What is the approximate size of the kidneys?

• A. Approximately size of a fist
• B. Approximately size of a bar of soap
• C. Approximately size of a grapefruit
• D. Approximately size of a walnut

Answer: (A)

The size of the kidneys is best understood as roughly fist-sized. This gives a practical reference point during physical examination and when reviewing imaging: in a healthy dog or cat, you’d expect the kidneys to be about the size of a clenched fist, giving a baseline to judge whether they’re enlarged or reduced. If the kidneys appear larger than a fist, that can point to conditions like hydronephrosis, inflammation, or masses; if they’re smaller, it may indicate atrophy from chronic disease. The other size comparisons—bar of soap, grapefruit, or walnut—don’t align with how the kidneys typically feel or appear in normal small animals, so they’re less useful as a general guide.