Diabetes insipidus

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/