A kidney infection, also known as pyelonephritis, is an inflammation of the renal pelvis and kidneys.
Although the urinary system is designed to keep bacteria out, kidney infection often occurs as a complication of an ascending urinary tract infection that spreads from the bladder to the kidney parenchyma.
Symptoms may be different in children and older adults than in other people where it typically presents as a triad of:
Pyelonephritis can be acute or chronic, simple or complicated, affect one or both kidneys. If not treated properly, the infection can cause lasting damage to the kidneys or spread through the bloodstream and cause a dangerous infection.
It is important to distinguish between cystitis (bladder infection), complicated and uncomplicated pyelonephritis, as the management and condition of the patient depend on this.
The urinary tract consists of two kidneys, two ureters, a bladder and a urethra.
The kidneys are two bean-shaped organs, each the size of a fist. They are located near the middle of the back, just below the rib cage, one on each side of the spine.
The spectrum of kidney infection is broad, ranging from mild disease to septic syndrome. Symptoms can vary depending on a person's age and can include the following:
The classic manifestations of acute pyelonephritis seen in adults are often absent in children, especially newborns and infants:
Elderly patients may present with typical manifestations of pyelonephritis, or they may experience the following:
Although many bacteria and viruses can cause pyelonephritis, the bacterium Escherichia coli is often the cause.
Bacteria that enter the urinary tract through the urethra can multiply and travel to your kidneys. It is the most common cause of kidney infections.
Bacteria can also reach the kidney via the bloodstream (Ex: bacteremia or Staphylococcus aureus endocarditis). Hematogenous spread is less common and usually occurs in patients with chronic diseases and those receiving immunosuppressive therapy.
Metastatic staphylococcal or fungal infections can spread to the kidney from distant foci in bone or skin.
Rarely, kidney infection occurs after kidney surgery.
Factors that increase the risk of developing a kidney infection include: