Acute pyelonephritis is a bacterial infection that causes kidney inflammation. Pyelonephritis is a kidney infection that develops as a result of an ascending urinary tract infection that travels from the bladder to the kidneys. Acute pyelonephritis affects over 250,000 people each year, resulting in more than 100,000 hospitalizations. Infection with Escherichia coli is the most prevalent cause. Fever, vomiting, abdomen or loin discomfort, and fatigue are all symptoms of acute pyelonephritis, however Fever is the most clinically useful symptom. Escherichia coli is the causative agent in more than 80% of instances of acute pyelonephritis. Staphylococcus saprophyticus, and enterococci are among the other etiologic factors. While Infections caused by Klebsiella, Enterobacter, Clostridium, or Candida are more common in diabetic patients. Acute pyelonephritis can be treated as an outpatient or as an inpatient procedure. Outpatient treatment is available for healthy, young, non-pregnant women with uncomplicated pyelonephritis. The choice of first-line oral antibiotics depends on local antibiotic resistance characteristics, although trimethoprim alone or in combination with sulphamethoxazole, cephalexin, or amoxicillin-clavulanic acid. In this article we will be looking the causes and management of acute pyelonephritis.