Central diabetes insipidus vs Nephrogenic diabetes insipidus
How to tell Central diabetes insipidus and Nephrogenic diabetes insipidus apart when a board question makes them look alike.
Central DI responds to desmopressin with urine concentration; nephrogenic DI stays dilute because the kidney cannot respond.
Side by side
Low ADH production from hypothalamic or posterior pituitary dysfunction with intact renal responsiveness.
Renal resistance to ADH, classically from lithium, hypercalcemia, hypokalemia, or inherited collecting-duct defects.
Posterior pituitary or hypothalamic injury reduces ADH release.
Collecting ducts cannot respond appropriately to ADH even when hormone is present.
Water deprivation leaves dilute urine; desmopressin increases urine osmolality.
Water deprivation and desmopressin both fail to concentrate urine.
The trap
Both present with polyuria above 3 L per day, dilute urine (urine osmolality below 300), and hypernatremia if water access is limited, so initial labs look identical. The water deprivation test with subsequent desmopressin (DDAVP) is the deciding test: in CENTRAL DI, urine osmolality stays low during dehydration but rises by more than 50 percent after DDAVP (the kidney works fine once given exogenous ADH); in NEPHROGENIC DI, urine osmolality stays low even after DDAVP (the kidney does not respond). Central DI causes include pituitary surgery, head trauma, autoimmune hypophysitis, craniopharyngioma, and infiltrative disease (sarcoidosis, histiocytosis X). Nephrogenic DI causes include lithium (most common drug cause; can persist after discontinuation), hypercalcemia, hypokalemia, and rare hereditary AVPR2 mutation.
Watch it explained
The repair move
Use desmopressin response to decide whether the problem is supply or kidney response.
Try a free question
CoreA patient with prior pituitary surgery has intense thirst, hypernatremia, high serum osmolality, and very dilute urine. Urine osmolality rises substantially after desmopressin. What is the most likely diagnosis?
Show answer and explanation
Answer: A. Central diabetes insipidus. Low ADH supply with preserved renal response causes central diabetes insipidus.
Why the other choices are tempting
- B. Nephrogenic DI would not concentrate urine well after desmopressin.
- C. SIADH causes hyponatremia with concentrated urine.
- D. Primary polydipsia usually has low/normal sodium and improves with water restriction.
- E. Adrenal insufficiency does not cause brisk desmopressin-responsive dilute polyuria.
Flashcards
Tap a card to flip it.
What desmopressin response separates central from nephrogenic DI?
Central DI concentrates urine after desmopressin; nephrogenic DI remains dilute because the kidney cannot respond.
What mechanism causes central diabetes insipidus?
Hypothalamic or posterior pituitary dysfunction lowers ADH release.
Quick answers
What is the fastest way to tell Central diabetes insipidus from Nephrogenic diabetes insipidus?
Central DI responds to desmopressin with urine concentration; nephrogenic DI stays dilute because the kidney cannot respond.
What is the key clue for Central diabetes insipidus?
Low ADH production from hypothalamic or posterior pituitary dysfunction with intact renal responsiveness.
What is the key clue for Nephrogenic diabetes insipidus?
Renal resistance to ADH, classically from lithium, hypercalcemia, hypokalemia, or inherited collecting-duct defects.
What is the common trap with Central diabetes insipidus vs Nephrogenic diabetes insipidus?
Both present with polyuria above 3 L per day, dilute urine (urine osmolality below 300), and hypernatremia if water access is limited, so initial labs look identical. The water deprivation test with subsequent desmopressin (DDAVP) is the deciding test: in CENTRAL DI, urine osmolality stays low during dehydration but rises by more than 50 percent after DDAVP (the kidney works fine once given exogenous ADH); in NEPHROGENIC DI, urine osmolality stays low even after DDAVP (the kidney does not respond). Central DI causes include pituitary surgery, head trauma, autoimmune hypophysitis, craniopharyngioma, and infiltrative disease (sarcoidosis, histiocytosis X). Nephrogenic DI causes include lithium (most common drug cause; can persist after discontinuation), hypercalcemia, hypokalemia, and rare hereditary AVPR2 mutation.