Evaluation of the Open Abdomen Classification System: A Validity and Reliability Analysis

The open abdomen in trauma, acute care, and vascular and endovascular surgery: comprehensive, expert, narrative review

BACKGROUND

The open abdomen is an innovation that greatly improved surgical understanding of damage control, temporary abdominal closure, staged abdominal reconstruction, viscera and enteric fistula care, and abdominal wall reconstruction. This article provides an evidence-informed, expert, comprehensive narrative review of the open abdomen in trauma, acute care, and vascular and endovascular surgery.

METHODS

A group of 12 international trauma, acute care, and vascular and endovascular surgery experts were invited to review current literature and important concepts surrounding the open abdomen.

RESULTS

The open abdomen may be classified using validated systems developed by a working group in 2009 and modified by the World Society of the Abdominal Compartment Syndrome-The Abdominal Compartment Society in 2013. It may be indicated in major trauma, intra-abdominal sepsis, vascular surgical emergencies, and severe acute pancreatitis; to facilitate second look laparotomy or avoid or treat abdominal compartment syndrome; and when the abdominal wall cannot be safely closed. Temporary abdominal closure and staged abdominal reconstruction methods include a mesh/sheet, transabdominal wall dynamic fascial traction, negative pressure wound therapy, and hybrid negative pressure wound therapy and dynamic fascial traction. This last method likely has the highest primary fascial closure rates. Direct peritoneal resuscitation is currently an experimental strategy developed to improve primary fascial closure rates and reduce complications in those with an open abdomen. Primary fascial closure rates may be improved by early return to the operating room; limiting use of crystalloid fluids during the surgical interval; and preventing and/or treating intra-abdominal hypertension, enteric fistulae, and intra-abdominal collections after surgery. The majority of failures of primary fascial closure and enteroatmospheric fistula formation may be prevented using effective temporary abdominal closure techniques, providing appropriate resuscitation fluids and nutritional support, and closing the abdomen as early as possible.

CONCLUSION

Subsequent stages of the innovation of the open abdomen will likely involve the design and conduct of prospective studies to evaluate appropriate indications for its use and effectiveness and safety of the above components of open abdomen management.

The unrestricted global effort to complete the COOL trial

BACKGROUND

Severe complicated intra-abdominal sepsis (SCIAS) has an increasing incidence with mortality rates over 80% in some settings. Mortality typically results from disruption of the gastrointestinal tract, progressive and self-perpetuating bio-mediator generation, systemic inflammation, and multiple organ failure. A further therapeutic option may be open abdomen (OA) management with negative peritoneal pressure therapy (NPPT) to remove inflammatory ascites and attenuate the systemic damage from SCIAS, although there are definite risks of leaving the abdomen open whenever it might possibly be closed. This potential therapeutic paradigm is the rationale being assessed in the Closed Or Open after Laparotomy (COOL trial) ( https://clinicaltrials.gov/ct2/show/NCT03163095 ). Initially, the COOL trial received Industry sponsorship; however, this funding mandated the use of a specific trademarked and expensive NPPT device in half of the patients allocated to the intervention (open) arm. In August 2022, the 3 M/Acelity Corporation without consultation but within the terms of the contract canceled the financial support of the trial. Although creating financial difficulty, there is now no restriction on specific NPPT devices and removing a cost-prohibitive intervention creates an opportunity to expand the COOL trial to a truly global basis. This document describes the evolution of the COOL trial, with a focus on future opportunities for global growth of the study.

METHODS

The COOL trial is the largest prospective randomized controlled trial examining the random allocation of SCIAS patients intra-operatively to either formal closure of the fascia or the use of the OA with an application of an NPPT dressing. Patients are eligible if they have free uncontained intraperitoneal contamination and physiologic derangements exemplified by septic shock OR severely adverse predicted clinical outcomes. The primary outcome is intended to definitively inform global practice by conclusively evaluating 90-day survival. Initial recruitment has been lower than hoped but satisfactory, and the COOL steering committee and trial investigators intend with increased global support to continue enrollment until recruitment ensures a definitive answer.

DISCUSSION

OA is mandated in many cases of SCIAS such as the risk of abdominal compartment syndrome associated with closure, or a planned second look as for example part of "damage control"; however, improved source control (locally and systemically) is the most uncertain indication for an OA. The COOL trial seeks to expand potential sites and proceed with the evaluation of NPPT agnostic to device, to properly examine the hypothesis that this treatment attenuates systemic damage and improves survival. This approach will not affect internal validity and should improve the external validity of any observed results of the intervention.

TRIAL REGISTRATION

National Institutes of Health ( https://clinicaltrials.gov/ct2/show/NCT03163095 ).

The unrestricted global effort to complete the COOL trial

BACKGROUND

Severe complicated intra-abdominal sepsis (SCIAS) has an increasing incidence with mortality rates over 80% in some settings. Mortality typically results from disruption of the gastrointestinal tract, progressive and self-perpetuating bio-mediator generation, systemic inflammation, and multiple organ failure. A further therapeutic option may be open abdomen (OA) management with negative peritoneal pressure therapy (NPPT) to remove inflammatory ascites and attenuate the systemic damage from SCIAS, although there are definite risks of leaving the abdomen open whenever it might possibly be closed. This potential therapeutic paradigm is the rationale being assessed in the Closed Or Open after Laparotomy (COOL trial) ( https://clinicaltrials.gov/ct2/show/NCT03163095 ). Initially, the COOL trial received Industry sponsorship; however, this funding mandated the use of a specific trademarked and expensive NPPT device in half of the patients allocated to the intervention (open) arm. In August 2022, the 3 M/Acelity Corporation without consultation but within the terms of the contract canceled the financial support of the trial. Although creating financial difficulty, there is now no restriction on specific NPPT devices and removing a cost-prohibitive intervention creates an opportunity to expand the COOL trial to a truly global basis. This document describes the evolution of the COOL trial, with a focus on future opportunities for global growth of the study.

METHODS

The COOL trial is the largest prospective randomized controlled trial examining the random allocation of SCIAS patients intra-operatively to either formal closure of the fascia or the use of the OA with an application of an NPPT dressing. Patients are eligible if they have free uncontained intraperitoneal contamination and physiologic derangements exemplified by septic shock OR severely adverse predicted clinical outcomes. The primary outcome is intended to definitively inform global practice by conclusively evaluating 90-day survival. Initial recruitment has been lower than hoped but satisfactory, and the COOL steering committee and trial investigators intend with increased global support to continue enrollment until recruitment ensures a definitive answer.

DISCUSSION

OA is mandated in many cases of SCIAS such as the risk of abdominal compartment syndrome associated with closure, or a planned second look as for example part of "damage control"; however, improved source control (locally and systemically) is the most uncertain indication for an OA. The COOL trial seeks to expand potential sites and proceed with the evaluation of NPPT agnostic to device, to properly examine the hypothesis that this treatment attenuates systemic damage and improves survival. This approach will not affect internal validity and should improve the external validity of any observed results of the intervention.

TRIAL REGISTRATION

National Institutes of Health ( https://clinicaltrials.gov/ct2/show/NCT03163095 ).

Retrospective Study of Indications and Outcomes of Open Abdomen with Negative Pressure Wound Therapy Technique for Abdominal Sepsis in a Tertiary Referral Centre

In patients with advanced sepsis from abdominal disease, the open abdomen (OA) technique as part of a damage control surgery (DCS) approach enables relook surgery to control infection, defer intestinal anastomosis, and prevent intra-abdominal hypertension. Limited evidence is available on key outcomes, such as mortality and rate of definitive fascial closure (DFC), which are needed for surgeons to select patients and adequate therapeutic strategies. Abdominal closure with negative pressure wound therapy (NPWT) has shown rates of DFC around 90%. We conducted a retrospective study to evaluate in-hospital survival and factors associated with mortality in acute, non-trauma patients treated using the OA technique and NPWT for sepsis from abdominal disease. Fifty consecutive patients treated using the OA technique and NPWT between February 2015 and July 2022 were included. Overall mortality was 32%. Among surviving patients, 97.7% of cases reached DFC, and the overall complication rate was 58.8%, with one case of entero-atmospheric fistula. At univariable analysis, age (p = 0.009), ASA IV status (<0.001), Mannheim Peritonitis Index > 30 (p = 0.001) and APACHE II score (p < 0.001) were associated with increased mortality. At multivariable analysis, higher APACHE II was a predictor of in-hospital mortality (OR 2.136, 95% CI 1.08−4.22; p = 0.029). Although very resource-intensive, DCS and the OA technique are valuable tools to manage patients with advanced abdominal sepsis, allowing reduced mortality and high DFC rates.

The Association of Coloproctology of Great Britain and Ireland consensus guidelines in emergency colorectal surgery

AIM

There is a requirement for an expansive and up to date review of the management of emergency colorectal conditions seen in adults. The primary objective is to provide detailed evidence-based guidelines for the target audience of general and colorectal surgeons who are responsible for an adult population and who practise in Great Britain and Ireland.

METHODS

Surgeons who are elected members of the Association of Coloproctology of Great Britain and Ireland Emergency Surgery Subcommittee were invited to contribute various sections to the guidelines. They were directed to produce a pathology-based document using literature searches that were systematic, comprehensible, transparent and reproducible. Levels of evidence were graded. Each author was asked to provide a set of recommendations which were evidence-based and unambiguous. These recommendations were submitted to the whole guideline group and scored. They were then refined and submitted to a second vote. Only those that achieved >80% consensus at level 5 (strongly agree) or level 4 (agree) after two votes were included in the guidelines.

RESULTS

All aspects of care (excluding abdominal trauma) for emergency colorectal conditions have been included along with 122 recommendations for management.

CONCLUSION

These guidelines provide an up to date and evidence-based summary of the current surgical knowledge in the management of emergency colorectal conditions and should serve as practical text for clinicians managing colorectal conditions in the emergency setting.

EWMA Document: Negative Pressure Wound Therapy

1. Introduction Since its introduction in clinical practice in the early 1990's negative pressure wounds therapy (NPWT) has become widely used in the management of complex wounds in both inpatient and outpatient care.¹ NPWT has been described as a effective treatment for wounds of many different aetiologies^2,3 and suggested as a gold standard for treatment of wounds such as open abdominal wounds,^4-6 dehisced sternal wounds following cardiac surgery^7,8 and as a valuable agent in complex non-healing wounds.^9,10 Increasingly, NPWT is being applied in the primary and home-care setting, where it is described as having the potential to improve the efficacy of wound management and help reduce the reliance on hospital-based care.¹¹ While the potential of NPWT is promising and the clinical use of the treatment is widespread, highlevel evidence of its effectiveness and economic benefits remain sparse.^12-14 The ongoing controversy regarding high-level evidence in wound care in general is well known. There is a consensus that clinical practice should be evidence-based, which can be difficult to achieve due to confusion about the value of the various approaches to wound management; however, we have to rely on the best available evidence. The need to review wound strategies and treatments in order to reduce the burden of care in an efficient way is urgent. If patients at risk of delayed wound healing are identified earlier and aggressive interventions are taken before the wound deteriorates and complications occur, both patient morbidity and health-care costs can be significantly reduced. There is further a fundamental confusion over the best way to evaluate the effectiveness of interventions in this complex patient population. This is illustrated by reviews of the value of various treatment strategies for non-healing wounds, which have highlighted methodological inconsistencies in primary research. This situation is confounded by differences in the advice given by regulatory and reimbursement bodies in various countries regarding both study design and the ways in which results are interpreted. In response to this confusion, the European Wound Management Association (EWMA) has been publishing a number of interdisciplinary documents^15-19 with the intention of highlighting: The nature and extent of the problem for wound management: from the clinical perspective as well as that of care givers and the patients Evidence-based practice as an integration of clinical expertise with the best available clinical evidence from systematic research The nature and extent of the problem for wound management: from the policy maker and healthcare system perspectives The controversy regarding the value of various approaches to wound management and care is illustrated by the case of NPWT, synonymous with topical negative pressure or vacuum therapy and cited as branded VAC (vacuum-assisted closure) therapy. This is a mode of therapy used to encourage wound healing. It is used as a primary treatment of chronic wounds, in complex acute wounds and as an adjunct for temporary closure and wound bed preparation preceding surgical procedures such as skin grafts and flap surgery. Aim An increasing number of papers on the effect of NPWT are being published. However, due to the low evidence level the treatment remains controversial from the policy maker and health-care system's points of view-particularly with regard to evidence-based medicine. In response EWMA has established an interdisciplinary working group to describe the present knowledge with regard to NPWT and provide overview of its implications for organisation of care, documentation, communication, patient safety, and health economic aspects. These goals will be achieved by the following: Present the rational and scientific support for each delivered statement Uncover controversies and issues related to the use of NPWT in wound management Implications of implementing NPWT as a treatment strategy in the health-care system Provide information and offer perspectives of NPWT from the viewpoints of health-care staff, policy makers, politicians, industry, patients and hospital administrators who are indirectly or directly involved in wound management.

Vacuum-Assisted Wound Closure and Permanent Onlay Mesh-Mediated Fascial Traction: A Novel Technique for the Prevention of Incisional Hernia after Open Abdomen Therapy Including Results From a Retrospective Case Series

BACKGROUND AND AIMS

Incisional hernia development is a frequent long-term sequel after open abdomen treatment. This report describes a novel technique, the vacuum-assisted wound closure and permanent onlay mesh-mediated fascial traction for temporary and final closure of the open abdomen, with the intention to decrease incisional hernia rates. Primary aim was to evaluate incisional hernia development and secondary aims to describe short-term complications and patient-reported outcome.

MATERIALS AND METHODS

The basics of the technique is an onlay mesh, applied early during open abdomen treatment by suturing to the fascia in two rows with a 3- to 4-cm overlap from the midline incision, used for traction and kept for reinforced permanent closure. A retrospective case series, including chart review, evaluation of computed tomography/ultrasound images, and an out-patient clinical examination were performed. The patients were asked to answer a modified version of the ventral hernia pain questionnaire.

RESULTS

A total of 11 patients were treated with vacuum-assisted wound closure and permanent onlay mesh-mediated fascial traction with median follow-up of 467 days. Fascial closure rate was 100% and 30 day mortality 0%. Two of nine patients, eligible for incisional hernia follow-up, developed a hernia. Neither of the hernias were symptomatic nor clinically detectable. Six of 10 patients eligible for short-term follow-up had a prolonged wound-healing time exceeding 3 weeks. One of seven patients eligible for patient-reported outcome have had pain during the last week.

CONCLUSION

The vacuum-assisted wound closure and permanent onlay mesh-mediated fascial traction is a promising new technique for open abdomen treatment and reinforced fascial closure. The results of the first 11 patients treated with this technique show a low incisional hernia rate with manageable short-term wound complications and few patient-reported disadvantages.

The open abdomen: analysis of risk factors for mortality and delayed fascial closure in 101 patients

Introduction

The core concepts of damage control and open abdomen in trauma surgery have been expanding for emergent general surgery. Temporary closures allow ease of access to the abdominal cavity for source control.The aim of the current study was to assess the outcomes of patients who underwent open abdomen management for acute abdominal conditions and evaluate risk factors for worse outcomes and inability of fascial closure during the initial hospitalization.

Methods

We conducted a retrospective analysis of 101 patients submitted to laparostomy in a single institution from January 2009 to March 2017. The evaluated outcomes were mortality, local morbidity, and rate of primary fascial closure.

Results

The most common indications for open abdomen were bowel perforation, bowel ischemia, and necrotizing pancreatitis. Global in-hospital mortality rate was 62.4%. For the 37 patients discharged from the hospital, a definitive abdominal closure was attained in 28.Multivariable logistic regression analysis revealed that people older than 60 years of age and with Acute Physiology and Chronic Health Evaluation (APACHE II) scores over 18.5 had higher in-hospital mortality rates. Definitive fascial closure was statistically associated with a lower number of re-interventions and ICU stay.

Conclusions

Open abdomen management may be appropriate in these critically ill patients; however, it continues to be associated with significantly high mortality, especially in elder patients and with higher APACHE II scores. Recognition of risk factors for fascia closure failure should promote the investigation for a tailored surgical approach in these patients.

Closed Or Open after Source Control Laparotomy for Severe Complicated Intra-Abdominal Sepsis (the COOL trial): study protocol for a randomized controlled trial

Background

Severe complicated intra-abdominal sepsis (SCIAS) has an increasing incidence with mortality rates over 80% in some settings. Mortality typically results from disruption of the gastrointestinal tract, progressive and self-perpetuating bio-mediator generation, systemic inflammation, and multiple organ failure. Principles of treatment include early antibiotic administration and operative source control. A further therapeutic option may be open abdomen (OA) management with active negative peritoneal pressure therapy (ANPPT) to remove inflammatory ascites and ameliorate the systemic damage from SCIAS. Although there is now a biologic rationale for such an intervention as well as non-standardized and erratic clinical utilization, this remains a novel therapy with potential side effects and clinical equipoise.

Methods

The Closed Or Open after Laparotomy (COOL) study will constitute a prospective randomized controlled trial that will randomly allocate eligible surgical patients intra-operatively to either formal closure of the fascia or use of the OA with application of an ANPTT dressing. Patients will be eligible if they have free uncontained intra-peritoneal contamination and physiologic derangements exemplified by septic shock OR a Predisposition-Infection-Response-Organ Dysfunction Score ≥ 3 or a World-Society-of-Emergency-Surgery-Sepsis-Severity-Score ≥ 8. The primary outcome will be 90-day survival. Secondary outcomes will be logistical, physiologic, safety, bio-mediators, microbiological, quality of life, and health-care costs. Secondary outcomes will include days free of ICU, ventilation, renal replacement therapy, and hospital at 30 days from the index laparotomy. Physiologic secondary outcomes will include changes in intensive care unit illness severity scores after laparotomy. Bio-mediator outcomes for participating centers will involve measurement of interleukin (IL)-6 and IL-10, procalcitonin, activated protein C (APC), high-mobility group box protein-1, complement factors, and mitochondrial DNA. Economic outcomes will comprise standard costing for utilization of health-care resources.

Discussion

Although facial closure after SCIAS is considered the current standard of care, many reports are suggesting that OA management may improve outcomes in these patients. This trial will be powered to demonstrate a mortality difference in this highly lethal and morbid condition to ensure critically ill patients are receiving the best care possible and not being harmed by inappropriate therapies based on opinion only.

Trial registration

ClinicalTrials.gov, NCT03163095.

Open Abdomen Treated with Negative Pressure Wound Therapy: Indications, Management and Survival

BACKGROUND

Open abdomen treatment (OAT) is a significant burden for patients and is associated with considerable mortality. The primary aim of this study was to report survival and cause of mortality after OAT. Secondary aims were to evaluate length of stay (LOS) in intensive care unit (ICU) and in hospital, time to abdominal closure and major complications.

METHODS

Retrospective review of prospectively registered patients undergoing OAT between October 2006 and June 2014 at Trondheim University Hospital, Norway.

RESULTS

The 118 patients with OAT had a median age of 63 (20-88) years. OAT indications were abdominal compartment syndrome (ACS) (n = 53), prophylactic (n = 29), abdominal contamination/second look laparotomy (n = 22), necrotizing fasciitis (n = 7), hemorrhage packing (n = 4) and full-thickness wound dehiscence (n = 3). Eight percent were trauma patients. Vacuum-assisted wound closure (VAWC) with mesh-mediated traction (VAWCM) was used in 92 (78 %) patients, the remaining 26 (22 %) had VAWC only. Per-protocol primary fascial closure rate was 84 %. Median time to abdominal closure was 12 days (1-143). LOS in the ICU was 15 (1-89), and in hospital 29 (1-246) days. Eighty-one (68 %) patients survived the hospital stay. Renal failure requiring renal replacement therapy (RRT) (OR 3.9, 95 % CI 1.37-11.11), ACS (OR 3.1, 95 % CI 1.19-8.29) and advanced age (OR 1.045, 95 % CI 1.004-1.088) were independent predictors of mortality in multivariate analysis. The nine patients with an entero-atmospheric fistula (EAF) survived.

CONCLUSION

Two-thirds of the patients treated with OAT survived. Renal failure with RRT, ACS and advanced age were predictors of mortality, whereas EAF was not associated with increased mortality.

Negative-pressure wound therapy for prevention and treatment of surgical-site infections after vascular surgery

BACKGROUND

Indications for negative-pressure wound therapy (NPWT) in vascular surgical patients are expanding. The aim of this review was to outline the evidence for NPWT on open and closed wounds.

METHODS

A PubMed, EMBASE and Cochrane Library search from 2007 to June 2016 was performed combining the medical subject headings terms 'wound infection', 'abdominal aortic aneurysm (AAA)', 'fasciotomy', 'vascular surgery' and 'NPWT' or 'VAC'.

RESULTS

NPWT of open infected groin wounds was associated with shorter duration of wound healing by 47 days, and was more cost-effective than alginate dressings in one RCT. In one RCT and six observational studies, NPWT-related major bleeding and graft preservation rates were 0-10 and 83-100 per cent respectively. One retrospective comparative study showed greater wound size reduction per day, fewer dressing changes, quicker wound closure and shorter hospital stay with NPWT compared with gauze dressings for lower leg fasciotomy. NPWT and mesh-mediated fascial traction after AAA repair and open abdomen was associated with high primary fascial closure rates (96-100 per cent) and low risk of graft infection (0-7 per cent). One retrospective comparative study showed a significant reduction in surgical-site infection, from 30 per cent with standard wound care to 6 per cent with closed incisional NPWT.

CONCLUSION

NPWT has a central role in open and infected wounds after vascular surgery; the results of prophylactic care of closed incisions are promising.

Anatomical, physiological, and logistical indications for the open abdomen: a proposal for a new classification system

Background

A systematic approach to the appropriate use of the open abdomen strategy has not been described. We propose three fundamental reasons for the use of this strategy, anatomical, physiological and logistical. Anatomical reasons pertain to the inability to bring the fascial edges together including soft tissue defects. Physiological reasons relate to features of systemic dysfunction. Logistical reasons involve any anticipated abdominal re-intervention while preserving fascia. These categories occur either as a single reason or in any combination.

Methods

A single-center prospective observational study of patients with open abdomens in trauma and acute abdomen. Surgeons were asked to select from the three reasons (single or any combination of) their motivation for using the open abdomen upon completion of the initial operation. Patients were compared using the non-parametric Wilcoxon two-sample test or Kruskal-Wallis test. Chi-square or Fisher’s exact test was used for categorical variables; Statistical significance set at P-value ≤ 0.05.

Results

Forty-five consecutive patients with open abdomens were evaluated (Jan. 1- Dec. 31, 2012). Mean age was 38.8 years, 32 were male, 39 (86.7 %) sustained trauma. The most common single reason for the open abdomen was physiological (24.4 %), 33 patients had multiple reasons, the most common combination being anatomical and physiological (22.2 %). A physiological reason was linked to: lower pH, higher lactate, and lower systolic blood pressure on admission (p < 0.05). A logistical reason was associated with earlier primary fascial closure, intra-operative packing, and bowel left in discontinuity. Logistic regression and adjusted odds ratio of primary fascial closure was: physiological (0.08, 95 % CI, 0.01–0.92, p = 0.043); logistical (6.03, 95 % CI, 1.13–32.29, p = 0.036); and anatomical (0.83, 95 % CI, 0.16–4.18, p = 0.816).

Conclusion

We defined three basic indications for the use of the open abdomen, anatomical physiological and logistical. These indications establish a practical and comprehensive terminology that could help to promote appropriate use of the open abdomen.

Amended Classification of the Open Abdomen

BACKGROUND

In 2009, a classification system for the open abdomen was introduced. The aim of such a classification is to aid the (1) description of the patient's clinical course; (2) standardization of clinical guidelines for guiding open abdomen management; and (3) facilitation of comparisons between studies and heterogeneous patient populations, thus serving as an aid in clinical research.

METHODS

As part of the revision of the definitions and clinical guidelines performed by the World Society of the Abdominal Compartment Syndrome, this 2009 classification system was amended following a review of experiences in teaching and research and published as part of updated consensus statements and clinical practice guidelines in 2013. Among 29 articles citing the 2009 classification system, nine were cohort studies. They were reviewed as part of the classification revision process. A total of 542 patients (mean: 60, range: 9-160) had been classified. Two problems with the previous classification system were identified: the definition of enteroatmospheric fistulae, and that an enteroatmospheric fistula was graded less severe than a frozen abdomen.

RESULTS

The following amended classification was proposed: Grade 1, without adherence between bowel and abdominal wall or fixity of the abdominal wall (lateralization), subdivided as follows: 1A, clean; 1B, contaminated; and 1C, with enteric leak. An enteric leak controlled by closure, exteriorization into a stoma, or a permanent enterocutaneous fistula is considered clean. Grade 2, developing fixation, subdivided as follows: 2A, clean; 2B, contaminated; and 2C, with enteric leak. Grade 3, frozen abdomen, subdivided as follows: 3A clean and 3B contaminated. Grade 4, an established enteroatmospheric fistula, is defined as a permanent enteric leak into the open abdomen, associated with granulation tissue.

CONCLUSIONS

The authors believe that, with these changes, the requirements on a functional and dynamic classification system, useful in both research and training, will be fulfilled. We encourage future investigators to apply the system and report on its merits and constraints.