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The Speed of Sound

The Speed of Sound: The Challenge of Renal Colic Made Easier with Ultrasound

Butts, Christine MD

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doi: 10.1097/01.EEM.0000459003.19568.9e
    Grade I hydronephrosis in a 61-year-old woman who presented with bilateral flank pain. Longitudinal sections of the right kidney (left) and left kidney (right) demonstrate mild distortion of the pelvocaliceal structures with dilated fluid-filled calyces.

    Evaluating patients with suspected renal colic is a challenge for emergency physicians. Many of these patients present multiple times a year with flank pain or hematuria, at which point the EP has to decide how often to image the patient, and if so, which modality to use. CT use increased tenfold in evaluating suspected renal colic from the mid-1990s to the mid-2000s. This increase, however, did not demonstrate a change in the proportion of renal stone diagnosis, significant alternate diagnosis, or admission to the hospital. (Acad Emerg Med 2011;18[7]:699.) CT has quickly become the gold standard for evaluating for renal stone, but the amount of radiation in even one CT is substantial.

    This dilemma was recently evaluated in a large, well-powered study in the New England Journal of Medicine. (2014;371[12]:1100.) The authors looked at almost 3,000 patients across multiple facilities to evaluate the outcomes related to the initial imaging choice for these patients in the ED. Patients evaluated as probable renal colic were randomized into three groups for their initial imaging study: abdominal CT, radiology-performed ultrasound, and EP-performed point-of-care ultrasound. Patients were managed after the initial imaging study at the discretion of the treating physician, and further imaging could be ordered as the EP deemed necessary.

    The authors looked at three specific outcomes: high-risk diagnoses with complications that could be related to missed or delayed diagnoses, cumulative radiation exposure from imaging, and total cost. Their ultimate findings were notable because they found no difference in the incidence of high-risk diagnoses among the three groups. Examples of high-risk diagnoses include AAA with rupture, appendicitis with rupture, and bowel ischemia. Most importantly, the authors found that the cumulative radiation dose in the six-month period following initial imaging was significantly lower in the ultrasound groups, which radiology and emergency medicine performed. The study had some limitations, namely that the authors did not standardize the findings seen on ultrasound to diagnose renal colic, but the findings are very promising.

    What does this mean for an EP evaluating the routine patient with flank pain? Initially consider performing a bedside ultrasound to evaluate for hydronephrosis or send the patient to radiology for a renal ultrasound. You will likely save your patients some radiation without sacrificing accuracy in the diagnosis.

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