Enhancements in helical computed tomography (CT) and angioembolization techniques have expanded the use and success of NOM of splenic injury over the past few decades. Approximately 85 % of adult patients with blunt splenic injury now undergo NOM with success rates varying between 70 and 90 % [3]. NOM consists of observation, intensive monitoring, serial abdominal examinations, serial hemoglobin/hematocrit measurements, and occasionally repeat CT imaging. Angioembolization, in select patients, remains a useful adjunct and has increased the success of NOM significantly.

To forgo laparotomy in favor of NOM a number of criteria must be met; the patient must be hemodynamically stable, must exhibit no peritoneal signs, and the setting in which NOM is being considered must be suitable. The appropriate setting entails a dedicated area for observation and intensive monitoring (e.g., an ICU), the capability of serial and frequent abdominal examinations by the same surgical team, and easy and rapid access to an operating room if necessary (Table 17.1). If any of these criteria are not met, then attempting NOM is potentially hazardous. On the other hand, if all of these criteria are met, then the practice management guideline committee for the Eastern Association for the Surgery of Trauma (EAST) developed a level 2 guideline suggesting that NOM may be attempted regardless of age, neurologic status, injury severity or the presence of associated extra-abdominal injuries [3].

Another useful tool in the decision-making armamentarium is the severity of the splenic injury as visualized upon CT imaging. The American Association for the Surgery of Trauma Organ Injury Scale provides the clinician with an injury grading scale from which management decisions can be made [4]. This scale is detailed in Table 17.2 and Fig. 17.2. Success rates of NOM, however, do vary according to the AAST injury severity. Patients with grade III injuries with large hemoperitoneum, or with grade 4 and 5 injuries are at higher risk of failure. A multi-institutional study demonstrated failure rates of 34.5 % for grade IV injuries, and 60 % for grade V injuries [5].