kidney stone diagnosis and managment ak et al. rsna 2010

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HARVARD MEDICAL SCHOOL Kidney Stone Diagnosis and Managment Dushyant Sahani MD

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Page 1: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

HARVARD MEDICAL SCHOOL

Kidney Stone Diagnosis and Managment

Dushyant Sahani MD

Page 2: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Disclosures

• MGH has research agreement – GE Health Care– Siemens Medical Systems

Page 3: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Clinical Perspective

• Urolithiasis has a life time risk of 10-15% • It has a high relapse rate (50% in 5-10 yrs and 75% in 20 yrs)• Affects Men more than women

• Common clinical presentation – Acute flank pain and hematuria

Prevalenceof

Urolithiasis3.2%

5.2%

1970s 1990s1980s

Rising Prevalence

Curhan, G.C., Epidemiology of stone disease. Urol Clin North Am, 2007. 34(3): p. 287-93.

Page 4: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

MDCT in Urolithiasis• Unenhanced CT - Initial investigation of choice in suspected urolithiasis

– 22% of all CT performed in the ER for acute abdomen pain

• Highly accurate test (Sensitivity = 95-98% & Specificity =96-100%)

– Detects other causes of acute flank pain

• Identification of ureterolithiasis at imaging altered management in nearly

55%–60% of patients suspected of having acute renal colic.

• Reveals associated abnormalities like congenital abnormalities,

infections and neoplasms• Rosen MP et al. Eur Radiol 2003;13(2):418–424.• Dalrymple NC et al. J Urol 1998;159(3):735–740.• Wrenn K. Ann Emerg Med 1995;26(3):304–307.

Page 5: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Stone Types

Calcium oxalate monohydrate (COM) & dehydrate (COD)

40-60% Radio-opaque Radio-opaque

Hydroxyapatite (Calcium phosphate)

20-60% Radio-opaque Radio-opaque

Radio-opaque Radio-opaque 2- 4%Brushite

Uric Acid Radio-opaque Radio- lucent 5-10%

Struvite 5-15% Radio-opaque Radio-opaque

Radio-opaque 1- 2.5% Mildly Opaque Cystine

Composition On KUB On CTOccurrence

Radioopacity

Page 6: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

MDCT Technique

• Scan Coverage - Upper pole of kidneys to the base of the bladder

• Patient preparation -Bladder distension to visualize stones within the distal ureter

Coronal Reformations (2.5 - 3mm)

Slice thickness – 3-5 mmPitch - 1 - 1.6

Page 7: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Urolithiasis –CT Diagnostic Signs

Primary sign of Ureterolithiasis

Stone in the ureter (target sign) with proximal

hydroureter

Virtually all stones are

radio-opaque on CT (>200HU)

Stones radiolucent on CT - Pure matrix stones and stones made of pure Indinavir (Indinavir - Protease inhibitor used in the treatment of HIV)

Page 8: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

• Improved detection of stones unrecognized on axial images

• Improved detection of small ureteral and renal calculi at poles

• Phleboliths and calcified vascular plaques from urinary stones

• Enhances radiologist confidence

• Benefits the urologists in treatment decision

1 2

Value of Coronal Reformations

Lin WC et al. J Urol 2007.

Page 9: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Factors Influencing Treatment Decision

Presence of obstruction is not the primary factor

considered for urologic intervention

Urologic intervention is influenced by 3 crucial factors

Stone size/ location

Stone Composition

Patient Symptoms

• Bierkens AF et al. Br J Urol. 1998.• Eisner BH et al. Urology 2008. • Phipps S et al. Ann R Coll Surg Eng 2010.

Page 10: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

8mm 6 mm

• Accurate stone size measurement is paramount to plan treatment options

• The ideal method for accurate measurement on CT is to measure using

bone window settings (1250 X 250) and magnification

Soft tissue window Bone window with Magnification

Stone Size

• Stone burden (stone size and volume) determines the type of procedure

• ESWL or Ureteroscopy is performed for stones <1cm

•PCNL for stones >1.5cm

Stone Burden Assessment

Eisner BH et al. J Urol 2009

Page 11: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Stones > 6mm & <15mm(6-9 mm uereteral stone 60-25% pass)

Stone location predicts outcome Upper=48%, mid=60%, lower 75-79%

likely to pass spontaneously

Stone < 5mm (98% for stones < or = 4mm

pass spontaneously)

Medical Expulsive therapy(Alpha blockers)

Intervene for unremitting pain, nausea, fever, failure

to passage on medical therapy

• Extracorporeal Shockwave lithotripsy (ESWL)

• Ureteroscopic lithotripsy (upper ureter or larger stone)

Stone >15mm or Staghorn Calculi

Percutaneous Nephrolithotomy

(PCNL)

Stone Size & Treatment Decisions

• Bierkens AF et al. Br J Urol. 1998.• Coll DM et al. AJR 2002.• Eisner BH et al. Urology 2008. • Phipps S et al. Ann R Coll Surg Eng 2010.

Page 12: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

• Linear measurement not suitable in irregularly contoured stones like

stag horn calculi

• Measuring the stone volume eliminates this problem

• Total stone volume is an appropriate measure of stone burden

22 cc

Stone Volumetry

Threshold based CAD Algorithms or manual semi-automated methods

• Demehri S et al. AJR 2012.• Singh Ak et al. RSNA 2010.

Page 13: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Independent Variables

(Dependent Variable= failure

rate)

Area-Under Curve (AUC)

Cut-off value Sensitivity; Specificity (%)

95% Confidence

Interval (CI)

P=value

Stone Volume CAD 0.895 >712.54 mm3 80;80 0.745-0.964 P<0.0001

Stone Volume-Products

0.872 >564.75 mm3 88;73 0.728-0.956 P<0.0001

Maximum Stone Size

0.839 >8.89mm 96;60 0.688-0.936 P<0.0001

Number of Stones 0.755 >2 52;86 0.593-0.877 P=0.0002

Mean Stone Size 0.735 >6.25mm 92;46.7 0.571-0.861 P=0.0002

Age 0.524 <50y 96;33 0.360-0.684 P=8267

Overall model fit (Chi square)=21.818; p=0.0006

ESWL Failure: Multivariate CT characteristics

Singh Ak et al. RSNA 2010.

Page 14: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

<400 HU

Uric Acid Stone

Medical ManagementAllopurinol

Treatment of Hyperuricemia

<1000 HU(Struvite)

ESWL

>1000HU (Brushite, Cystine, COM)

UreteroscopyPCNL

Stone Composition & Treatment Decisions

> 500 HU

Hamm M et al. J Urol 2002.Parker BD et al. Urology 2004

Page 15: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

MDCT and Stone CompositionStone composition can be determined using HU

CT Attenuation values – 64-77% accuracy in determination of stone

composition, is not robust and reliable

Stone Composition Attenuation value at 120kVp

Uric Acid 200-450 HU

Struvite 600-900 HU

Cystine 600-1100 HU

Calcium Phosphate 1200-1600 HU

COM and Brushite 1700-2800 HU

• Stone composition also effects the efficacy of ESWL (Brushite, cystine and

COM stones are hard and resistant, while struvite stones usually fragment easily)

Dretler SP. J Endourol 2001Motley G et al. Urol 2001Eisner BH et al. J Urol 2009KulkarniN et al. JCAT (in-press)

Page 16: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Uric Acid Stone Non uric acid stone

Element composition Light Elements(H, C, N, O)

Heavy Elements(P, Ca, S)

Attenuation at 80 kVp Lower HU Higher HU

Attenuation at 140 kVp Higher HU Lower HU

80kV

Calcium710 HU

Uric Acid290 HU

140kV

Calcium480 HU Uric Acid

315 HU

DECT: Stone composition

Page 17: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Renal Stone Composition: 11 studies (dsDECT=8 & ssDECT=3)

• Uric Acid vs. Non UA stone differentiation possible– Phantom and humans 100% – Reliable for stones 3 mm and above

• Non-UA subtype of pure composition possible in phantom and in humans – mixed composition stones difficult to characterize

Stolzman P. Urol Res 2008, Graser A. Invest Radiol 2008, Matlaga B. Urology 2008, Graser A . Eur Radiol 2009, Thomas C. Eur Radiol 2009, Ball D. Radiology 2009,, Hidas G. Radiology 2010, Manglaviti G. AJR 2011, Kulkarni N. JCAT (in-press)

Page 18: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Stone Fragility in Guiding Treatment

• CT helps predict stone fragility and susceptibility to lithotripsy

• Stones which are heterogeneous are more fragile than homogenous

stones which are more resistant to ESWL

HeterogenousMore fragile toLithotripsy

HomogenousMore resistantto lithotripsy

Page 19: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Stone Precursor-Randall’s Plaque

Normal papillae

Stone bearing papillae

30 HU

58 HU

• Randall’s Plaque - Calcium salt deposits

in the tip of renal papilla of patients with

nephrolithiasis and are potential sites for

calculus formation

• These stone bearing papillae appear

denser on non-contrast CT and represent

Randall’s plaque on endoscopy

• MDCT can help select patients at high-

risk for stone formation, who may

undergo appropriate medical

management to halt the formation of

stones

Whitish deposits- Randall’s plaque

Eisner BH et al. J Endourol 2008

Page 20: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

MDCT in Planning Intervention

• Simple trigonometry on CT of the patients with complex stones could help

endourologists in planning renal access.

• CT also helps in planning surgical interventions by identifying the location of the

posterior calyx thus guiding fluoroscopic procedures like percutaneous

nephrolithotomy

Page 21: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Calculi with attenuation > 300 HU are radio-opaque & are followed up by Abdominal Radiograph

Calculi with attenuation < 200 HU are radiolucent & hence followed up by CT

>300 HU Follow up Radiograph <200 HU Follow up CT

In patients managed medically,

CT attenuation is a good predictor of utility of radiography in routine follow up

Stone Follow up

Page 22: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Pre Treatment Post Treatment

Significant Stone Burden Residual Stone Burden though significantly reduced

Significant stone burden necessitates further treatment

Stone Follow up –Post Intervention

Page 23: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

• Differentiation between stent and stone is vital in post surgical follow up

• Stents and stones have the same CT appearance on abdominal window.

• Bone window allows visual distinction between the stent and the stone

which is accounted for by differences in pixel density.

Stones

Stent

Bone windowAbdominal window

Stone vs Stent

Tanricut C et al. Urology 2004

Page 24: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

• A key concern for repeated CT examinations in recurrent stone disease.

• The effective radiation dose during unenhanced CT

2.8 to 13.1 mSv for men / 4.5 to 18 mSv for women

• Techniques for Reduction of Radiation dose

- Limit scanning area (not typical Abd+Pelvis exam)

- Increase in axial slice thickness to 5mm from 1-3 mm

and include 2.5-3 mm coronal reconstructions

- Lower dose CT exam ( noise index, kVp, pitch)

MDCT and Radiation Dose

Page 25: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Strategies for Dose ReductionLimit

Scanning area

+Low mAs

+Low kVp+

Increase slice thicknessInclude coronal reformations

DLP 1000 mGy-cm

Total Dose Reduction by 40-70% from Standard dose

DLP 200 mGy-cm

Page 26: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Renal stone

Initial scan – Standard dose CT (low mAs)

Follow up scan – ultra-low dose CT

Ultra-low dose approaches

WT kVp mA

Low dose CT <200 lbs 80 75-150

> 200 lbs 100 75-150

Page 27: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Ultra-low dose approaches

177 lbs 280 lbs

Page 28: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

FBP Partial IR Full IRSimple Comprehensive Advanced

Ideal System

Few Iterations Advanced

model

Simple Fast

High noise

Better IQLow doseLow noise

Optimal IQLow noise

Better resolution

CPU CPU CPU

VS. VS.IRIS/ASIR/iDOSE/ADIR/SAFIRE MBIR/Veo

Blend FBP+IR

Page 29: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

DLP 3885.82

DLP 1842.76

18 DEC 2007 22 DEC 2008

53%

Page 30: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Radiation Dose-ULD Stone CT

8.8

1.1

mS

v

Std dose CT ULD CTWt

CategoryCTDI mSv CTDI mSv

Over all 11.4 8.8 1.8 1.1< 200 lbs 10.6 8.6 1.3 0.8> 200 lbs 15.4 10.8 2.3 1.5

87% 90% 85%

2 view KUB

Kulkarni N M et al. Radiology 2012

Page 31: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

=2 View KUB = 0.6 – 1.2 mSv CT KUB = < 1 mSv

Kulkarni N M et al. Radiology doi:10.1148/radiol.12112470

More aggressive dose reductionMore aggressive dose reduction

Page 32: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Author Year AbdomenCT

MarinD Radiology.2010

PrakashP InvestRadiol.2010

SagaraY AJRAmJRoentgenol.2010

SinghS Radiology.2010

MayMS InvestRadiol.2011

SchinderaST Radiology.2011

MartinsenAC EurJRadiol.2011

VoronaGA Pediatr Radiol.2011IQ Dos

e

20%-50%

Page 33: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Current Imaging Strategy

The scope of imaging has extended beyond the mere

detection of stone and its location

The current strategy is to determine the stone composition,

its fragility and quantification which has great implications in

treatment planning

Page 34: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Summary Points• MDCT with multiplanar reformations is accurate in stone assessment

• The qualitative assessment by CT influences management by

dictating treatment options like ESWL.

• Spectral imaging and CAD is emerging for stone

composition/Quantitation

• Various stratergies for radiation dose reduction in imaging of

urolithiasis achieving accurate diagnosis and reduced radiation dose

delivery.

• New reconstruction algorithms (ASIR) is promising in dose reduction

Page 35: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Dushyant V Sahani, MDDivision of abdominal imaging and intervention

Department of RadiologyMassachusetts General Hospital

White 270, 55 Fruit streetBoston, MA-02114

Email:[email protected]

Ph (o): 617-726-8396

Thank You

Page 36: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

1. Curhan, G.C., Epidemiology of stone disease. Urol Clin North Am, 2007. 34(3): p. 287-93.2. Sandhu, C., K.M. Anson, and U. Patel, Urinary tract stones--Part I: role of radiological imaging

in diagnosis and treatment planning. Clin Radiol, 2003. 58(6): p. 415-21.3. Ege, G., et al., Acute ureterolithiasis: incidence of secondary signs on unenhanced helical CT

and influence on patient management. Clin Radiol, 2003. 58(12): p. 990-4.4. Heneghan, J.P., et al., Helical CT for nephrolithiasis and ureterolithiasis: comparison of

conventional and reduced radiation-dose techniques. Radiology, 2003. 229(2): p. 575-80.5. Boulay, I., et al., Ureteral calculi: diagnostic efficacy of helical CT and implications for treatment

of patients. AJR Am J Roentgenol, 1999. 172(6): p. 1485-90.6. Fielding, J.R., et al., Unenhanced helical CT of ureteral stones: a replacement for excretory

urography in planning treatment. AJR Am J Roentgenol, 1998. 171(4): p. 1051-3.7. Lin WC, Uppot RN, Li CS, Hahn PF, Sahani DV. Value of automated coronal reformations from

64-section multidetector row computerized tomography in the diagnosis of urinary stone disease. J Urol 2007; 178:907-911; discussion 911.

8. Smith, R.C., et al., Diagnosis of acute flank pain: value of unenhanced helical CT. AJR Am J Roentgenol, 1996. 166(1): p. 97-101.

9. Eisner BH, Iqbal A, Namasivayam S, Catalano O, Kambadakone A, Dretler SP, Sahani DV. Differences in Computed Tomography Density of the Renal Papillae of stone formers and Non-stone formers: A pilot study. J Endourol 2008 Oct 2.

10. Bilen CY, Kocak B, Kiticci G, Danaci M, Sarikaya S. Simple trigonometry on computed tomography helps in planning renal access. Urology. 2007 Aug;70(2):242-5; discussion 245

References

Page 37: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Jouranal/Year

DECT Technique

# Stones

Page 38: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

• Dual Source CT: By operating the two

tubes at different energies (80 & 140 kVp)

it is effective in tissue material composition

•Gem stone spectral imaging (single

source DECT) - is a recent DE CT

operated on rapid kVp switching is also

available for tissue characterization/stone

composition

1

2

2

1

Dual-Energy CT for Stone Composition

Stolzman et al Urol Res 2008, Graser et al 2008 Invest Radiol, Graser et al 2009 Eur Radiol, Thomas et al Eur Radiol 2009

Page 39: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

140 kV80 kV

(Syngo VA 11; Siemens)3 material decomposition algorithm

• Uric acid stones - Red

• Non Uric acid stones - Blue

Post Processing - DSDCTPost Processing - DSDCT

80

140

High and low kVp Two X-ray tube

Page 40: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Post Processing - SDCTPost Processing - SDCTMD IodineMD Water

Effective Z Image

Uric Acid stone = MD Water +, MD Iodine –

Non-Uric Acid stone = MD Water +, MD Iodine +High and low kVp Rapid kV twitching

Effective z number – scatter plot

Page 41: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Phantom Model – Uric Acid vs Non uric Acid

Accuracy Sensitivity<3mm >3mm

DSDCT(UA -16, Non UA =49)

8/8(100%)

57/57(100%)

65/65 (100%)

SDCT(UA -6, Non UA =29)

2/2(100%)

33/33(100%)

35/35 (100%)

DSDCT SDCT

MD Iodine

Uric acid Non-Uric acid Uric acid Non-Uric acid

MD Water

65 stones (Size Range- 2-18mm) 35 stones (Size range 3-19mm)

Uric acid Non-Uric acid

Dual-Energy CT for Stone Composition

Page 42: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Patients – Uric Acid vs Non uric AcidDSDCT SDCT

Final confirmation- 9/18 patients- 20 Stones (6 uric acid & 14 non uric acid)

37 stones Mean size-6mm, Range 2-24mm)

CT

UA 7

Non UA 23

Not Identified 7

49 stones(Mean size-6.8mm, Range 1.2-28mm)

CT

UA 15

Non UA 34

Not Identified -

Final confirmation- 3/17 patients- 8 Stones (All calcium oxalate)

Dual-Energy CT for Stone Composition

Page 43: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Red Blue1.15 Uric Acid Struvite, Brushite,

COM, Cystiene

1.30 Uric acidStruvite

Cystine, BrushiteCOM

1.45 Uric acidStruvite, Cystine

BrushiteCOM

1.60 Uric acid, Struvite, Brushite, COM, Cystiene

90% Cystine stones (9/10) / 84.2% Struvite stones (11/13)

SDCTPhantom Model – Differentiation of Non uric Acid

CalculatedEffective z

Effective Z

Uric Acid 6.92 7.2

Struvite 9.72 9.99

Cystine 11.07 11.25

COM 14.37 13.12

DSDCT

100% Accuracy

Dual-Energy CT for Stone Composition

Page 44: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Dose Reduction by 15-20%

Strategies for Dose Reduction– Coverage Area

From top of diaphragm to lower border of pubic symphysis

From Top of kidneys to base of urinary bladder

Restrict Scanning Area

Targeted scans focused to area of interest can be performed for follow up CT exams

Page 45: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Increase Slice thickness from 1-3mm to 5mm and include 2.5-3mm Coronal Reformations

1-3mm 5mm

Strategies for Dose Reduction - Slice Thickness

Dose Reduction by 20-40%

Page 46: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Strategies for Dose ReductionRole of Low kVp - Exam based on Body Weight

140 kV (> 250 lbs)

120 kV (141-249 lbs)

Dose= kVp

100/80 kV (<140 lbs)

20% reduction

20% reduction

Total 40 % Dose Reduction

Page 47: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Strategies for Dose Reduction- Increase in Noise Index/ reference mAs (100-180)

Noise Index -15

Noise Index -20

Noise Index -30

15-20% reduction

15-20% reduction

Total 30-40 % Dose Reduction

Page 48: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

GE WT Slice Th mA NI

16/64-MDCT

<300 5 150-450 25- I

30 - F

>300 5 150-450 25- I

30 - F

NI- Noise indexI - Initial scanF- Follow up scan

kV (100-120)

MDCT Protocol Modifications

Siemens WT Ref mA

Sl Thick

DC Pitch

16-64 All wt group

100-160

5 24x1.2 1.2

Page 49: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

Review Phase (116 lbs)

Monitoring Phase (114 lbs)

CTDI- 11.5

CTDI- 4.22

61%

MDCT Protocol Modifications

Page 50: Kidney Stone Diagnosis and Managment Ak et al. RSNA 2010

• MGH Experience (GE HD 750) 65 patients studied so far• Radiation dose reduction achieved (25-81%)

Adaptive Statistical Iterative Reconstruction (ASIR)

• Noise reduction reconstruction method to improve the

signal-to-noise

• Relies on the accurate modeling of the distribution of

noise in the acquired data

Kole et al 2006 Phys Med Biol