Monday, 12 November 2012

Urinary tract infection case study

A 19-year-old, sexually active woman presents to the emergency room complaining of a 2-day history of urinary frequency, burning, and urgency. She denies vaginal discharge or itching, fever, chills, nausea, vomiting, back pain, abdominal pain, or hematuria. She has no history of UTI or a sexually transmitted disease. She recently began using a diaphragm for birth control, and reports that her last menstrual period occurred 3 weeks ago. She has only one sexual partner, who denies penile discharge or burning on urination. On physical examination, she is noted to be afebrile with a normal blood pressure and pulse. There is no costovertebral angle tenderness. Her abdomen is soft and there is mild suprapubic tenderness in response to palpation. A urinalysis reveals 1+ protein, 2+ leukocytes, and 1+ blood. The urine pH is 5.6. Gram's staining of an unspun urine specimen reveals abundant polymorphonuclear leukocytes and moderate gram-negative rods. A clean-catch urine specimen is sent to the microbiology laboratory for culture. The emergency room physician diagnoses an uncomplicated UTI and prescribes trimethoprim-sulfamethoxazole (TMP-SMX), one double-strength tablet twice a day for 3 days.

Q.  What other therapeutic options would have been appropriate in this patient?

Q. What can this woman do to help prevent recurrent UTIs?

Q. Should this woman's sexual partner be evaluated for UTI?

Q. Was the Gram's staining an important diagnostic test, and in what way did the findings alter the management of this case?

Q. What is the value of knowing the urine pH in this setting?

Q. What other diagnostic or laboratory tests should have been performed?

Q. What would be an appropriate analgesic for a patient with UTI who is experiencing severe urethral discomfort?

Q. What side effects of therapy should this woman know about?

Q. What possible consequences could arise if this woman does not comply with therapy?

Case Discussion

Q. What other therapeutic options would have been appropriate in this patient?

TMP-SMX remains the drug of choice for the empirically based treatment of uncomplicated UTIs. For sulfa-allergic patients, ampicillin, amoxicillin, a first-generation cephalosporin, or a quinolone is the appropriate alternative. Therapy may then be modified on the basis of the urine culture results and the sensitivities of the infecting organism. Enterococci are not susceptible to either TMP-SMX or cephalosporins, which points out the utility of performing urine Gram's staining when deciding on antibiotic therapy. The prevalence of ampicillin-resistant E. coli may be as high as 30% in some communities, and this needs to be considered when selecting an appropriate antibiotic. S. saprophyticus responds to ampicillin, TMP-SMX, and the quinolones. In the past, treatment of lower UTIs for 5 to 7 days was recommended. Short course therapy with agents that achieve high and sustained urinary concentrations (single dose with one or two double-strength TMP/SMX or 3 g of amoxicillin) will usually suffice for uncomplicated infections. Failures of short course therapy are indications that complicating factors requiring more extensive evaluation might be present. In general, single-dose therapy is contraindicated in patients with known anatomic or functional abnormalities, or with immunocompromising diseases such as diabetes mellitus. After single-dose therapy urine cultures should be performed 1 to 2 weeks later, to document the cure. In the event of treatment failure, a longer course of the appropriate antibiotic should be administered and an evaluation of potentially complicating factors should be undertaken. Regardless of the pathogen and the choice of antibiotics, aggressive oral hydration is a reasonable recommendation in the management of an uncomplicated UTI. Although there is no evidence that hydration improves the results of appropriate antimicrobial therapy, it does dilute the bacteria and removes infected urine by frequent bladder emptying.

Q. What can this woman do to help prevent recurrent UTIs?

Some women find that switching to another method of birth control considerably reduces the frequency of recurrent bacterial UTIs. Thorough cleansing of the perineal area before sexual relations may decrease the incidence of postcoital UTI in those prone to UTI; however, most patients find this to be an impractical and not completely effective preventive measure. Choosing another method of birth control may not be necessary for most women if they remember to drink a large glass of water before intercourse and void after intercourse; however, studies have shown that diaphragm usage is an independent risk factor for UTI. Regular antibiotic prophylaxis should be reserved for those patients with a history of multiple recurrent UTIs, or complicated UTI or upper tract infections, or for immunocompromised hosts. The disadvantages of ongoing prophylaxis include the development of drug-related side effects and colonization with multidrug-resistant organisms.

Q. Should this woman's sexual partner be evaluated for UTI?

No. Although lower UTIs in women are associated with sexual activity, this is not a sexually transmitted disease. The infecting organisms are usually endogenous flora. Healthy men without predisposing factors such as urinary tract instrumentation or diabetes mellitus rarely get lower UTIs. Bacterial prostatitis does not put his sexual partner at risk for cystitis.

Q. Was the Gram's staining an important diagnostic test, and in what way did the findings alter the management of this case?

When bacteriuria is found in Gram's-stained, uncentrifuged urine, this is a very specific finding for the diagnosis of UTI. The finding of microscopic bacteriuria corresponds to urine culture colony counts of 10 5 /mL in more than 90% of such specimens. Distinguishing between gram-positive and gram-negative infections can be quite useful in making therapeutic decisions.

Q. What is the value of knowing the urine pH in this setting?

Alkaline urine may be caused by infection with Proteus species, which produce urease. The presence of nonalkaline urine in this patient makes infection with a urea-splitting organism unlikely.

Q. What other diagnostic or laboratory tests should have been performed?

The physical examination and diagnostic studies performed in an emergency room setting should be directed toward elucidating the nature of the patient's chief complaint and history. A pelvic examination would be appropriate if the patient had reported symptoms of increased vaginal discharge, dyspareunia, or exposure to a known sexually transmitted disease in the partner. The indications for performing cultures for sexually transmitted pathogens are similar to those for a pelvic examination. Chlamydia, Ureaplasma, N. gonorrhoeae, or Mycoplasma infection should have been considered in this patient if no organisms were seen on the Gram's-stained urine specimens, or if subsequent routine bacterial cultures grew no organisms. Intravenous pyelography and a renal ultrasound examination should be reserved for when a complicated UTI or upper UTI such as pyelonephritis is suspected. A pregnancy test should be performed in any woman of childbearing age before prescribing an antibiotic that may be contraindicated in pregnancy.

Q. What would be an appropriate analgesic for a patient with UTI who is experiencing severe urethral discomfort?

Phenazopyridine hydrochloride is a urinary tract analgesic agent that exerts a topical analgesic effect on the mucosa of the urinary tract through an unknown mechanism of action. The side effects are minimal, and include the urine acquiring a red or orange color that may stain fabric. It is usually not necessary to prescribe more than a 2-day supply to patients with uncomplicated UTIs who are receiving appropriate antibiotic therapy. Opioid analgesics are relatively contraindicated in UTI because they may cause acute urinary retention.

Q. What side effects of therapy should this woman know about?

Vaginal candidiasis commonly develops after antimicrobial therapy because antibiotics eliminate much of the normal vaginal flora and create an ideal environment for the overgrowth of Candida albicans. Hypersensitivity reactions may occur with any antibiotic; however, TMP-SMX may rarely also be associated with interstitial nephritis, aseptic meningitis, Stevens-Johnson syndrome, or erythema multiforme. A careful history to rule out known drug allergy is important.

Q. What possible consequences could arise if this woman does not comply with therapy?

The consequences of noncompliance with therapy include continuing symptoms, the induction of antibiotic-resistant strains of microorganisms, and, most important, ascending infection leading to acute pyelonephritis or even a perinephric abscess.

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