Background : 5‐aminosalicylic acid (5‐ASA) has been associated with renal complications in inflammatory bowel disease. Renal function is typically monitored using serum creatinine; however, significant disease may predate increases in creatinine. Aims : To identify whether markers of early renal disease (urinary albumin, α‐1‐microglobulin [α‐1‐M] and N‐acetyl‐β‐D‐glucosaminidase [NAG], and serum cystatin C) are useful in the assessment of renal function in inflammatory bowel disease patients receiving 5‐ASA. Methods : Twenty‐one patients with a new diagnosis of inflammatory bowel disease were investigated. Samples were taken at diagnosis, and at 3‐monthly intervals after the commencement of 5‐ASA, for 1 year. Results : Mean creatinine clearance was 100 mL/min and did not change following treatment. Inflammatory bowel disease was not associated with albuminuria. Urinary N‐acetyl‐β‐D‐glucosaminidase and α‐1‐microglobulin at diagnosis were increased in 10 (48%) and 11 (52%) patients, respectively: treatment was not associated with consistent changes in urinary protein excretion. There was a significant correlation between cystatin C and creatinine clearance both at diagnosis (r=–0.533, P=0.0275) and combining the initial and follow‐up data (r=–0.601, P < 0.01), but not between creatinine and creatinine clearance (P > 0.05). Conclusions : Tubular proteinuria is an extra‐intestinal manifestation of inflammatory bowel disease irrespective of 5‐ASA treatment. Tubular proteins are not useful predictors of an adverse renal response to 5‐ASA. Serum cystatin C may be an improved marker of glomerular filtration rate in this setting.

SUMMARY BackgroundPatients attending for endoscopy are generally anxious and worried.

SUMMARYAim: To study 5-aminosalicylate nephrotoxicity in patients with inflammatory bowel disease in the UK.

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