Snapshot A 30-year-old woman presents to her primary care physician for increased frequency of urinating, thirst, and urinating at night. She was in a car accident about a month ago, where she had head trauma. Since then, she reports that she has noticed this increased frequency of urination. At that time, head imaging had been normal. Her physician decides to conduct a vasopressin challenge. The results show decreased urine volume and increased urine osmolality. Based on these results, she decides to start the patient on desmopressin. (Central diabetes insipidis) Introduction Clinical definition diabetes insipidus (DI) characterized by excess free water loss and dilute urine Central vs Nephrogenic Diabetes Inspidus (DI) Central DI Nephrogenic DI Definition Failure to produce antidiuretic hormone (ADH) Insensitivity or resistance of the kidneys to ADH in the collecting duct Etiology Pituitary tumor, where vasopressin is released Other pituitary injuries autoimmune disease trauma surgery ischemia Drugs lithium demeclocycline amphotericin B Congenital (rare) Electrolyte abnormalities hypercalcemia hypokalemia Pathogenesis ↓ ADH, resulting in increased extracellular fluid osmolarity ↑ ADH Vasopressin (DDAVP) challenge ↓ Urine volume and ↑ urine osmolality No change in urine volume or osmolality Presentation Symptoms polyuria polydipsia nocturia thirst Studies Serum labs ↑ serum osmolarity (central DI) electrolytes hypernatremia Other tests 24-hour urine studies best initial test ↓ urine osmolality ↓ urine sodium ↑ urine volume water deprivation challenge no change in urine osmolality or volume vasopressin challenge central DI ↓ urine volume and > 50% ↑ in urine osmolality with DDVAP nephrogenic DI lack of response to vasopressin Differential Primary polydipsia distinguishing factor hyponatremia after trial of desmopressin decreased urine output with water deprivation test Treatment Lifestyle hydration low sodium diet nephrogenic DI Medical desmopressin (DDAVP) mechanism ADH analog that act on the renal tubular cells to increased water permeability this, in turn, increases water retention indication central DI hydrochlorothiazide mechanism induces mild hypovolemia induces an increase in proximal water and sodium reabsorption indication nephrogenic DI indomethacin mechanism inhibits prostaglandin synthesis prostaglandin synthsis are ADH antagonists indication nephrogenic DI amiloride mechanism epithelial sodium channel inhibitor and is believed to impair lithium entry into the renal pricipal cells indication nephrogenic DI secondary to lithium toxicity Complications Hypernatremia Dehydration
QUESTIONS 1 of 6 1 2 3 4 5 6 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.EC.13.65) A 23-year-old male presents with complaints of polydipsia and frequent, large-volume urination. Laboratory testing does not demonstrate any evidence of diabetes; however, a reduced urine osmolality of 120 mOsm/L is measured. Which of the following findings on a desmopressin test would be most consistent with a diagnosis of central diabetes insipidus? QID: 100366 Type & Select Correct Answer 1 Reduction in urine osmolality to 60 mOsm/L following desmopressin administration 4% (2/47) 2 Reduction in urine osmolality to 110 mOsm/L following desmopressin administration 2% (1/47) 3 Increase in urine osmolality to 130 mOsm/L following desmopressin administration 4% (2/47) 4 Increase in urine osmolality to 400 mOsm/L following desmopressin administration 83% (39/47) 5 No detectable change in urine osmolality following desmopressin administration 4% (2/47) M 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic
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