Insulinoma in a 5-Year-Old Dexter Cow
A 5-year-old Dexter cow in the fifth month of pregnancy was referred to the Clinic for Ruminants and Swine, Department of Veterinary Medicine, Freie Universit€ at Berlin, Germany, by a local practitioner due to general weakness and ataxia that did not respond to treatment. Approximately 3 months before hospitalization the cow had suffered from two bouts of acute catarrhal mastitis, which were successfully treated by frequent milking and parenteral administration of tylosin a at a dosage of 10
... at a dosage of 10 mg/kg bodyweight once daily on ten consecutive days. Approximately 6 weeks after the second bout of mastitis (2 weeks before hospitalization), the cow had weakness and ataxia. There was severe hypoglycemia b (glucose concentration 21.6 mg/dL) while complete blood cell counts and differentials, bilirubin, blood urea, creatinine, magnesium, calcium, phosphate and iron concentrations remained within the reference range. c At examination, the cow's posture was characterized by a wide-based stance and reluctance to walk. The cow had symmetrical ataxia and hypermetria of all limbs, intention tremors of the head and a deficit in its menace responses. The ataxia was graded as 3À4 out of 5. 1 The cow demonstrated bilateral mydriasis and delayed pupillary reflexes (both direct and indirect). Other cranial nerve function and spinal reflexes were normal and there were no indications of head tilt, tail weakness, bladder atony, and perineal hypalgesia. The cow showed no signs of circling. Given the symmetrical ataxia and hypermetria of all limbs, the intention tremors and the deficit in its menace responses the tentative neurologic diagnosis was cerebellar ataxia. The body condition score was assessed 2 of 5. 2 Respiratory rate (36/min), heart rate (72/min), and body temperature (38.7°C) were within the reference range. Upon examination of the digestive tract, dysphagia was observed while the animal was ruminating. Rumen fluid was dripping from the oral cavity and a discharge containing rumen fluid was draining from the nostrils intermittently. Urinalysis yielded normal results. The color of urine was yellow to light amber and the specific gravity was normal (1.030; reference range 1.025-1.045). Neither glucose nor ketone bodies were detected in the urine. CBC and serum biochemistry revealed a low reticulocyte count (5.63 9 10 6 lL; reference range 6-8 9 10 6 lL) and a slight left shift (band neutrophils 0.31 9 10 3 lL; reference range 0-0.3 9 10 3 lL, segmented neutrophils 1.26 9 10 3 lL; reference range 1.3-4.5 9 10 3 lL), increased AST (86 U/L; reference range 0-50 U/L) and CK activities (860 U/L; reference range 0-150 U/L). Venous blood gas analysis identified a slightly increased Base Excess (6 mmol/L; reference range À3-+3 mmol/L), while the blood pH was within the reference range (7.39; reference range 7.35-7.45). NEFA d (0.6 mmol/L, reference range ≤0.4 mmol/L) were slightly increased, but beta-hydroxybuyrate e (0.2 mmol/L, reference range ≤1.0 mmol/L) was normal. The plasma glucose concentration revealed insulinoma as a tentative diagnosis based on the normal BHB concentration a negative energy balance was considered unlikely. The increase in the activity of AST and CK was probably because of transportation. To exclude cerebrocortical necrosis, serum total thiamine concentration was determined by HPLC technique. 3 Total thiamine was 41 lg/L (reference range of >50 lg/L). No abnormalities were detected on endoscopy of the upper gastrointestinal and respiratory tracts or ultrasonographic examination of the liver, gallbladder, spleen, intestine, rumen, reticulum and kidney. On transabdominal ultrasonographic examination, pregnancy in an advanced stage was ascertained and fetal viability confirmed by measuring fetal heart rate (110 beats/min; normal fetal heart rate 90-125 beats/min).