A diagnostic strategy for pulmonary fat embolism based on routine H&E staining using computational pathology

Pulmonary fat embolism (PFE) as a cause of death often occurs in trauma cases such as fractures and soft tissue contusions. Traditional PFE diagnosis relies on subjective methods and special stains like oil red O. This study utilizes computational pathology, combining digital pathology and deep learning algorithms, to precisely quantify fat emboli in whole slide images using conventional hematoxylin-eosin (H&E) staining. The results demonstrate deep learning's ability to identify fat droplet morphology in lung microvessels, achieving an area under the receiver operating characteristic (ROC) curve (AUC) of 0.98. The AI-quantified fat globules generally matched the Falzi scoring system with oil red O staining. The relative quantity of fat emboli against lung area was calculated by the algorithm, determining a diagnostic threshold of 8.275% for fatal PFE. A diagnostic strategy based on this threshold achieved a high AUC of 0.984, similar to manual identification with special stains but surpassing H&E staining. This demonstrates computational pathology's potential as an affordable, rapid, and precise method for fatal PFE diagnosis in forensic practice.

CT pulmonary arteriogram diagnosis of macroscopic fat embolism to the lung

Pulmonary fat embolism (PFE) is a recognised complication of long bone fractures. The majority of cases represent microscopic embolism and are not detectable at CT pulmonary arteriography (CTPA). CT can be used to detect macroscopic fat based on Hounsfield attenuation. This case describes a case of macroscopic fat embolism to the pulmonary arteries which was confidently diagnosed at CTPA. Distinction from thromboembolism is important as treatment is supportive and may avoid risks of anticoagulation.

Pulmonary fat embolism in non-survivors after cardiopulmonary resuscitation

BACKGROUND

Blunt trauma acting against the human body presents the fundamental cause of pulmonary fat embolism (PFE) and fat embolism syndrome. The aim of the present study was to investigate PFE in non-survivors after cardiopulmonary resuscitation (CPR).

METHODS

This was a prospective cohort study conducted in University Hospital Ostrava, Czech Republic. Within a 4-year study period, all non-survivors after CPR because of out-of-hospital cardiac arrest were assessed for the study eligibility. The presence/seriousness of PFE was determined by microscopic examination of cryo-sections of lung tissue (staining with Oil Red O).

RESULTS

In total, 106 persons after unsuccessful CPR were enrolled in the study. The most frequent cause of death in the study population (63.2% of cases) was cardiac disease (ischemic heart disease); PFE was not determined as the cause of death in any of our study cases. Sternal fractures were identified 66.9%, rib fractures (usually multiple) in 80.2% of study cases; the median number of rib fractures was 10.2 fractures per person. Serious intra-thoracic injuries were found in 34.9% of cases. Microscopic examination of lung cryo-sections revealed PFE in 40 (37.7%) study cases; PFE was most frequently evaluated as grade I or II. Occurrence of sternal and rib fractures was significantly higher in persons with PFE than between persons without PFE (p = 0.033 and p = <0.001). Number of rib fractures was also significantly higher in persons with PFE. The occurrence of serious intra-thoracic injuries was comparable in both our study groups (p = 0.089).

CONCLUSIONS

PFE presents a common resuscitation injury which can be found in more than 30% of persons after CPR. Persons with resuscitation skeletal chest fractures have significantly higher risk of PFE development. During autopsy of persons after unsuccessful CPR, it is necessary to distinguish CPR-associated injuries including PFE from injuries that arise from other mechanisms.

A case report

BACKGROUND

So far, there have been more than 761 million confirmed cases of SARS-CoV-2 worldwide, with more than 6.8 million deaths. The most common direct causes of death for COVID-19 are diffuse alveolar injury and acute respiratory distress syndrome. Autopsy results have shown that 80-100% of COVID-19 patients have microthrombi which is 9 times higher than in patients with influenza. There are reported cases of fat embolism associated with Covid-19, but relevant epidemiological investigations and fatal cases of pulmonary fat embolism are lacking. In this report, we describe the first COVID-19 patient to die from pulmonary fat embolism.

CASE PRESENTATION

A 54-year-old woman suddenly felt unwell while at work. She had difficulty breathing for 40 min and lost consciousness for 20 min before being taken to the hospital. On admission, her temperature was 36 ℃, but her respiration, heart rate, and blood pressure were undetectable. Laboratory examination revealed C-reactive protein, 26.55 mg/L; D-dimer, 11,400 µg/L; and procalcitonin, 0.21 ng/mL. She was declared clinically dead 2 h after admission due to ineffective rescue efforts. At autopsy, both lungs were highly oedematous with partial alveolar haemorrhage. The presence of microthrombi and pulmonary fat embolism in small interstitial pulmonary vessels was confirmed by phosphotungstic acid haematoxylin staining and oil red O staining. The immunohistochemical results of spike protein and nucleocapsid protein in laryngeal epithelial cells confirmed SARS-CoV-2 infection.

CONCLUSIONS

Pulmonary fat embolism may be another fatal complication of COVID-19 infection, and clinicians should pay more attention to it.

Rare, fatal pulmonary fat embolism after acupuncture therapy: A case report and literature review

BACKGROUND

Death from nontraumatic pulmonary fat embolism associated with minor soft tissue contusion, surgery, cancer chemotherapy, hematologic disorders and so on has been reported. Patients often present with atypical manifestations and rapid deterioration, making diagnosis and treatment difficult. However, there are no reported cases of death from pulmonary fat embolism after acupuncture therapy. This case emphasizes that the stress induced by acupuncture therapy, a mild soft tissue injury, plays an important role in pulmonary fat embolism. In addition, it suggests that in such cases, pulmonary fat embolism as a complication of acupuncture therapy needs to be taken seriously, and autopsy should be used to identify the source of fat emboli.

CASE PRESENTATION

The patient was 72 years old female and experienced dizziness and fatigue after silver-needle acupuncture therapy. She experienced a significant drop in blood pressure and died 2 h later despite treatment and resuscitation. A systemic autopsy and histopathology examination (H&E and Sudan Ⅲ staining) were performed. More than 30 pinholes were observed in the lower back skin. Focal hemorrhages were seen surrounding the pinholes in the subcutaneous fatty tissue. Microscopically, numerous fat emboli were observed in the interstitial pulmonary arteries and alveolar wall capillaries, in addition to the vessels of the heart, liver, spleen and thyroid gland. The lungs showed congestion and edema. The cause of death was identified as pulmonary fat embolism.

CONCLUSION

This article suggests that high vigilance for risk factors and the complication of pulmonary fat embolism following silver-needle acupuncture therapy should be exercised. In postmortem examinations, it should be pay attention that the peripheral arterial system and the venous system draining from non-injured sites should be examined for the formation of fat emboli, which can help distinguish posttraumatic and nontraumatic pulmonary fat embolism.

Fat embolism after intraosseous catheters in pediatric forensic autopsies

In our center, we performed the autopsy of a child who died from drowning and presented, at autopsy, a major pulmonary fat embolism (PFE). A cardiopulmonary resuscitation (CPR) was performed, including infusion by intraosseous catheter (IIC). No other traumatic lesions and diseases classically related to a risk of PFE were detected. According to some animal studies, we considered the IIC as the only possible cause for PFE. However, we could not find literature to confirm this hypothesis in humans, especially in a pediatric population. To verify the occurrence of PFE after IIC in a pediatric population, we retrospectively selected 20 cases of pediatric deaths autopsied in our center, in which a CPR was performed, without bone fractures or other possible causes of PFE: 13 cases with IIC (group A) and 7 cases without IIC (group B). Several exclusion criteria were considered. The histology slides of the pulmonary tissue were stained by Oil Red O. PFE was classified according to the Falzi scoring system. In group A, 8 cases showed PFE: 4 cases with a score 1 of Falzi and 4 cases with a score 2 of Falzi. In group B, no case showed PFE. The difference between the two groups was statistically significant. The results of our study seem to confirm that IIC can lead to PFE in a pediatric population and show that the PFE after IIC can be important (up to score 2 of Falzi). To the best of our knowledge, our study is the first specifically focused on the occurrence of PFE after IIC in a pediatric population by using autoptic data.

Radiological features of pulmonary fat embolism in trauma patients: a case series

PURPOSE

Fat embolism syndrome (FES) is a rare complication in trauma patients (usually with long bone fractures) in which migrating medullary fat precipitates multiorgan dysfunction, classically presenting with dyspnoea, petechiae and neurocognitive dysfunction. Although this triad of symptoms is rare, it nonetheless aids diagnosis of pulmonary fat embolism (PuFE). Typical imaging features of PuFE are not established, although increasing use of CT pulmonary angiography (CTPA) in this cohort may provide important diagnostic information. We therefore conducted a case series of FES patients with CTPA imaging at a Level 1 Trauma Centre in Melbourne, Australia.

METHODS

Medical records and various radiological investigations including CTPA of consecutive patients diagnosed clinically with FES between 2006 and 2018, including demographics, injury and their progress during their admission, were reviewed.

RESULTS

Fifteen FES patients with retrievable CTPAs were included (mean age 31.2 years, range 17-69; 12 males [80%]). 93.3% had long bone fractures. CTPA was performed 2.00 ± 1.41 days post-admission. Review of these images showed pulmonary opacity in 14 (93.3%; ground-glass opacities in 9 [64.3%], alveolar opacities in 6 [42.9%]), interlobular septal thickening in 10 (66.7%), and pleural effusions in 7 (46.7%). Filling defects were identified in three (20%) CTPAs, with density measuring - 20HU to + 63HU. Ten patients (66.7%) had neuroimaging performed, with two patients demonstrating imaging findings consistent with cerebral fat emboli.

CONCLUSION

CTPA features of PuFE are variable, with ground-glass parenchymal changes and septal thickening most commonly seen. Filling defects were uncommon.

Approaching pulmonary fat embolism on postmortem computed tomography

PURPOSE

Pulmonary fat embolism (PFE) is a relevant diagnosis playing a role as a sign of vitality or a cause of death. Its severity is assessed according to histological grading systems like that of Falzi. The aim of this study was to determine the utility of unenhanced postmortem computed tomography (PMCT) for PFE diagnosis based on the detection of fat layers.

METHODS

Consecutive cases with PMCT and autopsy were studied retrospectively. The case group consisted of cases with positive PFE, and the control group included cases with negative PFE. Three observers independently assessed PMCT data for fat layers in the pulmonary trunk and the right and left pulmonary artery. For cases with fat layers, autopsy protocols were assessed for the cause of death, relation to trauma, and undertaken resuscitation measures.

RESULTS

Eight hundred thirty cases were included: 366 PFE positive cases (144 of Falzi grade 1, 63 of 1.5, 99 of 2, 28 of 2.5, and 32 of 3) and 464 PFE negative cases. Interrater reliabilities varied between substantial and almost perfect, and discrepancies were solved according to majority. Eighteen cases showed fat layers on PMCT (2 controls-traumatic instantaneous deaths-, 16 PFE positive cases). PMCT showed low sensitivity but high specificity for PFE diagnosis. The layers were located at the same position in the pulmonary trunk directly adjacent to the pulmonary valve distal to the right ventricle.

CONCLUSION

Fat layer on PMCT is a rare finding but relates to PFE diagnosis, especially of severe histological grade. It is to be expected in a typical position within the pulmonary trunk.

An unusual case of pulmonary fat embolism following blunt trauma

Fat embolism is markedly underdiagnosed, even though it is a well-known phenomenon following fractures of the long bones, injury to subcutaneous fat tissue, rupture of a fatty liver, surgical operations on fatty tissues, septicemia, burns and barotrauma. Forensic pathologists tend to "simplify" autopsy report conclusion in cases with multiple injuries where fat embolism and exsanguination could be considered to be the concomitant causes of death. Herein we present a case of 24-year-old male who was beaten with a metal rod by several persons. On admission to hospital his vital signs and laboratory findings indicated hemorrhagic shock with gradual respiratory failure; he died 17 h after injury. On internal autopsy examination the subcutaneous tissue of the limbs and back was severely bruised, corresponding to about 35% of the body surface area. He had fractures of several small bones. Injuries of the internal organs were absent, there was no free blood in the body cavities, and all other autopsy findings were unremarkable but suggestive of a significant blood loss. Microscopic examination showed a massive pulmonary fat embolism (grade III according to Sevitt), without systemic fat embolism. The cause of death was attributed to pulmonary fat embolism combined with severe blood loss, following extensive and severe bruising of the subcutaneous tissues and bone fractures.

Detection of pulmonary fat embolism with dual-energy CT: an experimental study in rabbits

OBJECTIVES

To evaluate the use of dual-energy CT imaging of the lung perfused blood volume (PBV) for the detection of pulmonary fat embolism (PFE).

METHODS

Dual-energy CT was performed in 24 rabbits before and 1 hour, 1 day, 4 days and 7 days after artificial induction of PFE via the right ear vein. CT pulmonary angiography (CTPA) and lung PBV images were evaluated by two radiologists, who recorded the presence, number, and location of PFE on a per-lobe basis. Sensitivity, specificity, and accuracy of CTPA and lung PBV for detecting PFE were calculated using histopathological evaluation as the reference standard.

RESULTS

A total of 144 lung lobes in 24 rabbits were evaluated and 70 fat emboli were detected on histopathological analysis. The overall sensitivity, specificity and accuracy were 25.4 %, 98.6 %, and 62.5 % for CTPA, and 82.6 %, 76.0 %, and 79.2 % for lung PBV. Higher sensitivity (p < 0.001) and accuracy (p < 0.01), but lower specificity (p < 0.001), were found for lung PBV compared with CTPA. Dual-energy CT can detect PFE earlier than CTPA (all p < 0.01).

CONCLUSION

Dual-energy CT provided higher sensitivity and accuracy in the detection of PFE as well as earlier detection compared with conventional CTPA in this animal model study.

KEY POINTS

• Fat embolism occurs commonly in patients with traumatic bone injury. • Dual-energy CT improves diagnostic performance for pulmonary fat embolism detection. • Dual-energy CT can detect pulmonary fat embolism earlier than CTPA.

Fat embolism in pediatric patients: an autopsy evaluation of incidence and etiology

INTRODUCTION

Little is known about the incidence and etiology of fat embolism in pediatric patients. We sought to determine the incidence, time course, and associated factors of pulmonary fat embolism (PFE), cerebral fat embolism (CFE), and kidney fat embolism (KFE) in trauma and nontrauma pediatric patients at the time of autopsy.

METHODS

Retrospectively, a convenience sample of consecutive pediatric patients (age, ≤10 years) who had undergone autopsy between 2008 and 2012 were evaluated for fat embolism. Patients who had no documented cause of death or who were hospital births and died during the same hospitalization were excluded. Formalin-fixed paraffin sections were reviewed by a forensic pathologist for evidence of fat embolism and nuclear elements. Autopsy reports were used to determine cause of death, injuries, resuscitative efforts taken, sex, height, weight, and age.

RESULTS

Sixty-seven decedents were evaluated. The median age was 2.0 years (interquartile range, 0.75-4), median body mass index (BMI) was 18.0 kg/m(2) (interquartile range, 15.7-19.0 kg/m(2)), and 55% of the patients were male. Pulmonary fat embolism, CFE, and KFE were present in 30%, 15%, and 3% of all patients, respectively. The incidence of PFE was not significantly different by cause of death (trauma 33%, drowning 36%, burn 14%, medical 28%). Patients with PFE but not CFE had significantly higher age, height, weight, and BMI. Half of the PFE and 57% of the CFE occurred in patients who lived less than 1 hour after beginning of resuscitation. Seventy-one percent of patients with CFE did not have a patent foramen ovale. Multivariate regression revealed an increased odds ratio of PFE based on BMI (1.244 [95% confidence interval, 1.043-1.484], P = .015). None of the samples evaluated demonstrated nuclear elements.

CONCLUSIONS

Pulmonary fat embolism, CFE, and KFE are common in pediatric trauma and medical deaths. Body mass index is independently associated with the development of PFE. Absence of nuclear elements suggests that fat embolism did not originate from intramedullary fat.