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A 72-hour water deprivation test was performed in 12 horses to determine clinical pathologic changes. Reference values for electrolyte (X) clearance, expressed as a percentage of creatinine clearance (CLCR; %CLCRX), were also determined. A comparison was made between urine concentration measurement techniques. Results of %CLCRX determination in 12 horses before water deprivation were 0.034 +/- 0.095 %CLCRNa, 42.4 +/- 9.8 %CLCRK, 0.352 +/- 0.190 %CLCRCl, and 0.710 +/- 0.250 %CLCRP. During water deprivation, there was individual variation for electrolyte clearances, but Na excretion increased significantly (P less than 0.01) at 24 and 48 hours. After 48 hours' water deprivation, %CLCRNa decreased significantly, but was still greater than the initial clearance. Plasma protein was a better indicator of water deprivation (dehydration) in the horse than was PCV. Electrolyte concentrations in serum and urine were determined. Little significant (P less than 0.01) change in acid-base values was noticed after 72 hours' water deprivation. Urine osmolality (as determined by osmometry) was compared with sp gr (determined by refractometry) in determining urine concentration. Initially, sp gr correlated well with urine osmolality determinations, but this correlation decreased after 48 hours.

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RESUMEN

Two mature horses were examined for changes in laboratory and physical findings after experimentally induced bladder rupture. The postrupture laboratory diagnostic changes, which provide valuable information for a correct diagnosis are described. Hematology, serum and peritoneal fluid sodium, potassium, calcium, phosphorous, creatinine, urea nitrogen, albumin and peritoneal fluid components were measured and evaluated versus time. Hyponatremia and hyperkalemia occurred, as well as increased concentrations of peritoneal fluid potassium and inorganic phosphorus. In addition, peritoneal fluid creatinine:serum creatinine and peritoneal fluid urea nitrogen:serum urea nitrogen ratios were followed with time. Hematology and cytology of the peritoneal fluid showed an inflammatory response to urine contamination of the abdominal cavity. Physical findings of tachypnea and tachycardia as well as a mild colic were absent until nearly 50 hours postrupture. Based on these findings, it was concluded that the peritoneal fluid creatinine:serum creatinine ratio was the most useful antemortem laboratory diagnostic aid.

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Rhodococcus (Corynebacterium) equi pneumonia is diagnosed by thoracic auscultation, radiographic and hematologic examination, and transtracheal aspiration. Treatment may be unsuccessful because of the organism's tendency to cause pulmonary abscesses. A 2-month-old, depressed, anorectic, febrile Quarter Horse colt, previously unresponsive to penicillin therapy, had loud, moist breath sounds in the ventral lung fields. Chest radiographs revealed pneumonia. Based on culture and sensitivity tests on organisms isolated from transtracheal washes, chloramphenicol and erythromycin, and then oral trimethoprim-sulfadiazine, were given, in addition to supportive therapy. The animal was fully recovered within 2 months.

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Weight loss, poor growth and dysphagia occurred in a young stallion with some teeth missing, and soft, discolored and/or deformed deciduous incisors, premolars and molars. At necropsy, permanent teeth sites were filled with yellow, gelatinous material. Clinical signs suggested fluorosis but laboratory findings did not confirm the diagnosis.

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Two horses with ataxia of all four limbs were found to have cervical intervertebral disc protrusion. Severe pelvic limb ataxia, proprioceptive deficits and spasticity were present in both horses with similar but less severe signs in the thoracic limbs. Cerebrospinal fluid analysis was within normal limits. Metrizamide myelography allowed definitive diagnosis in one case when a compression of the spinal cord was demonstrated at the level of the second intervertebral space. In the second case, an intervertebral disc protrusion between cervical vertebrae 6 and 7 was found at necropsy. Fiber degeneration with poor myelin staining characterized the spinal cords histologically.

RESUMEN

Arthrodesis of the proximal interphalangeal joint in horses, with 2 screws crisscrossing the joint, was compared with arthrodesis achieved by placement of 3 screws crossing the joint parallel to the long axis of the bone. The comparison was made by means of radiography, gross and histologic examinations, and motion evaluation. Additionally, the fused 1st and 2nd phalanges resulting from each method were subjected to breaking forces. Motion evaluation and direct examination of the fused area demonstrated that either procedure can be used to achieve arthrodesis consistently, and the breaking procedure indicated that the fused joints were as strong or stronger than areas penetrated by the cortical screws used in internal fixation. The fused area resulting from the parallel procedure was stronger than that from the crisscross procedure. The parallel procedure was easier, gave better alignment of 1st and 2nd phalanges, and was prone to less error in screw placement. It was concluded that arthrodesis by either procedure was satisfactory for treating osteoarthritis and related problems of the proximal interphalangeal joint in horses, but that the parallel procedure created a superior union between the 1st and 2nd phalanges during the first 120 postoperative days.

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