Segmental colitis associated with diverticulosis

The cause of segmental colitis associated with diverticula is unknown. Several factors may influence the development of the disease, such as local colonic ischemia, fecal stasis, or mucosal prolapse. SCAD shares some features with inflammatory bowel disease, including the increase of tumor necrosis factor (TNF) alpha during active disease, and decrease in TNF during health improvement. The pathogenesis of SCAD likely overlaps with inflammatory bowel disease.[3]

People with SCAD may develop left lower quadrant abdominal cramping, intermittent rectal bleeding, and chronic diarrhea.[1] Rectal bleeding (hematochezia) is the most common symptom,[4] and is the presenting complaint in more than 70% of individuals with SCAD.[5]

There are four types of SCAD, based on endoscopic appearance. Pattern A is characterized by involvement of crescentic folds and is the most common type of SCAD (52%).[2] Pattern B has an appearance similar to mild-to moderate ulcerative colitis (30.40%), whereas pattern C appears similar to Crohn's disease (10.90%).[2] Pattern D is the least common, and appears similar to severe ulcerative colitis (6.50%).[2]

SCAD is diagnosed via colonoscopy, often incidentally during examination for unrelated concerns. Colonoscopy shows erythema of the colonic mucosa, which may be characterized by friability and exudate.[1] The descending and sigmoid colon are typically involved. Biopsies of the affected area and the unaffected rectum confirm the diagnosis.[1] Biopsies of SCAD show evidence of chronic inflammation. Rectal biopsies show normal mucosa.

It is important and occasional difficult to distinguish SCAD from inflammatory bowel disease (IBD).[1][6] Biopsies reveal histologic findings that are identical in both conditions.[1] However, ulcerative colitis usually affects the rectum and inflammation in IBD extends to areas of the colon without diverticulosis.[1]

Additional causes of colitis should be evaluated, including infectious and medication-induced, particularly NSAID-associated.[1]

Laboratory results are usually normal in individuals with SCAD. The white blood cell count may be mildly elevated. Fecal calprotectin, a marker of colon inflammation, may be elevated in individuals with SCAD.[7] Fecal calprotectin may assist in distinguishing SCAD from irritable bowel syndrome.[7]

Imaging tests, including CT abdomen, may show inflammation or thickening of the distal colon, with associated diverticulosis. There may be evidence of inflammation extending around the bowel (fat stranding).

There are several options in treatment for SCAD. Data is lacking, and there are no prospective trials comparing different therapies for SCAD. As of 2017, there are no guidelines available to direct treatment.[3] Treatment may include antibiotics, aminosalicylates, and corticosteroids. Antibiotics include ciprofloxacin and metronidazole, given for 14 days. If symptoms recur after improvement with antibiotics, a second course of antibiotics may be given.

If an initial course of antibiotics is ineffective, then mesalamine may be tried. If mesalamine is ineffective, then a course of prednisone may be helpful. In severe cases of SCAD, where corticosteroids are unable to be discontinued, then surgery may be considered (segmental resection).

The natural history of SCAD lacks rigorous study, with little data regarding long term outcomes. However, the course appears to largely benign. In cases that require surgery, recurrence of disease is rare.[8] Long term medication therapy is rarely necessary.[3] Over a course of 7 years, about half of people with SCAD experience a recurrence of symptoms.[9] About a third of people have a mild recurrence.[9]

Among individuals with diverticulosis, the prevalence of SCAD ranges from 0.3 - 1.3%.[10] SCAD is more common in men, with an average of 64 years upon diagnosis.[10][11]

SCAD was first described in a case series in 1984.[12] SCAD was initially believed to represent a complication of diverticular disease.[13] As evidence suggested increasing overlap with inflammatory bowel disease, SCAD became recognized as a distinct condition.[13]