Nephrology · Medical Literature
Male reproductive surgeries and long-term kidney outcomes: a Mendelian randomization and meta-analysis of UK Biobank and FinnGen.
Abstract
The long-term renal implications of conditions leading to male reproductive surgeries remain unclear. This study evaluated the potential causal relationships between genetic liability to undergoing these surgeries and kidney diseases. Genetic variants associated with four surgery-related phenotypes-testicular hydrocele surgery, testicular or scrotal surgery, circumcision, and vasectomy-were selected as instrumental variables. Mendelian randomization, meta-analysis, and exploratory mediation analyses were used to assess associations with 20 kidney outcomes. Results showed genetic liability to testicular hydrocele surgery was associated with higher odds of chronic kidney disease, IgA nephropathy, glomerulonephritis, cystic kidney disease, tubulo-interstitial nephritis, and kidney injury, and with lower odds of benign kidney tumors and renal stones. Genetic liability to testicular or scrotal surgery was associated with increased odds of renal colic, gout, malformations of the renal pelvis or ureters, renal stones, and kidney infections. Genetic liability to circumcision was associated with higher odds of congenital obstructive malformations, hypertensive heart/renal disease, malignant kidney neoplasms, and increased kidney volume, and with lower odds of kidney cysts, benign tumors, and chronic renal failure. Genetic liability to vasectomy was linked to reduced odds of pyelonephritis and malignant kidney neoplasms. Mediation analyses suggested partial contributions of immune and metabolic traits. This study provides evidence that genetic liability to undergoing male reproductive system surgeries-reflecting the underlying biological or pathological indications-is associated with distinct patterns of kidney disease susceptibility. Findings suggest that individuals with underlying conditions predisposing them to testicular hydrocele or scrotal surgery may benefit from attention to long-term kidney health.
Clinical relevance
Do genetic liabilities to undergoing male reproductive surgeries (testicular hydrocele surgery, testicular or scrotal surgery, circumcision, and vasectomy) have causal associations with long-term kidney disease outcomes? __SNAPSHOT__ {"studyDesign":"Two-sample Mendelian randomization (MR) with meta-analysis across two independent GWAS cohorts (UK Biobank and FinnGen), supplemented by exploratory mediation analyses","setting":"Population-level genome-wide association study (GWAS) data from UK Biobank (United Kingdom) and FinnGen (Finland); no single clinical site","sampleSize":"not reported in abstract; derived from UK Biobank and FinnGen summary-level GWAS data","population":"Males with genetic liability to four surgery-related phenotypes: testicular hydrocele surgery, testicular or scrotal surgery, circumcision, and vasectomy; ancestry not explicitly stated in abstract but UK Biobank and FinnGen are predominantly European-ancestry cohorts","intervention":"Genetic liability to each of four male reproductive surgery phenotypes, operationalized as GWAS-derived single-nucleotide polymorphisms (SNPs) used as instrumental variables (IVs) in a Mendelian randomization framework","comparator":"Genetic liability serving as the reference (no-surgery or low-liability reference group implied by MR design); no conventional active comparator arm","primaryOutcome":"Associations between genetic liability to each surgery phenotype and 20 kidney disease outcomes; specific primary endpoint hierarchy not stated in abstract","followUp":"not reported; cross-sectional GWAS summary data used — longitudinal follow-up not applicable in standard two-sample MR design","fundingSource":"not reported"}
Key findings
The study reports directional MR associations — expressed as odds ratios — between genetic liability to each of four male reproductive surgery phenotypes and multiple kidney outcomes across 20 tested endpoints. Specific odds ratios, 95% confidence intervals, and p-values are not provided in the available abstract and must be considered not reported at this level of evidence review. Key directional findings by surgery phenotype: 1. Testicular hydrocele surgery: Associated with increased odds of chronic kidney disease (CKD), IgA nephropathy, glomerulonephritis, cystic kidney disease, tubulointerstitial nephritis, and acute kidney injury; associated with decreased odds of benign kidney tumors and renal stones. 2. Testicular or scrotal surgery: Associated with increased odds of renal colic, gout, malformations of the renal pelvis or ureters, renal stones, and kidney infections. 3. Circumcision: Associated with increased odds of congenital obstructive malformations, hypertensive heart/renal disease, and malignant kidney tumors (abstract truncated; full results not reported here). 4. Vasectomy: Results not included in the provided abstract excerpt. No NNT or NNH can be calculated from the available abstract. No absolute risk differences are reported. Adverse event data are not applicable in this MR design. All effect estimates are for genetic liability (instrument-based), not for the surgical procedures per se.
Practice implications
This study uses Mendelian randomization to investigate whether genetic predisposition to conditions requiring male reproductive surgery is causally linked to kidney disease. The central interpretive concept is critical: in MR, the IVs reflect genetic liability to the underlying conditions necessitating surgery (e.g., hydrocele, conditions requiring scrotal surgery, anatomical variants associated with circumcision, or conditions leading to vasectomy), NOT the surgeries themselves as direct interventions. Therefore, the findings cannot establish that any surgical procedure causes or prevents kidney disease. What the study established: Genetic liability to phenotypes associated with testicular hydrocele surgery, testicular/scrotal surgery, and circumcision appear to associate with differing patterns of kidney disease risk, suggesting shared genetic or pathophysiological pathways between urogenital development and renal outcomes. What the study did NOT establish: (1) Causal harm or benefit of the surgical procedures themselves; (2) mechanistic pathways (mediation analyses are described as 'exploratory'); (3) generalizability beyond predominantly European-ancestry populations; (4) clinical thresholds or actionable screening criteria; (5) statistical parameters for the full set of 20 outcomes tested. Patients not well-represented: Women, pediatric populations, non-European ancestries, and individuals undergoing surgery for indications differing from those in UK Biobank/FinnGen phenotype definitions. Clinical importance: The directional diversity of associations across surgery phenotypes suggests biologically distinct pathways rather than a uniform urogenital-renal connection. However, without full quantitative results, clinical magnitude cannot be assessed. IMPORTANT LIMITATION OF THIS SUMMARY: Only the abstract — and a truncated abstract — was available for review. Specific effect sizes, confidence intervals, p-values, sensitivity analyses (MR-Egger, weighted median, MR-PRESSO), F-statistics, and mediation results are not reported here and are essential to full critical appraisal. __LIMITATIONS__ 1. Truncated abstract: Full quantitative results, sensitivity analyses, and mediation data were not available for this summary, precluding complete critical appraisal. 2. MR design constraints: Causal inference requires three core IV assumptions (relevance, independence, exclusion restriction); pleiotropy — particularly for surgery-related phenotypes that may share genetic architecture with anatomical, developmental, and hormonal traits — is a substantial concern. 3. Phenotype proxies: 'Genetic liability to surgery' is a proxy for the underlying condition requiring surgery; the IV may capture diverse biological signals not specific to a single pathological entity. 4. Multiple testing: With 4 exposures × 20 outcomes = 80 tested associations, Bonferroni or FDR correction thresholds and the number of associations surviving correction are not reported in the abstract. 5. Exploratory mediation: Authors themselves label mediation analyses as 'exploratory,' meaning mediating mechanisms remain speculative. 6. Population restriction: UK Biobank and FinnGen are predominantly European-ancestry; findings may not generalize to other ancestries. 7. Sample overlap: Potential overlap between UK Biobank and FinnGen summary statistics, if not adequately addressed, can bias MR estimates. 8. Sex specificity: Male-only phenotypes analyzed in predominantly mixed-sex GWAS databases may introduce misclassification noise. 9. No clinical covariate adjustment: Standard two-sample MR cannot adjust for individual-level confounders (e.g., comorbidities, BMI, smoking) that may influence both surgical indication and kidney outcome. 10. No follow-up or temporality: Cross-sectional GWAS design cannot establish the timing of kidney disease onset relative to surgical indication. __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This Mendelian randomization study identifies associations between genetic liability to conditions requiring male reproductive surgeries and diverse patterns of kidney disease, suggesting shared urogenital-renal genetic pathways. However, the findings reflect genetic predisposition to the underlying surgical indications — not the procedures themselves — and cannot support changes to surgical practice or renal surveillance protocols in their current form. Replication with full quantitative reporting, rigorous pleiotropy testing, and non-European ancestry cohorts is needed before these findings can inform clinical decision-making.