A 55-year-old man with diabetes and coronary heart disease, who underwent cardiac catheterization with the use of a radiocontrast agent 2 days ago, is admitted to the emergency department with a flu-like 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. Explain the elevated serum creatinine, proteinuria, and presence of pulmonary congestion