Question

A 43-year-old Caucasian man with a 20-year history of bipolar disorder presents for the first time with long-term polyuria and polydipsia. He previously took lithium for mood stabilization for 15 years before initiating divalproex sodium therapy. He stopped using lithium because of the polyuria, but he felt that the polyuria never fully subsided. His weight is stable, and he has no other urinary complaints. His blood pressure is 115/80 mmHg and his physical exam is normal. His urinalysis shows no blood, cells, protein, glucose, nitrate, casts, or crystals.

What is the most likely cause of his polyuria?
1 Central diabetes insipidus
2 Nephrogenic diabetes insipidus
3 Polyuria secondary to hyperglycemia
4 Polyuria following acute kidney injury
5 Polyuria secondary to polydipsia

Answer 1

The correct option is 2 Nephrogenic diabetes insipidus.

Step-by-step explanation:

Nephrogenic diabetes insipidus (NDI) occurs when the renal tubule response to vasopressin (ADH) is weakened, resulting in the excretion of large volumes of dilute urine.

As the renal tubules do not respond to vasopressin (antidiuretic hormone) and are unable to reabsorb filtered water back into the body, the kidneys create a high volume of dilute urine in nephrogenic diabetes insipidus.

Nephrogenic diabetes insipidus (NDI) can be inherited or develop as a result of disorders that impede the ability of the kidneys to concentrate.

Therefore, the correct option is 2 Nephrogenic diabetes insipidus.

That is, the most likely cause of his polyuria is nephrogenic diabetes insipidus.