Sunday, October 31, 2010

Lower urinary tract infection

The patient (usually female) complains of urinary frequency and urgency, internal dysuria, and suprapubic pain. There may have been some antecedent trauma (sexual intercourse) to inoculate the bladder, and there may be blood in the urine (hemorrhagic cystitis). Usually, there is no labial irritation, external dysuria or vaginal discharge (which would suggest vaginitis); and no fever, chills, nausea, flank pain, or costovertebral angle tenderness (which would suggest an upper urinary tract infection.)
What to do:

If available in the ED, dip stick for white cells or obtain a urinalysis or Gram stain a sample of urine. The presence of any white cells or bacteria in a clean specimen on microscopic examination confirms the infection. A positive nitrite on dip stick is helpful, but a negative does not rule out infection because many bacteria do not produce nitrites.

If the clinical picture is clearly that of an uncomplicated lower UTI, give trimethoprim 160mg plus sulfamethoxazole 800mg (Bactrim DS or Septra DS) one tablet bid for three days or a 3 day regimen of a quinolone such as ciprofloxacin (Cipro) 250mg bid, norfloxacin (Noroxin) 400mg bid or ofloxacin (Floxin) 200mg bid. Single dose treatment with two TMP/SMX DS tablets is also effective in the young healthy female, but does have a higher early recurrence rate. Instruct the patient to drink plenty of liquids (such as cranberry juice) but do not push fluids when treating children or males.

Extend therapy to 7 days and obtain cultures when treating a patient who is unreliable, pregnant, diabetic, symptomatic more than 5 days, older than 50 or younger than 16. Also extend treatment and obtain cultures on all male patients and those with an indwelling urinary catheter, renal disease, obstructive urinary tract lesions, recurrent infection or other significant medical problems.

If there are no bacteria or few white cells, no hematuria or suprapubic pain, gradual onset over 7-10 days, and a new sexual partner, the dysuria may be caused by a chlamydia or ureaplasma urethritis. Perform a pelvic exam and obtain samples for culture and microscopic examination. Ask the patient about the use of spermicides or douches, which may irritate the periurethral tissue and cause dysuria.

If there is external dysuria, vaginal discharge, odor, itching and no frequency or urgency, then evaluate for vaginitis with a pelvic examination.

If the dysuria is severe, you may also prescribe phenazopyradine (Pyridium) 200mg tid for 2 days only, to act as a surface anesthetic in the bladder. Warn the patient that it will stain her urine (and perhaps clothes) orange.

Arrange for followup in 2 days if the symptoms have not completely resolved. If necessary, urine culture and a longer course of antibiotics can be undertaken then.
What not to do:

Do not undertake expensive urine cultures for every lower urinary tract infection of recent onset in nonpregnant, normally health women with no history of recent UTI or antibiotic use.

Do not follow the single-dose or 3 day regimens for a possible upper urinary tract infection.

Do not rely on gross inspection of the urine sample. Cloudiness is usually caused by crystals and odors result from diet or medication.

Do not require a follow up visit or culture after therapy unless symptoms persist or recur.
Lower UTI or cystitis is a superficial bacterial infection of the bladder or urethra. The majority of these infections involve Escherichia coli, Staphylococcus saprophyticus or enterococci. The urine dip stick is a reasonable screening measure that can direct therapy if results are positive. Under the microscope, in a clean sediment (free of epithelial cells) one white cell per 400x field suggests a significant pyuria, although clinicians accustomed to imperfect samples usually set a threshold of 3-5 WBCs per field. In addition, Trichomonas may be appreciated swimming in the urinary sediment, indicating a different etiology for urinary symptoms or associated vaginitis. In a straightforward lower UTI, urine culture may be reserved for cases which fail to resolve with single-dose or 3 day therapy. In complicated or doubtful cases, however, or with recurrences, a urine culture before initial treatment may be helpful.
 Risk factors for UTI in women include pregnancy, sexual activity, use of diaphragms or spermicides, failure to void post coitally, and history of prior UTI. Healthy women may be expected to suffer a few episodes of lower urinary tract infection in a lifetime without indicating any major structural problem, but recurrences at short intervals suggest inadequate treatment or underlying abnormalities. Young men, however, have longer urethras and far fewer lower UTIs, and probably should be evaluated urologically after just one episode unless they have a risk factor such as an uncircumcised foreskin, HIV infection or homosexual activity and respond to initial treatment. In sexually active men, consider urethritis or prostatitis as the etiology. In men over 50 years old, there is a rapid increase in UTI due to prostate hypertrophy, obstruction and instrumentation.

Valenstein PN, Koepke JA: Unnecessary microscopy in routine urinalysis. Am J Clin Pathol 1984;82:444-448.

Stamm WE, Hooton TM: Management of urinary tract infections in adults. N Eng J Med 1993;329:1328-1334.

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