Pyelonephritis is an upper urinary tract infection, with over 95% caused by bacterial infections in areas such as the renal pelvis and calyces, leading to inflammation. As a type of bacterial infection, if a patient's urine routine shows leukocytes and there is percussion pain in the renal area, along with fever, these symptoms combined with the urine examination can essentially lead to a diagnosis. However, a definitive diagnosis requires a culture of clean-catch midstream urine. If the bacteria in two consecutive urine cultures exceed 100,000 per milliliter and are the same type, the patient can be clearly diagnosed with pyelonephritis.