Prospective Evaluation of Predictive Parameters for Urinary Tract Infection in Patients with Acute Renal Colic

Acute renal colic (ARC) is an emergency that can mostly be treated conservatively, but can be life threatening in combination with urinary tract infection (UTI). Assessment for infection includes white blood cell (WBC) count and C-reactive protein (CRP), but these parameters are often unspecifically elevated and might lead to antibiotic over-therapy. In times of increasing antibiotic resistance, however, unnecessary antibiotic therapy should be avoided.

The goal of the study was to investigate the prevalence of UTI proven by urine culture (UC) in patients with ARC and to identify predictive factors in the emergency setting.

We prospectively enrolled 200 consecutive patients with ARC and evaluated blood test results, urinalysis, UC, symptoms suspicious for UTI, and time between symptom onset and admission, as well as body temperature. Logistic regression analyses were performed to identify predictive factors.

There were 196 patients eligible for statistical analysis. UTI proven by positive UC was detected in 26 patients (13%). On multivariate logistic regression analysis, suspicious urinalysis (positive nitrite or bacteria > 20/high-power field [hpf] or WBC > 20/hpf), patient age ≥ 54 years and CRP ≥ 1.5 mg/dL (fivefold increase) were significant predictors for the presence of UTI. Neither elevated WBC count nor typical UTI symptoms were associated with UTI.

Based on our results, a routine antibiotic prophylaxis in patients with ARC does not seem to be appropriate. Patient age and CRP can help to decide if antibiotic treatment might be indicated, even in case of a not clearly suspicious urinalysis.