Central DI vs Nephrogenic DI
How to tell Central DI and Nephrogenic DI apart when a board question makes them look alike.
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Urine osmolality response to desmopressin separates central from nephrogenic diabetes insipidus.
Side by side
Polyuria with dilute urine that concentrates after desmopressin indicates central diabetes insipidus.
Polyuria with dilute urine that does not concentrate after desmopressin indicates nephrogenic diabetes insipidus.
Central DI results from deficient vasopressin production or release from hypothalamic-pituitary axis.
Nephrogenic DI results from renal resistance to vasopressin signaling, often due to lithium, hypercalcemia, or kidney disease.
Urine osmolality remains low after water deprivation but rises by at least about 50% after desmopressin; serum sodium and osmolality are often elevated if free water access is limited.
Urine osmolality remains low after water deprivation with minimal change after desmopressin, often below 10% increase; evaluate for hypercalcemia, hypokalemia, and offending medications such as lithium.
The trap
Assuming all polyuria is uncontrolled diabetes mellitus can delay diagnosis. Persistently dilute urine with high serum osmolality should prompt formal water deprivation and desmopressin testing.
The repair move
Next best step: confirm hypotonic polyuria and serum hyperosmolality, then perform desmopressin response testing to classify subtype. Treat central DI with desmopressin, such as 10 mcg intranasal once or twice daily titrated to symptoms and sodium, while nephrogenic DI is managed by stopping offending drugs, low-solute diet, thiazide diuretic, and often amiloride for lithium-related cases.
Try a free question
CoreA 29-year-old woman has intense thirst and polyuria after pituitary surgery. BP 108/66 mm Hg, HR 96/min, temp 36.7 C. Serum sodium is 149 mEq/L and urine osmolality rises from 140 to 520 mOsm/kg after desmopressin. What is the most likely diagnosis?
Show answer and explanation
Answer: A. Central diabetes insipidus. Marked urine concentration response after desmopressin indicates central DI from ADH deficiency.
Why the other choices are tempting
- B. Nephrogenic DI would show little to no concentration response after desmopressin.
- C. Primary polydipsia usually has low or normal serum sodium rather than hypernatremia.
- D. SIADH causes concentrated urine with hyponatremia, opposite this pattern.
- E. HHS causes hyperglycemia-related osmotic diuresis, not desmopressin-responsive dilute urine.
Flashcards
Tap a card to flip it.
What desmopressin response defines central diabetes insipidus?
A substantial rise in urine osmolality after desmopressin supports central DI.
Which response pattern supports nephrogenic diabetes insipidus?
Minimal or absent urine osmolality increase after desmopressin supports nephrogenic DI.
Quick answers
What is the fastest way to tell Central DI from Nephrogenic DI?
Urine osmolality response to desmopressin separates central from nephrogenic diabetes insipidus.
What is the key clue for Central DI?
Polyuria with dilute urine that concentrates after desmopressin indicates central diabetes insipidus.
What is the key clue for Nephrogenic DI?
Polyuria with dilute urine that does not concentrate after desmopressin indicates nephrogenic diabetes insipidus.
What is the common trap with Central DI vs Nephrogenic DI?
Assuming all polyuria is uncontrolled diabetes mellitus can delay diagnosis. Persistently dilute urine with high serum osmolality should prompt formal water deprivation and desmopressin testing.