EMPF should be considered as a differential diagnosis for adult horses with interstitial pneumonia and should be suspected on the basis of characteristic radiographic, ultrasonographic, and histopathologic findings. Equine herpesvirus type 5 is found in association with EMPF; although the exact pathogenic role this virus plays in EMPF is unknown, equine herpesvirus type 5 may be an etiologic agent or cofactor in the development of EMPF.

Organ regeneration in mammals is hypothesized to require a functional pool of stem or progenitor cells, but the role of these cells in lung regeneration is unknown. Whereas postnatal regeneration of alveolar tissue has been attributed to type II alveolar epithelial cells (AECII), we reasoned that bronchioalveolar stem cells (BASCs) have the potential to contribute substantially to this process. To test this hypothesis, unilateral pneumonectomy (PNX) was performed on adult female C57/BL6 mice to stimulate compensatory lung regrowth. The density of BASCs and AECII, and morphometric and physiological measurements, were recorded on days 1, 3, 7, 14, 28, and 45 after surgery. Vital capacity was restored by day 7 after PNX. BASC numbers increased by day 3, peaked to 220% of controls (P<0.05) by day 14, and then returned to baseline after active lung regrowth was complete, whereas AECII cell densities increased to 124% of baseline (N/S). Proliferation studies revealed significant BrdU uptake in BASCs and AECII within the first 7 days after PNX. Quantitative analysis using a systems biology model was used to evaluate the potential contribution of BASCs and AECII. The model demonstrated that BASC proliferation and differentiation contributes between 0 and 25% of compensatory alveolar epithelial (type I and II cell) regrowth, demonstrating that regeneration requires a substantial contribution from AECII. The observed cell kinetic profiles can be reconciled using a dual-compartment (BASC and AECII) proliferation model assuming a linear hierarchy of BASCs, AECII, and AECI cells to achieve lung regrowth.

BackgroundPheochromocytoma is the most common adrenal medullary neoplasm of domestic animals, but it is rare in horses. Antemortem diagnosis in horses is difficult, with clinical signs often being vague or non‐specific.ObjectiveThe objective of this study was to describe the clinical, laboratory, and pathologic findings of pheochromocytoma in horses.AnimalsThirty‐seven horses diagnosed with pheochromocytoma based on postmortem examination from 2007 to 2014.MethodsRetrospective case series.ResultsPheochromocytoma was identified in 37/4094 horses during postmortem examination. Clinical signs consistent with pheochromocytoma had been observed antemortem in only 7 cases, with the remainder being incidental findings. Colic was the most common presenting complaint (13 of 37 cases) and tachycardia was noted in 95% of cases (median heart rate of 86 bpm in clinical cases). Hyperlactatemia (median, 4.9 mmol/L) and hyperglycemia (median, 184 mg/dL) were the most common clinicopathologic abnormalities. Hemoperitoneum caused by rupture of pheochromocytoma was noted in 4/7 clinical cases. Concurrent endocrine abnormalities (eg, thyroid adenoma, adrenal hyperplasia, pituitary pars intermedia hyperplasia or adenoma, parathyroid C‐cell carcinoma) were found in 27/37 horses, with 8/37 horses having lesions consistent with multiple endocrine neoplasia syndrome as described in humans.ConclusionsPheochromocytoma was diagnosed in 0.95% of horses presented for necropsy. The majority of these were incidental findings, but pheochromocytoma was thought to contribute to clinical findings in 19% of cases, and multiple endocrine neoplasms were commonly seen. Usually an incidental finding at necropsy, pheochromocytoma may cause acute death from intraperitoneal exsanguination and should be considered in horses presenting with colic, tachycardia, and hemoperitoneum.

This clinical report describes 8 cases of branchial remnant cysts (BRC) in the horse. The horses presented with bimodal age distribution, with 5 cases in mature horses (age 8-21 years) and 3 in foals (age 1, 6 and 10 months). Mature cases presented for dysphagia or intermittent oesophageal obstruction (2/5), and retropharyngeal swelling (3/5), whereas respiratory stridor and visible mass were presenting complaints in the foals. Presence of a right-sided (5/8) or dorsally located (2/8) palpable retropharyngeal mass of 3-35 cm diameter was noted clinically; one left-sided mass was identified as an incidental finding at necropsy. Ultrasonography typically revealed a thick-walled cyst containing hypoechoic fluid with dependent hyperechoic masses consistent with blood clots. Radiographs and upper airway endoscopy were also consistent with a retropharyngeal mass. Fluid cytology revealed chronic haemorrhage in 6/8 cases, and squamous epithelial cells in one case. Histopathology in all cases demonstrated an epithelium-lined cyst with no smooth muscle or thyroid tissue. Two cases was subjected to euthanasia; one due to concurrent laryngeal anomalies and one due to financial constraints. The remaining 5 cases were treated via surgical excision. Post operatively, right laryngeal hemiplegia was observed in 4/5 cases. All previous reports of BRC in the horse have described juvenile individuals. Brachial remnant cyst should be considered a differential diagnosis for mature horses with masses of the throatlatch area and can be definitively diagnosed by the presence of squamous epithelium in aspirated fluid or by histopathology of the excised mass. Right recurrent laryngeal nerve damage is a common complication of surgery.

BackgroundThere is a markedly reduced half‐life of transfused RBCs when donor and recipient cats or humans are cross‐match incompatible. Only 10–20% of horses have naturally occurring alloantibodies. Therefore, cross‐match testing before blood transfusion is not always performed.HypothesisCross‐match incompatibility predicts shortened RBC survival time as compared to that of compatible or autologous blood.AnimalsTwenty healthy adult horses.MethodsProspective trial. Blood type, anti‐RBC antibody screen (before and 1 month after transfusion) and major and minor cross‐match determined 10 donor‐recipient pairs. Two pairs were cross‐match compatible, the remainder incompatible. Donor blood (4 L) was collected into citrate phosphate dextrose adenine‐1, labeled with NHS‐biotin, and transfused into recipients. Samples were collected at 1 hour and 1, 2, 3, 5, 7, 14, 21, 28, and 35 days after transfusion, and biotinylated RBCs were detected by flow cytometry. Horses were monitored for transfusion reaction during transfusion and daily for 5 days.ResultsCross‐match incompatibility was significantly associated with decreased RBC survival time (P < .001). The half‐life of transfused incompatible (cross‐match >1+) allogenic equine RBCs was 4.7 (95% CI, 3.2–6.2) days versus 33.5 (24–43) days for compatible pairings. Cross‐match incompatibility was associated with acute febrile transfusion reaction (P = .0083). At day 30, only 1 horse had developed novel anti‐RBC antibodies.Conclusions and Clinical ImportanceCross‐match incompatibility was predictive of febrile transfusion reaction and shortened transfused RBC survival, but did not result in production of anti‐RBC antibodies at 30 days. Cross‐match testing before transfusion is recommended.