CT/MRI Society Case of the Month
November 2006
Sponsored by Eklin Medical Systems
Patient Identification Number: CTMRSOC1
Patient Surname Code: CTMRSOC
Patient First Name Code: SCHWARZ
Accession Number: NOV06
Contributor: Tobias Schwarz
Contributor’s Affiliation: University of Wisconsin-Madison School of Veterinary Medicine
Species: Canine
Breed: Dachshund
Age at exam: 8 yr
Gender: Female Spayed
Presenting signs and pertinent history:
2 years ago constipated. Local veterinarian obtained abdominal radiographs and noticed caudal thoracic mass. Dog was and is asymptomatic. There is no specific reason why the owner selected to have this mass worked up now.
Clinical/Neuro Exam Findings: Normal
Relevant Laboratory data: Normal
Primary clinical rule-out pre imaging:
1. Slow growing lung mass
2. Caudal mediastinal mass
3. Diaphragmatic mass
Modality: CT
Manufacturer: GE
Model:
Single row helical CT unit
Automated bolus tracking
Sequences Acquired Pre- and Post-Contrast:
1. helical thorax precontrast, bone algorithm, 2 mm slice with, pitch 2.
2. helical thorax postcontrast (800 mg I/kg, 2 min post start injection), detail algorithm, 2 mm slice width, pitch 2.
3. helical abdomen post contrast (800 mg I/kg, start at peak aortic enhancement with power injector and bolus tracking feature), detail algorithm, 3 mm slice width, pitch 1.4.
CT Findings:
THORAX
1) Soft tissue attenuating mass in the right caudal hemithorax between the accessory and right caudal lung lobe (2x5.1x4.6cm WxHxL). It is abutting both lobes, the cardiac silhouette and comprising the caudal vena cava. Heterogeneous contrast enhancement.
2) V. azygos is of same size as the thoracic aorta and can be seen entering the cranial vena cava.
3) The intrahepatic portal vessels are enlarged.
ABDOMEN
1) The splenic vein is partially obliterated and there is a lateral and then central filling defect of the portal vein at the level of the splenic vein joining it.
2) There is a shunt arising from the caudal vena cava at the level of L7, curving laterally around the right kidney and joining the enlarged azygos vein at the level of T13.
3) The caudal vena cava cranially to the shunt continues as a small vessel, that decreases in diameter with the entrance of the left and right renal vein respectively, indicating retrograde flow.
Diagnostic interpretation:
1) Accessory lung lobe mass comprising and compressing the caudal vena cava.
2) DDX: caudal vena cava tumor, hepatic mass, right caudal lung lobe mass.
3) Cavo-azygos shunt, draining both kidneys.
4) Splenic vein thrombosis with extension of the thrombus into the portal vein
No evidence of brain invasion or abnormal leptomeningeal enhancement is identified.
Post Imaging Management:
Thoracic surgery was performed. The thoracic mass was mediastinal and could be completely separated from the caudal venal cava. The dog recovered normally from anaesthesia and was sent home the next day
Outcome:
Histopathology revealed hepatic tissue with biliary stasis that was otherwise normal.
Final Diagnosis based on all diagnostic tests and outcome:
Ectopic hepatic tissue that was separated from the liver during the fetal diaphragmatic fusion causing CVC compression and cavo-azygos shunt formation.
Splenic vein thrombosis
Comments:
The compressed CVC was able to handle the portal blood supply, but not systemic caudal caval blood supply, promoting the formation of a cavo-azygos shunt. Since the shunt did not deviate portal blood, no clinical signs of hepatic encephalopathy were present. Portal flow is probaly slow promoting splenic vein thrombosis.