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clinical signs are usually not sampled. However, cysts with the following criteria in a patient with clinical signs should be aspirated: thick or irregular walls, internal echoes or septations, or a mass arising from the wall (Mattoon 2021). Gastrointestinal Tract (GI) Sampling of gastrointestinal masses is well reported in the literature with consistent results (Crystal 1993, Eich 2000, Bonfanti 2006, and Turner 2021). Cytologic sampling of GI tumors achieves complete or partial agreement with histopathology approximately 70% of the time. Samples are usually better at categorizing the etiology (i.e., neoplastic versus non-neoplastic) than identifying the exact etiology. Non-diagnostic samples are a common reason GI sampling is inaccurate. At this time, it appears lesions that are malignant, gastric, or thicker are more likely to yield a correct diagnosis. Submitting more slides may also help increase the likelihood of a correct diagnosis. Curiously, no complications were reported in any of the four aforementioned studies. Anecdotally, the author has heard veterinarians raise concern for septic peritonitis from inadvertent lumen puncture. This risk appears to be low and is further validated by the fact that needles are used to leak test small bowl intra- op as well as trocharize the stomach in patients with GDV. Furthermore, a recent abstract looked at the value of small intestinal mucosal aspirates to diagnose feline lymphoma (Geston 2023). The authors reported no complications when performing full thickness aspirates with 27G needles to collect cytologic samples for PCR antigen receptor rearrangement testing. Segments that were aspirated demonstrated muscularis thickening, mucosal hyperechogenicity, or an overall thickness of > 0.26 cm. While the author has not put this procedure into practice yet, his team does utilize FN-NA to sample abnormal GI lesions that demonstrate thickening or masses, especially when there is a loss of wall layering. Commonly diagnosed etiologies include neoplasia, histoplasmosis, pythiosis, and feline infectious peritonitis.
of the disease process itself or the result of sampling normal pancreatic tissue. In one study (Cordner 2010), aspirates from 20 healthy dogs with apparently normal pancreases yielded no samples that were of appropriate cellularity to be diagnostic. Fortunately, needle sampling did not cause a significant increase in pancreatic enzymes, which should reduce the fear of procedure associated pancreatitis. Other studies (Cordner 2015 and Crain 2015) confirm a low complication rate of 0 – 6%. When complications occurred in these studies, it was suggested that they were likely the result of other procedures and/or comorbidities, rather than from needle sampling alone. Although evidence is very limited in 11 dogs (Cordner 2015) and 7 cats (Crain 2015), cytologic agreement with histopathology is reported to be 91% and 86%, respectively. Similar to other organs, pancreatic cytology may be better at ruling in cancer rather than ruling it out (Mattoon 2021).
Ultrasound image of the pancreas. Photo courtesy of Dr. Amy Kaplan- Zattler, cVMA, DACVECC, MRCVS.
Adrenal Glands Adrenal gland aspiration is mainly indicated when there is a mass present. One study demonstrated that cytology is excellent in distinguishing mass as either medullary or cortical with an accuracy of 90% or higher (Bertazzolo 2014). However, it may not be accurate at differentiating benign from malignant adrenal gland neoplasia (Bertazzolo 2014). For years, veterinarians have not sampled adrenal masses in fear of inducing a hyper-/hypotensive crisis related to the presence of a pheochromocytoma. Fortunately, the literature does not support this fear. To date, there are no veterinary case reports of hypertensive crisis related to aspiration and only sparse human case reports. While some veterinarians have reported this complication anecdotally, the author has also witnessed a patient with a pheochromocytoma code from too much ultrasound transducer pressure as well as changing its position from lateral to dorsal. A retrospective case series by Sumner et al. reported only one case of tachycardia among 19 dogs undergoing FNA of adrenal gland lesions, 9 of which were confirmed to be pheochromocytoma. However, that dog also had
Ultrasound images of the small intestine (left image) and stomach (right image). Photos courtesy of Dr. Amy Kaplan- Zattler, cVMA, DACVECC, MRCVS.
Pancreas Both FNA and FN-NA techniques have been used to sample pancreatic disease in dogs (Cordner 2015) and cats (Crain 2015) with a diagnostic yield of ~ 70%. Non-
diagnostic samples are typically of low cellularity, which may the result
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