Fried et al studied factors affecting the conversion of patients from a laparascopic cholecystectomy to an open procedure. Identification of patients who have a significant chance of being converted can help in surgical planning, especially for outpatient procedures. The authors are from McGill University in Quebec.
Parameters associated with increased risk for conversion to an open procedure:
(1) acute cholecystitis
(2) age >= 65 years
(3) obesity
(4) male gender
(5) thickened gallbladder wall on ultrasound
Parameter 
Odds Ratio 
95% Confidence Interval 

acute cholecystitis 
5.79 
3.21 – 10.43 
age >= 65 years 
2.00 
1.15 – 3.49 
obesity 
1.77 
1.02 – 3.05 
male gender 
2.54 
1.48 – 4.37 
thickened gallbladder wall 
1.72 
0.93 – 3.20 
from Table IV, page 37
Method 1: Age as a Continuous Variable:
Parameter 
Finding 
Points 

cholecystitis 
subacute or chronic 
0 

acute 
1 
body weight 
not obese 
0 

obese 
1 
gender 
female 
0 

male 
1 
gallbladder wall 
not thickened 
0 

thickened 
1 
probability of conversion =
= EXP(X) / (1 + EXP(X))
X = (0.0248 * (age in years)) + (0.8925 * (points for sex)) + (1.7764 * (points for acute disease)) + (0.5589 * (points for obesity)) + (0.5294 * (points for thickened wall)) – 5.7924
Method 2: Age as a Dichotomous Variable
age >= 65 
acute? 
sex 
obese? 
thickened? 
Percent Convert 

N 
N 
F 
N 
N 
0.9% 
N 
N 
F 
N 
Y 
1.6% 
N 
N 
F 
Y 
N 
1.6% 
N 
N 
F 
Y 
Y 
2.7% 
N 
N 
M 
N 
N 
2.3% 
N 
N 
M 
N 
Y 
3.9% 
N 
N 
M 
Y 
N 
4.0% 
N 
N 
M 
Y 
Y 
6.7% 
N 
Y 
F 
N 
N 
5.1% 
N 
Y 
F 
N 
Y 
8.4% 
N 
Y 
F 
Y 
N 
8.6% 
N 
Y 
F 
Y 
Y 
14.0% 
N 
Y 
M 
N 
N 
12.0% 
N 
Y 
M 
N 
Y 
19.0% 
N 
Y 
M 
Y 
N 
19.4% 
N 
Y 
M 
Y 
Y 
29.2% 
Y 
N 
F 
N 
N 
1.8% 
Y 
N 
F 
N 
Y 
3.1% 
Y 
N 
F 
Y 
N 
3.2% 
Y 
N 
F 
Y 
Y 
5.3% 
Y 
N 
M 
N 
N 
4.5% 
Y 
N 
M 
N 
Y 
7.5% 
Y 
N 
M 
Y 
N 
7.7% 
Y 
N 
M 
Y 
Y 
12.5% 
Y 
Y 
F 
N 
N 
9.7% 
Y 
Y 
F 
N 
Y 
15.6% 
Y 
Y 
F 
Y 
N 
15.9% 
Y 
Y 
F 
Y 
Y 
24.8% 
Y 
Y 
M 
N 
N 
21.4% 
Y 
Y 
M 
N 
Y 
31.9% 
Y 
Y 
M 
Y 
N 
32.5% 
Y 
Y 
M 
Y 
Y 
45.3% 
from Table III, page 37
Specialty: Gastroenterology, Surgery, general
ICD10: ,