COMPUTED TOMOGRAPHY OF THE LLAMA HEAD: TECHNIQUE AND NORMAL ANATOMY

Computed tomography was performed on the head of 6 normal adult llamas. The animals were under general anesthesia and positioned in dorsal recumbency on the scanning table. The area scanned was from the external occipital protuberance to the rostral portion of the nasal passage, and the images are presented in both a bone window and a soft tissue window to allow evaluation and identification of the anatomy of the head. Computed tomography of the llama head can be accomplished by most computed tomography scanners utilizing a technique similar to that used in small animals with minor modification of the scanning table.     

COMPUTED TOMOGRAPHY OF THE NORMAL LUMBOSACRAL INTER VERTEBRAL DISC IN 22 DOGS

Computed tomography of the lumbosacral spine was performed on 22 purpose-bred, medium-sized hound dogs between 1 and 6 years of age. Images were evaluated to determine the degree of disc bulge. All dogs were neurologically normal. Dogs were imaged in dorsal recumbency with the pelvic limbs variably extended. Sagittal reconstructions were made from transverse images. The mean (+/-SD) width of the mid-portion of the L7-S1 intervertebral disc was 0.5 +/- 0.07 cm (range 0.33-0.62 cm). All L7-S1 intervertebral discs were dorsally convex, with the mean bulge measuring 0.25 +/- 0.07 cm (range 0.17-0.50 cm). The height of the vertebral canal at L7-S1 was 0.91 +/- 0.11 cm (range 0.68-1.15 cm). The mean percentage of the vertebral canal occupied by the bulge was 26.89 +/- 5.05% (range 20.74-43.08%). Mild bulging of the L7-S1 intervertebral disc can be present without associated neuropathy in medium-sized dogs.     

A RETROSPECTIVE ANALYSIS OF 140 DOGS WITH ORAL MELANOMA TREATED WITH EXTERNAL BEAM RADIATION

Despite the early notion that canine oral malignant melanoma is radioresistant, recent data suggest that external beam radiotherapy is effective in local tumor control. However, optimal fractionation schedules have not been established. The high rate of regional and distant metastasis is another problem that has hindered long-term control. The role of chemotherapy in the management of canine oral melanoma has also not been determined. In this study, data from 140 dogs irradiated at North Carolina State University were evaluated with the following objectives: (1) to compare the efficacy of three radiation therapy protocols (36 Gy, 9 Gy x 4 fractions; 30 Gy, 10 Gy x 3 fractions; or >45 Gy, 2-4 Gy x 12-19 fractions) for the treatment of dogs with oral malignant melanoma, (2) to identify any host or tumor factors influencing prognosis, and (3) to determine the impact of systemic chemotherapy on treatment outcome. Information regarding response to therapy, disease progression, and survival were determined from the medical records or from information obtained by telephone or mail survey. Relationships between host, tumor, and treatment variables and outcome measures (response, time to first event, and survival) were evaluated using Fisher's exact test (response) and the Cox regression model (time to first event and survival). The median time to first event for the 140 dogs was 5.0 months (95% C.I., 4-6 months) and the median survival was 7.0 months (95% C.I., 6-9 months). In the univariate analysis, the following variables were associated with increased time to first event and survival: (1) rostral tumor sublocation; (2) lack of bone lysis observed on skull imaging, and (3) microscopic tumor burden. In a multivariate analysis of 111 dogs with complete data for these variables, tumor sublocation, bone lysis, and tumor volume were identified as joint predictors of time to first event (p < .001, p < .001, and p = .04, respectively) and survival (p < .001, p < .001, and p = .05, respectively). There were no differences in response, time to first event and survival between the three radiation therapy protocols used. Systemic chemotherapy had no impact on the development of metastatic disease, time to first event, or survival, although the dosages used in this study were suboptimal. External beam radiation therapy is effective in local disease control of canine oral malignant melanoma; however, the optimal fractionation scheme has yet to be determined. The high metastatic rate observed with this disease and the inefficacy of systemic chemotherapy indicate that further investigation into novel therapies is warranted.     

CHANGES IN ULTRASONOGRAPHIC APPEARANCE OF ADRENAL GLANDS IN DOGS WITH PITUITARY-DEPENDENT HYPERADRENOCORTICISM TREATED WITH TRILOSTANE

Trilostane, a 3beta-hydroxysteroid dehydrogenase inhibitor, has been used successfully over the last few years for the treatment of canine pituitary-dependent hyperadrenocorticism. In a prospective study of 19 dogs with pituitary-dependent hyperadrenocorticism, the adrenal glands were measured before and at least 6 months after initiation of trilostane therapy. Right adrenal gland length and caudal pole thickness and left adrenal gland caudal pole thickness increased significantly (p < or = 0.05); there was no significant change in left adrenal gland length. Enlargement of adrenal glands during trilostane therapy may occur as a result of suppression of the negative feedback mechanism affecting cortisol production.     

ENDOSCOPIC ULTRASOUND INSTRUMENTATION, APPLICATIONS IN HUMANS, AND POTENTIAL VETERINARY APPLICATIONS

Endoluminal scanning under endoscopic guidance, or endoscopic ultrasonography (EUS), has become the most significant advance for imaging the gastrointestinal (GI) tract wall and contiguous organs in the past 20 years. It was originally designed to overcome the limitations in humans to imaging the abdominal organs transabdominally, such as large penetration depths and GI air. This imaging modality provides detailed images of pathological processes both within and outside of the GI wall since a high-frequency transducer can be brought into close proximity with the target regions. It has found most success in humans for the staging of lung, gastric, and esophageal cancer, the detection of both lymphatic and hepatic metastases, and diagnosis of pancreatitis and pancreatic cancer, as well as achieving an important role in interventional and therapeutic procedures. The EUS examination can be performed to examine both the thorax and abdomen in animals when both conventional transthoracic or transabdominal ultrasound are inadequate due to intervening air, bone, large penetration depths, or obesity. The echoendoscope is similar to a conventional endoscope but has an ultrasound transducer at its tip. Both radial and linear multifrequency scanners are available. Linear scanners allow fine-needle aspiration (FNA) of the bowel wall or extraluminal structures. Transducer coupling is either by direct mucosal contact or by inflation of a water-filled balloon surrounding the transducer. Current thoracic applications for EUS in veterinary medicine include examination of the mediastinum, bronchial lymph nodes, esophagus, and pulmonary lesions as well as FNA of pulmonary masses. Abdominal applications include examination of both pancreatic limbs and the liver, including portosystemic shunts, detection of lymphadenomegaly, and examination of the gastric wall, duodenum, and jejunum. Other potential applications in dogs and cats include tumor staging and intrapelvic ultrasound.     

Effect of Intestinal Resection on Two Juvenile Horses With Granulomatous Enteritis

Two horses were presented with lethargy, weight loss, anorexia, and swelling of the limbs and ventral body wall. One horse, a 12-month-old American Paso Fino colt, also had acute abdominal pain. The other horse, a seven-month-old Tennessee Walking Horse (TWH) filly passed diarrheic stools during the initial examination. Each horse had low serum protein, neutropenia, and a normal packed cell volume (3.2 g/dl, 1300 cells/ul, and 38%, respectively, for the colt, and 2.4 g/dl, 696 cells/ul, and 44%, respectively for the filly). After intravenously administering plasma, the colt's PCV dropped to 23%, and the filly's dropped to 30%. During exploratory surgery, 3.5 and 2.0 meters of thickened terminal small intestine were removed from the colt and filly respectively, and a jejunocecostomy performed. The results of histologic examination of resected intestine were consistent with a diagnosis of equine granulomatous enteritis (EGE). Both horses showed clinical improvement within two days after surgery. The colt developed a neutrophilia (20,500 cells/ul) within 24 hours of surgery. Serum protein concentrations remained stable and gradually elevated to normal or near normal values of 7.0 g/dl (colt) and 5.8 g/dl (filly) by two weeks. The colt was killed four months after surgery because of signs of abdominal pain. Postmortem examination revealed a small intestinal volvulus associated with an adhesion. The TWH filly remains clinically normal 13 months after surgery.     

Effects of Carbon Dioxide Insufflation Combined With Changes in Body Position on Blood Gas and Acid-Base Status in Anesthetized Llamas (Llama glama)

Objective— To study the combined effects of intra-abdominal CO₂ insufflation with changes in body position during laparoscopy in xylazine-ketamine-halothane anesthetized llamas. Study Design— Prospective, controlled study. Animals— Nine castrated, male llamas weighing 114 ± 23 kg, 3 to 13 years old. Methods— Three llamas (preliminary study [PS] group) were used to study the effect of right lateral, dorsal, and left lateral recumbency on gas exchange and acid-base status. The other six (experimental study [ES] group) were used to study the combined effects of changes in body position and CO₂ insufflation to an intraabdominal pressure of 10 to 12 mm Hg. Heart rate, respiratory rate, and indirect arterial blood pressures (systolic [SAP], mean [MAP], and diastolic [DAP]) were recorded every 5 minutes during anesthesia. Arterial blood gases (PaO₂ and PaCO₂) and acid-base status (pHa and HCO₃) were measured immediately after induction of anesthesia and before each change of position. Results— In the PS group, significant decreases in SAP, MAP and PaCO₂ and increases in PaO₂ and pHa were observed when the llamas were turned from right lateral to dorsal recumbency. Values for HCO_-3 were lower than the postinduction values, but they remained unaffected by the changes in position. In the ES group, values for MAP were significantly lower when the llamas were placed in dorsal and left lateral recumbency than those observed during right lateral recumbency. Arterial O₂ tension during right lateral recumbency was lower but returned to preinsufflation values when the llamas were placed in the dorsal position. All llamas recovered uneventfully within 30 minutes after termination of anesthesia. Conclusions— Insufflation of CO₂ and changing body position induce minor and transient changes in cardiovascular and respiratory function. Clinical Relevance— Laparoscopy with mild intra-abdominal CO₂ insufflation (10 to 12 mm Hg) can be used safely in spontaneously breathing llamas anesthetized with xylazine, ketamine, and halothane.     

Intra-Articular Replacement of Bovine Cranial Cruciate Ligaments with an Autogenous Fascial Graft

Transected cranial cruciate ligaments in nine Holstein heifers were replaced with an autograft harvested from fascia on the medial surface of the gluteobiceps muscle and a connected segment of the lateral patellar ligament. There was minimal lameness at month 1, and all animals were sound by month 2. There was no evidence of degenerative joint disease in any stifles examined at necropsy on days 90, 120, or 365. Augmented healing of the severed cranial cruciate ligaments occurred in several animals. The mean failure strength of the cranial cruciate ligament replacements was 29.7% of the failure strength of the contralateral normal cranial cruciate ligament in four heifers. The technique was successful in eight of 13 bulls and cows with ruptured cranial cruciate ligaments. Animals treated successfully had significantly lower body weights than those with unsuccessful outcomes.