Question 28

Choice A reason: Polyuria, excessive urine output, typically leads to potassium loss, causing hypokalemia, not hyperkalemia. In conditions like diabetes insipidus, increased urination reduces serum potassium as the kidneys excrete more fluid and electrolytes. Elevated potassium is more associated with reduced renal excretion, as in kidney failure, not polyuria. Choice B reason: Creatinine levels increase in acute kidney injury due to reduced glomerular filtration, impairing the kidneys’ ability to clear creatinine, a muscle metabolism byproduct. Decreased creatinine levels are rare and may reflect low muscle mass, not kidney injury, making this statement incorrect as it contradicts the pathophysiology of renal impairment. Choice C reason: Specific gravity is increased in hypovolemia, as the kidneys conserve water, producing concentrated urine (high specific gravity, >1.020). Decreased specific gravity occurs in conditions like diabetes insipidus, where dilute urine is produced. This statement is incorrect, as hypovolemia leads to higher, not lower, urine specific gravity. Choice D reason: Blood urea nitrogen (BUN) increases in dehydration due to reduced renal perfusion, causing the kidneys to reabsorb urea to conserve water. This elevates serum BUN levels, often with a normal creatinine, reflecting prerenal azotemia. This statement correctly aligns with the pathophysiology of dehydration’s effect on renal laboratory values.