eP748 - Can Assessment of the Geographic Distribution of External Hemorrhoid Thromboses Provide Insights into Their Pathogenesis?

Purpose/Background: Thrombosed external hemorrhoids are one of the most frequent conditions requiring urgent colorectal evaluation. Their pathogenesis remains controversial; the most widely accepted theory is elevated intravenous pressure in the hemorrhoidal plexus leads to rupture of the endothelial lining initiating thrombosis. Since there are three main hemorrhoidal plexi, two of which are situated on the right side of the anus, one would naturally expect more external hemorrhoidal thromboses on the right side of the anus versus the left side. Despite their high incidence, little is known regarding the geographic distribution of external hemorrhoid thromboses. In this study, we aimed to assess the distribution of external hemorrhoid thromboses.Methods/Interventions: A retrospective chart review was performed on patients with an external thrombosed hemorrhoid assessed in the office of the senior author over the 18-month period ending July 2023. Geographic position of thromboses around the anal canal was categorized into 8 equal octants: anterior midline (AML), left anterior (LA), left lateral (LL), left posterior (LP), posterior midline (PML), right posterior (RP), right lateral (RL) and right anterior (RA). Differences in geographic position of thromboses were assessed using Chi-square analysis. An even distribution of the thrombosis was assumed in the distribution analysis.Results/Outcomes: The study cohort of 165 patients included 104 (63%) males and 61 females (37%) (p=0.02). Median age of the patient group was 51 (range, 17-73) years. The expected circumferential distribution of the 165 thromboses was 21 in each octant. The observed distribution was unequal: AML (n=3;2%), LA (n=13;8%); LL (n=46; 28%), LP (n=34;21%), PML (n=0), RP (n=27;16%), RL (n=32;19%) and RA (n=10;6%) (Figure). The number of thromboses in midline positions was significantly lower than expected (AML, p=0.0003; PML, p=0.0001). However, the number of thromboses in the LL and LP positions was significantly higher than expected (LL, p=0.0005; LP, p=0.03). There was no significant difference in expected thromboses in any right sided position (RA, p=0.09; RL p=0.09; RP p=0.35). There were no significant differences in gender or age between the 8 geographic positions.Conclusion/

Discussion: External thrombosed hemorrhoids are significantly more common in males. They are rarely present in midline positions and occur more commonly than expected on the left side of the anus. Despite the presence of more right sided internal hemorrhoids and their associated blood vessels, the relative paucity of right sided thromboses questions the current proposed pathogenesis of acute hemorrhoidal thrombosis.Geographic Distribution of ThrombosesValues expressed as n (%)