History
A 7-year-old 13.5-kg (29.7-lb) castrated male mixed-breed dog was referred for evaluation because of a 3-week history of ascites. The referring veterinarian had empirically treated the dog with amoxicillin, S-adenosylmethionine and silybin-phosphatidylcholine complex, prednisone, spironolactone, and furosemide (dosages unknown). On physical examination, the dog was quiet, alert, and responsive with no signs of discomfort, had a moderately distended abdomen with a palpable fluid wave, and had ecchymosis on the ventral and lateral aspects of its abdomen. No other abnormalities were detected on physical examination. Abnormal results for serum biochemical analyses and a CBC included mild hypoproteinemia (3.6 g/dL; reference range, 5.4 to 6.8 g/dL) and leukocytosis (38.9 × 103 WBCs/μL; reference range, 5.1 × 103 to 14.0 × 103 WBCs/μL) characterized by lymphocytosis (11.44 × 103 lymphocytes/μL; reference range, 1.1 × 103 to 4.6 × 103 lymphocytes/μL), monocytosis (4.24 × 103 monocytes/μL; reference range, 0.165 × 103 to 0.85 × 103 monocytes/μL), and mature neutrophilia (22.68 × 103 neutrophils/μL; reference range, 2.65 × 103 to 9.80 × 103 neutrophils/μL). Results for the dog's prothrombin time and partial thromboplastin time were within reference limits. Abdominocentesis was performed, and results of abdominal fluid analysis and cytologic examination indicated a transudate. Thoracic and abdominal radiography was performed (Figure 1).
Thoracic (left lateral [A] and ventrodorsal [B]) and abdominal (right lateral [C] and ventrodorsal [D]) radiographic images of a 7-year-old 13.5-kg (29.7-lb) castrated male mixed-breed dog examined because of a 3-week history of ascites.
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Thoracic (left lateral [A] and ventrodorsal [B]) and abdominal (right lateral [C] and ventrodorsal [D]) radiographic images of a 7-year-old 13.5-kg (29.7-lb) castrated male mixed-breed dog examined because of a 3-week history of ascites.
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Thoracic (left lateral [A] and ventrodorsal [B]) and abdominal (right lateral [C] and ventrodorsal [D]) radiographic images of a 7-year-old 13.5-kg (29.7-lb) castrated male mixed-breed dog examined because of a 3-week history of ascites.
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Diagnostic Imaging Findings and Interpretation
A focal, bulbous widening of the caudal vena cava was present at its juncture with the right atrium (Figure 2). The cardiac silhouette was small, and the pulmonary vessels were attenuated, consistent with hypovolemia. The abdomen lacked serosal detail, consistent with abdominal effusion. The liver extended beyond the costal arch and had rounded margins caudoventrally. The gastric axis was displaced caudally. Our prioritized differential diagnosis was partial obstruction of the caudal vena cava by a focal mass or, less likely, a thromboembolic lesion.
Same images as in Figure 1. A and B—There is a focal, bulbous widening of the caudal vena cava at its juncture with the right atrium (arrows). The cardiac silhouette is small, and the pulmonary vessels are attenuated. C and D—The abdomen has a severe lack of serosal detail, consistent with abdominal effusion. The liver extends caudally beyond the costal arch and has rounded margins caudoventrally (arrowheads). The gastric axis (line; C) is displaced caudally.
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Same images as in Figure 1. A and B—There is a focal, bulbous widening of the caudal vena cava at its juncture with the right atrium (arrows). The cardiac silhouette is small, and the pulmonary vessels are attenuated. C and D—The abdomen has a severe lack of serosal detail, consistent with abdominal effusion. The liver extends caudally beyond the costal arch and has rounded margins caudoventrally (arrowheads). The gastric axis (line; C) is displaced caudally.
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Same images as in Figure 1. A and B—There is a focal, bulbous widening of the caudal vena cava at its juncture with the right atrium (arrows). The cardiac silhouette is small, and the pulmonary vessels are attenuated. C and D—The abdomen has a severe lack of serosal detail, consistent with abdominal effusion. The liver extends caudally beyond the costal arch and has rounded margins caudoventrally (arrowheads). The gastric axis (line; C) is displaced caudally.
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Computed tomography was performed before and after administration of contrast medium (ioversol; 350 mg of I/mL; 2.2 mL/kg [1 mL/lb], IV) and revealed a lobulated, homogeneously soft tissue–attenuating (62 HU), non–contrast-enhancing mass (approx 4.2 × 2.4 × 2.6 cm [length × height × width]) contiguous with and indistinguishable from the wall of the right atrium (Figure 3). The mass extended caudally into the caudal vena cava as a broad-based mass, contiguous with the ventral, left, and right aspects of the vessel wall, and occluded most of the vessel lumen. Caudal to the mass, the caudal vena cava and the hepatic veins were dilated, and plexuses of multiple small, tortuous, and mildly dilated blood vessels arose from the left gastric and left gastroepiploic veins adjacent to the gastric fundus. These vessels drained into 2 mildly dilated paraesophageal veins that coursed dorsal and ventral along the esophagus before inserting into the azygos vein. The azygos vein was slightly dilated from this level to its insertion into the cranial vena cava. These findings were consistent with gastroesophageal varices. Also evident were marked abdominal effusion and hepatomegaly, a thickened gallbladder wall, mildly enlarged sternal and cranial mediastinal lymph nodes, and a healed rib fracture. Although hemangiosarcoma is the most common type of right atrial neoplasia in dogs,1 the homogeneous appearance, location, and obstructive nature of the lesion were considered atypical for hemangiosarcoma. Therefore, other considerations included primary or metastatic neoplasia (eg, lymphoma) or granulomatous disease (eg, fungal infection). An abbreviated echocardiographic examination (not shown) revealed portions of the mass associated with the right atrium; however, the entire extent of the mass could not be seen.
Precontrast thoracic transverse (A), postcontrast venous phase thoracic transverse (B), multiplanar reconstructed thoracic and cranial abdominal sagittal oblique (C) and dorsal oblique (D), postcontrast maximum intensity projection slab reconstruction thoracic and cranial abdominal dorsal oblique (E) and sagittal oblique (F), and localizer postcontrast transverse (G), sagittal (H), and dorsal (I) plane CT images of the dog described in Figure 1. A lobulated, homogeneous, soft tissue–attenuating mass (arrows) is associated with the right atrium and extends caudally into the caudal vena cava (plus sign). The caudal vena cava and hepatic veins (pound signs) are dilated caudal to the mass. Marked abdominal effusion (white asterisks) and hepatomegaly are evident. The gallbladder (GB) wall is thickened. There are several plexuses of multiple small, tortuous, and mildly dilated blood vessels arising from the left gastric and left gastroepiploic veins (in white squares), consistent with gastric varices. These vessels drain into 2 dilated paraesophageal veins (arrowheads) that course dorsal and ventral to the esophagus (daggers) before draining into the azygos vein (black asterisks). Images are displayed in a soft tissue window (window level, 60 HU; window width, 360 HU; slice thickness, 0.9 mm [A and B] or 0.54 mm [C and D]) or modified soft tissue window (window level, 180 HU; window width, 495 HU; slice thickness, 1.1 cm [E] or 1.5 cm [F]). G through I—The lines and transparent bars represent the planes and approximate slice or slab thicknesses of the other images (A and B, yellow lines; C, red line; D, blue line; E, transparent brown bar; F, transparent green bar). Toward the left in each image is the dog's right side (A, B, D, E, G, and I) or the dog's head (C, F, and H).
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Precontrast thoracic transverse (A), postcontrast venous phase thoracic transverse (B), multiplanar reconstructed thoracic and cranial abdominal sagittal oblique (C) and dorsal oblique (D), postcontrast maximum intensity projection slab reconstruction thoracic and cranial abdominal dorsal oblique (E) and sagittal oblique (F), and localizer postcontrast transverse (G), sagittal (H), and dorsal (I) plane CT images of the dog described in Figure 1. A lobulated, homogeneous, soft tissue–attenuating mass (arrows) is associated with the right atrium and extends caudally into the caudal vena cava (plus sign). The caudal vena cava and hepatic veins (pound signs) are dilated caudal to the mass. Marked abdominal effusion (white asterisks) and hepatomegaly are evident. The gallbladder (GB) wall is thickened. There are several plexuses of multiple small, tortuous, and mildly dilated blood vessels arising from the left gastric and left gastroepiploic veins (in white squares), consistent with gastric varices. These vessels drain into 2 dilated paraesophageal veins (arrowheads) that course dorsal and ventral to the esophagus (daggers) before draining into the azygos vein (black asterisks). Images are displayed in a soft tissue window (window level, 60 HU; window width, 360 HU; slice thickness, 0.9 mm [A and B] or 0.54 mm [C and D]) or modified soft tissue window (window level, 180 HU; window width, 495 HU; slice thickness, 1.1 cm [E] or 1.5 cm [F]). G through I—The lines and transparent bars represent the planes and approximate slice or slab thicknesses of the other images (A and B, yellow lines; C, red line; D, blue line; E, transparent brown bar; F, transparent green bar). Toward the left in each image is the dog's right side (A, B, D, E, G, and I) or the dog's head (C, F, and H).
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Precontrast thoracic transverse (A), postcontrast venous phase thoracic transverse (B), multiplanar reconstructed thoracic and cranial abdominal sagittal oblique (C) and dorsal oblique (D), postcontrast maximum intensity projection slab reconstruction thoracic and cranial abdominal dorsal oblique (E) and sagittal oblique (F), and localizer postcontrast transverse (G), sagittal (H), and dorsal (I) plane CT images of the dog described in Figure 1. A lobulated, homogeneous, soft tissue–attenuating mass (arrows) is associated with the right atrium and extends caudally into the caudal vena cava (plus sign). The caudal vena cava and hepatic veins (pound signs) are dilated caudal to the mass. Marked abdominal effusion (white asterisks) and hepatomegaly are evident. The gallbladder (GB) wall is thickened. There are several plexuses of multiple small, tortuous, and mildly dilated blood vessels arising from the left gastric and left gastroepiploic veins (in white squares), consistent with gastric varices. These vessels drain into 2 dilated paraesophageal veins (arrowheads) that course dorsal and ventral to the esophagus (daggers) before draining into the azygos vein (black asterisks). Images are displayed in a soft tissue window (window level, 60 HU; window width, 360 HU; slice thickness, 0.9 mm [A and B] or 0.54 mm [C and D]) or modified soft tissue window (window level, 180 HU; window width, 495 HU; slice thickness, 1.1 cm [E] or 1.5 cm [F]). G through I—The lines and transparent bars represent the planes and approximate slice or slab thicknesses of the other images (A and B, yellow lines; C, red line; D, blue line; E, transparent brown bar; F, transparent green bar). Toward the left in each image is the dog's right side (A, B, D, E, G, and I) or the dog's head (C, F, and H).
Citation: Journal of the American Veterinary Medical Association 258, 8; 10.2460/javma.258.8.839
Treatment and Outcome
A blood sample was submitted for PCR assay for antigen receptor rearrangements to further evaluate the nature of the patient's lymphocytosis (ie, infectious or inflammatory vs neoplastic). Amoxicillin, S-adenosylmethionine and silybin-phosphatidylcholine complex, spironolactone, and furosemide were discontinued, and the dog was prescribed prednisone (1.5 mg/kg [0.68 mg/lb], PO, q 24 h for 3 days; followed by 0.75 mg/kg [0.34 mg/lb], PO, q 24 h for 3 days; then q 48 h for 3 days), doxycycline (7.4 mg/kg [3.36 mg/lb], PO, q 12 h), and clopidogrel (1.4 mg/kg [0.64 mg/lb], PO, q 24 h). The owners declined biopsy of the caval mass. The dog's condition worsened, and 1 week later, the owners elected euthanasia and necropsy for the dog.
Necropsy revealed multifocal white-tan, firm, round to oval, smooth masses in the myocardium. The masses ranged from 1 cm in diameter to 2 × 2 × 4 cm, with the largest mass extending into and nearly occluding the caudal vena cava. On cut section, these masses were homogeneous and white-tan and diffusely infiltrated and expanded the myocardium. An enlarged cranial mediastinal lymph node (1 × 1 × 2.5 cm) was white-tan on cut section and lacked normal architecture. The abdominal cavity contained approximately 1,900 mL of cloudy pale-red fluid, and the dog's liver (0.76 kg) represented 5.2% (reference range, 3.0% to 3.5%) of the dog's body weight (14.5 kg [31.9 lb]), was friable, and had an enhanced reticular pattern.
Histologic examination revealed neoplastic cells extending caudally from the right atrial lesion that invaded and obliterated areas of the wall of the caudal vena cava, as suspected on CT. Additionally, lymphocytic hyperplasia with erythrocytic hypoplasia of the bone marrow and marked hepatic centrilobular glycogenesis and edema were observed. Results of the PCR assay for antigen receptor rearrangements confirmed a T-cell lymphocytic population. On the basis of findings, the diagnosis was primary cardiac lymphoma with vena cava infiltration and lymph node metastasis, consistent with stage 5 (manifestation in the blood and involvement of bone marrow or other organ systems) and substage b (systemic signs of disease present) lymphoma.2
Comment
Cardiac neoplasms in dogs are uncommon, with reported incidences of 0.12% to 4.33%.3 The most common cardiac tumor is hemangiosarcoma, with others (eg, aortic body tumors, lymphoma, and ectopic thyroid carcinoma) also reported.3 Unlike people, in whom B-cell lymphoma comprises 80%4 of cardiac lymphomas in immunocompetent individuals, dogs more commonly have T-cell lymphoma,5,6,7 which can affect dogs as young as 10 weeks of age.5
Pericardial effusion secondary to cardiac neoplasia is common and may result in cardiac tamponade and right heart failure; however, obstruction of blood flow by intracavitary cardiac tumors, including intracardiac lymphoma, is rare in dogs.8,9 The lack of pericardial effusion in the dog of the present report may have been unexpected but was consistent with findings in other dogs with cardiac lymphoma.5,7 If the dog of the present report had had pericardial effusion, perhaps diagnosis and treatment would have occurred sooner. Further, the mean survival time for dogs with cardiac lymphoma and pericardial effusion has been reported6 as 157 days for 5 dogs receiving chemotherapy and 22 days for 7 dogs not receiving chemotherapy, and those investigators concluded that cardiac lymphoma may not always warrant the poor prognosis typically associated with other types of lymphoma classified as stage 5b. The cause of the rapid clinical decline in the dog of the present report was unclear but could have related to potential further progression of lymphoma, heart failure, or both.
Thoracic radiography generally has limited use in diagnosing cardiac neoplasia. Visible changes to the cardiac silhouette may include a mass at the level of the heart base, a globoid cardiac silhouette indicative of pericardial effusion, or both. In the dog of the present report, the abnormal shape and size of the caudal vena cava and evidence of heart failure affecting the right side of the heart were appreciated. Echocardiography is a good modality to use in evaluating dogs for cardiac masses, with a reported sensitivity and specificity of 82% and 100%, respectively.10 In the dog of the present report, echocardiography was useful; however, we could not see the entire tumor because of its size and extension into the caudal vena cava, and we did not see additional masses later identified on necropsy. With CT, we could see the largest mass, but, similar to echocardiography, additional smaller lesions found on necropsy were not identified. These limitations were consistent with those previously reported11 for the detection of infiltrative cardiac masses in dogs; however, to our knowledge, this is the first report to describe CT findings of cardiac lymphoma in a dog.
In addition to ascites and hepatomegaly identified radiographically, CT also identified vascular abnormalities and gallbladder wall thickening in the dog of the present report. These findings were attributable to obstruction of the posthepatic portion of the caudal vena cava, between the right atrium and the caudal vena cava, that resulted in Budd-Chiari syndrome, a condition in which obstruction of hepatic venous outflow results in portal hypertension, hepatomegaly, and ascites.12,13 In dogs, Budd-Chiari syndrome is associated with the formation of acquired portal and caudal vena cava collateral circulation.12,14 In the dog of the present report, acquired portal collateral circulation consisted of gastroesophageal varices that drained into the azygos vein, which in turn drained into the cranial vena cava.
In people, MRI is considered the gold standard for imaging cardiac masses because of the modality's excellent soft tissue contrast.15 Although cardiac MRI in dogs shows potential,16 the procedure is not commonly performed, likely because of the need for specialized equipment, extended duration of the procedure, and additional cost.
References
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