It is difficult, if not impossible, to explain exactly how 'we do what we do' when we take care of patients. The mental processes used by clinicians for patient assessment, diagnosis formulation, diagnostic testing, treatment selection, and outcome prediction are complex and influenced by knowledge, logic, experience, intuition, and circumstance. Although the medical thought process does not lend itself to ready analysis, it is nevertheless a fascinating exercise to try to understand how clinicians think. The purpose of this lecture is to enhance awareness of how the science of medicine informs the art of medicine by analyzing and attempting to understand decisions--good and bad--made by clinicians working-up real life clinical cases.
Case #1. The Instant Diagnosis
A 7-yr old, spayed female cat with dermatitis is presented to the veterinarian for a third opinion. The dermal changes developed several months ago and have gradually worsened. The progression of dermatitis has been accompanied lately by weight loss and diminished appetite. Treatments with several courses of antibiotics, glucocorticoids, and topical therapies recommended by two other veterinarians have resulted in temporary improvement but have failed to resolve the problem. In fact, the condition has progressed despite the attempts at therapy. After a brief examination, the veterinarian renders the correct diagnosis.
Case #2. The Inadvertent Discovery
A 12-yr old, female poodle is evaluated prior to an elective dental procedure. The owner reports that the dog is in good health and had no specific complaints. The physical examination is unremarkable except for mild dental disease. A pre-anesthetic laboratory evaluation reveals a modest elevation in serum alkaline phosphatase (ALP). The veterinarian recommends an ultrasound examination to follow-up the abnormal liver value. Abdominal ultrasound examination reveals multiple nodules scattered throughout the hepatic parenchyma and a solitary splenic nodule. The remainder of the ultrasound examination is unremarkable.
Case #3. A Shaky Step
A 6-yr old, spayed female terrier is presented for acute onset of vomiting and diarrhea. Twelve hours prior to becoming ill the dog had escaped its pen and roamed the neighborhood for several hours prior to returning home. At examination, the dog is lethargic and dehydrated. Abdomen palpation elicits mild discomfort and reveals fluid filled bowel loops. Laboratory findings showed pre-renal azotemia and mild hyponatremia and hypochloremia. An ACTH stimulation test showed elevated baseline and 1-hr stimulated cortisol levels. Results of abdominal radiography are consistent with gastroenteritis. An abdominal ultrasound was performed to evaluate the pancreas. The ultrasound examination found no evidence of pancreatitis but a 1-cm diameter mass on the cranial pole of the right adrenal gland was detected. The dog showed a complete response to conservative therapy that included an anti-emetic, intestinal motility modifier, and fluid therapy and was discharged from the hospital 2 days later.
One week later the dog returned to the hospital for re-evaluation. The owner reported resolution of all clinical signs and noted that the dog was active and had a good appetite. The physical examination was unremarkable. The laboratory evaluation showed resolution of the previously noted abnormalities and was completely unremarkable. The dog was admitted to the hospital for further evaluation of the adrenal mass. A repeat ACTH stimulation test was normal. A pre-operative CT (computed tomography) examination of the abdomen suggested that the adrenal tumor did not invade local vascular structures. Adrenalectomy was recommended. Complications developed during surgery and the dog died 12 hrs later.
Case #4. The Crystal Ball
A 3-yr old, male Springer spaniel presents with an acute onset of vomiting and abdominal distention. The owner discovered the dog after returning home from some errands and reports the dog was completely normal several hours earlier. Physical examination reveals that the abdomen is tympanic and painful and there is evidence of hypovolemia and shock. Gastric dilatation-volvulus (GDV) is suspected and confirmed by radiography. The owner agrees to the recommended treatment, including surgery. However, the pre-surgical evaluation shows that the plasma lactate concentration is 6.6 mmol/L, which is above the level (plasma lactate >6.0 mmol/L) that is associated with severe gastric necrosis and poor survival in dogs with GDV.