Diabetes insipidus
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Diabetes insipidus
Pratap Sagar Tiwari, MD
Lecturer, NMC
Polyuria
• Polyuria has generally been defined as a urine output exceeding 3 L/day in adults and 2 L/m2 in children.
1. Primary polydipsia
2. Central DI
3. Nephrogenic DI
Primary polydipsia
• Also called psychogenic polydipsia
• Characterized by a primary increase in water intake.
Antidiuretic hormone
• Vasopressin, also known as argininevasopressin (AVP), antidiuretic hormone(ADH), or argipressin, is a neurohypophysialhormone.
• Its two primary functions are to retain waterin the body and to constrict blood vessels.
Central DI
• Central DI (also called neurohypophyseal orneurogenic DI) is associated with deficientsecretion of ADH.
• This condition is most often idiopathic(possibly due to autoimmune injury), or canbe induced by trauma, pituitary surgery, orhypoxic or ischemic encephalopathy.
Clinical manifestation
• Patients with untreated central DI typicallypresent with polyuria, nocturia, and, due tothe initial elevation in serum sodium andosmolality, polydipsia.
• They may also have neurologic symptomsrelated to the underlying neurologic disease.
Nephrogenic DI
• Characterized by normal ADH secretion butvarying degrees of renal resistance to itswater-retaining effect.
• NDI presenting in adults is almost alwaysacquired with chronic lithium use andhypercalcemia .
Workup
• A normal Na is’t helpful in Dx but, if a/w a UO> 600 mosmol/kg, excludes a diagnosis of DI.
• A low Na(<137 meq/L) with a low UO(eg, lessthan one-half the plasma osmolality) is usuallyindicative of water overload due to PP.
• A high-normal Na (>142 meq/L, dt water loss)points toward DI, particularly if the UO is < PO
Water deprivation test
• Free fluids until 0730 hrs on the morning of thetest.
• Attend at 0830 hrs for body weight, plasma andurine osmolality
• Record body weight, urine volume, UO, PO andthirst score on a VAS q 2 hrs for up to 8 hrs
• Stop the test if the patient loses 3% of bodyweight .
• If PO > 300 mOsm/kg and UO < 600 mOsm/kg,then administer DDAVP 2 μg i.m
Water deprivation test
• DI : if PO> 300 mOsm/kg with a UO< 600 mOsm/kg
• CDI :if UO rises by at least 50% after DDAVP
• NDI :if DDAVP does not concentrate the urine
• PP is suggested by low PO at the start of test
Treatment
• The initial AOT is to reduce nocturia, therebyproviding adequate sleep, most often byadministration at bedtime desmopressin, whichis the preferred therapy for CDI.
• Once this is achieved, aim for partial control ofthe diuresis during the day, since completecontrol can lead to retention of water andhyponatremia.
• Other drugs, chlorpropamide, carbamazepine,thiazide diuretics, and nonsteroidalantiinflammatory drugs.
End of slides
References:
• Davidson’s 21st edition.
• Medscape
• Uptodate 21.2
Last slide pic: www.weallhaveuniquebrains.com1st slide pic :http://nurse-practitioners-and-physician-assistants.advanceweb.com/