Q: Why intravenous diuretics are preferred over oral diuretics till patient resolves clinical significant edema or anasarca?


Answer: Patients with high degree of edema may also have mucosal edema and consequently decrease intestinal perfusion as well as reduced intestinal motility. Once edema is reduce enough, IV diuretic can be changed to PO form.


Reference: 

Krämer BK, Schweda F, Riegger GA. Diuretic treatment and diuretic resistance in heart failure. Am J Med 1999; 106:90.