Which of the Following Is the Most Common Cause of Acute Pyelonephritis

Ms. Santos, a 45-year-old Female, Presents to the Emergency Department with Complaints of Fever, Chills and Right Flank Pain. She Reports Frequent Urination and a Burning Sensation during Urination. Upon Assessment and the Nurse Notes Tenderness in the Right Costovertebral Angle. the Healthcare Provider Suspects Acute Pyelonephritis