From Ask Dr Wiki
Lymphocytic colitis, a subtype of microscopic colitis, is a rare condition characterized by chronic non-bloody watery diarrhea. The colonoscopy is normal but the mucosal biopsy reveals an accumulation of lymphocytes in the colonic epithelium and connective tissue (lamina propria). Collagenous colitis shares this feature but additionally shows a distinctive thickening of the subepithelial collagen table. The peak incidence of lymphocytic colitis is in persons over age 50; the disease affects women more than men.
Over-the-counter antidiarrheal drugs are effective for many people with lymphocytic colitis. Anti-inflammatory drugs, such as salicylates may also help. Corticosteroids or Mesalazines may be prescribed for people who do not respond to other drug treatment. The long-term prognosis for this disease is not clear.