Pyelonephritis, also known as an upper urinary tract infection, occurs in the majority of cases when bacteria enter the renal pelvis and calices, causing an inflammatory response. This condition is indeed characterized by severe symptoms and an aggressive onset. Patients may suddenly develop a fever, with temperatures even exceeding 39°C, and experience back pain. Some patients may also exhibit clinical signs such as hematuria. The symptoms are indeed severe, and there is a pronounced systemic inflammatory response, leaving patients feeling listless, dizzy, headachy, and lacking appetite. However, the treatment for this disease generally yields good results. After antibiotic treatment, most patients can gradually see symptom relief within 3 to 5 days, and the condition is mostly curable after 10 to 14 days of medication.