Table 1. Patient Characteristics by Type of Procedure and Regional Use of Laparoscopy.
| Variable | Type of Procedure | Regional Use of Laparoscopya | ||||
|---|---|---|---|---|---|---|
| Laparoscopic Surgery (n = 133 528) |
Open Surgery (n = 295 271) |
Absolute Standardized Differenceb | <Median (n = 207 976) |
>Median (n = 220 823) |
Absolute Standardized Differenceb | |
| Age, y | ||||||
| Mean (SD) | 74 (10) | 73 (8) | 6.8 | 73 (9) | 74 (9) | 3.6 |
| Median (IQR) | 75 (14) | 73 (12) | 74 (13) | 74 (13) | ||
| Race, No. (%) | ||||||
| White | 115 575 (86.6) | 252 772 (85.6) | 8.6 | 181 815 (87.4) | 186 529 (84.5) | 2.9 |
| Black | 11 706 (8.8) | 29 698 (10.1) | 6.1 | 18 148 (8.7) | 23 256 (10.5) | 4.4 |
| Comorbidities | ||||||
| Mean (SD) | 2 (2) | 3 (2) | 28.1 | 2 (2) | 2 (2) | 3.8 |
| Median (IQR) | 2 (2) | 2 (3) | 2 (2) | 2 (2) | ||
| Hospital length of stay, median (IQR), d | 5 (3) | 8 (7) | 47.6 | 7 (7) | 7 (7) | 2.2 |
| Specific comorbidities, No. (%) | ||||||
| Congestive heart failure | 8591 (6.4) | 31 235 (10.6) | 14.9 | 19 063 (9.2) | 20 763 (9.4) | 1.0 |
| Pulmonary circulatory disease | 2427 (1.8) | 8151 (2.8) | 6.3 | 5182 (2.5) | 5396 (2.4) | 1.0 |
| Type 2 diabetes | 26 497 (19.8) | 55 351 (18.7) | 2.7 | 39 173 (18.8) | 42 675 (19.3) | 1.2 |
| Type 2 diabetes with complications | 2857 (2.1) | 6630 (2.2) | 1.0 | 4646 (2.2) | 4841 (2.2) | 1.0 |
| Liver disease | 1852 (1.4) | 4310 (1.5) | 1.0 | 3013 (1.4) | 3149 (1.4) | 1.0 |
| Renal failure | 8550 (6.4) | 26 522 (9.0) | 9.7 | 17 094 (8.2) | 17 978 (8.1) | 1.2 |
| Metastatic cancer | 13 916 (10.4) | 47 544 (16.1) | 16.8 | 29 276 (14.1) | 32 184 (14.6) | 1.4 |
| Obesity | 11 184 (8.4) | 22 888 (7.8) | 3.3 | 17 488 (8.4) | 16 584 (7.5) | 2.2 |
| Depression | 8835 (6.6) | 19 524 (6.6) | 1.8 | 14 236 (6.8) | 14 123 (6.4) | 1.0 |
| Operative diagnosis, No. (%) | ||||||
| Cancer | 63 278 (47.4) | 119 908 (40.6) | 13.7 | 86 820 (41.7) | 96 366 (43.6) | 3.8 |
| Diverticular disease | 18 456 (13.8) | 76 613 (25.9) | 30.7 | 44 703 (21.5) | 50 371 (22.8) | 3.1 |
| Inflammatory bowel disease | 1821 (1.4) | 11 235 (3.8) | 15.4 | 7104 (3.4) | 5949 (2.7) | 4.1 |
| Elective procedure, No. (%) | 106 565 (79.8) | 144 061 (48.8) | 47.6 | 130 032 (62.5) | 120 590 (54.6) | 8.5 |
| Postoperative events, No. (%) | ||||||
| Complications | 17 915 (13.4) | 90 842 (30.8) | 36.9 | 50 361 (24.2) | 58 396 (26.4) | 4.4 |
| Death within 30 d | 2193 (1.6) | 23 074 (7.8) | 28.3 | 10 926 (5.3) | 14 341 (6.5) | 5.1 |
| Unadjusted total episode payments, US $ | 16 255 | 25 778 | 33.1 | 21 706 | 23 855 | 6.7 |
Abbreviation: IQR, interquartile range.
a
Regional use of laparoscopy, the instrumental variable, is the proportion of colectomies performed laparoscopically within a hospital referral region in a given year, excluding the hospital in which the specific beneficiary had his or her operation.
b
See the Statistical Analysis subsection of the Methods section for a detailed explanation. An absolute standardized difference exceeding 10 suggests statistically significant imbalance of a covariate.