Intrahepatic Gas at Postmortem Computed Tomography: Forensic Experience as a Potential Guide for In Vivo Trauma Imaging

1. Intrahepatic Gas at Postmortem Computed Tomography: Forensic Experience as a Potential Guide for In Vivo Trauma Imaging[Original Articles] Jackowski, Christian MD; Sonnenschein, Martin MD; Thali, Michael J. MD; Aghayev, Emin MD; Yen, Kathrin MD; Dirnhofer, Richard MD; Vock, Peter MD

2. Introduction • Postmortem imaging: multislice computed tomography (MSCT) & magnetic resonance (MR) imaging VS traditional destructive autopsy in selected cases. • Intrahepatic gas (IHG) : a frequent finding • Yamazaki et al. as hepatic portal venous gas. Shiotani et al. nontraumatic deaths correlating the occurrence of intrahepatic portal venous gas with gastrointestinal distention(scanned in 2 hours). Traumatic causes of IHG were missing in this study as well as postmortem alterations such as putrefaction

3. Introduction • Intended to investigate the occurrence of IHG according to conditions, that are thought to influence the occurrence of IHG such as venous or systemic air embolism, artificial respiration, gastrointestinal distention, and putrefaction.

4. MATERIALS AND METHODS • 106 virtopsy cases • 18 cases(direct traumatic injury of the liver) ,1 case of adipocire, 1 case(in a glacier) that was scanned before defrosting as well as 1 newborn, and 1 fetus were excluded • Remaining 84 cases were investigated using the scanning procedures • IHG was assessed by a subjective observer-dependent grading score: • 0 (no gas within the liver) • 1 (small amounts of gas within the small peripheral intrahepatic vessels predominantly in anterior parts of the liver) • 2 (moderate amounts of IHG within major intrahepatic vessels) • 3 (large amounts of IHG, completely filling the major hepatic vessels)

5. MATERIALS AND METHODS A: Grade 0 B: Grade 1 C: Grade 2 D: Grade 3

6. MATERIALS AND METHODS • This grading was supported by an objective quantification of the IHG volume-- A three-dimensional volume-rendering model of the liver.

7. MATERIALS AND METHODS • The IHG location-- using the anatomic intrahepatic course of the gas-filled vessel . • When very small volumes didn't allow an assessment of the vessel course the occurrence of extra hepatic gas was used to distinguish between the different liver vessels.-- Small gas bubbles within the liver were verified to be within the hepatic veins, when additional gas was found within the right heart or the major systemic veins. A simultaneous occurrence of gas within the extra hepatic course of the portal vein indicated the intrahepatic portal vein as location of the IHG. Similarly, systemic arterial gas helped with the hepatic artery system. • This method was used when only the venous or the arterial part of the systemic vessel system or only the portal vein contained gas.

8. MATERIALS AND METHODS • Gastrointestinal distention: • Grade 0 (physiologic amounts of gas within bowel) • Grade 1 (slightly increased amounts of gas within bowel) • Grade 2 (distinctively increased amounts of gas within bowel) • Grade 3 (severe intestinal distention with ballooning of the abdomen)

9. MATERIALS AND METHODS A: Grade 0 B: Grade 1 C: Grade 2 D: Grade 3

10. MATERIALS AND METHODS • All included cases were investigated for radiologic signs of putrefaction—extra luminal intraparenchymateous collection of gas • signs of putrefaction noted within the autopsy protocols(ex.green coloration of the skin in the abdominal region) • Putrefaction was found to be positive when at least the radiologic or one autoptical sign was positive. • The five definite putrefaction cases were excluded from statistical calculations leaving 79 cases to be further investigated

11. MATERIALS AND METHODS • All cases were checked for the presence of systemic gas embolism--when gas was visible at MSCT lung window settings within cardiac cavities, major systemic vessels, or both, and no signs of putrefaction were noted within the autopsy protocol or seen at postmortem imaging.

12. MATERIALS AND METHODS • The cases were checked for open trauma • Artificial respiration :received extensive resuscitation attempts or died under intensive care conditions • Relations between the findings were analyzed (contingency table, [chi]2, p < 0.01) and the postmortem intervals (PMI) were compared (t test, two tail).

13. RESULTS

14. RESULTS

15. RESULTS • IHG occurred in 42 cases (50%) without definitive signs of putrefaction. • the gas distribution was as follows: hepatic arteries:21 , hepatic veins:35 , portal vein branches:13, Combinations: 20. Unclassified:2 . In 2 cases, gas was detected exclusively within the hepatic arteries, in 16 cases within the hepatic veins, and in 2 cases within the portal vein branches. • Two intrahepatic vessel systems occurred for-- hepatic arteries and hepatic veins: 9 cases, for hepatic veins and portal vein branches: 1 case, hepatic artery and portal vein branches: 1 case. • Three intrahepatic vessel systems :9 cases.

16. RESULTS • Intestinal distention was diagnosed in 61 cases (72.6%) (grade 1–38 [45.2%]; grade 2–17 [20.2%]; grade 3–6 [7.1%]) and 1 of the burned corpses was not diagnosable because of the destruction of the bowel

17. RESULTS • Systemic gas embolism was diagnosed in 42 cases (50%). Of the systemic gas embolism cases, 39 (92.9%) presented also with IHG. Only three of the nonputrefied IHG cases (7.1%) presented without systemic gas embolism. All three were burned corpses. • There was a strong significant relation of the finding of IHG and systemic gas as well as a strong significant relation between systemic gas and traumatic cause of death

18. RESULTS • There was no significant relation between the occurrence of gastrointestinal distention (all gradings) and IHG in our data although in grade 3 gastrointestinal distention five of six cases showed IHG. All of the IHG cases involving the intrahepatic branches of the portal vein showed at least grade 1 distention. • Artificial respiration was noticed in 31 (39.2%) of the nonputrefied cases and showed no significant relation to the occurrence of IHG.

19. RESULTS • After exclusion of the five putrefaction cases the mean postmortem interval (PMI) in 42 cases showing IHG was 29.1 hours (standard deviation 14.3 hours) and in 37 cases without IHG 29.3 hours (s 15.8 hours). There was no significant difference in PMIs of both groups.

20. RESULTS • Of the 79 nonputrefied cases, 48 (60.8%) presented with an open trauma as cause of death . Of these, 32 (66.7%) also showed IHG. There was a significant relation between open trauma and the occurrence of IHG in our population.

21. DISCUSSION

22. Intrahepatic Venous Gas • most frequent location of IHG in this study • trauma with gas embolism to be the commonest cause of intrahepatic venous gas • craniocerebral trauma and head shot wounds were associated with IHG • We also hypothesize this to be the mechanism for intrahepatic venous gas accumulation. Other traumatic injuries might also cause gas to enter the hepatic venous system such as blunt or open abdominal trauma.

23. Intrahepatic Venous Gas • it remains arguable whether a retrograde gas transport into the liver veins occurs passively postmortem when the corpse is stored in supine position because of the ascending force.

24. Intrahepatic Venous Gas Either an active and vital retrograde gas transportation downwards into the hepatic veins resulting from an increased right ventricular pressure after total gaseous occlusion of the right ventricular outflow tract and pulmonary artery, or a passive gas transport caused by buoyancy from right atrium into the liver veins, when the corpse was stored and scanned in supine position, might have been responsible.

25. Intrahepatic Arterial Gas • Gas can enter the arterial system via a patent foramen ovale combined with an increasing right atrial pressure in gaseous pulmonary artery embolism. • pass the pulmonary capillary bed or in direct pulmonary trauma (contusion, laceration) with damage to the alveolar-capillary barrier it may reach the pulmonary veins • alveolar rupture because of emphysema aquosum in cases of drowning or because of pulmonary barotrauma caused by high-inspiratory pressures during artificial respiration to cause systemic arterial gas emboli.

26. Intrahepatic Arterial Gas • The 31 artificial respiration cases included only 14 cases with IHG and thereby had a lower percentage of IHG (45.2%), as compared with the entire population studied (53.2%). • In some cases of natural death (cases 85, 90, 101, and 106), resuscitation seems to be the only obvious mechanism allowing gas to enter the vascular system

27. Intrahepatic Portal Venous Gas • Portal venous gas occurred in 13 cases and exclusively in 2 of them • portal venous gas is indicative of necrotic bowel disease • Blunt traumatic injury is rarely • Portal venous gas was also described in child abuse

28. Intrahepatic Portal Venous Gas • we assume a damage to the barrier between the intestinal lumen and the capillary bed of the mesentery to be responsible for the portal venous gas, comparable to the clinical experience in necrotic bowel disease. • Case 69 was based on a person who was hit by a motorcycle and suffered fatal abdominal blunt trauma indicating traumatic damage of the mucosa allowing intestinal gas to enter the portal venous system • Case 86 was based on a person who succumbed to lethal oral intoxication with severe necrosis of the intestinal mucosa and grade 2 distention.

29. Intrahepatic Portal Venous Gas • Other 11 cases with portal venous gas either already showed putrefaction signs or also presented with gas in further hepatic vessels. Because most of them also had suffered trauma, we assume the mechanism of the gas entry to the portal vein was through the capillary bed of the intestine after arterial gas embolism.

30. Intrahepatic Portal Venous Gas • Massive amounts of portal venous gas were also present in strangulation (case 87).We postulate a passage of the arterial gas via the mesenteric capillary bed into the portal vein as cause for the massive portal venous gas

31. A:case 78 • B:case 69 • C:case 87 • D:case 36

32. Burned Corpses • The development of intravascular gas was assumed to be caused by heat in all vessels. Remarkable is the fact that burned corpses were the only exception that showed IHG without systemic gas embolism.

33. Putrefaction • Putrefaction was only found to be a cause of relevant volumes of IHG in cases that showed radiologic signs of putrefaction or when signs of putrefaction were noticed during autopsy. • The earliest time that putrefaction gas starts developing is considered to be 1 to 2 days postmortem. Thus, in some cases with a PMI of more than 1 day, the measured gas volumes might have been influenced by beginning putrefaction.

34. Putrefaction • However, we assume that this is not a relevant influence on the volume of gas until secure signs of putrefaction are noticed either at autopsy or in postmortem imaging.This can be supported by the mean PMI in the group of cases with IHG (after exclusion of the five secure putrefaction cases) and the group without IHG.

35. Intestinal distention • Investigation of intestinal distention did notreveal any obvious relation to the occurrence of IHG except for grade 3 distention because the occurrence of IHG was not increased compared with the cases without distention.

36. CONCLUSION • IHG is a frequent finding in postmortem imaging in forensic medicine. • The most common cause is of a traumatic nature because of craniocerebral trauma or blunt forces. It is strongly related to the occurrence of systemic gas embolism.