The Biomechanical Properties of Meshed versus Perforated Acellular Dermal Matrices (ADMs).

Acellular dermal matrices (ADMs) are used for soft tissue augmentation across surgical specialties. Since allograft incorporation depends on direct opposition between the ADM and a vascular bed, seroma formation can be detrimental to incorporation. Since most ADM products are available in many meshed and perforated forms, there is a lack of consistency between manufacture designs. We set out to determine the fluid egress properties and increase in surface area resulting from common cut patterns. METHODS: Three ADM cut patterns were studied: 1 meshed and 2 perforated. We calculated the surface area of these modified ADM samples. Fluid was passed through each ADM, and time required for fluid passage was recorded. An ANOVA (P < 0.05) was used to determine if there was a significant difference in egress properties across the 3 patterns. RESULTS: Meshing in a 1:1 pattern resulted in a 97.50% increase in surface area compared with the uncut product. In comparison, only a 0.30% increase resulted from Perforation Pattern #1 and a 0.59% increase resulted from Perforation Pattern #2. There was a significant difference in egress properties across the three cut patterns (P = 0.000). The average egress time of Mesh Pattern #1 was 1.974 seconds. The average egress time of Perforation Pattern #2 was 6.504 seconds, and of Perforation Pattern #1 was 10.369 seconds. CONCLUSIONS: Quantitative comparison revealed that meshing ADM significantly improves fluid egress and increases the surface area. Therefore, the use of meshed ADM tissue could improve the incorporation of ADM with the recipient, with improved patient outcomes.

Aventriculi associated with holoprosencephaly in a dog.

CASE DESCRIPTION: A 10-month-old neutered male mixed breed dog was presented for assessment of poorly controlled seizures. CLINICAL FINDINGS: Magnetic resonance imaging of the brain disclosed complete absence of the lateral and third ventricles and mesencephalic aqueduct. Postmortem computed tomographic (CT) imaging and positive contrast cisterno-ventriculography confirmed the lack of a contiguous ventricular system. However, histopathology identified the presence of vestigial lateral and third ventricles with hypoplastic choroid plexus, atresia of the third ventricle, and fused thalami, consistent with a diagnosis of lobar holoprosencephaly (HPE). CLINICAL RELEVANCE: To our knowledge, this report is the first case of radiographically confirmed aventriculi associated with HPE, a rare congenital malformation previously reported in people, to be described in veterinary medicine.

Use of radiographic measurements to diagnose stage B2 preclinical myxomatous mitral valve disease in dogs.

OBJECTIVE: To investigate the usefulness of radiographic measures of the left atrium and ventricle as surrogates for echocardiographic criteria in identifying dogs with stage B2 preclinical myxomatous mitral valve disease (MMVD). ANIMALS: 56 client-owned dogs with preclinical mitral regurgitation attributed to MMVD examined between April 19, 2016, and November 22, 2017. PROCEDURES: Medical records were retrospectively searched, and data collected included age, body weight, heart murmur grade, and echocardiographic and radiographic measurements. Dogs were grouped according to whether they did (case dogs) or did not (control dogs) meet echocardiographic criteria used to identify dogs with stage B2 MMVD. Measurements for lateral thoracic radiographic variables normalized to vertebral body units (VBUs) were obtained, and results were analyzed to identify variables that could best discriminate between case and control dogs. RESULTS: Three radiographic variables of left atrial size (vertebral left atrial size [VLAS], left atrial width, and the combined variable of VLAS + left atrial width) most accurately distinguished control dogs from case dogs, and the VLAS was the simplest and fastest to perform in a clinical setting. The optimal cutoff for VLAS was 2.5 VBUs (sensitivity, 70%; specificity, 84%; and likelihood ratio, 4.38), with VLAS ≥ 2.5 VBUs for case dogs. The maximum specificity cutoff for VLAS was 3.0 VBUs (sensitivity, 40%; specificity, 96%; and likelihood ratio, 10.0), with VLAS ≥ 3.0 VBUs for case dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that when echocardiography is unavailable, radiographic VLAS ≥ 3 VBUs could be used with minimal risk of false-positive diagnosis of stage B2 MMVD in dogs.

Placement of a balloon for resuscitative endovascular balloon occlusion of the aorta without fluoroscopic guidance in canine cadavers.

OBJECTIVE: To determine whether a balloon for resuscitative endovascular balloon occlusion of the aorta (REBOA) could be accurately placed in the descending aorta between the left subclavian and celiac arteries (zone I) by using external anatomic landmarks in dogs. STUDY DESIGN: Cadaver study. SAMPLE POPULATION: Fifteen canine cadavers of 3 weight categories (10-20, 20-30, and ≥ 30 kg). METHODS: Percutaneous catheterization of the femoral artery was attempted under ultrasonographic guidance; when unsuccessful, an arterial cutdown was performed to place an introducer sheath. Distance was measured between the introducer sheath and the target region, located ventral to the epaxial muscles at the level of the 12th thoracic vertebra. The balloon was advanced the measured distance, and placement was confirmed with fluoroscopy. The volume of iohexol solution required to inflate balloons was recorded. Histopathology was performed on the aortas of the first 5 dogs. RESULTS: Three catheters were placed under ultrasonographic guidance. Balloons were successfully placed into zone I in 15 of 15 cadavers. Balloons were inflated with a median 0.4 mL/kg (range, 0.21-0.67) of iohexol solution. Minor changes were identified in 2 of 5 dogs examined with histopathology (linear defects in 1 dog, small focal dissection in the other). CONCLUSION: A balloon for REBOA was consistently placed in the target zone I without fluoroscopic guidance. CLINICAL SIGNIFICANCE: Fluoroscopy may not be required for zone I REBOA in dogs. Additional studies are warranted to evaluate the feasibility of REBOA in clinical dogs with hemoperitoneum.

ACCURACY OF RADIOGRAPHIC DETECTION OF THE CRANIAL MARGIN OF THE DORSAL LAMINA OF THE CANINE SACRUM.

An elongated sacral lamina has been described as one of the contributing factors for dogs with cauda equina syndrome due to degenerative lumbosacral stenosis (DLSS); however, published evidence is lacking on the accuracy of radiographic screening for the presence of this lesion. Objectives of this prospective, cross-sectional cadaver study were to describe the accuracy and repeatability of detection of the cranial sacral lamina margin on plain lateral radiographs of the lumbosacral junction in dogs. Twenty-five medium and large breed canine cadavers were radiographed before and after placement of a radiopaque hook in the cranial margin of the sacral lamina. Three independent evaluators placed digital markers at the perceived margin on preinterventional radiographs. The distance from perceived location to the true location on postinterventional radiographs was recorded for each dog and observer. A discordance threshold (distance between perceived and actual margin) of 1.5 mm was subjectively defined as clinically relevant. The three evaluators demonstrated good repeatability, although the accuracy for margin detection was only fair (mean discordance 1.7 mm). Evaluators demonstrated greater accuracy in identifying the landmark in juveniles (1.4 mm) vs. adults (1.8 mm; P < 0.01). Results of this study indicated that observer repeatability is good and accuracy is fair for correctly identifying the radiographic cranial margin of the sacral lamina in dogs. This should be taken into consideration when interpreting elongation of the sacral lamina in radiographs of dogs with suspected DLSS, especially adults.

Multilocus analyses of admixture and introgression among hybridizing Heliconius butterflies.

Introgressive hybridization is an important evolutionary process and new analytical methods provide substantial power to detect and quantify it. In this study we use variation in the frequency of 657 AFLP fragments and DNA sequence variation from 15 genes to measure the extent of admixture and the direction of interspecific gene flow among three Heliconius butterfly species that diverged recently as a result of natural selection for Miillerian mimicry, and which continue to hybridize. Bayesian clustering based on AFLP genotypes correctly delineated the three species and identified four H. cydno, three H. pachinus, and three H. melpomene individuals that were of mixed ancestry. Gene genealogies revealed substantial shared DNA sequence variation among all three species and coalescent simulations based on the Isolation with Migration (IM) model pointed to interspecific gene flow as its cause. The IM simulations further indicated that interspecific gene flow was significantly asymmetrical, with greater gene flow from H. pachinus into H. cydno (2Nm = 4.326) than the reverse (2Nm = 0.502), and unidirectional gene flow from H. cydno and H. pachinus into H. melpomene (2Nm = 0.294 and 0.252, respectively). These asymmetries are in the directions expected based on the genetics of wing patterning and the probability that hybrids of various phenotypes will survive and reproduce in different mimetic environments. This empirical demonstration of extensive interspecific gene flow is in contrast to a previous study which found little evidence of gene flow between another pair of hybridizing Heliconius species, H. himera and H. erato, and it highlights the critical role of natural selection in maintaining species diversity. Furthermore, these results lend support to the hypotheses that phenotypic diversification in the genus Heliconius has been fueled by introgressive hybridization and that reinforcement has driven the evolution of assortative mate preferences.