With significant dehydration in an otherwise healthy patient, which of the following would likely appear on a urinalysis and CBC?

With significant dehydration in an otherwise healthy patient, which of the following would likely appear on a urinalysis and CBC?

• A. Increased urine SG and increased PCV
• B. Increased urine SG and decreased PCV
• C. Decreased urine SG and decreased PCV
• D. Decreased urine SG and increased PCV

Answer: (A)

When a patient is significantly dehydrated, the body loses water but not red blood cells, so the plasma volume drops while the red cell mass remains the same. This hemoconcentration causes the packed cell volume (PCV) to rise. At the same time, the kidneys conserve water, producing more concentrated urine, which shows up as an increased urine specific gravity on urinalysis. So the pattern you’d expect is higher urine specific gravity and a higher PCV. The other patterns—dilute urine or a lower PCV—don’t fit dehydration, which is why they’re not correct.

When a patient is significantly dehydrated, the body loses water but not red blood cells, so the plasma volume drops while the red cell mass remains the same. This hemoconcentration causes the packed cell volume (PCV) to rise. At the same time, the kidneys conserve water, producing more concentrated urine, which shows up as an increased urine specific gravity on urinalysis.

So the pattern you’d expect is higher urine specific gravity and a higher PCV. The other patterns—dilute urine or a lower PCV—don’t fit dehydration, which is why they’re not correct.