Why is SDMA considered a more sensitive marker for GFR than creatinine in senior dogs?

• A. It is influenced by muscle mass and diet
• B. It is not influenced by muscle mass or diet
• C. It is less stable in blood than creatinine
• D. It rises only with severe dehydration

Answer: (B)

The key idea is that SDMA tracks kidney filtration more reliably in aging dogs because it’s not affected much by muscle mass or diet. Creatinine is a byproduct of muscle metabolism, so in senior dogs with less muscle, creatinine can stay low even as kidney function declines. That makes it a less sensitive early marker of reduced GFR. SDMA, on the other hand, is produced at a relatively steady rate and is cleared by the kidneys primarily through filtration, so its level rises as GFR falls regardless of the dog’s muscle mass or dietary protein. This makes SDMA a better early indicator of decreasing kidney function in older dogs. The other statements don’t fit: SDMA is not notably influenced by muscle mass or diet, it isn’t generally less stable in blood than creatinine, and it doesn’t rise only with severe dehydration.