Non-Protein Nitrogen(NPN) Compounds

BUN-to-Creatinine ratio Test Units BUN (Urea) 7–20 mg/dL Urea 20-40 mg/dL Creatinine 0.7-1.2 mg/dL The principle behind this ratio is the fact that both urea (BUN) and creatinine are freely filtered by the glomerulus, however urea reabsorbed by the tubules can be regulated (increased or decreased) whereas creatinine reabsorption remains the same (minimal reabsorption).

The most likely cause is chronic renal disease The most likely cause is chronic renal disease. Supporting data are the essentially BUN/creatinine ratio and the significant elevation of all nonprotein nitrogen (NPN) values. There was no significant improvement when cardiac function improved, further eliminating congestive heart failure as a cause of elevated BUN.

If the levels of acetone and other α-ketoacids were elevated, as might be found in diabetes, the patient’s elevated creatinine levels could have been an erroneous result. α-Ketoacids cause a positive bias when creatinine is measured by a kinetic Jaffe reaction, the most commonly used assay method. However, the normal glucose level and abnormal values for other NPN substances make this unlikely.

Increased uric acid is a result of the significant increase in nuclear breakdown in the presence of a high WBC. The increase is not from renal disease, because BUN and creatinine are normal. Chemotherapy has reduced the WBC to below normal levels, and the patient is taking allopurinol.

It is probably due to decreased intake (patient is unable to eat); a determination of total serum protein and albumin would be helpful.