Objective: To evaluate the relationships between the location and extent of diffusion of free intraperitoneal air by multi-slice spiral CT (MSCT) and between the location and size of acute gastrointestinal perforation. Methods: This was a descriptive case series. We examined abdominal CT images of 33 patients who were treated for intraoperatively confirmed gastrointestinal perforation (excluding appendiceal perforation) in the Department of General Surgery, Nanfang Hospital between January and September 2022. We identified five locations of intraperitoneal air: the subphrenic space, hepatic portal space, mid-abdominal wall, mesenteric space, and pelvic cavity. We allocated the 33 patients to an upper gastrointestinal perforation (n=23) and lower gastrointestinal perforation group (n=10) base on intraoperative findings and analyzed the relationships between the locations of free gas and of gastrointestinal perforation. Additionally, we established two models for analyzing the extent of diffusion of free gas in the abdominal cavity and constructed receiver operating characteristic (ROC) curves to analyze the relationships between the two models and the size of the gastrointestinal perforation. Results: In the upper gastrointestinal perforation group, free gas was located around the hepatic portal area in 91.3% (21/23) of patients: this is a significantly greater proportion than that found in the lower gastrointestinal perforation group (5/10) (P=0.016). In contrast, free gas was located in the mesenteric interspace in 8/10 patients in the lower gastrointestinal perforation group; this is a significantly greater proportion than was found in the upper gastrointestinal perforation group (8.7%, 2/23) (P<0.010). The sensitivity of diagnosis of upper gastrointestinal perforation base on the presence of hepatic portal free gas was 84.8% and the specificity 71.4%. Further, the sensitivity of diagnosis of lower gastrointestinal perforation base on the presence of mesenteric interspace free gas was 80.0% and the specificity 91.3%. The rates of presence of free gas in the subdiaphragmatic area, mid-abdominal wall, and pelvic cavity did not differ significantly between the two groups (all P>0.05). Receiver operating characteristic curves showed that when free gas was present in four or more of the studied locations in the abdominal cavity, the optimal cutoff for perforation diameter was 2 cm, the corresponding sensitivity 66.7%, and the specificity 100%, suggesting that abdominal free gas diffuses extensively when the diameter of the perforation is >2 cm. Another model revealed that when free gas is present in three or more of the studied locations, the optimal cutoff for perforation diameter is 1 cm, corresponding to a sensitivity of 91.7% and specificity of 76.2%; suggesting that free gas is relatively confined in the abdominal cavity when the diameter of the perforation is <1 cm. Conclusion: Identifying which of five locations in the abdominal cavity contains free intraperitoneal air by examining MSCT images can be used to assist in the diagnosis of the location and size of acute gastrointestinal perforations.
目的： 探讨多层螺旋CT显示腹腔游离气体位置及弥散程度与急性消化道穿孔部位及大小的关系。 方法： 本研究采用描述性病例系列研究方法。分析南方医院普通外科2022年1—9月期间，33例经手术证实的消化道穿孔患者（阑尾穿孔除外）的腹部CT图像，将腹腔游离气体位置分为5个部位，即膈下、肝门、中腹壁、肠系膜间和盆腔。按手术探查结果，将33例患者分为上消化道穿孔组（23例）和下消化道穿孔组（10例），分析不同位置的腹腔游离气体与消化道穿孔部位的关系。另外，通过观察腹腔内游离气体的弥散程度，建立两个分析模型，利用受试者工作特征（ROC）曲线分析两种模型与消化道穿孔大小的关系。 结果： 上消化道穿孔组中，有91.3%（21/23）可观察到肝门部游离气体，高于下消化道穿孔组（5/10），差异有统计学意义（P=0.016）；而下消化道穿孔组中，有8/10可观察到肠系膜间游离气体，高于上消化道穿孔组（8.7%，2/23），差异有统计学意义（P<0.010）。肝门部游离气体诊断上消化道穿孔的灵敏度为84.8%，特异度为71.4%；肠系膜间游离气体诊断下消化道穿孔的灵敏度为80.0%，特异度为91.3%。两组观察到膈下、中腹壁和盆腔游离气体的差异无统计学意义（均P>0.05）。ROC曲线显示，当腹腔内出现4个或以上部位游离气体时，穿孔直径最佳截断值为2 cm，对应灵敏度为66.7%，特异度为100%；提示穿孔直径>2 cm时，腹腔游离气体高度弥散。当腹腔内出现3个或以上部位游离气体时，穿孔直径最佳截断值为1 cm，对应灵敏度为91.7%，特异度为76.2%；提示穿孔直径<1 cm时，腹腔游离气体相对局限。 结论： 腹腔游离气体五分法可帮助诊断急性消化道穿孔的定位和大小。.