In a patient with gross hematuria the height of erythrocytes in a spun urine sample can give an indication of the amount of blood loss. This is similar to the hematocrit done on the peripheral blood.


Specimen: a urine specimen that is well mixed


Test: Pipette a sample of urine into a narrow tube and centrifuge so that that erythrocytes are packed in the bottom of the tube.


percent erythrocytes in urine =

= (height of erythrocytes in mm) / (total height of the specimen in mm) * 100%


volume of erythrocytes in the urine in mL =

= (total urine volume in mL) * (percent erythrocytes)


volume of blood loss in mL =

= (volume of erythrocytes in the urine) / (hematocrit in the peripheral blood)


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