Fishberg concentration test /fish′berg/ , a test for renal function. The patient is given supper with not more than 200 mL of fluid and nothing thereafter. Urine voided during the night is discarded. The morning urine is saved, the patient is kept in bed, and the urine of 1 hour later and of 2 hours later is saved. If the specific gravity of any of these three specimens is less than 1.024, there is impairment of renal concentration.
