Contribuição do contraste negativo na artrografia tomográfica do joelho normal de cães / Contribution of negative contrast in computed tomography arthrography of the normal canine stifle

A ruptura do ligamento cruzado cranial é uma das causas mais comuns de claudicação do membro pélvico de cães. A radiografia e a ultrassonografia são métodos de diagnóstico frequentemente utilizados na rotina clínica de pequenos animais, porém a tomografia computadorizada é uma modalidade de imagem ainda pouco estudada para avaliar a articulação do joelho de cães. O presente trabalho teve por objetivo avaliar a contribuição do contraste negativo na artrografia tomográfica do joelho normal de cães, para visibilizar as estruturas intra-articulares e padronizar o uso desse contraste na articulação. Foram utilizados 24 membros pélvicos de cães de raças variadas, selecionados pela ausência de histórico de doença articular prévia do joelho e por apresentarem exames radiográficos, ultrassonográficos e macroscópicos normais. O experimento foi delineado em dois grupos, sendo o grupo I constituído de animais com peso até 20 kg e grupo II acima de 20 kg. Foram feitos cortes tomográficos com o membro flexionado e estendido. A quantidade média de ar empregada para a distensão da cápsula articular foi de 49 ml para o Grupo I e de 81 ml para o Grupo II. Utilizou-se um tubo de látex na porção distal à articulação do joelho para reduzir o escape de ar pelo tendão extensor digital profundo, que possui comunicação intra-articular. Foi possível visibilizar pela imagem tomográfica, em todas as articulações, as seguintes estruturas: ligamento cruzado cranial e caudal, meniscos medial e lateral, ligamento patelar, ligamentos colaterais e cápsula articular. Desta forma, o contraste negativo se mostrou uma alternativa eficaz para auxiliar a identificação das estruturas anatômicas do joelho na artrografia tomográfica.

The cranial cruciate ligament rupture is one of the most common causes of canine hind limb lameness. The radiographic and ultrasonographic are methods of diagnosis frequently used in small animal clinics, but there are few studies of computed tomography to exam the stifle joint in dogs. The aim of this study was to evaluate the contribution of negative contrast in computed tomography arthrography of the normal stifle of dogs for the visualization of intra-joint structures, and to standardize the use of contrast in this joint. Twenty-four hind limbs from dogs of several breeds were used. They were selected based on history of absence of previous stifle joint disease and normal radiographic, ultrasonographic and macroscopic exams. The experiment was designed in two groups: Group I animals weighing up to 20 kg, and Group II animals weighing above 20 kg. Tomographic sections were done with the limb flexed and extended. The amount of air used for the joint capsule distension was approximately 49 ml for group I and 81 ml for group II. A latex tube was used on the distal portion of the stifle to reduce air escaping through the long digital extensor tendon, which has intra-joint communication. In all joints, the tomographic image allowed the visualization of the following structures: cranial and caudal cruciate ligament, medial and lateral menisci, patellar ligament, medial and lateral collateral ligament and joint capsule. Thus, the negative contrast (air) showed to be an effective alternative in the evaluation of the stifle anatomical structures by using tomography arthrography.

An innovative technique for displaying three dimensional radiographic anatomy of synovial structures in the equine distal limb.

Radiography is the most commonly applied imaging modality in equine practice and forms an essential part of the diagnostic work-up of lame horses. Radiographic signs of musculoskeletal pathology are frequently localized at sites of soft tissue attachment, which are often not clearly visible on radiographs. Different lesions carry different prognoses and require a variety of treatments, and a good knowledge of the position of the synovial structures in the distal limb of the horse is essential for practitioners in the interpretation of radiographs. This study describes a new technique for creating three-dimensional (3D) models of the synovial structures and superimposing them onto radiographs for the purpose of teaching radiographic anatomy. A set of standard radiographs was acquired of the metacarpophalangeal and the distal interphalangeal joints of a fresh cadaver leg while the leg was positioned in a material-testing machine to mimic the weight-bearing horse. Computed tomography of the same regions was performed after injection of negative contrast medium into the joints. 3D reconstructions of the joints were created using grayscale thresholding and polynomial surface meshing in Mimics. The resulting 3D reconstructions were superimposed on top of the radiographs using Adobe Photoshop CS3 Extended, thus allowing the visualization of the joint anatomy in relation to the bone on all projections. The main advantage of this technique is that it allows synovial structures to be visualized on radiographs where they are normally indistinct, which will serve as a teaching aid for anatomy.

Clinical utility of pneumogastrography in dogs.

Pneumogastrography utilizes negative contrast media such as air or carbonated beverages to improve visualization of luminal contents and mucosal surfaces within the stomach. Pneumogastrography as a diagnostic technique in cases of gastric disease has not been widely described in the veterinary literature and is a procedure that may yield additional information not obtained from survey radiographs. This technique is useful in the diagnosis of luminal and mucosal gastric diseases. In this article, the pneumogastrography technique and relevant literature are reviewed. Six case examples are included that demonstrate the utility of pneumogastrography in dogs with gastric disease.

Urocystolith detection: comparison of survey, contrast radiographic and ultrasonographic techniques in an in vitro bladder phantom.

Urocystoliths of 9 mineral types from 437 canine patients submitted to the University of Minnesota Urolith Bank were imaged in a urinary bladder phantom. Imaging techniques simulated were survey radiography, pneumocystography, double contrast cystography (two iodine concentrations) and real-time ultrasonography (3.5 MHz, 5.0 MHz, 7.5 MHz). Imaging techniques were compared for accuracy of urocystolith detection, accuracy of urocystolith enumeration, and tendencies for over or undercounting. Across urocystolith mineral types, the false negative rates (no urocystoliths detected in a given case) for survey radiographs range from 2 to 27%. Pneumocystographic techniques are one-half as likely to yield false negative results as are survey radiographic techniques. Underestimates of urocystolith numbers and false negatives are likely using 80 mg iodine/ml double contrast cystography because calcium-based urocystoliths are isopaque in this contrast medium dilution. The 200 mg iodine/ml double contrast cystographic techniques are unlikely to yield false negative diagnoses even for very small (< or = 1.0 mm) urocystoliths and is comparable to pneumocystography for detection and slightly better for enumeration. The likelihood of an ultrasonographic false negative for urocystoliths decreases with increasing MHz. Under optimal conditions using a 7.5 MHz mechanical sector transducer, the false negative rates were comparable to double contrast cystography, but rates increased notably with lower MHz transducers.

Hemodynamics of progressive pneumopericardium in the dog.

The hemodynamics of progressive pneumopericardium were studied in 6 anesthetized healthy dogs (with intact thorax). Heart rate, cardiac output, and pericardial and intravascular pressures were recorded. Pressures were measured in the pericardial space by means of a percutaneously introduced, air-filled catheter, and in the right atrium, right ventricle, left atrium, left ventricle, pulmonary artery, and aorta by means of fluid-filled catheters. The gradual increase in mean pericardial pressure up to 11 +/- 2 mm of Hg was associated with increases in heart rate and mean right atrial, mean left atrial, right ventricular end-diastolic, and left ventricular end-diastolic pressures and with decreases in cardiac output and stroke volume, with no change in left ventricular systolic and mean aortic pressures. Critical cardiac tamponade occurred at a pericardial pressure of 12.2 +/- 2.8 mm of Hg, which was produced by 8.7 +/- 1.9 cm3 air/kg of body weight. This was characterized by a sudden marked decrease in heart rate, cardiac output, stroke volume, left ventricular systolic pressure, and mean aortic pressure, and equilibration of mean right atrial, mean left atrial, right ventricular end-diastolic, left ventricular end-diastolic, and pulmonary artery diastolic pressures. These hemodynamic changes were similar to those of experimental pericardial effusion.