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Abstract

Laparoscopy was performed on 6 horses (2 mares, 2 geldings, 2 stallions) to determine the normal laparoscopic anatomy of the equine abdomen. After withholding feed for 36 hours, horses were examined from the left and right paralumbar fossae, and the visceral anatomic structures were recorded by videotape and photography. One mare developed emphysema located subcutaneously at the primary laparoscopic portal; otherwise, there were no complications. The anatomic structures of diagnostic importance that were observed in the left half of the abdomen were the hepatic duct; left lateral and quadrate lobes of the liver; stomach; spleen; left kidney with the associated nephrosplenic ligament; segments of jejunum, descending colon, and ascending colon; left side of the male and female reproductive tracts; urinary bladder; vaginal ring; and mesorchium. Important structures observed in the right side of the abdomen were portions of the common hepatic duct; left lateral, quadrate, and right lobes of the liver; caudate process of the liver; stomach; duodenum; right dorsal colon, epiploic foramen; omental bursa; right kidney; base of the cecum; segments of jejunum, descending colon, and ascending colon; urinary bladder; right half of the male and female reproductive tracts; and rectum.

Free access
in American Journal of Veterinary Research

Summary

Surface oximetry was used to evaluate viability of the ascending colon in 60 horses with naturally occurring colonic volvulus or displacement. Tissue surface oxygen tension (Ps o 2 ) was measured on the serosal surface of the pelvic flexure after anatomic correction of the colonic obstruction. Horses with Ps o 2 > 20 mm of Hg were predicted to have viable colon; whereas, horses with Ps o 2 ≤ 20 mm of Hg were predicted to have nonviable colon. Results of surface oximetry were compared with final outcome. For surface oximetry, sensitivity (ability to accurately identify colon that was nonviable) was 53%, but specificity (ability to accurately identify bowel that was viable) was 100%. Negative predictive value (probability that a horse with Ps o 2 > 20 mm of Hg truly had viable bowel) was 87%, and positive predictive value (probability that a horse with Ps o 2 ≤ 20 mm of Hg truly had nonviable bowel) was 100%. The overall accuracy was 88%. Of the 45 horses that had a colonic Ps o 2 > 20 mm of Hg and survived, 7 had been given, on the basis of subjective assessment of visual criteria, a good prognosis, 28 had been given a guarded prognosis, and 10 had been given a poor prognosis. Of the horses that had a colonic Ps o 2 > 20 mm of Hg but died after surgery because of further colonic infarction, confirmed at necropsy, 4 had been given a poor prognosis, and 3 had been given a guarded prognosis. Of the 8 horses that had a colonic Ps o 2 ≤ 20 mm of Hg and died after surgery, 7 had been given a poor prognosis, and 1 had been given a guarded prognosis. We concluded that surface oximetry, a relatively noninvasive technique, provided a better prediction of survival in horses with colonic volvulus or displacement than did visual inspection alone.

Free access
in Journal of the American Veterinary Medical Association

Summary

The normal microvascular permeability of the ascending colon in horses and the microvascular permeability of that segment after ischemia and reperfusion were investigated. Microvascular permeability was estimated by the ratio of lymphatic protein to plasma protein concentration (Cl/Cp) at high lymph flow rates in 8 adult horses in 2 equal groups: normal and ischemic (2-hour period). Lymphatic flow rates and lymph and plasma protein concentrations were determined. Intestinal biopsy specimens were obtained at the end of each experiment. Flow independent values were selected and compared by one-way anova, and the mean and sem of these values were determined. The mean Cl/Cp ratios for the flow independent part of each data set were as follows: normal = 0.36 ± 0.08; ischemic = 0.70 ± 0.08. These groups were significantly different (P ≤ 0.0001). Microscopic evaluation revealed mild congestion and edema in the normal group. The ischemic group had mild to moderate mucosal degeneration, with moderate to severe congestion and edema. We concluded that ischemia of the ascending colon, when followed by reperfusion, results in a significant increase in microvascular permeability.

Free access
in Journal of the American Veterinary Medical Association

Summary

The medical records of 50 horses examined because of lacerations of the tendon of the superficial or deep digital flexor muscle were reviewed to determine whether any injury or treatment factors could be associated with outcome. Median age of horses treated was 4.5 years (range, 1.5 years to 15 years), and the median follow-up time was 5 years (range, 1.5 to 16 years) after injury. Horses were considered to have survived if they were alive more than 1 year after injury. Twelve of 16 horses that had 1 or the other tendon transected survived; 13 of 16 horses that had both tendons transected survived; and 14 of 18 horses that had partial tendon disruptions of 1 or both tendons survived. Of the 39 surviving horses, 27 horses returned to their original use, and 32 horses were sound for riding. Nine horses with 1 or both tendons transected were being used for athletic activities. Lacerated tendons were sutured in 16 horses, and 15 of these survived. Tendons were not sutured in 34 horses, and 24 of these survived. We were not able to detect any association between outcome and tendon sheath involvement or between outcome and limb involvement (forelimb vs hind limb).

Free access
in Journal of the American Veterinary Medical Association

Summary

To determine whether body direction in a trailer affects the degree to which a horse is excited (and presumably stressed) during transport, heart rates were measured in 8 Thoroughbred geldings transported over a 32-km route of county roads while tethered facing forward or backward in a 4-horse stock trailer. Heart rates also were measured on the horses while they were tethered facing forward or backward in the same trailer while it was parked. Heart rates decreased during the first 10 minutes for both groups, and remained stable after the first 15 minutes. Heart rates were not significantly different between horses facing forward or backward during transport or while parked. Heart rates were significantly (P < 0.05) higher for horses during transport, compared with those of horses in a parked trailer whether facing forward or backward.

Free access
in American Journal of Veterinary Research

Summary:

Twenty horses with 30 lesions were studied to evaluate the effects of intratumoral chemotherapy with cisplatin in sesame oil on equine sarcoids (n = 19), squamous cell carcinomas (n = 7), and squamous cell papillomas (n = 4). Treatment consisted of 4 sessions of intratumoral cisplatin chemotherapy at 2-week intervals. A controlled-release formulation of cisplatin in sesame oil was used to limit drug egress from the injection site. Mean dosage per session was 0.97 (±0.17, sem) mg of cisplatin/cm3 of tumor tissue treated for tumor volumes ranging from 10 to 20 cm3. Dosage tended to be slightly higher for smaller tumors and slightly lower for larger tumors. Tumor regression was observed in all horses. Complete response was observed in 18 of the sarcoids, 5 of the squamous cell carcinomas, and 4 of the squamous cell papillomas. The mean relapse-free interval was 21.6 and 14 months in horses with sarcoid and carcinoma/papilloma, respectively. The 1-year relapse-free rates were 87 and 65% for equine sarcoid and carcinoma/papilloma, respectively. In horses with relapse, 70% had tumor recurrence outside the treated field. Cisplatin-related local toxicosis was minimal. Intratumoral cisplatin chemotherapy was found to be a practical and effective treatment of sarcoid and squamous cell carcinoma/papilloma in horses.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Chemical and cytologic effects and bactericidal activity of gentamicin in septic synovial fluid were evaluated in an experimental model of infectious arthritis in horses. Septic arthritis was induced by inoculation of approximately 7.5 × 106 colony-forming units of Escherichia coli into 1 antebrachiocarpal joint in each of 16 clinically normal adult horses. Clinical signs of septic arthritis were evident 24 hours after inoculation. Horses were allotted to 3 groups: group-1 horses (n = 5) each were given 150 mg of gentamicin (50 mg/ml; 3 ml) intra-articularly (ia); group-2 horses (n = 5) each were given 2.2 mg of gentamicin/kg of body weight, iv, every 6 hours; and group-3 horses (n = 6) each were given buffered gentamicin, consisting of 3 mEq of sodium bicarbonate (1 mEq/ml; 3 ml) and 150 mg of gentamicin (50 mg/ml; 3 ml), ia. Synovial fluid specimens were obtained at posttreatment hour (pth) 0, 0.25, 1, 4, 8, 12, and 24 via an indwelling intra-articular catheter. Synovial fluid pH was evaluated at pth 0, 0.25, and 24. Microbiologic culture and cytologic examination were performed on synovial fluid specimens obtained at pth 0 and 24, and gentamicin concentration was measured in all synovial fluid specimens.

At pth 0, E coli was isolated from synovial fluid specimens obtained from all horses. Synovial fluid pH was lower (range, 7.08 to 7.16) and wbc count was higher (range, 88,000 to 227,200 cells/μl) and predominantly neutrophilic (95 to 99%) at pth 0 than before inoculation. Synovial fluid pH was lowered further (mean, pH 6.63) after ia administration of gentamicin in group-1 horses; mean pH remained unchanged (7.07) after buffered-gentamicin administration in group-3 horses. At pth 0.25, mean peak synovial fluid gentamicin concentration in horses of groups 1 and 3 (4,745 and 6,190 μg/ml, respectively) was 1,000 times greater than that in group-2 horses (5.1 μg/ml) at the same time. Synovial fluid gentamicin concentration in group-1 and group-3 horses was always greater than that in group-2 horses and remained greater than a minimal inhibitory concentration of gentamicin (2 μg/ml) against many common equine bacterial pathogens for at least 24 hours after injection. Further, the calculated apparent half-life and clearance of gentamicin in synovial fluid calculated after ia administration were similar in horses of groups 1 and 3. By pth 24, E coli could not be isolated from synovial fluid specimens obtained from group-1 horses. However, moderate to heavy growth of E coli was isolated from synovial fluid specimens obtained at pth 24 from horses in groups 2 and 3 (80 and 66%, respectively).

In selected cases, ia administration of unbuffered gentamicin may be a useful supplement to drainage, lavage, and systemic antibacterial and anti-inflammatory treatment in horses with naturally acquired infectious arthritis.

Free access
in American Journal of Veterinary Research

SUMMARY

Interstitial and bronchointerstitial pulmonary patterns are commonly observed in thoracic radiographs of Thoroughbreds. Prominent interstitial and bronchointerstitial pulmonary patterns are observed in clinically normal horses, and in horses with respiratory tract disease. Until recently, the relevance of these pulmonary patterns was not known. Previous studies indicated that bronchiolitis, bronchiolar epithelial hyperplasia, epithelial metaplasia, and bronchial arteriolar recruitment correlated strongly with the prominence of the interstitial and bronchointerstitial pulmonary patterns observed radiographically. We examined the content and distribution of collagen in the lungs of 7 clinically normal Thoroughbreds in race training. After standardized fixation, lung tissue was treated with a compound that selectively stains collagen. Standard morphometric techniques were used to determine the volume density of parenchymal tissue and parenchymal airspace, mean linear intercept (estimate of alveolar size), alveolar surface area-to-volume ratio, percentage of parenchyma composed of collagen, percentage of airway wall composed of collagen, and airway wall thickness. These values were compared with radiographic and histopathologic scores obtained from the same horses. The volume density of parenchymal tissue and small airway wall thickness correlated strongly with the prominence of the bronchial and bronchointerstitial pulmonary patterns observed radiographically. Small airway thickness was also highly correlated with the perceived prominence of the interstitial pulmonary patterns observed radiographically, and morphometric estimates of parenchymal tissue and parenchymal collagen. There were also strong correlations between the volume density of parenchymal tissue, the percentage of parenchymal collagen, peribronchiolar mononuclear cell infiltrates, and bronchiolar mucosal plication estimates. In horses with more prominent bronchiolar mucosal plication, there was a strong direct relation to the observed prominence of peribronchiolar and submucosal blood vessels, and the bronchial and bronchointerstitial patterns observed radiographically. Horses with prominent peribronchiolar mononuclear cell infiltrates also had more obvious interstitial and bronchointerstitial pulmonary patterns observed radiographically. There also was a direct correlation between the percentage of parenchymal collagen and the observed prominence of peribronchiolar and submucosal blood vessels in these horses. In all horses, there was a strong negative correlation between the estimated average alveolar size and the observed severity of the vascular and bronchial patterns observed radiographically.

Four horses with the greatest estimated airway wall and interalveolar collagen had more prominent interstitial and bronchointerstitial densities and histopathologic evidence of bronchiolitis. These horses had evidence of epithelial basement membrane disruption, with disorganized collagen fibers running between the adventitial layer and the epithelial basement membrane. Amounts of collagen were greater in the adventitia and interalveolar septa, with the fibers appearing larger and more coarse and disorganized. In horses with the greatest percentage of interalveolar septal collagen, accumulations of collagen were larger in the interalveolar septal tips. These findings suggest that horses with prominent interstitial and bronchointerstitial pulmonary patterns radiographically have undergone previous episodes of pulmonary injury, which has resulted in deposition of increased amounts of collagen in interalveolar septa and airway walls.

Free access
in American Journal of Veterinary Research

Objective

To determine the benefits of reducing the interval between surgical cytoreduction and intratumoral administration of cisplatin.

Design

Randomized clinical study.

Animals

70 horses with 89 incompletely resected T2- and T3-stage sarcoids (n = 64) and squamous cell carcinomas (25).

Procedure

Horses were given 4 intratumoral treatments of cisplatin at 2-week intervals. The first treatment was given at the time of, or immediately after, surgical resection for horses treated in accordance with the perioperative protocol (group 1). Horses in group 2 were treated with cisplatin after the skin healed following surgical resection in accordance with the postoperative protocol.

Results

A difference was not found in duration of overall local tumor control between the 2 groups. Patterns of treatment failures and interval to failure differed between the 2 groups. Length of the surgical scar was the only factor that affected prognosis; an increase in length was associated with a poorer prognosis. A detrimental effect of postoperative treatment was only found in tumors with a high tumor proliferative fraction. Local reactions were similar for the 2 treatment groups, and chronic reactions were not observed.

Conclusions and Clinical Relevance

Intratumoral administration of cisplatin is beneficial for treatment of cutaneous tumors in horses. Tumor repopulation during the interval between surgery and intratumoral administration of cisplatin decreases treatment efficacy. These results provide evidence of rapid tumor repopulation following surgical resection without a lag period for tumors with a high proliferation index. When tumor proliferation index is not known, it may be prudent to use the perioperative protocol. (J Am Vet Med Assoc 1999;215:1655–1660)

Free access
in Journal of the American Veterinary Medical Association