Effects of withholding feed on thyrotropin-releasing hormone stimulation test results and effects of combined testing on oral sugar test and thyrotropin-releasing hormone stimulation test results in horses.

OBJECTIVE To assess effects of withholding feed on thyrotropin-releasing hormone (TRH) stimulation test results used in diagnosis of pituitary pars intermedia dysfunction in horses and determine effects of combined testing on results of the TRH stimulation test and the oral sugar test (OST) used in diagnosis of equine metabolic syndrome. ANIMALS 30 adult horses. PROCEDURES All horses underwent TRH stimulation tests under fed and nonfed conditions, an OST alone, and an OST combined with TRH stimulation testing. For TRH stimulation tests, plasma ACTH concentrations were measured before (baseline) and 10 minutes after (poststimulation) IV TRH administration. For the OST, plasma glucose and insulin concentrations were measured before (baseline) and 60 and 90 minutes after oral corn syrup administration. For combined testing, the TRH stimulation test was initiated immediately after 60-minute posttreatment sample collection for the OST. Results were compared among methods by Wilcoxon matched-pairs, signed rank tests, paired t tests, and Bland-Altman analysis. RESULTS Feeding conditions did not affect median ACTH concentrations when TRH stimulation tests were performed alone. Median baseline ACTH concentration did not differ between TRH stimulation tests performed alone (under fed or nonfed conditions) and those combined with OSTs. Median poststimulation ACTH concentration was significantly lower for combined tests than for solitary TRH stimulation tests. Mean 60-minute plasma glucose concentration was significantly lower for solitary OSTs than for combined tests, but this difference could not be attributed to TRH administration. CONCLUSIONS AND CLINICAL RELEVANCE Combined testing in the manner described impacted ACTH concentrations during TRH stimulation tests and is not recommended at this time.

SURGICAL CORRECTION OF A CERVICAL SPINAL FRACTURE IN A BENNETT'S WALLABY (MACROPUS RUFOGRISEUS).

Macropods are susceptible to trauma, and fractures of the cervical vertebrae due to collisions are relatively common. A 4-yr-old, intact male Bennett's wallaby (Macropus rufogriseus) was presented acutely nonambulatory and tetraparetic but with motor function present in all limbs. Cervical radiographs revealed a C4 vertebral fracture. Surgical stabilization was obtained through a ventral midline approach whereby the vertebral bodies were distracted and then secured with screws and polymethylmethacrylate (PMMA). Postoperative radiographs revealed restoration of the spinal canal and appropriate implant placement. The patient was discharged 4 days postoperatively and gradually recovered full neurologic function per the owner over the ensuing 10 wk. Subsequent radiographs obtained 10.5 mo postoperatively revealed a healed fracture with stable implants. The ventral spinal distraction and stabilization technique using screws and PMMA, as are used in the domestic dog, was successful in this wallaby despite its smaller vertebral size and comparable lack of soft-tissue support.