The laboratory diagnostic approach to thoracic and abdominal effusions in the dog, cat, and horse

Abstract

Cases involving pleural and peritoneal effusions occur relatively frequently in clinical practice. Determining the underlying etiology in these cases relies mainly on fluid analysis. The technique used for obtaining the pleural or peritoneal fluid can impact greatly the results of the analysis. Most often used diagnostic tools include evaluation of gross appearance, Total Nucleated Cell Count / Total Protein (TNCC/TP) measurement, chemical/biochemical analysis (Lactate dehydrogenase and lactate, cholesterol, triglycerides, glucose, creatinine, pH, pO2, pCO2, and K measurements), cytology (identification of septic and non-septic inflammation and neoplasia), microbiology (Gram stain, culture, molecular techniques), and specific tests for certain clinical conditions and diseases. Classifying an effusion as transudate, modified transudate and exudate is traditionally based on the TNCC and TP values. New diagnostic methods encourage the clinician to approach the effusion etiologically instead of strictly following this traditional classification. Many of the diagnostic tests described in this review are simple and can be performed in-house, providing the clinician quickly with information about the cause of the effusion, essential for an effective treatment plan without wasting valuable time.

Utility of the Ratio between Lactate Dehydrogenase (LDH) Activity and Total Nucleated Cell Counts in Effusions (LDH/TNCC Ratio) for the Diagnosis of Feline Infectious Peritonitis (FIP)

“…However, this latter procedure has not be applied to the current samples due to the retrospective nature of this study, and because additional enzymatic treatments of the fluid may theoretically modify other proteins that are present in the effusion, including the enzyme LDH, thus falsely altering the results of biochemical analysis. The TNCC of FIP effusion is known to be lower than other types of inflammatory effusions [ 24 , 28 ], however the cellular count could be affected by the technology used by the cell counter: the result of our study should be therefore revaluated using different hematology analyzers.…”

“…Although the cytology and the physicochemical features of an effusion are often diagnostic for a given disease or suggestive of a specific physio-pathological process, the inclusion of additional biochemical tests on the same sample may increase the accuracy of the interpretation. For example, analytes such as creatinine, urea, potassium have been historically considered as markers for uroperitoneum, the measurement of lipase or amylase in effusion may support a diagnosis of pancreatitis, the measurement of triglycerides and/or cholesterol is usually employed to differentiate chylous from non chylous effusions, and low glucose concentrations is considered suggestive of bacterial infection [ 24 , 25 , 26 , 27 , 28 ]. More recently, additional specific markers have been recommended by some authors.…”

“…Based on TNCC, chemical analyses and cytology, all the effusions were first classified as reported in Table 1 , following the classification scheme proposed by Stockham and Scott [ 24 ] integrated with additional criteria proposed for feline effusions [ 25 , 26 , 27 , 28 ].…”

Evaluation of pleural fluid parameters related to cardiac diseases in cats

“…Another limitation was the small number of cats in each group that may affect the statistical analysis. In addition, the protein concentration in this study was measured using the supernatant after centrifugation of pleural fluid samples to avoid falsely high-protein concentrations [23]. Therefore, the results from this study cannot be used using uncentrifuged samples.…”

Diagnosis of Septic Body Cavity Effusion in Dogs and Cats: Cytology vs. Bacterial Culture

“…The most isolated bacterial species include aerobic or anaerobic bacteria, including Clostridium spp., Bacteroides spp., Fusobacterium spp., Pasteurella spp., and filamentous bacteria ( Nocardia spp., Actinomyces spp.) [ 12 ]. Some of these bacteria are demanding and challenging to grow in cultures, so a negative culture result does not exclude the presence of a bacterial infection if the cytological findings are compatible with this possible diagnosis.…”