Colesevelam and colestipol: Novel medication resins in the gastrointestinal tract

Michael A. Arnold, Benjamin J. Swanson, Clinton D. Crowder, Wendy L. Frankel, Dora Lam-Himlin, Aatur D. Singhi, Peter P. Stanich, Christina A. Arnold

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1530-1537
Number of pages8
JournalAmerican Journal of Surgical Pathology
Issue number11
StatePublished - 2014


  • Bile acid sequestrant (BAS)
  • Bile acid-mediated diarrhea (BAM)
  • Cholestyramine (LoCholest; LoCholest; Prevalite
  • Colesevelam (Welchol)
  • Colestipol (Colestid)
  • Fish-scale
  • Gastrointestinal tract (GIT)
  • Questran)
  • Renagel)
  • Resin
  • Sevelamer (Renvela
  • Sodium polystyrene sulfonate (Kayexalate)

ASJC Scopus subject areas

  • Anatomy
  • Surgery
  • Pathology and Forensic Medicine


Dive into the research topics of 'Colesevelam and colestipol: Novel medication resins in the gastrointestinal tract'. Together they form a unique fingerprint.

Cite this