Which of the following is the next step in your evaluation and management?
ExplanationThe correct answer is C. Proteinuria may be either transient or persistent. Transient proteinuria is often due to fever, exercise, or other causes and is not associated with ignificant kidney disease. Transient proteinuria is found in 7% of women and 4% of men. It often resolves spontaneously, and subsequent urine tests will probably be negative. However, at this point you do not know if this case will be transient or persistent proteinuria. Orthostatic proteinuria is a common type of transient proteinuria seen in young, healthy persons. Up to 5% of adolescents have orthostatic proteinuria, and young adults may present with it as well. Protein is spilled in the urine when the patient is upright, but not when recumbent. There are two ways to determine recumbent urine protein: an easy way and a hard way. The easy way is to have the patient void before going to bed, stay supine all night (~8 hours), and collect urine immediately upon waking. This urine is checked for protein/creatinine ratio. Another urine must be checked for protein/creatinine after the patient has been upright. If the upright is abnormal and the recumbent is normal, you have diagnosed orthostatic proteinuria. The hard way involves splitting a 24-hour urine collection. Orthostatic proteinuria is a benign condition that usually resolves as the patient ages, and it require no additional evaluation. A finding of 1 g of protein in a 24-hour urine collection is abnormal (normal <0.15 g per day), but it does not yet reach the nephrotic range (>3 g per day). Reassuring the patient at this stage is not appropriate. CT scan of the abdomen and pelvis is unlikely to add any new information. Referring for renal biopsy is premature.
