Kidney Infection (Pyelonephritis)

Kidney infection definition and facts
- Kidney infection is one of a number of infections that can involve the urinary tract.
- Infection of the kidney is very common, especially in young females.
- Causes of kidney infection are bacteria that have gained entry to the urinary tract, usually via the anus or vagina.
- Risk factors for kidney infection are pregnancy, sexual intercourse, a history of urinary tract infection, spermicide use, kidney stones, use of urinary catheters, diabetes, and surgery or instrumentation of the urinary tract.
- Kidney infections are not contagious.
- Symptoms of kidney infection are
- fever,
- chills,
- abdominal pain,
- nausea,
- vomiting,
- painful urination, and
- a need to urinate frequently.
- Treatment of kidney infection involves oral or intravenous antibiotics.
- Kidney infections can sometimes be prevented by drinking plenty of fluids, changing urinary catheters frequently, good hygiene practices, and taking preventive antibiotics in certain people at high risk.
- If treated early and adequately, kidney infection generally has a good outcome.

What is the function of the kidneys?
The kidneys have a variety of important functions in the body. These functions include filtering and excreting the waste products from the blood as it circulates through capillaries within the kidneys, regulating blood pressure, maintaining steady levels of electrolytes (for example, calcium, phosphorus, sodium, potassium, and chloride), and contributing to the production of red blood cells.
Where are the kidneys located?
The kidneys are located on either side of the body underneath the diaphragm near the lower back. Each kidney is connected to the bladder in the pelvis by ureters (long tube-like structures) that drain the urine from the kidneys to the bladder. Urine stored in the bladder is excreted from the body through the urethra. Collectively, these structures make up what is called the urinary tract.

What is a kidney infection? Is it the same as a urinary tract infection?
The main components of the urinary tract system are kidneys, ureters, bladder, and urethra. Any part of the urinary system may become infected and this is generally referred to as urinary tract infection (UTI). When a kidney becomes infected, the condition is medically referred to as pyelonephritis. Thus, kidney infection is only one of several types of infections encompassed by the term UTI. The spectrum of UTIs includes:
- Acute uncomplicated cystitis (bladder infection)
- Recurrent cystitis
- Complicated UTI
- Prostatitis (prostate infection)
- Kidney infection (pyelonephritis)
- Catheter-associated UTI (in individuals with indwelling urinary catheters)
A more general classification of urinary tract infection includes:
- Lower urinary tract infection involves the urethra, the bladder, and, in men, the prostate gland.
- Upper urinary tract infection refers to infection of the kidneys.

What are the signs and symptoms of kidney infection?
Some of the common symptoms of a kidney infection include:
- fever,
- nausea,
- vomiting,
- abdominal pain,
- shivering,
- shaking -- chills,
- painful urination (dysuria),
- frequent urination (urinary frequency),
- urge to urinate (urinary urgency),
- flank and low and mid back pain (dull kidney pain), and
- generalized malaise.
Signs of kidney infection on the exam may include:
- fever,
- tenderness on the flanks (costovertebral angle tenderness, referring to tenderness upon tapping gently on the mid-back on the sides), and
- clinical evidence of infection in the urinalysis (laboratory analysis of urine).
In elderly patients and those with weak immune systems, kidney infection may be more severe with these conditions:
- confusion,
- lethargy,
- rapid heart rate,
- low blood pressure, and
- dehydration.

What are the causes of kidney infection?
Urine, similar to other fluids in the body, is normally sterile without any bacterial infection. Therefore, the presence of bacteria in the urine is considered abnormal and may lead to urinary tract infection. Typically, bacteria gain access to the urinary system from outside through the urethra (the drainage tube for urine from the bladder). The bacteria may then ascend in the urinary system and cause kidney infections. Kidney infection (upper UTI) is typically more severe than lower UTI because bacteria may also infect the bloodstream (bacteremia) from the kidneys resulting in a more severe illness.
Bacteria may travel from the rectum or the vagina towards the urethra to gain entry into the urinary system. Other bacteria may enter from the skin. Women are more susceptible to urinary tract infections due to the shorter length of their urethras in comparison to those of men.
Is a kidney infection contagious?
Since kidney infection occurs when bacteria from the genital or anal areas enter the urinary tract, it is typically not contagious.