Pyelonephritis, a kidney infection, is usually caused by Escherichia Coli, a bacteria type that is found in the large intestine. Being more common in women than in men, this infection makes its way from the genital area through the urethra to the bladder, up the ureters and then it reaches the kidneys.
It is known that if a person has any physical obstruction to the flow of urine, like a kidney stone, an enlarged prostate, or the backflow of urine from the bladder into the ureters, it is very likely the risk of pyelonephritis to rise.
The bloodstream can be also a source of infections. If a person has another part of the body infected, the bloodstream can carry the infection to the kidneys.

There are certain categories of people who are more exposed to the risk of developing pyelonephritis. Pregnancy causes the ureters to dilate and reduces the muscle contractions that propel urine down the ureters into the bladder. In this way, the risk of reflux of urine grows. Also a partially obstruct of the normal flow of urine may appear because the enlarged uterus puts pressure on the ureters. The persons with a weakened immune system, or which have diabetes, have a great risk of developing pyelonephritis.

Persons with pyelonephritis might experience painful urination, tightly contraction of the abdomen muscles, one or both kidneys may be enlarged and tender, and cystitis symptoms can appear also. Usually, pyelonephritis starts suddenly, with pain in the lower part of the back on either side, fever, chills, nausea and vomiting, but very often, in children these symptoms are slight and difficult to recognize.

There can appear chronic pyelonephritis in people who have major underlying abnormalities like the reflux of urine from the bladder into the ureters, large kidney stones that persist, or a urinary tract obstruction. The chronic pyelonephritis can have vague symptoms, fever may come and go easily, or it may even not occur, and the pain doesn't cause much sufferance.

If the doctor believes that a patient has pyelonephritis, he will perform some tests, to see if the kidney is infected. A urine specimen will be demanded from the patient, and the doctor will examine that sample to determine which bacteria is present. The doctor will also perform blood tests, to find out if there are bacteria or if elevated white blood cells are present in the blood.
Sometimes, there are necessary some more tests, for example if the patient does not respond to antibiotic treatment within 48 hours, if there is an intense back pain from renal colic, or if, after the treatment is finished, the symptoms return in a short time.
The doctor will perform ultrasound or x-ray studies, and that might reveal structural abnormalities, or kidney stones, or other causes of urinary obstruction.

When the doctor suspects the patient has pyelonephritis, he will demand a urine sample and will perform a blood test, and send the tests to the laboratory. Right away, he will start the treatment with antibiotics, but this treatment might change after the lab results are ready.
If the patient has no nausea or vomiting, no signs of dehydration, fever or chills, the treatment with antibiotics given by mouth might be successful. Otherwise, the patient is treated in hospital, being injected intravenous antibiotics. After 1 ore 2 days, the treatment can be switched to antibiotics given by mouth.
The antibiotic treatment may continue for 2 up to six weeks, to prevent recurrence of the infection. After that, a urine sample is taken, to see if the infection disappeared for good.

It is not known which is the ideal duration of such therapy, but if the infection comes back, medication will continue indefinitely.

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