Brief Report
Bedside renal ultrasound in the evaluation of suspected ureterolithiasis

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Abstract

Objective

To determine whether ultrasound changes emergency physicians' estimated likelihood of acute ureterolithiasis in patients with flank pain.

Methods

This prospective, observational study enrolled patients awaiting computed tomographic (CT) scan for presumed renal colic. Using a visual analogue scale, treating physicians estimated the likelihood of acute ureterolithiasis based first on clinical findings and urinalysis, then after ultrasound, and finally after CT. A 20% change in estimated likelihood was considered clinically significant. Test characteristics of ultrasound for any ureteral stone and for those greater than or equal to 5 mm in size were determined.

Results

One hundred seven patients were enrolled. Sensitivity, specificity, and negative predictive value of ultrasound for stones observed on CT were 76.3% (95% confidence interval [CI], 59.4%-88.0%), 78.3% (95% CI, 66.4%-86.9%), and 85.7% (95% CI, 74.1%-92.9%) respectively, and for stones >5 mm 90.0% (95% CI, 54.1%-99.5%), 63.9% (95% CI, 53.4%-73.2%), and 98.4% (95% CI, 90.3%-99.9%), respectively. Ultrasound significantly impacted the estimated likelihood of disease in 33 of 107 cases (30.8%, 95% CI, 22.5%-40.6%). Computed tomography further significantly changed physicians' impression of disease in 55 of 107 cases (51.4%, 95% CI, 41.6%-61.1%).

Conclusions

Bedside renal ultrasound had only a limited impact on the physicians' clinical impression of patients with possible ureterolithiasis. The sensitivity of sonographic hydronephrosis was modest for detecting any ureteral stone, but much better for detecting a large stone. Further study is needed to define the precise role ultrasound should play in evaluating patients with suspected ureterolithiasis.

Introduction

Non-contrast computed tomography (CT) scanning of the abdomen and pelvis is accepted as the most accurate diagnostic modality for ureterolithiasis in emergency department (ED) patients [1], [2], [3]. However, CT is time-consuming, costly, and exposes patients to radiation. Bedside renal ultrasound is relatively sensitive and specific for unilateral hydronephrosis, and may be of diagnostic value to emergency physicians evaluating patients with possible ureterolithiasis [4], [5], [6]. Although renal ultrasound is a core component of training in emergency ultrasound [7], emergency physicians do not use this modality as commonly as other applications such as the Focused Assessment with Sonography in Trauma, aortic, and early pregnancy examinations [8]. The reasons for this relative underutilization of ultrasound are unclear but may be due to limited published data on how bedside renal ultrasound might be incorporated into medical decision making. Presently, when sonography is employed in patients with flank pain, the impact of sonographic findings on emergency physicians' impression of disease likelihood is unknown. The purpose of this study was to determine whether ultrasound changes a physician's estimated likelihood of acute ureterolithiasis. In addition, this study sought to examine the test characteristics of ultrasound for ureteral stones and for those likely to require intervention (ie, greater than or equal to 5 mm in size).

Section snippets

Methods

This was a prospective, observational study involving a convenience sample of patients awaiting CT scan for possible ureterolithiasis between October 2006 to September 2008. The study was approved by the institutional review board. The study was conducted in a large, urban, academic ED with an annual census of about 85,000. Patients were eligible for inclusion if the treating physician had ordered a non-contrast CT scan of the abdomen and pelvis to evaluate for ureterolithiasis, but was unaware

Results

One hundred seven patients were enrolled in the study. Mean age was 38 years (SD 14 years); 58.9% were men; 48.6% had a history of prior stones; 75.7% had hematuria. Overall, 35.5% of patients in the study were found to have bladder or ureteral stones on CT. The treating physician who assessed disease likelihood was a resident in 95 cases (88.8%) and an attending in 12 cases (11.2%). The primary investigator was the attending of record for 43.0% of the subjects. Ultrasound changed the estimated

Discussion

Prior studies have demonstrated that sonographic hydronephrosis as judged by emergency physicians correlates relatively well with hydronephrosis on intravenous pyelogram [5] and CT scan [4], [9], and that the degree of sonographic hydronephrosis is related to stone size [6]. The purpose of this investigation was to determine the extent to which this sonographic finding impacts physicians' perceived likelihood of acute ureterolithiasis. Secondarily, our study sought to determine the test

Acknowledgment

The authors wish to thank Pattie Smith, RDMS, for her assistance in enrolling patients in this study and Tina Choudhri, BS, for her assistance with data entry.

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  • Point-of-Care Ultrasound Identifies Urinoma Complicating Simple Renal Colic: A Case Series and Literature Review

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    The assessment of renal colic with POC ultrasound generally centers around the identification of hydronephrosis, with the obstructing ureteral stone also occasionally visualized. The sensitivity of POC ultrasound for identifying findings of renal stone has previously been shown to be about 70–80% (10,15,16). Larger stones may have a slight predilection for increased degrees of hydronephrosis (10,16).

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Presentations: This research was presented as an abstract at ACEP Scientific Assembly in Chicago, Oct. 27-28, 2008.

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