Atypical granulation in neutrophils of a domestic shorthair cat.

A 13-year-old male domestic short-hair cat presented for evaluation of labored breathing, hyporexia, and lethargy. Pertinent initial diagnostics yielded leukocytosis, characterized by neutrophilia and monocytosis. Numerous small, round, magenta granules were observed within all neutrophils in Wright-Giemsa-stained blood films on the day of presentation and the day thereafter. No other neutrophil morphologic abnormalities were present, making cytoplasmic toxicity highly unlikely. Hyperadrenocorticism was diagnosed based on the lack of suppression in a low-dose dexamethasone suppression test, and without other diagnostics, the cat was discharged on trilostane therapy. Neutrophil granules did not stain with Alcian blue pH 1.0, periodic acid-Schiff (PAS), PAS and Alcian blue pH 2.5, and toluidine blue. Electron microscopy identified no differences in the morphology of the secretory granules or other neutrophil features. Metabolic screening tests of the cat's urine did not identify a genetic metabolic disorder. However, serum α- and ß -hexosaminidase (HexA and HexB) activities were 4.3% and 0% of normal controls, respectively, which is supportive of GM2-gangliosidosis, that is, Sandhoff disorder. However, the historical, clinical, and electron microscopy findings did not provide evidence to confirm this genetic defect. To the author's knowledge, this is the first case of magenta-staining granules within neutrophils in a breed other than a Birman, Siamese, or Himalayan.

Hepatic insufficiency in two juvenile dogs with histoplasmosis.

A 9-month-old female intact toy poodle and a 1-year-old female intact Labrador retriever mix presented to separate teaching hospitals for chronic histories of malaise and clinicopathologic evidence of hepatic dysfunction. The signalment and clinical histories of these dogs prompted consideration of a congenital portosystemic shunt as a primary differential. However, microscopic evaluation of peritoneal effusion, pleural effusion, and peripheral blood samples from the dogs revealed round to ovoid yeast organisms morphologically most compatible with Histoplasma capsulatum. Additional testing confirmed histoplasmosis in each case. The poodle underwent a computed tomography (CT) study, which showed hepatomegaly with a spleno-gonadal shunt, pancreatic and gastric wall edema, and marked peritoneal effusion, findings compatible with portal hypertension and secondary acquired shunt formation. The dog was later humanely euthanized due to clinical deterioration, and on necropsy hepatic histoplasmosis was verified, with additional affected tissues comprising lungs and spleen. The Labrador Retriever mix responded clinically and clinicopathologically to antifungal therapy, though no abdominal imaging was performed to definitively exclude the possibility of a congenital portosystemic shunt. In retrospect, several features were more compatible with histoplasmosis than portosystemic shunt in these cases, including hyperbilirubinemia, effusion, and hepatomegaly. These findings serve as a reminder of the need to interpret serum biochemical findings in the context of the totality of the clinicopathologic data and imaging findings, as well as the diagnostic value of microscopy in the evaluation of hematologic and body cavity fluid samples.

Telangiectatic osteosarcoma in four dogs: Cytologic, histopathologic, cytochemical, and immunohistochemical findings.

Telangiectatic osteosarcoma is a rare variant of osteosarcoma histologically and clinically similar to hemangiosarcoma (HSA). This case series describes the imaging and cytologic features of four histologically confirmed telangiectatic osteosarcomas, including the use of cytochemical stains. Alkaline phosphatase (ALP) was applied to Wright-Giemsa-stained cytology slides, and Factor VIII immunohistochemistry was evaluated. Cytologic characteristics included atypical mesenchymal cells with evidence of acute and chronic hemorrhage. Telangiectatic osteosarcoma cases had positive ALP cytochemical staining, while control HSA cases were negative. Factor VIII immunohistochemistry was negative in telangiectatic osteosarcoma and positive in HSA. Cytologic diagnosis of telangiectatic osteosarcoma with positive ALP cytochemical staining can help differentiate this neoplasm from HSA.

Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.

Effect of lactic acid addition to equine whole blood on platelet aggregation measured by impedance aggregometry.

BACKGROUND: Acidemia in sick or injured horses is often due to lactic acid accumulation. Alterations in platelet function and hemostasis are among numerous deleterious effects caused by decreased physiologic pH. OBJECTIVES: We aimed to evaluate the effect of hyperlactatemia and resultant acidemia on platelet aggregation in equine whole blood using impedance aggregometry. METHODS: Platelet aggregation was measured using the Multiplate analyzer in whole blood from 34 healthy horses at baseline and after in vitro addition of lactic acid to adjust the pH. Platelet aggregation of each sample was quantified by the area under the curve measurement reported by the Multiplate system. The association between platelet aggregation and pH was analyzed using a linear mixed-effects model. The association of baseline platelet aggregation with hematocrits (Hcts), white blood cell (WBC) counts, and platelet counts was evaluated using Pearson's correlations. RESULTS: There was a significant association between acidemia and decreased platelet aggregation. No significant correlations were detected between platelet aggregation and Hct, WBC count, or platelet count. Platelet aggregation measured in healthy horses using the Multiplate analyzer showed substantial variation between animals. CONCLUSIONS: Acidemia caused by the addition of lactic acid to equine whole blood was associated with a mild though statistically significant decrease in platelet aggregation. In conjunction with other factors, this change may contribute to morbidity-related disorders of hemostasis, although its precise clinical relevance is uncertain.

Impact of preheparinization and sample volume on routine hematology findings in healthy cats.

OBJECTIVES: It can be challenging to collect sufficient blood from feline patients for both a biochemical profile and a complete blood count (CBC). The ability to generate accurate hematologic and biochemical data from a single, small (<2 ml) sample could reduce patient stress and improve clinical efficiency. The objective of this study was to determine the impact of preheparinization and/or sample size on routine hematology findings in cats. METHODS: Blood was collected from 20 healthy cats; measured aliquots were placed directly into tubes containing either EDTA or lithium-heparin (Hep). Within 2 mins, specific volumes were removed from the Hep tubes and placed in additional EDTA tubes. Four distinct sample sizes/types were created from each cat: (1) 1.3 ml EDTA (criterion standard); (2) 0.5 ml EDTA; (3) 1.3 ml Hep + EDTA; and (4) 0.5 ml Hep + EDTA. Three CBCs were performed on each sample using an automated bench-top hematology analyzer. Drops of blood were contemporaneously used to create three air-dried stained slides from each tube. Triplicate results were averaged for statistical analysis; results were compared across all sample types and against the criterion standard. Significance was set at P <0.05. RESULTS: Preheparinization did not significantly impact determinations of erythrocyte number, hematocrit, hemoglobin concentration, mean cell volume and neutrophil count. Platelet counts for the non-traditional samples correlated poorly with the criterion standard, although numbers could be effectively estimated using stained slides. Cell morphology was well preserved across all sample types. CONCLUSIONS AND RELEVANCE: These results indicate that a 0.5 ml preheparinized EDTA blood sample can generate clinically useful hematologic data (excluding platelet count) in cats, using a bench-top analyzer. Our findings support the collection of a single small (<2 ml) sample that can be used for both biochemical and hematologic analyses. Further studies are needed to verify these findings using other hematology machines and in diseased cats.