My friend Jean was chagrined to have unwittingly risked her health. “It felt like a barely-there bladder infection, so I took some cranberry extract. The next day, I felt OK, so I forgot about it,” Jean told me. “But on day three, I developed a fever and my back hurt like crazy, so I called my doctor. I wound up in the hospital getting intravenous [IV] antibiotics for a kidney infection that could have caused serious, or even fatal, complications! I’m kicking myself for not checking with my doctor sooner, while the infection was still just in my bladder.”

Jean’s story is not unusual, I heard from kidney specialist Mildred Lam, MD, of Case Western Reserve University School of Medicine. She told me that, in most cases of urinary tract infection (UTI), bacteria get into the urethra (the tube that carries urine out of the body), travel into the bladder and multiply. Called a bladder infection or cystitis, this generally is easily treated with antibiotics.

But sometimes the bacteria travel farther and invade the kidney itself, causing a kidney infection. Possible consequences of this type of UTI include temporary or permanent kidney failure… chronic kidney disease… and potentially life-threatening septicemia if bacteria enter the bloodstream.

Women are more vulnerable to UTIs than men because in women, the urethra and bacteria-laden anus are closer together… and the urethra is shorter, so bacteria don’t have to travel as far to reach the bladder and kidneys. Other risk factors…

  • Being postmenopausal — accompanying hormonal changes can diminish muscle tone in the urinary tract, making it easier for bacteria to invade.
  • Sexual activity, especially with a new partner — perhaps because, over time, a woman develops antibodies to her partner’s bacteria.
  • Diabetes — sugar in the urine promotes bacterial growth.
  • Kidney stones — these provide a place for bacteria to grow and also impede the flow of urine (and therefore bacteria) out of the body.
  • Congenital defects that let urine travel upward from the bladder to the kidney — normally urine only travels downward from kidney to bladder.

Because a kidney infection can quickly become serious, Dr. Lam urged women to be on the lookout for symptoms. Call your doctor today if you notice…

  • Discomfort or burning pain when urinating.
  • Frequent urge to urinate (even if little comes out).
  • Cloudy or blood-tinged urine.
  • Low-grade fever.
  • Mild to moderate pain in the middle of the lower back.

These symptoms suggest a bladder infection. A urine test can confirm the diagnosis. Remember: Prompt treatment — typically a three-to-five-day course of oral antibiotics — helps keep a bladder infection from moving to the kidneys. If you need a pain reliever, your doctor may recommend acetaminophen (Tylenol). “High-dose aspirin, ibuprofen and naproxen carry a small risk for kidney failure,” Dr. Lam cautioned.

When urgent care is needed: See your doctor immediately or go to an urgent care center or emergency department if you have the above symptoms plus any of the following…

  • Severe pain in the “flank” area of the back, at the lower edge of the ribs on the left or right side.
  • Chills and/or fever above 102