Fig. 15.25 Sigmoiddiverticulardisease.(A)Endoscopicviewoftwosigmoiddiverticulae.ComparetoB. (B)Grossexaminationofaresectedsigmoidcolonshowsregularlyspacedstool-filleddiverticulae.(C)Cross-sectionshowingtheoutpouchingofmucosabeneaththemuscularispropria.(D)Low-powerphotomicrographofasigmoiddiverticulumshowingprotrusionofthemucosaandsubmucosathroughthemuscularispropria.(Endoscopic image courtesy of Dr. Ira Hanan,The University of Chicago, Chicago, Illinois.)
Continuous colonic involvement, Skip lesions develop complaints including intermittent cramping, continuous lower abdominal discomfort, constipation, and diarrhea. Longitudinal studies have shown that while diverticula can regress early in their development they often become more numerous and larger over time. Whether a high-fiber diet prevents such progression or protects against diverticulitis is unclear. Even when diverticulitis occurs, it most often resolves spontaneously or after antibiotic treatment, and relatively few patients require surgical intervention.
Inflammatory bowel disease (IBD) is a chronic condition resulting from complex interactions between intestinal microbiota and host immunity in genetically predisposed individuals resulting an inappropriate mucosal immune activation. IBD encompasses two entities, Crohn disease and ulcerative colitis. The distinction between ulcerative colitis and Crohn disease is based, in large part, on the distribution of affected sites and the morphologic expression of disease at those sites (
Fig. 15.26
Table 15.5 ). Ulcerative colitis is limited to the colon and rectum and extends only into the mucosa and submucosa. By contrast, Crohn disease, also referred to as regional enteritis (because of frequent ileal involvement), may involve any area of the gastrointestinal tract and is frequently transmural.
Both Crohn disease and ulcerative colitis frequently present during adolescence or in young adults, although some studies suggest a second, smaller peak in the incidence of both diseases after the fifth decade. In Western http://ebooksmedicine.net
Table 15.5 Features of Crohn Disease and Ulcerative Colitis Feature Crohn Disease Ulcerative Colitis submucosaPseudopolypsModerateMarkedUlcersDeep, knifelikeSuperficial, broad-basedLymphoid reactionMarkedModerateFibrosisMarkedMild to noneSerositisMarkedNoGranulomasYes (∼35%)NoFistulas/sinusesYesNo
Perianal fistulaYes (in colonic Nodisease)Fat/vitamin YesNomalabsorptionMalignant potentialWith colonic YesinvolvementRecurrence after CommonNosurgeryToxic megacolonNoYesNOTE: Not all features may be present in a single case.
industrialized nations, IBD is most common among whites and, in the United States, occurs three to five times more often among eastern European (Ashkenazi) Jews. This predilection is at least partly due to genetic factors, as discussed below. The geographic distribution of IBD is highly variable, but it is most prevalent in North America, northern Europe, and Australia. The incidence of IBD worldwide is on the rise and it is becoming more common in regions in which the prevalence was historically low. The hygiene hypothesis, first applied to asthma, says that childhood and even prenatal exposure to environmental microbes resets the immune system in a way that prevents excessive reactions. Extrapolated to IBD, it suggests that a reduced frequency of enteric infections due to improved hygiene has resulted in inadequate development of regulatory processes that limit mucosal immune responses early in life. While attractive and commonly stated, firm evidence is lacking and hence the increasing incidence of IBD remains mysterious.