BACKGROUND: Worsening azotemia following initiation of angiotensin blockade(AB), in patients with CKD, RAS with/without precipitating factors is recognized. Small increases inserum creatinine following initiation of AB occur and must not warrant drug discontinuation. We anecdotallyhad observed improvement in CKD in patients with normal renal arteries and no precipitating factors,following termination of AB. The worldwide ESRD epidemic, coincident with increasing use of AB, promptedus to hypothesize a late-onset azotemia in such CKD patients. MATERIAL/METHODS: Over 30 months, 103 patientswith worsening azotemia, while on AB were evaluated. Ninety-seven patients with abnormal MRA and/or withprecipitating factors were excluded. In the remaining five, AB was discontinued, and GFR monitored. RESULTS:One male, four females, mean age 66.2 years. Three diabetic/hypertensives, one SLE/hypertensive, onediabetic/kidney transplant recipient. Mean stable AB, 25.2 months, (6-66 months). Mean follow up, 11.8months. One month following discontinuation of AB, GFR increased by a mean 45%. Mean serum creatininedecreased from 2.9+/-0.9 to 1.8+/-0.4 mg/dL (p=0.04). Uremic symptoms in 3, hyperkalemia in one, secondaryhyperparathyroidism in one, resolved. Two with anemia, now require less erythropoietin. CONCLUSIONS:We called this unrecognized potentially reversible late-onset worsening azotemia, occurring several monthsto years on stable AB, in CKD patients with normal renal arteries, without precipitating factors, late-onsetrenal failure from angiotensin blockade (LORFFAB). Pathophysiologically, the concept of microvascularRAS is invoked. The extent of LORFFAB, with millions of patients worldwide on AB, remains conjecturaland warrants further investigation.

Keywords: Aged, 80 and over, Angiotensin II Type 1 Receptor Blockers - adverse effects, angiotensin receptor antagonists, Angiotensin-Converting Enzyme Inhibitors - adverse effects, Blood Pressure, Creatinine - urine, Glomerular Filtration Rate, Kidney Failure, Chronic - urine, Prospective Studies, Uremia - physiopathology, Wisconsin