A 55-year-old man with diabetes and coronary heart disease, who had undergone cardiac catheterization with the use of a radiocontrast agent 2 days ago, is admitted to the emergency department with a flulike syndrome, including chills, nausea, vomiting, abdominal pain, fatigue, and pulmonary congestion. His serum creatinine is elevated, and he has protein in his urine. He is admitted to the intensive care unit with a tentative diagnosis of AKI because of radiocontrast nephropathy.

A.  Radiocontrast agents are thought to exert their effects through decreased renal perfusion and through direct toxic effects on renal tubular structures. Explain how each of these phenomena contributes to the development of AKI.

B.  Explain the elevated serum creatinine, proteinuria, and presence of pulmonary congestion.