Sorted By Test Name - Mayo Medical Laboratories

AVP
80344
WESTERN EQUINE ENCEPHALITIS
IgG: or =5% loss in body weight) and assessing the antidiuretic response to exogenous administration of
the AVP at the conclusion of a water deprivation test: -If AVP is low despite elevated serum osmolality,
and the urine osmolality increases significantly after administration of exogenous AVP, the diagnosis is
compatible with central DI. -If stimulated AVP is elevated and the administration of exogenous AVP
results in little or no increase in urine concentration, the patient likely has nephrogenic DI. -Mixed forms
of DI can exist, and both central and peripheral DI may be incomplete, complicating the interpretation of
results. Patients with psychogenic polydipsia will either have a normal response to water deprivation or,
in particular in long-standing cases, will show a pattern suggestive of mild nephrogenic DI due to loss of
concentrating gradient across the nephron as a result of salt-washout by long-standing polydipsia. An
elevated plasma AVP level in a hyponatremic, euvolemic patient might be indicative of SIADH.
Confirmation of euvolemia is critical in such patients, since an elevated AVP level represents a
physiological response to hypovolemia. Seizures, cerebral hemorrhages, cerebral trauma, cerebral tumors,
neurosurgery, electroconvulsive therapy, central nervous system acting drugs, and a variety of conditions
that reduce apparent blood volume or pressure in central vessels (eg, severe low output cardiac failure)
can all result in inappropriate AVP elevations. Depending on the clinical course, these might be short
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