LSU Journal ClubUltrasounography versus Computed

Tomography for Suspected Nephrolithiasis

R. Smith-Bindman, C. Aubin, J. Bailitz, C.A. Camargo, Jr., J. Corbo, A.J. Dean, R.B. Goldstein, R.T. Griffey, G.D. Jay, T.L. Kang, D.R.Kriesel, O.J.Ma, M. Mallin, W. Manson, J,. Melnikow, D.L. Miglioretti, S.K. Miller, L.D. Mills, J.R.Miner, M. Mighadassi, V.E.Noble,

G.M. Press, M.L. Stoller, V.E. Valencia, J,. Wang, R.C.Wang, and S.R.Cummings

Abby Gandolfi, PGY 1November 20, 2014

Background• Cost of acute care for nephrolithiasis: 2 billion

annually • Fairly common ED presentation, but lack of

consensus as to regarding initial imaging modality• Abdominal CT is currently most common based on

sensitivity over ultrasound

• Drawbacks to CT: -Radiation exposure and long term risk of cancer - Incidental findings - Cost of CT, 2 billion a year acute care cost • No evidence that diagnosis via CT leads to better

patient outcomes

Background

Research question

• What is the effect of diagnostic imaging techniques, specifically CT versus ultrasound, on patient outcomes in the initial work up of suspected nephrolithiasis?

• Compared ED physician-performed ultrasound (point-of-care) radiologist performed ultrasound, and CT

Research Question • Primary outcomes

measured:– high risk diagnoses

that could be delayed or missed

– Cumulative radiation exposure

– Total cost, not reported in study

Any of the following diagnoses made within 30 days of initial ED presentation: -AAA with rupture -PNA with sepsis -appendicitis with rupture -diverticulitis with abscess or sepsis -Bowel ischemia or perforation -Renal infarct -Renal stone with abscess -Pyelonephritis with sepsis or bacteremia -Ovarian torsion with necrosis -Aortic dissection with ischemia

•Patients followed for 180 days after presentation

Research QuestionSecondary Outcomes: • Serious adverse events • Serious adverse events related to study

participation • Repeat ED visits and hospitalizations• Patient reported pain score• Diagnostic accuracy for nephrolithiasis

Confirmation of presence of stone within 6 months based on patient reported stone passage or surgical removal

Study Design

• Multicenter, randomized, comparative effectiveness trial

• October 2011 to February 2013• Conducted across 15 ED’s at geographically

diverse academic medical centers

Study design

-Patients who presented to the ED with suspected nephrolithiasis were randomly assigned to one of the three imaging groups

-Randomization 1:1:1 via SAS software and only occurred during hours when all 3 modalities were available

Study Subjects• Compiled data of 2759 patients age 18

to 76, all were consented

• Patients selected if chief complaint included flank or abdominal pain and if the treating physician decided that work up would include imaging to rule out nephrolithiasis as primary diagnosis

Table 2:Clinical Data and Provisional Diagnosis by Emergency Dept Physicians

Study SubjectsExclusion criteria: • High clinical suspicion for alternative, serious

diagnosis• Pregnant women • Men weighing more than 129kg or 285 lbs• Women weighing more than 113 kg or 250 lbs • Any patients with single kidney, s/p kidney

transplant, or dialysis patients

Results: Primary Outcomes

Results: Primary Outcomes• Cumulative radiation exposure was significantly lower in

patients who underwent ultrasound • 11 patients were identified with an alternative high risk

diagnosis,– 6 patients in the point of care ultrasound group – 3 patients in the radiology ultrasound group

• 2 patients in the CT group • No statistically significant difference among imaging modality

when a serious alternative diagnosis was made

Results: Secondary Outcomes

Results: Secondary Outcomes• Adverse events

– no significant difference

• ED length of stay– Longer time in ED for radiology ultrasound and CT groups

• Return ED visits– No statistical difference among groups

• Diagnostic accuracy – Based on result of initial imaging showed ultrasound had lower sensitivity and higher specificity sensitivity 54% POC, 57% radiology u/s, 88% CT specificity 71% POC, 73% radiology u/s, 58% CT– Based on confirmation of stone within 6 months, sensitivity and specificity for diagnosis were

similar across 3 groups – Patients who underwent u/s initially more likely to undergo subsequent testing

• 40% pts with point of care u/s got a subsequent CT• 27% of pts with radiology u/s got a subsequent CT• 5% of pts who got initial CT got additional ultrasound

Conclusions• Authors conclude that ultrasound should be initial

test of choice in suspected nephrolithiasis– Lower total radiation– No significant difference in missed high risk

diagnosis – Though more u/s patients had subsequent CT,

most u/s patients did not undergo any additional imaging

Conclusions• Start evaluation with ultrasound and then obtaining

additional imaging based on clinical judgment • Patients with history of nephrolithiasis have likely

had high cumulative radiation exposure, ultrasound preferred here

• CT has greater sensitivity, but did not translate to better outcomes

• As expected, point of care u/s had shortest length of stay but highest incidence of subsequent CT