Table 1 Variables with significant differences between study groups as identified in nonparametric, univariable analysis. Odds ratio and 95% confidence interval calculated using univariable logistic regression. For rectal exam results, a univariable analysis of association for each type of rectal finding is included

Season at presentation^a

0.001

 Spring/Summer

41 (38)

2 (10)

Reference variable

 Autumn

36 (34)

3 (15)

1.7

0.3–13.5

 Winter

30 (28)

15 (75)

10.2

2.6–68.2

Colic at admission^a

0.02

 No colic at admission

30 (28)

4 (20)

Reference variable

 Colic grade at admission

 Grade 1

67 (63)

12 (60)

1.50

0.48–5.67

 Grade 2

8 (7)

0 (0)

N/A

N/A

 Grade 3

2 (2)

4 (20)

17.50

2.62–161.78

Fever at admission (≥ 38.5 ℃)^a

0.03

 No fever at admission

53 (50)

4 (20)

Reference variable

 Fever at admission

52 (49)

16 (80)

0.3

0.1–0.8

 Missing

2

0

Rectal examination^a

 < 0.001

 Normal rectal exam

54 (51)

1 (5)

Reference variable

 One or several rectal findings

53 (49)

19 (95)

19.4

3.8–354.0

 Mass/adhesions

0 (0)

13 (65)

Part of case definition

 Impaction

44 (41)

9 (45)

1.2

0.4–3.1

 Gas distention

7 (7)

4 (20)

3.6

0.9–13.3

 Other abnormal finding

4 (4)

1 (5)

1.4

0.0–9.8

WBC (median [IQR])^b

7.10 [5.54, 9.30] × 10⁹/L

3.50 [3.05, 5.01] × 10⁹/L

 < 0.001

0.04^†

0.28–0.64

 Missing

6

5

Neutrophils (median [IQR])^b

5.00 [3.60, 7.10] × 10⁹/L

2.40 [1.40, 3.19] × 10⁹/L

 < 0.001

0.55^†

0.38–0.75

 Missing

7

4

Elevated fibrinogen level^a

13 (16)

8 (53)

0.01

4.70

1.28–17.19

 Missing

23

5

Peritoneal total protein level (median [IQR])^b

40.00 [34.00, 50.00] g/L

50.00 [40.00, 60.00] g/L

0.01

1.38^‡

1.10–1.78

 Missing

16

3