Inappropriate ADH secretion is characterised by the following except:
Answer is A (Hypo-osmolar urine): SIADH is characterized by increased vasopressin release leading to increased absorption of water producing a concentrated or hyperosmolar urine. SIADH The term SIADH is applied to conditions with vasopressin excess. Vasopressin excess is termed inappropriate as this increase occurs despite decreased plasma osmolality. Increased vasopressin acts on renal tubules, resulting in increased absorption of water (increased total body water), a concentrated urineQ and decreasing serum osmolality and hyponatremia Q. Edema does not occur despite increased total body water Q (due to unknown reasons) - Clinical EuvolemiaQ. SIADH should be suspected in patients who have hyponatremia and concentrated urine (osmolality > 300 mmol/kg) in the absence of edema, ohostatic hypotension and features of dehydration. Diagnosis is suppoed by finding of blood urea nitrogen, serum uric acid, creatinine, etc. in low normal or subnormal range Q (as can be expected from hypervolumia). Increased action of ADH causes increased reabsorption of water, and resulting expanded fluid volume & water intoxication, and this also explains fall in conc. of serum electrolytes such as Mg2+.
Hypo-osmolar urine
Water intoxication
Expanded fluid volume
Hypomagnesemia