The Guy's stone score--grading the complexity of percutaneous nephrolithotomy procedures

Urology. 2011 Aug;78(2):277-81. doi: 10.1016/j.urology.2010.12.026. Epub 2011 Feb 17.

Abstract

Objectives: To report the development and validation of a scoring system, the Guy's stone score, to grade the complexity of percutaneous nephrolithotomy (PCNL). Currently, no standardized method is available to predict the stone-free rate after PCNL.

Methods: The Guy's stone score was developed through a combination of expert opinion, published data review, and iterative testing. It comprises 4 grades: grade I, solitary stone in mid/lower pole or solitary stone in the pelvis with simple anatomy; grade II, solitary stone in upper pole or multiple stones in a patient with simple anatomy or a solitary stone in a patient with abnormal anatomy; grade III, multiple stones in a patient with abnormal anatomy or stones in a caliceal diverticulum or partial staghorn calculus; grade IV, staghorn calculus or any stone in a patient with spina bifida or spinal injury. It was assessed for reproducibility using the kappa coefficient and validated on a prospective database of 100 PCNL procedures performed in a tertiary stone center. The complications were graded using the modified Clavien score. The clinical outcomes were recorded prospectively and assessed with multivariate analysis.

Results: The Guy's stone score was the only factor that significantly and independently predicted the stone-free rate (P = .01). It was found to be reproducible, with good inter-rater agreement (P = .81). None of the other factors tested, including stone burden, operating surgeon, patient weight, age, and comorbidity, correlated with the stone-free rate.

Conclusions: The Guy's stone score accurately predicted the stone-free rate after PCNL. It was easy to use and reproducible.

Publication types

  • Validation Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Kidney Calculi / classification*
  • Kidney Calculi / surgery*
  • Male
  • Middle Aged
  • Nephrostomy, Percutaneous / methods*
  • Prognosis
  • Prospective Studies
  • Severity of Illness Index
  • Young Adult