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. 2021 Apr 9;118(14):244–249. doi: 10.3238/arztebl.m2021.0118

Acute Appendicitis: Trends in Surgical Treatment

A Population-Based Study of Over 800 000 Patients

Christian Stöß* 1,2, Ulrich Nitsche* 1,2, Philipp-Alexander Neumann 2, Victoria Kehl 3, Dirk Wilhelm 2, Reinhard Busse 4, Helmut Friess 2,*, Ulrike Nimptsch 4
PMCID: PMC8283679  PMID: 34114553

Abstract

Background

Appendectomy is the gold standard for treatment of acute appendicitis. However, recent studies favor primary antibiotic therapy. The aim of this observational study was to explore changes in the numbers of operations for acute appendicitis in the period 2010–2017, paying special attention to disease severity.

Methods

Data from diagnosis-related group statistics were used to analyze the trends, mortality, and complication rates in the surgical treatment of appendicitis in Germany between 2010 and 2017. All cases of appendectomy after a diagnosis of appendicitis were included.

Results

Altogether, 865 688 inpatient cases were analyzed. The number of appendectomies went down by 9,8%, from 113 614 in 2010 to 102 464 in 2017, while the incidence fell from 139/100 000 in 2010 to 123/100 000 in 2017 (standardized by age group). This decrease is due to the lower number of operations for uncomplicated appendicitis (79 906 in 2017 versus 93 135 in 2010). Hospital mortality decreased both in patients who underwent surgical treatment of complicated appendicitis (0.62% in 2010 versus 0.42% in 2017) and in those with a complicated clinical course (5.4% in 2010 versus 3.4% in 2017).

Conclusion

Decisions on the treatment of acute appendicitis in German hospitals follow the current trend towards non-surgical management in selected patients. At the same time, the care of acute appendicitis has improved with regard to overall hospital morbidity and hospital mortality.

Appendicitis is a common global disease with a lifetime risk of 7–8% (1). The pooled incidence of appendicitis in Western Europe is estimated at 151 per 100 000 person-years (2). Appendectomy has been established as the treatment of choice for acute appendicitis (3). In recent years, the surgical treatment of acute uncomplicated appendicitis – defined as the absence of perforation or abscess – has been challenged in several randomized controlled trials. Some have proclaimed a paradigm shift and proposed antibiotics alone as first-line treatment for acute appendicitis (4– 9). However, estimating the course of the disease remains problematic even with the use of diagnostic imaging (e.g., low-dose computed tomography) (9). In 14 to 40% of all cases, primary antibiotic treatment is followed by recurrence and rescue surgery. The guideline recommendations regarding conservative and surgical treatment options therefore show considerable heterogeneity (10– 14).

The aim of this study was to depict trends in case numbers for surgical treatment of acute appendicitis in Germany by examining all inpatient cases from 2010 to 2017, based on full national data sets. Specifically, outcomes of care were assessed by studying indicators of complicated clinical courses and in-hospital mortality.

Methods

This retrospective observational study was based on microdata analysis of diagnosis-related group statistics for the years 2010 to 2017 via the Research Data Center of the Federal Statistical Office by means of controlled data processing (15). Details of the statistical methods can be found in the eMethods. The inclusion and exclusion criteria for diagnosis codes (International Statistical Classification of Diseases, 10th revision [ICD-10]) and procedure codes (German classification for operations and procedures [OPS]) are given in eTable 1.

eTable 1. Definition of patient population and stratification variables.

Inclusion criteria Exclusion criteria
Patient population
All inpatient cases with appendectomy as sole intervention for acute appendicitis PD ICD-10 K35, K36, K37 and OPS 5-470, 5-455.3 OPS 5-471, 5-479
Severity
Uncomplicated appendicitis PD ICD-10 K35.30, K35.8, K36, K37
Complicated appendicitis PD ICD-10 K35.2, K35.31, K35.32
Surgical approach
Open OPS 5-470.0, 5-455.31 OPS 5-470.2, 5-455.37
Laparoscopic OPS 5-470.1, 5-455.35 OPS 5-470.0, 5-470.2, 5-455.31, 5-455.37
Conversion OPS 5-470.2, 5-455.37
Other or undefined OPS 5-470.x, 5-470.y OPS 5-470.0, 5-470.1, 5-470.2, 5-455.31, 5-455.35, 5-455.37
Type of surgery
Appendectomy OPS 5-470 OPS 5-455.3
Cecal resection OPS 5-455.3
Indicators of complicated course
Septicemia SD ICD-10 A40, A41, R57.2, R65
Blood transfusions, ≥ 6 units OPS 8-800.1, 8-800.c1-cr
Postoperative ileus SD ICD-10 K91.3
Mechanical ventilation > 24 h Mechanical ventilation for > 24 h (separate data field)
Complex intensive care OPS 8-980, 8-98d, 8-98f (from 2013)
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ICD, International Statistical Classification of Diseases; OPS, German classification for operations and procedures (Operationen- und Prozedurenschlüssel); PD, principal diagnosis; SD, secondary diagnosis

Complicated appendicitis was identified by the ICD-10 codes K35.2 (with generalized peritonitis), K35.31 (localized peritonitis with perforation or rupture), and K35.32 (with peritoneal abscess). The clinical outcome was assessed in terms of in-hospital mortality and indicators of a complicated clinical course. Based on previous research, these indicators were defined by means of the ICD-10 codes for the secondary diagnoses of septicemia or postoperative ileus and the OPS codes for blood transfusion (≥ six units), complex intensive care treatment, or mechanical ventilation for more than 24 hours (etable 1) (16, 17).

Results

Characteristics of cases treated

A total of 865 688 inpatient appendectomies for acute appendicitis were performed as independent procedures in Germany during the period 2010 to 2017 and were thus included in this study. The overall number of operations per year declined linearly from 113 614 cases in 2010 to 102 464 cases in 2017, a relative overall reduction of 9.8% (Table 1, eTable 2).

Table 1. Characteristics of inpatient cases with appendectomy as sole intervention for acute appendicitis.

2010 2017
n % n %
Total number of inpatient cases 113 614 100.0 102 464 100.0
Incidence per 100 000 persons 139 124
Incidence per 100 000 persons
(standardized by age group, in relation to 2010)		 139 123
Age (years) < 15 22 273 19.6 14 944 14.6
15–35 53 165 46.8 47 331 46.2
> 35 38 176 33.6 40 189 39.2
Sex Female 59 734 52.6 51 173 49.9
Length of hospital stay (days) Mean (median) 5.1 (4) 4.4 (4)
Severity Uncomplicated appendicitis 93 135 82.0 79 906 78.0
Complicated appendicitis 20 479 18.0 22 558 22.0
Surgical procedure Laparoscopic surgery 86 500 76.1 95 441 93.1
Open surgery 23 365 20.6 4534 4.4
Conversion 3728 3.3 2450 2.4
Other or undefined 21 0.0 39 0.0
Type of surgery Appendectomy 112 815 99.3 101 037 98.6
Cecal resection 799 0.7 1427 1.4
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eTable 2. Characteristics of inpatient cases with appendectomy as sole intervention for appendicitis.

2010 2011 2012 2013 2014 2015 2016 2017
n % n % n % n % n % n % n % n %
Total number of inpatient cases 113 614 100.0 113 975 100.0 111 957 100.0 108 437 100.0 107 322 100.0 104 922 100.0 102 997 100.0 102 464 100.0
Incidence per 100 000 persons 139 142 139 134 132 128 125 124
Incidence per 100 000 persons
(standardized by age group, in relation to 2010)		 139 142 139 134 132 127 124 123
Age (years) < 15 22 273 19.6 21 451 18.8 19 991 17.9 18 256 16.8 16 893 15.7 15 891 15.1 15 139 14.7 14 944 14.6
15–35 53 165 46.8 53 537 47.0 53 171 47.5 52 412 48.3 51 967 48.4 50 151 47.8 48 692 47.3 47 331 46.2
> 35 38 176 33.6 38 987 34.2 38 795 34.7 37 769 34.8 38 462 35.8 38 880 37.1 39 166 38.0 40 189 39.2
Gender Female 59 734 52.6 60 236 52.9 58 890 52.6 57 071 52.6 56 563 52.7 53 715 51.2 51 944 50.4 51 173 49.9
Length of hospital stay (days) Mean (median) 5.1 (4) 4.9 (4) 4.8 (4) 4.7 (4) 4.6 (4) 4.6 (4) 4.6 (4) 4.4 (4)
Severity Uncomplicated appendicitis 93 135 82.0 92 911 81.5 90 824 81.1 87 574 80.8 86 559 80.7 83 362 79.5 81 140 78.8 79 906 78.0
Complicated appendicitis 20 479 18.0 21 064 18.5 21 133 18.9 20 863 19.2 20 763 19.3 21 560 20.5 21 857 21.2 22 558 22.0
Surgical approach Laparoscopic 86 500 76.1 91 633 80.4 93 663 83.7 93 697 86.4 95 378 88.9 95 053 90.6 94 687 91.9 95 441 93.1
Open 23 365 20.6 18 582 16.3 14 777 13.2 11 578 10.7 9009 8.4 6992 6.7 5578 5.4 4534 4.4
Conversion 3728 3.3 3688 3.2 3441 3.1 3118 2.9 2908 2.7 2848 2.7 2704 2.6 2450 2.4
Other or undefined 21 0.0 72 0.1 76 0.1 44 0.0 27 0.0 29 0.0 28 0.0 39 0.0
Type of surgery Appendectomy 112 815 99.3 113 121 99.3 111 046 99.2 107 427 99.1 106 216 99.0 103 612 98.8 101 670 98.7 101 037 98.6
Cecal resection 799 0.7 854 0.7 911 0.8 1010 0.9 1106 1.0 1310 1.2 1327 1.3 1427 1.4
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Taking the population of Germany into consideration (18), the incidence of appendectomy in the year 2010 was 139 per 100 000 person-years. By 2017, the incidence had fallen to 124 per 100 000 person-years. Standardized by age groups to 2010, the incidence declined from 139 per 100 000 in 2010 to 123 per 100 000 in 2017 (etable 2). This corresponds to a relative reduction of approximately 11.5% within 8 years. The proportion represented by the youngest age group (< 15 years) decreased during the study from an initial 20% (n = 22 273) to 15% (n = 14 944), while the group “15–35” remained stable at 46% (n = 47 331) and the group “35 or older” increased from 34% (n = 38 176) to 39% (n = 40 189).

The proportion of female patients was higher in 2010 (53%; n = 59 734) than in 2017 (50%; n = 51 173). The mean length of hospital stay went down from 5.1 days to 4.4 days during the 8-year observation period. The proportion of operations performed for uncomplicated appendicitis decreased from 82% (n = 93 135) in 2010 to 78% (n = 79 906) in 2017. Conversely, the proportion of operations for complicated appendicitis increased from 18% (n = 20 479) to 22% (n = 22 558) (Figure 1). This trend can also be observed in the analysis of all individual federal states of Germany, with the sole exception of Saarland, where the opposite trend was found (etable 3).

Figure 1.

Figure 1

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Number of appendectomies in the period 2010–2017

The overall number of appendectomies fell by 9.8% from 113 614 cases in 2010 to 102 464 cases in 2017. The proportion of all appendectomies accounted for by complicated appendicitis increased to 22%, while that for uncomplicated appendicitis decreased to 78%.

eTable 3. Inpatient cases of uncomplicated and complicated appendicitis per federal state (patient’s place of residence).

2010 2011 2012 2013 2014 2015 2016 2017
n % n % n % n % n % n % n % n %
Germany Uncomplicated appendicitis 93 135 82.0 92 911 81.5 90 824 81.1 87 574 80.8 86 559 80.7 83 362 79.5 81 140 78.8 79 906 78.0
Complicated appendicitis 20 479 18.0 21 064 18.5 21 133 18.9 20 863 19.2 20 763 19.3 21 560 20.5 21 857 21.2 22 558 22.0
Schleswig–Holstein Uncomplicated appendicitis 2702 80.4 2820 80.1 2736 79.1 2731 80.4 2736 79.5 2605 78.3 2490 76.9 2372 77.4
Complicated appendicitis 657 19.6 702 19.9 721 20.9 664 19.6 706 20.5 722 21.7 750 23.1 691 22.6
Hamburg Uncomplicated appendicitis 1831 83.6 1822 81.7 1831 82.4 1795 81.7 1837 82.5 1667 82.5 1658 79.7 1633 79.7
Complicated appendicitis 360 16.4 409 18.3 392 17.6 401 18.3 391 17.5 354 17.5 421 20.3 415 20.3
Lower Saxony Uncomplicated appendicitis 10 008 82.0 9756 81.8 9302 80.5 9022 79.8 9025 81.0 8522 79.1 8152 78.9 8150 78.8
Complicated appendicitis 2204 18.0 2169 18.2 2257 19.5 2282 20.2 2121 19.0 2251 20.9 2179 21.1 2199 21.2
Bremen Uncomplicated appendicitis 527 77.6 542 79.0 595 78.7 573 77.1 541 77.4 550 77.0 492 74.3 525 76.1
Complicated appendicitis 152 22.4 144 21.0 161 21.3 170 22.9 158 22.6 164 23.0 170 25.7 165 23.9
North Rhine–Westphalia Uncomplicated appendicitis 21 957 82.6 21 532 81.9 21 329 81.7 20 169 80.9 19 840 81.1 19 563 80.4 19 019 79.8 18 426 78.7
Complicated appendicitis 4610 17.4 4766 18.1 4771 18.3 4751 19.1 4632 18.9 4762 19.6 4806 20.2 4989 21.3
Hesse Uncomplicated appendicitis 6383 80.8 6449 81.1 6355 80.3 6097 79.7 6127 80.4 5969 78.2 5945 78.0 5952 78.3
Complicated appendicitis 1521 19.2 1507 18.9 1561 19.7 1552 20.3 1498 19.6 1667 21.8 1679 22.0 1653 21.7
Rhineland–Palatinate Uncomplicated appendicitis 4670 82.1 4530 81.1 4323 80.8 4281 81.4 3988 80.1 3917 78.3 3756 78.7 3812 77.7
Complicated appendicitis 1019 17.9 1057 18.9 1026 19.2 978 18.6 992 19.9 1087 21.7 1019 21.3 1094 22.3
Baden–Württemberg Uncomplicated appendicitis 11 035 80.7 11 154 80.3 10 890 79.5 10 780 79.5 10 528 77.9 10 154 78.2 9975 77.5 10 223 76.9
Complicated appendicitis 2639 19.3 2737 19.7 2804 20.5 2786 20.5 2989 22.1 2833 21.8 2895 22.5 3072 23.1
Bavaria Uncomplicated appendicitis 15 508 83.8 15 944 83.1 15 633 82.9 14 903 83.0 14 746 82.8 13 990 81.1 13 176 79.7 13 086 78.8
Complicated appendicitis 3001 16.2 3246 16.9 3234 17.1 3062 17.0 3057 17.2 3267 18.9 3362 20.3 3527 21.2
Saarland Uncomplicated appendicitis 834 78.0 939 78.8 978 80.9 928 78.1 860 78.0 840 78.7 887 80.0 847 78.3
Complicated appendicitis 235 22.0 252 21.2 231 19.1 260 21.9 242 22.0 227 21.3 222 20.0 235 21.7
Berlin Uncomplicated appendicitis 3458 79.4 3435 80.8 3341 80.6 3318 80.3 3415 80.2 3110 78.0 3128 76.7 3160 76.5
Complicated appendicitis 897 20.6 818 19.2 805 19.4 814 19.7 842 19.8 876 22.0 950 23.3 970 23.5
Brandenburg Uncomplicated appendicitis 2651 80.9 2582 80.1 2600 80.9 2424 80.6 2386 79.2 2233 77.3 2269 77.6 2246 76.3
Complicated appendicitis 627 19.1 641 19.9 613 19.1 583 19.4 625 20.8 656 22.7 656 22.4 698 23.7
Mecklenburg–Western Pomerania Uncomplicated appendicitis 1479 79.9 1483 78.7 1508 79.7 1429 79.2 1472 79.8 1418 78.5 1397 78.1 1258 74.7
Complicated appendicitis 372 20.1 401 21.3 384 20.3 376 20.8 372 20.2 389 21.5 391 21.9 427 25.3
Saxony Uncomplicated appendicitis 4074 82.1 3960 81.6 3926 80.8 3755 79.8 3681 80.1 3617 78.2 3467 78.0 3338 76.3
Complicated appendicitis 891 17.9 892 18.4 930 19.2 950 20.2 917 19.9 1008 21.8 977 22.0 1037 23.7
Saxony–Anhalt Uncomplicated appendicitis 2376 81.0 2374 79.8 2333 80.5 2268 80.5 2350 81.5 2315 79.4 2311 78.8 2131 77.5
Complicated appendicitis 559 19.0 601 20.2 564 19.5 549 19.5 532 18.5 602 20.6 623 21.2 617 22.5
Thuringia Uncomplicated appendicitis 2672 84.8 2688 84.9 2581 84.0 2551 83.0 2448 82.8 2313 81.9 2326 82.4 2155 79.6
Complicated appendicitis 479 15.2 479 15.1 493 16.0 523 17.0 509 17.2 510 18.1 498 17.6 552 20.4
Other country or unknown Uncomplicated appendicitis 970 79.1 901 78.8 563 75.2 550 77.2 579 76.3 579 75.8 692 72.8 592 73.2
Complicated appendicitis 256 20.9 243 21.2 186 24.8 162 22.8 180 23.7 185 24.2 259 27.2 217 26.8
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Morbidity and mortality

The mean rates for secondary diagnoses or procedures such as septicemia (0.56%), blood transfusion (0.07%), postoperative ileus (0.46%), mechanical ventilation > 24 hours (0.33%) and complex intensive care treatment (1.58%) did not change significantly. The proportion of cases with at least one of the above-mentioned surrogates for a complicated course stayed constant at 2.2–2.4% (2010: n = 2540; 2017: n = 2502). The overall in-hospital mortality rate was 0.12% (n = 118) in 2017 compared with 0.16% (n = 184) in 2010. If at least one of the indicators for a complicated course was present, the mean in-hospital mortality rate increased steeply to 4.2%. Here too, however, in-hospital mortality declined, from 5.4% (n = 136) in 2010 to 3.4% (n = 86) in 2017 (Table 2, eTable 4).

Table 2. Morbidity and mortality of inpatient cases with appendectomy as sole intervention for appendicitis.

2010 2017
n % n %
Total number of patients 113 614 100.0 102 464 100.0
Indicators of complicated course Septicemia 578 0.5 727 0.7
Blood transfusions
(≥ 6 units)		 108 0.1 50 0.05
Postoperative ileus 494 0.4 537 0.5
Mechanical ventilation > 24 h 434 0.4 309 0.3
Complex intensive care 1796 1.6 1609 1.6
At least one indicator of complicated course 2540 2.2 2502 2.4
In-hospital mortality (all appendectomy cases) 184 0.16 118 0.12
In-hospital mortality (among patients with at least one indicator of complicated course) 136 5.4 86 3.4
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eTable 4. Morbidity and mortality of inpatient cases with appendectomy as sole intervention for appendicitis.

2010 2011 2012 2013 2014 2015 2016 2017
n % n % n % n % n % n % n % n %
Total number of patients 113 614 100.0 113 975 100.0 111 957 100.0 108 437 100.0 107 322 100.0 104 922 100.0 102 997 100.0 102 464 100.0
Indicators of complicated course Septicemia 578 0.5 533 0.5 545 0.5 535 0.5 578 0.5 650 0.6 677 0.7 727 0.7
Blood transfusions
(≥ 6 units)		 108 0.1 104 0.1 90 0.1 77 0.1 75 0.1 52 0.05 59 0.1 50 0.05
Postoperative ileus 494 0.4 468 0.4 473 0.4 454 0.4 509 0.5 526 0.5 521 0.5 537 0.5
Mechanical ventilation > 24 h 434 0.4 399 0.4 384 0.3 346 0.3 320 0.3 363 0.3 329 0.3 309 0.3
Complex intensive care 1796 1.6 1806 1.6 1693 1.5 1678 1.5 1744 1.6 1690 1.6 1697 1.6 1609 1.6
At least one indicator of complicated course 2540 2.2 2496 2.2 2432 2.2 2346 2.2 2512 2.3 2501 2.4 2521 2.4 2502 2.4
In-hospital mortality (all appendectomy cases) 184 0.16 174 0.15 138 0.12 139 0.13 134 0.12 112 0.11 114 0.11 118 0.12
In-hospital mortality (among patients with at least one indicator of complicated course) 136 5.4 131 5.3 105 4.3 106 4.5 107 4.3 86 3.4 81 3.2 86 3.4
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Uncomplicated versus complicated appendicitis

The ratio of appendectomies for uncomplicated versus complicated appendicitis differed among the age groups (efigure). In patients aged < 15 years, the number of appendectomies for uncomplicated appendicitis declined, while the absolute numbers of appendectomies for complicated appendicitis stayed almost constant. As a consequence, the proportion of appendectomies for complicated appendicitis rose from 14% (n = 3083) in 2010 to 19% (n = 2879) in 2017. In the intermediate age group (15–35 years) the proportion of appendectomies for complicated appendicitis increased from 9% (n = 4604) in 2010 to 11% (n = 5104) in 2017, and for patients older than 35 years the proportion was 34% (n = 12 792) in 2010 and 36% (n = 14 575) in 2017.

eFigure.

eFigure

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The development of absolute case numbers for appendectomy, stratified by age group.

Of note, in-hospital mortality differed between uncomplicated appendicitis and complicated appendicitis (etable 5). The in-hospital mortality rate for uncomplicated appendicitis was 0.06% (57 deaths) in 2010 and fell by 50% to 0.03% in 2017 (23 deaths) (Figure 2a). The in-hospital mortality rate for an acute complicated appendicitis was more than 10 times higher: 0.62% (127 deaths) in 2010, 0.42% (95 deaths) in 2017. At least one of the indicators of a complicated clinical course was present in 9.3% (n = 1897) of all patients with complicated appendicitis in 2010 and in 8.9% (n = 2001) in 2017—compared with 0.7% and 0.6%, respectively, for uncomplicated appendicitis (Figure 2b).

eTable 5. Appendectomy case numbers, mortality, and morbidity, stratified by severity of appendicitis (uncomplicated or complicated).

2010 2011 2012 2013 2014 2015 2016 2017
n % n % n % n % n % n % n % n %
Total number of patients 113 614 100.0 113 975 100.0 111 957 100.0 108 437 100.0 107 322 100.0 104 922 100.0 102 997 100.0 102 464 100.0
Hospital size ≤ 20 000
cases per year		 Uncomplicated appendicitis 62 791 83.0 60 583 82.6 56 367 82.5 52 161 81.9 49 421 81.7 45 547 80.6 42 771 80.1 41 943 79.6
Complicated appendicitis 12 839 17.0 12 735 17.4 11 988 17.5 11 551 18.1 11 095 18.3 10 988 19.4 10 655 19.9 10 744 20.4
> 20 000
cases per year		 Uncomplicated appendicitis 30 344 79.9 32 328 79.5 34 457 79.0 35 413 79.2 37 138 79.3 37 815 78.2 38 369 77.4 37 963 76.3
Complicated appendicitis 7640 20.1 8329 20.5 9145 21.0 9312 20.8 9668 20.7 10 572 21.8 11 202 22.6 11 814 23.7
Age (years) < 15 Uncomplicated appendicitis 19 190 86.2 18 379 85.7 17 067 85.4 15 418 84.5 14 184 84.0 13 188 83.0 12 328 81.4 12 065 80.7
Complicated appendicitis 3083 13.8 3072 14.3 2924 14.6 2838 15.5 2709 16.0 2703 17.0 2811 18.6 2879 19.3
15–35 Uncomplicated appendicitis 48 561 91.3 48 791 91.1 48 325 90.9 47 634 90.9 47 283 91.0 45 205 90.1 43 809 90.0 42 227 89.2
Complicated appendicitis 4604 8.7 4746 8.9 4846 9.1 4778 9.1 4684 9.0 4946 9.9 4883 10.0 5104 10.8
> 35 Uncomplicated appendicitis 25 384 66.0 25 741 66.0 25 432 65.6 24 522 64.9 25 092 65.2 24 969 64.2 25 003 63.8 25 614 63.7
Complicated appendicitis 12 792 34.0 13 246 34.0 13 363 34.4 13 247 35.1 13 370 34.8 13 911 35.8 14 163 36.2 14 575 36.3
Mortality*1 In-hospital mortality Uncomplicated appendicitis 57 0.06 38 0.04 47 0.05 28 0.03 29 0.03 21 0.03 27 0.03 23 0.03
Complicated appendicitis 127 0.62 136 0.65 91 0.43 111 0.53 105 0.51 91 0.42 87 0.40 95 0.42
Complicated course*2 At least one indicator of complicated course Uncomplicated appendicitis 643 0.7 569 0.6 515 0.6 492 0.6 524 0.6 478 0.6 510 0.6 501 0.6
Complicated appendicitis 1897 9.3 1927 9.2 1917 9.1 1854 8.9 1988 9.6 2023 9.4 2011 9.2 2001 8.9
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*1 The percentages given indicate the proportion of the total quantity

*2 The percentages given indicate the proportion of the subset of uncomplicated (complicated) appendicitis per year

Figure 2.

Figure 2

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Development of in-hospital mortality and proportion of cases with complicated course, stratified by severity of appendicitis (complicated versus uncomplicated)

Mortality is higher for appendectomy cases with complicated appendicitis than for appendectomy cases with uncomplicated appendicitis and shows a declining trend over time (a).

The proportion of cases with a complicated course is higher for appendectomy cases with complicated appendicitis than for appendectomy cases with uncomplicated appendicitis. No temporal trend is evident (b).

Discussion

This study demonstrates a decrease in the number of appendectomies for acute appendicitis between 2010 and 2017 in Germany (relative reduction: 9.8%; demographically adjusted relative reduction: 11.5%). Interestingly, despite the reduction in the absolute number of appendectomies, the proportion of patients with complicated appendicitis has increased. This effect was most pronounced in patients younger than 15 years (etable 5). The decrease in cases reflects either a declining incidence of acute appendicitis or a decrease in the number of patients treated surgically. The latter would be consistent with the current trend towards primary antibiotic treatment in selected patients (19, 20). De Wijkerslooth et al. reported a fall in the incidence of appendectomy from 90 per 100 000 inhabitants in 2006 to 78 per 100 000 in 2015 (21). It remains unclear why the incidence in their study was significantly lower than in our and other studies (see below). Moreover, the authors were unable to determine whether the cause was a reduction in the incidence of acute appendicitis or a decrease in the number of patients treated surgically. Furthermore, improved diagnostic modalities (sonography, computed tomography, etc.) are contributing to the reduced rate of appendectomy. However, the reduction cannot be fully explained by a lower rate of negative appendectomies (22– 24).

The data on the development of the incidence of appendicitis are very heterogeneous. Studies in the USA and England describe decreasing rates (25, 26), while more recent publications report stable or rising case numbers (27– 30). A systematic review on the global incidence of appendicitis published in 2017 estimated the pooled incidence of appendicitis or appendectomy in western Europe at 151/100 000 person-years; since 1990 the incidence of appendectomy has decreased in western countries, while the incidence of appendicitis is stated as stable (2). Assuming that the incidence remained stable during the period we investigated, one can conclude that the observed decrease of appendectomies in Germany may be influenced by the growing number of studies which, on the basis of their results, recommend conservative treatment of 60–70% of all appendicitis patients (3, 19, 20, 31, 32). A glance at the appendectomy numbers for uncomplicated and complicated appendicitis seems to confirm this conclusion: The proportion of patients that underwent appendectomy for uncomplicated appendicitis fell from 82% (n = 93 135) in 2010 to 78% (n = 79 906) in 2017.

Since both the absolute and relative number of operations for complicated appendicitis increased, it might be supposed that an increasing number of patients treated with antibiotics were developing complicated appendicitis and required surgery. Although this cannot be supported by unambiguous data in this study, the results of a recently published randomized controlled trial suggest exactly this clinical scenario (20). This study of 1552 adult patients showed non-inferiority of antibiotic treatment; nevertheless, three out of every ten participants in the antibiotic arm of the trial had to undergo rescue appendectomy. In addition, the complication rate was correspondingly higher. In our study, the increase in the number of cecal resections from 799 (0.7%) in 2010 to 1427 (1.4%) in 2017 may be due to a delay in surgical intervention, as cecal resection is only performed when severe inflammation does not allow simple appendectomy.

Appendectomy is in principle a low-risk surgical procedure. The in-hospital mortality rate in Germany decreased from 0.16% (n = 184) in 2010 to 0.12% (n = 118) in 2017, which is comparable to mortality rates reported from other countries (0.09% to 0.25%) (33). Here, we also present data on the mortality rate stratified by disease severity. For uncomplicated appendicitis, the rate of death was 0.03% (95% confidence interval [0.02; 0.04]; n = 23) in 2017, compared to a significantly higher rate of 0.06% in 2010 ([0.05; 0.08]; n = 57). For complicated appendicitis, the mortality rate was more than 10 times higher in 2017, at 0.42% (n = 95), but also showed a downward trend (2010: 0.62%; n = 127). For those cases in which acute appendicitis—whether uncomplicated or complicated—was accompanied by at least one surrogate parameter of a complicated clinical course (i.e., septicemia, transfusion of more than six units of erythrocytes or whole blood, postoperative ileus, mechanical ventilation > 24 h, need for intensive care), the in-hospital mortality in 2017 was 3.4% (n = 86), compared with 5.4% (n = 136) in 2010. As expected, however, complicated appendicitis was more likely than uncomplicated appendicitis to involve a complicated clinical course (2017: 8.9% vs. 0.6%; 2010: 9.3% vs. 0.7%).

The present study has several limitations. Studies based on DRG statistics are subject to potential information bias introduced by inconstant coding behavior. Moreover, the distinction between non-perforated and perforated appendicitis is based on ICD-10 diagnoses. These are assigned on the basis of the surgeon’s intraoperative findings, so the distinction is open to interobserver variation (34). Cases with the clinical appearance of appendicitis and conservative treatment were excluded from the study because the respective number might have been distorted by incorrect diagnoses and multiple hospitalizations. Moreover, owing to the way in which DRG data are documented no temporal association could be established between possible subsequent procedures and diagnoses, which limits our assumptions with regard to a complicated disease course.

Given these limitations, the advantage of this study lies in the robustness of its data. Whereas study populations often represent only a statistical sample, our study included all inpatient cases in Germany who underwent surgery for acute appendicitis, corresponding to over 850 000 cases.

We therefore present not only developments in the surgical treatment of appendicitis, but also new data on in-hospital mortality of appendicitis, stratified by disease severity and clinical course. The numbers of appendectomies for appendicitis in general, and uncomplicated appendicitis in particular, fell during the study period, while the population (all residents of Germany) grew (18).

The findings of this study suggest that German hospitals are acting, albeit slowly, on the evidence of recently published studies favoring a non-operative approach in selected patients. Thus, an overall reduction of 9.8% was observed within 8 years. Advances in diagnosis may have contributed to this effect. Interestingly, the proportion of patients with complicated appendicitis treated with appendectomy increased during the period 2010 to 2017, while the use of appendectomy in those with uncomplicated appendicitis decreased. The outcome of treatment in terms of in-hospital morbidity and mortality improved during the same time span.

Supplementary Material

eMethods

Study design and setting

The study presented here is a population-based retrospective study based on the diagnosis-related groups hospital discharge data of the national reimbursement system (G-DRG). The evaluation of secondary data via the German DRG system for this investigation does not require ethics committee approval (e1).

Data

Since 2004, reimbursement for inpatient services in Germany has been uniform across all hospitals calculated through a DRG reimbursement system (G-DRG). The information available for each of these inpatient cases includes age, sex, diagnoses (coded according to the International Statistical Classification of Diseases and Related Health Problems, 10th revision, German modification, ICD-10-GM), procedures (coded according to the German classification for operations and procedures, OPS), length of hospital stay, and mode of discharge. The individual inpatient data of the DRG statistics for the years 2010 to 2017 were accessed remotely via the Research Data Center of the Federal Statistical Office by means of controlled remote data processing (15).

Inclusion criteria

The units of analysis were inpatient cases who underwent appendectomy as sole intervention for appendicitis. These cases were identified by a principal diagnosis of appendicitis in combination with the OPS code for appendectomy or cecal resection. The inclusion and exclusion criteria for the diagnosis and procedure codes are given in etable 1. Due to the nature of the data, no histological diagnoses were included in this analysis.

Stratification and outcome variables

Complicated appendicitis was identified by a principal diagnosis code of acute appendicitis with generalized (K35.2) or localized peritonitis with perforation or rupture (K35.31) or acute appendicitis with peritoneal abscess (K35.32). In accordance with previously published age distributions in patients with acute appendicitis, the study population was divided into three groups: < 15 years, 15–35 years, and > 35 years (e2). The clinical outcome was assessed in terms of in-hospital mortality and indicators of a complicated clinical course. Based on previous research, these indicators were defined by the ICD-10 codes for the secondary diagnoses septicemia and postoperative ileus, the procedure codes for blood transfusions (≥ 6 units), complex intensive care, or mechanical ventilation > 24 hours (etable 1) (16, 17). These indicators were designed to identify serious complications or procedures required for serious complications while being widely unaffected by variation in coding behavior (e3).

Statistical methods

This study follows the REporting of studies Conducted using Observational Routinely collected health Data (RECORD) statement checklist (e4). All calculations were performed using SAS Version 9.3 (SAS Institute Inc., Cary, NC, USA). Data were analyzed descriptively for every year of observation and are expressed as absolute and relative frequencies. Development of appendectomy case numbers over time was analyzed separately for uncomplicated and complicated appendicitis and stratified by age group and hospital size. Additionally, in-hospital mortality and indicators of clinical course were stratified according to uncomplicated or complicated appendicitis.

Footnotes

Conflict of interest statement

The authors declare that no conflict of interest exists.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

eMethods

Study design and setting

The study presented here is a population-based retrospective study based on the diagnosis-related groups hospital discharge data of the national reimbursement system (G-DRG). The evaluation of secondary data via the German DRG system for this investigation does not require ethics committee approval (e1).

Data

Since 2004, reimbursement for inpatient services in Germany has been uniform across all hospitals calculated through a DRG reimbursement system (G-DRG). The information available for each of these inpatient cases includes age, sex, diagnoses (coded according to the International Statistical Classification of Diseases and Related Health Problems, 10th revision, German modification, ICD-10-GM), procedures (coded according to the German classification for operations and procedures, OPS), length of hospital stay, and mode of discharge. The individual inpatient data of the DRG statistics for the years 2010 to 2017 were accessed remotely via the Research Data Center of the Federal Statistical Office by means of controlled remote data processing (15).

Inclusion criteria

The units of analysis were inpatient cases who underwent appendectomy as sole intervention for appendicitis. These cases were identified by a principal diagnosis of appendicitis in combination with the OPS code for appendectomy or cecal resection. The inclusion and exclusion criteria for the diagnosis and procedure codes are given in etable 1. Due to the nature of the data, no histological diagnoses were included in this analysis.

Stratification and outcome variables

Complicated appendicitis was identified by a principal diagnosis code of acute appendicitis with generalized (K35.2) or localized peritonitis with perforation or rupture (K35.31) or acute appendicitis with peritoneal abscess (K35.32). In accordance with previously published age distributions in patients with acute appendicitis, the study population was divided into three groups: < 15 years, 15–35 years, and > 35 years (e2). The clinical outcome was assessed in terms of in-hospital mortality and indicators of a complicated clinical course. Based on previous research, these indicators were defined by the ICD-10 codes for the secondary diagnoses septicemia and postoperative ileus, the procedure codes for blood transfusions (≥ 6 units), complex intensive care, or mechanical ventilation > 24 hours (etable 1) (16, 17). These indicators were designed to identify serious complications or procedures required for serious complications while being widely unaffected by variation in coding behavior (e3).

Statistical methods

This study follows the REporting of studies Conducted using Observational Routinely collected health Data (RECORD) statement checklist (e4). All calculations were performed using SAS Version 9.3 (SAS Institute Inc., Cary, NC, USA). Data were analyzed descriptively for every year of observation and are expressed as absolute and relative frequencies. Development of appendectomy case numbers over time was analyzed separately for uncomplicated and complicated appendicitis and stratified by age group and hospital size. Additionally, in-hospital mortality and indicators of clinical course were stratified according to uncomplicated or complicated appendicitis.

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