-IBIS-1.5.0-
tx
endocrine system
diabetes insipidus
diagnoses
definition and etiology
definition: Excessive excretion of very dilute urine and a marked increase in thirst.
etiology: There are two types of diabetic insipidus (DI):
nephrogenic: a disorder where the renal function is normal except for an inability of the kidneys to concentrate urine because the renal tubules do not respond to antidiuretic hormone (ADH). It is X-linked, so seen only in males.
vasopressin-sensitive: this is either a temporary or chronic condition of the posterior lobe of the pituitary in which there is a deficiency of ADH released, and normal kidney reaction to it when administered in laboratory tests. Causes are either primary/idiopathic or acquired: sarcoidosis, tuberculosis, intra/suprasellar tumors; posthypophysectomy; vascular lesions, infections and histiocytosis.
Damage to the posterior lobe will not produce DI, as the posterior lobe is basically just a storage and release area.
signs and symptoms
vasopressin-sensitive:
The onset is insidious or acute.
Occurs at any age.
Tremendous urination and thirst.
Nocturia.
Signs and symptoms specific to the cause if the disorder is secondary.
nephrogenic:
Same as for vasopressin-sensitive, except the disease typically begins soon after birth. If not recognized and treated promptly, the infant may develop permanent mental retardation from hypernatremia, dehydration, fever, vomiting and convulsions.
lab findings:
Complete water deprivation test:
» Nephrogenic: Dehydration and vasopressin administration do not cause the formation of normal urinary concentrations.
» Urinary concentration increases after the administration of ADH.
blood Na normal or increased
increased chloride
increased urine volume
decreased blood volume
course and prognosis
Treatment for nephrogenic DI is to ensure the patient has an adequate fluid intake, and possibly, thiazide diuretics. Vasopressin-sensitive DI may be treated with ADH, thiazide diuretics or ADH-releasing drugs.
Prognosis depends on the cause.
differential diagnosis
Uncontrolled diabetes mellitus
Psychogenic polydipsia
Osmotic diuresis
footnotes