Collagenous colitis

Collagenous colitis
Micrograph of collagenous colitis. H&E stain.
Specialty	Gastroenterology

Collagenous colitis is an inflammatory condition of the colon. Together with the related condition lymphocytic colitis, it is a subtype of microscopic colitis, which is sometimes considered to be an inflammatory bowel disease along with Crohn's disease and ulcerative colitis. Collagenous colitis is characterized by inflammation that specifically affects the colon (i.e. colitis), and a clinical presentation that involves watery diarrhea but a lack of rectal bleeding. The peak incidence is in the 5th decade of life, and women more are more frequently affected than men.

Signs and symptoms

Collagenous colitis causes chronic watery diarrhea with increased stool frequency. Some patients report nocturnal diarrhea, abdominal pain, bowel urgency, fecal incontinence, fatigue, dehydration and weight loss. Patients report a significantly diminished quality of life.

Causes

The cause of collagenous colitis is unknown. A connection with autoimmune disorders such as celiac disease is suspected, as up to 40% of patients with collagenous colitis have an autoimmune disease. Use of nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs) and beta blockers also appear to increase the risk of collagenous colitis, but the cause of this is not known.

Diagnosis

On colonoscopy, the mucosa of the colon typically looks normal, but biopsies of affected tissue usually show deposition of collagen in the lamina propria, which is the area of connective tissue between colonic glands. Radiological tests, such as a barium enema are also typically normal.

Treatment

First line treatment for collagenous colitis is the use of budesonide, a steroid that works locally in the colon and is highly cleared by first pass effect. Other medications that can be used include the following:

• Bismuth agents, including Pepto-Bismol
• 5-aminosalicylic acid
• Immunosuppressants, including azathioprine
• Infliximab

Pilot-scale studies have shown some evidence of possible benefit for both Boswellia serrata extract and specific strains of probiotics in the treatment of collagenous colitis, although larger sample sizes are needed to confirm the results.

Epidemiology

One epidemiological study done on data from Olmsted County, Minnesota reported previous incidence rates found in the literature as ranging from 0.6 per 100,000 person-years (based on French data from 1987–1992) to 5.2 per 100,000 person-years (from an Icelandic study based on data from 1995-1999), while the authors themselves found an incidence rate of 3.1 per 100,000 person years in Olmsted County across the entire period 1985-2001. Based only on the subset of the data from 1998-2001, however, the authors found a higher rate of 7.1 per 100,000 person-years, an incidence rate which exceeded those of Crohn's disease and ulcerative colitis. The previously mentioned Icelandic study also found increasing rates through the studied period, with the incidence rate in Iceland increasing from 2.2 in 1995 to 8.3 in 1999. Women appear to be more frequently affected by collagenous colitis than men, with the Icelandic study finding a female-male ratio of 7.9 in diagnosed cases and the Olmested County study finding a female-male ratio of 4.4.