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Several symptoms and their combinations significantly increase the risk of urinary infections and may be used to determine the pre-test probability for disease thus informing the need to test and individual.
In children several large studies have looked at the risk of UTI based on symptoms. Likelihood ratios have been establish to predict the diagnosis:
In young to middle aged women the likelihood of UTI with any urinary symptom (dysuria, frequency, urgency, suprapubic pain, or hematuria) exceeds 50 percent. That rises to 90 percent if they have dysuria and frequency without vaginal discharge.
A UTI is the systemic response to a bacterial infection in the urine with pyruira representing the immune response measurable on urinalysis. Pyuria is interpreted as nitrite OR leukocyte esterase AND microscopy showing bacteria or > 10 WBC / hpf in the setting of a clinical syndrome consistent with UTI. With a UA positive for nitrate or leukacyte esterase the sensitivity is 75 percent and specificity of 82 percent. However, a negative UA should not be used to definitely rule out the diagnosis of UTI in the setting of high clinical suspicion even if both tests are negative. Of note, the use of bladder analgesics (phenazopyridine) ingestion of beets (14 percent of patients may develop beeturia) may cause false negatives in urine dipsticks.
In order to definitively diagnose a UTI there must be a urinalysis that suggests infection (pyuria and/or bacteriuria) AND one of the following
These cultures should consist of a single predominant organism to be considered positive.
Because the majority of patients with an uncomplicated urinary tract infection are infected with well described pathogens, urine culture is not universally required. However, patients with pyelonephritis, recurrent UTI and younger children are at higher risk of infection with atypical or resistant organisms. All patients with these diagnoses should have a urine culture obtained.
In uncomplicated cystitis the most common causative pathogen is E. coli accounting for more than 90 percent of infections. There have been reported increases in E coli resistance to trimethoprim-sulfamethoxazole (TMP-SMX), amoxicillin-clavulanate, and first-generation cephalosporins however these are dependent on local resistance patterns. Second and third-generation cephalosporins have been shown to be highly active against E. coli and other gram-negative organisms, but may have limited activity against Enterococcus. Despite its history of resistance, Nitrofurantoin has been shown to have improved resistance patterns in many parts of the world and may be considered a first line therapy for uncomplicated cystitis.
Overall, no antibiotic is currently the ideal therapy for uncomplicated cystitis and local antibiograms should steer the provider to the optimal therapy.
Although most uncomplicated urinary tract infections respond to therapy within 48 hours, patients may have decreased discomfort with the use of urinary analgesics such as phenazopyridine. These medications are oral and over the counter making it easy for the patient to source (although patients have been shown to commonly misuse this medication and only few RCTs have looked at these medications). Patients should be told not to chronically use this medication as it may mask recurrent UTI symptoms and has been associated with rare, but severe side effects if used inappropriately.
Outpatient therapy for uncomplicated pyelonephritis may be efficacious. Nitrofurantoin, fosfomycin and pivmecillinam should be avoided in pylenonephritis as it does not achieve adequate concentrations in renal tissues. Fluroquinolones have been the mainstay of outpatient empirical treatment of acute uncomplicated pyelonephritis. However, increasing resistance has put into question their efficacy. Oral third-generation cephalosporins have good activity against the majority of pathogens causing pyelonephritis and may be considered first line therapy for pyelonephritis. In all cases, referral to local antibiograms will provide the best match of antimicrobial to bacterial resistance patterns.