Lipids of lung and lung fat emboli of the toothed whales (Odontoceti).

Lipids are biomolecules present in all living organisms that, apart from their physiological functions, can be involved in different pathologies. One of these pathologies is fat embolism, which has been described histologically in the lung of cetaceans in association with ship strikes and with gas and fat embolic syndrome. To assess pathological lung lipid composition, previous knowledge of healthy lung tissue lipid composition is essential; however, these studies are extremely scarce in cetaceans. In the present study we aimed first, to characterize the lipids ordinarily present in the lung tissue of seven cetacean species; and second, to better understand the etiopathogenesis of fat embolism by comparing the lipid composition of lungs positive for fat emboli, and those negative for emboli in Physeter macrocephalus and Ziphius cavirostris (two species in which fat emboli have been described). Results showed that lipid content and lipid classes did not differ among species or diving profiles. In contrast, fatty acid composition was significantly different between species, with C16:0 and C18:1ω9 explaining most of the differences. This baseline knowledge of healthy lung tissue lipid composition will be extremely useful in future studies assessing lung pathologies involving lipids. Concerning fat embolism, non-significant differences could be established between lipid content, lipid classes, and fatty acid composition. However, an unidentified peak was only found in the chromatogram for the two struck whales and merits further investigation.

Comparison of Three Histological Techniques for Fat Emboli Detection in Lung Cetacean's Tissue.

Fat embolism is the mechanical blockage of blood vessels by circulating fat particles. It is frequently related to traumas involving soft tissues and fat-containing bones. Different techniques have been used for decades to demonstrate histologically fat emboli, being the extremely toxic post-fixation with osmium tetroxide one of the most used techniques in the last decades. In the present study, the osmium tetroxide technique was compared qualitatively and quantitatively, for the first time, with chromic acid and Oil Red O frozen techniques  for histological fat emboli detection in the lungs of eight sperm whales that died due to ship strikes. This was also the first time that chromic acid technique was tested in cetaceans. Results showed that the three techniques were valuable for the histological detection of fat embolism in cetaceans, even when tissues presented advanced autolysis and had been stored in formaldehyde for years. Although quantitative differences could not be established, the Oil Red O frozen technique showed the lowest quality for fat emboli staining. On the contrary, the chromic acid technique was proven to be a good alternative to osmium tetroxide due to its slightly lower toxicity, its equivalent or even superior capacity of fat emboli detection, and its significantly lower economic cost.

Lipid emboli in a Vietnamese potbellied pig (Sus scrofa).

A 2-year-old, spayed female Vietnamese potbellied pig (Sus scrofa) was evaluated due to polyuria, polydipsia, lethargy, and hyporexia. The pig was obese, and a large abdominal mass was palpated. Additional findings included hypercalcemia, hyperglycemia, glucosuria, and an inflammatory leukogram. At surgery, the abdominal mass was biopsied and found to be bilaterally symmetric adipose tissue with mineralization and granulomatous steatitis. An additional surgery was performed to collect additional diagnostic samples, but the pig died while recovering from anesthesia. A cosmetic necropsy was performed, and lipid emboli were identified microscopically in various tissues. The presence of lipid emboli in the lung and kidney was supported by antifibrinogen immunohistochemistry. Obesity is a common finding in potbellied pigs; however, mineralization and saponification of fat are uncommon, particularly the bilateral symmetrical distribution found in the abdomen of the present case. This may present as a single intra-abdominal mass complicating diagnostic interpretation. Whether mineralization and saponification of fat facilitate the development of fat embolism is undetermined. Lipid emboli should be considered in obese pigs undergoing medical or surgical procedures. Factors that may predispose to the development of fat embolism, such as excessive handling or bruising of fat stores, should be avoided.

Pulmonary embolization of fat and bone marrow in cynomolgus Macaques (Macaca fascicularis).

Fat embolization (FE), the introduction of bone marrow elements into circulation, is a known complication of bone fractures. Although FE has been described in other animal models, this study represents the first reported cases of FE and bone marrow embolism in nonhuman primates. Histopathologic findings from cynomolgus macaques (Macaca fascicularis) indicated that in all 5 cases, fat and bone marrow embolization occurred subsequent to multiple bone marrow biopsies. In the most severe case, extensive embolization was associated pulmonary damage consistent with acute respiratory distress syndrome. Fat embolism syndrome (FES) is an infrequent clinical outcome of FE and is triggered by systemic biochemical and mechanical responses to fat in circulation. Although clinical criteria diagnostic of FES were not investigated at the time of death, this severe case may represent the fulminant form of FES, which occurs within 12 h after trauma. Bone marrow biopsy as an etiology of FES has been reported only once in humans. In addition, the association of embolization with bone marrow biopsies suggests that nonhuman primates may be a useful animal model of FE. FE and FES represent important research confounders and FES should be considered as a differential diagnosis for clinical complications subsequent to skeletal trauma.

Fat embolism secondary to yellow fat disease in an Appaloosa horse.

A 4-year-old female Appaloosa horse was referred to the Department of Comparative Pathology, Veterinary Faculty, with a history of colic and acute respiratory distress. At necropsy, gross lesions consisted of extensive firm, multinodular, hemorrhagic foci in fat tissues with yellow-brown discoloration. The most affected areas were peritoneal fat and perirenal, epicardial, and subcutaneous adipose tissues. Other findings were hepatic lipidosis and multiple 1-1.5 cm hemorrhagic foci scattered in both lungs. Histopathological examination revealed severe degeneration and necrosis of adipose tissue with dystrophic calcification. The necrotic fat was infiltrated by abundant foamy macrophages and multinucleated giant cells. Based on these histopathological changes, yellow fat disease, also called nutritional panniculitis, was diagnosed. In addition, the microscopic examination of lung and kidney sections stained with osmium tetroxide and oil red O revealed numerous lipid droplets within glomerular and alveolar septal capillaries. To the authors' knowledge, this is the first description of the development of fat embolism in horses affected by yellow fat disease.

"Gas and fat embolic syndrome" involving a mass stranding of beaked whales (family Ziphiidae) exposed to anthropogenic sonar signals.

A study of the lesions of beaked whales (BWs) in a recent mass stranding in the Canary Islands following naval exercises provides a possible explanation of the relationship between anthropogenic, acoustic (sonar) activities and the stranding and death of marine mammals. Fourteen BWs were stranded in the Canary Islands close to the site of an international naval exercise (Neo-Tapon 2002) held on 24 September 2002. Strandings began about 4 hours after the onset of midfrequency sonar activity. Eight Cuvier's BWs (Ziphius cavirostris), one Blainville's BW (Mesoplodon densirostris), and one Gervais' BW (Mesoplodon europaeus) were examined postmortem and studied histopathologically. No inflammatory or neoplastic processes were noted, and no pathogens were identified. Macroscopically, whales had severe, diffuse congestion and hemorrhage, especially around the acoustic jaw fat, ears, brain, and kidneys. Gas bubble-associated lesions and fat embolism were observed in the vessels and parenchyma of vital organs. In vivo bubble formation associated with sonar exposure that may have been exacerbated by modified diving behavior caused nitrogen supersaturation above a threshold value normally tolerated by the tissues (as occurs in decompression sickness). Alternatively, the effect that sonar has on tissues that have been supersaturated with nitrogen gas could be such that it lowers the threshold for the expansion of in vivo bubble precursors (gas nuclei). Exclusively or in combination, these mechanisms may enhance and maintain bubble growth or initiate embolism. Severely injured whales died or became stranded and died due to cardiovascular collapse during beaching. The present study demonstrates a new pathologic entity in cetaceans. The syndrome is apparently induced by exposure to mid-frequency sonar signals and particularly affects deep, long-duration, repetitive-diving species like BWs.

Fatal intraoperative pulmonary fat embolism during cemented total hip arthroplasty in a dog.

A 3-year-old, German shepherd dog died suddenly during cemented total hip arthroplasty. Gross necropsy findings included severe pulmonary edema and congestion as well as congestion of the liver and kidneys. Acute pulmonary embolism was suspected as the cause of death. Microscopic examination of hematoxylin and eosin-stained, formalin-fixed, and oil red O-stained frozen tissue sections confirmed the presence of large numbers of fat globules in blood vessels in the lungs, liver, and kidneys. Fat embolism during total hip arthroplasty is a common surgical complication in humans, but it is uncommon in veterinary cases and is rarely a cause of death.

Fatal pulmonary fat embolism during humeral fracture repair in a cat.

An 11-month-old cat was referred following a road traffic accident with non-weightbearing forelimb lameness and tachypnoea. A diaphragmatic rupture was repaired two days after trauma. Six days post trauma, a further operation was performed to repair the fractured humerus. As an intramedullary pin was advanced into the bone to achieve stabilisation, acute respiratory arrest occurred. Manual extrathoracic cardiopulmonary resuscitation was immediately instigated, but the cat did not recover. Postmortem examination identified a high degree of embolic fat occluding pulmonary capillaries. A massive embolic shower was established as the cause of death.

Crossed fat embolism in a cow with tetralogy of Fallot.

A 10-month-old, female Holstein-Friesian cow with tetralogy of Fallot died during surgery for ameliorating pulmonary stenosis. Necropsy revealed no fracture of bones. Microscopically, fat emboli in the capillaries were detected in the brain, kidney, lung, adrenal gland and pituitary. In the kidney, many fat emboli were present in the glomeruli. No significant changes of the neurons were found throughout the brain, and perivascular hemorrhage and/or necrosis were rarely seen accompanying with fat emboli in the cerebral cortex. The trigger for fat embolism might be costectomy, and right-to-left shunt due to heart malformation might be attributed to crossed and systemic distribution of the fat emboli.

[Fat-embolic vascular occlusions in avian lungs. Research of histologically determinable neutral fats in parrotlike birds (Psittaciformes)]. / Fettembolische Verschlüsse in den Blutgefässen der Vogellunge. Untersuchungen zum histologisch bestimmbaren Neutralfettgehalt papageienartiger Vögel (Psittaciformes)

In 50 flying birds (49 parrot-like, one peacock), the content of fat-embolic vascular occlusions was determined. In 22 cases, fat-embolic occlusions of low intensity were found in pulmonary capillaries. There were no occlusions in renal vessels. The fat embolies had no influence on a lethal outcome. There was no statistically significant correlation between the fatty infiltration of the liver, the fat content of the bone marrow, and the frequency of fat-embolic occlusion of blood vessels. In 18 cases, mycoses were the cause of death. These infections did not influence the number of fat-embolic vascular occlusions.