2013 Radiology Exam - CT/MRI Case 2

History: 14 year old male neutered Dalmatian with a history of azotemia and abdominal pain, dog was neutered 5 months ago.

Images given: pre- and post-contrast transverse images of the abdomen in a soft tissue window; sagittal reformats were available if the candidate asked for them, but were not required to successfully interpret the case.

Observation:

  • Large, heterogeneous soft tissue attenuating mass, with amorphous mineral foci centrally, of the right kidney (peripherally soft tissue attenuating and centrally soft tissue to fluid attenuating)
  • Contrast filling defect in the CVC with a stalk of tissue extending from the renal mass to this area of the kidney, presumed to be renal vein tumor thrombus
  • Normal right adrenal gland
  • Bilaterally symmetrically enlarged prostate gland with cystic and mineral foci throughout the parenchyma

Synthesis:

  • Right renal mass most likely represents neoplasia such as renal adenocarcinoma. The mass has mineralization and a necrotic/avascular center. A renal granuloma cannot be ruled out.
  • Right renal vein and CVC tumor extension or thrombosis
  • Prostatic changes most likely due to benign prostatic hyperplasia (late neuter); prior or chronic prostatitis cannot be ruled out.

Comments:
This case was typically the most time consuming CT case. Candidates that were the most successful identified the mass as renal in origin, identified the vascular invasion, and identified the normal right adrenal gland. They also found the ureter dorsal to the mass (this also had questionable invasion at its origin.) They also concluded that the prostatic changes were most likely benign and unrelated to the tumor. Less successful candidates did not identify the vascular invasion or interpreted a tubular structure medial to the kidney to be a severely dilated ureter and diagnosed hydroureter/hydronephrosis. (Although this structure was admittedly confusing, it did not continue to the urinary bladder and a more normally sized ureter could be found dorsal to the mass and did continue to the bladder.) Less successful candidates also determined the prostatic changes to be likely neoplastic and thought there was primary prostatic neoplasia with metastasis to the right kidney.