Mechanical injuries rank 3rd, mortality-wise, after socially significant diseases such as ischemic heart disease or oncological pathology. Legally, mechanical injuries can result from accidents or be inflicted intentionally. Regardless of how a violent death is classified, only a forensic medical examiner is competent to conclude where a mechanical injury came from, whether it caused or contributed to death, and what the comorbid condition of this injury was.

Isolated mesenteric vascular injury (IMVI) of the small bowel is far from being a common mechanical injury. Reports found in literature [1] and the authors' own experience suggest this injury is, in fact, very uncommon. That is why IMVI is challenging for clinicians, being hard to diagnose timely, and for forensic medical examiners who need, as part of conventional investigative process, need to conclude on the cause and recentness of injury. A wrong forensic conclusion on the mechanism of IMVI might be due to the rarity of this pathology in forensic expert's practice, aggravated by lack of proper coverage in scientific literature.

Morphogenesis and mechanism of closed blunt abdominal trauma are covered in papers by forensic medical examiners A.A. Solokhin, A.A. Karandasev, S.V. Savchenko, Yu.A. Solokhin [2–4]. Several papers [5–8] deal specifically with digestive tract injuries. Some studies apply mathematics in the forensic examination of abdominal organ injuries1 [9].

Nevertheless, examination of isolated injuries to the mesentery and its vessels is covered in a few papers, and they show no methodological unity [5].

This is why the authors hereof sought to summarize data found in today's Russian and international literature on the morphogenesis and mechanism of isolated mesenteric injuries as well as on the examination of such.

Besides classical forensic medical papers on abdominal organ injuries, we sampled papers indexed in PUBMED and eLibrary.ru over the last two decades (2000 to 2020) by the keywords: mesenteric root rupture, diagnosis, forensic medical examination.

We further analyzed papers that covered such topics as:

We further analyzed a single forensic case of repeated forensic medical examination from the authors' practice.

From the facts of the case: a fight between two young men (aged below 40) occurred during New Year's Eve celebrations. Crime scene: the backyard of a detached house. The men used their hands and feet to inflict blows on each other's head, body, and limbs. Once clinched, both fell; the victim ended up lying on the back, and the attacker was on top. Men wrestling on the ground were then pulled apart. The fight lasted no longer than 1-2 minutes. The victim was able to go indoors, find the bathroom, and wash his face. He then felt weak, sat down on the floor, and lost consciousness. An ambulance was called. The victim died on the way to hospital. The fact of the case: ~1.5 h passed between the onset of the fight and the statement of death. Initial forensic medical examination reported abrasions on the face and limbs, a back bruise in the 9th-10th left rib projection along the left scapular line, a closed abdominal trauma, rupture of the small-bowel mesenteric root, and hemoperitoneum (2000 ml). The ambulance doctor did not recognize the closed abdominal trauma in vivo due to the victim's grave condition. The examiner's report did not specify each small-bowel mesenteric vessel(s) were damaged. Routine laboratory tests (forensic chemical and histological examination) were run as part of the primary forensic medical investigation of the corpse. Chronic viral hepatitis was reported posthumously as a concomitant pathology. No varicose veins of the esophagus as a sign of portal hypertension. The forensic medical examiner concluded with respect to the mechanism of the closed abdominal trauma, which directly caused the victim's death, that force was applied to the back in the projection of the 9th and 10th left rib where the bruise was found. The prosecution considered such injury to be intentionally inflicted. Yet, the defense questioned the forensic medical report with regard to the cause of closed blunt abdominal injury and commissioned a re-examination.

English researchers report the following breakdown of closed abdominal traumas (CAT): 6.4% are mesenteric or hollow-organ injuries; 6% are hepatobiliary injuries; 5.4% are spleen injuries; vascular damage accounts for 1.7% [10]. Other researchers claim injuries to the small-bowel mesentery and intestinal injuries account for 1–5% [11]. Great importance is attached to the commotion of the body in general [6][7]. A.A. Matyshev [7] reports mesentery injuries to have resulted from impact or from compression due to runover in 26% and 27% of all examined roadkills, respectively. Mesenteric rupture due to falling from a great height is not uncommon [7].

Yet, in the case of isolated mesenteric injury, damage to the large vessels has an occurrence rate of 0.2% at max [12].

51.2% of CAT victims are victims of road accidents (40% are women and 60% are men). Falling from a height of >2 meters accounts for 20.5% of all cases, with another 11.6% resulting from other falls, 11.6% being of unidentified cause [11].

A rare case is reported where IMVI is a result of repeated blows inflicted with a hard blunt object with a limited surface area; the victim (boy, 2.5 years old) developed intraabdominal hemorrhage [12]. However, in the case considered herein, blows were inflicted upon an adult, physically strong man.

The mortality rate of isolated injuries to intraabdominal organs and retroperitoneal space is 6.1%. Clinically, the best-studied course is that of retroperitoneal hematomas, which occur at a rate of 7% to 70% [13–15].

Given its anatomy and topographic anatomical location in the abdominal cavity, is not surprising that the rate of isolated injury to this internal abdominal organ fluctuates to such an extent.

Special medical literature (including literature on medical forensics) reports in detail on the mechanism and clinical course of abdominal traumas and abdominal organ injuries (injuries to the liver, the spleen, the retroperitoneal organs such as the kidneys and the pancreas) [3][16–19].

As for the cause of isolated small-bowel mesenteric injury with vascular rupture, the mechanism is either compression or blunt force trauma. IMVI is mainly observed in the case of road accidents when a person is injured inside a car due to impact against the steering will or being pressed against the seat belt. IMVI might also occur in an air accident due to fall from a great height [11].

However, inra vitam diagnosis of injuries to the small-bowel mesentery or the hollow organ remains complicated [11] due to lack of specific clinical signs coupled with the fast progression of a life-threatening condition.

What makes this injury so treacherous is that its initial symptoms can be nonspecific or totally absent. Lack of clear clinical signs results in high mortality due to untimely diagnosis. Intra vitam diagnosis relies on instrumental studies. Modern instrumental diagnostic methods include diagnostic laparocentesis to find the source of internal bleeding, abdominal and retroperitoneal ultrasound to find free fluid in the abdominal cavity, and computer tomography [11][21]. Laparocentesis has a sensitivity of 90% when searching for blood in the abdominal cavity; ultrasound has a sensitivity of 86% [22]. CT sensitivity in case of surgery-requiring mesentery or hollow-organ injury ranges from 53% to 92% [11].

Notably, most delayed laparotomies in clinical practice are due to small-bowel mesentery or hollow-organ injury [11].

The case under consideration shows IMVI to be a rare pathology. The vascular injury of the mesentery is always secondary to a closed blunt abdominal trauma, in this case, mesenteric rupture. Rupture of a large vessel is always a high risk of death. The rarity of this pathology is why publications on the topic are few and far between. Only a few authors pay attention to this pathology [6][7][19].

It is indisputable that massive blood loss is the key factor of fatal complications in case of mesenteric rupture and damage to the mesenteric vessels. Academically, and maybe for the needs of practical clinical (surgical) medicine, it is important to know which particular vessels are likely (and how likely) to break in cause of a mechanical injury. This implies a need to find the source of bleeding and study the vascular rupture morphology macro- and microscopically.

For a forensic medical examiner, finding the damaged mesenteric vessel(s) is no challenge. Postmortem angiography can objectively visualize the ruptured vessel(s) [23]. However, the authors' experience suggests such forensic reports are nearly impossible to find. Conventionally, histological examination of the small-bowel mesentery with damaged vessels seeks to find the signs of hemorrhage and cellular response, and to quantify the severity of inflammation; however, it is academically interesting in the sense that it can detect chronic pathological processes, e.g., portal hypertension. Yet, forensic medical papers on the issue are few and far between [24—26].

M.A. Sapozhnikova in her monograph Morfologiya zakrytoy travmy grudi i zhivota [Morphology of Closed Thoracic and Abdominal Trauma] [16] mentions not without reason that veins are more prone to damage than arteries due to the specific vascular wall anatomy. Of interest are the qualitative results presented by Juan A. Asensio et al. [1]. The authors analyzed five years' worth of cases of closed abdominal trauma with isolated injuries to the small-bowel mesentery and its vessels, and found some patterns in such injuries. Thus, the superior mesenteric artery and vein have roughly the same chance to be damaged. Of the 504 cases in the reviewed period, 28 (5.56%) had isolated rupture of the superior mesenteric artery, 33 (6.55%) had isolated rupture of the superior mesenteric vein [1].

Unpaired abdominal vessels exhibit significant locational variability [27]. This applies to where the arteries branch off the abdominal aorta and part of the aortic semicircle, how far they deviate in either direction, their length, outer diameter, and angle of branching from the aorta. Surgeons need the knowledge of such topography and anatomy first [28][29]. However, we believe forensic medical examiners, too, need to know the variations in the branching of unpaired arteries from the abdominal aorta, and the branching of their accompanying veins, when they have to examine a victim's corpse who succumbed to isolated mesentery trauma with vascular damage; this can expand the understanding of the mechanism behind such injuries. Yet, we have to state that as of today, there is no systematized data on typical, yet alone untypical location of unpaired vessels [30–32]. For space considerations, we cannot present the topography and anatomy of abdominal vessels in sufficient detail. This is why the authors hereof cite a list of references on the topic2 3 [33].

As known from clinical practice, blunt force trauma may cause arterial pseudoaneurysms (AP). APs are a possible result of abdominal trauma, whether open or closed. They might also result from poor medical aid. APs are caused by partial or total damage to the vascular wall; however, clinically significant blood loss may not occur over some time due to intact adventitia or compression by the tissue of the same vessel. Literature overview was unable to find specific AP timings. Time to develop APs after injury may vary. There are reports on massive fatal internal bleeding occurring 10 days after CAT, with an unrecognized vascular rupture and resulting pseudoaneurysm. All this time, the patient was under supervision of medical staff [34].

Yet the researchers emphasize blunt abdominal trauma resulting in vascular rupture and a pseudoaneurysm is highly unusual. Statistical data suggests aneurysms of visceral arteries are extremely rare at 0.1–0.2%. At the same time, innate or acquired pathologies (connective tissue dysplasia, arterial atherosclerosis, vascular wall inflammation) are the factors of predisposition to APs [35].

In this particular forensic case, routine histological examination was unable to clarify whether the damaged vessel was affected by a pathology.

Researchers agree unanimously that injuries to large mesenteric vessels quickly result in loss of circulation and imminent death. The abundance of bleeding is directly proportionate to the proximity of the damaged vessel. The length of survival after sustaining such an injury is not yet known for certain. The authors believe it is limited to 3 hours [12]. In this case, only 1.5 hours passed from inflicting the injury to the victim's death at max.

It is only logical some conditions contribute to more severe trauma. Besides the impact force and the duration of compression, the severity is affected by the relaxation of the abdominal wall muscles. In this case, the victim was under the influence of alcohol, which could be a contributing factor. Yet, we have not been able to find any scientific reports on whether the isolated injury depended on the degree of alcoholic intoxication.

1. Kimbar V.I. Mekhanogenez i morfologiya zakrytykh povrezhdeniy pecheni tupymi tvyordymi predmetami [Mechanogenesis and morphology of closed blunt liver trauma: a mathematical evaluation]. PhD in Medicine Thesis. Moscow, 2006. 2. Bolshakov O.P., Semyonov G.M. Operativnaya khirurgiya i topograficheskaya anatomiya [Operative Surgery and Topographic Anatomy]. University textbook. St. Petersburg: Piter, 2012. 958 p. 3. Kagan I.I., Kirpatovsky I.D. et al. Topograficheskaya anatomiya i operativnaya khirurgiya [Topographic Anatomy and Operative Surgery] in 2 volumes, Geotar-media, 2012