Scrotal Surgery After Laparoscopic Donor Nephrectomy

Overview

This study will examine whether laparoscopic nephrectomy is associated with a higher long-term risk of receiving scrotal surgery in male living kidney donors compared to male nondonors from the general population who have similar baseline health indicators. Both groups will be followed for many years.

\* Summary \* Background: It is underappreciated that some men who donate a kidney later experience unilateral scrotal pain and swelling on the same side of their nephrectomy. The condition can be assessed with an ultrasound, and some men undergo surgery for severe discomfort. Methods: Using large provincial healthcare databases, the investigators will conduct a retrospective cohort study of approximately 800 male kidney donors who will be matched in a 1:10 ratio with 8000 male nondonors of similar baseline health from the general population. Laparoscopic nephrectomies will have occurred between 2002 and 2023 in the province of Ontario, Canada, with follow-up through linked healthcare databases until March 2024. Donors and nondonors will be matched for age, date of cohort entry, residency (urban or rural), income (average neighbourhood income categorized into fifths), a history of vasectomy, and a history of inguinal hernia repair. The primary outcome will be a hospital admission with receipt of surgery to address a unilateral scrotal fluid collection, typically involving hydrocele excision. The secondary outcome will be receipt of a scrotal ultrasound. Study outcome: The study will determine if laparoscopic nephrectomy is associated with a higher long-term risk of receiving scrotal surgery or a scrotal ultrasound in male living kidney donors compared to male nondonors with similar indicators of baseline health. \* Literature Review \* Over the last decade the investigators have become aware of reports suggesting that some male donors experience unilateral testicular pain and scrotal swelling after donation on the same side of their nephrectomy. Upon review, the investigators identified over 10 studies that have described this outcome. The proportion of affected male donors ranged from 2% to 55%. No study included a comparison group of nondonors, and most studies only followed donors for a short period after nephrectomy. Some studies reported that testicular pain was more common after laparoscopic than open surgery. The pain was described as dull, aching, and heavy in nature, starting in the week following nephrectomy. Some studies, but not others, report that testicular pain was more common after a left-sided versus right-sided nephrectomy, where, due to anatomy, the gonadal vein is divided in a left nephrectomy but may be spared in a right nephrectomy. There are several treatment options for testicular pain, including reports of some men undergoing scrotal surgery to address a hydrocele on the same side as their donated kidney. \* Research location \* The study will be conducted at ICES (ices.on.ca), an independent, non-profit research institute whose legal status under Ontario's health information privacy law allows it to collect and analyze health care and demographic data without consent for health system evaluation and improvement. The use of data in this project is authorized under section 45 of Ontario's Personal Health Information Protection Act, which does not require review by a Research Ethics Board. Information will be obtained from several linked databases in Ontario such as, the Trillium Gift of Life Network, Ontario's Registered Persons Database, and the Ontario Health Insurance Plan, and from the Canadian Institute for Health Information the Discharge Abstract Database, National Ambulatory Care Reporting System and Same Day Surgery. In Ontario, the Canadian Classification of Health Interventions system to record procedures in healthcare databases was adopted on April 1, 2002, and this date will serve as the start of the accrual period. The investigators expect the data to be complete for virtually all variables to be used in this study. This is a retrospective cohort study for which all study data is already available in administrative healthcare databases at ICES. As a recommended research practice, the investigators are publicly documenting the study description, design and statistical analysis plan on clinicaltrials.gov. before analyzing the study outcomes. \* Statistical analysis plan \* Baseline characteristics: Continuous variables will be presented as mean (standard deviation) or median (interquartile range \[IQR\]), as appropriate, and categorical variables as frequency (percentage). Due to the large expected cohort size and the influence of sample size on statistical testing, the characteristics of donors and nondonors at the time of cohort entry will be compared prior to and after matching using standardized mean differences, where a value \>0.10 is considered meaningfully different. Characteristics specific to the donors will also be reported (e.g., pre-nephrectomy kidney function, their relationship to the recipient, the number of years the surgeon who performed their nephrectomy was in practice). Period of observation: After cohort entry, a person's follow-up time will be censored at the time of developing the relevant study outcome (i.e., time to first event), death, emigration from the province, or the end of the study's observation period (March 31, 2024). Assessing risk of the primary and secondary outcome: The association between laparoscopic donor nephrectomy and a hospital admission with scrotal surgery will be assessed using hazard ratios and their 95% confidence intervals, estimated using Cox proportional hazards regression with robust variance estimation accounting for the correlation within matched sets. The proportional hazards assumption will be assessed using the Kolmogorov-type supremum test on 1000 simulated patterns. If the assumption is violated, instead of a hazard ratio, a stratified log-rank test will be used to test significance of the outcome and the difference of restricted mean survival time at 20 years with its 95% confidence interval will be presented. Main additional analyses: (i) The investigators will perform the primary outcome analysis restricting the code set only to hydrocele repair. (ii) The primary focus is to better understand the outcomes following laparoscopic donor nephrectomy, which currently is the preferred method for this procedure. However, over 250 open nephrectomies were also performed in Ontario during the study period. Some studies suggest that scrotal symptoms may be more common after laparoscopic procedures compared to open ones, while other studies do not support this claim. To investigate this, the investigators will add a group of donors who underwent open procedures during the study period, assembled in a similar fashion to those who had laparoscopic procedures. The investigators will employ inverse probability of treatment weighting based on propensity scores to balance the baseline characteristics of the donors who had nephrectomies via laparoscopic procedures (one group) and open procedures (the other group). Donors who had open procedures will be weighted using the average treatment effect in the treated weights, defined as propensity score divided by (1 - propensity score). Donors who received laparoscopic procedures will have a weight of 1. This approach is expected to generate a weighted pseudo-sample of donors who underwent open procedures, with a distribution of measured baseline characteristics resembling that of donors who had laparoscopic procedures. The investigators will account for the weighting in all comparative analyses, with hazard ratios estimated using Cox proportional hazards regression and 95% confidence intervals created using a variance estimate obtained from bootstrapping. The primary outcome will be receipt of scrotal surgery, while the secondary outcome will be receipt of a scrotal ultrasound. (iii) If the investigators can reliably ascertain the side of nephrectomy in the data sources, they will compare the outcomes of left vs. right nephrectomy amongst those who received a laparoscopic nephrectomy. This will be done in the same manner as for open vs. laparoscopic nephrectomy. Some studies, but not others, report that scrotal symptoms are more common after a left-sided versus right-sided nephrectomy, where, due to anatomy, the gonadal vein is divided in a left nephrectomy but may be spared in a right nephrectomy. Other additional analyses (iv) The investigators will conduct the primary and secondary outcome analysis for other prespecified subgroups of men according to age, income, year of cohort entry, and a history of vasectomy prior to cohort entry (yes or no), and if the number of events allow for meaningful analysis, rural residence and a prior history of inguinal hernia repair. The investigators expect no significant difference in the hazard ratio between these subgroups. Rather, they will be examined for general consistency of any donation-attributable observed effect across subgroups. (v) The investigators will analyze the characteristics associated with the primary and secondary outcomes separately for donors and nondonors using Cox proportional hazards regression. The characteristics under consideration and assessed at cohort entry include age, income, rural residence, year of cohort entry, a prior history of vasectomy, and a prior history of inguinal hernia repair. In nondonors, an older (vs. younger) age at cohort entry may associate with a higher risk of developing the outcomes in follow-up, whereas this association may not hold true for donors. Rather, in donors, outcomes caused by nephrectomy may be minimally associated with age at cohort entry. Descriptive analyses and graphs (i) Outcomes will be described as incidence rates per 1000 person-years, and as the cumulative incidence during follow-up (obtained using the Aalen-Johansen estimator, treating death as a competing event, with donors and nondonors compared visually with graphical curves and at landmark timepoints). (ii) Characteristics of the primary outcome amongst donors will be described, such as when the scrotal surgeries were performed after nephrectomy, whether they were done under general anesthesia, whether they required a hospital overnight stay, and whether they were performed by a different surgeon than the one who performed their nephrectomy. Similarly, the investigators will examine the characteristics of the secondary outcome amongst donors, such as the type of physician who ordered the scrotal ultrasound and when it was performed after nephrectomy. P values (significance testing) and confidence intervals: The investigators will perform hierarchical statistical tests to assess their hypotheses in the pre-defined order described below. The 2-sided significance level will be 0.05 for each tested hypothesis. After a non-significant test no further significance testing will be performed and no further P values will be reported. All estimates (with and without P values) will be reported as point estimates with 95% confidence intervals. The investigators acknowledge the interval widths of the estimates without P values are not adjusted for multiple testing and that those inferences may not be reproducible. The order: (i) the primary outcome (scrotal surgery) in donors vs. nondonors (ii) the secondary outcome (scrotal ultrasound) in donors vs. nondonors (iii) hydrocele surgery (codes within the primary outcome) in donors vs. nondonors (iv) primary outcome in donors who underwent a laparoscopic vs. open procedure (v) secondary outcome in donors who underwent a laparoscopic vs. open procedure (vi) \[if data on laterality is available\] primary outcome in donors who underwent a left vs. right laparoscopic nephrectomy (vii) \[if data on laterality is available\] secondary outcome in donors who underwent a left vs. right laparoscopic nephrectomy Statistical power: The investigators are restricted to using information available in the datasets and have not performed power calculations to determine the sample size needed to detect a given effect with adequate statistical power. Instead, they will present 95% confidence intervals with point estimates to suggest the range in which the true parameter may fall. There are now over 10 studies describing testicular pain and/or scrotal swelling in donors, with a range of 2% to 55% of donors effected. This study will produce the first population-based estimates of donation-attributable absolute and relative risks with 95% confidence intervals of this potentially important complication.

Conditions

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Outcomes