J Yeungnam Med Sci.  2022 Jan;39(1):39-45. 10.12701/yujm.2021.01207.

Clinical investigation on acute pyelonephritis without pyuria: a retrospective observational study

• Song HK
• Shin DH
• Na JU
• Han SK
• Choi PC
• Lee JH

• KMID: 2525026
• DOI: http://doi.org/10.12701/yujm.2021.01207

Abstract

Background
The current guidelines for the diagnosis of acute pyelonephritis (APN) recommend that APN be diagnosed based on the clinical features and the presence of pyuria. However, we observed that some of the patients who are diagnosed with APN do not have characteristic clinical features or pyuria at the initial examination. We performed this study to investigate the characteristics of APN without pyuria.
Methods
A retrospective, cross-sectional study was conducted on 391 patients diagnosed with APN based on clinical and radiologic findings, between 2015 and 2019. The clinical features, laboratory results, and computed tomography (CT) findings were compared between patients with normal white blood cell (WBC) counts and those with abnormal WBC counts (WBC of 0–5/high power field [HPF] vs. >5/HPF) in urine.
Results
More than 50% of patients with APN had no typical urinary tract symptoms and one-third of them had no costovertebral angle (CVA) tenderness. Eighty-eight patients (22.5%) had normal WBC counts (0–5/HPF) on urine microscopy. There was a negative correlation between pyuria (WBC of >5/HPF) and previous antibiotic use (odds ratio, 0.249; 95% confidence interval, 0.140–0.441; p<0.001), and the probability of pyuria was reduced by 75.1% in patients who took antibiotics before visiting the emergency room.
Conclusion
The diagnosis of APN should not be overlooked even if there are no typical clinical features, or urine microscopic examination is normal. If a patient has already taken antibiotics at the time of diagnosis, imaging studies such as CT should be performed more actively, regardless of the urinalysis results.

Keyword

Diagnosis; Emergency medical services; Pyelonephritis; Pyuria; Urinalysis

Figure

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  Fig. 1. Flow diagram of the enrolled patients. APN, acute pyelonephritis; ED, emergency department; CT, computed tomography; DJ, Double J; PCN, percutaneous nephrostomy.

Reference

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