System that produces and discharges urine to rid the body of waste products. It consists of the kidneys, which balance electrolytes in blood, retaining and adding needed ones and removing unneeded or dangerous ones for excretion; the ureters, two thin muscular tubes 10–12 in. (25–30 cm) long that move the urine by peristalsis; the hollow, muscular bladder, which receives and stores it; and the urethra, through which it leaves the body. In women the urethra is 1.5 in. (4 cm) long. In men it is longer (since it passes through the penis), about 8 in. (20 cm), and carries semen from the prostate gland as well as urine. Urinary disorders, which can lead to dehydration or edema and to a dangerous buildup of waste and toxic substances, include kidney failure, tumours, and bladder and kidney stones.
Learn more about urinary system with a free trial on Britannica.com.
A urinary tract infection (UTI) is a bacterial infection that affects any part of the urinary tract. Although urine contains a variety of fluids, salts, and waste products, it usually does not have bacteria in it. When bacteria get into the bladder or kidney and multiply in the urine, they cause a UTI. The most common type of UTI is a bladder infection which is also often called cystitis. Another kind of UTI is a kidney infection, known as pyelonephritis, and is much more serious. Although they cause discomfort, urinary tract infections can usually be quickly and easily treated with a short course of antibiotics. Studies have shown that breastfeeding can reduce the risk of UTI's in infants.
Since bacteria can enter the urinary tract through the urethra (an ascending infection), poor toilet habits can predispose to infection, but other factors (pregnancy in women, prostate enlargement in men) are also important and in many cases the initiating event is unclear.
While ascending infections are generally the rule for lower urinary tract infections and cystitis, the same may not necessarily be true for upper urinary tract infections like pyelonephritis which may be hematogenous in origin.
Allergies can be a hidden factor in urinary tract infections. For example, allergies to foods can irritate the bladder wall and increase susceptibility to urinary tract infections. Keep track of your diet and have allergy testing done to help eliminate foods that may be a problem. Urinary tract infections after sexual intercourse can be also be due to an allergy to latex condoms, spermicides, or oral contraceptives. In this case review alternative methods of birth control with your doctor.
Indwelling urinary catheters in women and men who are elderly, over placement of a temporary Prostatic stent can be a major cause of UTI's. Also, people experiencing nervous system disorders, people who are convalescing or unconscious for long periods of time, will have an increased risk of urinary tract infection for a number of reasons. Scrupulous aseptic techniques may decrease these associated risks.
The bladder wall is coated with various mannosylated proteins, such as Tamm-Horsfall proteins (THP), which interfere with the binding of bacteria to the uroepithelium. As binding is an important factor in establishing pathogenicity for these organisms, its disruption results in reduced capacity for invasion of the tissues. Moreover, the unbound bacteria are more easily removed when voiding. The use of urinary catheters (or other physical trauma) may physically disturb this protective lining, thereby allowing bacteria to invade the exposed epithelium.
Elderly individuals, both men and women, are more likely to harbor bacteria in their genitourinary system at any time. These bacteria may be associated with symptoms and thus require treatment with an antibiotic. The presence of bacteria in the urinary tract of older adults, without symptoms or associated consequences, is also a well recognized phenomenon which may not require antibiotics. This is usually referred to as asymptomatic bacteriuria. The overuse of antibiotics in the context of bacteriuria among the elderly is a concerning and controversial issue.
Women are more prone to UTIs than males because in females, the urethra is much shorter and closer to the anus than in males, and they lack the bacteriostatic properties of prostatic secretions. Among the elderly, UTI frequency is in roughly equal proportions in women and men.
A common cause of UTI is an increase in sexual activity, such as vigorous sexual intercourse with a new partner. The term "honeymoon cystitis" has been applied to this phenomenon.
A patient with dysuria (painful voiding) and urinary frequency generally has a spot mid-stream urine sample sent for urinalysis, specifically the presence of nitrites, leukocytes or leukocyte esterase. If there is a high bacterial load without the presence of leukocytes, it is most likely due to contamination. The diagnosis of UTI is confirmed by a urine culture.
If the urine culture is negative:
Most cases of lower urinary tract infections in females are benign and do not need exhaustive laboratory work-ups. However, UTI in young infants must receive some imaging study, typically a retrograde urethrogram, to ascertain the presence/absence of congenital urinary tract anomalies. Males too must be investigated further. Specific methods of investigation include x-ray, Nuclear Medicine, MRI and CAT scan technology.
If the patient has symptoms consistent with pyelonephritis, intravenous antibiotics may be indicated. Regimens vary, usually Aminoglycosides (such as Gentamicin) are used in combination with a beta-lactam, such as Ampicillin or Ceftriaxone. These are continued for 48 hours after fever subsides. The patient may then be discharged home on oral antibiotics for a further 5 days.
If the patient makes a poor response to IV antibiotics (marked by persistent fever, worsening renal function), then imaging is indicated to rule out formation of an abscess either within or around the kidney, or the presence of an obstructing lesion such as a stone or tumor.
As an at-home treatment, increased water-intake, frequent voiding, the avoidance of sugars and sugary foods, drinking unsweetened cranberry juice, taking cranberry supplements, as well as taking vitamin C with the last meal of the day can shorten the time duration of the infection. Sugars and alcohol can feed the bacteria causing the infection, and worsen pain and other symptoms. Vitamin C at night raises the acidity of the urine }, which retards the growth of bacteria in the urinary tract. However, if pain is in the back region (suggesting kidney infection) or if pain persists, if there is fever, or if blood is present in the urine, doctor care is recommended.
In complementary and alternative medicine, D-mannose pills are advocated as a herbal remedy for urinary tract infections. Theoretically, if D-mannose would be present in sufficient concentration in the urine, it could interfere with the adherence of the bacterium E. coli to the epithelial cells lining the urinary tract (similar to the mechanism underlying the effect of cranberry juice). One study showed that it could significantly influence bacteriuria in rats, but there are no studies showing any effect in humans.
Patients with recurrent UTIs may need further investigation. This may include ultrasound scans of the kidneys and bladder or intravenous urography (X-rays of the urological system following intravenous injection of iodinated contrast material). If there is no response to treatments, interstitial cystitis may be a possibility.
During cystitis, uropathogenic Escherichia coli (UPEC) subvert innate defenses by invading superficial umbrella cells and rapidly increasing in numbers to form intracellular bacterial communities (IBCs).