Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (869 page)

   Hyperthyroidism

   Leukemia

   Muscle wasting diseases

   Paralysis

   Polycystic kidney disease

   Shock

   Urinary tract obstruction (e.g., from calculi)

   Vegetarian diets

   Limitations

   CrCl approximates GFR but overestimates it due to the fact that creatinine is secreted by the proximal tubule as well as filtered by the glomerulus.

   Measurement of CrCl should be considered in circumstances when the estimating equation based on serum creatinine is suspected to be inaccurate or for patients with estimated GFR >60 mL/minute/1.73 m
²
when a more accurate clearance measure is required for clinical decision making. Such circumstance may occur in people who are undergoing evaluation for kidney donation, treatment with drugs with significant toxicity that are excreted by the kidneys (e.g., high-dose methotrexate), or consideration for participation in research protocols.

   Indications for a clearance measurement because estimates based on serum creatinine may be inaccurate because of extremes of age and body size, severe malnutrition or obesity, disease of skeletal muscle, paraplegia or quadriplegia, a vegetarian diet, rapidly changing kidney function, or pregnancy.

   Drugs that may increase urine CrCl include enalapril, oral contraceptives, prednisone, and ramipril.