Renal Safety of Topical Diclofenac in Adults with Increased Renal Risk: A Systematic Review

Background and Objectives: Topical diclofenac is recommended over oral non-steroidal anti-inflammatory drugs (NSAIDs) for osteoarthritis, particularly in older adults and those with comorbidities, on the assumption that low systemic absorption limits renal effects. Whether this presumed safety extends to patients already at increased risk of kidney injury has not been systematically evaluated. This review assessed the evidence on renal outcomes of topical diclofenac in adults. Materials and Methods: We conducted a systematic review (PROSPERO CRD420261393454) of studies reporting renal outcomes after topical diclofenac exposure. PubMed, Embase, Web of Science, and Scopus were searched from inception to 19 April 2026. Studies were stratified a priori into increased-renal-risk and general populations and synthesised separately, without pooling. Risk of bias was assessed with RoB 2, ROBINS-I, and JBI tools, certainty with GRADE, and synthesis followed the SWiM framework.