Associations of intestinal diseases with anal diseases: a Mendelian randomization study

Abstract Although observational clinical studies have established an association between Intestinal Diseases (IDS) and Anal Diseases (ADS), the causal relationship is still not fully understood due to the limitations of observational studies. Genome-wide association study (GWAS) statistical data for IDS and ADS were obtained from publicly available databases. To assess the causal effects of IDS on ADS, we conducted Mendelian randomization analysis. The inverse variance weighted method indicated that Inflammatory bowel disease (IBD) had a significant causal relationship with three kinds of ADS: Anorectal abscess (ARB), Haemorrhoidal disease (HEM), and Fissure and fistula of anal and rectal regions (FISSANAL). Crohn’s disease (CD) and Ulcerative colitis (UC) also showed significant causal effects with three ADS: ARB, HEM, and FISSANAL. Furthermore, a potential link between CD and BNA(Benign neoplasm of anus and anal canal), Irritable bowel syndrome (IBS) and HEM, Colorectal cancer (CRC) and BNA, and Celiac disease and MNA (Malignant neoplasm of anus and anal canal) was observed. This comprehensive MR analysis highlight the significant and increased risk of common Anal Diseases (ARB, FISSANAL, and HEM) in patients with IBD, CD, and UC. Additionally, potential positive causal associations emerged between IBS and HEM, CRC and BNA, as well as between celiac disease and MNA.