QUESTIONS

1. There are many not particularly specific clinical signs associated with pheochromocytoma.  Here are some:
   
   panting
   weakness
   tremors
   restlessness
   PU/PD
   neuro signs (ataxia, seizures)
   epitstaxis
   flushing of pinnae
   diarrhea
   retinal hemorrhage
   
   Many of these signs are from direct catecholamine effects but others are secondary to a direct catecholamine effect.
    
2. Clinical signs are usually (choose one) continuous or paroxysmal in pheochromocytoma.
    
3. In 1/3 of all cases a tumor thrombus has invades where?
    
4. Why do dogs with pheochromcytoma get hemoconcentration?
    
5. Why is there are neutrophilia in 50% of pheochromocytoma cases?
    
6. How is pheochromocytoma diagnosed?
    
7. How is pheochromocytoma treated?
    
8. Normally, after surgery, there is a drop in blood pressure.  What does it mean if there isn't?
   
   
   
   
    

ANSWERS

1. Catecholamines cause hypertension which leads to neuro signs, epistaxis, flushing of pinnae, retinal hemorrhage.
   
   
   
   
    
2. Signs are usually paroxysmal & the dog is normal between episodes.  Signs don't have to be paroxysmal though, they can be continuous.
   
   
   
   
    
3. In 1/3 of cases, a tumor thrombus invades the postcava where it causes complete or partial obstruction. :(
   
   
   
   
    
4. No one knows why there is hemoconcentration.  It is suspected that the tumor produces an erythropoietin-like factor.  This can be masked by anemia of chronic disease, though.
   
   
   
   
    
5. Catecholamines cause the demargination of neutrophils.  Note, this is one of the paroxysmal signs so you might not find it.
   
   
   
   
    
6. Serum catecholamine levels can be elevated from pre-venipuncture anxiety so you might catch them elevated in a normal patient.  It's better to run urine catecholamines as it is easier to find an elevations.  Most labs do not run these tests and a 24 hour urine collection is needed.
   
   A more dangerous test is the phentolamine suppression test.  The theory is that an alpha adrenergic blocker will drop blood pressure by blocking alpha (vasoconstrictor) effects of catecholamines if they are present.  This test only works in hypertensive animals.  A positive test shows a drop in blood pressure of at least 35 torr for at least 4 min.  Keep an alpha agonist & fluids ready.
   
   
   
   
    
7. Surgery is the treatment of choice but the blood pressure has to be stabilized first. If the tumor is inoperable, you can try medical therapy (phenoxybenzamine - an alpha blocker & propranolol - a beta blocker)
   
   
   
   
    
8. If you don't get a drop in blood pressure post-op, there is probably tumor left behind :(