Nephrology Question 22 Instructor

How can you determine if a 24 hour urine collection is complete?

To determine adequacy of a 24 hour urine collection, one must look at the total amount of creatinine excreted in the collection period.

Males should excrete 200 umol/kg of creatinine per 24 hours and females should excrete 150 umol/kg/24 hours.

A 70 kg male performs a 24 hour urine collection. The lab report reveals:

Volume: 2.5 L
Creatinine: 34 mmol
Protein: 240 mg

Do you think this patient has abnormal protein excretion? Why?

This patient should have produced:

70 kg * 200 umol/kg = 14 mmol of creatinine in the 24 hour collection.

Since his collection had 34 mmol of creatinine, this represents an overcollection. Therefore, the protein measured is an overestimate of his true 24 hour protein excretion. One could estimate that his true protein excretion rate would be closer to:

(14 / 34) * 240 mg = 99 mg per day, which would fall within the normal range.

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