Association of Pyuria and Clinical Characteristics With the Presence of Urinary Tract Infection Among Patients With Acute Nephrolithiasis

Study objective: Pyuria is a useful indicator of urinary tract infection among patients with compatible symptoms; however, its utility has not been adequately investigated among patients with acute nephrolithiasis. Therefore, we examine performance characteristics of pyuria and other clinical and laboratory correlates for urinary tract infection among patients with acute nephrolithiasis. Methods: A single-center prospective observational study examining the performance characteristics of pyuria and other clinical correlates for urinary tract infection was conducted among patients older than 17 years and presenting with acute nephrolithiasis confirmed by computed tomography and for whom urine culture was obtained. Results: Of 360 patients with acute nephrolithiasis, 28 (7.8%) had urinary tract infection, defined as growth of a single uropathogen at greater than or equal to 10(3) colony-forming units/mL. For the presence of urinary tract infection, pyuria level greater than 5 WBCs/high-power field (hpf) had a sensitivity of 86% and specificity of 79%; greater than 20 WBCs/hpf had a sensitivity of 68% and specificity of 93%. In 307 patients who lacked history of fever or measured temperature greater than 37.9 degrees C (100.2 degrees F), pyuria level greater than 5 WBCs/hpf had a sensitivity of 79% and specificity of 81% for urinary tract infection; greater than 20 WBCs/hpf had a sensitivity of 57% and specificity of 94%. Patients with urinary tract infection more often were female; had a history of dysuria, frequent urination, chills, urinary tract infection, or subjective fever; or had measured temperature of greater than 37.9 degrees C (100.2 degrees F). Conclusion: About 8% of patients presenting with acute nephrolithiasis have urinary tract infection, in many without clinical findings of infection, and pyuria has only a moderate accuracy in identifying urinary tract infection in this setting. Clinical features of urinary tract infection, a greater degree of pyuria, and female sex increases the likelihood of infection.