Inguinal hernia combined with colorectal cancer: 8 cases report and Mendelian Randomization

Abstract

Background  The colorectal cancer (CRC) and inguinal hernia association has been long debated. Here, we describe eight cases of patients with inguinal hernia simultaneously combined with CRC. We applied Mendelian randomization (MR) analysis to estimate the bidirectional causal relations between CRC and inguinal hernia.Methods  Data of the clinical manifestations, diagnosis, and treatments of eight patients with inguinal hernia combined with CRC, six of whom were incarcerated, from January 2012 to December 2022, have been collected. Two-sample Mendelian randomization was conducted. Fifty-three colorectal cancer-associated single-nucleotide polymorphisms (SNPs) and 38 inguinal hernia-associated SNPs were used as genetic instrument variables (IV), derived from publicly available genome-wide association studies (GWAS) summary meta-analysis. The primary estimation was based on the inverse-variance weighted approach (IVW); the MR-Steiger method was used to detect the reverse effect.  MR Pleiotropy RESidual Sum and Outlier, MR-Egger, and weighted median methods were utilized for heterogeneity and pleiotropy evaluation.Results  Surgery was performed in all eight cases. Postoperative pathology confirmed the combination of inguinal hernia and colorectal cancer in all patients Eventually, seven of them were cured, whereas one died; Mendelian randomization showed no evidence of bidirectional causal effect between CRC and inguinal hernia. Inguinal hernia did not cause CRC (OR = 0.999 (0.992,1.006), P = 0.802, OR = 1.039 (0.998, 1.081), P = 0.409), neither did inguinal hernia could induce CRC (OR = 1.015 (0.909, 1.134), P = 0.784, OR = 1.039 (0.985, 1.233), P = 0.097), colon cancer (OR = 0.999 (0.877, 1.140), P = 0.999, OR = 1.001 (0.999, 1.004), P = 0.137), or rectal sigmoid junction cancer (OR = 1.001 (0.999, 1.001), P = 0.343). The sensitivity analysis showed no pleiotropy or heterogeneity among SNPs.  Conclusions  MR study found no bidirectional association between CRC and inguinal hernia. More treatment suggestions should be concluded by collecting a large number of cases.