Table 1.
Patient demographics, comorbidities and index operation details
| Original | Matched | |||||
|---|---|---|---|---|---|---|
| High-volume hospital (n = 214) n (%) or median (i.q.r.) |
Low-volume hospital (n = 168) n (%) or median (i.q.r.) |
SMD before matching | High-volume hospital (n = 142) n (%) or median (i.q.r.) |
Low-volume hospital (n = 142) n (%) or median (i.q.r.) |
SMD after matching | |
| Sex | ||||||
| Male | 138 (63.6) | 109 (64.9) | 0.200 | 87 (61.3) | 90 (63.4) | 0.043 |
| Female | 78 (36.4) | 59 (35.1) | 55 (38.8) | 52 (36.7) | ||
| Age (years) | 68.4 (56.9–75.4) | 65.1 (57.1–74.3) | 0.052 | 67.2 (56.2–74.5) | 64.7 (57.1–74.9) | 0.021 |
| BMI (kg/m2) | 25.3 (22.4–29.0) | 26.8 (23.8–29.8) | 0.273 | 25.6 (23.0–30.0) | 26.7 (23.7–29.7) | 0.066 |
| Current smoker | 23 (10.7) | 19 (11.3) | 0.018 | 15 (10.6) | 18 (12.7) | 0.066 |
| Medication | ||||||
| Anticoagulation | 40 (18.7) | 23 (13.7) | 0.135 | 19 (13.4) | 22 (15.5) | 0.060 |
| Immunosuppressants | 13 (6.1) | 6 (3.6) | 0.115 | 4 (2.8) | 5 (3.5) | 0.040 |
| Corticosteroids | 12 (5.6) | 8 (4.8) | 0.153 | 8 (5.6) | 7 (4.9) | 0.031 |
| Previous abdominal operations | 95 (44.4) | 58 (34.5) | 0.202 | 60 (42.3) | 50 (35.2) | 0.152 |
| Charlson Comorbidity Index | 4 (0–6) | 4 (0–6) | 0.048 | 3 (0–6) | 4 (0–6) | 0.056 |
| Atrial fibrillation | 31 (14.5) | 18 (10.7) | 0.113 | 20 (14.1) | 18 (12.7) | 0.041 |
| Ischaemic heart disease | 34 (1.4) | 20 (11.9) | 0.114 | 17 (12.0) | 16 (11.3) | 0.022 |
| Myocardial infarct | 21 (9.8) | 9 (5.4) | 0.168 | 10 (7.0) | 5 (3.5) | 0.157 |
| Congestive heart failure | 31 (14.5) | 16 (9.5) | 0.151 | 13 (9.2) | 14 (5.6) | 0.024 |
| Peripheral vascular disease | 14 (6.5) | 5 (3.0) | 0.164 | 5 (3.5) | 5 (3.5) | 0.000 |
| Dementia | 7 (3.3) | 3 (1.8) | 0.093 | 2 (1.4) | 3 (2.1) | 0.053 |
| Cerebrovascular accident/transient ischaemic attack | 17 (7.9) | 9 (5.4) | 0.103 | 6 (4.2) | 8 (5.6) | 0.065 |
| Chronic obstructive pulmonary disease | 18 (8.4) | 6 (3.6) | 0.200 | 5 (3.5) | 6 (4.2) | 0.036 |
| Connective tissue disease | 9 (4.2) | 9 (5.4) | 0.054 | 6 (4.2) | 7 (4.9) | 0.034 |
| Diabetes mellitus | 34 (15.9) | 23 (13.7) | 0.070 | 19 (13.4) | 18 (12.7) | 0.021 |
| Peptic ulcer | 6 (2.8) | 3 (1.8) | 0.067 | 4 (2.8) | 3 (2.1) | 0.045 |
| Liver disease | 7 (3.3) | 2 (1.2) | 0.137 | 4 (2.8) | 2 (1.4) | 0.098 |
| Hemiplegia | 11 (5.1) | 3 (1.8) | 0.179 | 3 (2.1) | 2 (1.4) | 0.053 |
| Solid tumour, local | 95 (44.4) | 81 (48.2) | 0.077 | 62 (43.7) | 65 (45.8) | 0.042 |
| Solid tumour, metastatic | 19 (8.9) | 15 (8.9) | 0.002 | 13 (9.2) | 13 (9.2) | 0.000 |
| Leukaemia | 2 (0.9) | 1 (0.6) | 0.038 | 1 (0.7) | 1 (0.7) | 0.000 |
| Lymphoma | 2 (0.9) | 3 (1.9) | 0.075 | 1 (0.7) | 2 (1.4) | 0.069 |
| Acquired immune deficiency syndrome | 0 | 0 | – | 0 | 0 | |
| Chronic kidney disease | 12 (5.6) | 4 (2.4) | 0.161 | 5 (3.5) | 4 (2.8) | 0.040 |
| Previous thrombosis | 16 (7.5) | 6 (3.6) | 0.168 | 8 (5.6) | 5 (3.5) | 0.101 |
| Surgical approach | ||||||
| Laparoscopy | 112 (52.3) | 65 (38.7) | 0.275 | 79 (55.6) | 58 (40.8) | 0.298 |
| Open | 71 (33.2) | 74 (44.1)) | 0.225 | 43 (30.3) | 59 (41.5) | 0.236 |
| Converted | 31 (14.5) | 29 (17.3) | 0.076 | 20 (14.1) | 25 (17.6) | 0.096 |
| Operating time (min)* | 140 (112–189) | 154 (114.0–211.3) | 0.002 | 138.0 (112.0–189.0) | 154 (110–206) | 0.004 |
| Blood loss (ml)† | 150 (50–400) | 150 (75–350) | 0.001 | 100 (50–400) | 150 (50–350) | 0.026 |
| Reason for surgery | ||||||
| Colorectal cancer or premalignant lesion | 134 (62.6) | 111 (66.1) | 0.072 | 88 (62.0) | 91 (64.1) | 0.044 |
| Diverticulosis | 49 (22.9) | 41 (24.4) | 0.035 | 38 (26.8) | 35 (24.6) | 0.048 |
| Benign large bowel obstruction | 10 (4.7) | 4 (2.4) | 0.087 | 5 (3.5) | 5(3.5) | 0.000 |
| Inflammatory bowel disease | 13 (6.1) | 6 (3.6) | 0.115 | 5 (3.5) | 6 (4.2) | 0.036 |
| Other malignancy | 3 (1.4) | 3 (1.8) | 0.006 | 3 (2.1) | 3 (2.1) | 0.000 |
| Other resection ‡ | 5 (2.3) | 3 (1.8) | 0.054 | 3 (2.1) | 3 (2.1) | 0.053 |
| Right-sided colectomy | 79 (36.9) | 55 (32.7) | 0.087 | 48 (36.6) | 50 (35.2) | 0.030 |
| Left-sided colectomy | 104 (48.6) | 92 (54.8) | 0.111 | 77 (54.2) | 73 (51.4) | 0.042 |
| Rectal resection | 26 (12.1) | 12 (7.1) | 0.125 | 9 (6.3) | 10 (7.0) | 0.028 |
| Subtotal colectomy | 10 (4.7) | 12 (7.1) | 0.106 | 8 (5.6) | 9 (6.3) | 0.030 |
| Faecal contamination | 15 (7.0) | 12 (7.1) | 0.009 | 9 (6.3) | 8 (5.6) | 0.026 |
| Primary anastomosis | 211 (98.6) | 166 (98.8) | 0.019 | 141 (99.3) | 140 (98.6) | 0.069 |
| Protective diversion | 15 (7.0) | 6 (3.6) | 0.133 | 5 (3.5) | 5 (3.5) | 0.000 |
*Seventeen patients were missing data for operating time (10 in low-volume hospitals (LVHs) and 7 in high-volume hospitals (HVHs)). †Forty-five patients were missing data for blood loss (19 in LVHs and 26 in HVHs). ‡Other: iatrogenic lesion, n = 1; trauma, n = 1; endometriosis, n = 1; rectum prolapse, n = 1; hidradenitis, n = 1; polyposis, n = 2; other infection, n = 1; other benign lesion, n = 1. SMD, standardized mean difference.