This cohort study investigates the development of morbidity and mortality after major abdominal surgery over 2 decades in Denmark.
Key Points
Question
How did morbidity and mortality after major emergency abdominal surgery develop over 2 decades in Denmark?
Findings
In this nationwide register-based study that included 61 476 patients undergoing major emergency abdominal surgery from 2002 to 2022, 30- and 90-day mortality rates significantly decreased. However, readmission rates drastically increased, and the rate of postoperative complications remained high.
Meaning
Results suggest that, although advances in surgical and perioperative care have reduced mortality, the significantly increased readmission rate and persistently high rate of postoperative complications underscore the need for improved postoperative follow-up.
Abstract
Importance
Major emergency abdominal surgery is associated with high morbidity and mortality. Understanding trends in outcomes over time can reveal critical practice-changing improvements, identify gaps in postoperative care, and establish a large-scale benchmark for future research.
Objective
To investigate trends in morbidity and mortality after major emergency abdominal surgery in Denmark.
Design, Setting, and Participants
This was a nationwide, population-based cohort study. Analyses were performed based on data from Danish nationwide administrative registries. Within the public health care system in Denmark, all adult patients undergoing major emergency abdominal surgery from 2002 to 2022 were included. Major emergency abdominal surgeries included laparotomy or laparoscopy due to intra-abdominal pathologies, including intestinal perforation, ischemia, bowel obstruction, abscess, or bleeding.
Exposure
Major emergency abdominal surgery.
Main Outcomes and Measures
The primary outcome was the trend in 30- and 90-day mortality after major emergency abdominal surgery over time.
Results
A total of 61 476 patients (mean [SD] age, 66.2 [16.3] years; 34 827 female [56.7%]) were included. The annual number of surgeries remained constant, with a mean (SD) of 3044 (165) surgeries per year. The 30- and 90-day mortality was reduced from 25% and 33%, respectively, to 13% and 18%, respectively (P < .001). Median (IQR) hospital length of stay was decreased from 10 (5-17) days to 6 (4-13) days (P < .001). The rate of 30-day postoperative complications (classified Clavien-Dindo ≥3a) was reduced from 49% to 44% (P <.001) and the 90-day rate was reduced from 53% to 48% (P <.001), however, with a tendency toward more patients undergoing earlier intervention. The 30- and 90-day readmission rate increased drastically from 9% and 13%, respectively, to 25% and 33%, respectively (P < .001).
Conclusions and Relevance
Results of this cohort study suggest notable reductions in mortality and hospital length of stay after major emergency abdominal surgery. A marked increased readmission rate and a persistently high rate of postoperative complications were found. These shifts underscore the need for enhanced postoperative monitoring and postdischarge follow-up.
Introduction
Major emergency abdominal surgery (MEAS) is frequently performed across various settings and indications.1,2 In 2011, the rate of emergency surgery in England was 1 per 1100 individuals.3 The procedures are associated with a high risk of complications and considerable mortality.4
Outcomes for patients undergoing MEAS are influenced by various factors, including patient characteristics, disease-specific factors, and factors related to perioperative management.5,6,7,8 Recently, shifts in treating high-risk surgical patients have been observed internationally. The introduction of preoperative care bundles has accelerated diagnostics, optimized treatment initiation, and expedited surgery.9,10,11,12,13 Laparoscopic procedures have been introduced and deemed safe in emergency surgery.14 Treating patients with various conditions, such as perforated peptic ulcer, perforated diverticulitis, and small bowel obstruction, using laparoscopy is now possible and is associated with faster recovery and shorter hospital length of stay (LOS).15,16,17 Risk scores, such as the National Emergency Laparotomy Audit (NELA), the Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity (P-POSSUM), and Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT), enable more individualized treatment strategies based on patient- and disease-specific factors.18,19,20 Furthermore, enhanced recovery protocols after MEAS have been successfully implemented.21 In frail patients with significant comorbidities and where the surgical stress response may outweigh their physiological reserves, conservative management is increasingly favored over surgery.22
These factors are expected to have influenced the selection and treatment of patients undergoing MEAS over time. It is hypothesized that these changes have led to a shift in morbidity and mortality rates.
This study aimed to identify pivotal shifts in surgical practice, uncover gaps in postoperative care and follow-up, and establish a comprehensive benchmark for future research by investigating nationwide trends in morbidity and mortality related to MEAS in Denmark over the past 2 decades.
Methods
Setting
This nationwide register-based study was conducted in Denmark, a country with a population of approximately 5.8 million inhabitants. MEAS is exclusively performed in public hospitals with acute care facilities. In Denmark, emergent and nonemergent health care services are tax funded for all citizens. All Danish citizens are assigned a unique Civil Registration Number (CRN) at birth or immigration, enabling the identification of hospital contacts, diagnoses, and surgical procedures for all individuals included in the study.23
The study was approved by the regional Data Protection Agency. Data access was approved and maintained by Statistics Denmark (project No. 709637). In Denmark, register-based studies do not require approval from research ethics committees or patient consents. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guidelines.24
Data Sources and Classifications
Data were prospectively collected through Danish national health registries. The Danish National Patient Registry (NPR)25 was used to identify the index and subsequent procedures, diagnoses, and readmissions. Diagnoses were registered according to the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes. Surgical procedures were registered according to the Nordic Medico-Statistical Committee (NOMESCO) Classification of Surgical Procedures (NCSP). Both private and public health care practitioners in Denmark are required to register diagnosis and procedures codes. In 2019, the NPR was restructured, and the new validated research-oriented data model was launched in 2022. The restructuring did not alter the reporting or quality of the covariates used in this study. The Charlson Comorbidity Index (CCI) was calculated from NPR data and was categorized into 3 groups: 0 to 1, 2 to 3, or greater than or equal to 4.26 The lookback period was minimum 2 years.
The Civil Registration System27 provided information on patient mortality during the follow-up period. Information regarding the general Danish population’s yearly development was publicly available through the Danish Mobile Statbank.28
Study Population
The study population included all adults (18 years and older) who underwent MEAS between January 1, 2002, and September 31, 2022. MEAS was defined as laparotomy or laparoscopy for intra-abdominal pathologies, including intestinal perforation, ischemia, bowel obstruction, abscess, or bleeding. The Danish Acute Surgery Database29 developed the register-based definition of MEAS in collaboration with the Board of Emergency, Trauma, and Hernia Surgery under the Danish Surgical Society. Patients were included in case of a relevant ICD-10 diagnosis code linked with a relevant NCSP code, as listed in eTable 1 in Supplement 1. Patients with traumatic injuries, appendicitis, cholecystitis, or other hepatic-pancreatic-biliary procedures were not included in the algorithm. In cases where multiple procedures occurred within 90 days, only the first procedure was included and was considered the index procedure. Outpatient procedures and patients without a valid CRN number were excluded. Participant race and ethnicity information was not gathered. All health care, both inpatient and outpatient, is tax funded in Denmark, and there are no differences in health care access or the quality of health care based on ethnicity. Therefore, ethnicity is not registered in administrative registry data.
Outcomes
The primary outcome was the 30- and 90-day mortality trend after MEAS. Secondary outcomes included LOS and the 30- and 90-day incidences of postoperative complications and readmissions.
Postoperative complications were classified according to the Clavien-Dindo (CD) classification.30 Complications graded CD 1-2 could not be assessed from the available data. CD 3a complications were defined as minor procedures expected to be performed without general anesthesia (eg, drainage of collections, endoscopic procedures, and minor endovascular interventions). CD 3b complications were defined as surgical procedures generally performed under general anesthesia. The need for intensive care was defined by admission to an intensive care unit (ICU) during the follow-up period. Distinguishing between single-organ and multiorgan failure was not possible with the available data. Readmissions were defined as any emergency admission occurring 1 or more days after discharge.
Statistical Analysis
Categorical data are presented as numbers and percentages. Continuous data were examined by plotting histograms and q-q plots, and they are presented with mean or median and SD or IQR. Due to variance in time of risk due to differences in LOS, readmission is presented as the number of patients readmitted and the cumulative incidence proportion.
Patients were categorized into 4 groups based on the timing of the index surgery: 2002 to 2006, 2007 to 2011, 2012 to 2016, and 2017 to 2022. The Kaplan-Meier estimator was used to assess all-cause 30- and 90-day mortality after index surgery, with the log-rank test used for group comparisons. Cumulative incidences of postoperative complications (CD ≥3a) and readmissions were calculated and plotted with adjustment for the competing risk of death (Aalen-Johansen estimator). The Fine and Gray test was used for group comparisons. Multivariate logistic regression models were performed to evaluate risk factors for mortality, postoperative complications (CD ≥3a), and readmissions. Models were adjusted for sex, age, CCI, year of surgery, indication, and type of surgery. Results were presented as odds ratios (ORs) with 95% CIs. Two-sided P values <.05 were considered statistically significant. The register-based design ensured no missing data.
Data analyses were performed using SAS, version 9.4 (SAS Institute). Plots were created using R, version 4.4.1 (R Foundation for Statistical Computing).
Results
A total of 61 476 patients (mean [SD] age, 66.2 [16.3] years; 34 827 female [56.7%]; 26 649 male [45.4%]) were included. The annual number of MEASs remained stable throughout the study period, with a mean (SD) of 3044 (165) index surgeries (52 surgeries per 100 000 inhabitants per year). eTable 2 in Supplement 1 provides the number of index procedures per year throughout the study period.
Patient and Procedure Characteristics
The patients and procedure characteristics are available in Table 1 and elaborated in eTable 3 in Supplement 1. A slight, statistically significant increase in the proportion of male patients over time was observed (2002-2006, 5707 of 13 869 [41.2%] vs 2017-2022, 7879 of 13 869 [45.7%]; P < .001). A total of 69% of the patients (42 641 of 61 476) were 60 years or older, and 22% to 25% (13 749 of 61 476) had a CCI score of CCI of 2 or greater. A significant increase, from 16.8% in 2002 to 2006 to 22.5% in 2017 to 2022, was observed in the proportion of patients with CCI of 2 or greater throughout the study period (P < .001). No significant change in age was observed.
Table 1. Patient and Procedure Characteristics.
| Characteristic | Overall (N = 61 476) | Subgroups according to year of surgery | |||
|---|---|---|---|---|---|
| 2002-2006 (n = 13 869) | 2007-2011 (n = 14 793) | 2012-2016 (n = 15 554) | 2017-2022 (n = 17 260) | ||
| Sex, No. (%) | |||||
| Female | 34 827 (56.7) | 8162 (58.9) | 8468 (57.2) | 8816 (56.7) | 9381 (54.4) |
| Male | 26 649 (45.4) | 5707 (41.2) | 6325 (42.8) | 6738 (43.3) | 7879 (45.7) |
| Age, No. (%), y | |||||
| <50 | 10 233 (16.7) | 2144 (15.5) | 2464 (16.7) | 2978 (19.2) | 2647 (15.3) |
| 50-59 | 8602 (14.0) | 2119 (15.3) | 1974 (13.3) | 2116 (13.6) | 2393 (13.9) |
| 60-69 | 12 723 (20.7) | 2690 (19.4) | 3300 (22.3) | 3353 (21.6) | 3380 (19.6) |
| 70-79 | 16 173 (26.3) | 3528 (25.4) | 3658 (24.7) | 3881 (25.0) | 5106 (29.6) |
| ≥80 | 13 745 (22.4) | 3388 (24.4) | 3397 (23.0) | 3226 (20.7) | 3734 (21.6) |
| CCI, No. (%) | |||||
| 0-1 | 47 727 (77.6) | 11 540 (83.2) | 11 241 (76.0) | 11 534 (74.2) | 13 412 (77.7) |
| 2-3 | 11 533 (18.8) | 2080 (15.0) | 2971 (20.1) | 3238 (20.8) | 3244 (18.8) |
| ≥4 | 2216 (3.6) | 249 (1.8) | 581 (3.9) | 782 (5.0) | 604 (3.5) |
| Indication for surgery, No. (%) | |||||
| Perforation | 20 684 (33.7) | 5737 (41.4) | 5538 (37.4) | 4642 (29.8) | 4767 (27.6) |
| Ischemia | 3748 (6.1) | 892 (6.4) | 901 (6.1) | 926 (6.0) | 1029 (6.0) |
| Bowel obstruction | 39 105 (63.6) | 7731 (55.7) | 8945 (60.5) | 10 478 (67.4) | 11 951 (69.2) |
| Bleeding | 674 (1.10) | 242 (1.7) | 210 (1.4) | 136 (0.87) | 86 (0.50) |
| Type of surgery, No. (%) | |||||
| Laparoscopic | 8467 (13.8) | 345 (2.5) | 1268 (8.6) | 2771 (17.8) | 4083 (23.7) |
| Open | 53 009 (86.2) | 13 524 (97.5) | 13 525 (91.4) | 12 783 (82.2) | 13 177 (76.3) |
| Bowel resection, No. (%) | |||||
| Small bowel | 5369 (8.7) | 1254 (9.0) | 1420 (9.6) | 1373 (8.8) | 1322 (7.7) |
| Colon | 7008 (11.4) | 1612 (11.6) | 1969 (13.3) | 1855 (11.9) | 1572 (9.1) |
| Unspecified | 172 (0.28) | 19 (0.14) | 24 (0.16) | 45 (0.29) | 84 (0.49) |
| None | 49 073 (79.8) | 11 019 (79.5) | 11 419 (77.2) | 12 331 (79.3) | 14 304 (82.9) |
| Creation of stoma, No. (%) | 10 489 (17.1) | 2667 (19.2) | 2623 (17.7) | 2590 (16.7) | 2609 (15.1) |
Abbreviation: CCI, Charlson Comorbidity Index.
The number of patients undergoing laparoscopic procedures increased significantly from 2.5% (345 of 13 869) in the 2002 to 2006 period to 23.7% (4084 of 13 869) in the 2017 to 2022 period. The primary indications for surgery were bowel obstruction and intestinal perforation. The percentage of surgeries due to bowel obstruction increased from 55.7% (7731 of 13 869) in the 2002 to 2006 period to 69.2% (11 951 of 13 869) in the 2017 to 2022 period, whereas surgeries due to intestinal perforation decreased from 41.4% (5737 of 13 869) to 27.6% (4767 of 13 869), respectively. The number of surgeries due to ischemia or bleeding remained stable throughout the study period. The number of bowel resections and stoma creations remained relatively constant throughout the study period.
Mortality
The all-cause mortality rate decreased significantly over the study period. Thirty-day mortality decreased from 25% in the 2002 to 2006 period to 13% in the 2017 to 2022 period (P < .001), whereas 90-day mortality decreased from 31% to 18% over the same period. A significant decline was explicitly observed between 2008 and 2013, where the 30-day mortality dropped from 24% to 14%, and the 90-day mortality likewise decreased from 29% to 19%.
The results are available in Table 2 and elaborated in eTable 4 in Supplement 1. The eFigure in Supplement 1 depicts the yearly mortality trend, and Figure 1 depicts the Kaplan-Meier curve distinguishing the risk according to the year of surgery.
Table 2. Postoperative Outcomes and Complications Within 30 and 90 Days After Primary Major Emergency Abdominal Surgery.
| Outcome | Overall (N = 61 476) | Subgroups according to year of surgery | |||
|---|---|---|---|---|---|
| 2002-2006 (n = 13 869) | 2007-2011 (n = 14 793) | 2012-2016 (n = 15 554) | 2017-2022 (n = 17 260) | ||
| LOS, median (IQR), d | 7 (4-14) | 10 (5-17) | 9 (5-15) | 7 (4-13) | 6 (2-10) |
| LOS, No. (%) | |||||
| <7 d | 26 876 (43.7) | 4549 (32.8) | 5331 (36.4) | 7462 (46.7) | 9734 (56.4) |
| ≥7 d | 34 600 (56.3) | 9320 (67.2) | 9462 (64.0) | 8292 (53.3) | 7526 (43.6) |
| Readmission, No. (CIP) | |||||
| 30 d | 9148 (14.9) | 269 (9.1) | 1550 (10.5) | 2060 (13.2) | 4269 (24.7) |
| 90 d | 12 519 (20.4) | 1824 (13.2) | 2172 (14.7) | 2831 (18.2) | 5692 (33.0) |
| CD 3a, No. (%) | |||||
| 30 d | 8689 (14.1) | 1462 (10.5) | 1986 (13.4) | 2243 (14.4) | 2998 (17.4) |
| 90 d | 11 346 (18.5) | 1894 (13.7) | 2486 (16.8) | 3180 (20.4) | 3786 (21.9) |
| CD 3b, No. (%) | |||||
| 30 d | 12 684 (20.6) | 2983 (21.5) | 3097 (20.9) | 3078 (19.8) | 3526 (20.4) |
| 90 d | 14 273 (23.2) | 3336 (24.1) | 3469 (23.5) | 3522 (22.6) | 3946 (22.9) |
| CD ≥3a, No. (%) | |||||
| 30 d | 28 513 (46.4) | 6856 (49.4) | 7013 (47.4) | 7085 (45.6) | 7559 (43.8) |
| 90 d | 30 545 (49.7) | 7282 (52.5) | 7415 (50.1) | 7531 (48.4) | 8317 (48.2) |
| ICU treatment, No. (%) | |||||
| 30 d | 3385 (5.5) | 535 (3.9) | 380 (2.6) | 994 (6.4) | 1476 (8.6) |
| 90 d | 3584 (5.8) | 555 (4.0) | 395 (2.7) | 1063 (6.8) | 1571 (9.1) |
| Mortality, No. (%) | |||||
| 30 d | 11 293 (18.4) | 3471 (25.0) | 3211 (21.7) | 2350 (15.1) | 2261 (13.1) |
| 90 d | 14 680 (23.9) | 4335 (31.3) | 4054 (27.4) | 3155 (20.3) | 3136 (18.2) |
Abbreviations: CD, Clavien-Dindo; CIP, cumulative incidence proportion; ICU, intensive care unit; LOS, length of stay.
Figure 1. Kaplan-Meier Estimates of 90-Day Mortality After Major Emergency Abdominal Surgery.
In the multivariate analysis, 90-day mortality was significantly and continuously reduced over the study period. When compared with data from 2002 to 2006, the 90-day mortality was significantly decreased from that of 2007 to 2011 (OR, 0.75; 95% CI, 0.70-0.79; P < .001), from 2012-2016 (OR, 0.48; 95% CI, 0.45-0.51; P <.001), and from 2017 to 2022 (OR, 0.45; 95% CI, 0.42-0.47; P <.001). Significant risk factors for mortality were increasing age and CCI, open surgery, indication for surgery being perforation, ischemia or bleeding, no bowel resection, and creation of a stoma. The results of the multivariate analysis are available in Table 3.
Table 3. Multivariate Logistic Regression Model Identifying Risk Factors for Mortality, Postoperative Complications (CD ≥3a), and Readmission 90 Days After Major Emergency Abdominal Surgery.
| Variable | Mortality | Postoperative complication (CD ≥3a) | Readmission | |||
|---|---|---|---|---|---|---|
| OR (95% CI) | P value | OR (95% CI) | P value | OR (95% CI) | P value | |
| Sex | ||||||
| Female | 0.97 (0.93-1.02) | .22 | 0.83 (0.80-0.86) | <.001 | 0.91 (0.88-0.95) | <.001 |
| Male | 1 [Reference] | 1 [Reference | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Age, y | ||||||
| <50 | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| 50-59 | 2.48 (2.21-2.80) | <.001 | 1.31 (1.23-1.40) | <.001 | 1.10 (1.02-1.19) | .01 |
| 60-69 | 3.63 (3.26-4.05) | <.001 | 1.52 (1.43-1.61) | <.001 | 1.13 (1.05-1.21) | <.001 |
| 70-79 | 5.75 (5.18-6.39) | <.001 | 1.76 (1.66-1.86) | <.001 | 1.10 (1.03-1.18) | .004 |
| ≥80 | 11.46 (10.34-12.74) | <.001 | 2.16 (2.04-2.29) | <.001 | 1.09 (1.02-1.17) | .01 |
| Year of surgery | ||||||
| 2002-2006 | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| 2007-2011 | 0.75 (0.70-0.79) | <.001 | 0.93 (0.88-0.98) | .004 | 1.15 (1.07-1.23) | <.001 |
| 2012-2016 | 0.48 (0.45-0.51) | <.001 | 0.97 (0.92-1.02) | .26 | 1.52 (1.43-1.63) | <.001 |
| 2017-2022 | 0.45 (0.42-0.47) | <.001 | 1.02 (0.97-1.07) | .43 | 3.47 (3.27-3.69) | <.001 |
| Charlson Comorbidity Index | ||||||
| 0-1 | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| 2-3 | 4.22 (4.02-4.43) | <.001 | 2.22 (2.12-3.33) | <.001 | 1.22 (1.16-1.28) | <.001 |
| ≥4 | 7.55 (6.85-8.33) | <.001 | 3.36 (3.03-3.74) | <.001 | 1.11 (1.00-1.24) | .05 |
| Indication for surgery | ||||||
| Perforation | 1.47 (1.32-1.64) | <.001 | 2.92 (2.62-3.26) | <.001 | 1.05 (0.94-1.17) | .40 |
| Ischemia | 4.70 (4.18-5.28) | <.001 | 6.80 (5.97-7.75) | <.001 | 0.77 (0.68-0.88) | <.001 |
| Bowel obstruction | 0.86 (0.78-0.96) | .008 | 1.33 (1.19-1.48) | <.001 | 0.97 (0.87-1.09) | .64 |
| Bleeding | 1.69 (1.41-2.03) | <.001 | 3.88 (3.15-4.81) | <.001 | 1.01 (0.82-1.23) | .93 |
| Type of surgery | ||||||
| Laparoscopic | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Open | 1.99 (1.83-2.16) | <.001 | 1.73 (1.64-1.82) | <.001 | 1.23 (1.15-1.30) | <.001 |
| Bowel resection | 0.79 (0.75-0.83) | <.001 | 0.70 (0.67-0.73) | <.001 | 0.97 (0.92-1.02) | .29 |
| Creation of stoma | 1.83 (1.73-1.93) | <.001 | 2.41 (2.30-2.53) | <.001 | 1.57 (1.48-1.66) | <.001 |
Abbreviations: CD, Clavien-Dindo; OR, odds ratio.
LOS and Readmissions
The median (IQR) LOS was reduced from 10 (5-17) days to 6 (4-13) days from 2002 to 2006 to the period 2017 to 2022. The number of patients with LOS greater than 7 days was reduced from 67% (9320 of 13 869) during the 2002 to 2006 period to 44% (7526 of 17 260) in the 2017 to 2022 period.
Contradictory, readmissions increased drastically and significantly throughout the study period. The cumulative incidence of readmissions within 30 days increased from 9% (1269 of 13 869) to 25% (4269 of 17 260) from 2002 to 2006 to the period 2017 to 2022, and within 90 days from 13% (1824 of 13 869) to 33% (5692 of 17 260), respectively. Adjusting for the competing risk of death, the cumulated incidence of readmission remained significantly higher among patients undergoing surgery in 2017 to 2022.
The results are available in Table 2 and elaborated in eTable 4 in Supplement 1. The cumulated incidences of readmission adjusted for the competing risk of death are depicted in Figure 2A.
Figure 2. Cumulative Incidences of 90-Day Readmission and 90-Day Clavien-Dindo Complications After Major Emergency Abdominal Surgery.
A, Readmission after 90 days. B, Clavien-Dindo ≥3 complications after 90 days.
In the multivariate analysis, the 90-day readmission rate significantly and continuously increased over the study period. When compared with data from 2002 to 2006, the 90-day readmission was significantly increased from 2007 to 2011 (OR, 1.15; 95% CI, 1.07-1.23; P <.001), from 2012 to 2016 (OR, 1.52; 95% CI, 1.43-1.63; P <.001), and from 2017 to 2022 (OR, 3.47; 95% CI, 3.27-3.69; P <.001). Significant risk factors for readmission were male sex, increasing age and CCI, open surgery, and indication for surgery being ischemia and creation of a stoma. The results of the multivariate analysis are available in Table 3.
Postoperative Complications
The overall incidence of CD ≥3a complications slightly decreased over the study period. The 30-day rate of CD ≥3a complications decreased from 49% in 2002 to 2006 to 44% in 2017 to 2022. The 90-day rate decreased from 53% to 48% over the same period. Adjusting for the competing risk of death, the differences in 30- and 90-day postoperative complications remained statistically higher among patients undergoing surgery in 2012 to 2016 and 2017 to 2022. Notably, an increase in CD ≥3a complications was observed within the first 10 postoperative days, followed by a flattening of the curve, demonstrating a considerable decrease in complications after the tenth postoperative day. The cumulated incidences of CD ≥3a complications adjusted for the competing risk of death are depicted in Figure 2B.
In the multivariate analysis, the risk of CD ≥3a complications significantly decreased from 2002 to 2006 to the period 2007 to 2011 (OR, 0.93; 95% CI, 0.88-0.98, P =.004). However, no significant difference was observed when comparing 2002 to 2006 with the periods 2012 to 2016 and 2017 to 2022 (OR, 0.97; 95% CI, 0.92-1.02; P = .26 and OR, 1.02; 95% CI, 0.97-1.07; P = .43).
Significant risk factors for complications of CD ≥3a complications were male sex, increasing age and CCI, open surgery, indication for surgery being perforation, bowel obstruction, ischemia or bleeding, no bowel resection, and creation of a stoma. The results of the multivariate analysis are available in Table 3.
The postoperative complications were further subcategorized according to CD classification. The rate of CD 3a complications increased significantly throughout the study period, from 11% in 2002 to 2006 to 17% from 2017 to 2022 after 30 days and from 14% to 22% after 90 days (P < .001). The 30- and 90-day rate of CD 3b complications remained constant throughout the study period. The difference in the 30-day rate of CD 3b complications was statistically significant from 22% in the 2002 to 2006 period to 20% in the 2017 to 2022 period (P = .003), whereas the difference in the 90-day rate was nonsignificant, from 24% in the 2002 to 2006 period to 23% in the 2017 to 2022 period (P = .07). The number of patients necessitating ICU treatment increased significantly from 4% (555 of 13 869) in 2002 to 2007 to 9% (1571 of 17 260) in 2017 to 2022.
The results are available in Table 2 and elaborated in eTable 4 in Supplement 1.
Discussion
Results of this nationwide cohort study suggest significant improvements in the outcomes of patients undergoing MEAS in Denmark over the past 2 decades, as evidenced by reduced mortality rates and shorter hospital LOS. However, the 3-doubling rate of readmission and the persistently high rates of postoperative complications highlight a shift in patient pathways and an ongoing challenge in the management of this patient population.
The reduction in mortality aligns with trends observed in previous research, where improvements in surgical techniques, perioperative care, and hospital infrastructure have collectively contributed to better outcomes.31,32 The increasing use of minimally invasive surgical procedures has likely played a considerable role in reducing mortality rates.33 This study reflects the trend toward minimally invasive surgery, which, according to previous studies, has been associated with reduced postoperative pain, shorter recovery times, and lower rates of postoperative infections than open procedures.
The reduction in mortality from 2008 to 2013 coincides with the implementation of the emergency surgery subspecialty, standardized care bundles, and enhanced recovery protocols for MEAS in Denmark. The preoperative care bundles streamline the process from diagnosis to surgery,9 and previous literature has associated the rapid diagnosis and preoperative optimization with improved outcomes.34,35,36 Enhanced recovery protocols streamline the process from surgery to discharge, which is associated with lower complication rates and shorter LOS.21 However, it was not possible to select patients managed with preoperative care bundles or enhanced recovery protocols in this study, and it is, therefore, not possible to draw a causal association.
The decline in mortality, along with a rise in CD ≥3a complications within the first 10 postoperative days and lower 30- and 90-day complication rates, indicate a shift toward an earlier and more aggressive complication approach in patients with major complications. These results could indicate an improved ability to prevent mortality following major complications, contributing to a notable reduction in failure to rescue throughout the study.37
The rate of CD 3b complications was initially hypothesized to decrease over the study period, mirroring the anticipated reduction in mortality. A possible explanation for the persistently high rate of CD 3b complications could be the increasing use of damage control approach and vacuum-assisted temporary abdominal closure in patients with secondary peritonitis, bowel ischemia, and considerable hemodynamic instability.38,39,40 These patients undergo planned relaparotomy, which is not considered a CD 3b complication from a clinical perspective. However, the register-based study methodology does not allow for a distinction between planned laparotomy and laparotomy on demand.
The drastically increasing number of readmissions presented in this study matches the results from a prospective Danish study.41 When compared with international data, readmission rates in Denmark appear higher although still within a comparable range.42,43,44 This higher rate can be explained by the complete follow-up, including all readmissions, some of which may be unrelated to the initial surgical procedure. The increasing trend in readmissions has not been described in previous studies. The reduced mortality cannot solely explain it, as the cumulative incidence was significantly higher when adjusting for the competing risk of death. Causes cannot be determined from the existing data. However, contributing factors could be an increasing awareness of this patient population and a gradual transition from in-person to telephonic public medical helplines outside of office hours in Denmark since 2014.45 Despite improvements in mortality and LOS, these results highlight concerning trends in postoperative complications and readmissions. This trade-off between shorter hospital stays and increased readmissions could be a consequence of budgetary optimizations and increased pressure on staffing and health-related economics. These results underscore the need for research focusing on the causes of readmission and initiatives to improve postdischarge follow-up care.
Limitations
The primary limitations of this study are linked with the register-based design.46 ICD-10 and NSCP codes from NPR could be wrongfully registered, impacting the population’s definition and outcome measures. The decision to only include patients with relevant NSCP codes linked with relevant ICD-10 codes most likely limits the population. However, if choosing to expand the definition, the risk of including patients not undergoing MEAS was deemed too high. The introduction of care bundles and increased research focus on outcomes in frail patients undergoing MEAS could have led to a shift in selecting patients considered candidates for surgery throughout the study period.22,47,48 Likewise, stable patients with contained perforations or obstruction without bowel ischemia could increasingly be treated nonsurgically. These shifts in patient selection could explain the change in the rate of patients undergoing surgery due to intestinal perforation vs bowel obstruction throughout the study period. In the present study, comparing the outcomes with those of a nonsurgical cohort was not possible. Still, this selection bias could contribute to a further decrease in mortality in this population.
Preoperative and intraoperative information was not available, eg, smoking, alcohol use, height, weight, severity of comorbidities, history of previous abdominal surgeries, duration of surgery, intra-abdominal contamination, and use of blood transfusions and antibiotics. These clinical covariates would be relevant for adequately investigating the risk of adverse postoperative outcomes.
Although external validity may vary due to various endemic factors and differences in health care systems and acute care protocols, the nationwide study design, large study population, and complete data from Danish health registries enhance its generalizability to similar international cohorts.
This study provides valuable insights into the MEAS population, but several areas warrant further investigation. Detailed analysis of the impact of different surgical strategies on outcomes is needed. This includes preoperative and intraoperative strategies for ensuring that the patients are sufficiently resuscitated and that the right competencies are in-house when performing the surgical interventions. Given the increasing rate of readmissions, research focusing on identifying reasons for readmissions and effective readmission prevention strategies is warranted. This could include trials of postdischarge interventions such as telemonitoring, enhanced home care, and early and late outpatient follow-up. This research could form the basis for using artificial intelligence to develop individualized postoperative courses. Finally, future studies should explore the long-term outcomes for patients undergoing MEAS, including quality of life, physical abilities, and the long-term burden of complications. Understanding these outcomes is crucial for assessing the surgical interventions’ true impact and optimizing the surgical outcomes.
Conclusions
Results of this cohort study suggest an important reduction in mortality and hospital LOS after MEAS. However, the persistently high rates of postoperative complications and drastically increasing readmission rates highlight the ongoing challenges in managing this patient population, also from a resource perspective. Further clinical research on tailored perioperative care, enhanced postoperative monitoring, and robust postdischarge support is warranted.
eTable 1. International Classification of Diseases System Version 10 (ICD-10) and NOMESCO Classification of Surgical Procedures (NCSP) Codes Used for Definition of the Study Population
eTable 2. Yearly Number of Major Emergency Abdominal Procedures
eTable 3. Baseline Characteristics
eTable 4. Postoperative Outcomes and Complications Within 30- and 90 Days After Primary Major Emergency Abdominal Surgery
eFigure. Thirty- and 90-Day Mortality After Major Emergency Abdominal Surgery From 2002-2022
Data Sharing Statement.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
eTable 1. International Classification of Diseases System Version 10 (ICD-10) and NOMESCO Classification of Surgical Procedures (NCSP) Codes Used for Definition of the Study Population
eTable 2. Yearly Number of Major Emergency Abdominal Procedures
eTable 3. Baseline Characteristics
eTable 4. Postoperative Outcomes and Complications Within 30- and 90 Days After Primary Major Emergency Abdominal Surgery
eFigure. Thirty- and 90-Day Mortality After Major Emergency Abdominal Surgery From 2002-2022
Data Sharing Statement.
