Brief ReportCan the degree of hydronephrosis on ultrasound predict kidney stone size?☆
Introduction
Symptomatic renal colic is a common complaint presenting to the emergency department (ED). An estimated 5% to 15% of the population will have a kidney stone during their lifetime with an ED use rate of 126 to 226 per 100 000 visits [1], [2]. Diagnosis of renal colic is often made solely on the basis of history, physical examination, and urinalysis, especially in patients presenting with typical complaints of flank pain radiating to the ipsilateral groin, costovertebral angle tenderness, and hematuria [2]. Multiple imaging modalities, including intravenous pyelography, noncontrast computed tomography (CT), and ultrasound, have been used to diagnose renal colic [3], [4], [5], [6], [7], [8], [9], [10], [11]. In many EDs, noncontrast CT has become the dominant imaging modality because it allows determination of stone size and location, degree of hydronephrosis, and evaluation of other pathophysiologic processes that may masquerade as renal colic [2], [10], [11], [12]. Despite the advantages of CT, drawbacks include cost, accessibility, availability, increased length of ED stay, and risks from ionizing radiation [6], [13], [14], [15].
Focused emergency ultrasound is advantageous because it is nonionizing, inexpensive, and can be performed at the patient's bedside thereby becoming an integral part of the physical examination [16], [17]. Multiple studies using ultrasound in the evaluation of renal colic have demonstrated that ultrasound is accurate at detecting hydronephrosis and that emergency physicians can accurately determine the presence and degree of hydronephrosis but that ultrasound has limited use in directly detecting calculi or determining stone location [4], [5], [6], [7], [8], [9]. Furthermore, the presence of hydronephrosis on focused emergency ultrasound and hematuria on urinalysis is accurate in detecting and sufficient for diagnosing renal colic [18], [19]. Despite ultrasound not being as accurate as other modalities in determining stone location, stone size is a more important determinant of likelihood of stone passage and clinical outcome. Ureteral calculi less than 5 mm are likely to pass spontaneously regardless of location in the ureter, whereas those greater than 5 mm have a decreased likelihood of spontaneous passage or an increased likelihood of need for eventual urologic intervention [20], [21], [22]. For larger stones, current guidelines recommend a trial of passage with medical expulsion therapy for calculi between 5 and 10 mm; stones larger than 10 mm will require surgical removal in most cases [21].
The objective of our study is to determine if the degree of hydronephrosis on focused emergency renal ultrasound correlates with ureteral calculi size on noncontrast CT and to ascertain if these results would allow for prediction of stone size.
Section snippets
Methods
We performed a retrospective chart review using an emergency ultrasound database containing the findings and interpretations of the focused emergency ultrasounds performed in the ED of an academic medical center with an annual census of 70 000. All consecutive adult patients (≥18 years) in the database who had a complete focused emergency renal ultrasound performed and a noncontrast CT documenting ureterolithiasis for a 4-year period from March 2004 to March 2008 were enrolled. Approval for
Results
One hundred seventy-seven ultrasounds were performed in the ED on patients who had confirmed ureteral calculi on CT. Of these patients, 120 (67.8%) were male, and the mean age was 48.1 years old (range, 18-89 years old). One hundred forty-four patients (81.4%) had ureteral calculi 5 mm or smaller, and 33 patients (18.6%) had ureteral calculi larger than 5 mm. For the ultrasounds performed, there was very good interobserver agreement between the degree of hydronephrosis as determined by the
Discussion
Our study demonstrated a relationship between the degree of hydronephrosis found on focused emergency ultrasound and ureteral stone size on CT. We observed that increasing degree of hydronephrosis on ultrasound was associated with an increasing proportion of ureteral calculi larger than 5 mm. Most patients in this study had less severe (none or mild) hydronephrosis; these patients were less likely to have larger ureteral calculi. The specificity of an ED ultrasound demonstrating none or mild
Acknowledgments
Statistical analysis was assisted by Cristina Sison, PhD, Senior Research Statistician, Feinstein Institute for Medical Research. Alexander Tsukerman, MD, Department of Emergency Medicine, Long Island Jewish Medical Center performed data entry.
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2019, Emergency Medicine Clinics of North AmericaCitation Excerpt :In addition to attempting to visualize the stone, POCUS attempts to identify unilateral hydronephrosis as an indirect sign of obstructing ureteral stone, or bilateral hydronephrosis as a sign of bladder outlet obstruction (Fig. 7). Similarly, to comprehensive radiology US, POCUS scans do not always identify the location and size of the stone, but studies have suggested that a normal scan or mild hydronephrosis on POCUS indicates a smaller stone size (<5 mm)19 whereas moderate to severe hydronephrosis implies a larger stone and therefore predicts necessity for urologic intervention. A study by Rosen and colleagues20 showed a sensitivity and specificity of 72% and 73%, respectively, for the detection of hydronephrosis by bedside US in the emergency department.
Evaluation of the clinical significance of sonographic perinephric fluid in patients with renal colic
2019, American Journal of Emergency MedicineImaging in Suspected Renal Colic: Systematic Review of the Literature and Multispecialty Consensus
2019, Journal of the American College of RadiologyCitation Excerpt :Diagnostic accuracy was based on presence of hydronephrosis rather than direct visualization of stones, and pooled results yielded sensitivity of 70.2% and specificity of 75.4%, although specificity increased to 94.4% when moderate or greater hydronephrosis was used as a criterion [24,25]. Four studies did show a positive association between stone size, and larger stones had a higher likelihood of intervention when hydronephrosis was present [24,26-28]. A multicenter, pragmatic, comparative effectiveness trial published in 2014 randomized over 2,500 patients with suspected kidney stones to POCUS, RPUS, or CT and concluded that ultrasound (RPUS or POCUS) is a safe approach for the evaluation of ureterolithiasis, noting that “return emergency department visits, hospitalizations, and diagnostic accuracy did not differ significantly among the groups” [5].
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Previously presented at the American College of Emergency Physicians Scientific Assembly, Seattle, Wash, October 2007.