Acute pyelonephritis is an acute infection of the renal parenchyma and pelvis; it is highly prevalent in women and is particularly likely to occur during childhood, nuptials, and pregnancy. The causative organisms mostly enter through the urethra and cause an upstream infection or can be blood-borne. Urinary tract obstruction, vesicoureteral reflux and urinary retention often lead to secondary pyelonephritis. The common causative organisms are gram-negative bacilli. 1. Pathology The kidney is swollen and edematous, with a dull surface color and an unclear boundary between the renal cortex and medulla in the cut surface view, with most small foci of pus visible; the mucosa of the renal pelvis is congested and edematous, with ulcers on the surface. In severe cases, tubular epithelial necrosis is seen, while the glomerulus has few changes. When the septic foci heal, they can form tiny fibrotic scars that are absorbed without impairing renal function. In severe and extensive cases, part of the kidney tissue can be rendered non-functional. If the causative organisms and causes are not completely removed, the disease can turn into chronic pyelonephritis. 2. Clinical manifestations Fever is acute, and the body temperature may rise above 39℃, accompanied by chills, chills, muscle pain, headache, nausea and vomiting, and loss of appetite. The fever pattern is similar to sepsis, which can subside after 1 week and gradually recover after 2 weeks. Low back pain At the onset of the disease, there is often back pain on one or both sides caused by edema and swelling of the renal parenchyma compressing the perirenal membrane. Pressure pain in the renal area and percussion pain at the cribriform angle are obvious. Acute pyelonephritis caused by upstream infection begins with frequent urination, urgency, painful urination, and hematuria. Hemorrhagic infections often begin with high fever, and the symptoms of urinary tract irritation are sometimes not obvious. 3.Laboratory tests Urine examination has white blood cells, red blood cells, bacteria and protein; blood leukocyte count is elevated and neutral white blood cells are rising; lower urinary tract infection is dominated by bladder irritation symptoms with lower abdominal pain and suprapubic pressure, while systemic symptoms such as fever and chills are rarely present. 4.Treatment Systemic treatment Bed rest and fluid infusion to maintain the daily urine volume of more than 1500ml, which is conducive to the excretion of inflammatory substances. Antibacterial drug treatment 3 to 5 days as a course of treatment, treatment should be maintained for a sufficient period of time, when the symptoms subside and the urine culture turns negative, apply a certain period of maintenance amount to prevent recurrence.