Various stones scores and its prediction in stone clearance

1. STONE SCORES
A review
Sukhdev, CMC Vellore

2. Why do we need to score a stone?
• Accurate counselling pre operatively
• Objective assessment of technical modifications
• Benchmarking
• Rationalization of complex cases to specialist centres

3. Phases of score development
• Development
• Reproducibility
• Validation
Ideal scoring
• Straightforward
• Easy to use (like ASA score)

4. Guys score
• Stone Unit in Guys Hospital, London
• Pre operative imaging – radiograph, CT, IVU
• At 6 weeks, plain KUB radiograph; CT/USG in select cases(like
radiolucent stones)

5. Development
• Combo of literature review, expert opinion, iterative process
• Iterative plan/do/act/study process

7. Reproducibility
• Additional 40 cases were evaluated by 3 clinicians(2 senior
endourologists and 1 urology trainee)
• The scorers were given a copy of the image of the scoring system and
the radiographic images
• Inter-rater agreement was calculated using the free marginal kappa
coefficient
• Overall agreement was 86%
• Most disagreement were in Guy score 2-3 because definition of
partial staghorn was not defined

8. Internal validation
• 100 consecutive PCNL cases from November 2007 to December 2008
• Multivariate regression analysis of factors like : stone score, stone
burden, operating surgeon, patient age, weight, co morbidities and
urine culture findings
• Outcomes were SFR, complication rate and severity, operation time,
radiation time and exposure

10. Limitations
• Single centre study with small number of patients
• CIRF definition. Smaller size of CIRF would furthermore decrease the
SFR
• Pre operative imaging modalities were not stratified

11. STONE Nephrolithometry score

12. Development
• Systematic review
• MEDLINE review of English language studies from 1976 to 2012
• Variables that affected the outcomes of PCNL were studied
• Studies were limited to those which used NCCT KUB for pre operative imaging of calculi.
• 5 variables
1. S – Stone size
2. T – Tract length
3. O – degree of Obstruction
4. N – Number of involved calices
5. E – Essence of stone

13. • Stone size – length * width in mm2
• Tract length – skin to stone distance – mean vertical distance from
centre of stone to skin measured on supine NCCT KUB at 00, 450, 900
• Obstruction : none or mild – 1 point; moderate to severe – 2
• Score can range from 5-13

14. Reproducibility

15. • Retrospective review of NCCT KUB of 70 patients who underwent
PCNL
• Done by
1. 2 medical students
2. 2 urology residents
3. 1 urology fellow and 1 attending physician
• The inter observer variability were rated using ƙ coefficient of
concordance

17. • Medical students : obstruction is the least concordant and tract
length is the most concordant
• Residents: stone size is the least concordant and tract length is the
most concordant
• fellow/attending physicians : obstruction is the least concordant and
tract length is the most concordant

18. Reasons for variation
Stone size:
• Most stones are not perfectly geometric
• Measuring sizes among different axial images, planes were difficult
• Hence the least concordant
Tract length:
• Multiple stones with varying SSDs can be difficult
• The farthest stone was used for calculation because it will be the most
difficult to break by PCNL
• And also, only 2 divisions of scores - ≤10 cm and >10 cm. so, tract length is
the most concordant

19. Obstruction:
• Relies heavily on user knowledge of renal anatomy in CT
• So, this score was also given only 2 subdivions: none-mild – 1 and
moderate-severe : 2
• However, localised obstruction may be difficult to score

20. Number of calices involved
• Second least concordant

21. Essence
• Density of stone is calculated by marking the stone excluding urine
and soft tissues around it, which makes it difficult for an irregularly
shaped stone
• Also, in a lamellated stone, density may vary from periphery to centre
• So, only 2 subdivisions were given for scoring: ≤950 HU and >950 HU

22. Internal validation
• Prospective evaluation of patients who underwent PCNL
• Patients with PCN or DJS
• Patients who had other open, endoscopic or laparoscopic procedures
along with PCNL
• Patients who underwent second stage PCNL
Were excluded

23. • Primary outcome was SFR
• Residual calculi were assessed using:
1. Intra operative flexible nephroscopy
2. Post operative NCCT KUB on POD 1 for radiolucent stones
3. USG at 3 months for all patients

24. • From November 2009 to October 2011, 117 subjects met the criteria
and were included in the study
• Overall SFR was 80%

26. • Overall STONE score yielded an accuracy of 83% in predicting SFR
• However, tract length, stone density and presence of HUN were not
significant enough to predict SFR
• Though stone size and number of calyces had the most
interobserver variability, they predicted SFR better than other
individual components

28. CROES Nomogram

29. • Clinical Research Office of the Endourological Society
• November 2007 to December 2009
• 5803 patients from 96 centres globally; each centre performed at
least 10 PCNLs annually

30. Variables
• Stone burden : 0.785 * length * width. Individual stone burdens to be
added for multiple stones
• Stone location
• Stone count
• Case volume/year
• Presence/absence of staghorn
• Prior treatment

32. Internal validation
• 76% predictable accuracy
• But case volume and patient history can make CROES nomogram
cumbersome

33. Seoul National University Renal Stone
Complexity(S-ReSC)

34. • 155 consecutive sPCNL cases from January 2004 through July 2012 at
Seoul National University Bundang Hospital
• Percutaneous access obtained by uroradiologists 1 day before or on
the DOS
• All patients were evaluated with pre and post operative NCCT KUB
• Complete staghorn – filling at least 80% of collecting system
• Partial staghorn – pelvic stone extending to at least 2 calyces

35. • S-ReSC is calculated by counting the number of locations affected by
calculi regardless of stone size, number or composition

36. Reproducibility
• Intra observer reliability by 1 junior faculty member scoring and
rescoring after 1 month blinded
• Inter observer reliability – one senior resident scored what the junior
faculty member scored
• Weighted kappas for intra and inter observer agreement were 0.832
and 0.982

38. Score Author Country Subjects Type of internal
validation
Pre operative
imaging
Post operative
imaging
Stone free
definition
SFR
Guy’s score Thomas et al UK 100 Prospective CT, X ray KUB,
IVU
X ray KUB <4 mm
fragments
62%
S.T.O.N.E score Okunov et al US 117 Prospective NCCT Flouroscopy,
NCCT, YSG
Absence of
stones
80%
CROES Smith A et al Global 2806 Retrospective NCCT KUB, IVU X ray KUB <4 mm
fragments
82%
S-ReSC Jeong CW et al South Korea 155 Retrospective NCCT KUB NCCT KUB Absence of
stones
72.3%

39. Guy’s score S.T.O.N.E score CROES S-ReSC
Strengths  Ease of use  Relies solely on pre
operative CT
 Large multicentric
database
 Easy to use
 No calculations
Weaknesses  Not predictive of
complications
 Partial staghorn not clearly
defined
 Knowledge of stone
unrelated factors
required(spina bifida, spinal
injury)
 Stone size and
number of calyces
involved were
variable
 Cumbersome
 Requires info like
case volume,
patient treatment
history
 Might not be
applicable to
abnormal
collecting systems