Water deprivation test should never be performed on patients with:

Water deprivation test should never be performed on patients with:

• A. High MCV
• B. Suspected sufficient ADH
• C. Dehydration
• D. Suspected tubular malfunction

Answer: (C)

Water deprivation test measures how well the kidneys concentrate urine and how the body handles ADH, helping distinguish diabetes insipidus from primary polydipsia when a patient has polyuria and thirst. It should be done only when the patient is adequately hydrated and hemodynamically stable, with careful monitoring of weight and electrolytes, because the test relies on a stable hydration status to interpret changes in urine osmolality. In someone who is dehydrated, performing the test is not appropriate. Dehydration already drives ADH release and concentrates the urine; withholding water would worsen fluid and electrolyte imbalance and the results would be unreliable, since the baseline state is already abnormal. The risk of hypernatremia and volume depletion also makes it unsafe. Other scenarios listed do not inherently contraindicate the test, and in fact the test can be used to evaluate suspected DI or differentiate types, whereas dehydration directly interferes with both safety and interpretation.

Water deprivation test measures how well the kidneys concentrate urine and how the body handles ADH, helping distinguish diabetes insipidus from primary polydipsia when a patient has polyuria and thirst. It should be done only when the patient is adequately hydrated and hemodynamically stable, with careful monitoring of weight and electrolytes, because the test relies on a stable hydration status to interpret changes in urine osmolality.

In someone who is dehydrated, performing the test is not appropriate. Dehydration already drives ADH release and concentrates the urine; withholding water would worsen fluid and electrolyte imbalance and the results would be unreliable, since the baseline state is already abnormal. The risk of hypernatremia and volume depletion also makes it unsafe.

Other scenarios listed do not inherently contraindicate the test, and in fact the test can be used to evaluate suspected DI or differentiate types, whereas dehydration directly interferes with both safety and interpretation.