Diabetes Insipidus Flashcards
How Diabetes insipidus (DI) manifests clinically ..?
polyuria and polydipsia and
can result from either vasopressin deficiency (central DI) or vasopressin insensitivity at the level of the kidney (nephrogenic DI [NDI])
Extracellular fluid tonicity is regulated almost exclusively by ..?
by water intake and excretion
Extracellular volume is regulated by …?
sodium intake and excretion
Volume homeostasis is largely regulated by ……?
the renin-angiotensin-aldosterone system, with
contributions from both vasopressin and
the natriuretic peptide family
Actions of vasopressin …?
anti diuretic and vascular pressor activity
The half-life of vasopressin in the circulation is..?
5 min
What is pathologic polyuria or polydipsia …?
exceeding 2 L/m2/24 hr
The diagnosis of DI is established if ..?
The serum osmolality is >300 mOsm/kg, and
The urine osmolality is <300 mOsm/kg.
When to do water deprivation test …?
If the patient’s serum osmolality is <300 mOsm/kg (but >270 mOsm/kg) and pathologic polyuria and polydipsia are present
Inference of water deprivation test …?
A water deprivation test is indicated to establish the diagnosis of DI and to differentiate central from nephrogenic causes.
Wolfram syndrome include ..?
DI, diabetes mellitus, optic atrophy, and deafness
The most common primary brain tumors associated with DI ..?
Germinomas and pinealomas
When to suspect germinoma ..?
Quantitative measurement of α-fetoprotein and β-human chorionic gonadotropin, often secreted by germinomas, should be performed in children with idiopathic or unexplained DI, in addition to serial MRI scans
Most common common types of infiltrative disorders causing central DI. ..?
Langerhans cell histiocytosis
lymphocytic hypophysitis
About etiology of Nephrogenic Diabetes Insipidus ..
…?
NDI can result from genetic or acquired causes.
Genetic causes are less common but more severe than acquired forms of NDI
Genetic NDI ..?
Congenital X-linked NDI results from inactivating mutations of the vasopressin V2 receptor, AVPR2.
Congenital autosomal recessive NDI results from defects in the aquaporin-2 gene, AQP2.
An autosomal dominant form of NDI is associated with processing mutations of the aquaporin-2 gene.
Acquired NDI etiology ..?
Hypercalcemia or hypokalemia and is associated with lithium, demeclocycline, foscarnet, clozapine, amphotericin, methicillin, and rifampin
What type of food to consume in DI …?
Patients with both central and NDI should ingest a diet without excessive solute (e.g., sodium chloride) to help decrease urine output when vasopressin action wanes.
Treatment of central DI in older children is best accomplished with …?
DDAVP (desmopressin)
Why nasal desmopressin is contraindicated in childhood enuresis …?
The use of DDAVP nasal spray for childhood enuresis is no longer approved due to its risk of causing hyponatremia
TREATMENT For Congenital NDI ..?
T he main goals are to ensure the intake of adequate calories for growth and to avoid severe dehydration.
Foods with the highest ratio of caloric content to osmotic load (Na <1 mmol/kg/24 hr) should be ingested to maximize growth and to minimize the urine volume required to excrete the solute load
Rationale of thiazides in acquired NDI …?
Thiazides appear to induce a state of mild volume depletion by enhancing sodium excretion at the expense of water and by causing a decrease in the glomerular filtration rate, which results in proximal tubular sodium and water reabsorption
