A urinary tract infection (UTI) is an infection involving the kidneys, ureters, bladder, or urethra. These are the structures that urine passes through before being eliminated from the body.
The kidneys are a pair of small organs that lie on either side of the spine at about waist level. They have several important functions in the body, including removing waste and excess water from the blood and eliminating them as urine.
These functions make them important in the regulation of blood pressure. Kidneys are also very sensitive to changes in blood sugar levels and blood pressure and electrolyte balance. Both diabetes and hypertension can cause damage to these organs.
Two ureters, narrow tubes about 10 inches long, drain urine from each kidney into the bladder.
The bladder is a small saclike organ that collects and stores urine. When the urine reaches a certain level in the bladder, we experience the sensation that we have to void, then the muscle lining the bladder can be voluntarily contracted to expel the urine.
The urethra is a small tube connecting the bladder with the outside of the body. A muscle called the urinary sphincter, located at the junction of the bladder and the urethra, must relax at the same time the bladder contracts to expel urine.
Any part of this system can become infected. As a rule, the farther up in the urinary tract the infection is located, the more serious it is.
The upper urinary tract is composed of the kidneys and ureters. Infection in the upper urinary tract generally affects the kidneys (pyelonephritis), which can cause fever, chills, nausea, vomiting, and other severe symptoms.
The lower urinary tract consists of the bladder and the urethra. Infection in the lower urinary tract can affect the urethra (urethritis) or the bladder (cystitis).
What causes a urinary tract infection?
The urine is normally sterile. An infection occurs when bacteria get into the urine and begin to grow. The infection usually starts at the opening of the urethra where the urine leaves the body and moves upward into the urinary tract.
The culprit in at least 90% of uncomplicated infections is a type of bacteria called Escherichia coli, better known as E. coli. These bacteria normally live in the bowel (colon) and around the anus.
These bacteria can move from the area around the anus to the opening of the urethra. The two most common causes of this are improper wiping and sexual intercourse.
Usually, the act of emptying the bladder (urinating) flushes the bacteria out of the urethra. If there are too many bacteria, urinating may not stop their spread.
The bacteria can travel up the urethra to the bladder, where they can grow and cause an infection.
The infection can spread further as the bacteria move up from the bladder via the ureters.
If they reach the kidney, they can cause a kidney infection (pyelonephritis), which can become a very serious condition if not treated promptly.
Signs and Symptoms of Urinary Tract Infection:
Urinary tract infections don’t always cause signs and symptoms, but when they do they may include:
- A strong, persistent urge to urinate
- A burning sensation when urinating
- Passing frequent, small amounts of urine
- Urine that appears cloudy
- Urine that appears red, bright pink or cola-colored — a sign of blood in the urine
- Strong-smelling urine
- Pelvic pain, in women — especially in the center of the pelvis and around the area of the pubic bone
UTIs may be overlooked or mistaken for other conditions in older adults.
Types of urinary tract infection
Each type of UTI may result in more-specific signs and symptoms, depending on which part of your urinary tract is infected.
Part of urinary tract affected Signs and symptoms:
Kidneys (acute pyelonephritis):
Upper back and side (flank) pain
Shaking and chills
Lower abdomen discomfort
Frequent, painful urination
Blood in urine
Burning with urination