BLOOD UREA NITROGEN

BUN

test that measures the amount of urea nitrogen in the blood, which is a waste product formed from protein metabolism in the liver and excreted by the kidneys.

assess kidney function, determine nitrogen balance, and diagnose conditions

Why is the BUN test clinically important?

kidney disease, dehydration, and liver disorders

What conditions can BUN assess?

liver

where is urea synthesized?

ammonia

Urea is synthesized in the liver from?

kidneys

Where is urea primarily excreted?

GI tract, skin

Minor amounts of urea can be eliminated through the —

Dehydration, high-protein diet, hemorrhage, shock, chronic liver disease

Pre-renal causes of increased BUN levels

Acute or chronic renal disease, urinary tract obstruction.

Renal/Postrenal causes of increased BUN levels

Uremia, starvation, muscle wasting

other causes of increased BUN levels

High BUN with normal creatinine

How is BUN used alongside creatinine levels for Prerenal issues?

Both BUN and creatinine are elevated.

How is BUN used alongside creatinine levels for renal/postrenal issues?

Enzymatic UV-Kinetic method

what method is used in the BUN test

Glutamate Dehydrogenase (GLDH)

the enzymatic UV-Kinetic method uses —- to measure urea concentration

Tris buffer, ADP, α-Ketoglutarate, Urease, GLDH

what are the first key reagents in the BUN test

NADH

what is the second key reagent in the BUN test?

Serum or Lithium Heparinized Plasma
24-hour urine diluted with 1/20 normal saline

What specimens can be used for the BUN test?

stable for 24 hours

how long is the sample stable for at room temp?

1 week

how long is the sample stable for at 2-8C?

at least 3 months

how long is the sample stable for at ←20C?

12.9-42.9 mg/dL (2.14-7.14 mmol/L)

what is the normal reference value for BUN for adults 21-60? (serum/plasma)

17.2-49.3 mg/dL (2.86-8.21 mmol/L)

what is the normal reference value for BUN for adults 60-90? (serum/plasma)

21.4-66.5 mg/dL (3.57-11.07 mmol/L)

what is the normal reference value for BUN for adults >90? (serum/plasma)

26-43 g/24h (0.43-0.71 mol/24h)

what is the normal reference value for BUN for Urine?

No effect up to 30 mg/dL

Bilirubin (Unconjugated & Conjugated) effect on BUN Results?

No effect up to 614 mg/dL

Turbidity (Triglycerides) effect on BUN Results?

No effect up to 500 mg/dL

Hemoglobin effect on BUN Results?

No effect up to 20 mg/dL

Ascorbic Acid effect on BUN Results?

No effect up to 1 mg/dL

Methyl Dopa effect on BUN Results?