What to know about kidney infections

What to know about kidney infections

A common form of urinary tract infection is kidney infection, also known as renal infection, or pyelonephritis.

Bacteria also invade the urethra or the bladder and spread to one of the kidneys.

Women are most often affected by kidney infection, as are pregnant mothers, children under the age of 2 and people over the age of 60.

An estimated 3 to 4 men in every 10,000 and 15 to 17 in every 10,000 women are affected by kidney infections.

This article will describe the signs of a kidney infection and the diagnosis, prevention , and treatment of it.

Important facts about kidney infections

Here are some key points about kidney infections. More detail and supporting information is in the main article.

  • One of the kidney’s major roles is to remove toxins from the body.
  • Symptoms of kidney infections include diarrhea, nausea, and back pain.
  • Sometimes, a bladder infection may occur at the same time as a kidney infection.
  • In most cases, oral antibiotics can successfully treat kidney infections.


Women, the young, and the elderly are most at risk of kidney infections.
Women, the young, and the elderly are most at risk of kidney infections.

When someone has a kidney infection, it usually progresses fairly quickly – in a day or hours. Kidney-infection signs include:

  • diarrhea
  • nausea
  • uncontrollable shivering
  • vomiting
  • back pain
  • pain in the groin
  • pain in the side
  • often symptoms are worse when the patient urinates

If there is also a corresponding bladder infection, the individual may experience:

  • bloody urine
  • cloudy urine
  • pain or difficulty while urinating, often described as a burning or stinging sensation
  • foul-smelling urine
  • frequent urination
  • inability to urinate fully
  • pain in the lower abdomen


Bacteria entering the urethra and reproducing in the bladder cause a kidney infection, which causes an infection. And then the infection spreads to the kidneys. The bacteria can do this through a variety of ways:

  • Toilet hygiene: After going to the toilet and using toilet paper to clean the anus, there may be contact with the genitals, resulting in an infection getting through and working its way up to the kidneys. The infection could also enter via the anus. Bacteria occupy the colon and eventually cause a kidney infection.
  • Female physiology: Women are more vulnerable to bladder infections and ultimately kidney infections than men, because their urethra is shorter, making it easier for infections to reach parts of the urinary tract more quickly.
  • Urinary catheter: A urinary catheter is a tube that is inserted into the bladder through the urethra to drain out urine. Having a urinary catheter raises the risk of developing a urinary tract infection (UTI). This includes kidney infection.
  • Kidney stones: Individuals with kidney stones have a higher risk of developing kidney infection. Kidney stones are the result of a buildup of dissolved minerals on the inner lining of the kidneys.
  • Enlarged prostate: Males with an enlarged prostate have a higher risk of developing kidney infections.
  • Sexually active females: If sexual intercourse irritates the urethra there may be a higher risk of bacteria getting inside the urinary tract and eventually reaching the kidneys.
  • Weakened immune systems: Some patients with weakened immune systems may have a bacterial or fungal infection on their skin, which eventually gets into the bloodstream and attacks the kidneys.

What is the urinary tract?

Diagram of the urinary system.
Diagram of the urinary system.

The urinary tract consists of:

  • The kidneys: The majority of humans have two kidneys, one on either side of the abdomen. Kidneys clear poisonous substances from the blood.
  • The ureters: Urine passes from the kidneys to the bladder through tubes called ureters. Each kidney has one ureter connecting it to the bladder.
  • The bladder: This is a hollow organ in the lower abdomen that stores urine.
  • The urethra: A tube that carries urine from the bladder to outside the body. In males, the urethra travels down the middle of the penis to an opening at the end. In females, the urethra runs from the bladder to just above the vaginal opening. The urethra in females is shorter than in males.


Kidney infection may be treated either at home or in a hospital; this will depend on a variety of factors, including the severity of symptoms and the general state of health of the patient.

Home treatment involves taking prescription oral antibiotics. After a few days the patient should begin feeling better.

It is important that the person ends the treatment and follows the instructions provided by their doctor.

Consuming plenty of fluids will help prevent fever and dehydration. Recommendations for fluid intake can differ depending upon the form of infection.

If there is some discomfort the doctor can may prescribe an analgesic.

If the person is being treated in hospital and is suffering from dehydration, fluids may be given with a drip. Most hospitalization cases last for longer than 3-7 days.

Subsequent tests of urine and blood will tell the doctor how successful treatment has been.

The following causes are more likely to result in treatment for kidney infection being given in hospital:

  • diabetes
  • serious difficulties urinating
  • cancer and chemotherapy or radiotherapy
  • sickle cell anemia
  • a history of kidney infection
  • HIV
  • a blockage in the kidneys
  • being pregnant
  • severe pain
  • severe vomiting
  • being aged 60 years or older


Oral antibiotics alone are often adequate to treat a kidney infection.
Oral antibiotics alone are often adequate to treat a kidney infection.

Typically, a doctor will monitor the patient’s heart rate , blood pressure, temperature, and respiratory function to determine their overall health status. The doctor will scan for dehydration signs too.

A physical examination will be done, with special focus on the mid and lower back to see whether there is any discomfort, pain or tenderness.

If the patient is a young woman, a pelvic exam can be done by the doctor to determine whether there is any pelvic inflammatory disease (PID). A pregnancy test may be recommended when the female is of childbearing age.

A urine test can determine the presence of a UTI but not its location. A urine test that identifies an infection may also help the doctor make a diagnosis.


There are two types of kidney infection:

  • Uncomplicated kidney infection: The patient is healthy and serious complications are highly unlikely.
  • Complicated kidney infection: The patient is more likely to suffer complications, perhaps because of a pre-existing illness or condition.

If a kidney infection is not treated promptly, there is a risk of serious complications, including:

  • Emphysematous pyelonephritis (EPN): This is a very rare, potentially fatal complication. EPN is a severe infection in which kidney tissues are destroyed rapidly. The bacteria that cause the infection release a toxic gas that accumulates inside the kidney, causing fever, nausea, abdominal pain, vomiting, and confusion.
  • Kidney abscesses: pus accumulates in kidney tissues in abscesses. Symptoms include blood in urine, weight loss, and abdominal pain. Sometimes surgery is needed to drain out the pus.
  • Blood poisoning, or sepsis: Also a rare but possibly life-threatening complication, sepsis leads to bacteria spreading from the kidneys into the bloodstream, resulting in infections in any part of the body, including major organs. It is a medical emergency and patients are usually placed in an intensive care unit (ICU).

When to call a doctor

A kidney infection can develop quickly and lead to serious complications.

Medical help is needed if there is:

  • persistent pain
  • a high temperature
  • a change in urination patterns
  • blood in the urine


A kidney infection is often the result of a pre-existing urinary tract infection. The easiest way to stop contracting a kidney infection is by not having any bacteria in the urethra or bladder.

  • Hydration: Drink plenty of fluids.
  • Urination: Urinate whenever there is an urge. Don’t wait.
  • Sexual intercourse: Urinate after sexual intercourse. Wash the genitals before and after intercourse.
  • Toilet hygiene: After passing stools, wipe the anus from front to back. This lessens the risk of spreading bacteria to the genitals.
  • Fiber: Eat plenty of fiber so that stools come out easily and do not irritate or cause skin lesions. Constipation increases the risk of developing a kidney infection.