutes; operation time, 412 [309-552] minutes; blood loss, 10 [5-30] ml; open conversion, 0 cases; postoperative hospitalization, 12 [9-17.5]; circumferential resection margins < 1 mm (rectal surgery), 4/87 cases (4.6%); comorbidities, 0 ureteral injury, 1 urethral injury during FUC insertion (0.7%) and 16 CD Grade 3 or higher cases (11%).

CONCLUSIONS

FUC may improve the safety of MIS and reduce blood loss in addition to preventing ureteral injury and is expected to have oncological advantages for ensuring the margin of the tumor without fear of ureteral injury. However, the time required for and complications associated with FUC are challenging. New methods for less invasive and easier ureteral visualization may be needed.

Developments in the Use of Indocyanine Green (ICG) Fluorescence in Colorectal Surgery

Indocyanine Green (ICG) has significantly advanced minimally invasive surgery. It is widely recognized for its ability to visualize blood vessel patency in real-time across various surgical specialties. While its primary use in colorectal surgery is to evaluate anastomoses for leaks, numerous other applications have been documented in the literature. In this review, we aim to explore both established and emerging applications of ICG fluorescence in colorectal surgery, with the goal of improving patient outcomes. This includes preoperative tumor marking and the detection of metastatic disease. Some applications, such as lymphatic mapping, require further research to determine their impact on clinical practices. Conversely, others, like the intraoperative localizations of ureters, necessitate additional procedures and are not yet widely accepted by the surgical community. However, the development of alternative compounds could offer better solutions. Future research should focus on areas like quantitative ICG and protocol standardization in prospective multicenter studies.

Can preoperative ureteral stent placement help in the intraoperative identification of iatrogenic ureteral injury?

BACKGROUND

The benefits of prophylactic ureteral stent placement during colorectal surgery remain controversial. This study aimed to determine the incidence of ureteral injury in colorectal operations, assess the complications associated with stent usage, and determine whether their use leads to earlier identification and treatment of injury.

METHODS

This was a retrospective study of patients undergoing colorectal abdominal operations between 2015 and 2021. Variables were examined for possible association with ureteral stent placement. The primary study endpoint was ureteral injury identified within 30 days postoperatively.

RESULTS

Of 6481 patients who underwent colorectal surgery, 970 (15%) underwent preoperative ureteral stent placement. The use of stents was significantly associated with a higher American Society of Anesthesiologists classification, wound classification, and longer duration of surgery. A ureteral injury was identified in 28 patients (0.4%). Of these patients, 13 had no stent, and 15 had preoperative stents placed. After propensity matching, stent use was associated with an increased risk of hematuria and urinary tract infection. Ureteral injury was identified intraoperatively in 14 of 28 patients (50.0%) and was not associated with ureteral stent use (P = .45).

CONCLUSION

Iatrogenic ureteral injury was uncommon, whereas preoperative stent placement was relatively frequent. Earlier recognition of iatrogenic ureteral injury is not an expected advantage of preoperative ureteral stent placement.

Preventing iatrogenic ureteral injury in colorectal surgery: a comprehensive and systematic review of the last 2 decades of literature and future perspectives

Iatrogenic ureteral injury (IUI) during colorectal surgery is a rare complication but related to a serious burden of morbidity. This comprehensive and systematic review aims to provide a critical overview of the most recent literature about IUI prevention techniques in colorectal surgery. We performed a comprehensive and systematic review of studies published from 2000 to 2022 and assessed the use of techniques for ureteral injury prevention and intraoperative localization. 26 publications were included, divided into stent-based (prophylactic/lighted ureteral stent and near-infrared fluorescent ureteral catheter [PUS/LUS/NIRFUC]) and fluorescent dye (FD) groups. Costs, the percentage and number of IUIs detected, reported limitations, complication rates and other outcome points were compared. The IUI incidence rate ranged from 0 to 1.9% (mean 0.5%) and 0 to 1.2% (mean 0.3%) in the PUS/LUS/NIRFUC and FD groups, respectively. The acute kidney injury (AKI) and urinary tact infection (UTI) incidence rate ranged from 0.4 to 32.6% and 0 to 17.3%, respectively, in the PUS/LUS/NIRFUC group and 0-15% and 0-6.3%, respectively, in the FD group. Many other complications were also compared and descriptively analyzed (length-of-stay, mortality, etc.). These techniques appear to be feasible and safe in select patients with a high risk of IUI, but the delineation of reliable guidelines for preventing IUI will require more randomized controlled trials.

Iatrogenic ureteral injury: What should the digestive surgeon know?

PURPOSE OF THE STUDY

Iatrogenic ureteral injury (IUI) is a rare but formidable complication of any abdominal or pelvic surgery. The aim of this study was to describe the epidemiology of IUI in colorectal surgery in the Basse-Normandie region over the period 2004-2022, as well as to review the literature on the management of this complication.

MATERIALS AND METHODS

This multicenter retrospective analysis of clinical data (medical records and operative reports) concerned 22 patients (13 men and 9 women) who suffered an IUI during colorectal surgery between 2004 and 2022. Ureteral resections for oncological purposes and endoluminal instrumental injuries (post-ureteroscopy) were excluded from the study. We also carried out a review of the literature concerning the incidence of IUI in colorectal surgery.

RESULTS

The incidence of IUI was 0.27% over the study period (22 ureteral injuries out of 8129 colorectal procedures). Colorectal cancer and sigmoid diverticulitis were the dominant surgical indications (85% of cases). Proctectomy and left colectomy were the most performed resection procedures (75% of cases). Surgery was scheduled in 68% of cases. The approach was open laparotomy in 59% and laparoscopy in 41% of cases. The IUI involved the left ureter in 63% of cases and the pelvic ureter in 77% of cases. Conservative endoscopic treatment by insertion of a double-J catheter stent had a success rate of 87.5%. Surgical repairs consisting of re-implantation techniques and uretero-ureteral anastomosis had a success rate of 75%. The nephrectomy rate was 13.6% (3/22) and the mortality rate 9% (2/22). A literature review identified sixteen studies, where the incidence of IUI varied from 0.1 to 4.5%.

FINDINGS

IUI occurring during colorectal surgery is a rare occurrence but remain a formidable complication. No means of prevention has proven its effectiveness to date, but guidance devices using illuminated ureteral catheters or dyes seem to constitute a promising approach. Injuries to the left pelvic ureter are the most common, and the majority can be treated endoscopically if diagnosed early.

Risk stratification of acute kidney injury (AKI) following ureteral stent insertion for colorectal surgery

INTRODUCTION AND OBJECTIVES

Ureteral stents have long been utilized during colorectal resections to assist in the identification of ureters intraoperatively and mitigate risk of ureteral injury. As these procedures have shifted toward robot-assisted laparoscopic methods, lighted stents have increasingly been used. The incidence of acute kidney injury (AKI) following bilateral ureteral stent placement has been reported to be as high as 41.9%. We sought to identify our single-institution risk and determine the extent to which age, sex, and stent type affected incidence of AKI.

METHODS

A retrospective analysis was performed at a single community hospital of all open and robotic-assisted laparoscopic colorectal surgeries from October 2012 to April 2022. If requested, ureteral stents were placed bilaterally by a urologist and later removed by the surgeon. Non-lighted stents used were 5 Fr whistle-tip (BARD); lighted stents were 6 Fr with a fiberoptic core (STRYKER). Kidney failure was described as a rise of creatinine to ≥ 1.5 times the preoperative value, per KDIGO guidelines.

RESULTS

633 consecutive colorectal surgeries were evaluated, with no stents placed in 237 cases, non-lighted stents placed in 137 cases, and lighted stents placed in 259 cases. No ureteral injuries were observed. Overall incidence of AKI for non-stented surgeries was 0.8% vs 5.8% for non-lighted stents and 5.8% for lighted stents. Patient age was the most significant factor in AKI incidence: for patients under 60, there was no statistical difference in AKI incidence for stented vs non-stented procedures (2.2% vs 1.1%). For patients over 60, the risk of AKI was 10.5% for stented vs 0.7% for non-stented. Female patients had statistically significant risk differences, with AKI incidence of 7.1% stented vs 0.0% non-stented. AKI completely resolved in all cases, regardless of cohort.

CONCLUSIONS

In patients under age 60, the use of stents was not associated with an increased risk of AKI. For women and those over 60, stents pose a higher risk of transient AKI. Overall incidence of AKI in our larger and single-institution community hospital population was significantly lower than reported in other studies. No statistical difference was observed, overall, in AKI incidence between lighted and non-lighted stents.

2023 WSES guidelines for the prevention, detection, and management of iatrogenic urinary tract injuries (IUTIs) during emergency digestive surgery

Iatrogenic urinary tract injury (IUTI) is a severe complication of emergency digestive surgery. It can lead to increased postoperative morbidity and mortality and have a long-term impact on the quality of life. The reported incidence of IUTIs varies greatly among the studies, ranging from 0.3 to 1.5%. Given the high volume of emergency digestive surgery performed worldwide, there is a need for well-defined and effective strategies to prevent and manage IUTIs. Currently, there is a lack of consensus regarding the prevention, detection, and management of IUTIs in the emergency setting. The present guidelines, promoted by the World Society of Emergency Surgery (WSES), were developed following a systematic review of the literature and an international expert panel discussion. The primary aim of these WSES guidelines is to provide evidence-based recommendations to support clinicians and surgeons in the prevention, detection, and management of IUTIs during emergency digestive surgery. The following key aspects were considered: (1) effectiveness of preventive interventions for IUTIs during emergency digestive surgery; (2) intra-operative detection of IUTIs and appropriate management strategies; (3) postoperative detection of IUTIs and appropriate management strategies and timing; and (4) effectiveness of antibiotic therapy (including type and duration) in case of IUTIs.

Laparoscopic versus open surgery for colonoscopic perforation: A systematic review and meta-analysis

BACKGROUND

The efficacy of laparoscopic surgery (LS) for the treatment of colonoscopic perforation is still controversial. The purpose of this meta-analysis was to evaluate the effectiveness and safety of LS versus open surgery (OS) for colonoscopic perforation.

METHODS

All clinical trials that compared laparoscopic with OS for colonoscopic perforation published in English were identified in PubMed, EMBASE, Web of Science, and Cochrane Library searches. A modified scale was used to assess the quality of the literature. We analyzed the age, sex ratio, aim of colonoscopy, history of abdominopelvic surgery, type of procedure, size of perforation, operation time, postoperative fasting time, hospital stay, postoperative complication morbidity, and postoperative mortality. Meta-analyses were performed using weighted mean differences for continuous variables, and odds ratios for dichotomous variables.

RESULTS

No eligible randomized trials were identified, but eleven nonrandomized trials were analyzed. In the pooled data of 192 patients who underwent LS and 131 OS, there were no significant differences in age, sex ratio, aim of colonoscopy, history of abdominopelvic surgery, perforation size, and operative time between the groups. LS group had shorter time of hospital stay and postoperative fasting time, less postoperative complication morbidity, but there were no significant difference in postoperative mortality rate between LS group and OS group.

CONCLUSIONS

Based on the current meta-analysis, we conclude that LS is a safe and efficacious technique for colonoscopic perforation, with fewer postoperative complications, less hospital mortality, and faster recovery compared with OS.

Evaluation of the Utilization of Near-Infrared Fluorescent Contrast Agent ASP5354 for In Vivo Ureteral Identification in Renal Diseases Using Rat Models of Gentamicin-Induced Acute Kidney Injury

ASP5354 was recently developed as a near-infrared fluorescence (NIRF) contrast agent for intraoperative ureteral identification, and its use has been evaluated in healthy animals. However, the utilization of ASP5354 for ureteral identification has not been evaluated in animals with renal injury. In this study, we assessed the application of ASP5354 for ureteral imaging using rat models of gentamicin-induced mild, moderate, and severe acute kidney injury (AKI), using a clinically available NIRF detection system. NIRF was detected in the abdominal cavity and ureters after laparotomy, and the efficiency of ASP5354 was evaluated based on the NIRF signal intensity over 60 min. After the intravenous injection of ASP5354 into rats with mild or moderate AKI, the ureters were clearly imaged at a high ratio of NIRF intensity in the ureter to that in the tissues around the ureter. Six days after intravenous injection, the use of ASP5354 in rats with moderate AKI did not affect the biochemical kidney functions or histopathological conditions of the kidney tissues, as compared to those with no injection of ASP5354. In rats with severe AKI, ureteral imaging was not effective due to the relatively strong NIRF expression in the tissues around the ureters. These data indicate that ASP5354 holds potential as a contrast agent for intraoperative ureteral identification in patients with limited renal injury.

Iatrogenic injury of the urinary tract during salvage procedures for pelvic sepsis: Experience of a national referral centre

AIM

This study aimed to determine the incidence, consequences and outcomes of iatrogenic urinary tract injury (IUI) during salvage surgery for pelvic sepsis.

METHOD

Patients who underwent salvage surgery for pelvic sepsis after prior low anterior resection or Hartmann's procedure for rectal cancer were prospectively maintained in a database between 2010 and 2020 and reviewed retrospectively. The primary endpoint was the incidence of IUI. Secondary endpoints were timing of diagnosis (intra- vs. postoperative), reinterventions related to the IUI and healing of IUI.

RESULTS

In total 126 consecutive patients were included, and IUI occurred in 13 patients (10%). A ureteric injury occurred in eight patients, bladder injury in four patients and a urethral injury in one patient. All patients with an IUI had radiotherapy as neoadjuvant treatment. The IUI was diagnosed postoperatively in 63% (n = 8/13) with a median duration between surgery and diagnosis of the IUI of 10 days (IQR: 6-15). The median number of reinterventions was five (range 1-31) in the group with a postoperative diagnosis and one (range 0-1) in the group with an intraoperative diagnosis. Four patients required a surgical reintervention, all concerning injuries diagnosed postoperatively. At the end of follow-up, 85% of patients (n = 11/13) had a healed IUI.

CONCLUSION

Iatrogenic urinary tract injury is not uncommon in salvage procedures for pelvic sepsis, even in an experienced tertiary referral centre. Most injuries were diagnosed postoperatively which affects the severity of these complications, emphasising the need to improve intraoperative diagnostic modalities.

Computer-Assisted Differentiation between Colon-Mesocolon and Retroperitoneum Using Hyperspectral Imaging (HSI) Technology

Complete mesocolic excision (CME), which involves the adequate resection of the tumor-bearing colonic segment with “en bloc” removal of its mesocolon along embryological fascial planes is associated with superior oncological outcomes. However, CME presents a higher complication rate compared to non-CME resections due to a higher risk of vascular injury. Hyperspectral imaging (HSI) is a contrast-free optical imaging technology, which facilitates the quantitative imaging of physiological tissue parameters and the visualization of anatomical structures. This study evaluates the accuracy of HSI combined with deep learning (DL) to differentiate the colon and its mesenteric tissue from retroperitoneal tissue. In an animal study including 20 pig models, intraoperative hyperspectral images of the sigmoid colon, sigmoid mesentery, and retroperitoneum were recorded. A convolutional neural network (CNN) was trained to distinguish the two tissue classes using HSI data, validated with a leave-one-out cross-validation process. The overall recognition sensitivity of the tissues to be preserved (retroperitoneum) and the tissues to be resected (colon and mesentery) was 79.0 ± 21.0% and 86.0 ± 16.0%, respectively. Automatic classification based on HSI and CNNs is a promising tool to automatically, non-invasively, and objectively differentiate the colon and its mesentery from retroperitoneal tissue.

Two cases of an internal hernia after laparoscopic sigmoid resection

Two patients with a laparoscopic resection of the sigmoid colon in their surgical history were diagnosed with an internal hernia because of a mesenteric gap underneath the descending neocolon. While the first case demonstrated a strongly symptomatic patient with a closed-loop obstruction of the small bowel, the second case was less obvious and correct diagnosis was achieved after a few weeks by finally performing a diagnostic laparoscopy. Since internal hernias after laparoscopic sigmoid resection are a rare complication and as presented in the second case can display very unspecific symptoms, the surgeon’s awareness is not immediately raised towards it. Therefore, an asymptomatic internal hernia bears a constant risk of a life-threatening outcome allowing to recommend an initial closure of the mesenteric gap. In both cases, successful treatment was achieved by surgery and intraoperatively closing the remaining mesenteric gap. Subsequently recovery and follow-up were uneventful.

Fluorescent ureterography with indocyanine green in laparoscopic colorectal surgery: A safe method to prevent intraoperative ureteric injury

Intraoperative injuries to the ureter can occur in complicated colorectal and gynaecologic procedures in minimal access surgery. The majority of these go unrecognised at the time of the operation, which can be disastrous to the patient. The routine use of ureteric stents is controversial, with some studies showing that stents only enable detection of ureteric injury but do not prevent it. Fluorescent image-guided surgery with indocyanine green (ICG) to visualise the ureter is a relatively new technique. We report our method of visualisation of the ureter in two patients undergoing laparoscopic anterior resection and Hartmann procedure, respectively. After induction of anaesthesia, retrograde catheterisation of both ureters was performed by the urologist. 2.5 mg ICG was injected into each catheter at the start of the procedure. Both ureters were visualised very well throughout the procedure with no post-operative complications. This technique using ICG adds visual cues to make up for the loss of tactile feedback, making it a safe strategy to prevent intraoperative ureteric injury.

Nerve autofluorescence in near-ultraviolet light markedly enhances nerve visualization in vivo

BACKGROUND

During surgery, surgeons must accurately localize nerves to avoid injuring them. Recently, we have discovered that nerves fluoresce in near-ultraviolet light (NUV) light. The aims of the current study were to determine the extent to which nerves fluoresce more brightly than background and vascular structures in NUV light, and identify the NUV intensity at which nerves are most distinguishable from other tissues.

METHODS

We exposed sciatic nerves within the posterior thigh in five 250-300 gm Wistar rats, then observed them at four different NUV intensity levels: 20%, 35%, 50%, and 100%. Brightness of fluorescence was measured by fluorescence spectroscopy, quantified as a fluorescence score using Image-J software, and statistically compared between nerves, background, and both an artery and vein by unpaired Student's t tests with Bonferroni adjustment to accommodate multiple comparisons. Sensitivity, specificity, and accuracy were calculated for each NUV intensity.

RESULTS

At 20, 35, 50, and 100% NUV intensity, fluorescence scores for nerves versus background tissues were 117.4 versus 40.0, 225.8 versus 88.0, 250.6 versus 121.4, and 252.8 versus 169.4, respectively (all p < 0.001). Fluorescence scores plateaued at 50% NUV intensity for nerves, but continued to rise for background. At 35%, 50%, and 100% NUV intensity, a fluorescence score of 200 was 100% sensitive, specific, and accurate identifying nerves. At 100 NUV intensity, artery and vein scores were 61.8 and 60.0, both dramatically lower than for nerves (p < 0.001).

CONCLUSIONS

At all NUV intensities ≥ 35%, a fluorescence score of 200 is 100% accurate distinguishing nerves from other anatomical structures in vivo.

Fluorescence Imaging in Colorectal Surgery: An Updated Review and Future Trends

Fluorescence imaging in colorectal surgery is considered a novel predominantly intraoperative method of ensuring a greater surgical success. The use of fluorescence is linked to advanced tumor visualization and projection of its lymphatics, both vessels and nodes, which results in a higher chance of achieving a total excision. Additionally, iatrogenic complications prove to be reduced using fluorescence during the surgical excision. The combination of fluorescence and artificial intelligence to better facilitate oncological surgery will soon become an established approach in operating rooms worldwide.

Fluorescence ureteral navigation during laparoscopic surgery for clinically suspected stage T4 colorectal cancer: A cohort study

BACKGROUND

Approximately 15% of patients with colorectal cancer present with locally advanced tumors (T4 stage). Laparoscopic surgery for stage T4 disease has not yet been established. The near-infrared ray catheter fluorescent ureteral catheter (NIRFUC) is a new device that uses near-infrared fluorescence resin. We examined the utility of fluorescence ureteral navigation (FUN) with the NIRFUC during laparoscopic surgery for stage T4 colorectal cancer.

MATERIALS AND METHODS

Patients with stage T4 colorectal cancer (n = 143, from January 2017 to March 2021) were divided into a T4FUN + group, in which the NIRFUC was used (n = 21), and a T4FUN- group, in which the NIRFUC was not used (n = 122). Short-term outcomes were compared between the groups. Next, the laparoscopic surgery rate and incidence of ureteral injury from January 2017 to March 2021 were compared between the T4FUN- group and the non-stage T4FUN- group (n = 434, from January 2017 to March 2021), in which fluorescence ureter navigation was not used.

RESULTS

Rectal cancer, stage T4b disease, and invasion into the urinary tract were observed more often in the T4FUN + group than in the T4FUN- group. In the comparisons of the T4FUN + versus T4FUN- groups, the operative time was 398 (161-1090) vs. 256 (93-839) minutes, the blood loss was 10 (1-710) vs. 25 (0-1360) ml, and the ratio of laparoscopic surgery to open surgery was 21:0 vs. 79:43. Postoperative complications (Clavien-Dindo grade ≥ III) were present in 2 (10%; 0 ureteral injury) patients in the T4FUN + group and 13 (11%; 2 ureteral injury) patients in the T4FUN- group. In the T4FUN + group, the operative time was longer (p < 0.0001), but the laparoscopic ratio was higher (p = 0.0002), and the blood loss volume and incidence of ureteral injury tended to be lower. In the comparisons of the T4FUN- versus non-stage T4FUN- groups, the ratio of laparoscopic surgery to open surgery was 79:43 vs. 384:50, the incidence of open conversion was 8 (6.6%) vs. 15 (3.5%), and the incidence of ureteral injury was 2 (1.6%) vs. 0 (0%). In the T4FUN- group, the open surgery rate (<0.0001), open conversion rate (p = 0.0205) and incidence of ureteral injury (p = 0.0478) were high, with a significant difference observed between the groups.

CONCLUSION

Patients with stage T4 disease have an increased risk of ureteral injury and are more likely to be converted to open surgery. FUN can help to safely increase the laparoscopic surgery rate while safely visualizing the ureter. FUN is recommended for laparoscopic surgery in patients with stage T4 colorectal cancer.

CLINICAL TRIAL REGISTRATION

Examination of fluorescence navigation for laparoscopic colorectal cancer surgery; Research Ethics Committee of the Kawaguchi Municipal Medical Center (Saitama, Japan) approval number: 2020-3. https://kawaguchi-mmc.org/wp-content/uploads/clinical research-r02.pdf.

Real-Time Intraoperative Ureteral Identification in Minimally Invasive Colorectal Surgery: A Systematic Review

Background: Although colorectal surgery (CRS) has currently almost entirely standardized surgical procedures, it can still show pitfalls such as the intraoperative ureteral injury. Intraoperative ureteral identification (IUI) could reduce the ureteral injuries rate but evidence is still lacking. We aimed to analyze the utility and the effectiveness of real-time IUI in minimally invasive CRS. Materials and Methods: A systematic review was performed examining available data on randomized and nonrandomized studies evaluating the utility of intraureteral fluorescence dye (IFD) and lighted ureteral stent (LUS) for intraoperative identification of ureters in CRS, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) standards. Primary endpoint was ureteral injuries rate. Secondary endpoints included acute kidney injury, hematuria, urinary tract infections (UTI), and fluorescence assessment. Results: After literature search, 158 studies have been recorded, 36 studies underwent full-text reviews and 12 studies met inclusion criteria. Overall, out of a total of 822 patients who successfully received IUI, 3 (0.33%) patients experienced ureteral injury. Hematuria was reported in 689 (97.6%) of patients following LUS-guided surgery and in 1 (2%) patient following IFD-guided surgery, although transient in all cases. UTI was reported in 15 (3.3%) LUS-guided resections and in 1 (2%) IFD-guided resections. Acute kidney injury occurred in 23 (2.5%) LUS-guided surgery and 1 (1%) IFD-guided surgery. Conclusions: Real-time ureteral identification techniques could represent a valid solution in complex minimally invasive CRS, safely, with no time consuming and always reproducible by surgeons. Prospective studies will be needed to confirm these findings.

Role of near-infrared fluorescence in colorectal surgery

Near-infrared fluorescence (NIRF) is a technique of augmented reality that, when applied in the operating theatre, allows the colorectal surgeon to visualize and assess bowel vascularization, to identify lymph nodes draining a cancer site and to identify ureters. Herein, we review the literature regarding NIRF in colorectal surgery.

Fluorescence vessel and ureter navigation during laparoscopic lateral lymph node dissection

BACKGROUND

Lateral lymph node metastasis in lower rectal cancer is considered a local disease in Japan, and guidelines suggest lateral lymph node dissection (LLND). However, laparoscopic procedures are relatively difficult. The ureter and hypogastric fascia must be dissected from the vesicohypogastric fascia to preserve the autonomic nerve and ureter. Additionally, lymph node dissection around the internal iliac artery is complex because many patterns of branching from the internal iliac artery exist. We investigated the utility of fluorescence ureter and vessel navigation using a near-infrared ray fluorescent ureteral catheter (NIRFUC) and indocyanine green (ICG).

METHODS

Fourteen patients who underwent laparoscopic LLND using fluorescence navigation were included. Eleven patients had rectal cancer, 1 had anal cancer, and 2 exhibited recurrence of rectal cancer. Eleven patients underwent NIRFUC insertion before surgery. Fluorescence vessel navigation (FVN) was performed with intraoperative ICG injections in 14 patients, with a total of 18 sides. The outcome measures were ureter navigation visibility, detection of the branch form from the internal iliac artery with FVN, differences between the fluorescence findings and anatomy of the internal iliac artery determined after LLND, and the surgical outcome.

RESULTS

In all 11 patients, the ureters were clearly identified as fluorescent before dissection around the ureter. FVN revealed the internal iliac, umbilical, and superior vesical arteries in all patients. The branch from the internal iliac artery according to the Adachi classification was revealed on 16 sides (89%). The time from intravenous ICG injection to fluorescence of the internal iliac artery was 38 (17-57) s. The time from intravenous injection to when the vessels were observed as fluorescent was 113 (65-661) s. No ureteral or vessel injuries occurred.

CONCLUSIONS

Fluorescence navigation of vessels and the ureter is feasible in laparoscopic LLND and has the potential to increase safety.

CLINICAL TRIAL REGISTRATION

Examination of fluorescence navigation for laparoscopic colorectal cancer surgery Research Ethics Committee of the Kawaguchi Municipal Medical Center (Saitama, Japan) approval number: 2020-3. https://kawaguchi-mmc.org/wp-content/uploads/clinicalresearch-r02.pdf.

Ureteral injuries in colorectal surgery and the impact of laparoscopic and robotic-assisted approaches

BACKGROUND

Ureteral injury is a feared complication in colorectal surgery that has been increasing over the past decade. Some have attributed this to an increased adoption of minimally invasive surgery (MIS), but the literature is hardly conclusive. In this study we aim to further assess the overall trend of ureteral injuries in colorectal surgery, and investigate propensity adjusted contributions from open and MIS to include robotic-assisted surgery.

METHODS

This is a retrospective analysis of colorectal surgeries from 2006 to 2016 using the Nationwide Inpatient Sample (NIS) database. Multivariable logistic regression was performed to identify predisposing and protective factors. Demographics, hospital factors, and case-mix differences for open and MIS were accounted for via propensity analysis. The NIS coding structure changed in 2015, which could introduce a potential source of incongruity in complication rates over time. As a result, all statistical analyses included only the first nine years of data, or were conducted before and after the change for comparison.

RESULTS

Of 514,162 colorectal surgeries identified there were 1598 ureteral injuries (0.31%). Ureteral injuries were found to be increasing through 2015 (2.3/1000 vs 3.3/1000; p < 0.001) and through the coding transition to 2016 (4.8/1000; p < 0.001). This trend was entirely accounted for by injuries made during open surgery, with decreasing injury rates for MIS over time. Adjusted odds ratio (OR) for ureteral injury with all MIS vs. open cases was 0.81 (95% CI 0.70-0.93, p = 0.003) and for robotic-assisted surgery alone versus open cases was 0.50 (95% CI 0.33-0.77, p = 0.001).

CONCLUSIONS

The incidence rate of ureteral injuries during open colorectal surgery is increasing over time, but have been stable or decreasing for MIS cases. These findings hold even after using propensity score analysis. More research is needed to further delineate the impact of MIS and robotic-assisted surgery on ureteral injuries.

Ureteral navigation using a fluorescent ureteral catheter during laparoscopic colorectal surgery

BACKGROUND

Ureteral injury is the most common urological complication of pelvic surgery, with a reported incidence during colon resection of 0.3-1.5%. Ureteral stenting is commonly performed preoperatively to prevent ureteral injury. Because tactile sensation is not reliable during laparoscopic surgery, the effect of the ureteral stent is considered limited. Recently, fluorescence imaging has been used in laparoscopic surgery. The Near-Infrared Ray Catheter (NIRC™) fluorescent ureteral catheter (NIRFUC) is a new catheter with built-in NIR fluorescent resin. This pilot study was performed to evaluate the utility of fluorescence ureteral navigation using the NIRFUC during laparoscopic colorectal surgery.

METHODS

We evaluated the intraoperative utility of the NIRFUC and the short-term outcomes in 20 patients treated with colorectal surgery at Kawaguchi Municipal Medical Center between February and July 2020. In all, 18 patients with malignant tumors and 2 patients with benign disease, i.e., a sigmoid colovesical fistula, were included. Ten patients developed preoperative intestinal obstruction. One patient experienced preoperative perforation. Nine patients developed preoperative peritumoral abscesses. Laparoscopic surgery was performed with the VISERA ELITE2 system.

RESULTS

In all cases, the ureters were very clearly identified as fluorescent without the need for dissection. In all cases, only a moment was required to identify the ureter by fluorescence observation. In all cases, R0 resection was performed. The mean surgical duration was 334 min (161-1014), the mean blood loss was 10 ml (1-500), and the mean postoperative hospital stay was 11 days (8-47). There were no cases of ureteral injury.

CONCLUSION

The NIRFUC was very clearly identified as fluorescent in a moment during surgery without dissection around the ureter. Fluorescence ureteral navigation using the NIRFUC may make colorectal surgery easier and facilitate completion of complex minimally invasive surgery, especially during surgery in patients with invasion of the surrounding tissue or a history of pelvic surgery or radiation.

Nerve autofluorescence in near-ultraviolet light markedly enhances nerve visualization in vivo

BACKGROUND

During surgery, surgeons must accurately localize nerves to avoid injuring them. Recently, we have discovered that nerves fluoresce in near-ultraviolet light (NUV) light. The aims of the current study were to determine the extent to which nerves fluoresce more brightly than background and vascular structures in NUV light, and identify the NUV intensity at which nerves are most distinguishable from other tissues.

METHODS

We exposed sciatic nerves within the posterior thigh in five 250-300 gm Wistar rats, then observed them at four different NUV intensity levels: 20%, 35%, 50%, and 100%. Brightness of fluorescence was measured by fluorescence spectroscopy, quantified as a fluorescence score using Image-J software, and statistically compared between nerves, background, and both an artery and vein by unpaired Student's t tests with Bonferroni adjustment to accommodate multiple comparisons. Sensitivity, specificity, and accuracy were calculated for each NUV intensity.

RESULTS

At 20, 35, 50, and 100% NUV intensity, fluorescence scores for nerves versus background tissues were 117.4 versus 40.0, 225.8 versus 88.0, 250.6 versus 121.4, and 252.8 versus 169.4, respectively (all p < 0.001). Fluorescence scores plateaued at 50% NUV intensity for nerves, but continued to rise for background. At 35%, 50%, and 100% NUV intensity, a fluorescence score of 200 was 100% sensitive, specific, and accurate identifying nerves. At 100 NUV intensity, artery and vein scores were 61.8 and 60.0, both dramatically lower than for nerves (p < 0.001).

CONCLUSIONS

At all NUV intensities ≥ 35%, a fluorescence score of 200 is 100% accurate distinguishing nerves from other anatomical structures in vivo.

Intraoperative ureter identification with a novel fluorescent catheter

Iatrogenic ureteral injuries (IUI) occur in 0.5–1.3% of cases during abdominal surgery. If not recognized intraoperatively, IUI increase morbidity/mortality. A universally accepted method to prevent IUI is lacking. Near-infrared fluorescent imaging (NIRF), penetrating deeper than normal light within the tissue, might be useful, therefore ureter visualization combining NIRF with special dyes (i.e. IRDye 800BK) is promising. Aim of this work is to evaluate the detection of ureters using stents coated with a novel biocompatible fluorescent material (NICE: near-infrared coating of equipment), during laparoscopy. female pigs underwent placement of NICE-coated stents (NS). NIRF was performed, and fluorescence intensity (FI) was computed. Successively, 0.15 mg/kg of IRDye 800BK was administered intravenously, and FI was computed at different timepoints. Ureter visualization using NS only was further assessed in a human cadaver. Both methods allowed in vivo ureter visualization, with equal FI. However, NS were constantly visible whereas IRDye 800BK allowed visualization exclusively during the ureteral peristaltic phases. In the human cadaver, NS provided excellent ureter visualization in its natural anatomical position. NS provided continuous ureteral visualization with similar FI as the IRDye 800BK, which exclusively allowed intermittent visualization, dependent on ureteral peristalsis. NS might prove useful to visualize ureters intraoperatively, potentially preventing IUI.

Iatrogenic ureteral injury during retroperitoneal laparoscopy for large renal cysts: What we learned and a review of the literature

PURPOSE

To avoid Iatrogenic ureteral injury during retroperitoneal laparoscopy for large renal cyst (diameter > 70 mm), we present two cases of iatrogenic ureteral injury and discuss their clinical courses and final outcomes.

PATIENTS AND METHODS

Two male patients (47 years old and 74 years old) with large left simple renal cysts underwent a retroperitoneal laparoscopic operation to treat the cysts. In the first patient, the left proximal ureter was partially transected (Grade 3) during the operation. The injury was identified intraoperatively. The transection was managed with a primary ureteroureterostomy (end to end) along with a double J ureteral stent. In the second patient, the left proximalureter was partially transected (Grade 4). However, the injury was unrecognized postoperatively for two days. After recognition of the complication, the injury was managed with an early primary ureteroureterostomy, which followed a failed attempt to place ureteral stent endoscopically.

RESULTS

In the first patient, a postoperative urinary leakage developed and lasted for 13 days. During long term follow-up of the first patient after the urine leak resolved, there were no reports of pain in the lumbar region or other discomfort. No recurrence of the renal cyst occurred, which was confirmed with an ultrasound at one year postoperatively. In the second patient a ureteral fistula and severe perirenal infection occurred and lasted for 86 days. The patient ultimately underwent a left nephrectomy after conservative management for this surgical complication failed. This patient developed a chronic wound infection that lasted for 3.14 months following the nephrectomy. During follow-up post nephrectomy, the patient developed stage 3B moderate chronic kidney disease (CKD) (GFR = 30 -44 ml/min).

CONCLUSIONS

For single large (diameter > 70 mm) renal cysts located at the lower pole of the kidney, it is recommended to not completely dissect out and mobilize the entire renal cyst for cyst decortication in order to avoid injuring the ureter. Iatrogenic ureteral injury increases the risk of readmission and serious life-threatening complications. The immediate diagnosis and proper management ureteric injury can reduce complications and long term sequalae.

Methylene Blue-Current Knowledge, Fluorescent Properties, and Its Future Use

Methylene blue is a fluorescent dye discovered in 1876 and has since been used in different scientific fields. Only recently has methylene blue been used for intraoperative fluorescent imaging. Here, the authors review the emerging role of methylene blue, not only as a dye used in clinical practice, but also as a fluorophore in a surgical setting. We discuss the promising potential of methylene blue together with the challenges and limitations among specific surgical techniques. A literature review of PubMed and Medline was conducted based on the historical, current and future usage of methylene blue within the field of medicine. We reviewed not only the current usage of methylene blue, but we also tried to grasp its' function as a fluorophore in five main domains. These domains include the near-infrared imaging visualization of ureters, parathyroid gland identification, pancreatic tumors imaging, detection of breast cancer tumor margins, as well as breast cancer sentinel node biopsy. Methylene blue is used in countless clinical procedures with a relatively low risk for patients. Usage of its fluorescent properties is still at an early stage and more pre-clinical, as well as clinical research, must be performed to fully understand its potentials and limitations.

A Near-Infrared Fluorescent Probe Coated with β-Cyclodextrin Molecules for Real-Time Imaging-Guided Intraoperative Ureteral Identification and Diagnosis

Although iatrogenic ureteral injury and its lack of recognition due to ureteral invisibility are serious incidents in open and laparoscopic abdominal surgeries, there are currently no safe and effective methods for intraoperative ureteral identification (IUI) and diagnosis (IUD). In this study, I designed and chemically synthesized a near-infrared fluorescence (NIRF) imaging probe (CD-NIR-1) and evaluated its clearance and ability for IUI and IUD in animal models. CD-NIR-1 demonstrated high specificity and ultrarapid clearance by rat kidneys to the urinary bladder following intravenous administration of a single dose (25 nmol/kg of body weight), with 96% of the dose ultimately excreted at the first urination with no chemical modification. Furthermore, urine containing CD-NIR-1 in ureters showed strong NIRF, thereby enabling IUI and IUD via NIRF imaging. These results demonstrated the efficacy of CD-NIR-1 for clinical use.

Prophylactic ureteral catheter placement for minimally invasive colorectal surgery

Ureteral catheter placement for identification of ureters during colorectal surgery has been a controversial subject with ill-defined indications. We present a case of ureteral catheter placement wherein the patient required readmission for renal failure with intervention under local anesthesia. This case highlights the importance of patient selection for catheter placement and clinical follow-up, as well as the need for prospective studies to determine the risk-benefit ratio of preoperative catheters.

Routine prophylactic ureteral stenting before cytoreductive surgery and hyperthermic intraperitoneal chemotherapy: Safety and usefulness from a single-center experience

OBJECTIVE

There are very few evidences about safety and usefulness of routine prophylactic ureteral stenting (PUS) before cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC).

MATERIAL AND METHODS

An analysis of prospectively collected data about patients who underwent CRS and HIPEC for different sites of primary disease was carried out focusing on ureteral complications.

RESULTS

A total of 138 patients who underwent CRS and HIPEC between December 2010 and June 2017 were considered. All patients underwent PUS before CRS and HIPEC. Of them, 91 (66.4%) patients received pelvic peritonectomy, 49 (35.8%) pelvic lymphadenectomy, 31 (22.6%) left hemicolectomy, 44 (32.4%) right hemicolectomy, 46 (33.6%) rectal resection, 56 (40.9%) hysteroannessiectomy, and 39 (28.5%) appendectomy. There was one (0.7%) postoperative ureteral fistula. The cumulative risk of ureteral stent-related major complications was 4.3% (two patients (1.4%) had protracted gross hematuria, two patients (1.4%) had urinary sepsis, and three patients (2.9%) developed hydronephrosis after a period from removing ureteral stents and required restenting. Morbidity due to ureteral stenting was associated with a longer length of stay (LOS) (p=0.053). A total of 52 patients (44.1%) developed renal dysfunction according to the RIFLE (Risk, Injury, Failure, Loss of kidney function, End-stage kidney-disease) criteria: 19.5% were in risk class, 10.2% in acute renal injury class, and 14.4% in acute renal failure class.

CONCLUSION

PUS could be a useful tool for reducing iatrogenic ureteral injury, but it is associated with a non-negligible morbidity, which implies longer LOS. A more accurate patient selection for PUS is necessary.

Currently available and experimental dyes for intraoperative near-infrared fluorescence imaging of the ureters: a systematic review

Background

Iatrogenic ureteral injury (IUI) following abdominal surgery has a relatively low incidence, but is associated with high risks of morbidity and mortality. Conventional assessment of IUI includes visual inspection and palpation. This is especially challenging during laparoscopic procedures and has translated into an increased risk of IUI. The use of near-infrared fluorescent (NIRF) imaging is currently being considered as a novel method to identify the ureters intraoperatively. The aim of this review is to describe the currently available and experimental dyes for ureter visualization and to evaluate their feasibility of using them and their effectiveness.

Methods

This article adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standard for systematic reviews. A systematic literature search was performed in the PubMed database. All included articles were screened for eligibility by two authors. Three clinical trial databases were consulted to identify ongoing or completed unpublished trials. Risk of bias was assessed for all articles.

Results

The search yielded 20 articles on ureter visualization. Two clinically available dyes, indocyanine green (ICG) and methylene blue (MB), and eight experimental dyes were described and assessed for their feasibility to identify the ureter. Two ongoing clinical trials on CW800-BK and one trial on ZW800-1 for ureter visualization were identified.

Conclusions

Currently available dyes, ICG and MB, are safe, but suboptimal for ureter visualization based on the route of administration and optical properties, respectively. Currently, MB has potential to be routinely used for ureter visualization in most patients, but (cRGD-)ZW800-1 holds potential for this role in the future, owing to its exclusive renal clearance and the near absence of background. To assess the benefit of NIRF imaging for reducing the incidence of IUI, larger patient cohorts need to be examined.

Electronic supplementary material

The online version of this article (10.1007/s10151-019-01973-4) contains supplementary material, which is available to authorized users.

Near-infrared fluorescence laparoscopy of the ureter with three preclinical dyes in a pig model

Background

Ureteric injury is reported to occur in 1–7.6% of colorectal surgeries. To reduce the incidence of ureteral injury, it is essential to identify the ureters. The use of near-infrared fluorescence (NIRF) imaging with intravenously administered dyes might be of added value for ureteral visualization during laparoscopy. The aim of this study is to assess the performance of three preclinical dyes; IRDye^® 800BK, IRDye^® 800NOS and IRDye^® 800CW, for near-infrared fluorescence laparoscopy of the ureter in pigs.

Methods

In three female Dutch landrace pigs, the new dyes were evaluated. In each pig, 1 dye was tested using a 6-mg intravenous dose in a concentration of 1 mg/ml. Imaging was performed in fluorescence mode and white light mode with a laparoscopic imaging system. In order to further evaluate the dyes, an ex vivo imaging experiment was performed, in which 8 decreasing concentrations per dye, diluted in PBS, were evaluated in a transparent test tube with NIRF mode at a distance of 1, 5 and 10 cm from the laparoscope.

Results

All three dyes were effective in allowing the identification of the ureter with NIRF imaging. The ureter became fluorescent after 35, 45 and 10 min, respectively, for IRDye^® 800BK, IRDye^® 800NOS and IRDye^® 800CW with a maximum target-to-background ratio (TBR) of 2.14, 0.66 and 1.44, respectively. In the ex vivo imaging experiment, all three dyes produced a strong fluorescence signal at all concentrations and all distances evaluated.

Conclusions

Intravenous administration of the preclinical dyes IRDye^® 800CW, IRDye^® 800 BK and IRDye^® 800NOS facilitated successful identification of the anatomical course of the ureter in living pig models. The highest measured TBR occurred with the use of IRDye^® 800BK. Ex vivo, a correlation was observed between the fluorescence intensities of the signal with the concentration of the dye and with the distance to the object.

Methylene blue fluorescence of the ureter during colorectal surgery

Background

Iatrogenic ureteric injury is a serious complication of colorectal surgery. Incidence is estimated to be between 0.3 and 1.5%. Of all ureteric injuries, 9% occur during colorectal procedures. Ureteric stents are utilised as a method to reduce the risk of injury; however, these are not without risk and do not guarantee prevention of injury. Fluorescence is a safe and effective alternative for intraoperative ureteric localisation. This proof of principle study aims to assess the use of methylene blue to fluoresce the ureter during colorectal surgery.

Method

Patients undergoing elective colorectal surgery were included in this open label, non-randomised study. Methylene blue was administered intravenously at varying doses (0.25–1 mg/kg) over 5 min, 10–15 min prior to entering ‘ureteric territory.’ Fluorescence was assessed using the PINPOINT Deep Red laparoscopic system at fixed time points by the surgeon and an independent observer.

Results

42 patients received methylene blue; 2 patients were excluded from analysis. Of the 69 ureters assessed, 64 were seen under fluorescence. Of these, 14 were not visible under white light. 50 ureters were observed with both fluorescence and white light with 14 of these being seen earlier with fluorescence. In ten cases, fluorescence revealed the ureter to be in a different location than suspected.

Conclusion

Fluorescence is a promising method to allow visualisation of the ureter, where it is not identified easily under standard operative conditions, thereby improving safety and reducing operative time and difficulty.

Electronic supplementary material

The online version of this article (10.1007/s00464-018-6219-8) contains supplementary material, which is available to authorized users.

Ureteral stents increase risk of postoperative acute kidney injury following colorectal surgery

BACKGROUND

Ureteral stents are commonly placed before colorectal resection to assist in identification of ureters and prevent injury. Acute kidney injury (AKI) is a common cause of morbidity and increased cost following colorectal surgery. Although previously associated with reflex anuria, prophylactic stents have not been found to increase AKI. We sought to determine the impact of ureteral stents on the incidence of AKI following colorectal surgery.

METHODS

All patients undergoing colon or rectal resection at a single institution between 2005 and 2015 were reviewed using American College of Surgeons National Surgical Quality Improvement Program dataset. AKI was defined as a rise in serum creatinine to ≥ 1.5 times the preoperative value. Univariate and multivariate regression analyses were performed to identify independent predictors of AKI.

RESULTS

2910 patients underwent colorectal resection. Prophylactic ureteral stents were placed in 129 patients (4.6%). Postoperative AKI occurred in 335 (11.5%) patients during their hospitalization. The stent group demonstrated increased AKI incidence (32.6% vs. 10.5%; p < 0.0001) with bilateral having a higher rate than unilateral stents. Hospital costs were higher in the stent group ($23,629 vs. $16,091; p < 0.0001), and patients with bilateral stents had the highest costs. Multivariable logistic regression identified predictors of AKI after colorectal surgery including age, procedure duration, and ureteral stent placement.

CONCLUSIONS

Prophylactic ureteral stents independently increased AKI risk when placed prior to colorectal surgery. These data demonstrate increased morbidity and hospital costs related to usage of stents in colorectal surgery, indicating that placement should be limited to patients with highest potential benefit.

Biodegradation behavior of magnesium and ZK60 alloy in artificial urine and rat models

In this work, the biodegradable and histocompatibility properties of pure Mg and ZK60 alloy were investigated as new temporary implants for urinary applications. The corrosion mechanism in artificial urine was proposed using electrochemical impedance spectroscopy and potentiodynamic polarization tests. The corrosion potential of pure magnesium and ZK60 alloy were −1820 and −1561 mV, respectively, and the corrosion current densities were 59.66 ± 6.41 and 41.94 ± 0.53 μA cm⁻², respectively. The in vitro degradation rates for pure Mg and ZK60 alloy in artificial urine were 0.382 and 1.023 mm/y, respectively, determined from immersion tests. The ZK60 alloy degraded faster than the pure Mg in both artificial urine and in rat bladders (the implants of both samples are ø 3 mm × 5 mm). Histocompatibility evaluations showed good histocompatibility for the pure Mg and ZK60 alloy during the 3 weeks post-implantation in rat bladders, and no harm was observed in the bladder, liver and kidney tissues. The results provide key information on the degradation properties and corrosion mechanism of pure Mg and ZK60 alloy in the urinary system.

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ZK60 obtained loose corrosion product layer with poor corrosion resistance in AU.

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ZK60 showed a faster degradation rate than Mg in artificial urine and bladder of rat.

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Mg and ZK60 alloy showed good histocompatibility for the bladder model of rat.