Segmental colitis associated with diverticulosis (SCAD) is a condition characterized by localized

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

in the colon, which spares the

rectum The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the s ...

and is associated with multiple sac-like protrusions or pouches in the wall of the colon (

diverticulosis Diverticulosis is the condition of having multiple pouches (diverticulum, diverticula) in the colon (anatomy), colon that are not inflamed. These are outpockets of the colonic mucosa and submucosa through weaknesses of muscle layers in the col ...

). Unlike

diverticulitis Diverticulitis, specifically colonic diverticulitis, is a gastrointestinal disease characterized by inflammation of abnormal pouches—diverticula—which can develop in the wall of the large intestine. Symptoms typically include lower abdominal ...

, SCAD involves inflammation of the colon between diverticula (interdiverticular mucosa), while sparing the diverticular orifices. SCAD may lead to abdominal pain, especially in the left lower quadrant, intermittent rectal bleeding and chronic diarrhea. The cause of SCAD is unknown, but may be related to local colonic ischemia,

fecal Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

stasis, or

mucosal prolapse A rectal prolapse occurs when walls of the rectum have prolapsed to such a degree that they protrude out of the anus and are visible outside the body. However, most researchers agree that there are 3 to 5 different types of rectal prolapse, depend ...

. The factors that cause SCAD likely overlap with inflammatory bowel disease. There are four types of SCAD, which are categorized based on the appearance during colonoscopy. Pattern A is characterized by involvement of crescentic folds and is the most common type of SCAD (52%). 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%). Pattern D is the least common, and appears similar to severe ulcerative colitis (6.50%). SCAD is diagnosed by colonoscopy. Additional testing may be necessary to rule out infectious causes of colitis. Evaluation should include assessment for additional causes of colitis, such as medication induced ( checkpoint inhibitors, NSAIDs, etc.). Laboratory results are usually normal in SCAD, although the

white blood cell count A complete blood count (CBC), also known as a full blood count (FBC), is a set of medical laboratory tests that provide information about the cells in a person's blood. The CBC indicates the counts of white blood cells, red blood cells and pl ...

may be mildly elevated.

Fecal calprotectin Faecal calprotectin ( or fecal calprotectin) is a biochemical measurement of the protein calprotectin in the stool. Elevated faecal calprotectin indicates the migration of neutrophils to the intestinal mucosa, which occurs during intestinal in ...

, a marker of colon inflammation, may be elevated. Computed tomography of the abdomen is not routinely necessary, but may show thickening or inflammation in the distal colon (sigmoid colon) with associated diverticulosis. Treatment may consist of antibiotics,

aminosalicylate An aminosalicylate is a class of medications that is often used to treat ulcerative colitis and Crohn's disease. The class includes among others: * 4-Aminosalicylic acid * Balsalazide * Olsalazine *Sulfasalazine *Mesalazine (5-Aminosalicylic acid) ...

s (mesalamine), or prednisone. In rare cases, surgery with segmental resection may be considered. The long term prognosis is likely benign, although data is lacking. The prevalence of SCAD ranges from 0.3 - 1.3 percent.

Types

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%). 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%). Pattern D is the least common, and appears similar to severe ulcerative colitis (6.50%).

Signs and symptoms

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

Pathophysiology

The cause of segmental

colitis Colitis is swelling or inflammation of the large intestine ( colon). Colitis may be acute and self-limited or long-term. It broadly fits into the category of digestive diseases. In a medical context, the label ''colitis'' (without qualification) ...

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 Inflammatory bowel disease (IBD) is a group of inflammation, inflammatory conditions of the colon (anatomy), colon and small intestine, Crohn's disease and ulcerative colitis being the principal types. Crohn's disease affects the small intestine a ...

, including the increase of

tumor necrosis factor Tumor necrosis factor (TNF, cachexin, or cachectin; formerly known as tumor necrosis factor alpha or TNF-α) is an adipokine and a cytokine. TNF is a member of the TNF superfamily, which consists of various transmembrane proteins with a homolog ...

(TNF) alpha during active disease, and decrease in TNF during health improvement. The pathogenesis of SCAD likely overlaps with inflammatory bowel disease.

Diagnosis

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. The descending and

sigmoid colon The sigmoid colon (or pelvic colon) is the part of the large intestine that is closest to the rectum and anus. It forms a loop that averages about in length. The loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thus ''s ...

are typically involved. Biopsies of the affected area and the unaffected rectum confirm the diagnosis. 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). Biopsies reveal histologic findings that are identical in both conditions. However, ulcerative colitis usually affects the rectum and inflammation in IBD extends to areas of the colon without diverticulosis. Additional causes of colitis should be evaluated, including infectious and medication-induced, particularly NSAID-associated. Laboratory results are usually normal in individuals with SCAD. The white blood cell count may be mildly elevated.

, a marker of colon inflammation, may be elevated in individuals with SCAD. Fecal calprotectin may assist in distinguishing SCAD from irritable bowel syndrome. 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).

Treatment

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. Treatment may include antibiotics,

s, and

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...

s. 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).

Prognosis

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. Long term medication therapy is rarely necessary. Over a course of 7 years, about half of people with SCAD experience a recurrence of symptoms. About a third of people have a mild recurrence.

Epidemiology

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

History

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

References

{{Digestive system diseases Diseases of intestines