Miller and Kane developed an equation to predict the number of days for a renal stone to pass. This can help a physician and patient decide which therapeutic option to pursue. The authors are from the Naval Medical Center in San Diego, California.
Parameters:
(1) size in mm
(2) position
(3) side of body
Parameter
Finding
Points
size
<= 1 mm
1
2 mm
2
3 mm
3
>=4 mm
4
position
proximal ureter
1
mid ureter
2
distal ureter
3
side
left
1
right
2
where:
• The size of the stone will be rounded to the nearest mm if > 1 or < 4 mm in the implementation.
• Large stones (4-6 mm) were cleared more rapidly on the right side.
• The authors noted that intervention was required in 50% of patients with stones > 5 mm in diameter.
predicted number of days to stone passage =
= 20.21 + (5.01 * (points for size)) - (4.23 * (points for position)) - (7.25 * (points for side))
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