Xiao et al reported a preoperative scoring system for evaluating a patient prior to renal stone removal by retrograde intrarenal surgery. This can help to identify cases that may pose problems for stone clearance. The authors are from Nanjing Medical University
RIRS refers to retrograde intrarenal surgery.
RIRS also is an acronym for renal stone density (R), inferior pole (I), RIL (R) and stone diameter (S)
Parameters:
(1) renal stone density in Hounsfield Units
(2) stone location
(3) distance from the most distal point at bottom stone-containing calix to midpoint of lip of renal pelvis (RIL)
(4) stone burden as cumulative stone diameter in mm
Parameter
Finding
Points
renal stone density
<= 1,000 HU
1
> 1,000 HU
2
stone location
not in inferior pole
1
inferior pole with RIPA > 30 degrees
2
inferior pole with RIPA <= 30 degrees
3
RIL
<= 25 mm
1
> 25 mm
2
cumulative stone diameter
<= 10 mm
1
10.1 to 20 mm
2
> 20 mm
3
where:
• RIPA = renal infundibulopelvic angle
total score =
= SUM(points for all of the parameters)
Interpretation:
• minimum score: 4
• maximum score: 10
• The higher the score the greater the complexity of the situation.
Score
Complexity Group
Stone-Free
4 or 5
mild
99 to 100%
6 to 8
moderate
42 to 92%
9 or 10
severe
0 to 20%
Performance:
• The area under the ROC curve is 0.90.
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