兽研简要总结
金属弹丸伤是伴侣动物创伤性伤害的重要表现形式，常具有重大的法医学意义。在疑似非意外伤害（NAI）案件中，当武器、射击情况以及主要弹道弹丸无法获得时，建立科学上可辩护的死因需要系统性的尸检方法。本文报告了韩国一例雄性珍岛犬因致命性穿透性胸部弹丸创伤而进行的法医尸检调查。通过结合数字X线摄影、高分辨率尸检计算机断层扫描（PMCT）、细致的法医尸体剖检和组织病理学分析，我们成功定位了滞留的金属碎片，记录了严重的肺经膜撕裂和左侧第四肋骨骨折，并重建了可能的右至左经胸弹道轨迹。这一简化的多模式工作流程突显了将解剖前虚拟尸检与经典法医病理学相结合如何增强证据采集、确认生前生命反应，并支持对疑似虐待动物案件的法律调查。
1. 引言
金属弹丸伤是伴侣动物创伤性损伤的重要原因，可能具有重大的法医学意义[1,2,3,4,5,6]。近年来，兽医法医学文献越来越关注非意外伤害（NAI）的识别和特征描述，其中弹丸相关创伤代表了一种特别严重和恶意的形式[1,3,4]。在国际兽医调查中，犬和猫的枪弹伤和气枪伤经常遇到，胸部和四肢创伤占主导地位，因为其表面积大且在直接遭遇时易受伤害[5,6,7]。在严格管制枪支和气枪的司法管辖区，如韩国，平民枪支拥有受到严格限制，使得国内弹丸伤相对罕见，但一旦发生则具有法律关键性。在此类法律框架下，法医尸检调查对于确定射击是否涉及授权狩猎武器、非法枪支或改装气枪，以及区分故意虐待动物与意外走火至关重要[1,3,4]。
胸部穿透性创伤尤为重要，因为即使相对局限的伤口也可导致肺经膜撕裂、血胸、气胸、呼吸功能受损和快速死亡[5,6]。然而，弹丸相关损伤的法医解释并不总是 straightforward[3,4,8]。当现场未被完整记录、主要弹丸质量未被回收或正式弹道检查不可用时，武器类型、弹丸成分、速度、射击距离和确切轨迹可能难以确定[7,8,9]。
与人类法医学相比，兽医法医病理学面临独特挑战。在人类法医调查中，专门的犯罪现场小组常规保存物证、进行全面弹道回收并记录现场的枪击残留物。相比之下，兽医从业者和法医病理学家很少被召集到犯罪现场；相反，死亡动物受害者通常在没有现场重建或弹道背景的情况下被提交[1,2,3,4]。此外，伴侣动物具有浓密的毛发覆盖，掩盖外部入口和出口缺损，高软组织弹性以及品种间极大的解剖多样性，这些可显著复杂化轨迹重建和伤口评估[3,4]。虽然人类法医设施常规依赖专门的尸检虚拟尸检方案，但在许多机构中，兽医病理学对先进横断面成像的获取仍然有限，这强调了建立标准化、可重复的多模式工作流程的必要性[2,9,10,11,12,13,14,15]。
多模式尸检方法可改善此类病例的解释[2,7,9,11,13,14]。常规数字X线摄影有助于快速检测不透射线异物以及骨骼和胸部异常的广泛特征描述[9,11,12]。尸检计算机断层扫描（PMCT）提供金属碎片的详细三维定位，并允许在侵入性解剖前全面评估骨折、胸腔内气体、液体积聚、肺塌陷和皮下气肿[7,9,11,14]。剖检前成像至关重要，因为解剖可能无意中移位小碎片或破坏骨骼骨折与软组织轨迹之间的细微解剖关系[2,7,9]。尽管兽医文献中报道了血管内弹丸迁移等罕见现象[15,16,17,18]，但绝大多数弹道病例涉及直接机械穿透和局部组织破坏。
本报告描述了来自韩国的一例成年雄性珍岛犬致命性胸部穿透性金属弹丸伤病例。目的是整合数字X线摄影、PMCT、法医尸体剖检和组织病理学分析，以表征创伤、评估可能的轨迹、阐明致命病理生理机制，并展示用于疑似非意外弹丸创伤兽医法医学调查的实用工作流程。
2. 材料与方法
2.1. 病例背景
一头体重9.8 kg的成年雄性珍岛犬（根据完整成年齿列及闭合的骨骺估计年龄为3–4岁），由当地警方依据官方动物虐待调查规程提交至动植物检疫局（APQA）动物疾病诊断部，进行法医尸检调查。尸体在户外环境中被发现时已死亡，并立即由执法部门封存。尸体于发现后约4小时内冷藏保存于4 °C，并于死后24小时内提交检查。外部物理检查显示为新鲜死后状态，尸僵已建立，未见腐败、自溶或腐败气体形成的迹象，确保了死后虚拟解剖和尸检的最佳诊断完整性。现有调查记录表明存在胸部投射物损伤及可能残留金属碎片的疑虑。最初未获得现场重建、确认的枪支身份、口径或弹道报告。
2.2. 死后影像学检查
在解剖前，使用平板数字X射线摄影系统（EpiX，POSKOM Co., Ltd.，韩国高阳市）获取正交胸部及全身X线片（侧位和腹背位投照），曝光参数：70 kVp，10 mAs，焦片距100 cm。使用DICOM查看工作站审阅图像，评估不透X线异物、骨骼创伤、胸腔积液及软组织气肿。
随后，使用16层多探测器CT扫描仪（Brivo CT385，GE Healthcare，中国北京）进行死后计算机断层扫描（PMCT）。以背卧位采集螺旋容积数据（120 kVp，150 mAs，层厚0.75 mm，重建增量0.5 mm，螺距0.938，机架旋转时间0.8 s）。分别处理并归档高分辨率骨算法和标准软组织重建算法的图像。使用专用DICOM软件版本14BW25.15（OsiriX MD，Pixmeo，瑞士日内瓦；骨窗：窗宽2000 HU，窗位500 HU；软组织窗：窗宽400 HU，窗位40 HU；肺窗：窗宽1500 HU，窗位−600 HU）进行多平面重建（横断面、矢状面、背侧面）和三维（3D）容积渲染。CT审阅重点为金属衰减碎片的定位，以及胸部软组织和骨骼结构的详细评估，并确定头部、脊柱和腹部是否存在创伤性病变。
2.3. 尸检与样本采集
按照既定的兽医法医证据采集规程[2,4,13]，进行了完整、系统的逐层法医尸检。在切开胸壁之前，通过在直视下进行膈下穿刺水下测试（“水试验”），评估是否存在气胸及胸腔负压丧失。对外部皮肤缺损进行拍照、测量和记录。解剖过程中仔细遵循影像学发现所提供的路线图，以暴露破坏的骨骼结构并回收残留金属碎片。按照正式的证据链文件记录，所有回收的金属碎片均原位记录，在生理盐水中轻柔冲洗（不做机械刮擦），称重，使用法医天平拍照，并移交至国家法医服务局[2,13]。
取自内部肺实质损伤边缘、皮肤入口和出口病变、皮下组织及邻近肋间肌的组织样本，用10%中性缓冲福尔马林固定，石蜡包埋，4 µm切片，苏木精-伊红（H&E）染色。组织病理学检查评估出血、纤维蛋白沉积、细胞炎症反应以及热损伤或异物颗粒的显微镜下证据。
3. 病例展示
3.1. 外部检查
外部检查显示被毛完整，右肩和左腋区有局灶性血迹。剃毛后，在右肩胛区上方发现一直径6 mm的离散圆形皮肤缺损，周围环绕 faint 环状擦伤带（图1A）。在左腋区，观察到一个不规则、略呈长形的星状皮肤缺损，大小约14 mm × 9 mm，其尾腹侧缘伴有偏心性表皮浅层擦伤区，形态学上与出口创相符，可能伴有垫衬伤（图1A）。触诊发现左侧胸壁外侧有明显捻发音，与皮下气肿一致。头部、脊柱、骨盆或四肢未见挫伤、裂伤或骨折的证据。
3.2. 放射学检查结果
正交位胸片显示多发（6–8处）离散、形态不规则、边缘锐利的金属不透X线影，最大径1.0 mm至3.5 mm，主要聚集于左侧腹侧及中段胸区，投影于左侧第4至第6肋间（图1B）。可见中至大量胸腔积液，表现为双侧肺叶扇贝样边缘、肺缘向背侧回缩，以及弥漫性软组织密度影遮盖腹侧心影及膈线。左侧侧胸壁可见明显胸壁皮下气肿。回顾性评估侧位片显示左侧第4肋中段皮质不连续及台阶样畸形，部分被前肢肌肉组织遮挡。
3.3. 死后计算机断层扫描发现
PMCT提供了胸部创伤的全面三维定位。于左侧第4肋中至背侧三分之一处发现斜行移位骨折，骨折端皮质向外（侧方）移位。成簇的高密度金属碎片（CT衰减值>3000 HU）嵌入紧邻骨折肋的断裂肋间肌及壁层胸膜内（图1C、D）。此外，记录到中量双侧胸腔积液（CT衰减值35至50 HU，符合未凝固至部分凝固血液），数枚微小金属碎片（1–2 mm）迁移至积聚胸腔积液内左侧肋膈隐窝的依赖部位。发现明显左侧气胸，伴左侧胸壁广泛胸壁皮下气肿，以及纵隔明显向对侧（右侧）移位，提示左侧张力性气胸。左肺叶显示严重被动性压迫性肺不张，右肺叶显示斑片状肺泡实变，符合肺挫伤及出血。
仔细检查前纵隔发现局灶性纵隔气肿及轻度纵隔增宽，沿连接颅侧肺叶的右背侧至左腹侧跨胸通道可见软组织密度。然而，主要纵隔血管结构——包括前腔静脉、主动脉弓、头臂干及左锁骨下动脉——保持完整，管壁连续性保留，无横断或假性动脉瘤证据。邻近器官包括食管、气管、心脏及心包未见创伤性破裂、钝性挫伤或暂时性空腔形成损伤征象。全身CT扫描确认颅骨、脑实质、颈/胸腰段椎骨及腹腔脏器完全无创伤性或病理性异常。
3.4. 剖检发现
水下潜水膈肌穿刺立即释放加压气泡，确认打开胸腔前存在气胸。进入胸腔后，从胸腔排出约100 mL暗红色、液体至部分凝固血液（血胸），以左侧明显积聚。
详细解剖肺实质显示明显的局灶性经包膜撕裂道。右前叶肺内，一穿孔性缺损进入外侧面（缺损8 mm×6 mm）并穿出内侧面（9 mm×7 mm），周围环绕暗色出血性实质袖套。左前叶肺内，相应贯穿性经包膜撕裂（入口9 mm×8 mm，出口12 mm×10 mm）横穿腹侧三分之一，边缘参差不齐、出血。创道在大血管结构腹侧的前纵隔腹侧形成直接解剖连续体，连接右侧入口部位与左侧胸壁缺损。
左侧胸壁内表面，紧邻骨折的左第4肋处可见第4肋间动脉、静脉及壁层胸膜严重撕裂，为血胸的主要来源，同时伴有撕裂的前叶肺血管出血。广泛肌内及筋膜出血累及直接位于左腋皮肤缺损下方的左腋及胸肌。仔细解剖骨折肋及病灶周围软组织，取出五枚变形金属碎片（总重1.78 g），已编目并保存用于法医弹道学。尸体内部未发现大型完整弹头核心。
详细检查右侧胸壁内表面发现右侧第3及第4肋间入口道周围局灶性撕裂及广泛肌肉出血；然而，右侧肋间神经血管束大体完整，无主要动脉横断，提示右侧胸腔积液主要来源于撕裂的右肺实质及相关毛细血管床。
3.5. 组织病理学发现
对肺经包膜撕裂边缘的组织病理学检查显示，肺泡结构广泛破坏，大量肺泡及间质红细胞外渗，致密纤维蛋白网沉积，以及邻近毛细血管和血管周围间隙内早期边集和浸润的中性粒细胞（图2B）。成纤维细胞增殖、成熟胶原沉积和含铁血黄素巨噬细胞完全缺失。这些发现证实了急性生前生活反应，表明当投射物穿过肺部时犬仍存活，存活时间估计在数分钟至不足一小时之间。
对右侧肩胛部皮肤缺损的组织学评估显示，表皮和真皮机械性穿孔、胶原束撕裂及急性真皮出血。重要的是，未见表皮凝固性坏死、上皮热变形或真皮碳/火药颗粒沉积。左侧腋窝出口缺损切片显示全层表皮撕裂和皮下出血，无热改变。这些组织学特征证实为机械性投射物创伤，无近距离或接触性热爆现象。
4. 讨论
本病例展示了整合数字X线摄影、PMCT、法医尸体剖检和组织病理学在伴侣动物致死性投射物创伤法医学评估中的互补诊断价值（表1）[1,2,3,4,7,9,11,13,14]。在兽医法医学中，投射物所致创伤常发生于非意外伤害（NAI）或疑似虐待动物的情境中，要求检查者对死亡原因提供客观、科学上可辩护的判定，并重建创伤事件[1,3,4]。当调查情况缺乏枪支回收或弹道验证时，严格的多模式死后检查方法提供了物理损伤与法律解释之间必要的证据桥梁。
PMCT虚拟解剖在本调查中作为不可或缺的解剖前工具。正如人类和兽医法医学文献先前所强调的[2,7,9,10,13,14]，仅靠常规尸体剖检存在固有风险，可能在翻动胸廓时无意改变小金属碎片位置、造成人工组织通道或掩盖细微骨折。通过在打开胸腔前进行薄层螺旋PMCT，我们绘制了金属碎片的精确解剖分布——区分嵌入左侧第四肋间肌的碎片与重力性沉积于依赖性胸膜隐窝的碎片——并记录了移位的斜行肋骨骨折。此外，PMCT实现了对整个尸体的无创检查，确认神经颅、脊柱和腹部完全完整，从而排除了并发创伤性或既存衰弱性病变[2,7,9,14]。
法医创伤学中的一个关键病理生理学问题涉及确切的死亡机制。在临床兽医急诊实践中，孤立性钝性或穿透性胸部创伤的受伤犬常表现为小至中等量血胸或气胸，通过胸腔管引流和保守治疗可获得极佳的存活率[5,6]。一只9.8 kg犬约100 mL的血胸量约占总循环血量的12%至15%（按约80–90 mL/kg计算），其本身会导致中度代偿性低血容量而非立即失血致死[5,6]。然而，在本病例中，尸体剖检和PMCT显示了并发双侧肺经包膜撕裂与左侧张力性血气胸的灾难性协同作用。胸膜腔气体（经水下膈肌穿刺阳性证实）和血液的压力性蓄积导致左肺叶严重压迫性肺不张、纵隔显著移位及严重的通气-灌注不匹配。同时，胸腔内正压升高使前后腔静脉塌陷，急剧减少心脏静脉回流，促发急性梗阻性循环休克和快速呼吸停止。这种多因素衰竭解释了急性致死性结局。
弹道路径重建是法医学分析中的另一项首要目标[3,4,8,17]。本犬体格检查与影像学发现的汇聚确立了一条高度可靠、可辩护的从右至左经胸腔轨迹：(1) 右肩胛区初始入口缺损，呈小圆形直径(6 mm)并伴有擦伤环；(2) 连续的经囊膜撕裂道穿过右前肺叶和左前肺叶，跨越前纵隔；(3) 左侧第四肋骨中段直接受击并向外移位；(4) 沿左侧胸壁局限性碎裂并滞留金属碎片；以及(5) 左侧腋窝不规则、较大(14 mm)的出口型缺损(图3)。左侧腋窝皮肤缺损显示出与出口创相符的特征，可能伴有支撑效应，可能由犬倒地呈左侧卧或弹丸穿出瞬间腋窝受地面/基质支撑所致[3,4,8]。左侧第四肋骨碎片的向外斜面及移位提供了确凿的解剖学确认，表明弹丸从胸腔内击中肋骨内皮质面，由内侧向外侧移动[3,8]。
邻近纵隔结构(食管、气管和大血管)未见暂时性空腔损伤或远隔实质挫伤，这是一项值得注意的弹道学发现。在高速度步枪伤中，膨胀性暂时空腔会产生广泛的实质撕裂、微骨折以及远离永久弹道的广泛血管破裂[3,8]。在本例中，高度局限的永久空腔及缺乏侧支空腔损伤表明，弹丸为低至中等速度弹丸(如手枪子弹或高功率气枪弹丸)，或在进入胸腔前已显著减速，其残余动能主要在撞击左侧第四肋骨时消耗[3,4,8]。此外，入口皮肤边缘的组织病理学检查显示无真皮热坏死、上皮烧灼或烟灰颗粒，明确排除了接触性或近距离枪击，提示为中远距离射击[3,8]。
家畜穿透性胸部创伤的鉴别诊断包括锐器伤(如刀、矛、箭或弩箭刺伤)和犬咬伤撕裂[3,4,9]。锐器产生干净、线性的切口边缘，缺乏环周擦伤环、弹丸碎裂或嵌入骨骼的散在金属碎片[9]。咬伤通常表现为成对的“压-撕”穿刺孔、犬齿间距模式及广泛皮下撕脱[3,4]。PMCT上存在碎裂的高衰减金属物质，并经尸检回收金属碎片证实，可牢固排除刺入伤或动物咬伤，并证实金属弹丸创伤[3,4,8]。
组织病理学评估提供了关键的确认性证据。在肺撕裂边缘内检测到纤维蛋白网、外渗红细胞和早期边集中性粒细胞，确立了无可争议的生前生活反应[1,2,4]。无纤维增生、内皮出芽或含铁血黄素沉积表明生存时间短暂——可能在伤后数分钟至不足1小时内。这一微观时间线证实，致命性衰竭直接归因于急性弹道创伤，而非继发性感染或迟发性并发症。
在伴侣动物枪伤病例系列中(如Olsen等[6]、Capak等[5]和Grela等[7]报道的病例)，胸部枪伤占就诊病例的20%至35%，由于快速发生血气胸和心肺骤停，其在各解剖区域中死亡率最高。本病例代表了一个典型但法医学上复杂的致命性穿透性胸部创伤实例，说明了在兽医学中标准化法医学虚拟解剖的必要性[2,7,11,13,14]。兽医病理学家、兽医放射学家和法医弹道学专家之间的合作对于推进动物虐待起诉和执行动物福利立法至关重要。
5. 结论
本报告记录了一例通过整合多模式方法调查的珍岛犬致命性胸部穿透性金属弹丸损伤。数字X线摄影、PMCT虚拟解剖、系统性法医尸检和组织病理学汇聚，确立了一条急性生前从右至左经胸腔轨迹，伴有肺经囊膜撕裂、左侧第四肋骨骨折、左侧胸壁金属碎裂和致命性血气胸。PMCT在标测金属碎片、评估骨骼完整性以及记录危及生命的张力性血气胸而不干扰物证方面被证明至关重要。组织病理学发现证实了急性生活反应(生存<1小时)并排除了接触距离热排放。这一综合工作流程凸显了兽医法医学虚拟解剖和病理学在支持涉嫌动物虐待和非意外创伤的法律调查中日益增长的重要性。
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Simple Summary
Metallic projectile injuries are an important manifestation of traumatic harm in companion animals, often carrying substantial medicolegal implications. In cases of suspected non-accidental injury (NAI) where the weapon, shooting circumstances, and primary ballistic projectile are unavailable, establishing a scientifically defensible cause of death requires a systematic postmortem approach. Here, we report a forensic postmortem investigation of a male Jindo dog with fatal perforating thoracic projectile trauma in the Republic of Korea. By combining digital radiography, high-resolution postmortem computed tomography (PMCT), meticulous forensic necropsy, and histopathological analysis, we successfully localized retained metallic fragments, documented severe pulmonary transcapsular lacerations and left fourth rib fracture, and reconstructed a probable right-to-left trans-thoracic trajectory. This streamlined multimodal workflow highlights how the integration of pre-dissection virtopsy with classical forensic pathology enhances evidence recovery, confirms antemortem vital reaction, and supports legal investigations of suspected animal cruelty.
1. Introduction
Metallic projectile injuries are an important cause of traumatic injury in companion animals and may have substantial medicolegal significance [1,2,3,4,5,6]. In recent years, veterinary forensic literature has increasingly focused on the identification and characterization of non-accidental injury (NAI), of which projectile-associated trauma represents a particularly severe and malicious form [1,3,4]. Across international veterinary surveys, gunshot and airgun injuries in dogs and cats are frequently encountered, with thoracic and extremity wounds predominating due to their large surface area and vulnerability during direct encounters [5,6,7]. In jurisdictions with strict firearm and airgun regulations, such as South Korea, civilian firearm ownership is heavily restricted, making domestic projectile injuries relatively uncommon yet legally critical when they occur. Under such legal frameworks, forensic postmortem investigations are essential to determine whether the shooting involved an authorized hunting weapon, an illegal firearm, or a modified airgun, and to distinguish deliberate animal abuse from accidental discharge [1,3,4].
Thoracic penetrating trauma is particularly important since even a relatively focal wound can result in pulmonary transcapsular laceration, hemothorax, pneumothorax, respiratory compromise, and rapid death [5,6]. However, the forensic interpretation of projectile-associated injuries is not always straightforward [3,4,8]. Weapon type, projectile composition, velocity, shooting distance, and exact trajectory may be difficult to establish when the scene has not been fully documented, the main projectile mass is not recovered, or formal ballistic examination is unavailable [7,8,9].
Veterinary forensic pathology presents unique challenges when compared to human forensic medicine. In human forensic investigations, specialized crime-scene units routinely preserve physical evidence, conduct comprehensive ballistics recovery, and document gunshot residues at the scene. In contrast, veterinary practitioners and forensic pathologists are rarely called to crime scenes; instead, deceased animal victims are typically submitted without scene reconstruction or ballistic context [1,2,3,4]. Furthermore, companion animals exhibit dense hair coats that obscure external entrance and exit defects, high soft-tissue elasticity, and extreme anatomical diversity among breeds, which can substantially complicate trajectory reconstruction and wound assessment [3,4]. While human forensic facilities rely routinely on dedicated postmortem virtopsy protocols, access to advanced cross-sectional imaging in veterinary pathology remains limited in many institutions, underscoring the necessity of establishing standardized, reproducible multimodal workflows [2,9,10,11,12,13,14,15].
A multimodal postmortem approach may improve interpretation in such cases [2,7,9,11,13,14]. Conventional digital radiography is useful for rapid detection of radiopaque foreign material and broad characterization of skeletal and thoracic abnormalities [9,11,12]. Postmortem computed tomography (PMCT) provides detailed three-dimensional localization of metallic fragments and permits comprehensive assessment of fractures, intrathoracic gas, fluid accumulation, pulmonary collapse, and subcutaneous emphysema prior to invasive dissection [7,9,11,14]. Pre-necropsy imaging is essential because dissection may inadvertently displace small fragments or disrupt subtle anatomical relationships between skeletal fractures and soft tissue tracts [2,7,9]. Although rare phenomena such as intravascular projectile migration have been reported in the veterinary literature [15,16,17,18], the vast majority of ballistic cases involve direct mechanical penetration and local tissue disruption.
This report describes a fatal case of thoracic perforating metallic projectile injury in an adult male Jindo dog from South Korea. The objective was to integrate digital radiography, PMCT, forensic necropsy, and histopathological analysis to characterize the trauma, evaluate the probable trajectory, elucidate the fatal pathophysiological mechanism, and demonstrate a practical workflow for veterinary medicolegal investigation of suspected non-accidental projectile trauma.
2. Materials and Methods
2.1. Case Background
A 9.8 kg, intact adult male Jindo dog (estimated age 3–4 years based on complete adult dentition and closed physes) was submitted by local police authorities to the Animal Disease Diagnostic Division of the Animal and Plant Quarantine Agency (APQA) for a forensic postmortem investigation under an official animal cruelty investigation protocol. The carcass was discovered deceased in an outdoor setting and immediately secured by law enforcement. The body was stored refrigerated at 4 °C within approximately 4 h of discovery and submitted for examination within 24 h postmortem. External physical inspection revealed a fresh postmortem condition with established rigor mortis and absent signs of decomposition, autolysis, or putrefactive gas formation, ensuring optimal diagnostic integrity for postmortem virtopsy and necropsy. Available investigative records indicated concern for thoracic projectile injury and possible retained metallic fragments. No scene reconstruction, confirmed firearm identity, caliber, or ballistic reports were initially available.
2.2. Postmortem Imaging
Orthogonal thoracic and whole-body radiographs (lateral and ventrodorsal projections) were obtained prior to dissection using a flat-panel digital radiography system (EpiX, POSKOM Co., Ltd., Goyang-si, Republic of Korea) exposure factors: 70 kVp, 10 mAs, focal-film distance 100 cm). Images were reviewed using a DICOM viewing workstation for radiopaque foreign material, skeletal trauma, pleural effusion, and soft tissue emphysema.
Subsequently, postmortem computed tomography (PMCT) was performed with a 16-slice multi-detector CT scanner (Brivo CT385, GE Healthcare, Beijing, China). Helical volumetric data were acquired in dorsal recumbency (120 kVp, 150 mAs, slice thickness 0.75 mm, reconstruction increment 0.5 mm, pitch 0.938, gantry rotation time 0.8 s). Both high-resolution bone kernel and standard soft-tissue reconstruction algorithms were processed and archived. Multiplanar reconstructions (transverse, sagittal, dorsal) and three-dimensional (3D) volume rendering were performed using dedicated DICOM software version 14BW25.15. (OsiriX MD, Pixmeo, Geneva, Switzerland; window width 2000 HU, window level 500 HU for bone; WW 400 HU, WL 40 HU for soft tissue; WW 1500 HU, WL −600 HU for lung). CT review focused on metal attenuating fragment localization as well as detailed evaluation of thoracic soft tissue and osseous structures and the presence or absence of traumatic lesions in the head, spine, and abdomen.
2.3. Necropsy and Sample Collection
A complete, systematic layer-by-layer forensic necropsy was conducted following established veterinary forensic evidence collection protocols [2,4,13]. Prior to incising the thoracic wall, the presence of pneumothorax and loss of thoracic negative pressure were evaluated by performing a submerged diaphragmatic puncture test (‘water-test’) under direct visualization. External cutaneous defects were photographed, measured, and documented. Dissection carefully followed the roadmap provided by the observed imaging findings to expose disrupted skeletal structures and recover retained metallic fragments. Following the formal chain-of-custody documentation, all recovered metallic fragments were documented in situ, rinsed gently in saline without mechanical scraping, weighed, photographed with a forensic scale, and transferred to the National Forensic Service [2,13].
Tissue samples from the margins of internal pulmonary parenchymal injuries, cutaneous entry and exit lesions, subcutaneous tissue, and adjacent intercostal musculature were fixed in 10% neutral-buffered formalin, embedded in paraffin wax, sectioned at 4 µm, and stained with hematoxylin and eosin (H&E). Histopathological examination evaluated hemorrhage, fibrin deposition, cellular inflammatory response, and microscopic evidence of thermal injury or foreign particulates.
3. Case Presentation
3.1. External Examination
External examination revealed an intact hair coat with focal blood-staining on the right shoulder and left axilla. Following clipping of hair, a discrete circular skin defect measuring 6 mm in diameter was identified over the right scapular region, surrounded by a faint circumferential abrasion collar (Figure 1A). In the left axillary region, an irregular, slightly elongated, stellate skin defect measuring approximately 14 mm × 9 mm was observed, accompanied by an eccentric zone of superficial epidermal abrasion along its caudoventral margin, morphologically compatible with an exit wound with possible shoring (Figure 1A). Palpation revealed marked crepitus over the left lateral thoracic wall consistent with subcutaneous emphysema. No evidence of contusion, laceration, or skeletal fracture was identified in the head, spine, pelvis, or extremities.
3.2. Radiographic Findings
Orthogonal thoracic radiographs revealed multiple (6–8) discrete, irregularly shaped, sharply marginated metallic opacities ranging from 1.0 mm to 3.5 mm in maximal diameter, clustered primarily in the left ventral and mid-thoracic region projecting over the left 4th to 6th intercostal spaces (Figure 1B). A moderate-to-large volume of pleural effusion was evident, characterized by bilateral scalloping of lung lobes, dorsal retraction of pulmonary margins, and generalized soft-tissue opacity obscuring the ventral cardiac silhouette and diaphragmatic line. Thoracic subcutaneous emphysema was marked along the left lateral body wall. Retrospective evaluation of the lateral projection demonstrated an irregular cortical discontinuity and step-off deformity at the mid-shaft of the left fourth rib, partially obscured by forelimb musculature.
3.3. Postmortem Computed Tomographic Findings
PMCT provided comprehensive three-dimensional mapping of the thoracic trauma. An oblique, displaced fracture of the left fourth rib was identified at its mid-to-dorsal third, with outward (lateral) displacement of the cortical margins. Clustered hyperattenuating metallic fragments (CT attenuation > 3000 HU) were embedded within the disrupted intercostal musculature and parietal pleura immediately adjacent to the fractured rib (Figure 1C,D). Additionally, a moderate volume of bilateral pleural effusion (CT attenuation ranging from 35 to 50 HU, consistent with unclotted to partially clotted blood) was documented, and several tiny metallic fragments (1–2 mm) had migrated into the dependent aspect of the left costodiaphragmatic recess within accumulated pleural fluid. Marked left-sided pneumothorax was identified, accompanied by extensive thoracic subcutaneous emphysema along the left thoracic wall, as well as a prominent mediastinal shift to the contralateral (right) side indicating left-sided tension pneumothorax. The left lung lobes showed severe passive compression atelectasis, while the right lung lobes exhibited patchy alveolar consolidation compatible with contusion and hemorrhage.
Careful examination of the cranial mediastinum revealed focal pneumomediastinum and mild mediastinal widening with soft tissue attenuation along the prospective right dorsal-to-left ventral trans-thoracic tract connecting the cranial lobes. However, the major mediastinal vascular structures—including the cranial vena cava, aortic arch, brachiocephalic trunk, and left subclavian artery—remained intact with preserved wall continuity and no evidence of transection or pseudoaneurysm. Adjacent organs including the esophagus, trachea, heart, and pericardium demonstrated no signs of traumatic rupture, blunt contusion, or temporary cavitation injury. Whole-body CT survey confirmed the complete absence of traumatic or pathological abnormalities in the calvarium, brain parenchyma, cervical/thoracolumbar vertebrae, and abdominal viscera.
3.4. Necropsy Findings
Diaphragmatic puncture under water submersion yielded immediate release of pressurized gas bubbles, confirming the presence of pneumothorax prior to opening the pleural cavity. Upon thoracic entry, approximately 100 mL of dark red, liquid to partially clotted blood (hemothorax) was evacuated from the thoracic cavity, with marked accumulation on the left side.
Detailed dissection of the pulmonary parenchyma revealed distinct focal transcapsular laceration tracts. In the right cranial lung lobe, a perforating defect entered the lateral surface (defect 8 mm × 6 mm) and exited the medial aspect (9 mm × 7 mm), surrounded by dark hemorrhagic parenchymal cuffs. In the left cranial lung lobe, a corresponding through-and-through transcapsular laceration (entry 9 mm × 8 mm, exit 12 mm × 10 mm) traversed the ventral third, presenting ragged, hemorrhagic margins. The wound trajectory formed a direct anatomical continuum across the ventral cranial mediastinum located ventral to the major vascular structures, connecting the right entry site to the left thoracic wall defect.
On the inner surface of the left thoracic wall, severe tearing of the fourth intercostal artery, vein, and parietal pleura was present adjacent to the fractured left fourth rib, representing the primary source of the hemothorax, alongside bleeding from the lacerated cranial lobar pulmonary vessels. Extensive intramuscular and fascial hemorrhage involved the left axillary and pectoral musculature directly underlying the left axillary skin defect. Careful dissection of the fractured rib and perilesional soft tissues yielded five deformed metallic fragments (aggregate weight 1.78 g), which were cataloged and preserved for forensic ballistics. No large intact projectile core was identified within the carcass.
Detailed inspection of the right internal thoracic wall revealed focal laceration and extensive muscular hemorrhage within the right third and fourth intercostal spaces surrounding the entry tract; however, the right intercostal neurovascular bundles remained grossly intact without major arterial transection, indicating that right hemithoracic fluid primarily originated from the lacerated right pulmonary parenchyma and associated capillary bed.
3.5. Histopathological Findings
Histopathological examination of the margins of the pulmonary transcapsular lacerations revealed extensive disruption of alveolar architecture, massive alveolar and interstitial erythrocyte extravasation, dense fibrin meshwork deposition, and early marginating and infiltrating neutrophils within adjacent capillaries and perivascular spaces (Figure 2B). Fibroblastic proliferation, mature collagen deposition, and hemosiderin-laden macrophages were entirely absent. These findings confirmed an acute antemortem vital reaction, indicating that the dog was alive when the projectile traversed the lungs, with survival estimated at between several minutes and less than one hour.
Histological evaluation of the right scapular skin defect revealed epidermal and dermal mechanical perforation, collagen bundle tearing, and acute dermal hemorrhage. Importantly, there was no epidermal coagulation necrosis, epithelial heat distortion, or dermal carbon/gunpowder particulate deposition. Sections of the left axillary exit defect showed full-thickness epidermal laceration and subcutaneous hemorrhage without thermal changes. These histological characteristics confirm mechanical projectile trauma without close-range or contact thermal-blast phenomena.
4. Discussion
This case demonstrates the complementary diagnostic value of integrating digital radiography, PMCT, forensic necropsy, and histopathology in the medicolegal evaluation of fatal projectile trauma in a companion animal(Table 1) [1,2,3,4,7,9,11,13,14]. In veterinary forensic medicine, projectile-induced trauma often occurs in the context of non-accidental injury (NAI) or suspected animal cruelty, requiring examiners to provide an objective, scientifically defensible determination of the cause of death and reconstruction of traumatic events [1,3,4]. When investigative circumstances lack firearm recovery or ballistic verification, a rigorous multimodal postmortem approach provides the essential evidentiary bridge between physical lesions and legal interpretation.
PMCT virtopsy served as an indispensable pre-dissection tool in this investigation. As previously emphasized in both human and veterinary forensic literature [2,7,9,10,13,14], conventional necropsy alone carries inherent risks of inadvertently altering small metallic fragment positions, creating artificial tissue tracts, or obscuring subtle bone fractures during rib cage reflection. By conducting thin-section helical PMCT prior to opening the thoracic cavity, we mapped the precise anatomical distribution of metallic fragments—distinguishing fragments embedded in the left fourth intercostal musculature from those resting gravitationally in the dependent pleural recess—and documented the displaced oblique rib fracture. Furthermore, PMCT enabled a non-invasive survey of the entire carcass, confirming the complete integrity of the neurocranium, spine, and abdomen, thereby excluding concurrent traumatic or pre-existing debilitating pathology [2,7,9,14].
A critical pathophysiological question in forensic traumatology concerns the precise mechanism of death. In clinical veterinary emergency practice, traumatized dogs with isolated blunt or penetrating chest trauma frequently present with small-to-moderate hemothorax or pneumothorax and can achieve excellent survival rates with tube thoracostomy and conservative therapy [5,6]. A hemothorax volume of approximately 100 mL in a 9.8 kg dog represents approximately 12% to 15% of total circulating blood volume (calculated at ~80–90 mL/kg), which alone would induce moderate compensatory hypovolemia rather than immediate exsanguination [5,6]. However, in the present case, necropsy and PMCT demonstrated the catastrophic synergy of concurrent bilateral pulmonary transcapsular lacerations and left-sided tension hemopneumothorax. The pressurized accumulation of pleural air (confirmed by positive underwater diaphragmatic puncture) and blood caused severe compression atelectasis of the left lung lobes, profound mediastinal shift, and substantial ventilation-perfusion mismatch. Concurrently, elevated positive intrathoracic pressure collapsed the cranial and caudal vena cava, drastically diminishing cardiac venous return and precipitating acute obstructive circulatory shock and rapid respiratory arrest. This multi-factorial failure explains the acute fatal outcome.
Reconstruction of the projectile pathway is another paramount objective in forensic analysis [3,4,8,17]. The convergence of physical and imaging findings in this dog establishes a highly defensible right-to-left trans-thoracic trajectory: (1) an initial entry defect on the right scapular region displaying a small circular diameter (6 mm) with an abrasion ring; (2) continuous transcapsular laceration tracts traversing the right cranial lung lobe and left cranial lung lobe across the cranial mediastinum; (3) direct impact and outward displacement of the left fourth rib mid-shaft; (4) localized fragmentation and retention of metallic debris along the left thoracic wall; and (5) an irregular, larger (14 mm) exit-type defect in the left axilla (Figure 3). The left axillary skin defect displayed features compatible with an exit wound with possible shoring, likely caused by the dog collapsing into left lateral recumbency or the axilla being supported by ground/substrate at the moment of projectile emergence [3,4,8]. The outward beveling and displacement of the left fourth rib fragments provide conclusive anatomical confirmation that the projectile struck the inner cortical aspect of the rib from within the thoracic cavity, moving from medial to lateral [3,8].
The absence of temporary cavitation injury or remote parenchymal contusion in adjacent mediastinal structures (esophagus, trachea, and great vessels) is a notable ballistic finding. In high-velocity rifle injuries, expansive temporary cavitation produces widespread parenchymal tearing, micro-fractures, and extensive vascular ruptures distant from the permanent tract [3,8]. In this case, the highly localized permanent cavity and lack of collateral cavitation damage indicate that the projectile was either a low-to-medium-velocity projectile (such as a handgun bullet or high-power airgun slug) or had significantly decelerated before entering the thoracic cavity, expending its residual kinetic energy primarily during impact with the left fourth rib [3,4,8]. Furthermore, histopathological examination of the entry cutaneous margins showed an absence of dermal heat necrosis, epithelial scorching, or soot particles, definitively excluding a contact or close-range gunshot and indicating an intermediate-to-distant discharge [3,8].
Differential diagnoses for penetrating thoracic trauma in domestic animals include sharp-force injury (e.g., stabbing with knives, spears, arrows, or crossbow bolts) and dog-bite lacerations [3,4,9]. Sharp implements produce clean, linear incision margins, lacking circumferential abrasion collars, projectile fragmentation, or scattered metallic debris embedded in bone [9]. Bite trauma typically presents with paired ‘crush-tear’ punctures, canine tooth spacing patterns, and extensive subcutaneous avulsion [3,4]. The presence of fragmented hyperattenuating metallic material on PMCT, confirmed by necropsy recovery of metallic shards, firmly rules out impalement or animal bites and substantiates metallic projectile trauma [3,4,8].
Histopathological evaluation provided vital confirmatory evidence. The detection of fibrin networks, extravasated erythrocytes, and early marginating neutrophils within pulmonary laceration borders established an indisputable antemortem vital reaction [1,2,4]. The absence of fibroplasia, endothelial sprouting, or hemosiderin deposits indicates that the survival time was brief—likely within minutes to less than an hour post-injury. This microscopic timeline corroborated that the fatal collapse was directly attributable to the acute ballistic trauma rather than secondary infectious or delayed complications.
In companion animal gunshot case series (such as those reported by Olsen et al. [6], Capak et al. [5], and Grela et al. [7]), thoracic gunshot trauma accounts for 20% to 35% of presentations, carrying the highest mortality rate among anatomical regions due to rapid hemopneumothorax and cardiopulmonary arrest. The present case represents a classic yet forensically intricate example of fatal perforating thoracic trauma, illustrating the necessity of standardizing forensic virtopsy in veterinary medicine [2,7,11,13,14]. Collaboration between veterinary pathologists, veterinary radiologists, and forensic ballistics experts is paramount to advance the prosecution of animal cruelty and enforce animal welfare legislation.
5. Conclusions
This report documents a fatal thoracic perforating metallic projectile injury in a Jindo dog investigated through an integrated multimodal approach. Digital radiography, PMCT virtopsy, systematic forensic necropsy, and histopathology converged to establish an acute antemortem right-to-left trans-thoracic trajectory with pulmonary transcapsular lacerations, left fourth rib fracture, left thoracic wall metallic fragmentation, and fatal hemopneumothorax. PMCT proved crucial in mapping metallic fragments, evaluating skeletal integrity, and documenting life-threatening tension hemopneumothorax without disturbing physical evidence. Histopathological findings confirmed an acute vital reaction (<1 h survival) and excluded contact-range thermal discharge. This comprehensive workflow highlights the growing importance of veterinary forensic virtopsy and pathology in supporting legal investigations of suspected animal abuse and non-accidental trauma.