9.3 Evaluating Kidney Function

Question 1

List 7 contemporary investigative methods to study renal disease/function

Answer 1

1. Urine dipstick (detects certain substances)
2. Urine microscopy (test for cells, bacteria, crystals etc.)
3. Protein analysis (protein/albumin or albumin/creatinine)
4. Serum biomarkers (creatinine, blood urea nitrogen [BUN])
5. Radiographic imagery (CT/MRI of kidneys)
6. Nuclear medicine
7. Renal biopsy (needle through back)

Question 2

GFR vs eGFR

Answer 2

• GFR: measures clearance rate of substance such as inulin
• eGFR: estimatees based on age, gender, and serum creatinine (estimated, so not perfect, but far more practical)

Question 3

List and explain two serum biomarkers that can be used to measure renal function. Explain their limitations

Answer 3

1. Blood Urea nitrogen (BUN); increased may indicate slowed clearance of urea
2. Creatinine; increased may indicate slow clearance also

BUN can be affected by protein status (since eating more protein increases urea).

Serum creatinine can be affected by age, gender, and muscle mass (why?). It does not increase linearly as GFR decreases, meaning a large amount of GFR (50-60%) may be lost before creatinine is abnormal.