What Is Acute Pyelonephritis?

Acute pyelonephritis is a sudden infection in the kidneys that can occur when bacteria travel backward from the bladder up to the kidneys. It can also occur when bacteria in the bloodstream settle in the kidneys. Symptoms of pain, fever, and chills usually appear suddenly but should resolve after a course of antibiotic treatment.

The kidneys are located on each side of the back of the body, and they serve to make urine and regulate the amount of water in the blood. By controlling levels of water in the blood, the kidneys also regulate blood volume and blood pressure. Waste is filtered from the blood by the kidneys and excreted in the urine. The functional unit of the kidney is the nephron, which is made up of tubules that filter waste from the blood.

Each kidney has a tube, called a ureter, that transports urine from the kidney down to the bladder. Urine then exits the body by leaving the bladder through another tube, the urethra. Bacteria can enter the body through the urethra, and if the bacteria migrate from the bladder and up the ureter, the bacteria can then infect the kidneys.

Normally, as urine leaves the kidneys, it flushes the ureters and prevents any bacteria from accumulating. Any abnormality or constriction of the ureter may allow bacteria to pool in the ureter and infect the kidneys. Pregnancy can also put pressure on the ureter and put the patient at risk of contracting acute pyelonephritis.

Patients who experience sudden back pain, nausea, fever, chills, or pain while urinating should be examined by a physician for acute pyelonephritis. The physician can examine a urine sample under a microscope, looking for bacteria. Bacteria can also be cultured from the urine sample to confirm the diagnosis of acute pyelonephritis. An ultrasound or computed tomography (CT) scan may help the physician determine if there is an obstruction in the urinary tract.

Depending on the severity of the infection or the presence of other symptoms, patients may be prescribed antibiotics to be taken orally at home or they may be hospitalized. In the hospital, antibiotics can be given intravenously for one or two days, then followed by oral antibiotics. The entire course of antibiotic treatment is 14 days. Drinking plenty of fluids may aid in flushing bacteria through the urinary tract. Acute pyelonephritis may recur.