Pyelonephritis/Kidney infections results when a UTI progresses to involve the upper urinary system (the kidneys and ureters).
The kidneys filter the blood to produce urine. Two tubes called the ureters carry urine from the kidneys down to the bladder. Urine travels from the bladder out of the body through the urethra.
Most cases of pyelonephritis are complications of common bladder infections. Bacteria enter the body from the skin around the urethra. They then travel up the urethra to the bladder.
Sometimes, bacteria escape the bladder and urethra, traveling up the ureters to one or both kidneys.
Pyelonephritis is a potentially serious kidney infection that can spread to the blood, causing severe illness. Fortunately, pyelonephritis is almost always curable with antibiotics.
The urethra is much shorter in women than in men, which is one reason why women are more vulnerable to UTIs and pyelonephritis.