Empera or pleural purulent is the accumulation of purulent effusion in the pleural cavity due to the presence of infectious factors. The overall incidence of empyema in cats and dogs has not been determined. A study of 81 canine pleural and mediastinal effusions determined that the most common type of effusion was empyema, which was diagnosed in 16% of cases, while a review of pleural effusions in 82 cats showed that 14.5% of pus in empyema was found. Retrospective studies have shown that empyema in small animals can be unilateral or bilateral, although in most cases bilateral effusions.
Etiology
In small animals, the root cause of empyema is usually not determined. It is reported that dogs have a cause in 4–22% of cases, while the root cause is found in 35–67% of cases reported in cats. In canines, reported causes include foreign body migration, penetrating chest trauma, hematogenous or lymphatic transmission, esophageal perforation, parasite migration, progression of vertebritis, parapneumoinflammatory transmission, tumor formation, rupture of lung abscess, and iatrogenic causes (thoracic surgery or thoracic puncture). After determination, the most common cause is the migration of grass sheds or plant material, although the incidence of inhaled foreign matter may vary by region, climate, vegetation, and the prevalence of variety of work type.
In cats, reported causes include pneumonia, thoracic penetrating wounds, foreign body migration, parasite migration and hematogenous spread.
Although the main cause of cats is not yet known, it is generally believed that cat bites may be the direct main cause. Studies have shown that bacteria isolated from pleural infections are similar to those found in cat bites. Additionally, cats with empyema are 3.8 times more likely to live in multi-cat families, and in late summer and autumn, the incidence of empyema is higher when outdoor activities such as fighting and mating are increased. Nevertheless, the risk of empyema was not significantly increased in outdoor or male cats, and the recent history of wounds was documented in only a few cases. Recent reviews show that only 15.6% of the cases of cat empyema described in the literature (20 of the 128 total) are caused by bites.
Another explanation for the increased incidence of empyema in multi-cat families may be due to the additional risk of the development of upper respiratory tract infection, which may make cats susceptible to colonization of normal oropharyngeal flora in the lower respiratory tract. Several studies have shown pneumonia or lung abscess associated with empyema and suggest that parapneumonia spread may be a more common mechanism for empyema.
Microbiology
In dogs and cats, the prevalence of multibacterial infections is high, and the commonly cultured organisms include obligate anaerobic bacteria or a mixture of obligate anaerobic bacteria and facultative aerobic bacteria. The oral and upper respiratory tract appear to be common sources of these organisms, representing the typical bacteria found.
fungal organisms are rarely reported, but include Cryptococcus, Candida albicans and Bacillus dermatitis. There may be geographical differences because tents are common locally and are related to actinomycetes.
Characterization Description
Although empyema can occur in any animal, it is often a disease of puppies and cats, usually 3-6 years old. However, case reports describe empyema and newborns at 1 and 4 months old. Although some groups have a lot of literature reports, the preference for gender or breed has not reached statistical significance. In several studies, male dogs and cats had too high proportions. In dogs, medium and large breeds are reported more common, with too many representatives of hunting breeds.
Among cats, the most commonly described are domestic shorthair cats, but they are not overrepresented compared to the local population.
Clinical Signs Clinical Signs of empyema are usually nonspecific, can be acute or chronic, and may be associated with pleural excretion or pulmonary abscess. Common signs include shortness of breath, cough, loss of appetite, lethargy and weight loss, or signs related to pleural effusion. Because 50% or less cats may have fever, normal body temperature cannot rule out empyema. Other signs may be consistent with systemic inflammatory response syndrome or sepsis. Of the 80 cats with empyema, 40% met the clinical criteria for sepsis. In a retrospective study of 29 cats with severe sepsis, empyema was found to be the most common underlying disease. The occurrence of sepsis in empyema dogs is unknown.
Diagnosis
Under the medical history and physical examination results, empyema, or at least pleural effusion may be suspected. Thoracic imaging can be used to identify pleural effusions, but to clearly diagnose empyema, thoracic puncture and cytology of pleural effusions are required. Aerobic and anaerobic cultures and drug sensitivity are recommended, but many studies have shown that the culture positive rate is < 100%. Generally speaking, if an anaerobic infection occurs, the liquid may appear cloudy or opaque, may have flocs, and may emit a foul smell.
Clinical pathological results
Hematological abnormalities are most common in anemia and neutrophilia, with or without left shift. In a study of degenerative left shift in cats, empyema was found in 17% of cases. The most common biochemical abnormalities reported include hypoproteinemia (usually hypoalbuminemia), hypoglycemia or hyperglycemia, electrolyte abnormalities and mild elevations in liver enzyme activity.