Why are Diverticula of the Rectum Uncommon? Angiomorphological Hypothesis

Abstract

IntroductionThe incidence of diverticula in the rectum is very low, ranging from 0.07 to 0.08% [1], compared to rates of 20 to 40% observed in the colon, despite the intra luminal pressures observed in the rectal lumen. The diverticula of the colon are called pseudo-diverticula. They are small (5 to 10mm), appear in multiple numbers (may be hundreds) and occur preferentially in the areas of penetration of vasa recta through the wall of the organ [2]. The natural history and patho-physiology of diverticular disease is complex and continues to be not fully understood nowadays, being considered multi factorial [2]. Most of the rectal diverticula are true diverticula, usually solitary (1 to 3 per case) and large (2cm in diameter) [3]. The etiology of rectal diverticula is still unknown [4]. They occur in a higher frequency in the lateral wall of the rectum, where the longitudinal muscle layer is thinner. They are observed in 2 to 2.4% of the cases of colon diverticulosis [5] and occur sometimes associated with scleroderma. In order to explain the low incidence of rectal diverticula, several hypotheses have been proposed: the protection offered by the perirrectal muscle-fibrous structures, the presence of a continuous circumferential muscle layer (the circular and longitudinal muscle layers) and the lesser peristaltic activity in the rectum [2,4]. ObjectivesThis work proposes an angiomorphologicaletiology to complement the theories already described to explain the low incidence of diverticular disease of the rectum and the rare occurrence of diverticula in the mesocolicside of the sigmoid colon: a hypothesis based on the location and course of the arteries through the colon wall and in the diameter of the lumen of the colon. Material and MethodsEighty specimens collected from human cadavers were used. Two groups were formed: 60 cases (1 st group) included the sigmoid colon, rectum and anal canal and the remaining 20 cases (2 nd group) included only the rectossigmoid transitions and the rectal and anal canal transitions. The specimens were all injected via the inferior mesenteric artery with colloidal barium sulfate with red colored The cause of rectal diverticula is still unknown and its incidence is very low when compared to the incidence of diverticular disease in the colon. The aim of this work is to propose an angiomorphological etiology to complement the theories already described to explain the low incidence of diverticular disease of the rectum and the rare occurrence of diverticula in the mesocolicside of the sigmoid colon: a hypothesis based on the location and course of the arteries through the colon wall and in the diameter of the lumen of the colon.

Pulsion diverticula of the rectum: Radiological diagnosis and clinical implications

“…1,2 However, the rectum itself is spared by this process due to its unique anatomy and blood supply. 10 The main reason for such discrepancy is that the three separate bands of longitudinal muscles known as teniae coli are fused together at the rectosigmoid junction and form a solid external layer around the rectum. This would eliminate its involvement by colonic diverticulosis, which develops due to mucosal protrusion at the entry sites of vasa recta along the margins of each teniae coli.…”

“…[4][5][6]11 They were found with an incidence of 0.07-0.08% on barium enema studies which included 2 large series of patients. 6,10 The exact pathogenesis for the development of these diverticula is not well-documented, since there are no distinct areas of anatomical weakness in the rectal walls. 10 Nevertheless, high intraluminal pressure can lead to focal outpouching of the rectal wall as a pulsion diverticulum.…”

“…6,10 The exact pathogenesis for the development of these diverticula is not well-documented, since there are no distinct areas of anatomical weakness in the rectal walls. 10 Nevertheless, high intraluminal pressure can lead to focal outpouching of the rectal wall as a pulsion diverticulum. This occurs most commonly when the anterior rectal wall protrudes towards the vagina as a rectocele in women with relaxed rectovaginal septum.…”