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Summary

A study of 15 American miniature horses (amh) that underwent surgical treatment for colic was performed. Information obtained from the medical records included signalment, clinical signs, type and location of gastrointestinal lesion, and postoperative complications. All 15 amh had intraluminal obstructions, attributable to feed impactions (11 horses), enteroliths (2), and sand (2). The most common location of obstruction was the small colon, which was involved in 9 of the 15 cases. All 15 amh survived and were discharged from the hospital. Six of the 15 amh underwent subsequent surgical treatment for abdominal disorders. Elapsed time between the first and second operations ranged from 1 month to 5 years. Intestinal adhesions were observed in all amh that were surgically treated twice. Thus, despite the fact that most of the amh had a simple intraluminal obstruction, 40% (n = 6) developed adhesions that required or complicated a second surgery. Of the 15 amh, 87% (n = 13) survived at least 12 months after the initial exploratory celiotomy. These findings suggest that most surgical abdominal conditions in amh can be corrected; however, precautions should be taken to avoid or minimize adhesion formation.

Free access
in Journal of the American Veterinary Medical Association

Summary

The microvascular anatomic features of the small intestine was described by correlating results of microangiography, light microscopy, gross studies, and scanning electron microscopy of vascular replicas in 14 horses. After heparinization, the horses were euthanatized, a length of jejunum was transected, and blood was flushed free of the circulation, using isotonic NaCl solution. In six horses, the circulatory system was perfused with a modified radiopaque medium and evaluated radiographically. These sections were then evaluated by standard histologic methods. Sections from 8 horses were perfused with 1 of 2 types of plastics and studied grossly or by scanning electron microscopy.

The margined arterial arcade gives rise to vessels that enter the jejunum at the mesenteric angle. These vessels penetrated either directly, by branching and entering on both sides of the mesenteric angle, or supplying only 1 side of the mesenteric angle. All these vessels continued in the submucosa branching extensively, forming a submucosal plexus. This submucosal plexus supplied the tunica muscularis, tunica serosa, and the mucosa. Vessels within the 2 muscle layers ran parallel to the muscle fibers and, consequently, perpendicular to each other. The arterial supply to the mucosa penetrated the muscularis mucosae and branched to supply 2 mucosal capillary networks. An eccentrically placed arteriole penetrated the base of the villus and spiralled to the tip where it "fountained" into a mesh-like capillary network, which descended peripherally in the villus to drain via 1 to 3, but most commonly 2 venules. Venules from adjacent villi united and drained via the submucosal veins. The second capillary network supplied the glands of the intestinal crypts. The capillary network around adjacent glands anastomosed just below the luminal surface. There were connections between this network and the base of the villus capillary network. Drainage of the glandular capillary network was through these connections and through the villus venules. There was no evidence of arterovenous anastomoses.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the nucleotide sequence of the equine intestinal fatty acid binding protein (I-FABP) gene, its expression in various regions of the gastrointestinal tract, and the use of measuring I-FABP in horses with colic.

Animals—86 horses with colic.

Procedure—The mRNA sequence for the I-FABP gene was obtained by use of a rapid amplification of complementary DNA ends technique. Comparative I-FABP gene expression was quantitated by use of a real-time reverse transcription-polymerase chain reaction assay. Amounts of I-FABP in abdominal fluid and plasma were measured by use of an ELISA kit. Association between I-FABP concentrations and clinical variables was performed by nonparametric analysis, and associations of these variables with intestinal ischemia were determined by the Spearman correlation test.

Results—The nucleotide sequence had 87% identity with human I-FABP. The I-FABP gene was highly expressed in the small intestinal mucosa but had low expression in the colon. High concentrations of I-FABP in abdominal fluid correlated with an increase in protein concentrations in peritoneal fluid and nonsurvival, whereas plasma I-FABP concentrations correlated with the necessity for abdominal surgery. Clinical variables associated with intestinal ischemia included the color and protein content of abdominal fluid and serum creatine kinase activity.

Conclusions and Clinical Relevance— Determination of I-FABP concentrations in abdominal fluid and plasma may be useful for predicting survival and the need for abdominal surgical intervention in horses with colic. Furthermore, serum creatine kinase activity and color and protein concentrations of abdominal fluid may be useful in the diagnosis of intestinal ischemia. (Am J Vet Res 2005;66:223–232)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of Carolina rinse solution, dimethyl sulfoxide (DMSO), and 21-aminosteroid, U-74389G, on microvascular permeability and morphology of the equine jejunum after low-flow ischemia and reperfusion.

Animals—20 healthy adult horses.

Procedure—Under anesthesia, full-thickness biopsy specimens of a distal portion of the jejunum were obtained for baseline measurements. In addition to a control segment, 2 jejunal segments were identified as sham-operated or experimental segments. Experimental segments underwent 60 minutes of low-flow ischemia and 3.5 hours of reperfusion. Treatments were as follows: U-74389G (3 mg/kg, IV; 6 horses), DMSO (20 mg/kg, IV; 6) diluted in 1 L of saline (0.9% NaCl) solution, local perfusion (via jejunal artery) of Carolina rinse solution (0.5 mL/kg; 4), and local perfusion of lactated Ringer's solution (0.5 mL/kg; 4).

Results—Jejunal microvascular permeability was significantly lower after treatment with Carolina rinse solution or DMSO, compared with U-74389G or lactated Ringer's solution treatments. After DMSO treatment, serosal- and submucosal-layer edema was significantly increased in experimental segments, compared with control or sham-operated segments; however, edema increases were significantly less than for lactated Ringer's solution or U-74389G treatments. Significant decreases in intestinal wet weight-to-dry weight ratio were found following Carolina rinse solution or DMSO treatments, compared with lactated Ringer's solution or U-74389G treatments. Edema formation and leukocyte infiltration in jejunal segments of horses treated with lactated Ringer's solution or U-74389G were increased, compared with Carolina rinse solution or DMSO treatments.

Conclusions and Clinical Relevance—Carolina rinse solution and DMSO may be protective against ischemia-reperfusion injury in the equine jejunum. (Am J Vet Res 2005;66:525–536)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine effect of leukocyte depletion on hematologic, morphologic, and metabolic variables of equine jejunum after induction of arterial lowflow ischemia and reperfusion by use of an extracorporeal circuit.

Animals—14 healthy adult horses.

Procedure—A segment of jejunum was surgically removed and maintained in an isolated circuit for 3 hours (control group), arterial flow was reduced to 20% of baseline for 40 minutes followed by 1 hour of reperfusion (low-flow group), or leukocyte depletion was filter-induced, and low-flow ischemia and reperfusion were conducted as in the low-flow control group (filter-treated group). Various metabolic, hemodynamic, and histomorphologic variables were evaluated, including effects of electrical field stimulation and L- N-nitro-arginine-methyl-ester (L-NAME) on contractile activity.

Results—The extracorporeal circuit appeared to maintain the jejunum within physiologic limits for an extended period. Low-flow ischemia with reperfusion induced significant differences in various measurements, compared with control specimens. Significant differences were not detected between the low-flow and filter-treated groups. Myeloperoxidase activity was greater in the low-flow group than the control group, whereas a difference was not detected between control and filter-treated groups.

Conclusions and Clinical Relevance—The extracorporeal circuit maintained intestine for 3 hours in a physiologic state and may be used for simulation of tissue injury. Leukocyte depletion generally did not attenuate the effects of low-flow ischemia and reperfusion on equine small intestine. ( Am J Vet Res 2001;62:87–96)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine efficacy of an extracorporeal circuit to maintain a segment of equine large colon for 3.5 hours and to evaluate the effect of low arterial flow on histologic and metabolic variables.

Sample Population—Segments of large colon from 15 healthy adult horses.

Procedure—The pelvic flexure was surgically removed and maintained in an isolated circuit. In the control group, tissue was evaluated for 3.5 hours, whereas in the low-flow group, arterial flow was reduced to 20% of baseline for 40 minutes followed by 2 hours of reperfusion. Various metabolic and hemodynamic variables were evaluated at 30-minute intervals. Effects of nitric oxide (NO) and L-N-nitro-arginine- methyl-ester (L-NAME) on contractile activity were determined, and histomorphologic evaluation was performed at the completion of the study.

Results—Low-flow ischemia with reperfusion caused significant histomorphologic differences, compared with the control group. In the low-flow group, significant differences included reduction in PaCO2, reduction in bicarbonate concentrations, increase in PaO2, and an increase in base deficit in arterial and venous blood samples. Other significant differences included increases in PCV, protein concentration, total WBC count, and albumin clearance for the low-flow group. Differences were not detected in inhibitory activity of the low-flow group relative to the control tissue with or without addition of NO and L-NAME.

Conclusion—The extracorporeal circuit maintained a segment of equine intestine for 3.5 hours and can be used to simulate ischemic injury. The extracorporeal circuit provides the potential to investigate pharmaceutic agents that can minimize intestinal injury. (Am J Vet Res 2000;61:1042–1051)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To use an extracorporeal circuit to evaluate effects of intraluminal distention on the jejunum of healthy horses.

Sample Population—2 jejunal segments from each of 5 horses.

Procedure—Jejunal segments were harvested and maintained in an extracorporeal circuit. One segment was subjected to distention (intraluminal pressure, 25 cm H2O) followed by decompression, and 1 segment was maintained without distention. The influence of distention-decompression on vascular resistance was calculated. Mucosal permeability was evaluated by measuring the clearance of albumin from blood to lumen. After distention and decompression, tissue specimens were collected for histomorphologic evaluation. In addition, the contractile response of the circular smooth muscle layer was determined following incubation with 3 prokinetic agents.

Results—Intestinal vascular resistance increased during intraluminal distention and returned to baseline values after decompression. Albumin clearance rate increased after distention, compared with baseline and control values. Histologic examination of the distended segments revealed grade-1 and -2 lesions of the mucosal villus. Edema and hemorrhage were evident in the submucosa and muscular layers. Mesothelial cell loss, edema, and hemorrhage were also evident in the serosa. Mucosal surface area and villus tip height decreased and submucosal volume increased in the distended tissue. Compared with responses in control specimens, distention decreased the contractile response induced by cisapride, erythromycin, and metoclopramide.

Conclusions and Clinical Relevance—Intraluminal distention of the jejunum followed by decompression increased mucosal permeability and injury and decreased responses to prokinetic agents. Horses with intraluminal intestinal distention may have a decreased response to prokinetic agents. (Am J Vet Res 2002;63:267–275)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe the ultrasonographic and quantitative histologic effect of injecting 2% iodine in almond oil (IAO) and ethanolamine oleate (EO) in the medial and middle patellar ligaments of horses and to determine whether a difference in response exists between IAO and EO treatment.

Animals—10 healthy horses.

Procedure—In 5 horses, the medial and middle patellar ligaments of 1 limb were injected with EO, whereas IAO was injected in the medial and middle patellar ligaments of another 5 horses. Ultrasonographic evaluation was performed on the experimental and control limb before injection of IAO and EO and prior to euthanasia to determine cross-sectional area and evaluate fiber pattern. The patellar ligaments were harvested 2 weeks after injection and examined histologically to evaluate the inflammatory response, fibroplasia, and chondroid metaplasia.

Results—Injection of the patellar ligaments with IAO resulted in a greater increase in cross-sectional area on ultrasonography than EO. Both agents caused a decrease in echogenicity of the ligament. Histologically, significantly greater infiltration of inflammatory cells and fibroplasia developed after injection with IAO, compared with EO. Both agents resulted in significantly greater fibroplasia relative to control specimens.

Conclusions and Clinical Relevance—Injection of the medial and middle patellar ligaments with IAO induces more severe inflammation and fibroplasia than EO. Maturation of the inflammatory and fibrous response may contribute to resolution or attenuation of upward fixation of the patella by subsequent stiffening of the ligaments. (Am J Vet Res 2002;63:738–743)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the efficacy of a customized solution to attenuate intestinal injury following 20% low-flow ischemia and reperfusion in the jejunum of horses.

Animals—10 healthy adult horses.

Procedure—Two 30.5-cm-long segments of jejunum were exteriorized through a ventral midline incision and the mesenteric artery and vein supplying that portion of the intestine were instrumented with flow probes. Blood flow was decreased to 20% of baseline for 90 minutes followed by 90 minutes of reperfusion. In 5 horses, 60 mL of the customized solution was placed in the lumen of each segment (treatment-group horses), and 60 mL of lactated Ringer's solution was placed in the lumen of 5 additional horses (control-group horses). Biopsy specimens were obtained from 1 segment in both groups for histologic evaluation. Aliquots of luminal fluid were obtained from the other segment in both groups for determination of albumin concentrations as an index of mucosal permeability.

Results—Compared with control-group horses, treatment-group horses had a significant decrease in luminal albumin concentration following reperfusion. Although differences in mucosal grades were not significantly different between control- and treatment-group horses, treatment-group horses had significantly greater jejunal villous length and area, compared with that of control-group horses.

Conclusions and Clinical Relevance—Intraluminal administration of the customized solution in the jejunum, compared with lactated Ringer's solution, results in an improvement in histologic findings and mucosal translocation of albumin in horses with mild intestinal injury. (Am J Vet Res 2004;65:485–490)

Full access
in American Journal of Veterinary Research