Emergency Evaluation of Effusions — Sample Handling, Cell Identification, Important Findings
Aug 01, 2007
CVC IN KANSAS CITY PROCEEDINGS
An acute abdomen is defined as the acute onset of abdominal pain. Possible underlying etiologies are broad ranging, and include the gamut from trauma to infectious and neoplastic causes. An effusion is defined as the escape of fluid into a part. Effusive processes can occur in essentially every tissue in the body. The ability to obtain this fluid for cytologic evaluation limits the types of samples that are amenable to examination. Synovial fluid, aqueous humor, cerebrospinal fluid and serous body cavity fluids are all routinely evaluated in veterinary medicine. Obtaining and rapidly assessing effusions are keys to the diagnosis, choice and institution of therapy, and the ultimate outcome of many cases.
Normal effusions are due to a combination of factors including Starlings forces, pressure differential across the visceral pleura that favors absorption, lymphatic drainage, mesothelial cell activity and the stoma between mesothelial cells. The different cavities can have a large, ongoing exchange of fluid and solute, yet a low, stable volume is maintained. Crudely, effusions form when there is an imbalance between formation and resorption
The power of the clincopathologic evaluation of effusions is undeniable. Using widely available tools and instruments, samples can be obtained with minimal risk to the patients, yet the diagnostic yield can be tremendous, depending on the specific disease entity present. The indication to obtain and evaluate fluid is often determined based on the history, physical examination, radiographic / ultrasonographic findings or other finding.
Unless otherwise noted, sample preparation should be done using fluid from the EDTA. Direct smears using the blood smear technique is an extremely simple, fast technique to visualize nucleated cells in an effusion that has moderately high to high TNCC (>10,000/μl). This is the preparation that should be consulted if there are concerns about true, in vivo changes to cells and/or structures in the background. A drop of the fluid is placed on one end of a clean, new slide. The spreader slide is backed up into the drop, which then spreads towards, but not to the sides. The spreader slide is then advanced off the slide in one firm, smooth motion, producing a bullet shaped smear: