CORRELATIVE IMAGING FINDINGS IN SEVEN DOGS AND ONE CAT WITH SPINAL ARACHNOID CYSTS

Information regarding 7 dogs and 1 cat with a spinal arachnoid cyst is presented. All patients were evaluated with survey radiographs and myelography. Computed tomography (CT) following myelography, magnetic resonance (MR) imaging, and sonography, were used in some of the patients. These imaging techniques were evaluated to determine their efficacy in diagnosing arachnoid cysts, ascertaining the extent and internal cyst architecture and detecting associated spinal cord abnormalities. Survey radiographs were nondiagnostic in all patients. Myelographically, the arachnoid cyst was visible in all patients, with partial blockage to flow of contrast medium. CT provided additional information on localization and lateralization of the cyst, and allowed measurement of the degree of spinal cord compression. MR imaging enabled identification of an associated syringomyelia. Sonography was useful for defining the cyst wall and characterizing the internal architecture of the cyst cavity and adjacent spinal cord. Measurements of the degree of spinal cord compression could be made and were similar to measurements made from CT. Additionally, sonography was considered a useful technique for orientating the surgeon to the location and extent of the cyst. In the absence of the availability of CT or MR imaging for evaluating patients with an arachnoid cyst, sonography is considered a valuable technique for directly assessing the spinal cord for associated disease. Decompressive surgery was performed on 4 dogs and 1 cat, all with successful outcomes.     

RESULTS OF MYELOGRAPHY IN SEVEN DOGS WITH MYELOMALACIA

Myelomalacia is a hemorrhagic infarction of the spinal cord that can occur as a sequel to acute spinal cord injury. Myelomalacia may be focal or diffuse; the diffuse form is typically associated with cranial migration of neurologic signs ("ascending syndrome") and is often fatal. In a retrospective study of seven affected dogs, diffuse myelomalacia was associated with intervertebral disc extrusion in five dogs, focal myelomalacia was associated with fibrocartilagenous embolus in one dog, and had no apparent cause in one dog. The myelographic signs included a variable degree of contrast medium infiltration into the spinal cord in six dogs (86%) and/or spinal cord swelling in six dogs (86%). In one dog with focal myelomalacia, the only myelographic sign was spinal cord swelling.     

OCCIPITAL DYSPLASIA AND ASSOCIATED CRANIAL SPINAL CORD ABNORMALITIES IN TWO DOGS

Occipital dysplasia was found in association with cervical spinal cord abnormalities in two dogs. One dog presented for tetraparesis and cervical hyperesthesia, the other for historical cervical hyperesthesia and mild paraparesis. In dog 1, a midline cervical spinal cord defect consistent with a communicating syrinx was found. In the other dog, a presumptive syringo/hydromyelia of the cervical spinal cord was found on magnetic resonance imaging. While occipital dysplasia alone is not thought to cause any clinical abnormalities, the dogs of this report suggest that intramedullary central nervous system abnormalities may be present concurrently with occipital dysplasia and should be considered as a possible cause of the clinical signs. The relationship between occipital dysplasia and syringo/hydromyelia in these dogs remains unclear, however, similar associated abnormalities are occasionally found in humans with Chiari malformation.     

COMPARISON OF RADIOGRAPHY, MYELOGRAPHY AND COMPUTED TOMOGRAPHY FOR THE EVALUATION OF CANINE VERTEBRAL AND SPINAL CORD TUMORS IN SIXTEEN DOGS

Radiographic, myelographic and computed tomographic (CT) studies from sixteen dogs with histologically diagnosed vertebral or spinal cord neoplasia (seventeen lesions) were retrospectively evaluated. Radiographs were compared with CT images to evaluate vertebral bony changes (bone production, lysis or both). Myelographic and CT images were evaluated to separate lesions into one of three categories, extradural, intradural/extramedullary, or intramedullary. These findings were compared to histologic tumor type from surgical or necropsy samples. Histologically, seven lesions were vertebral tumors and were classified as extradural lesions; ten lesions were spinal cord tumors of which eight were classified as intradural/extramedullary and two as intramedullary. Using CT, the amount of bony change associated with extradural lesions was greater than or equal to the amount of bony change visualized using radiographs. Myelography more correctly differentiated between intradural/ extramedullary and intramedullary lesions than did CT, although three open diagnoses detracted from the CT results. This study suggests that when evaluating extradural lesions, the amount of bony change was better visualized using CT than survey radiographs. Myelography was better when compared to CT for classifying spinal cord lesions, however, standardization of the CT imaging protocol may help determine the specific clinical indications for using CT in dogs with suspected vertebral or spinal cord tumors.     

POSTOPERATIVE IRRADIATION OF SPINAL CORD TUMORS IN 9 DOGS

Between 1985 and 1993, nine dogs with spinal cord tumors were treated postoperatively with cobaltradiation at North Carolina State University-Veterinary Teaching Hospital. Total doses ranged between 33.3–48.0 Gy given in 10–12 fractions of 3–4 Gy over a four week period. Five dogs were euthanized due to recurrence of the tumor or neurologic signs and two dogs were euthanized due tounrelated problems. Two dogs were alive but lost to follow-up at 12 and 25 months. Survival time ranged from 6.5–70.0 months. Median survival time (95% confidence interval) was 17 (12–70) months. Results of this study suggest decompressive surgery followed by irradiation can be an effective treatment for dogs with spinal cord tumors.     

PERIRENAL EFFUSION IN DOGS AND CATS WITH ACUTE RENAL FAILURE

Perirenal fluid accumulation has been described as an ultrasonographic feature of urine leakage, hemorrhage, abscessation, or neoplasia. The purpose of this retrospective study was to report perirenal effusion as an additional ultrasonographic finding in canine and feline patients with acute renal failure. The causes of acute renal failure in 18 patients included nephrotoxicity (4), leptospirosis (3), ureteral obstruction (2), renal lymphoma (2), ureteronephrolithiasis (2), prostatic urethral obstruction (1) and interstitial nephritis and ureteritis (1). An underlying cause was not identified in three patients. The sonographic finding of perirenal fluid was bilateral in 15 patients. Unilateral perirenal fluid was identified ipsilateral to the site of ureteric obstruction in two patients. Large effusions extended into the caudal retroperitoneal space. Additional sonographic findings suggestive of renal parenchymal disease included mild (5), moderate (5) or severe (2) pyelectasia, increased renal echogenicity (11), increased (9) or decreased renal size (2) and ureteral and/or renal calculi (3). There did not appear to be an association between the volume of perirenal fluid and the severity of renal dysfunction. All patients with large effusions underwent euthanasia. Perirenal fluid developing in acute renal failure is thought to be an ultrafiltrate associated with tubular back-leak into the renal interstitium that overwhelms lymphatic drainage within the perirenal and retroperitoneal connective tissues although obstruction to urine flow may also play a role. Localized perirenal retroperitoneal free fluid may be a useful ultrasonographic feature to assist with the characterization of, and determination of prognosis in, patients with suspected renal disease.     

MYELOGRAPHY IN THE CAT

Metrizamide myelographic examinations were performed on five normal cats using sequential cisternal and lumbar injections at weekly intervals to determine the dose of contrast medium required, adverse effects, and quality of the myelographic study. The normal myelographic appearance in the cat is described. All spinal cords were examined histopathologically after the termination of the study, and variable mild lesions were found. Doses of 0.2 ml/kg, 0.35 ml/kg, and 0.4 ml/kg metrizantide, respectively, for lumbar, thoracolumbar, and complete spinal studies are recommended when performing lumbar injection. Recommended doses using cisternal injection for cervical, cervicothoracic, and complete spinal studies are 0.2, 0.45, and 0.5 ml/kg, respectively. Subjectively, lumbar injection produced higher-quality thoracolumbar myelograms and cisternal injection produced higher-quality cervical studies. Clinical complications during the study included one seizure following cisternal myelography and mild neurologic deficits in all cats, which resolved within 36–48 hours.     

ULTRASONOGRAPHIC FINDINGS IN DOGS AND CATS WITH GASTROINTESTINAL PERFORATION

A retrospective study was performed to evaluate the sonographic features of gastrointestinal (GI) perforation in dogs and cats. Sonographic findings in 19 animals (14 dogs and 5 cats) included regional bright mesenteric fat (19), peritoneal effusion (16), fluid-filled stomach or intestines (12), GI wall thickening (11), presence of free air (9), loss of GI wall layering (9), regional lymphadenopathy (8), reduced GI motility (7), pancreatic changes (4), corrugated intestines (4), presence of a mass (3), presence of a foreign body (3), and mineralization of the gastric wall (1). In 14 patients, "perforation" was listed as a differential diagnosis by the sonographer. Abdominal radiographs and radiographic reports were available for 14 patients. Radiographic findings were decreased serosal detail (12), free air (8), peritoneal contrast medium (1), and suspected foreign body (1). GI perforation was listed as radiographic diagnosis in eight patients, seven of which had evidence of pneumoperitoneum, and one had leakage of contrast material on an upper GI study. In 9/14 patients with radiography, "GI perforation" was listed as a sonographic diagnosis. In three patients in which free air was diagnosed sonographically, radiographs were either not available (2) or the presence of free air was not detected at presentation (1). Peritoneal fluid analysis was performed in nine patients, five of which were identified as septic inflammation, and the remaining four were classified as neutrophilic inflammation with no etiologic agent identified. The histologic or surgical diagnoses were as follows: three intestinal surgical dehiscence; one percutaneous endoscopic gastrostomy tube site leakage; one duodenal adenocarcinoma; one ileocolic lymphoma; one trichobezoar; one ascarid impaction; and one bobby pin foreign body. In the remaining 10 patients, a focal area of gastric/intestinal ulceration or transmural necrosis with perforation was identified without evidence of an underlying cause.     

COLOR DOPPLER AND DOPPLER SPECTRAL ANALYSIS IN THE SPINAL CORD OF NORMAL DOGS

Doppler ultrasonography of the spinal cord was performed in 34 normal, anesthetized dogs following hemilaminectomy. This study was part of an investigation to evaluate the efficacy of a 21-aminosteroid compound and high dose methylprednisolone for the treatment of spinal cord trauma. Grey-scale images of the canine spinal cord were similar to those described for the spinal cord of people. Doppler waveforms of intraparenchymal spinal arteries exhibited high end diastolic blood flow velocities, indicating low resistance to flow. Doppler values (mean ± SD) for arteries immediately ventrolateral to the central canal were: Peak Systolic Velocity = 5.78 ± 2.5 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Systolic/Diastolic ratio = 169 ± 0.19, Pulsatility Index = 0.53 ± 0.09, and Resistance Index = 0.4 ± 0.06.     

COMPARISON OF FLUID-ATTENUATED INVERSION RECOVERY AND T2-WEIGHTED MAGNETIC RESONANCE IMAGES IN DOGS AND CATS WITH SUSPECTED BRAIN DISEASE

To compare fluid-attenuated inversion recovery (FLAIR) and T2-weighted magnetic resonance (MR) imaging in small animal patients with suspected brain disease, paired sets of FLAIR and T2-weighted MR images of 116 dogs and cats were reviewed separately without any patient information. Images were rated as normal or abnormal using a five-point scale, and the distribution, signal intensity, and anatomic location of abnormalities were recorded. In 60 animals, both FLAIR and T2-weighted images were normal. In 50 animals, the same abnormalities were identified in both FLAIR and T2-weighted images. Overall, very good agreement was found between FLAIR and T2-weighted MR images (kappa = 0.88). FLAIR images had abnormalities that were not recognized in the corresponding T2-weighted images in six of 116 examinations (5%). In four of these, the abnormalities in FLAIR images were thought to represent pathology, including granulomatous meningoencephalitis in one dog, postictal edema in one dog, and undiagnosed lesions in two dogs. In the remaining two examinations, the abnormalities in FLAIR images were probably artifacts. No examples were found of intracranial abnormalities in T2-weighted images that were not visible in FLAIR images. In this study, acquiring FLAIR images in addition to T2-weighted images resulted in detection of otherwise occult abnormalities in relatively few patients.     

EFFECTS OF METRIZAMIDE MYELOGRAPHY ON CEREBROSPINAL FLUID ANALYSIS IN THE DOG

The effect of metrizamide myelography on the composition of cerebrospinal fluid (CSF) was studied. Seven dogs received an intracisternal injection of metrizamide. An intracisternal puncture was performed in three additional dogs that did not receive metrizamide. CSF was collected before myelography and 24, 72, and 144 hours after myelography from all dogs. A significant increase in the percentage of neutrophils (p<0.05) and a pleocytosis noted 24 hours after myelography (p<0.02) were attributed to the effect of metrizamide. Significant increases in total protein concentration (p<0.001) and erythrocyte count (p<0.05), and a decrease in the percentage of small mononuclear cells (p<0.01) were attributed to repeated intracisternal puncture. No significant changes were observed for CSF creatine phosphokinase activity or the percentage of large mononuclear cells.     

IMAGING DIAGNOSIS—SPINAL CORD HEMANGIOMA IN TWO DOGS

Intramedullary masses are a dilemma due to the limited access for a nonsurgical biopsy, thus, accurate imaging characterization is crucial. Magnetic resonance imaging findings of two confirmed canine thoracic intramedullary hemangiomas are described. A capillary hemangioma was of mixed intensity but predominantly T2‐hyperintense and mildly T1‐hyperintense to spinal cord with strong contrast enhancement. A cavernous hemangioma had a target‐like appearance in both T1‐weighted (T1w) and T2‐weighted (T2w) images. In T2w images there was a small isointense center surrounded by a relatively large hyperintense area. In T1w images, there was a large isointense centre with a relatively small hyperintense periphery. Such characteristics should prioritize hemangioma as a consideration in a progressive myelopathy due to an intramedullary mass.     

SONOGRAPHY OF THE MUSCULOSKELETAL SYSTEM IN DOGS AND CATS

Sonography of the musculoskeletal system in dogs and cats was undertaken to evaluate the application of this imaging procedure in orthopedics. In most of the patients a 7,5 MHz linear transducer was used because of its flat application surface and its resolving power. The evaluation of bone by sonography is limited, but sonography can provide addition information regarding the bone surface and surrounding soft tissue. Ultrasound is valuable for assessing joint disease. Joint effusion, thickening of the joint capsule and cartilage defects can be identified sonographically. It is also possible to detect bone destruction. Instabilities are often identified with the help of a dynamic examination. Soft tissue abnormalities of the musculoskeletal system lend themselves to sonographic evaluation. Partial or complete muscles or tendon tears are able to be differentiated and the healing process can be monitored. Most of the diseases that are in the area of the biceps or the achilles tendon, such as dislocation of the tendon, old injuries with scarification, free dissecates in the tendonsheath, tendinitis and/or tendosynovitis can be differentiated by sonography. In addition, with clinical and laboratory findings, it is often possible to make a correct diagnosis with ultrasound in patients with abscesses, foreign bodies, hematomas, soft tissue tumors and lipomas.     

COMPLICATIONS OF METRIZAMIDE MYELOGRAPHY IN THE DOG: A SUMMARY OF 107 CLINICAL CASE HISTORIES

The case histories of 107 dogs undergoing metrizamide myelography at two veterinary hospitals were reviewed. Twenty-three variables, including body weight, injection site, dose of contrast medium, and medical complications during and after recovery from anesthesia, were submitted to statistical analysis by computer. Partial or generalized seizures were the most common medical complications, occurring in 54 percent of the dogs weighing more than 29 kg. Other less frequent medical complications were exacerbation of neurologic signs the day following myelography (11 percent), transient apnea during contrast medium injection (9 percent), vomiting (5 percent), hyperesthesia (3 percent), pyrexia (1 percent), and death (1 percent). The incidence of medical complications associated with metrizamide myelography in this study is higher than in previous reports. The most likely variables associated with seizures were high injection volumes and metrizamide injection at the cisterna magna. The preanesthetic administration of intramuscular pentobarbital did not significantly reduce seizure incidence. Seizures were controlled by anticonvulsant medication.     

ULTRASONOGRAPHIC ANATOMY OF THE NORMAL CANINE SPINAL CORD AND CORRELATION WITH HISTOPATHOLOGY AFTER INDUCED SPINAL CORD TRAUMA

Prior to trauma, intraoperative ultrasound of the spinal canal in 31 normal dogs was performed through a hemilaminectomy in the left pedicle of L2. A ventral compressive model of spinal cord injury was performed as part of a clinical drug trial. Maximum ultrasonographic spinal cord diameter ranged from 4.9–7.2 mm (5.7 × 0.6). Significant positive correlation (p = 0.023, r = 0.49) was found between age and spinal cord diameter. The dura mater was a separate, well-defined, echogenic horizontal line in 28 (90%) dogs, dorsally, and in 29 (94%) dogs, ventrally. Cerebrospinal fluid was anechoic. Eighteen (58%) dogs had a well-defined anechoic dorsal subarachnoid space, whereas 22 (71%) had a well-defined ventral space. Pia mater was thin but strongly echogenic and covered spinal cord. Central canal was a double hyperechoic line in 17 (55%) dogs and a single-line in 14 (45%) dogs. A difference in the ultrasonographic appearance between gray and white matter was not seen. Epidural fat and connective tissue was a lobular echogenic material in the ventral epidural space. The periosteal-vertebral body interface was seen as a bright curvilinear echo with distal acoustic shadowing. Spinal cord parenchyma could be classified subjectively into four groups based upon ultrasonographic appearance. Spinal cord parenchyma had a uniform hypoechogenicity in 8 (27%) dogs (Group 1), subtle low level echoes in 7 (23%) dogs (Group 2), multiple clusters of defined echogenic foci in 12 (37%) dogs (Group 3), and multiple sharply-defined linear echoes in 4 (13%) dogs (Group 4). There was a significant relationship between pre-trauma ultrasonographic appearance of the spinal cord and histopathology 21 days after trauma. One (13%) dog in Group 1, 4 (57%) dogs in Group 2,10 (91%) dogs in Group 3, and 3 (75%) dogs in Group 4 had malacia on histological evaluation. Therefore, dogs with echogenic spinal cords or linear echoes within cord parenchyma were significantly more likely to develop malacia rather than Wallerian degeneration after induced spinal cord trauma (p = 0.002). Spinal cord echogenicity may indicate vascularity in a segment of spinal cord and might be prognostic following spinal cord trauma. No complications were found related to intraoperative ultrasound. Hematoma or fibrous tissue formation appeared to impede percutaneous ultrasound of the spinal cord in dogs re-evaluated forty-eight hours and one week after surgery.     

IOHEXOL PLASMA CLEARANCE IN HEALTHY DOGS AND CATS

Iohexol plasma clearance as a measure of glomerular filtration was determined in 31 dogs and 19 cats after an intravenous (i.v.) bolus injection. All animals were healthy and privately owned. Serial blood samples were taken before and up to 4 h after tracer injection. Iohexol plasma concentration was determined using X-ray fluorescence. A plasma tracer elimination curve was generated and clearance was calculated by dividing the injected dose by the area under the curve estimated using a two-compartment pharmacological model. Clearance was normalized to body weight (BW), body surface area (BSA), and extracellular fluid volume (ECFV). Mean, SD, and coefficient of variation of plasma clearance, before and after normalization, were calculated. Linear regression analyses were performed between body size and normalized plasma clearances. No significant linear relation was found between BSA and clearance normalized to BSA in dogs, and between BSA, BW, ECFV and clearance normalized to BSA, BW, and ECFV in cats. The optimal method for normalization of iohexol plasma clearance in dogs was by using BSA. In cats, all three methods tested were considered satisfactory. Normalization to BSA appears to be superior to normalization to BW and ECFV in dogs, and can be recommended for clinical use.     

RADIOGRAPHIC APPEARANCE OF CONFIRMED PULMONARY LYMPHOMA IN CATS AND DOGS

Herein we describe the thoracic radiographic appearance of confirmed pulmonary lymphoma. Patients with thoracic radiographs and cytologically or histologically confirmed pulmonary lymphoma were sought by contacting American College of Veterinary Radiology members. Seven cats and 16 dogs met the inclusion criteria, ranging in age from 4 to 15 years. Method of diagnosis was via ultrasound‐guided cytology (four), surgical biopsy (two), ultrasound‐guided biopsy (one), and necropsy (16). Radiographic findings varied but ranged from normal (one) to alveolar (six) and/or unstructured interstitial infiltrates (11), nodules and/or masses (eight), and bronchial infiltrates (four). Additional thoracic radiographic findings included pleural effusion and lymphadenopathy. The results of this evaluation indicate a wide variability in thoracic radiographic abnormalities in cats and dogs with pulmonary lymphoma.     

USE OF ULTRASOUND TO DIAGNOSE DIAPHRAGMATIC RUPTURE IN DOGS AND CATS

Twenty-one cats and six dogs that presented to a first-opinion clinic with signs of dyspnea and muffled cardiac auscultation received ultrasonography to look for signs of diaphragmatic rupture. The presence or absence of diaphragmatic rupture was subsequently determined on the basis of unequivocal radiographic signs, surgical findings, or necropsy. Consistent findings in animals with diaphragmatic rupture were irregular or asymmetric cranial aspect of the liver and abdominal viscera in the thorax. Accuracy of ultrasonography was 25/27 (93%). One false-negative result occurred in a cat with a chronic diaphragmatic rupture in which adhesions between the liver and lung simulated the appearance of an intact diaphragm. One false-positive result occurred in a dog with an abscess involving the left lung and pleural cavity, which was misinterpreted as the stomach. The results of this study support use of ultrasonography in animals with suspected diaphragmatic rupture.     

RETROSPECTIVE ANALYSIS OF BRAIN SCINTIGRAPHY IN 116 DOGS AND CATS

We performed a retrospective study of 100 dogs and 16 cats with planar brain scintigraphy and histopathologically established diagnoses from a total of 485 studies performed from 1976 to 1992. Necropsy (112) or surgical biopsies (4) diagnoses were categorized in two ways: first as focal brain disease, diffuse brain disease or normal; second as either neoplastic, non-neoplastic or normal. A radiologist reviewed brain scintigrams and categorized the studies as focal areas of increased accumulation, diffuse or poorly localized areas of increased accumulation, or normal. We calculated for this population of 116 animals that focal brain scintigrams had 75% sensitivity and 90% specificity for any focal brain disease. The sensitivity and specificity of a focal scintigraphic lesion for a brain tumor was 72% and 82% respectively. The sensitivity and specificity of a diffuse or poorly localized scintigraphic lesion as a test for diffuse brain disease was 40% and 88% respectively.     

ULTRASONOGRAPHIC DIAGNOSIS OF PORTOSYSTEMIC SHUNTING IN DOGS AND CATS

The value of ultrasonography was evaluated in 85 dogs and 17 cats presented with a clinically suspected portosystemic shunt (PSS). A PSS was confirmed in 50 dogs and nine cats (single congenital extrahepatic in 42, single congenital intrahepatic in 11, and multiple acquired in six). Six dogs and one cat had hepatic microvascular dysplasia, and 29 dogs and seven cats had a normal portal system. Ultrasonography was 92% sensitive, 98% specific, and had positive and negative predictive values of 98% and 89%, respectively, in identifying PSS, with an overall accuracy of 95%. When a PSS was identified with ultrasonography, extrahepatic, intrahepatic, and multiple acquired PSS could be correctly differentiated in 53/54 patients (98%). The combination of a small liver, large kidneys, and uroliths had positive and negative predictive values of 100% and 51% for the presence of a congenital PSS in dogs. The portal vein/aorta (PV/Ao) and portal vein/caudal vena cava (PV/ CVC) ratios were smaller in animals with extrahepatic PSSs compared with animals with microvascular dysplasia, intrahepatic PSSs and those without portal venous anomalies (P<0.001). All dogs and cats with a PV/Ao ratio of < or = 0.65 had an extrahepatic PSS or idiopathic noncirrhotic portal hypertension. Dogs and cats with PV/Ao and PV/CVC ratios of > or = 0.8 and > or = 0.75, respectively, did not have an extrahepatic PSS. Reduced or reversed portal flow was seen in four of four patients with multiple acquired PSSs secondary to portal hypertension. The presence of turbulence in the caudal vena cava of dogs had positive and negative predictive values of 91% and 84%, respectively, for the presence of any PSS terminating into that vein.