title: Colesevelam and colestipol: novel medication resins in the gastrointestinal tract.
abstract: We report the morphologic description of the bile acid sequestrants (BAS) colesevelam and colestipol, as well as the largest series of cholestyramine. Histologically similar medication resins from 4 institutions were prospectively collected over 1 year (26 specimens, 15 patients). Comorbidities included hyperlipidemia (4/15), hypertension (4/15), inflammatory bowel disease (4/15), coronary artery disease (3/15), diarrhea (7/15), hypothyroidism (2/15), and ischemic bowel (1/15). Sites of involvement included the esophagus (1/26), stomach (1/26), small intestine (1/26), ileocecal valve (1/26), and colorectum (22/26). Associated histologic diagnoses included normal (8/26), chronic mucosal injury (11/26), acute inflammation (9/26), erosion/ulceration (6/26), and cytomegalovirus (2/26). The BAS resins were histologically indistinguishable from each other; they were all eosinophilic on hematoxylin and eosin (H&E) and lacked internal "fish-scales." To validate these observations, respective medications were submitted for histologic processing; the processed medications were identical to those in the patient specimens. Rare, irregular "fracture" lines presented diagnostic pitfalls by mimicking the true "fish-scales" of Kayexalate and sevelamer. Clues to the correct identification of BAS include recognition that the "fracture" lines were subtle, irregular, and restricted to large fragments or thick sections, likely representing a processing artifact. Moreover, Kayexalate is violet on H&E and black on acid fast bacillus, and sevelamer characteristically displays a 2-tone color on H&E and is magenta on acid fast bacillus. An association with inflammatory injury was seen (15/26). We believe that the BAS are innocent bystanders in complicated patients, although we cannot exclude their ability to cause mucosal injury in specific settings.
authors.affiliation: *Department of Pathology ¶Department of Internal Medicine, Ohio State University Wexner Medical Center †Department of Pathology, Nationwide Children's Hospital, Columbus, OH ‡Department of Pathology, Mercy Medical Center, Des Moines, IA §Department of Laboratory Medicine and Pathology, Mayo Clinic, Scottsdale, AZ ∥Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, PA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Arnold
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Swanson
authors.forename: Clinton D
authors.initials: CD
authors.lastname: Crowder
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Frankel
authors.forename: Dora
authors.initials: D
authors.lastname: Lam-Himlin
authors.forename: Aatur D
authors.initials: AD
authors.lastname: Singhi
authors.forename: Peter P
authors.initials: PP
authors.lastname: Stanich
authors.forename: Christina A
authors.initials: CA
authors.lastname: Arnold
mesh_terms: D000328:Adult; D000368:Aged; D000499:Allylamine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000032:analysis; D000924:Anticholesteremic Agents / Q000009:adverse effects / Q000032:analysis*; D001706:Biopsy; D002792:Cholestyramine Resin / Q000032:analysis; D000069472:Colesevelam Hydrochloride; D003084:Colestipol / Q000009:adverse effects / Q000032:analysis*; D005260:Female; D005765:Gastrointestinal Agents / Q000009:adverse effects / Q000032:analysis*; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry / Q000187:drug effects; D007422:Intestines / Q000737:chemistry* / Q000187:drug effects; D007475:Ion Exchange Resins / Q000009:adverse effects / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D014481:United States
chemical_list: D000924:Anticholesteremic Agents; D005765:Gastrointestinal Agents; D007475:Ion Exchange Resins; D002792:Cholestyramine Resin; D000499:Allylamine; D003084:Colestipol; D000069472:Colesevelam Hydrochloride