A kidney infection (pyelonephritis) usually occurs when a virus or bacteria travels from your urinary tract to the kidneys. Kidney infections can lead to severe complications if you don’t receive early treatment.
Fortunately, there are many ways to prevent and treat a kidney infection. By contacting your doctor as soon as you notice the symptoms, you can stop bacteria or viruses from causing permanent kidney damage.
Let's look closely at pyelonephritis, its symptoms, treatment, and complications.
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Kidney infection is when a virus or bacteria affects one or both kidneys. Most kidney infections begin with a urinary tract infection (UTI). However, they can also occur if bacteria enter your bloodstream during surgery and travels to one or both of your kidneys.
While kidney infections are rare, they still result in around 100,000 emergency room visits¹ annually in the USA.
Symptoms of a kidney infection usually develop quickly. You can start feeling worse within hours or over a few days. Symptoms include:
Fever (temperature up to 103.1°F)
Nausea and vomiting
Pain in your back, side, or groin area
If your kidney infection is a complication of a UTI, you can also experience such symptoms as:
Pain or burning when urinating
Feeling that you can't empty the bladder fully
Blood in urine
Bad-smelling or cloudy urine
Lower stomach pain
Children younger than 24 months may not have any clear signs of a kidney infection, such as fever or pain. Their key symptoms are poor appetite, vomiting, and diarrhea.
Common risk factors of kidney infections are:
Gender: Women are more likely to develop pyelonephritis² than men are
Current or recent UTI infection (in the past 12 months)
Spinal cord injury
Urinary tract defects
Urinary retention (problem emptying urinary tract)
Weakened immune system
Other issues with your kidneys, such as kidney stones
A study³ of 788 non-pregnant women between 18 and 49 years old demonstrated that risk factors include:
Frequency of sexual intercourse
New sexual partners within the past 12 months
Recent use of spermicides
The risk was also higher if the participant's mother had a history of urinary tract infections.
The most common cause of a kidney infection is gram-negative bacteria, which are highly resistant to drugs, including some antibiotics.
The most common is Escherichia coli (or E. coli). This bacterium usually lives in your bowel. However, it can enter the urinary tract during sex or improper wiping after a bowel movement.
Bacteria can enter your kidneys in two ways:
Through blood (often during surgery)
Through your urinary tract
Even when bacteria enter your urinary tract, your body can successfully flush the intruder out with urine in most cases. However, sometimes bacteria manage to stay and cause an infection. If you don’t receive prompt treatment for the UTI or bladder infection, it travels up the urinary tract and into the kidneys.
To diagnose a kidney infection, your doctor will review your medical and family history and ask questions about your symptoms. Then, they can order several tests:
In most cases, doctors can diagnose the infection with a simple urinalysis. A lab technician looks at your urine sample under a microscope and checks for bacteria and white blood cells that fight it.
Your doctor may order a urine culture test to determine which bacteria are responsible for an infection. This can determine the best course of treatment.
Your doctor may order additional imaging tests, such as a CT or a kidney ultrasound, to check for blockage or collections. This helps your doctor adjust the treatment to prevent complications.
Another imaging test is a voiding cystourethrogram (VCUG). It's an x-ray of your bladder and urethra with contrast dye that can show if any additional problems are causing your infection.
The most common and effective treatment for a kidney infection is antibiotics. In most cases, you can do it at home. However, if your condition is severe, you may need IV antibiotics in the hospital.
Your doctor will prescribe antibiotics for up to two weeks. While you may feel better in just a few days, you must take the full treatment. This reduces the risk of the infection returning or becoming antibiotic-resistant. Six weeks after your treatment, your doctor will order urine tests to check the infection has gone.
An untreated kidney infection could cause serious complications, including:
Kidney vein thrombosis (a blood clot in the renal vein)
Acute kidney failure
Without treatment, you can die from a kidney infection. You must contact your doctor as soon as you notice any symptoms.
If you have these sepsis symptoms, seek urgent medical care as it can be life-threatening:
A high fever or low body temperature causing chills, shivering, or clammy skin
Severe breathlessness or fast breathing
A fast heartbeat
A change in your mental state, like disorientation or confusion
Severe muscle pain
Nausea, vomiting, or diarrhea
Feeling dizzy or faint
Every year, kidney infections affect thousands of Americans. With the correct treatment, these infections can go away within days. However, a lack of proper treatment could cause severe complications, including kidney failure, sepsis, or even death.
If you suspect a UTI or a kidney infection, contact your doctor as soon as possible.
To prevent a UTI, you must empty your bladder, drink enough water, urinate after sex, and practice good genital hygiene. By preventing a UTI, you can stop a kidney infection.
Definition & facts of kidney infection (Pyelonephritis) | NIH: National Institute of Diabetes and Digestive and Kidney Diseases
Acute pyelonephritis | NIH: National Library of Medicine
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