Pyuria and Urine Cultures in Patients with Acute Renal Colic
Dorfman M, Chan SB, Hayek K, and Hill C. “Pyuria and Urine Cultures in Patients with Acute Renal Colic.” J Emerg Med. Oct 2016;51(4): 358-264.
It is unknown how frequently patients presenting with renal colic and pyuria have a urinary tract infection versus sterile pyuria. There are no previous studies on the rate of pyuria in renal colic and prior studies on urinary tract infection rates in these patients have not been performed in the emergency department patient. There are no evidence based guidelines about whether or not to treat pyuria in these patients, and we cannot rely on urine culture results as patients are sent home before results are available. The study sought to shed some light on these topics.
This was a retrospective EMR review at 3 different community EDs including patients 18 years and older presenting with renal colic and having a final diagnosis of renal colic or stones. Patients were excluded if they did not have a CT performed to diagnose a stone or if microscopic urinalysis was not performed.
Out of 339 patients included in the study:
6% of patients had some degree of renal obstruction
Hematuria was seen in only 74.9% of cases
Pyuria was seen in 14.2% of cases
Patients with pyuria were more likely to be female (68.8% vs 40.5%), more likely to have a urine culture sent (68.8 vs 41.2%), and more likely to have a positive urine culture (36.4% vs 3.3%)
Of 153 urine cultures sent, 10.5% were positive
Obstruction was associated with increased hematuria but NOT increased pyuria or positive cultures
There was an increased risk of having a positive urine culture with increased pyuria – positive culture rates were approximately 60% when microscopic examination revealed >50 WBC per HPF
There was an increased risk of having a positive urine culture with increased leukocyte esterase level – chances of a positive culture were 77.8% when leukocyte esterase levels were LARGE
There was an increased risk of having a positive urine culture with increased bacteria on microscopic examination – there was a 33.3% chance of positive culture when MANY bacteria were seen on microscopic examination per HPF
This was a more relevant patient population than prior studies (all comers to ED)
Having large leukocyte esterase levels on urinalysis was most predictive of a positive urine culture
The study excluded patients where no CT imaging was performed, which may bias the study population to preferentially include “sicker” patients as CT imaging is not always obtained in what appears to be uncomplicated renal colic
Patients without microscopic UAs were not included and urine culture was not sent in all cases, again likely biasing the results as “sicker” or more symptomatic patients have these studies performed
The outcomes of the study (pyuria, positive urine cultures) were not patient centered – there is no data on whether patients with positive urine cultures had clinical evidence of urinary tract infections or whether they benefited from antibiotic treatment
Author’s conclusion: All patients with pyuria should undergo urine culture.
This study makes me more likely to send a microscopic urinalysis on patients presenting with renal colic and then treat with antibiotics in the setting of finding large leukocyte esterase or many WBC in the urine, given the high prevalence of positive urine cultures in this setting. I do not feel there is enough evidence of benefit to start routinely sending urine cultures on all patients with pyuria in the ED, particularly as follow-up of these results is difficult in the ED population. I will continue to give patients return precautions for clinical signs or symptoms of infection.