Question 1
A 34 year old male with bipolar disorder who is on lithium and carbemazepime presents with polydipsia and polyuria, with a serum sodium of 138. His serum osmolality is 285, whilst his urine osmolality is 100. A water deprivation test is undertaken. A 24 hour urine collection reveals a urine volume of 6.8 L. The water deprivation test was completed when the urine osmolality reached 600mOsm. DDAVP was administered however the urine osmolality failed to increment. What is the likely diagnosis?
(A) Nephrogenic Diabetes insipidus
(B) Primary Polydipsia
(C) Central Diabetes Insipidus
(D) Syndrome of Inappropriate ADH secretion
(E) Carbemazepine toxicity
B: During the water deprivation test, the urine osmolality reached its target and thus showed that the patient is able to adequately concentrate urine via ADH release from the posterior pituitary. Patients with diabetes insipidus should not increase their urine osmolality above 300mOsm in the water deprivation test. N Engl J Med 2015; 372:1349-1358
A 34 year old male with bipolar disorder who is on lithium and carbemazepime presents with polydipsia and polyuria, with a serum sodium of 138. His serum osmolality is 285, whilst his urine osmolality is 100. A water deprivation test is undertaken. A 24 hour urine collection reveals a urine volume of 6.8 L. The water deprivation test was completed when the urine osmolality reached 600mOsm. DDAVP was administered however the urine osmolality failed to increment. What is the likely diagnosis?
(A) Nephrogenic Diabetes insipidus
(B) Primary Polydipsia
(C) Central Diabetes Insipidus
(D) Syndrome of Inappropriate ADH secretion
(E) Carbemazepine toxicity
B: During the water deprivation test, the urine osmolality reached its target and thus showed that the patient is able to adequately concentrate urine via ADH release from the posterior pituitary. Patients with diabetes insipidus should not increase their urine osmolality above 300mOsm in the water deprivation test. N Engl J Med 2015; 372:1349-1358