Objective-To characterize and quantitatively assess the typical pulmonary anatomy of healthy adult alpacas with multidetector row CT. Animals-10 clinically normal adult female alpacas. Procedures-CT examination of the thorax was performed before and after IV administration of iodinated contrast medium in sedated alpacas in sternal recumbency. Measurements of the trachea, bronchi and related blood vessels, and selected vertebrae as well as the extent and density of lung parenchyma were performed with a Digital Imaging and Communications in Medicine (DICOM) viewer. Morphometric and quantitative data were summarized. Results-Separation of individual lung lobes could not be identified, except for the accessory lung lobe. In all alpacas, both lungs extended farther caudally at the medial aspect than at the lateral aspect. The right lung extended farther in both cranial and caudal directions than did the left lung. The branching pattern of the bronchial tree varied only slightly among alpacas and consisted of 1 cranial bronchus and 3 caudal bronchi bilaterally, with a right accessory bronchus. Luminal diameters of first-generation bronchi ranged from 3 to 9 mm. Mean +/- SD parenchymal lung density was −869 +/- 40 Hounsfield units (HU) before contrast injection and −825 +/- 51 HU after contrast injection. Mean difference in diameter between bronchi and associated arteries or veins was 0.8 +/- 0.9 mm. Conclusions and Clinical Relevance-Knowledge of the typical anatomy of the lungs and bronchial tree in healthy alpacas as determined via CT will aid veterinarians in clinical assessment and bronchoscopic evaluation of alpacas.

Objective: To determine between-pony and within-pony variations and interobserver and intraobserver agreements of a technique for measurement of flow-mediated vasodilation (FMD) in healthy ponies Animals: 6 healthy pony mares (weight range, 236 to 406 kg; body condition score range, 3/9 to 7/9; age range, 14 to 25 years). Procedures: In each pony, the left median artery was occluded with a blood pressure cuff (inflated to > 300 mm Hg for 5 minutes). Two-dimensional ultrasonographic images of the artery were recorded for 30 seconds before cuff inflation and for 2 minutes after cuff deflation. Maximum luminal diameters of arteries were compared with their baseline diameters to calculate FMD (relative percentage increase in luminal size). Images were obtained from 6 ponies 1 time and from 1 pony 6 times. Independent analysis of images was performed by 2 investigators, 1 of whom analyzed images on 2 occasions. Results: Mean ± SD FMD in 6 ponies (1 time) was 12.57 ± 4.28% and in 1 pony (6 times) was 7.30 ± 2.11%. Between-pony and within-pony coefficients of variation were 34.09% and 28.84%, respectively. Interobserver agreement was fair (intraclass correlation coefficient, 0.47); intraobserver agreement was poor (intraclass correlation coefficient, 0.30). Conclusions and Clinical Relevance: FMD was identified and measured in ponies. Measurement of FMD is used to assess endothelial function in humans and has been investigated in dogs. Measurement of FMD in ponies appeared to be feasible and could be used to assess endothelial function (to determine predisposition for development of laminitis or cardiovascular diseases).

The blood supply to the proximal sesamoid bone of the equine forelimb was examined in 18 cadaver limbs from adult horses, using x-ray computed tomography and a tissue-clearing (Spalteholz) technique. Results of the study indicated that the proximal sesamoid bones were supplied by multiple branches of the medial and lateral palmar digital arteries, which entered the proximal half of the bones on their nonarticular, abaxial surface. After entering the bone, the vessels traverse dorsally, axially, and distally, arborizing into several smaller branches that appear to supply the entire bone. The major branches of these vessels reside in bony canals, the orientation and distribution of which parallel the radiographic lucencies seen in horses with sesamoiditis and correspond to the configuration of apical fracture patterns.

Objective--To test the hypothesis that endothelium-derived nitric oxide modulates vasomotor reactivity in equine digital arteries. Design--Digital arteries were isolated from adult horses, and their vasodilator properties were examined in an in vitro controlled environment. Animals--Five adult horses (1 gelding, 4 mares) without evidence of hoof or vascular disease were studied. Procedure--Arterial rings with or without endothelium were exposed to endothelium-dependent vasodilator drugs in the presence or absence of a pharmacologic inhibitor of the enzyme nitric oxide synthase. Results--Vasodilator effects of 3 endothelium-dependent vasorelaxant agents were significantly greater in endothelium-intact vessels than in endothelium-denuded vessels. Moreover a nitric oxide synthase inhibitor reduced vasodilator responses to endothelium-dependent vasodilators in endothelium-intact arteries, but had no discernable effects in endothelium-denuded arteries. Conclusions--These findings indicate the presence of endothelium-derived relaxing factor/nitric oxide in blood vessels of horses, and identify vascular endothelium as an endogenous modulator of vasomotor tone in the digital arteries of this species.

To determine blood supply in the area, dye or radioopaque contrast material was injected into the named arteries supplying the terminal colon and rectum in 10 dogs. The cranial rectal artery appeared to supply most of the blood to the terminal colon and rectum. The middle and caudal rectal arteries supplied variable and relatively insignificant amounts. The intrapelvic rectum had a less adequate blood supply than did the terminal colon or proximal rectum. A ventral midline laparotomy and pubic osteotomy were performed in an additional 11 dogs to provide access to the terminal colon and rectum. When the cranial rectal artery was ligated and the colorectal junction was transected and anastomosed, the intrapelvic rectum developed marked congestion, edema, and discoloration. Rectal fluorescence, after IV administration of fluorescein, was either poor or absent. Histologically, partial- to full-thickness mucosal necrosis was evident in most tissue specimens taken from the rectum, and muscle necrosis was evident in some. These findings suggest that, in dogs, the cranial rectal artery should be preserved if at all possible and, if the cranial rectal artery is ligated, most of the intrapelvic rectum should be resected to ensure adequate blood supply to the anastomosis.

Vascular patterns to thoracic limbs, thorax, and neck muscles were studied in 10 dogs (20 limbs) to identify muscles most suitable for transposition in the treatment of large wounds. Gross dissection of injected specimens and angiography were used to identify vascular pedicles. Size and location of pedicles were generally consistent, and any variations would not interfere with most muscle transfers. The cutaneous trunci, latissimus dorsi, sternothyroideus, sternohyoideus, deep pectoral, anconeus, ulnaris lateralis, and ulnar head of flexor carpi ulnaris muscles were identified as suitable for transfer. The cranial trapezius, caudal omotransversarius, cleidobrachialis, and caudal sternocephalicus muscles also had potential for use. Other muscles, because of inaccessibility or unfavorable vascular pattern, were not suitable candidates for transfer.

Cutaneous arterial blood supply to the tail was evaluated in 12 dogs. Subtraction radiography of internal iliac artery and distal aorta angiography in 3 of these dogs was used to determine arterial blood supply to the tail from the median sacral and lateral caudal arteries. Dissection of the tail in 8 canine cadavers revealed bilateral subcutaneous location of lateral caudal arteries following tail amputation. An axial pattern flap based on the lateral caudal arteries contributed to the reconstruction of a large caudodorsal cutaneous defect in a dog. An axial pattern flap based on the lateral caudal arteries following tail amputation may be indicated to aid reconstruction of large caudodorsal cutaneous defects of the trunk in dogs.

We developed a single-pedicle, axial pattern tubed skin flap that could be transferred to an in vitro perfusion apparatus. On the basis of results of prosections, angiography, contact radiography, and surviving-length studies, it was concluded that a single-pedicle, axial pattern skin flap measuring 4 cm X 12 cm incorporating the caudal superficial epigastric artery would survive to its entire length. Subsequently, a surgical (stage 1) procedure was developed for the routine preparation of single-pedicle, axial pattern tubed skin flaps. Healing after the stage-1 procedure was evaluated by visual inspection and fluorescein angiography. Stage-1 procedures were performed successfully 149 of 160 (93%) times. A second surgical (stage 2) procedure was developed for routine cannulation of the caudal superficial epigastric artery and harvest of the tubed skin flap. Stage-2 procedures were performed successfully 136 of 144 (94%) times.

The microvascular circulation of the cecum was studied in 15 adult horses, using microangiography and light microscopy combined with gross studies and scanning electron microscopy of vascular replicas. After heparinization, the horses were euthanatized and the cecum was transected at the cecocolic junction. Blood was flushed free of the circulation with isotonic NaCl and the cecal lumen was slightly distended. In 6 horses, the vascular system was injected with a modified radiopaque medium and evaluated radiographically. Sections evaluated radiographically were also prepared for histologic examination by standard methods. Eight horses were injected with 1 of 2 types of plastics and studied grossly or by scanning electron microscopy. In 1 additional horse, the lateral and medial arteries were injected with different colored plastic for gross studies. The lateral and medial cecal arteries appear to supply the respective areas of the cecum with minimal mixing of the 2 circulations. The major vascular supply to the cecal apex appeared to be through the medial cecal artery. Both the lateral and medial cecal arteries gave rise to cecal retia, which formed a mesh-like network around the respective veins. Vessels from these retia supplied the cecal tissue and the cecal lymph nodes. The continuation of the retia was through long terminal arteries that coursed around the circumference in the submucosa, forming an extensive submucosal plexus. This plexus supplied both the mucosa, and the tunica muscularis and serosa. Vessels within the longitudinal and circular muscle layers of the muscularis externa ran parallel to the muscle fibers, and consequently, perpendicular to each other. Arteries supplying the mucosa branched into a capillary network as they penetrated the muscularis mucosa at the base of the cecal glands. These capillary networks anastomosed with the networks around adjacent glands at the luminal surface, forming a honeycomb-like pattern. Drainage was facilitated by more sparsely distributed venules that united with venules from adjacent areas and descended to the submucosal veins. These veins were characterized by regular helical smooth muscle constrictions.