Acute pyelonephritis is a bacterial infection of the kidneys, which affects 1 to 2% of pregnant women. In most cases, the infection first develops in the lower urinary tract. If not diagnosed and treated properly, the infection may ascend from the urethra and genital area to the bladder, then to one or both kidneys.
Compared to non-pregnant women, pregnant women are more likely to develop pyelonephritis. This is due to physiological changes during pregnancy that can interfere with the flow of urine. Normally, the ureters drain urine from the kidney into the bladder and out of the body through the urethra. But, during pregnancy, the high concentration of the hormone progesterone can inhibit contraction of these drainage ducts. Also, as the uterus becomes enlarged during pregnancy, it can compress the ureters. These changes can lead to problems with proper drainage of the urine from the kidneys, causing the urine to remain stagnant. As a result, bacteria in the bladder, rather than being washed out of the system, may migrate to the kidneys and cause infection. The Escherichia coli (E. Coli) bacterium is the usual culprit. Other bacteria-such as Klebsiella pneumoniae, Proteus species, and staphylococci-can also cause kidney infections. About 75 to 80% of cases of pyelonephritis occur on the right side, 10 to 15% are left-sided, and about 10% are bilateral.
What Are the Symptoms and Consequences of Pyelonephritis?
Typically, the first symptoms of pyelonephritis are a high fever, chills, and pain on both sides of the lower back. In some cases, this infection causes nausea and vomiting. Urinary symptoms are also common, including:
- frequency (the need to urinate often);
- urgency (the need to urinate immediately);
- dysuria (painful urination); and
- hematuria (blood in the urine).
Proper treatment of pyelonephritis may prevent serious problems. But, this infection can lead to a bacterial infection in the bloodstream (sepsis), which can then spread to other parts of the body and cause serious conditions requiring emergency treatment. For example, untreated pyelonephritis can lead to acute respiratory distress as fluid accumulates in the lungs. Pyelonephritis during pregnancy is also a leading cause of preterm labor, which puts the baby at high risk for serious complications and even death.
Like a number of other infections during pregnancy, untreated pyelonephritis can lead to preterm delivery, the leading cause of non-fatal complications and death in newborn babies.
How Is Pyelonephritis Diagnosed?
A urine test can determine whether your symptoms are the result of a kidney infection. By examining a urine sample under a microscope, your doctor can identify whether white blood cells and bacteria are present, both telltale signs of infection. White blood cells casts mean that the kidney has been infected. A definitive diagnosis is made though bacteria cultures of the urine.
How Should Pyelonephritis Be Treated?
As a general rule, if you develop pyelonephritis during pregnancy, you will be hospitalized for treatment. You will be given intravenous antibiotics, probably cephalosporin drugs such as cefazolin (Ancef) or ceftriaxone (Rocephin). After starting antibiotics, approximately 75% of patients improve within 48 hours. By the end of 72 hours, almost 95% of patients will be without fever or other symptoms.
If your symptoms do not improve, it may be that the microorganisms causing the infection are resistant to the antibiotic. If your doctor suspects that the antibiotic is not sufficient to kill the bacteria, gentamicin (Garamycin)-a very strong antibiotic-may be added to your treatment.
Obstruction within the urinary tract is the other main cause of treatment failure. It is typically caused by a kidney stone or physical compression of the ureter by the growing uterus during pregnancy. Urinary tract obstruction is best diagnosed through an x-ray or an ultrasound of your kidneys.
Once your condition begins to improve, you may be allowed to leave the hospital. You will be given oral antibiotics for seven to 10 days. Your doctor will select a specific oral agent based on considerations of effectiveness, toxicity, and expense. Drugs such as trimethoprim-sulfamethoxazole (Septra, Bactrim) or nitrofurantoin monohydrate macrocrystals (Macrobid) are often prescribed.
Approximately 20 to 30% of pregnant patients with pyelonephritis develop recurrent infections later in pregnancy. The most cost-effective way to lower your risk of recurrence is to take a single dose of an antibiotic daily, as a preventive measure. Sulfisoxazole (Gantrisin), 1 g, or nitrofurantoin monohydrate macrocrystals (Macrobid), 100 mg, are appropriate options. (Remember, though, that drug dosages may vary; your doctor will prescribe what is right for you). If you are taking preventive medication, you should also have your urine screened for bacteria each time you see your doctor. Also, be sure to tell your doctor if any symptoms return. If symptoms recur, or if evaluation of your urine reveals the presence of bacteria or white blood cells, you will have another urine culture to determine if re-treatment is necessary.