Colonic left-side increase of eosinophils: a clue to drug-related colitis in adults

The colon shows frequent eosinophilic infiltration in allergic proctocolitis of infants, whereas in adults, eosinophilic infiltration of the colon is less defined and may be found in different conditions including drug-induced colitis, even though the pathological findings are often inconsistent.

To quantify eosinophils in the mucosa of normal controls and to compare them with those of patients with abdominal symptoms related to 'drug colitis'.

Mucosal biopsies were obtained during colonoscopy in 15 controls and in 27 patients with abdominal symptoms, a history of probable 'drug-related colitis' and without obvious causes of eosinophilia.

The drugs related to the patient symptoms were nonsteroidal anti-inflammatory drugs (70%), antiplatelet agents (19%) and oestroprogestinic agents (11%). Colonoscopy was normal in 30% of patients and abnormal in 70%. Histology showed low content of inflammatory cells and normal crypt architecture in-patients with endoscopy similar to inflammatory bowel diseases. The eosinophil score was significantly higher in the left side of the colon in the patient group compared with controls.

The finding of an increased eosinophil count limited to the left (descending and sigmoid) colon is an important clue towards a diagnosis of drug-related colitis.