[Colonic diverticulosis and its complications: pathogenesis, classification and clinical implications].

Current understanding of the pathogenesis of colonic diverticulosis and its complications has certain implications for current therapy concepts, which are summarised here. Colonic diverticula in the Western world are pseudodiverticula predominating in the sigmoid colon. Pathogenesis is multifactorial and includes low-fibre diet, dysmotility, increased intraluminal pressure and morphological changes. Uncomplicated diverticulitis results from microperforations, contradicting the hypothesis of the "abscessed diverticulum". Administration of antibiotics for treatment is controversial. Complicated sigmoid diverticulitis is characterised by an intensive inflammatory infiltrate with macrophages. Immunosuppression and especially steroid intake are identified as risk factors. Nowadays, elective or emergency resection is generally recommended as therapy of first choice. However, contrary concepts with merely conservative treatment or drainage--even for perforated diverticulitis--are emerging. The pathogenesis of chronically recurrent diverticulitis is poorly understood and concepts are changing. Resection after the second episode is replaced by a risk-adapted strategy. Diverticular bleeding occurs due to rupture of a vas rectum at the fundus of the diverticulum. Conservative and endoscopic management is the first line and surgical resection plays a role as salvage-strategy in case of recurrent and life-threatening bleeding. Localising the bleeding, i.e., with angiography, is crucial prior to surgery. The pathophysiology of colonic diverticulosis is complex and incompletely understood and linked with several controversial issues, regarding treatment strategies.