Box 1.

Example- calculating residual kidney function

Problem: A 46-year-old female patient with plasma BUN 74 (average of post dialysis and pre-dialysis BUN described above) and 24-h urine output of 400 ml, urine BUN 350 mg/dl. Height is 165 cm, and weight 54 Kg. Calculate her residual kidney function (Krt/V).

Solution:

Step 1: Calculate urea clearance or BUN clearance (urea clearance and BUN clearance is equal)

BUN clearance=BUNurine x Vurine (in ml/minute)/BUNplasma

BUNurine=350 mg/dl

BUNplasma=74 mg/dl

Vurine in ml/minute=400 ml/(24 x 60) = 400/1440 ml/min

BUN clearance = (350/74) x (400/1440) = 1.314 ml/min

Step 2: Calculate Krt/V

Kr (L/week) = Urea clearance (ml/min) X 10.08

Kr=1.314 x 10.08

Kr=13.245 L/week

V = -2.097 + (0.2466 X Weight in Kg) + (0.1069 X Height in cm)

= - 2.097 + (0.2466 x 54) + (0.1069 x 165)

=-2.097+13.3164+17.6385=28.8579 L=approximately 28.86 L

Krt/V=13.245 x 1/28.86=0.4589