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The urinary tract makes and stores urine. The kidneys produce urine by removing waste and water from the blood. The urine travels from the kidneys down two narrow tubes called the ureters. Urine is then stored in a balloon-like container called the bladder. (See figure 1 of male and female urinary systems below.) The bladder is a muscular organ that stores urine until one voids.
While the bladder is filling with urine, the base of the bladder (bladder neck) is closed tightly so that no urine escapes. The bladder muscle contracts to release urine. This causes the bladder neck to open and form a funnel.. The urine flows through this funnel into another tube (called the urethra) and out of the body (figure 2).
Other muscles besides the bladder help to hold urine. These are called “pelvic floor” muscles. They surround the urethra, rectum and, in females, the vagina. While the bladder fills with urine, these pelvic floor muscles begin to contract. When the bladder empties, these muscles relax, letting urine flow freely from the bladder out through the urethra.
Bladder function is controlled by special centres in the brain and spinal cord. While the bladder is filling with urine, these centres keep the bladder muscle relaxed and pelvic floor muscles tense. This hold the urine in the bladder. When the bladder is full and one decides to void, the special centres let the pelvic muscles relax and cause the bladder muscle to contract. This allows for urination to occur.
The special centres receive their instruction from other centres in the brain, even during sleep. When the bladder is full, they relay the urge to void to the brain. If the time and place are appropriate, the brain signals the centres of the spinal cord to allow the bladder to empty (figure 2).
Symptoms of urinary tract infections
A urinary tract infection is an overgrowth of bacteria in the bladder and sometimes in the kidney. The lining of the bladder and urethra become red and irritated just as the inside of the nose or throat does when one has a cold. If the bladder is infected, it is called cystitis. If the kidneys are infected, it is called pyelonephritis. It is important to treat these infections so that the kidneys are not damaged.
The urinary tract is normally sterile (contains no bacteria). A bladder infection occurs when bacteria enter the urethra and travel up to the bladder. Females are more prone to bladder infections than males because the urethra in females is short. In general the urethra does not allow bacteria to get up to the bladder, but this does happen in girls who get urinary infection.
In an infant or young child, the signs of a urinary tract infection may not be clear, especially if the child is too young to talk about how he or she feels. Instead, the child may be irritable, not eat as much as usual, have a fever or loose bowel movements (diarrhea), or just not seem healthy. If the symptoms last more than a day, this may signal a need to see a family doctor.
The family doctor reviews the child’s medical history looking for symptoms of past or present problems. The child is also given a physical exam. A sample of urine is examined in the lab (urinalysis). A sample of urine is also incubated in the lab (urine culture). The organisms that grow from the urine sample are identified and tested to see which antibiotics will kill them. A blood test may also be ordered.
Instructions for collecting a urine specimen (mid-stream catch)
Correct collection of urine is very important. Wash off the genital area several times with a clean washcloth. Have your female child sit on the toilet seat with legs spread widely so that the labia (skin folds of the vagina) don’t touch each other. Encourage your child to urinate into the toilet and then place the clean container directly in line with the stream of urine. Remove it after you have collected a few millilitres but before the child stop urinating. The first or last millilitres of urine that come out of the bladder may be contaminated with bacteria from the skin. In a male child, it is important to gently pull back the foreskin before collecting the sample.
Antibiotics are the primary treatment. A doctor will prescribe an antibiotic to kill bacteria and prevent the spread of infection to the kidneys. The doctor may prescribe an antibiotic before the results of the urine culture are know, or may use the results of the culture help in choosing an antibiotic.
If the child is more seriously ill, dehydrated or not responding to oral antibiotics, hospitalization may be required. A follow-up urine test within one week of completion of the antibiotic may be required.
Recovery depends on the severity of the symptoms when treatment is started. In mild cases, symptoms lessen within the first one to two days. More severe cases require several days before symptoms disappear. If symptoms return soon after treatment is finished, further tests including x-rays may be necessary. The doctor will try to determine whether an underlying cause for the infection is present. A urinary tract infection in a child may be the sign of an abnormal urinary tract.
Young children have the greatest risk for kidney damage from urinary tract infections. such damage may lead to poor kidney function, high blood pressure and other problems. For this reason, it is important that these infections receive prompt treatment and careful checkups.
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