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Kidney Diseases

High BUN/Creatin Ratio for a 3month old

03/23/2011

Question:

My 3 month old daughter had bloodwork done. Her Bun/Creat Ratio was 58 (norm 9-25). Her BUN was normal at 14 and her creatinine serum was also normal at .24. I am concerned that that ratio is more than double the high end of the normal range. Is this something I should bring her to the doc or ER for?

Other abnormals on the bloodwork: Co2 was low at 19 ALT was high at 52 Pyruvic Acid was low at .2

Answer:

It is unclear why she had bloodwork done, as a BUN and creatinine are not usually drawn as a routine in a 3-month-old girl. I assume she had an illness. The serum creatinine is a product of muscle metabolism and is an indication of kidney function. With healthy kidneys, more creatinine is excreted and the serum creatinine is low. A serum Cr of 0.24 at 3 months is excellent. As a child grows, the serum creatinine gradually rises, and is generally 0.9-1.2 in a young adult. The BUN also is an indicator of kidney function, but may rise with dehydration. Consequently, if a child is had vomiting or diarrhea, the BUN/Cr ratio often is elevated, and is not a sign of kidney disease. With dehydration, the serum creatinine also may rise, but not as quickly as the BUN.

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Response by:

Jack S Elder, MD, FACS, FAAP Jack S Elder, MD, FACS, FAAP
Clinical Professor of Urology
School of Medicine
Case Western Reserve University