Lower Urinary tract infection

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

Pathophysiology
Most lower UTIs result from ascending infection by a single gram-negative enteric bacterium, such as Escherichia coli, Klebsiella, Proteus, Enterobacter, 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.
Infection may result 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.
The risk of cystitis is higher when the bladder or urethra becomes blocked and urine flow stops. It can occur when instruments are inserted into the urinary tract during procedures such as catheterization or cystoscopy. Other risks include pregnancy, diabetes, and a history of analgesic or reflux nephropathy. The elderly are at increased risk for developing UTIs due to incomplete emptying of the bladder; this is associated with conditions such as benign prostatic hyperplasia (BPH), prostatitis, and urethral strictures. Also, lack of adequate fluids, bowel incontinence, immobility or decreased mobility, indwelling urinary catheters, and placement in a nursing home all place the person at risk for developing an infection.

Bacterial flare-up
During treatment, bacterial flare-up is generally caused by the pathogenic organism’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 treatment’s effectiveness.

Recurrent UTI
In 99% of patients, recurrent lower UTI results from reinfection by the same organism 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.

Clinical features
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
Characteristic clinical features and a microscopic urinalysis showing red blood cells and white blood cells greater than 10/high-power field suggest lower UTI.
A clean-catch, 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.

Management
Appropriate antimicrobials are the treatment of choice for most initial lower UTIs. A 7- to 10-day course of antibiotic therapy is standard, but recent studies suggest that a single dose of an antibiotic or a 3- to 5-day antibiotic regimen may be sufficient to render the urine sterile. After 3 days of antibiotic therapy, urine culture should show no organisms.
If the urine isn’t 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.