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Pyuria and Kidney Stones – What Does It Mean

December 9, 2016

Short Attention Span Summary

What does it meeeean?
What does pyuria in the setting of a kidney stone mean?  We see it all the time, and the stone itself causes inflammation. When does it indicate infection?  They found that patients with pyuria, defined as >10 WBC/hpf had positive urine culture 36% of the time; those without pyuria had positive culture in 3%.  The more cells, the greater the risk of positive culture; >50 WBCs = 60% chance of a positive culture.  Also large leukocyte esterase (LE) vs trace was more strongly associated with a positive culture (78% vs 1.6% respectively).

Spoon Feed
Not all patients with a kidney stone and a few WBCs on UA/micro have infection.  But the more WBCs, the greater the risk.  Also large LE on UA means greater risk.  Make sure to get a urine culture in these patients.


J Emerg Med. 2016 Oct;51(4):358-364. doi: 10.1016/j.jemermed.2015.10.043. Epub 2016 Jul 29.

Pyuria and Urine Cultures in Patients with Acute Renal Colic.

Dorfman M1, Chan SB1, Hayek K2, Hill C1.

Author information:

1Emergency Medicine Residency Program, Presence Resurrection Medical Center, Chicago, Illinois.

2Georgetown University Medical School, Washington, District of Columbia.



Renal colic caused by stone(s) is common in the emergency department. Often, urinalysis reveals white blood cells, but it is unknown how frequently pyuria is sterile or infectious.


We sought to determine the incidence of pyuria in patients with renal colic and to correlate the incidence with a positive urine culture.


A 1-year retrospective review of adult patients with renal colic presenting to three community emergency departments was performed. Patients without confirmed renal stone(s) or completed urinalysis were excluded. Hematuria is defined as ≥5 red blood cells per high power field (RBC/HPF) and pyuria as >10 white blood cells per high power field (WBC/HPF). A positive urine culture is defined as >100,000 colony forming units per milliliter. Student’s t-test, chi square, or Fisher’s exact tests were performed as appropriate, with significance set at 0.05.


There were 339 patients who satisfied the inclusion and exclusion criteria, and 14.2% of these patients had associated pyuria. There were 153 (45.1%) urine cultures performed, and 16 (10.5%) were positive. Patients with pyuria were more likely to have a positive urine culture (36.4% vs. 3.3%, respectively; p < 0.001). The percentage of positive urine cultures increased (p < 0.001) with increasing pyuria from 9.1% (10-20 WBC/HPF) to 60.0% (>50 WBC/HPF). Positive cultures also increased (p < 0.001) with increased leukocyte esterase observed on macroscopic samples, from 1.6% (small or less leukocyte esterase) to 77.8% (large-volume leukocyte esterase).


Pyuria was found in 14.2% of patients with renal colic. Patients with pyuria had 36.4% positive cultures compared to 3.3% of patients without pyuria. The degree of pyuria or leukocyte esterase was significantly associated with the risk of a positive culture. Urine cultures are recommended for all patients with renal colic and pyuria.

Copyright © 2016 Elsevier Inc. All rights reserved.

PMID: 27480349 [PubMed – in process]

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