12-years-old, Toy Poodle dog. Presented with mass palpable in the abdomen. An abdominal and thoracic CT-scan was performed.
Description
There is a large, oval, soft tissue mass (red arrows) with markedly irregular and ill-defined margins, located in the caudal aspect of the retroperitoneum, adjacent and ventral to the abdominal aorta and caudal vena cava. The mass has a markedly heterogeneous soft tissue attenuation with strong and heterogeneous post-contrast enhancement. The mass causes a mild dorsal displacement of the aorta (Ao) and its trifurcation (pink arrows). In addition, the mass causes a severe invasion of the caudal vena cava, which is distended with a large filling defect with an intravenous thrombus, showing the same attenuation and post-contrast enhancement as the mass (blue arrows). The mass also invades both common iliac veins, more prominent and extensive on the right compared to the left (orange arrows).
Adjacent to the mass (red arrows), on the left side, there is another oval mass, showing better defined margins and similar characteristics with strong and heterogeneous contrast enhancement, that could be consistent with a severely enlarged left medial iliac lymph node (green arrows).
The left kidney is markedly hydronephrotic with a severe distention of the renal pelvis, with preservation of a thin cortex (green arrows). The proximal aspect of the left ureter is also markedly distended, filled with fluid attenuating material up to the level of the mass, where the ureter seems to be embedded within the mass (pink arrows).
The right adrenal gland is enlarged with well-defined and irregular margins, showing a strong and slightly heterogeneous post-contrast enhancement (orange arrows). The lesion invades the phrenicoabdominal vein, with a filling defect that has the same attenuation as the lesion in the adrenal (blue arrows). It is also in intimate contact with the caudal vena cava causing a mild invasion, with a small and irregular filling defect (purple arrows).
There are multiple small pulmonary nodules, with soft tissue attenuation, showing mild contrast enhancement, spread throughout the lung lobes (orange arrows).
One of the cranial mediastinal lymph nodes is slightly prominent with homogeneous post-contrast enhancement (orange arrows).
Diagnosis
- Mass with aggressive characteristics affecting the right adrenal gland, most likely consistent with malignant neoplasia (primary adrenal tumor – pheochromocytoma or carcinoma vs metastasis from the mass located in the caudal retroperitoneum). The mass causes invasion of the right phrenicoabdominal vein and mild invasion of the cauda vena cava.
- Mass located in the caudal retroperitoneum, ventral to the aorta and caudal vena cava, infiltrative and with ill-defined margins, most likely consistent with a neoplastic process (retroperitoneal paraganglioma, most likely).
The mass severely invades the caudal vena cava and other adjacent vessels, such as both common iliac veins, both deep circumflex iliac veins, median sacral vein and caudal vesical vein.
Moderate left hydroureter and marked left hydronephrosis, most likely secondary to invasion/severe compression of the left ureter by the mass.
- Severe left medial iliac lymphadenopathy most likely consistent with metastasis.
- Multiple small pulmonary nodules throughout the lung parenchyma, most likely consistent with metastasis.
- Mild cranial mediastinal lymphadenopathy, most likely consistent with metastasis vs reactive.
