Symptoms & Signs
Urethritis: discomfort or pain at the urethral meatus or a burning sensation throughout the urethra with micturition (dysuria).
Cystitis: pain in the midline suprapubic region and/or frequent urination
Hematuria (bloody urine)
Cloudy and foul-smelling urine
High temperature lasting for more than 3 days should be a trigger to get the urine culture done to ascertain whether the fever is due to UTI or not. UTI is very harmful especially in infants since it can cause permanent renal damage.
Nausea and vomiting, accompanied by high fever may indicate a more complicated UTI in which the kidney is infected
Some urinary tract infections are asymptomatic.
Increased confusion and associated falls are common presentations to Emergency Departments for elderly patients with UTI.

Diagnosis
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. Pyelonephritis is ruled out by checking for costovertebral angle tenderness (CVAT). The diagnosis of UTI is confirmed by a urine culture.

If the urine culture is negative:

symptoms of urethritis may point at Chlamydia trachomatis or Neisseria gonorrheae infection.
symptoms of cystitis, may point at interstitial cystitis.
in men, prostatitis may present with dysuria.
In severe infection, characterised by fever, rigors or flank pain, urea and creatinine measurements may be performed to assess whether renal function has been affected.

Causative agents
Common organisms that cause UTIs include: Escherichia coli and Staphylococcus saprophyticus. Less common organisms include Proteus mirabilis, Klebsiella pneumoniae, and Enterococcus spp.

A mnemonic that can be used to remember the bacteria that cause UTIs is SEEK PP (Staph saprophyticus, E. coli, Enterococcus, Klebsiella, Proteus, Pseudomonas).

Prevention
The following are measures that studies suggest may reduce the incidence of urinary tract infections. These may be appropriate for people, especially women, with recurrent infections:

Cleaning the urethral meatus (the opening of the urethra) after intercourse has been shown to be of some benefit; however, whether this is done with an antiseptic or a placebo ointment (an ointment containing no active ingredient) does not appear to matter.[1]
It has been advocated that d-mannose can decrease the incidence of UTI (some of these opinions are referenced in External Links section). A specific type of tannin found only in cranberries and blueberries prevents the adherence of certain pathogens (eg. E. coli) to the epithelium of the urinary bladder. A review by the Cochrane Collaboration of randomized controlled trials states 'some evidence from trials to show cranberries ( and capsules) can prevent recurrent infections in women. Many people in the trials stopped drinking the , suggesting it may not be a popular intervention'[2].
For post-menopausal women, a randomized controlled trial has shown that intravaginal application of topical estrogen cream can prevent recurrent cystitis[3]. In this study, patients in the experimental group applied 0.5 mg of estriol vaginal cream nightly for two weeks followed by twice-weekly applications for eight months.
Often long courses of low dose antibiotics are taken at night to help prevent otherwise unexplained cases of recurring cystitis.
Acupuncture has been shown to be effective in preventing new infections in recurrent cases[4] [5] [6]. One study showed that urinary tract infection occurrence was reduced by 50% for 6 months[7]. However, this study has been criticized for several reasons [8]. Acupuncture appears to reduce the total amount of residual urine in the bladder [citation needed]. All of the studies are by done one research team without independent reproduction of results.
The following measures seem sensible, but have not been studied:[citation needed]

Cleaning genital areas prior to and after sexual intercourse.
For sexually active women, and to a lesser extent men, urinating within 15 minutes of sexual intercourse to allow the flow of urine to expel the bacteria before specialized extensions anchor the bacteria to the walls of the urethra.
Having adequate fluid intake, especially water.
Not resisting the urge to urinate.
Taking showers, not baths, or urinating soon after taking a bath.
Practicing good hygiene, including wiping from the front to the back to avoid contamination of the urinary tract by faecal pathogens.

Epidemiology
UTIs are most common in sexually active women, and increase in diabetics and people with sickle-cell disease or anatomical malformations of the urinary tract.

The use of urinary catheters in both men and women who are elderly, people experiencing nervous system disorders and people who are convalescing or unconscious for long periods of time may result in an increased risk of urinary tract infection for a variety of reasons. Scrupulous aseptic technique may decrease this risk. 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 physcial trauma) may physically disturb this protective lining, thereby allowing bacteria to invade the exposed epithelium.

Women are more prone to UTIs than males because in females, the urethra is much shorter and closer to the anus than in males. The article on vulvovaginal health has some health tips for preventing UTIs.

A common cause of UTI is an increase in sexual activity, such as vigorous sexual intercourse with a new partner. The term "honeymoon cystitis", although somewhat demeaning, has been applied to this phenomenon[1].

Treatment
Most uncomplicated UTIs can be treated with oral antibiotics such as trimethoprim, cephalosporins, Macrodantin, or a fluoroquinolone (e.g. ciprofloxacin, levofloxacin). (Whilst co-trimoxazole was previously used (and continues to be used in the U.S.), the additional benefits of the sulphonamide gave little additional benefit compared to the trimethoprim component alone, but was responsible for its both high incidence of mild allergic reactions and rare but serious complications).

If the patient has symptoms consistent with pyelonephritis, intravenous antibiotics may be indicated.

Recurrent UTIs
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.
References :
http://en.wikipedia.org/wiki/Urinary_tract_infection

Hope this helps.
References :