A nurse is caring for a client with SIADH. Which findings should the nurse expect? (Select all that apply.) (Select All that Apply.)

The syndrome of inappropriate antidiuretic hormone (SIADH) involves excessive, uninhibited release of arginine vasopressin, forcing continuous water reabsorption in the renal collecting ducts. This retention expands intravascular volume, driving a severe dilutional hyponatremia and producing low volumes of highly concentrated urine. The resulting fluid shift causes cerebral edema, manifesting as progressive neurological impairment. A. Increased urine specific gravity: Persistent antidiuretic activity causes maximal water reclamation, leaving the excreted urine highly concentrated with solutes like sodium and urea. This drives the specific gravity well above 1.030. It reflects the kidneys' inability to dilute urine despite systemic fluid excess. B. Hyponatremia: Excess free water retention dilutes the extracellular fluid compartment, causing serum sodium levels to drop below 135 mmol/L. This relative solute deficit occurs because water accumulation outpaces total body sodium levels. It represents the defining laboratory feature of this syndrome. C. Confusion: As extracellular osmolality falls, water moves down its osmotic gradient into brain cells, causing astrocyte swelling and acute encephalopathy. This neuro-cellular edema presents clinically as altered mentation, headache, and progressive lethargy. It signals a critical impact on the central nervous system. D. Decreased urine output: Continuous activation of V2 receptors in the distal nephrons maximizes fluid reabsorption, resulting in oliguria. The kidneys excrete minimal, concentrated fluid despite an expanded intravascular volume. This output pattern is a direct physiological consequence of the hormone excess. E. Hypernatremia: High serum sodium concentrations are caused by massive free water wasting, which is the classic hallmark of diabetes insipidus. In this syndrome, the pathophysiology is entirely opposite, featuring water retention that lowers sodium concentration. Elevated sodium is inconsistent with this condition.