A 14-year-old intact female mixed-breed dog (body weight of 8.5 kg) was presented with dyspnoea. This condition had persisted for eight days and was treated by the referring veterinarian with antibiotics, prednisolone, and vitamins. On the following day, prednisolone was substituted by a single dose of dexamethasone. Six days before presentation in our clinic, benazepril (0.3 mg/kg, PO, SID) and furosemide (1.2 mg/kg, PO, BID) were prescribed additionally. The bitch was regularly vaccinated and dewormed, with the last deworming dating three months back. The dog had never been abroad. For three years, a generalized alopecia was apparent without any known cause because the owners had declined a thorough dermatological examination; only the head and the distal limbs showed hair growth. The last period of heat was observed three years ago by the owners. For around eleven months, the dog showed polyuria und polydipsia. Food intake and defecation were reduced during the last days prior to presentation. On physical examination, the dog showed a calm and attentive general condition in upright posture. Rectal temperature was 36.8 C; mucous membranes were pink and moist with a capillary refill time of one second. Palpation of the peripheral lymph nodes revealed slightly enlarged, relocatable, and unpainful mandibular lymph nodes. In addition, a senile cataract on both eyes was diagnosed. Heart rate was 120 beats/min, and during auscultation, the volume of the heart sounds was unequal in every heartbeat. The femoral pulse was palpable on both sides, and no pulse deficit was found. The respiratory rate was 24 breaths/min and abdominally intensified. During lung auscultation, slightly amplified breathing sounds were noticed. The abdomen was prominent and indolent. Based on anamnesis and clinical examination, the preliminary diagnosis of a hyperadrenocorticism was assumed.
A chest X-ray in two planes was performed (Figure 1).
The transthoracic echocardiography (LOGIQ S8, General Electric, Munich, Germany) showed a moderate dilated left atrium (left atrium (LA): 2.66 cm, aorta (AO): 1.39 cm, LA/AO: 1.91, normal range: <1.6). A round, hyperechoic mass with a maximum diameter of 1.63 cm was floating from the left atrium into the mitral valve leaflets (Figure 2). At that time, an obstruction of the mitral valve was apparent. A notable connection between this mass and the atrial wall could not be depicted. Hence, a left atrial thrombus was suspected. A neoplasia was considered as a differential diagnosis. In addition to the mass in the left atrium, also a moderate mitral regurgitation, a low-grade pulmonary insufficiency, and a minimal aortic and tricuspid insufficiency were observed. Systolic blood pressure was measured by a Doppler device (Eickemeyer  Doppler, Tuttlingen, Germany) and was 80 mmHg.
An ACTH stimulation test was performed. The basal serum cortisol level was 9.1 mug/dL (normal range: <0.9-4.5 mug/dL), and the post-ACTH serum cortisol level was 61.6 mug/dL. Cortisol levels after stimulation of >20 mug/dL indicate a hyperadrenocorticism.
Additional diagnostics like hematology and chemistry panels, an abdominal ultrasonography, and follow-up blood pressure and echocardiographic control were refused by the owners. The prescribed therapy with benazepril (0.3 mg/kg, PO, SID) and furosemide (1.2 mg/kg, PO, BID) was supplemented with clopidogrel (2 mg/kg, PO, SID).
After 19 days, the owner reported the sudden death of their dog.