The spread of an infection from the kidneys or bladder is the most common cause. The underlying kidney or bladder infection is treated. The sections of the ureter in which nerves are defective may be removed surgically. Pyelonephritis Pyelonephritis is a bacterial infection of one or both kidneys. Escherichia coli, a bacterium that's normally found in the large intestine, causes about 90 percent of kidney infections among people who live in the community but only about 50 percent among hospitalized patients.
Infections usually ascend from the genital area to the bladder.
In a healthy urinary tract, the infection is usually prevented from moving up the ureters into the kidneys by the urine flow washing organisms out and by closure of the ureters at their entrance to the bladder. However, any physical obstruction to the flow of urine, such as a kidney stone or an enlargement of the prostate, or backflow of urine from the bladder into the ureters increases the likelihood of a kidney infection. Infections can also be carried to the kidneys from another part of the body through the bloodstream. For instance, a staphylococcal skin infection can spread to the kidneys through the bloodstream. Other conditions that increase the risk of a kidney infection include pregnancy, diabetes, and conditions that reduce the body's ability to fight infection.