-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