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Tubulo-interstitial nephritis (TIN) in patients affected by inflammatory bowel disease, both ulcerative colitis and Crohn’s disease, is usually considered as drug-associated to aminosalicylate. We report a rare case of granulomatous active tubulo-interstitial nephritis in a young patient with a recent diagnosis of ulcerative colitis naïve to aminosalicylate treatment. The patient has been successfully treated with steroids administration. Our purpose is to sensitize that TIN should always to be considered in differential diagnosis an extra-intestinal manifestation of bowel disease.

Background: In recent years, several case reports have been published suggesting an association between the use of 5-aminosalicylic acid (5-ASA) in patients with inflammatory bowel disease (IBD) and the development of chronic tubulo-interstitial nephritis. Apart from lesions associated to 5-ASA treatment, however, it is clear that IBD itself may also induce renal impairment, albeit the frequency is unknown. Methods: During 1 year, all IBD patients seen at the outpatient clinic of 27 European centres of gastro-enterology were registered and screened for renal impairment controlling for a possible association with 5-ASA therapy. Patients were questioned about their medical and drug history and their IBD disease activity. Renal screening (calculated creatinine clearance) was performed at baseline, after 6 and 12 months. Results: Included patients (n = 1,529) had a mean age of 39 (range 14 - 98), 56% had Crohn's disease, 42% ulcerative colitis and 2% indeterminate colitis. Half of the patients used 5-ASA during the study period. Decreased creatinine clearance was observed in 34 patients, among them 13 with chronic renal impairment. Comparing patients with and without renal impairment, no difference could be observed in 5-ASA consumption. In contrast, patients with renal impairment were significantly older, had a lower body mass index and showed a higher frequency of male sex, bowel resection and stoma. Conclusion: Although the association between 5-ASA therapy and chronic tubulo-interstitial nephritis is clearly described in several case reports, this prospective study came to the reassuring conclusion that renal impairment in IBD patients is not frequently observed and is rarely associated with 5-ASA therapy.