The Journal of TRAUMA Injury, Infection, and Critical Care

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1 Isolated Free Fluid on Computed Tomographic Scan in Blunt Abdominal Trauma: A Systematic Review of Incidence and Management Christian Rodriguez, MD, James E. Barone, MD, Tyr O. Wilbanks, MD, Chan-Kook Rha, MD, and Kevin Miller, MD Background: Abdominal computed tomographic (CT) scan is accepted as the primary diagnostic modality in stable patients with blunt abdominal trauma. A recent survey of 328 trauma surgeons demonstrated marked variation in the management of patients with head injuries and the finding of free intra-abdominal fluid without solid organ injury on CT scan. This study was undertaken to attempt to determine what to do when free fluid without solid organ injury is seen on abdominal CT scan in patients with blunt trauma. Methods: Articles concerning the incidence and significance of free intra-abdominal fluid on CT scan of blunt trauma patients without solid organ injury were systematically reviewed. A MEDLINE search was performed using terms such as tomography-x-ray computed, woundsnonpenetrating, small intestine/injuries, time factors, and abdominal trauma and diagnostic tests. Bibliographies of pertinent articles were reviewed. Appropriate articles were evaluated for quality and data were combined to reach a conclusion. Results: Meta-analysis could not be performed because no randomized, prospective, controlled trials could be found. Forty-one articles were excluded from the analysis because they looked at only patients with known injuries to intestine, diaphragm, or pancreas and the investigation of the CT scan findings did not include negative scans. Ten articles, which described CT scan results for all patients presenting with blunt abdominal trauma for a defined period of time, formed the basis of this study. Isolated free fluid was seen in 463 (2.8%) of over 16,000 blunt trauma patients scanned. A therapeutic laparotomy was performed in only 122 (27%) of these patients. Conclusion: The isolated finding of free intra-abdominal fluid on CT scan in patients with blunt trauma and no solid organ injury does not warrant laparotomy. Alert patients may be followed with physical examination. Patients with altered mental status should undergo diagnostic peritoneal lavage. Key Words: Blunt abdominal trauma, Diagnostic peritoneal lavage, Tomography-x-ray computed, Wounds-nonpenetrating, Small intestine/injuries, Time factors, Abdominal trauma and diagnostic tests. J Trauma. 2002;53: In alert patients, physical examination is regarded as the best method of determining the presence of significant abdominal injury. In patients with altered mental status, abdominal/pelvic computed tomographic (CT) scan is the diagnostic imaging modality of choice in the hemodynamically stable blunt trauma patient. Its advantages over diagnostic peritoneal lavage (DPL) and ultrasound are that it not only can demonstrate the presence of hemorrhage but also can identify the involved organ. As opposed to DPL or ultrasound, CT scanning may also reveal the presence of retroperitoneal injuries. One of its main drawbacks, however, is its poor sensitivity in the diagnosis of hollow viscus injuries. Submitted for publication August 17, Accepted for publication December 14, Copyright 2002 by Lippincott Williams & Wilkins, Inc. From the Department of Surgery (C.R., K.M.) and the Stamford Hospital/Columbia University College of Physicians and Surgeons Program in Surgery (J.E.B., T.O.W., C.-K.R.), Stamford Hospital, Stamford, Connecticut. Address for reprints: James E. Barone, MD, Department of Surgery, Stamford Hospital, P.O. Box 9317, Stamford, CT 06904; drjbarone@ stamhosp.chime.org. As nonoperative management of solid organ injury is now established, there is a growing concern for missing hollow viscus injuries. In the patient with solid organ injury, the presence of fluid on abdominal CT scan is thought to represent blood from the injured solid organ. Free fluid without solid organ injury may represent an undetected solid organ injury, bleeding from the mesentery not necessarily requiring operative intervention, or a missed bowel injury. What does one do when faced with a hemodynamically stable blunt trauma patient whose abdominal CT scan shows free fluid but no solid organ injury? To attempt to answer this question, Brownstein et al. 1 recently conducted a survey of members of the American Association for the Surgery of Trauma. They noted a variety of responses. A hypothetical stable patient with a head injury, intra-abdominal free fluid, and no solid organ injury on CT scan was presented. When asked to identify the next step in management, 42% of the 328 respondents said they would perform a DPL, 28% said they would observe the patient, 16% said they would perform laparotomy, and 12% said they would repeat the CT scan. The research question is, What is the optimal management of the stable blunt trauma patient whose abdominal CT scan shows only free fluid without solid organ injury? Our Volume 53 Number 1 79

2 objectives were to systematically review the recent literature and attempt to determine the following: the incidence of isolated free fluid on abdominal CT scans in blunt trauma; the percentage of patients with isolated free fluid who underwent a therapeutic laparotomy; and practical guidelines for the management of patients with the finding of isolated free fluid but no solid organ injury. PATIENTS AND METHODS We conducted a systematic review of the literature from the years 1990 to May This time period was chosen because it represents the era of modern CT scanning. A MEDLINE search using the OVID database was conducted. The search was limited to articles published in English. The following search terms were used: tomography-x-ray computed; wounds-nonpenetrating; small intestine/injuries, time factors; and abdominal trauma and diagnostic tests. The MEDLINE search was supplemented by reviewing bibliographies of appropriate articles and files of the senior author (J.E.B.). Articles were included in the systematic review if they dealt with the subject of isolated free fluid on abdominal CT scans from the perspective of all patients presenting with such findings. Articles reporting only those patients with known injuries, such as those based on all patients who suffered blunt injury to the small intestine, were excluded. RESULTS Fifty-one articles that involved blunt trauma and abdominal CT scans were found. Forty-one articles were excluded from the combined analysis because they approached the subject by using the number of patients with known injuries as the basis of the study or because of lack of data on the number of patients with isolated intraperitoneal free fluid. Tables 1 through lists all of these articles with the reason for exclusion from the combined analysis. The 10 articles listed in Table contained appropriate data for analysis. A meta-analysis could not be performed because all of the studies were observational. No study compared diagnostic and therapeutic strategies in a prospective fashion. As shown in Table 4, of the more than 16,176 patients scanned (not including the study by Levine et al., which did not enumerate the total number of patients scanned), 463 patients had the finding of isolated free fluid without solid organ injury on CT scan. Isolated free fluid was seen in 2.8% of all blunt trauma patients scanned. Only 122 of these patients underwent a therapeutic laparotomy. In the combined analysis, only 27% of patients with isolated free fluid had a therapeutic laparotomy. The larger the amount of fluid, the more likely an intestinal injury would be found. The number of false-negatives, that is, CT scans showing no fluid but patients having intestinal injuries, could not be determined from most of the articles. Table 1 Articles Excluded from the Systematic Review: Studies Based on Patients with Known Injuries Authors Year Hackam et al Fakhry et al Pikoulis et al Neugebauer et al Frick et al Fang et al Harris et al Janzen et al Kemmeter et al Kafie et al Jerby et al Kurkchubasche et al Dowe et al Albanese et al Moss et al Bloom et al Bensard et al Celeen et al Hagiwara et al Talton et al Sugimoto et al Mirvis et al Ceraldi and Waxman Wisner et al DISCUSSION The controversy regarding the management of patients with isolated intraperitoneal free fluid on abdominal CT scan is understandable. Four quotes from the recent surgical literature help to illustrate the point (Table 5). The survey by Brownstein et al. 1 reported that nearly three fourths of the respondents stated they made their treatment decisions on the basis of their experience rather than on the basis of evidencebased medicine. The systematic review demonstrates that the incidence of isolated free fluid is very low, occurring in only 2.8% of all CT scans for blunt abdominal trauma. Most surgeons have infrequent opportunities to deal with this problem. Personal experience would be inadequate to base treatment on. Table 2 Articles Excluded from the Systematic Review: Studies in which the Total Number of Patients with Free Fluid Was Not Stated Authors Year Stafford et al. 26 Tsang et al Jhirad and Boone Udekwu et al Federle et al Grieshop et al Sriussadaporn Clancy et al Padhani et al Meredith et al July 2002

3 Isolated Free Fluid on CT Scan in Blunt Abdominal Trauma Table 3 Articles Excluded from the Systematic Review: Other Excluded Studies Authors Year Reason for Exclusion Breen et al Patients with known bowel injuries compared to those without Chandler et al Study of seat belts and association with intra-abdominal injury Shapiro et al Patients with known diaphragmatic injuries Nolan et al Study based on patients with known mesenteric injuries Ngheim et al Review article Hamilton et al Study on the topic of extraluminal air Sherck and Oates Report of 10 cases of missed bowel injury Holmes and colleagues 43 prospectively observed 527 children with blunt abdominal trauma. Isolated intraperitoneal fluid on CT scan was noted in 42 patients, 4 of whom underwent therapeutic laparotomy. The authors used the classification system of Federle and Jeffrey 53 to grade the amount of intraperitoneal fluid as small (limited to one defined anatomic region), moderate (one anatomic region and the pelvis), or large (fluid in the pelvis and at least two other anatomic regions). They suggested that patients with small amounts of fluid were less likely to require exploration. All patients with therapeutic laparotomies had abdominal tenderness on examination. No patient with isolated free fluid who was conscious without abdominal pain had an intra-abdominal injury. They recommended that all patients with abdominal pain and isolated free fluid should be admitted to the hospital for repeat physical examinations. Ng et al. 45 reported that of 1,367 patients with blunt abdominal trauma, 28 (2%) had isolated free fluid on abdominal CT scan. Of 21 immediate laparotomies performed, 16 were therapeutic. Two of the seven patients initially observed underwent laparotomy within 24 hours for missed injuries. These authors identified seat belt ecchymosis and pelvic fracture as factors associated with bowel injury. Although Table 4 Results of the Systematic Review Authors Year No. of Patients Scanned No. with Isolated Fluid Therapeutic Laparotomy Holmes et al Malhotra et al , Ng et al , Brasel et al , Cunningham et al Hulka et al Livingston et al , Levine et al Not stated 60 5 Eaniello et al Sherck et al Total (%) 16, (2.8) 124 (27) Table 5 Difference of Opinion Regarding the Significance of Free Intra-abdominal Fluid without Solid Organ Injury on CT Scan We cannot support using the presence of free fluid as a trigger for mandatory celiotomy after blunt abdominal trauma. Livingston et al. 49, The presence of more than trace amounts of free fluid without solid organ injury in patients with blunt trauma is a strong indication for celiotomy. Brasel et al. 46, Intra-abdominal fluid as the sole finding on abdominal CT scan dose not mandate immediate celiotomy in the bluntly injured pediatric patient. Hulka et al. 48, The finding of free fluid in the absence of solid organ injury in blunt abdominal trauma is associated with a high rate of clinically significant visceral injury. Mandatory exploratory laparotomy is recommended. Ng et al. 45, they stated that CT scan findings were unreliable in estimating injury severity, they recommended mandatory laparotomy for patients with isolated free fluid on CT scan. In a series of over 8,100 of patients undergoing CT scan for blunt abdominal trauma, Malhotra et al. 44 noted seven patients with bowel or mesenteric injuries who had negative preoperative CT scans. They found that patients with significant intra-abdominal injuries usually had multiple positive findings at CT scan. In addition to isolated free fluid, signs of bowel or mesenteric injury included pneumoperitoneum, mesenteric streaking or hematoma, thickened bowel wall, and extravasation of luminal or vascular contrast material. They proposed an algorithm for the evaluation of patients with a solitary abnormal finding on CT scan, suggesting that patients with free fluid undergo DPL, but did not define criteria for a positive lavage. The group led by Brasel 46 found isolated free fluid in 3% of 1,141 patients who underwent abdominal CT scan for blunt trauma. Although their rate of therapeutic laparotomy was only 7 of 13 (54%), they recommended abdominal exploration for any patient with more than a trace amount of isolated fluid. A trace amount of fluid was defined as fluid seen on one to three CT scan sections. Cunningham et al. 47 studied 798 patients who underwent abdominal CT scanning for blunt trauma. Isolated free fluid was found in 31 patients. All of these patients underwent exploratory laparotomy, with 29 interventions listed as therapeutic. This therapeutic laparotomy rate of 94% was much higher than all of the other studies systematically reviewed. Although this article was accompanied by a discussion that contained a specific question about the high rate of therapeutic laparotomy, the discrepancy between this and most of the other articles on the subject of isolated free fluid in the abdomen after blunt trauma was not reconciled. Hulka s group 48 reported a 9% (24 of 259) incidence of isolated intra-abdominal fluid on CT scan for blunt trauma in children. Using the fluid classification system of Federle and Jeffrey, 53 the authors found that patients with a moderate amount of fluid were statistically significantly more likely to Volume 53 Number 1 81

4 Fig. 1. Proposed algorithm for the management of patients with isolated free fluid on abdominal CT scan. PE, physical examination. need a therapeutic laparotomy than those who had only a small amount of fluid present. The multicenter study led by Livingston 49 found free intraperitoneal fluid without solid or injury in 90 of 2,299 (4%) patients over 16 years of age. Patients with Glasgow Coma Scale scores 14 were excluded. Important findings of this study included the following: physical findings did not predict an abnormal CT scan; preliminary and final CT scan readings concurred in 92% of patients; only 7 of 90 patients with isolated intra-abdominal free fluid had therapeutic laparotomies; bowel injury was found in 25 patients, with CT scan accurately making the diagnosis in 22; and 3 patients with negative abdominal CT scans were later found to have bowel injuries requiring surgery. Levine et al. 50 noted 60 patients with isolated intraabdominal free fluid after blunt trauma. They categorized the amount of fluid by the number of consecutive CT scan sections: minimal, fewer than three sections; moderate, four to five sections; and marked, more than six sections. The rate of therapeutic laparotomy in this series was only 8.3%. The early diagnosis of hollow viscus injuries in patients suffering blunt abdominal trauma is difficult. Furthermore, a delay in the diagnosis of such injuries may be associated with increased morbidity and mortality. According to the combined analysis, immediate laparotomy for all patients with isolated intraperitoneal free fluid would yield a negative laparotomy rate of 73%. This is clearly unacceptable. Conversely, observation alone would lead to a delay in diagnosis of the 27% of patients who do have a bowel injury. The effect of delay in diagnosis on patient outcome is not agreed on. Fakhry et al. 3 reviewed registry data from North Carolina and found that delays in diagnosis of blunt small bowel injury of 8 hours caused excess morbidity. However, Fang and colleagues 7 studied 111 cases of blunt small bowel perforation. They divided the patients into four groups according to the time elapsed between the injury and laparotomy. They found that the complication rate was significantly higher only in those patients whose surgical procedure was delayed for at least 24 hours. Similarly, Bensard and associates 18 did not observe increased morbidity or hospital length of stay in children whose surgery was delayed for an average of 36 hours. Some authors have tried to identify patients at risk for serious intra-abdominal injury. The presence of a seat belt sign, or ecchymosis corresponding to the location of a passenger restraint device, has been associated with an increased number of injuries requiring laparotomy in one studies. Chandler et al. 37 reviewed 117 blunt trauma patients and noted that 5 of 14 (36%) patients with the seat belt sign had intraabdominal injuries requiring a therapeutic laparotomy. Only 4 of 103 (3%) patients without the sign needed therapeutic laparotomy. The difference was statistically significant. These findings were supported by Ng et al. 45 and Bensard et al. 18 However, the multicenter study by Livingston et al. 49 demonstrated no such relationship of the presence of a seat belt sign and injury requiring treatment. Dowe et al. 14 reported that the combination of mesenteric bleeding or hematoma associated with thickened bowel wall on CT scan re- 82 July 2002

5 Isolated Free Fluid on CT Scan in Blunt Abdominal Trauma sulted in a high likelihood of a significant injury being found at laparotomy. Permeation of the mesentery with blood in the absence of bowel wall thickening was nonspecific. Even the presence of free air on abdominal CT scan is not necessarily associated with the need for laparotomy. In 1995, Hamilton et al. 41 described seven patients with intra-abdominal free air detected by CT scan. None of these patients, two of whom underwent laparotomy and five of whom were followed clinically, had intra-abdominal disease. Because all of the patients had chest tubes in place before their CT scans, the air in the peritoneal cavity was presumed to have come from an injury to the lung. Another diagnostic modality would be quite useful, but few options exist. Serial physical examination is notoriously inconsistent in the diagnosis of hollow viscus injury until the occurrence of significant peritonitis. Holmes et al. 43 and Hulka et al. 48 feel that physical examination can be useful in selecting those patients who will need surgery. In pediatric patients, articles supporting the value of physical examination of the abdomen were published by Jerby et al. 12 and Kurkchubasche et al. 13 Livingston et al., 49 Fang et al., 7 and Dowe et al. 14 reached the opposite conclusion regarding the utility of physical examination in adults. In all three studies, abdominal pain was quite insensitive as an indicator of serious intra-abdominal injury. In addition, many blunt trauma patients have neurologic dysfunction secondary to head trauma or intoxication, which renders physical examination unreliable. Repeat CT scan is another option, but CT scan does not have good sensitivity in the diagnosis of bowel injuries. It is not clear that repeating the CT scan would add much to the decision-making process, and a study validating this idea has not been published. The systematic literature review suggests that patients with isolated intra-abdominal fluid in the absence of solid organ injury on CT scan should undergo DPL. Those patients with a positive DPL should go on to laparotomy. The traditional definition of a positive DPL is fluid recovered from the lavage with a red blood cell (RBC) count 100,000/mm 3 ;a white blood cell (WBC) count 500/mm 3 ; amylase 100 IU/L; or the presence of bile, bacteria, or particulate matter. In a recent small series of patients, Jackson et al. 54 stated that a DPL WBC count of 500/mm 3 had both a sensitivity and a negative predictive value of 100%, but a positive predictive value of only 35%. Sozuer et al. 55 also questioned the standard diagnostic criteria, citing a false-positive rate of 23.9% in their series of 2,010 patients with blunt abdominal trauma who underwent DPL. A lavage fluid WBC count of 500/ mm 3 had a positive predictive value of only 23% in a series of over 3,500 patients with blunt abdominal trauma patients reported by Soyka et al. 56 Otomo et al. 57 have attempted to refine these criteria further. They suggest that because white blood cells will be present in the peritoneal cavity in any case where significant hemorrhage occurs, the ratio of the number of WBCs to RBCs might be more valid. Their criterion for a positive DPL is 1 WBC for every 150 RBCs. Other authors have attempted to clarify the DPL criteria. A study by Henneman and colleagues 58 refined the criteria of WBCs in lavage fluid by correcting for the WBCs of peripheral blood. They reported greater accuracy in identifying those with serious injuries using this correction. Similarly, Fang and coauthors 7 found that the ratio of WBCs to RBCs in the lavage fluid versus the blood was helpful. McAnena s group 59 reported that lavage amylase and alkaline phosphatase levels were useful adjuncts to the standard lavage criteria. These findings were supported by Jaffin et al., 60 who felt that lavage alkaline phosphatase levels were helpful in equivocal cases. In a series of 292 patients, Megison and Weigelt 61 noted no benefit from measurement of lavage alkaline phosphatase. In summary, a CT scan that shows only free fluid without solid organ injury in the hemodynamically stable blunt trauma patient presents a dilemma. On the basis of our study, we do not recommend that such a patient be rushed to immediate celiotomy. What the next step should be is controversial. A suggested algorithm is depicted in Figure 1. Patients who are alert may be followed with serial physical examinations. A positive physical examination would be one in which the presence of peritoneal irritation was detected. For those patients whose physical examinations are unreliable, we suggest that DPL is a reasonable method of management. Each institution would need to establish criteria for a lavage to be considered positive. REFERENCES 1. Brownstein MR, Bunting T, Meyer AA, Fakhry SM. Diagnosis and management of blunt small bowel injury: a survey of the membership of the American Association for the Surgery of Trauma. J Trauma. 2000;48: Hackam DJ, Ali J, Jastaniah SS. Effects of other intra-abdominal injuries on the diagnosis, management, and outcome of small bowel trauma. J Trauma. 2000;49: Fakhry SM, Brownstein M, Watts DD, Baker CC, Oller D. Relatively short diagnostic delays ( 8 hours) produce morbidity and mortality in blunt small bowel injury: an analysis of time to operative intervention in 198 patients from a multicenter experience. J Trauma. 2000;48: Pikoulis E, Delis S, Psalidas N, et al. Presentation of blunt small intestinal and mesenteric injuries. 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6 12. Jerby BL, Attorri RJ, Morton D Jr. Blunt intestinal injury in children: the role of the physical examination. J Pediatr Surg. 1997; 32: Kurkchubasche AG, Fendya DG, Tracy TF Jr, Silen ML, Weber TR. Blunt intestinal injury in children: diagnostic and therapeutic considerations. Arch Surg. 1997;132: Dowe MF, Shanmuganathan K, Mirvis SE, Steiner RC, Cooper C. CT findings of mesenteric injury after blunt trauma: implications for surgical intervention. AJR Am J Roentgenol. 1997;168: Albanese CT, Meza MP, Gardner MJ, et al. Is computed tomography a useful adjunct to the clinical examination for the diagnosis of pediatric gastrointestinal perforation from blunt abdominal trauma in children? J Trauma. 1996;40: Moss RL, Musemeche CA. Clinical judgment is superior to diagnostic tests in the management of pediatric small bowel injury. J Pediatr Surg. 1996;31: Bloom AI, Rivkind A, Zamir G, et al. Blunt injury of the small intestine and mesentery: the trauma surgeon s Achilles heel? 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7 Isolated Free Fluid on CT Scan in Blunt Abdominal Trauma 55. Sozuer EM, Akyurek N, Kafali ME, Yildirim C. Diagnostic peritoneal lavage in blunt abdominal trauma. Eur J Emerg Med. 1998;5: Soyka JM, Martin M, Sloan EP, Himmelman RG, Batesky D, Barrett JA. Diagnostic peritoneal lavage: is an isolated WBC count greater than or equal to 500/mm3 predictive of intra-abdominal injury requiring celiotomy in blunt trauma patients? J Trauma. 1990;30: Otomo Y, Henmi H, Mashiko K, et al. New diagnostic peritoneal lavage criteria for diagnosis of intestinal injury. J Trauma. 1998; 44: Henneman PL, Marx JA, Moore EE, Cantrill SV, Ammons LA. Diagnostic peritoneal lavage: accuracy in predicting necessary laparotomy following blunt and penetrating trauma. J Trauma. 1990;30: McAnena OJ, Marx JA, Moore EE. Peritoneal lavage enzyme determinations following blunt and penetrating abdominal trauma. J Trauma. 1991;31: Jaffin JH, Ochsner MG, Cole FJ, Rozycki GS, Kass M, Champion HR. Alkaline phosphatase levels in diagnostic peritoneal lavage fluid as a predictor of hollow visceral injury. J Trauma. 1993;34: Megison SM, Weigelt JA. The value of alkaline phosphatase in peritoneal lavage. Ann Emerg Med. 1990;19: EDITORIAL COMMENT Blunt intestinal and mesenteric injuries continue to present diagnostic problems in the management of blunt abdominal trauma. Delayed diagnosis and operative treatment, with its attendant morbidity and mortality, has been a function of both imperfect diagnostic methods and errors in interpreting the significance of selected findings. The determination of the optimal management of blunt trauma patients with the sole finding of unexplained free intraperitoneal fluid seen on computed tomography would be an important step as an evidence-based practice guideline. Unfortunately, the data available in the literature, of which a limited subset is used in this report, consist entirely of a series of retrospective, non case-controlled observations. In a strict evidence-based context, the best that can be derived from this material is level 4 data and corresponding grade C (or D) recommendations. In addition, the methods for conducting the systematic review that the conclusions of this report are based on fall well short of more rigorous evidence-based search and review methods such as those used by the Cochrane Collaboration. 1 In the absence of controlled, prospective data or rigorous systematic review, the authors are left to draw conclusions based on that well recognized, time honored, level 5 data element: expert opinion. Having performed this review, it may well be that the author s opinions are better or more learned than those conflicting ones contained in the articles they cite (Table 3 in the article). It could be argued, however, that the most important statistic derived from this report is the 27% incidence of therapeutic celiotomy in patients with isolated free fluid on CT scan, and that the readership of The Journal of Trauma would prefer to draw their own conclusions from this information. Other opinions and otherwise unsubstantiated statements contained in this report are cause for more concern. The authors recommend that alert patients be followed with serial physical examinations, noting that the physical examination is regarded as the best method of detecting serious intraabdominal injury, despite the fact that at least three of the cited studies (references 6, 14, and 49 in the article) as well as many others in the literature suggest just the opposite. 2 6 Blunted or diminished response to the physical examination may be produced by alcohol, medications or drugs, other injuries, or even related therapeutic and diagnostic interventions, and diagnostic delay resulting from relying solely on the physical examination, as suggested, may be catastrophic even in the alert patient. Another statement, presumably an opinion also, suggesting that the likelihood of blunt intestinal injury is related to the amount of free fluid, while possibly true, is difficult to substantiate with data, insofar as this relationship was not quantified in more than one or two of the cited studies. The algorithm included as part of this review, in addition to being somewhat simplistic and imprecisely worded, has little basis in tabulated data and no basis in associated outcome data whatsoever. While I do not necessarily disagree with the philosophy and expert opinions underlying this algorithm, it should by no means be regarded as a legitimate evidence-based guideline that can be justified based on the data presented. Determining the optimal management for the problem of isolated free abdominal fluid in blunt trauma cannot be derived from existing data. Reports such as this, even if based primarily on expert opinion and a loose collection of retrospective data, will perhaps form the basis for carefully controlled, criteria-driven, algorithm-based prospective studies, which will eventually lead to a valid evidence-based practice guideline. Robert C. Mackersie, MD Professor of Surgery University of California, San Francisco Director of Trauma Services San Francisco General Hospital San Francisco, California REFERENCES 1. Cochrane Collaboration Ferrera PC, Verdile VP, Bartfield JM, Snyder HS, et al. Injuries distracting from intraabdominal injuries after blunt trauma. Am J Emerg Med. 1998;16: Davis JJ, Cohn I Jr, Nance FC. Diagnosis and management of blunt abdominal trauma. Ann Surg. 1976;183: McAnena OJ, Moore EE, Marx JA. Initial evaluation of the patient with blunt abdominal trauma. Surg Clin North Am. 1990;70: Rodriguez A, DuPriest RW Jr, Shatney CH. Recognition of intraabdominal injury in blunt trauma victims. A prospective study comparing physical examination with peritoneal lavage. Am Surg. 1982;48: Mackersie RC, Tiwary AD, Shackford SR, Hoyt DB. Intraabdominal injury following blunt trauma: identifying the high-risk patient using objective risk factors. Arch Surg. 1989;124: Volume 53 Number 1 85