Table 1.

Current Nephrolithometric Scoring Systems

Scoring System	Categorization	Method of Derivation
Guy’s Stone Scorea	Grade I: A solitary stone in the mid/lower pole, or renal pelvis with simple anatomy	Literature review
	Grade II: A solitary stone in the upper pole with simple anatomy, multiple stones in a patient with simple anatomy, or any solitary stone in a patient with abnormal anatomy	Expert opinion
	Grade III: Multiple stones in a patient with abnormal anatomy, stones in a calyceal diverticulum, or partial staghorn calculus	Iterative process
	Grade IV: Staghorn calculus or any stone in a patient with spina bifida or spinal injury
Nephrolithometric Nomogramb	A: Stone Burden — calculated as follows:	Multiple logistic regression analysis
	1. Measure the maximum length of each stone in millimeters
	2. Measure the maximum width of each stone in millimeters
	3. Calculate the stone burden for each stone = 0.785 × length × width
	4. Add individual stone burdens if multiple stones
	B: Calyceal location — position in renal pelvis or multiple calyces involved, including staghorn calculi
	C: Stone count — single or multiple
	D: Case volume
S.T.O.N.E. Nephro-lithometryc	Scoring based on 5 variables from preoperative noncontrast computed tomography stone size:	Systematic review
	S = stone size
	1: 0–399 mm2
	2: 400–799 mm2
	3: 800–1599 mm2
	4: > 1600 mm2
	T = tract length
	1: < 100 mm
	2: > 100 mm
	O = Obstruction
	1: no or mild dilatation
	2: moderate to severe dilatation
	N = Number of involved calyces
	1: 1 calyx involved
	2: 2–3 calyces involved
	3: full staghorn calculus
	E = Essence (stone density)
	1: < 950 HU
	2: > 950 HU
Seoul Renal Stone Complexity Scored	Identify number of preselected pelvicalyceal locations involved, each of the 9 locations is worth 1 point; total score = cumulative number of locations involved	Not reported

^aFrom Thomas K et al.⁷

^bFrom Smith A et al.⁸

^cFrom Okhunov Z et al.⁹

^dFrom Jeong CW et al.¹⁰