Colonic angiodysplasia and true diverticula: is there an association?

Aims: To investigate the pathology of colectomy specimens, from patients presenting with lower gastrointestinal haemorrhage, who had undergone preoperative mesenteric angiography. The angiography diagnoses ranged from active bleeding of unknown aetiology to angiodysplasia. Methods and results: The macroscopic and microscopic pathology of 11 colectomy specimens was studied. All the specimens contained blood on receipt with no obvious macroscopic source of haemorrhage identified. In all cases the large bowel demonstrated diverticula with an unusual topography. These were wide-mouthed, up to 20 mm across and exhibited a partly scattered distribution across the bowel; in two cases the diverticula contained blood clot. Histology demonstrated true diverticula invested by all muscle layers, exhibiting thick-walled vessels, within the submucosa and within the muscularis propria fibres, resembling the vascular elements identified in congenital vascular malformations. The two cases that contained blood clot revealed the thick-walled vessels to have ruptured into the diverticular lumen. Histology from the background colon between the diverticula demonstrated vascular lesions fulfilling the histological criteria for angiodysplasia; these features were also represented in the true-type diverticula. Most cases showed right-sided angiodysplasia and right-sided true diverticula. However, left-sided angiodysplastic lesions were also seen in association with left-sided true-type diverticula. Conclusions: We have identified the dual pathologies of angiodysplasia and multiple true-type diverticula, and suggest a topographical relationship between these two lesions. Furthermore, we propose that the thick-walled vessels within the true diverticula are congenitally abnormal, and raise the possibility that these vessels exert local haemodynamic effects, that effectively predispose the colon to acquired angiodysplastic phenomena.