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Puzzling 'Improvement' in Creatinine Clearance in a Diabetic, Hypertensive PatientI have a 70 year-old, diabetic, hypertensive African American paitient who is 6 ft 2 in and weighs 192 lb. In January 1996, his creatinine clearance was 41 mL/min/1.732 with a urine volume of 1,070 mL; at that time, the serum creatinine level was 1.8 mg/dL and the urinary creatinine level was 1.1 mg/kg/24h. In March 1999, his creatinine clearance was 44 mI/mm/1.732 with a urine volume of 2,500 mL, the serum creatinine level was 1.8 mg/dL, and the urinary creatinine level was 3.7 mg/kg/24 h. The proteinuria has worsened from 417 to 875 mg/24 h. Has his creatinine clearance "improved" because of a larger urine sample? Should I repeat the test? Higinio Fuentes, MD The answer to both questions is no. The different results reflect the ongoing changes seen in diabetic patients in whom renal disease progresses. While the first creatinine clearance value may have been low because of an incomplete collection, the more recent test that shows hyperfiltralion (a glomerular filtration rate of more than 120 mL/min) does not confirm this possibility. The continued increase in proteinuria indicates worsening renal function. Serum creatinine and blood urea nitrogen levels remain normal even when the creatinine clearance rises with the appearance of proteinuria. Only when azotemia occurs do blood tests--the least sensitive marker for early renal disease--rise in value. Your patient needs to achieve glycosylated hemoglobin values of 8% or less. He would also benefit from angiotensin II receptor blocker to protect renal function and to treat hypertension. Avoid using angiotensin-converting enzyme inhibitors in this patient, since they pose a higher risk of angioedema in African Americans. Eric A. Ozeck, MD For more information: This article appeared in the July issue of Consultants: Consultations in Primary Care Vol 39, Issue 7, p. 1906. |
