Organ Injury Scaling

The Organ Injury Scaling (OIS) Committee of the American Association for the Surgery of Trauma (AAST) was organized formally in 1987; the fundamental purpose was to devise injury severity scores for individual organs to facilitate clinical investigation and outcomes research. The OIS Committee members were selected on the basis of recognized clinical expertise as well as experience with injury scoring. The Committee was charged to develop a comprehensive set of OISs, monitor their application in the current literature, and recommend modifications when deemed appropriate. The following OISs for spleen and liver represent the first revisions in this long term project. Conceptually, the OIS is a classification scheme based on the anatomic disruption of an individual organ scaled 1 to 6, representing the least to most severe injury. Grades 1 to 5 represent increasingly complex injuries encountered in salvageable patients, while grade 6 is a destructive lesion incompatible with survival. Severity is based on potential threat to the patient's life, and the progressive scale derived from a comprehensive review of the current literature with consensus of the OIS Committee. Finally, the AAST Board of Managers approves all OISs prior to submission for publication. Despite this extensive preparation process, OISs are inherently limited by design as ordinal rather than interval scales. For example, the difference between a grade I versus II injury is generally less significant clinically than a grade IV versus V. The fundamental objective of the OIS, however, is not to assign prognostic value to a specific injury, but rather to provide a clearer description to facilitate comparison of an equivalent injury managed in one fashion versus another. To date, OISs have been developed and published in the Journal of Trauma for spleen, liver, kidney, [1] pancreas, duodenum, small bowel, colon, rectum, [2] chest wall, abdominal vascular, ureter, bladder, urethra, [3] and thoracic vascular, lung, cardiac, diaphragm. [4] While many of these OISs have been employed in clinical research, the individual scaling grades have not been studied independently for scientific accuracy. Nonetheless, with increased clinical testing and constructive review by other investigators, the need for revisions has become apparent. Spleen and liver OISs, first published in 1989, [1] have been applied frequently in the literature over the past five years, and describe two ongoing controversial areas in trauma care. Consequently, it is not surprising that revisions for these two OISs have become necessary. Some of these modifications were straightforward, while others required considerable deliberation of the OIS committee before a consensus could be reached. The significant revisions in the spleen and liver OIS include: 1) global downgrading of hematomas for both spleen and liver, acknowledging their relatively benign course with the advent of widespread CT scanning for blunt abdominal trauma, 2) addition of Couinard's segmental liver anatomy to facilitate quantification of lobar parenchymal disruption, employing internationally familiar terminology, 3) more rigorous criteria for grade IV and V hepatic injuries, recognizing the need to further delineate the operative challenges of these advanced lesions, and 4) restricting the advancement of one grade for multiple injuries within an OIS to grade III. The revised scale for spleen OIS is depicted in Table 1. The specific changes are increased threshold hematoma size to > 5cm for grade III, and elimination of ruptured intraparenchymal hematoma as a grade IV injury. The changes for the revised liver OIS (Table 2) are increased threshold hematoma size to > 10cm for grade III, increased amount of parenchyma involved to > 75% for grade V, and the addition of equivalent Counard segments for grade IV and grade V.Table 1: Spleen injury scale (1994 revision).Table 2: Liver injury scale (1994 revision).We hope these modifications will be helpful to those who employ OISs to improve care of the injured, and look forward to the evaluation of their scientific validity by experienced trauma surgeons.