stone protocol ct: why, how and pitfalls

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Hello…. CT Stone Protocol Why, How and Pitfalls Rathachai Kaewlai, MD Division of Emergency Radiology, Department of Radiology Ramathibodi Hospital, Bangkok, Thailand For RCRT-RST Annual Scientific Meeting, 24 Mar 2016

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Page 1: Stone protocol CT: Why, How and Pitfalls

Hello…. CT Stone Protocol

Why, How and Pitfalls

Rathachai Kaewlai, MD

Division of Emergency Radiology, Department of Radiology

Ramathibodi Hospital, Bangkok, Thailand

For RCRT-RST Annual Scientific Meeting, 24 Mar 2016

Page 2: Stone protocol CT: Why, How and Pitfalls

Why – How – Pitfalls

Page 3: Stone protocol CT: Why, How and Pitfalls

Why NCCT for KUB Stone?

Page 4: Stone protocol CT: Why, How and Pitfalls

Virtually All KUB Stones Are Radiopaque on CT Composition Frequency

(%) Radiopacity Radiograph

Shade of White on CT

Calcium phosphate 10 4

Calcium phosphate/oxalate

40 3-4

Calcium oxalate 30 3

Struvite 10 2-3

Cystine 1 1

Uric acid 10 0

Genitourinary Imaging: the Requisite

Page 5: Stone protocol CT: Why, How and Pitfalls

Stone Types Based On CT Characteristics

Page 6: Stone protocol CT: Why, How and Pitfalls

Detection of Stones

X-ray IVU Ultrasound NCCT

Sensitivity (%) 44-77 52-87 19-93 94-100

Specificity (%) 80-87 94-100 84-100 92-100

Page 7: Stone protocol CT: Why, How and Pitfalls

ACR Appropriateness Criteria (2015)

Page 8: Stone protocol CT: Why, How and Pitfalls

ACR Appropriateness Criteria (2015)

Page 9: Stone protocol CT: Why, How and Pitfalls

ACR Appropriateness Criteria (2015)

Page 10: Stone protocol CT: Why, How and Pitfalls

Diagnostic Strategies

Page 11: Stone protocol CT: Why, How and Pitfalls

Factor Definition Level Points

Sex Female Male

0 2

Timing Duration of pain from onset to presentation, h

>24 6-24 <6

0 1 3

Origin Race Black Nonblack

0 3

Nausea Presence of nausea and vomiting

None Nausea only Vomiting

0 1 2

Erythrocyte Hematuria on urine dip Absent Present

0 3

Total 0-13

STONE score for uncomplicated ureteral stone in ED

Moore CL, et al. BMJ 2014;348:g2191

Page 12: Stone protocol CT: Why, How and Pitfalls

Points Probability of

symptomatic stone on CT %

Recent validation

(n=264)

0 to 5 Low 10% 10%

6 to 9 Moderate 10-90% (~50%)

60%

10 to 13 High >90% 89%

STONE score for uncomplicated ureteral stone in ED

Moore CL, et al. BMJ 2014;348:g2191 Moore CL, et al. Radiology 2016 March

Page 13: Stone protocol CT: Why, How and Pitfalls

STONE score Sensitivity Specificity

Low probability (n=144) without ultrasound with ultrasound

3 64

67 87

Moderate probability (n=411) without ultrasound with ultrasound

41 60

42 71

High probability (n=280) without ultrasound with ultrasound

55 69

91 60

Daniels B, et al. Ann Emerg Med 2016 March

STONE PLUS for uncomplicated ureteral stone in ED

Page 14: Stone protocol CT: Why, How and Pitfalls

Daniels B, et al. Ann Emerg Med 2016 March

Page 15: Stone protocol CT: Why, How and Pitfalls

Ramathibodi Protocol (WIP) < 80 kg >/= 80 kg

kVp 100 120

mA 70-250 70-350

Rotation time (s) 0.6 0.6

SureExposure 3D 20 20

PF/HP 0.828/53 0.828/53

Slice thickness/interval (mm) 2.0/1.5 2.0/1.5

Page 16: Stone protocol CT: Why, How and Pitfalls

Stone CT Radiation Dose

Page 17: Stone protocol CT: Why, How and Pitfalls

Stone CT Radiation Dose: How Low Can We Go?

Page 18: Stone protocol CT: Why, How and Pitfalls

Moore CL, et al. Ann Emerg Med 2015;65:189

N=201 Prospective, head-to-head comparison standard v reduced-dose CT

Two groups: BMI <30 v. BMI >30

Page 19: Stone protocol CT: Why, How and Pitfalls

2.2 mSv

Reduced-dose CT

Page 20: Stone protocol CT: Why, How and Pitfalls

Initial CT

F/U CT (known stone) Can accept more noise to reduce dose

8.3 mSv

3.7 mSv

Page 21: Stone protocol CT: Why, How and Pitfalls

How About Giving IV Contrast?

Page 22: Stone protocol CT: Why, How and Pitfalls

Forniceal rupture with urinoma due to obstructing Lt UVJ stone

UVJ stone

Delayed nephrogram

Perinephric fluid

Urine extravasation confirmed at delayed scan although this phase is not necessary

Page 23: Stone protocol CT: Why, How and Pitfalls

McLaughlin PD, et al. Insights Imaging 2014;5:217

5.1 mSv (ASiR)

5.1 mSv (FBP)

0.56 mSv (FBP)

0.56 mSv (40% ASiR)

0.56 mSv (70% ASiR)

0.56 mSv (90% ASiR)

CT Doses Even Lower than Abdominal Radiograph

N=33 Comparing routine and sub-mSv CT (with iterative recon)

Calculi >3 mm: Sensitivity 87%, specificity 100%

1 missed appendicitis 1 missed dermoid

Advanced scanner can reduce dose further with

iterative reconstruction

Page 24: Stone protocol CT: Why, How and Pitfalls

High-density calcium stone in renal pelvis with obstruction

Advanced scanner can predict which stone is uric acid (medical) or non-uric acid

Page 25: Stone protocol CT: Why, How and Pitfalls

How We Interpret CT Stone Protocol

Page 26: Stone protocol CT: Why, How and Pitfalls

Soft tissue rim sign = ureteral stone

Page 27: Stone protocol CT: Why, How and Pitfalls

Stone Size and Appearance

Page 28: Stone protocol CT: Why, How and Pitfalls

Perinephric/periureteric Changes

Page 29: Stone protocol CT: Why, How and Pitfalls

Risks for Stone Formation Identifiable on Imaging

Page 30: Stone protocol CT: Why, How and Pitfalls

Typical Cases

hydronephrosis

stone

Page 31: Stone protocol CT: Why, How and Pitfalls

Distal ureteric stone with obstruction

Typical Cases

Hydronephrosis & minimal perinephric fat stranding

stone

Page 32: Stone protocol CT: Why, How and Pitfalls

Unilateral Perinephric Fat Stranding w/o Stone - DDx

Page 33: Stone protocol CT: Why, How and Pitfalls

Mimickers on CT of:

Page 34: Stone protocol CT: Why, How and Pitfalls

Moore CL, et al. Acad Emerg Med 2013;20:470

N=5383 Descriptive study No comparison Two EDs

Alternative Diagnosis

Page 35: Stone protocol CT: Why, How and Pitfalls

Incidental Findings

Samim MM, et al. JACR 2015;12:63

Page 36: Stone protocol CT: Why, How and Pitfalls

Samim MM, et al. JACR 2015;12:63

N=5383 Descriptive study, no comparison Two emergency departments

Page 37: Stone protocol CT: Why, How and Pitfalls

Take Home Messages