Emergency. 2017; 5 (1): e34 OR I G I N A L RE S E A RC H Diagnostic Accuracy of Abdominal wall Ultrasonography and Local Wound Exploration in Predicting the Need for Laparotomy following Stab Wound Ali Vafaei1, Kamran Heidari1, Afshin Saboorizadeh1, Amin shams akhtari1∗ 1. Department of Emergency Medicine, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Received: December 2016; Accepted: December 2016; Published online: 11 January 2017 Abstract: Introduction: Screening of patients with anterior abdominal penetrating trauma in need for laparotomy is an important issue in management of these cases. This study aimed to compare the accuracy of abdominal wall ultrasonography (AWU) and local wound exploration (LWE) in this regard. Methods: This diagnostic accuracy study was conducted on âL’ě 18 year-old patients presenting to emergency department with anterior abdominal stab wound and stable hemodynamics, to compare the characteristics of AWU and LWE in screening of patients in need of laparotomy. Results: 50 cases with the mean age of 28.44 ± 7.14 years were included (80% male). Sensitivity, specificity and area under the receiver operating characteristic (ROC) curve of AWU were 70.58 (95% CI: 44.04 – 88.62), 93.33 (95% CI: 76.49 – 98.83), and 81.96 (95% CI: 69.91 – 94.01), respectively. These measures were 88.23 (62.25 – 97.93), 93.33 (76.49 – 98.83), and 90.78 (95% CI: 81.67 – 99.89) for LWE, respectively. The difference in overall accuracy of the two methods was not statistically significant (p = 0.0641). Conclusion: Based on the findings of the present study, AWU and LWE had the same specificity but different sensitivities in screening of anterior abdominal stab wound patients in need of laparotomy. The overall accuracy of LWE was slightly higher (91.48% versus 85.1%). Keywords: Abdominal injuries; wounds, penetrating; wounds, stab; ultrasonography; diagnostic techniques and proce- dures © Copyright (2017) Shahid Beheshti University of Medical Sciences Cite this article as: Vafaei A, Heidari K, Saboorizadeh A, Shams akhtari A. Diagnostic Accuracy of Abdominal wall Ultrasonography and Local Wound Exploration in Predicting the Need for Laparotomy following Stab Wound. Emergency. 2017; 5(1): e34. 1. Introduction P enetrating abdominal trauma is known as one of the relatively frequent causes of emergency department visits. There is a general agreement that patients with penetrating abdominal trauma and hemodynamic instabil- ity must immediately be referred to operation room without additional diagnostic measures (1). However, management of hemodynamically stable patients is a controversial issue. At least 25% of anterior abdominal stab wounds are super- ficial and do not need laparotomy (2). Unnecessary laparo- tomy can increase the risk of morbidity and mortality of these patients (3). Sanei et al. showed that 82% of stab wound la- parotomies, which were done only based on anterior fascial ∗Corresponding Author: Amin Shams Akhtari; Emergency Department, Loghman Hakim Hospital, Kamali Street, Karegar Avenue, Tehran, Iran. Tel: +989123788731 / Fax: +982155415539 / E-mail: amin.may1981@gmail.com impairment, are negative (4). In recent years, most physi- cians have tried to change their diagnostic approaches from mandatory exploration to selective diagnostic approaches (5-7). Appropriate approach to these patients needs balance between invasiveness and accuracy of diagnostic measures in this regard. Using ultrasonography, deep peritoneal lavage (DPL), serial clinical examination, local wound exploration (LWE), and abdominal computed tomography (CT) scan are suggested by different studies to decrease the rate of unnec- essary laparotomies. LWE is a valid, yet invasive, screening tool for selection of stab wound patients in need of laparo- tomy (2). However, abdominal wall ultrasonography (AWU) seems to be as a non-invasive, available, bedside, and safe alternative for LWE in this regard (1, 3). Based on the above- mentioned point, this study aimed to assess the diagnostic accuracy of AWU and LWE in detection of patients in need of laparotomy following anterior abdominal stab wound. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com A. Vafaei et al. 2 2. Methods 2.1. Study design and setting This cross sectional study was conducted on patients pre- senting to emergency departments of Loghman Hakim, Imam Hossein, and Hafte-tir Hospitals, Tehran, Iran, follow- ing anterior abdominal stab wound, during March 2013 to March 2015, to compare the diagnostic accuracy of AWU and LWE in prediction of need for laparotomy. The study protocol was approved by ethics committee of Shahid Beheshti Uni- versity of Medical Sciences and informed consent form was signed by all participants. Authors adhered to all Helsinki recommendations and confidentiality of patients’ informa- tion during the study period. 2.2. Participants Patients older than 18 years old with anterior abdominal stab wound were included. Hemodynamic instability, presenting peritoneal signs, protrusion of abdominal organs, gastroin- testinal bleeding, pregnancy, instrument in situ, presence of abdominal free fluid on focused abdominal ultrasonography for trauma patients (FAST), peritoneal evisceration, multi- ple wounds, and need for emergent laparotomy were among the exclusion criteria. Anterior abdominal wall was defined as the area superior to the inguinal ligaments, medial to the anterior axillary line, and two fingerbreadths inferior to the costal margins. 2.3. Data gathering A predesign check list, consisting of demographic informa- tion (age, sex), trauma mechanism, vital signs (blood pres- sure, heart rate, respiratory rate, and oxygen saturation), findings of AWU and LWE regarding need for laparotomy, as well as final outcome (decision of in charge surgeons regard- ing performing laparotomy), was used for data gathering. Without interfering in the routine approach, eligible patients underwent AWU by a trained senior emergency medicine resident (under supervision of an emergency medicine spe- cialist) at the time of admission to emergency department. The emergency medicine resident was trained and certi- fied by an expert radiologist, performing tract ultrasonogra- phy on ten sheep cadaver models under his direct supervi- sion. After doing AWU, all patients underwent LWE by se- nior surgery residents and were followed until discharge from hospital. Patients that underwent laparotomy based on fi- nal decision of in charge surgeon, considering all clinical and imaging findings (serial clinical examination, abdominal CT scan, serial FAST, and etc.) during the period of hospi- tal admission were considered as reference group. Samsung HM70A ultrasonography machine with 8 MHZ linear probe was used for ultrasonography of the abdominal wall and its 10 × 10 cm surrounding area (figure 1). Figure 1: Abdominal wall ultrasonography view. 2.4. Statistical Analysis Considering 25% prevalence of penetrating abdominal trauma in need for laparotomy (2), d = 0.05, and 95% confi- dence interval (CI), the minimum required sample size was calculated to be 35 cases. Data were analyzed using SPSS version 21 and STATA 11. Qualitative and quantitative vari- ables were presented with frequency and percentage, and mean ± standard deviation, respectively. For evaluating the screening performance characteristics of AWU and LWE in prediction of need for laparotomy sensitivity, specificity, pos- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 3 Emergency. 2017; 5 (1): e34 Table 1: Baseline characteristics of studied patients (n = 50) Variable Number (%) Age (year) 18 -24.9 12 (24) 25- 34.9 23 (46) ≥ 35 15 (30) Sex Male 40 (80) Female 10 (20) Marital status Married 18 (38.3) Single 29 (61.7) Trauma mechanism Knife 41 (82) Other 9 (18) Employment Employed 36 (72) Non-employed 14 (28) Vital Sign Systolic blood pressure (mmHg) 117.10 ± 10.79 Diastolic blood pressure (mmHg) 71.30 ± 9.36 Heart rate (/minute) 87.62 ± 6.97 Respiratory rate (/minute) 19.20 ± 1.84 Oxygen saturation (%) 96.52 ± 1.50 Data are presented as mean ± standard deviation or frequency and percentage. Figure 2: Area under the receiver operating characteristic (ROC) curve of abdominal wall ultrasonography and local wound explo- ration in prediction of need for laparotomy following anterior ab- dominal stab wound (p = 0.0641). itive predictive value (PPV ), negative predictive value (NPV ), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) with 95% CI were calculated. The area under the re- ceiver operating characteristic (ROC) curve of the two tests was compared. Need for laparotomy based on final decision of in charge surgeon was considered as the reference test. P- values less than 0.05 were assumed significant results. 3. Results 3.1. Baseline characteristics 50 cases with the mean age of 28.44 ± 7.14 years (18 – 47) were included (80% male). Table 1 shows the baseline character- istics of studied patients. 46% of cases were in 25 – 35 years age group, 61.7% single, 72% employee, and 82% with knife. 3 (6%) cases were discharged against medical advice and were omitted from final analysis. 3.2. Screening characteristics Based on AWU and LWE 14 (28%) and 17 (34%) cases were detected as peritoneal penetration and needed laparotomy. According to the final decision of surgery service based on all clinical and imaging findings, 17 (34%) cases underwent la- parotomy during the hospitalization period. Table 2 and fig- ure 2 summarize the screening performance characteristics of AWU and LWE in prediction of need for laparotomy follow- ing anterior abdominal stab wound. The area under the ROC curve of AWU and LWE were 81.96 (95% CI: 69.91 – 94.01) and 90.78 (95% CI: 81.67 – 99.89), respectively (p = 0.0641). 4. Discussion Based on the findings of the present study, AWU and LWE have the same specificity (93.3%) but different sensitivities (70.58% versus 88.23%) in screening of anterior abdominal stab wound patients in need of laparotomy. The overall ac- curacy of LWE in this regard is slightly higher (91.48% ver- sus 85.1%) without statistical significance. Rapid assessment and decision making plays a main role in improving the out- come of severely injured trauma patients (8-11). Although using LWE could be helpful in eliminating hospitalization of more than 30% of patients with anterior abdominal stab wound (2), it is invasive, uncomfortable for the patient, and difficult in obese and uncooperative patients as well as those with thick abdominal musculature. Finding noninvasive al- ternatives for LWE is an interesting area in management of these patients in emergency and surgery departments. Ultra- sonography is known as an available diagnostic measure for focused assessment of blunt and penetrating trauma patients in emergency department (12-17). Omari et al. showed that ultrasonography is a good guide for selecting patients in need for laparotomy following penetrating abdominal trauma (1). Murphy et al. reported that tract ultrasonography in patients with anterior abdominal penetrating trauma had 59% sen- sitivity and 100% specificity (18). Soffer et al. reported that sonography had 48% sensitivity and 98% specificity in di- agnosis of intra-abdominal lesions and Fray et al. reported 100% positive and negative predictive value of ultrasonogra- phy in this regard (19, 20). Ku et al. presented a 76 year-old stab wound case with negative abdominal CT scan findings, This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com A. Vafaei et al. 4 Table 2: Screening performance characteristics of abdominal wall ultrasonography (AWU) and local wound exploration (LWE) in prediction of need for laparotomy following anterior abdominal stab wound (n = 47) Characteristics AWU LWE True positive 12 (25.5) 15 (31.9) True negative 28 (59.6) 28 (59.6) False positive 2 (4.2) 2 (4.2) False negative 5 (10.6) 2 (4.2) Sensitivity 70.58 (44.04 – 88.62) 88.23 (62.25 – 97.93) Specificity 93.33 (76.49 – 98.83) 93.33 (76.49 – 98.83) Positive predictive value 85.71 (56.15 – 97.48) 88.23 (62.25 – 97.93) Negative predictive value 84.84 (67.33 – 94.28) 93.33 (76.49 – 98.83) Positive likelihood ratio 6.00 (1.63 – 22.03) 7.50 (2.01 – 27.88) Negative likelihood ratio 0.17 (0.07 –0.40) 0.07 (0.01 – 0.27) Data are presented with 95% confidence interval. which underwent laparoscopy based on positive tract ultra- sonography finding regarding peritoneal impairment (21). In our study, need for laparotomy was confirmed in 85.7% of pa- tients with positive AWU and 88.2 % of positive LWE results. There were 5 (10.6%) cases with false negative ultrasonogra- phy reports and 2 (4.2%) cases with false negative exploration reports. Although the difference in total accuracy of the two models is not statistically significant, accuracy of exploration is in excellent range and ultrasonography in good range. As we know, ultrasonography is very operator dependent and this slight inferiority of ultrasonography could be eliminated by more practice. It seems that tract ultrasonography as a bedside, noninvasive, non-expensive, available, and safe di- agnostic approach could be considered for screening of pen- etrating abdominal trauma patients in need of laparotomy. 5. Limitation Among the limitations of the present study is not evaluat- ing the cases with multiple penetrating traumas and those with trauma of other parts of the abdominal area. In addi- tion, in most cases trauma was caused by knife, which affects the diversity of trauma type and might limit the generaliz- ability of the results for cases such as wounds caused by bul- lets. Patient selection for laparotomy was done by surgeons who were aware of the results of LWE, which might have led to some type of selection bias. 6. Conclusion Based on the findings of the present study, AWU and LWE have the same specificity (93.3%) but different sensitivities (70.58% versus 88.23%) in screening of anterior abdominal stab wound patients in need of laparotomy. The overall accu- racy of LWE is slightly higher (91.48% versus 85.1%) without statistical significance. 7. Appendix 7.1. Acknowledgements The authors would like to thank all the staff of Loghman Hakim, hafte tir, and Imam Hossein Hospitals and Clinical Research Development Center of Loghman Hakim Hospital, for their cooperation. 7.2. 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