Urinary Tract Infection, Lower - Causes, Symptoms and Treatments

Cystitis and urethritis, the two forms of lower urinary tract infection (UTI), are nearly 10 times more common in women than in men; they affect approximately 10% to 20% of all women at least once. Lower UTI is also a prevalent bacterial disease in children, and girls are most commonly affected.

In men and children, lower UTIs arc frequently related to anatomic or physiologic abnormalities and therefore require extremely close evaluation. UTIs often respond readily to treatment, but recurrence and resistant bacterial flare-up during therapy are possible.

Causes of Urinary Tract Infection, Lower:

Most lower UTIs result from ascending infection by a single gram-negative enteric bacteria, such as Escherichia coli, Klehsiella, Proteus, Enterohacter, Pseudomonas, or Serratia. However, in a patient with neurogenic bladder, an indwelling urinary catheter, or a fistula between the intestine and bladder, lower UTI may result from simultaneous infection with multiple pathogens.

Recent studies suggest that infection results from a breakdown in local defense mechanisms in the bladder that allow bacteria to invade the bladder mucosa and multiply. These bacteria cannot be readily eliminated by normal micturition.

During treatment, bacterial flare-up is generally caused by the microbe's resistance to the prescribed antimicrobial therapy. The presence of even a small number (less than 10,000/ ml) of bacteria in a midstream urine sample obtained during treatment casts doubt on the effectiveness of treatment.

In 99% of patients, recurrent lower UTI results from reinfection by the same microbe or from some new pathogen; in the remaining 1 %, recurrence reflects persistent infection, usually from renal calculi, chronic bacterial prostatitis, or a structural anomaly that may become a source of infection.

The high incidence of lower UTI among women may result from the shortness of the female urethra ( 1 1/4" to 2" [3 to 5 cm]), which predisposes women to infection caused by bacteria from the vagina, perineum, rectum, or a sexual partner.

Men are less vulnerable because their urethras are longer (7 1/4" [19.68 cm]) and their prostatic fluid serves as an antibacterial shield. In both men and women, infection usually ascends from the urethra to the bladder.

Signs and symptoms of Urinary Tract Infection, Lower:

Lower UTI usually produces urgency, frequency, dysuria, cramps or spasms of the bladder, itching, a feeling of warmth during urination, nocturia, and possibly urethral discharge in males. Inflammation of the bladder wall also causes hematuria and fever.

Other common features include low back pain, malaise, nausea, vomiting, abdominal pain or tenderness over the bladder area, chills, and flank pain.

Diagnosis of Urinary Tract Infection, Lower:

Characteristic clinical features and a microscopic urinalysis showing red blood cells and white blood cells greater than 1O/high-power field suggest lower UTI.

A clean, midstream urine specimen revealing a bacterial count of more than 100,000/ml confirms the diagnosis. Lower counts do not necessarily rule out infection, especially if the patient is voiding frequently, because bacteria require 30 to 45 minutes to reproduce in urine.

Careful midstream, clean-catch collection is preferred to catheterization, which can reinfect the bladder with urethral bacteria.

Sensitivity testing determines the appropriate therapeutic antimicrobial agent. Voiding cystoureterography or excretory urography may detect congenital anomalies that predispose the patient to recurrent UTIs.

If patient history and physical examination warrant, a blood test or a stained smear of the discharge rules out a sexually transmitted disease.

Treatments of Urinary Tract Infection, Lower:

Complicated or recurrent UTIs: 14 to 21 days of an antibiotic based on culture and sensitivity.

After 3 days of antibiotic therapy, urine culture should show no microbes.

If the urine is not sterile, bacterial resistance has probably occurred, making the use of a different antimicrobial necessary. Single-dose antibiotic therapy with amoxicillin or co-trimoxazole may be effective in women with acute, noncomplicated UTI. A urine culture taken 1 to 2 weeks later indicates whether the infection has been eradicated.

Recurrent infections due to infected renal calculi, chronic prostatitis, or structural abnormality may necessitate surgery; prostatitis also requires long-term antibiotic therapy. In patients without these predisposing conditions, long-term, low-dosage antibiotic therapy is the treatment of choice.