Elevations in serum creatinine concentration: concerning or reassuring?

The use of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) has significantly reduced morbidity and mortality across the continuum of vascular disease. The utilization of these agents, however, remains suboptimal. The drugs are not prescribed in many patients because of concerns regarding their effects on renal function. Despite overwhelming evidence in favor of renoprotection, it is not uncommon for the glomerular filtration rate (GFR) to decrease shortly after starting treatment with an ACE inhibitor or ARB. This response is functional in nature and should be expected based on renal physiology and its dependence on the renin-angiotensin system to maintain GFR. Unfortunately, this phenomenon sometimes is viewed as an adverse effect or an indicator of underlying pathology. Although somewhat counterintuitive, early elevations in serum creatinine concentration are associated with improved long-term renal outcomes in patients with renal insufficiency and thus support, rather than condemn, continued treatment. Clinicians should be aware of the physiologic course associated with blockade of the renin-angiotensin system so that these agents will not be withheld unnecessarily.