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A Patient with Sigmoid Colon Resection for Diverticulitis, and Pathology Report Reading 'Chronic Colitis'
Q: Is Diverticular-Associated Colitis a Subset of Inflammatory Bowel Disease, and Does My Patient Need Any Medical Therapy to Prevent Recurrence of Colitis?
A: Diverticular-associated colitis is an interesting clinical scenario that is occasionally encountered by the practicing gastroenterologist. The incidence of diverticular disease is very high in Western societies, with a prevalence estimated to approach 50% to 60% after the age of 50 years. The majority of patients are asymptomatic, whereas far fewer have bleeding and diverticulitis. An associated clinical entity that is increasingly recognized is segmental colitis-associated diverticular disease (SCAD). The patient in this clinical question may indeed have SCAD; therefore, we will discuss the clinical manifestations of this disorder, including diagnosis and treatment, and also demonstrate how SCAD may be a subset of inflammatory bowel disease (IBD).
Diagnosis
The literature suggests that a spectrum of disease severity may exist within SCAD, but the hallmark diagnostic feature is inflammation detected on colonoscopy in an area of diverticulosis, usually in the sigmoid colon. The other key feature is that this inflammation is confined to the area of diverticulosis; the rectum must be endoscopically and histologically normal, and the colon proximal to the diverticula must be normal. The inflammation unique to SCAD is located in the interdiverticular area (between the diverticula) and not within the diverticular orifices themselves, as is seen in acute diverticulitis. Two less-common scenarios where inflammation can be seen both in and around the diverticula are severe SCAD and a patient with a diagnosis of ulcerative colitis (UC) who also has diverticulosis of the sigmoid colon. The latter situation is distinguished by an abnormal rectum consistent with UC. The endoscopic appearance of the inflammation may be variable, but four different types have been described. The most common and mildest form appears endoscopically as nonraised red spots, often seen on the crescents of the colon folds (Figure 1). The second form is a UC type with loss of vascular markings, erythema and erosions (Figure 2). There is also a Crohn's disease (CD) type where there may be apthous-type ulcers interspersed throughout mucosa that otherwise appears normal. The final type that has already been alluded to is severe SCAD, where there may be severe edema, erythema and ulceration in the area of diverticulosis.
Figure 1. Endoscopic image of a mild form of segmental colitis-associated diverticular disease (SCAD) with cherry red spots in an area of diverticulosis.
Figure 2. Endoscopic image of ulcerative colitis-type SCAD.
Images: Hamilton MJ, Friedman S
These endoscopic features are likely the most useful to make the diagnosis of SCAD, but the histology provides important confirmatory information; therefore, it is essential to take biopsies both in and around the area of inflammation, especially in the rectum. Histologic evidence of inflammation should be confined to the area of diverticulosis, and inflammation present in the rectum or in the area proximal is more consistent with another type of IBD. If inflammation is confined to the area of diverticulosis, the histologic appearance can resemble that of a nonspecific IBD with an acute infiltrate, including neutrophils in and around the crypts, and chronic immune cells, including lymphocytes and plasma cells in the lamina propria. There may be architectural changes, such as crypt branching. Granulomas are not a feature of SCAD and should prompt further work-up for CD. It is also important to note that the histology may be normal in as many as half of the patients with milder forms of SCAD.
Blood tests are unlikely to provide additional diagnostic support in SCAD; white and red cell counts, platelets, and C-reactive protein were normal for the most part in a prospective study.
Courses of Treatment
Patients who are symptomatic and diagnosed with SCAD after colonoscopy are good candidates for medical treatment. The available literature suggests that 5-aminosalicylic acid (5-ASA)-based treatment regimens (given orally and/or topically) are effective in treating the nonsevere forms of SCAD. Symptoms will remit usually within 6 weeks, and less than half of these patients will have a recurrence. No data are available regarding postoperative recurrence of SCAD, but as long as a patient has remaining diverticula, the likelihood of recurrence is possible in this chronic disorder. Patients with severe SCAD (based on symptoms and endoscopic appearance) may need the addition of steroids to obtain remission. It is also possible that this group of patients may not adequately respond to any medical therapy and are therefore candidates for surgical resection of the affected area. According to the literature, it does not appear that patients with SCAD develop penetrating features (eg, abscess or fistula) that may be seen in CD and complicated acute diverticulitis.
SCAD represents a subset of IBD based on several key features of the disease. The endoscopic and histologic appearance may be indistinguishable from IBD within the area of diverticulosis. The inflammation is responsive to the same core medications used in IBD including 5-ASA (eg, mesalamine). The inflammatory cytokine tumor necrosis factor (TNF)-alpha has been found to be elevated in SCAD, and a case report describes a patient who was successfully treated with infliximab. Lastly, symptoms and signs of SCAD may recur after a patient has been in remission, confirming the chronic nature of this disorder.
There has been speculation as to what may drive the inflammation seen in SCAD, but there are no definitive studies in this area. Diverticula in the sigmoid colon may be prone to fecal stasis; therefore, changes in the surrounding microbiota may serve as the nidus for inflammation. It is not known whether these patients have any underlying genetic defects that predispose them to this chronic inflammation or whether environmental factors, such as smoking, exacerbate SCAD.
Conclusion
The patient in this scenario likely had SCAD at the time of the operation, which may have responded to 5-ASA-based therapies and steroids (if needed) to induce remission. SCAD is a chronic inflammatory disorder of the bowel that is likely a subset of IBD; therefore, this patient has a small risk of recurrence in the future.
Excerpted from:
Rubin DT, Friedman S, Farraye FA. Curbside Consultation in IBD: 49 Clinical Questions, Second Edition (pp 145-148). ©2015 SLACK Incorporated.
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