Microscopic ileitis in diverted and non-diverted enteric segments: an under-recognized condition with a multifactorial etiology

Publication date: Available online 27 March 2018
Source:Human Pathology
Author(s): Chunlai Zuo, Zhiyan Fu, Edward C. Lee, Llewellyn Foulke, Gloria Q. Young, David Cubero Rego, Hwajeong Lee
Microscopic ileitis has been infrequently reported in the literature with the few reported cases usually associated with concurrent microscopic colitis. Having encountered a case of collagenous ileitis involving the diverted distal limb of a loop ileostomy and sparing the proximal limb, we examined additional cases of loop ileostomy, end ileostomy, colostomy, and the accompanying diverted colorectal segment for features of microscopic ileitis and colitis. A total of 101 cases of diverted and non-diverted enteric segments were examined from 37 loop ileostomies, 16 end ileostomies and 12 colostomies status post Hartmann's procedure. The patients' clinical histories, including demographics and risk factors for microscopic colitis were obtained from electronic medical records. The index case and an additional case showed collagenous ileitis; the former in the diverted distal limb, and the latter in the non-diverted proximal limb of the loop ileostomy. The latter was associated with high ileostomy output with watery diarrhea. Two additional cases showed lymphocytic ileitis; one in the non-diverted proximal limb of loop ileostomy, and the other in the end ileostomy. All 4 patients had one or more risk factors for microscopic colitis. The etiology of microscopic ileitis appears to be multifactorial, and microscopic ileitis may be under-diagnosed. The diverted enteric segment may be involved by microscopic enteritis suggesting additional factors other than fecal stasis and altered bacterial flora may be contributing to its pathogenesis. When microscopic ileitis is encountered, identifying associated risk factors, recognizing incipient clinical symptoms of microscopic colitis and considering other associated disease or conditions is warranted.



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