2012 Radiology Exam - Ultrasound Case 1

HISTORY:
9 year old male, castrated DSH with ventroflexion of the neck and anorexia.  Biochemical abnormalities revealed hypokalemia, mild azotemia, mild elevation in ALT, AST, and ALP. Patient is hypertensive.

If you'd like to enlarge the video, use the 'ENTER FULL SCREEN' button on the playbar and the 'VIEW ACTUAL SIZE/VIEW FULL SIZE' button on the playbar of the full screen view to toggle scaling as needed.

PERTINENT FINDINGS/OBSERVATION:

  • Bilobed gall bladder and cytic duct tortuosity, as a variant of normal in cats.
  • Normal right adrenal
  • Left adrenal mass

Some candidates noticed that one of the lobes of the bilobed gall bladder had a slightly thicker and more hyperechoic wall than the other.  No extra points or point deductions were made for this.  Many searched for the major duodenal papilla at the end of a normal CBD.  It may be briefly visible but this was not a focus of the clip.  The caudal vena cava and aorta are normal with Doppler interrogation.  Doppler interrogation of the celiac and cranial mesenteric arteries was provided to give the candidate anatomic reference for the location of the left adrenal. 

SYNTHESIS:

  • Bilobed gall bladder, ductal tortuosity = incidental
  • Left mass-like  adrenomegaly.  

DDX:  Left adrenal neoplasia is considered most likely and is given most weight.  Functional and non-functional adenomas/carcinomas, pheochromocytomas, and less likely nodular hyperplasia were all possible considerations.  Based on history of hypokalemia and hypertension, these findings are supportive of hyperaldosteronism (Conn’s Syndrome) secondary to an adrenal tumor (adenoma or carcinoma).   Pheochromocytoma could explain the hypertension but not the hypokalemia, unless there were other diseases present (like renal disease).  
No extra credit or point deductions were made for diagnoses of cholangitis/cholangiohepatitis.  Point deductions were made for interpreting the bilobed gall bladder or tortuous cystic duct as abnormal.  Some candidates described the other GB lobe as a cystadenoma or a dilated intrahepatic bile duct.  Some candidates were very concerned about the cystic ducts tortuosity.  Some candidates suspected invasion of the left phrenicoabdominal vein by the left adrenal gland.  This observation was given little weight. Point deduction was only made if the candidate incorrectly states that there was caval/aorta invasion.  

PLAN:

  • Stabilize, then surgery (adrenalectomy) and/or medical therapy
  • Three view thorax for metastasis or CTA for tumor thrombus assessment

FINAL COMMENTS:  When this case was presented to the exam committee, I placed plenty of weight on connecting the history with the lesion to make the final diagnosis of an ALDOSTERONE secreting tumor.  The committee disagreed with me however.  We determined as a group that a general diagnosis of adrenal mass with cortical and medullary tumors (both functional and non-functional) was sufficient for most of the points.  The committee’s prediction that only few would diagnose an aldosterone-secreting tumor proved correct as only 5 of 23 candidates had this in their differential.

Most candidates passed this question. 7 candidates failed this question.  Failure was mostly based on incorrect identification of structures (adrenal glands called lymph nodes; the left adrenal called a liver, spleen, or pancreatic mass).  Another major reason for poor performance was describing a bilobed gall bladder as abnormal.