Guy’s Stone Score (PCNL Complexity)
Guy's stone score (Grade I–IV) for percutaneous-nephrolithotomy complexity, with the expected stone-free rate by grade.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Stone configuration / anatomy grade
- 4
Result: Guy's stone score Grade IV — expected stone-free rate ~29% (staghorn calculus, or any stone with spina bifida / spinal injury).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Grades
- I lower-pole/pelvic stone (~81%); II upper-pole/multiple/abnormal stone (~72%); III abnormal-anatomy multiple, diverticulum, or partial staghorn (~35%); IV staghorn or spinal injury (~29%).
- Use
- grades PCNL complexity; a complement to S.T.O.N.E. nephrolithometry. Higher grade predicts a lower stone-free rate.
What you enter
- Stone configuration / anatomy grade (1–4)
How this is calculated
Thomas K, Smith NC, Hegarty N, Glass JM. The Guy's stone score — grading the complexity of percutaneous nephrolithotomy procedures. Urology. 2011;78(2):277-281. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.