How Do You Get A Kidney Infection?

A kidney infection happens when bacteria travel up from your bladder into one or both of your kidneys. It is a serious type of urinary tract infection (UTI) that needs medical treatment right away. Most cases start as a bladder infection that was not caught early enough or did not clear up on its own.

What Exactly Is a Kidney Infection?

A kidney infection is called pyelonephritis in medical terms. It is an infection of the kidney tissue itself, not just the tubes that carry urine. When bacteria get into your kidney, your body sends white blood cells to fight them. This causes inflammation, swelling, and pain.

Your kidneys filter waste from your blood and make urine. When they get infected, they cannot work as well. The infection can also spread into your bloodstream if left untreated. That is why kidney infections are more dangerous than regular UTIs.

The CDC reports that about 1 in 30 people with a bladder infection will develop a kidney infection. Women get kidney infections much more often than men because their urethra is shorter, making it easier for bacteria to reach the bladder and then the kidneys.

How Do You Get A Kidney Infection in the First Place?

Bacteria called Escherichia coli (E. coli) cause about 80 to 90 percent of kidney infections. These bacteria normally live in your colon and around your anus. They do not belong in your urinary tract.

The most common route is upward. Bacteria enter your urethra, travel into your bladder, and then move up the ureters into your kidneys. The ureters are the thin tubes that carry urine from each kidney down to the bladder. Normally, urine only flows one way — down. But if bacteria get into the bladder and multiply, they can push back up into the kidneys.

Another way is through your bloodstream. This is much less common, but bacteria from an infection somewhere else in your body, like a skin wound or a dental infection, can travel through your blood and settle in your kidneys. This happens more often in people with weakened immune systems.

Some people report getting a kidney infection after a kidney stone. The stone can block urine flow, letting bacteria grow behind the blockage. Research published in the Journal of Urology has found that any blockage in the urinary tract raises the risk significantly.

Who Is Most at Risk for a Kidney Infection?

Women are at the highest risk. The female urethra is about 1.5 inches long, while a man’s is about 8 inches. Bacteria have a much shorter distance to travel. According to the National Institute of Diabetes and Digestive and Kidney Diseases, women are five times more likely than men to get a kidney infection.

Pregnant women face even higher risk. Hormonal changes during pregnancy relax the ureters, and the growing uterus presses on the bladder. This slows urine flow and gives bacteria more time to multiply. A kidney infection during pregnancy can lead to early labor or low birth weight, so doctors test pregnant women’s urine regularly.

People with diabetes are also at greater risk. High blood sugar weakens the immune system’s ability to fight bacteria. Diabetes can also cause nerve damage that makes it harder to empty the bladder fully. Urine that sits in the bladder is a breeding ground for bacteria.

Anyone with a urinary catheter is at risk. The tube provides a direct path for bacteria to enter the bladder. Hospitals follow strict protocols to prevent this, but the risk never goes away completely.

Men over 50 with an enlarged prostate are more vulnerable. The prostate can press on the urethra and make it hard to empty the bladder. This leftover urine lets bacteria grow.

What Are the Signs That You Have a Kidney Infection?

The symptoms come on fast. You will likely have a high fever, often over 101°F. You may have chills and shaking that feel like the flu. Pain in your lower back or side is very common, usually on one side near where your kidney sits just under your ribs.

You might feel sick to your stomach. Nausea and vomiting happen in about 30 percent of kidney infection cases. You may also feel tired and weak, like your body is fighting something hard.

Urinary symptoms are usually present too. You may feel a burning sensation when you pee. You might need to go more often than normal. Your urine may look cloudy, dark, or have blood in it. Some people notice a strong smell.

Older adults sometimes have different symptoms. Instead of fever and back pain, they may become confused or disoriented. If an elderly family member suddenly seems confused, a kidney infection could be the cause.

One non-obvious sign is that the pain does not go away when you change positions. Kidney pain is steady and deep. Muscle pain usually shifts when you move or stretch. If the pain stays in the same spot no matter how you sit or lie down, that points to a kidney problem.

How Do Doctors Diagnose a Kidney Infection?

Your doctor will start with a urine sample. They test it for white blood cells, red blood cells, and bacteria. A dipstick test can give results in a minute or two. If it shows nitrites or leukocyte esterase, that strongly suggests an infection.

A urine culture is more specific. They send your urine to a lab and let it grow for one to two days. This tells them exactly which bacteria are present and which antibiotics will kill them. This test is important because some bacteria are resistant to common antibiotics.

If the infection is severe or keeps coming back, doctors may order imaging. A CT scan or ultrasound can show kidney stones, blockages, or abscesses that make the infection harder to treat. These scans are not needed for most first-time kidney infections.

Blood tests are common for people who are sick enough to be hospitalized. They check for bacteria in the bloodstream and measure kidney function. A high white blood cell count confirms your body is fighting an infection.

What Is the Standard Treatment for a Kidney Infection?

Antibiotics are the only proven treatment. You cannot treat a kidney infection with cranberry juice, vitamin C, or herbal remedies. Those things may help prevent UTIs in some people, but they will not cure an active kidney infection.

Oral antibiotics work for most people. Common choices include ciprofloxacin, levofloxacin, or trimethoprim-sulfamethoxazole. Your doctor will choose based on local resistance patterns and your medical history. The typical course is 7 to 14 days.

Severe cases require hospitalization. You may need intravenous antibiotics and fluids if you cannot keep pills down, your fever is very high, or you are pregnant. Hospital stays usually last two to four days. Once your fever breaks and you can eat and drink, you go home on oral antibiotics.

Pain relief is part of treatment. Your doctor may recommend acetaminophen for fever and discomfort. Do not take ibuprofen or other NSAIDs without asking your doctor first, because they can affect kidney function in some people.

Drink plenty of water. Staying hydrated helps flush bacteria out of your urinary tract. Aim for six to eight glasses of water per day while you recover. Avoid alcohol and caffeine because they can irritate your bladder and dehydrate you.

What Happens If a Kidney Infection Is Not Treated?

An untreated kidney infection can turn into sepsis. Sepsis is when the infection spills into your bloodstream and your body’s response damages its own organs. It is a medical emergency. The Sepsis Alliance reports that sepsis kills about 270,000 Americans each year, and untreated infections are a major cause.

Kidney damage is another risk. The infection can scar the kidney tissue and permanently reduce how well your kidneys filter blood. This is more likely if you have repeat infections or if treatment is delayed.

An abscess can form inside the kidney. That is a pocket of pus that antibiotics cannot reach easily. Abscesses sometimes need to be drained with a needle or through surgery. This adds weeks to recovery time.

In rare cases, the infection can spread to the tissue around the kidney. This is called a perinephric abscess. It causes severe pain and requires drainage along with antibiotics.

Pregnant women face extra risks. A kidney infection during pregnancy can trigger early labor. It can also lead to low birth weight or infection in the baby after birth. That is why doctors treat even mild UTIs aggressively in pregnant women.

Common Misconceptions About Kidney Infections

One widespread myth is that you can get a kidney infection from being cold or sitting on a cold surface. This is not true. Bacteria cause kidney infections, not temperature. Being cold does not give you an infection.

Another myth is that cranberry juice can cure a kidney infection. Cranberries contain compounds that may help prevent bacteria from sticking to the bladder wall. That is useful for prevention in some people. But once bacteria reach the kidney, cranberry juice has no effect on the infection itself. Research published in the Cochrane Database of Systematic Reviews found no evidence that cranberry products treat active UTIs.

Some people believe that a kidney infection always causes visible blood in the urine. This is not accurate. Many people have only microscopic blood that cannot be seen without a lab test. The absence of visible blood does not rule out a kidney infection.

There is also a belief that kidney infections are contagious. They are not. You cannot catch a kidney infection from someone else. The bacteria that cause them come from your own body, usually from your digestive tract.

How Can You Lower Your Risk of Getting a Kidney Infection?

Treat bladder infections early. That is the single most important thing you can do. If you feel the burning and urgency of a UTI, see a doctor quickly. Do not wait to see if it goes away. Early treatment stops bacteria from reaching your kidneys.

Stay hydrated. Drinking enough water keeps urine flowing and flushes bacteria out of your bladder before they can multiply. Aim for pale yellow urine throughout the day. Dark urine means you need more fluids.

Urinate after sex. This flushes out any bacteria that may have entered the urethra during intercourse. It is a simple habit that studies have found reduces UTI risk in women.

Wipe from front to back after using the toilet. This prevents bacteria from your anus from reaching your urethra. It is especially important for women and girls.

Avoid using spermicidal lubricants or diaphragms if you get frequent UTIs. Spermicides can kill healthy vaginal bacteria that normally keep harmful bacteria in check. Some women find that switching birth control methods reduces their infection rate.

Do not hold your urine for long periods. When you feel the urge to go, use the bathroom. Letting urine sit in your bladder gives bacteria more time to grow and travel upward.

For people with recurrent UTIs, doctors sometimes recommend low-dose antibiotics taken after sex or every day for several months. This is called prophylaxis. It is effective but only used when infections keep coming back despite other measures.

Evidence indicates that probiotics may help some women. Lactobacillus strains can help maintain a healthy balance of bacteria in the vagina and urinary tract. The research is not strong enough to recommend them for everyone, but some women report fewer infections when taking them regularly.