MR IMAGING OF HISTIOCYTIC SARCOMA OF THE CANINE BRAIN

Histiocytic sarcomas are characterized by proliferation and/or infiltration of neoplastic histiocytes localized to specific organs, unlike malignant histiocytosis which involves many organ systems. Only a few cranial histiocytic sarcomas have been reported. Here we describe four dogs that presented with neurological deficits referable to the forebrain, and were diagnosed histologically as having histiocytic sarcoma. Using magnetic resonance (MR) imaging, the tumors were characterized by a T2-hyperintense and T1-isointense mass in one dog, T2- and T1-isointense extraaxial masses in two dogs, and a diffuse T2-hyperintense lesion over the left cerebral cortex in one dog. All tumors had contrast enhancement. MRI features in three of the four dogs were similar to that of meningioma, supported by the observation of a dural tail in two of these three dogs, and a broad base of attachment in the other. In the other dog the imaging findings were similar to those of encephalitis. Intracranial histiocytic sarcoma does not appear to have specific MR imaging features and can be confused with meningioma or encephalitis.     

SKELETAL LESIONS OF HISTIOCYTIC SARCOMA IN NINETEEN DOGS

The purpose of this study was to describe the clinical and radiographic findings in dogs with bone lesions secondary to histiocytic sarcoma. Nineteen dogs with radiographically identified bone lesions that were histologically diagnosed as histiocytic sarcoma were assessed. The medical records, all available radiographs and histologic sections were reviewed retrospectively. Dogs were subcategorized into localized or disseminated histiocytic sarcoma groups. Golden Retrievers or Rottweilers greater than 5 years of age, with a history of lameness or neurologic deficits localized to the spinal cord was the most common presentation. Fifteen of 19 dogs had a radiographically detectable soft tissue mass associated with bone destruction. The bone lesions had aggressive characteristics and the sites of involvement included periarticular bones (n = 11), vertebrae (n = 6), proximal humerus (n = 5), and rib (n = 2). Fifteen of 19 dogs had disseminated histiocytic sarcoma, and four had localized histiocytic sarcoma. All Rottweilers had disseminated histiocytic sarcoma. Histiocytic sarcoma should be considered as a differential diagnosis for aggressive periarticular, vertebral, or proximal humeral bone lesions identified on radiographs. The index of suspicion should be increased in greater than 5-year-old Golden Retrievers and Rottweilers when a soft tissue mass is associated with the bone lesion on radiographs or myelography. Bone involvement with histiocytic sarcoma, and the Rottweiler breed, was associated with the disseminated form of the disease.     

ULTRASONOGRAPHIC FINDINGS IN CANINE GASTRIC NEOPLASIA IN 13 PATIENTS

The ultrasonographic findings in 13 canine patients with histopathologically proven gastric tumors were reviewed. The echogenicity of gastric wall lesions was variable and independent of the type of tumor. All dogs had an increase in gastric wall thickness and in only one dog was the wall layering intact. Regional lymph node involvement was a common finding, but abnormalities within the liver were seen in only one patient. Gastric neoplasia was observed most commonly in middle-aged and old, medium- to large-sized dogs. Carcinoma was the most common tumor found. In this study, with a limited number of animals and limited tumor types, it appeared that thickening of the gastric wall, accompanied by loss of gastric wall layering and enlargement of regional lymph nodes were ultrasonographic signs likely to be found with gastric neoplasia. In this limited study the histologic type of gastric tumor could not be predicted on the basis of the ultrasound examination.     

TRANSABDOMINAL SONOGRAPHIC EVALUATION OF THE CANINE PROSTATE

The present study sought to determine the accuracy of ultrasonographic measurement of the prostate; to observe the ultrasonographic appearance of the normal prostate; and to compare these observations with those in prostates affected by cystic hyperplasia, benign hyperplasia, land neoplasia. Trassabdominal ultrasonography of the canine prostate was performed in eight normal dogs to establish criteria for evaluating enlarged prostates. Marginal boundries, size, and ultrasonographic architecture were compared with dissection findings to assess the accuracy of ultrasonography. Four enlarged prostates were evaluated ultrasonographically, and the findings were correlated with results of needle aspiration and urethral wash and with surgical and histopathologic findings. Differentiation between cystic and solid prostatic enlargement by ultrasonography proved efective. Transducer frequency and gain manipulation were important factors in describing the nature of the fluid within a cyst. Assenssment of the nature of solid prostatic enlargement and accurate size determination proved to be areas in which ultrasonography should by used in conjunction with other diagnostic techniques.     

ULTRASONOGRAPHIC FEATURES OF CANINE HEPATIC NODULAR HYPERPLASIA

Hepatic nodular hyperplasia is a benign, usually clinically inapparent, proliferative lesion commonly found at necropsy in older dogs. Three examples of hepatic nodular hyperplasia are described in dogs with clinical signs compatible with hepatic disease in which ultrasonography revealed a variety of echotextural changes in the liver similar to those reported in primary or secondary hepatic neoplasia. In subsequent in vitro ultrasonographic studies of hepatic nodular hyperplasia lesions detected at necropsy in dogs without clinical signs of hepatic disease, only subtle echotextural changes were seen. Hence, hepatic nodular hyperplasia may be inapparent in vivo in many dogs. Hepatic nodular hyperplasia is a potentially confusing sporadic finding which must be considered by ultrasonographers examining dogs with clinical signs of hepatic disease. The diagnosis of hepatic neoplasia should not be made on the basis of ultrasonographic findings alone.     

COMPUTED TOMOGRAPHY OF SPONTANEOUS CANINE NEOPLASMS*

Five spontaneous extracranial canine neoplasms studied by a computed tomography whole body scanner are presented: an undifferentiated sarcoma of the scapula, a mast cell sarcoma of the hip, a mast cell sarcoma of the neck, a fibrosarcoma of the neck, and a malignant melanoma of the gingiva. Computed tomography enables accurate detection and definition of tumor size and extent and is, therefore, an aid to diagnostic evaluation, therapy, and prognosis.     

TRANSCUTANEOUS ULTRASONOGRAPHY OF THE ABDOMEN IN THE NORMAL COMMON MARMOSET (CALLITHRIX JACCHUS)

Ultrasonographic examinations were performed on 17 clinically healthy adult common marmosets to gain information about the normal abdominal echoanatomy. The marmosets were 1.5-9 years of age and weighed between 328 and 506g. Marked species-specific differences compared with the cat or dog were noted. Good images of the kidneys, bladder, spleen, adrenal glands, liver, and the gastrointestinal tract could be obtained. The pancreas, caecum, and abdominal lymph nodes were not seen. The spleen was the least echogenic organ, followed by the medium echogenic liver and the sometimes isoechoic, but mostly hyperechoic renal cortex. The kidneys had a poor corticomedullary distinction. The prominent right lobes of the liver extended caudally far beyond the costal arch. The gallbladder had a bi- to multi-lobed appearance with a wide, tortuous cystic duct. The pylorus was centrally positioned. The adrenal glands were readily seen, but should not be confused with the adjacent spleen. A statistically significant (P<0.05) difference between female and male kidney, and right adrenal gland length was present.     

RADIOGRAPHIC FINDINGS IN CANINE MALIGNANT HISTIOCYTOSIS

Radiographs of 19 dogs diagnosed as having malignant histiocytosis were examined. The most common abnormalities involved the spleen (10), liver (6), lymph nodes (6 thoracic, 4 abdominal), and lungs (6). Other abnormalities involved the spinal column (3), and bones (2). Correlations were made between radiographic appearance and histologic diagnoses. As has been reported, Bernese Mountain Dogs were found to be significantly more often affected than other breeds. Rottweilers and Golden Retrievers were also found to have higher incidence rates. Viewed radiographically, treatment appeared to have little impact on the course of the disease.     

SONOGRAPHIC EVALUATION OF CANINE TESTICULAR AND SCROTAL ABNORMALITIES: A REVIEW OF 26 CASE HISTORIES

The ultrasonographic and medical records of 26 dogs examined for testicular/scrotal abnormalities were reviewed. Fifteen dogs were diagnosed with testicular neoplasia that included one or more of the following tumor cell types: Sertoli cell, seminoma and interstitial cell. Ultrasound was highly sensitive to detection of testicular neoplasia including one nonpalpable tumor. Tumor type specificity was not readily apparent in this study, although the three nondescended Sertoli cell tumors displayed similar characteristic sonographic patterns. Six dogs were reviewed with nonneoplastic, noninfectious disorders that included: vascular compromise, atrophy, scrotal edema and intestinal hernia. Five dogs with infectious diseases were reviewed. Ultrasound was sensitive and relatively specific for the nonneoplastic conditions.     

NODULAR FAT NECROSIS IN THE FELINE AND CANINE ABDOMEN

The radiographic appearance of nodular fat necrosis is described in ten cats and one dog. The most common radiographic sign was the presence of a focal mineralized circular to oval soft tissue mass in the abdominal fat as present in 9 cats. These masses had a distinct eggshell-like rim encapsulating the lesion. In one cat and one dog multiple masses were present, without radiographic signs of mineralization. Abdominal ultrasound was performed in three cats and one dog, findings included the presence of hyperechoic masses with associated acoustic shadowing, some with a hypoechoic centre. Almost all animals were old and obese. In three cats and one dog, changes were confirmed with biopsy or post mortem examination. Lesions having the appearance of those in this paper are most likely incidental findings and should not be confused with abdominal masses of neoplastic origin. Ultrasound can be helpful in identifying such lesions.     

SONOGRAPHIC EVALUATION OF URINARY BLADDER WALL THICKNESS IN NORMAL DOGS

Urinary bladder wall thickness was evaluated by ultrasonography in 16 normal dogs. Sterile saline solution was administered via urinary catheters to control the degree of bladder distention. Bladder wall thickness was measured on static ultrasound images in 4 locations and at 3 degrees of bladder distention (minimal, mild, and moderate). Four randomized distention sequences with 3 distentions per sequence were performed on each dog and the data were analyzed using Williams' balanced Latin square. Mean bladder wall thickness was 2.3 mm in minimally distended bladders (0.5 ml/kg saline), 1.6 mm in mildly distended bladders (2 ml/kg saline) and 1.4 mm in moderately distended bladders (4 ml/kg saline). Mean bladder wall thickness increased significantly with increasing body weight and with decreasing bladder distention. The caudoventral measurement location produced a statistically significant smaller measurement, with a difference of 0.3 mm. Sex did not affect bladder wall thickness. Distention sequence and repetition of distentions did not affect bladder wall thickness.     

ULTRASONOGRAPHIC FEATURES OF CANINE LIPOMAS

The purpose of this study was to evaluate the ultrasonographic features of canine lipomas. A group of 94 dogs with a soft tissue mass was considered. All dogs were examined ultrasonographically and cyto/histologic examination was performed. Twenty-four dogs, whose mass was diagnosed as a lipoma, were selected. Fifty-five lipomas were present on the 24 dogs. Fifty-one lipomas were superficial and located subcutaneously. Four lipomas were deep and located in the paratesticular region. Ultrasonographically, lipomas appeared as oval, well-defined, encapsulated, striated masses.     

CELLULAR FEATURES OF SONOGRAPHIC TARGET LESIONS OF THE LIVER AND SPLEEN IN 21 DOGS AND A CAT

Target lesions are seen in ultrasound images of the liver or spleen as nodules or masses with a hypoechoic rim and a hyperechoic or isoechoic center. To assess the diagnostic significance of finding a target lesion, the cytologic and/or histopathologic findings were reviewed in a series of 21 dogs and a cat that had hepatic and/or splenic target lesions noted during abdominal ultrasonography. Twelve of 16 hepatic target lesions and 5 of 7 splenic target lesions were malignant. In this series, the finding of one or more target lesions in the liver or spleen had a positive predictive value for malignancy of 74%; for the finding of multiple target lesions in one organ, the positive predictive value for malignancy was 81%. Benign lesions associated with target lesions were nodular hyperplasia of the liver and spleen, pyogranulomatous hepatitis, cirrhosis, and chronic active hepatitis.     

COMPARISON OF SONOGRAPHIC FEATURES OF BENIGN AND NEOPLASTIC DEEP LYMPH NODES IN DOGS

The differentiation of benign vs. neoplastic lymph nodes impacts patient management. Specific sonographic features are typically considered when assessing lymph nodes in dogs. However, the usefulness of these criteria in distinguishing benign vs. malignant lymph nodes remains largely unknown, especially for deep lymph nodes. Our aim was to compare sonographic features in benign and neoplastic deep lymph nodes with the hope of identifying predictive criteria. Thirty‐one deep lymph nodes (16 mesenteric, 10 medial iliac, three hepatic, one sternal, and one cranial mediastinal) in 31 dogs were examined prospectively with B‐mode and Color flow Doppler. Lymph nodes were aspirated using ultrasound‐guidance and final diagnosis were established based on cytologic and/or histopathologic interpretation. Prevalence of each sonographic feature and combinations of two features was calculated for each group and compared using a χ²‐test or Student's t‐test for unequal variances. Ten lymph nodes were benign (hyperplastic and/or inflammatory) and 21 were neoplastic. All were hypoechoic, except for one neoplastic lymph node. Maximal short‐axis diameter (P=0.0006) and long‐axis diameter (P=0.01), and SA/LA ratio (P=0.008) were increased significantly for neoplastic (2.8, 5.5 cm, and 0.50, respectively) vs. benign (1.2, 3.8 cm, and 0.34, respectively) lymph nodes. The prevalence of other features was similar between groups. Doppler evaluation was possible in 77% of lymph nodes, but there was no significant difference between groups. When any two ultrasound features were combined, the only difference between benign and neoplastic lymph nodes was for the combination of contour regularity and appearance of the perinodal fat (P=0.03).     

SONOGRAPHIC APPEARANCE OF RENAL NEOPLASIA IN THE DOG

Eight dogs with renal neoplasia were radiographically and sonographically examined. An enlarged, nonopacified kidney was seen on the excretory urogram in four dogs, but differentiation between a solid mass or severe hydronephrosis was not possible. The excretory urogram suggested an avascular lesion in one kidney, but differentiation between solid or cystic disease was not possible. Renal neoplasia was diagnosed in two dogs by excretory urography. Radiographic examination suggested splenic neoplasia in one dog. Solid masses were sonographically diagnosed in all dogs. A metastatic lesion was sonographically diagnosed in the opposite kidney of one dog that was missed on the radiographic examination. Ultrasonography com-plemented radiography as a diagnostic modality in eliciting additional information on renal disease. Sonograms did not allow determination of tumor cell type or whether the tumor was benign or malignant.     

PRENATAL SONOGRAPHIC DIAGNOSIS OF FETAL DEATH AND HYDRANENCEPHALY IN TWO CHIHUAHUA FETUSES

Hydranencephaly and fetal death was diagnosed in two of three fetuses during the abdominal sonographic examination of a 2.5-year-old, intact female Chihuahua that had clinical signs of dystocia 63 days after mating. A cesarean section was performed and one live normal puppy was present. Two dead puppies, each with a markedly enlarged and fluid filled skull were removed.     

ULTRASOUND APPROACH TO THE CANINE DISTAL TIBIA AND TROCHLEAR RIDGES OF THE TALUS

The aim of the present study was to evaluate to what extent the distal tibia and the trochlear ridges of the talus can be examined with ultrasound (US) in the dog and to establish a protocol for an optimal US examination of these ridges. Six hind limbs of deceased adult mixed-breed dogs were used. In two limbs, needles were placed using US guidance on the trochlea of the talus, just dorsal to and plantar to the distal tibia: one with the tarsal joint in extension and one with the joint in flexion. Then mediolateral (ML) radiographs of both joints were made with the needle in place to determine the percentage of the trochlear ridge of the talus that can be seen using US imaging. An US examination of the tarsal joint was performed on the four other limbs using microconvex (8 MHz) and linear (12 MHz) transducers (Logiq 7) and compound imaging. A three-step protocol was performed including a dorsal approach with the limb extended and the linear transducer (step I), a plantar approach with the limb flexed and the linear transducer (step II), and a plantar approach with the limb flexed and the microconvex transducer (step III). After the US examination, the four limbs were frozen and sectioned, two in a transverse and two in a sagittal plane. Bony structures on the US images were matched with the corresponding anatomic sections. The distal tibia and both trochlear ridges of the talus were easily recognized on the US images using the proposed protocol. When combining the dorsal and plantar approaches, it was possible to visualize up to 75% of the trochlear ridges of the talus in the dog.     

IMAGING DIAGNOSIS—SPINAL CORD HISTIOCYTIC SARCOMA IN A DOG

A 12‐year‐old mixed breed dog was presented for evaluation of progressive paraparesis and ataxia. Magnetic resonance (MR) imaging was performed and identified multifocal intradural spinal cord mass lesions. The lesions were hyperintense in T2‐weighted sequences, isointense to mildly hyperintense in T1‐weighted sequences with strong contrast enhancement of the intradural lesions and spinal cord meninges. Spinal cord neoplasia was suspected. A diagnosis of intramedullary spinal cord histiocytic sarcoma, confined to the central nervous system, was confirmed histopathologically. Spinal cord histiocytic sarcoma is a rare neoplasm, but should be included in the differential diagnosis for dogs with clinical signs of myelopathy.     

ENDOSCOPIC ULTRASOUND OF THE CANINE ABDOMEN

The aim of this study was to develop a standardized procedure for examination of the canine abdomen using endoscopic ultrasound and to describe the organs and structures that could be identified transgastrically. The abdomen of four healthy dogs and two cadavers were examined with endoscopic ultrasound. Five anatomic landmarks were used for standardized imaging of the cranial abdomen. These were the portal vein, splenic head and body, duodenum, left kidney, and aorta. High-resolution images of the following organs and structures could be made: distal esophagus, gastric wall from the cardia to the pylorus, liver, caudal vena cava, hepatic lymph nodes, liver hilus, and associated vessels, trifurcation of the celiac artery as well as the path of its branches and the left pancreatic limb and body. Structures that were more difficult to image were the distal duodenum and right pancreatic limb, the entire jejunum, ileum, and cecum as well as the tail of the spleen. Endoscopic ultrasound allowed excellent visualization of the gastric wall and regional structures without interference with gas artefacts. Centrally located organs such as the pancreas could be well examined transgastrically with endoscopic ultrasound without interference by overlying intestinal segments as is common with transabdominal ultrasound.