Morning Report: October 25, 2010

Board Review Today!

12:00Topic: Genetics

Diabetes InsipidusPolydipsia, polyuria, dilute urine,Hypernatremia, dehydration

Diabetes InsipidusCentral or Neurogenic DI

Destruction of posterior pituitary (tumors/trauma) Deficiency of vasopressin

Nephrogenic DIRenal tubular resistance to vasopressinIntrinsic receptor defectMedications

Compulsive Water DrinkerPhysiologic inhibition of vasopressin

secretionFemale PredominanceUsually presents in adulthood

May be seen in adolescence>10% of patients with schizophrenia

Clinical PresentationInfants:

Poor feeding, FTTIrritability, seizures

hypernatremia, dehydrationVomiting after feedsDiapers “dripping wet”Less severe in breast fed babies (solute load)Inquire about family history

Clinical PresentationOlder Children:

Polyuria, polydipsia with normal glucose Hypernatremia

Neurologic deficits or precocious puberty Neurogenic DI

Consider obstructive uropathyMedicationsSystemic disorders

Laboratory TestsCompulsive water drinker

Low serum osmolality coupled with hypo-osmolar urine

Vasopressin deficiency/insensitivityHigh serum osmolality

In setting of normal serum glucose and ureacoupled with hypo-osmolar urine

Water Deprivation TestFollow specific protocol

close monitoringDiagnostic criteria of DI (short deprivation)

Plasma elevation >10mOsm/kg over baselineUrine SpG remains <1.010

DDAVP ChallengeIf urine osm increased > 450mOsm/kgEstablishes central DI

If urine osm remains < 200 mOsm/kgLikely nephrogenic DI

If urine osm incresed > 750 mOsm/kgLikely compulsive water drinker

DDAVP Intranasally

MRIVisualizes:

Anterior and posterior pituitaryPituitary stalk

Possible pathologySuprasellar massPituitary cystHypoplasiaEctopic pituitary

ManagementCentral DI

Intranasal DDAVPOral repletion of waterIf IV fluids used

No more than 3% dextrose Avoid worsening hyperosmolality Avoid glucosuria

ManagementNephrogenic DI

Low-Osmolar, low Na dietHuman milk in infancyThiazide diuretic

Increases Na lossNSAIDS may have benefit

Use only if other methods fail

PrognosisConsider genetic testing/counselingBehavioral problems

Short attention span, hyperactivity, learning delays ? Exacerbated by frequent trips to bathroom, water

source ?Nonobstructive functional hydronephrosis

May be transientCaution when pt cannot readily access water