Ulcerative colitis is a relapsing disorder characterized by attacks of bloody diarrhea with expulsion of stringy, mucoid material and lower abdominal pain and cramps that are temporarily relieved by defecation. These symptoms may persist for days, weeks, or months before they subside, and occasionally the initial attack may be severe enough to constitute a medical or surgical emergency. More than half of patients have mild disease, but almost all experience at least one relapse during a 10-year period. Colectomy cures intestinal disease, but extraintestinal manifestations may persist.
The factors that trigger ulcerative colitis are not known; infectious enteritis precedes disease onset in some cases. The onset of symptoms can occur shortly after smoking cessation in some patients, and smoking may partially relieve symptoms. Unfortunately, studies of nicotine as a therapeutic agent have been disappointing.
One of the most feared long-term complications of ulcerative colitis and colonic Crohn disease is the development of neoplasia. This process begins as dysplasia, which, just as in Barrett esophagus and chronic gastritis, is a step along the road to full-blown carcinoma. The risk for development of dysplasia is related to several factors:
Duration of disease. Risk increases beginning 8 to 10 years after disease initiation.
Extent of involvement. Patients with pancolitis are at greater risk than those with only left-sided disease.
Fig. 15.30 Pathologyofulcerativecolitis.(A)Endoscopicviewofsevereulcerativecolitiswithulcerationandadherentmucopurulentmaterial.(B)Totalcolectomywithpancolitisshowingactivedisease,withred,granularmucosainthececum(left) andsmooth,atrophicmucosadistally(right). (C)Sharpdemarcationbetweenactiveulcerativecolitis(bottom) andnormal(top). (D)Thisfull-thicknesshistologicsectionshowsthatdiseaseislimitedtothemucosa.Comparewith
Fig.15.29C .(Endoscopic image courtesy of Dr. Ira Hanan,The University of Chicago, Chicago, Illinois.) http://ebooksmedicine.net • Inflammation. Greater frequency and severity of active inflammation (characterized by the presence of neutrophils) may increase risk. This is another example of the enabling effect of inflammation on carcinogenesis (Chapter 6).
To facilitate early detection of neoplasia, patients typically are enrolled in surveillance programs approximately 8 years after diagnosis of IBD. An important exception to this approach is in patients with primary sclerosing cholangitis, who are at markedly greater risk for development of dysplasia and generally are enrolled for surveillance at the time of diagnosis. Surveillance requires regular and extensive mucosal biopsy, making it a costly practice. In many cases, dysplasia occurs in flat areas of mucosa that do not appear abnormal by eye. Thus, advanced endoscopic imaging techniques are being developed to try to enable the detection of early dysplastic changes.
Inflammatoryboweldisease(IBD)isanumbrellatermforCrohndiseaseandulcerativecolitis.
Crohndiseasemostcommonlyaffectstheterminalileumandcecum,butanysitewithinthegastrointestinaltractcanbeinvolved;skiplesionsandnoncaseatinggranulomasarecommon.
Ulcerativecolitisislimitedtothecolon,iscontinuousfromtherectum,andrangesinextentfromonlyrectaldiseasetopancolitis;neitherskiplesionsnorgranulomasarepresent.
BothCrohndiseaseandulcerativecolitiscanhaveextraintestinalmanifestations.
IBDisthoughttoarisefromacombinationofalterationsinhostinteractionswithintestinalmicrobiota,intestinalepithelialdysfunction,andaberrantmucosalimmuneresponses.