If milk alkali syndrome causes renal vasoconstriction and decreased gfr why is there polyuria, water and sodium loss?

if milk alkali syndrome causes renal vasoconstriction and decreased gfr why is there polyuria, water and sodium loss?

Pathophysiology-Excessive intake of calcium & absorbable alkali
Renal vasoconstriction & decreased GFR
Renal loass of sodium & water, reasorption of bicarbonate

Symptoms- Nausea vomiting,constipation
Polyuria,polydipsia
Neuropsychiatric symptoms

Laboratory finding- Hypercalcemia
Metabolic alkalosis
Acute kidney injury
Suppressed PTH

Treatment Discontinuation of causative agent
Isotonic saline followed by furosemide.