Heuristics are a simplified approach to medical decision-making that focuses on using specific, pertinent data points and discounting other available information in order to streamline choices around diagnostic testing, therapy, and other aspects of case management. Relying on these medical shortcuts can help simplify complex decisions and prevent feelings of overwhelm. Heuristics can be especially valuable in emergent situations when prompt intervention may be the difference between life and death.
Although a heuristic approach can be useful and accurate, especially when employed by an experienced clinician, medical errors are possible. Making a presumptive diagnosis too quickly may lead to ignoring information that supports the true diagnosis. Heuristics may also be misleading in patients with atypical presentation of a common disorder. Further, personal experience may trigger conscious and unconscious biases.
For the following cases, consider how heuristics impact your approach to practice.
The Case: Vomiting in a Dog Following Chewing Gum Exposure
Genevieve, a 6-year-old spayed standard poodle, is presented for vomiting and lethargy.
History
Genevieve was found lethargic and recumbent on the kitchen floor by her owner, along with multiple piles of vomit and a spilled container of sugar-free gum. Three pieces of gum out of a 40-piece container were found, but the owner does not remember how full the container was at the time of the incident. Genevieve is the only animal in the home, is up-to-date on preventive care, and has a history of a sensitive stomach (according to the owner).
Physical Examination
On physical examination, Genevieve is in sternal recumbency with dull mentation. BCS is 4/9, and she has lost 1.1 lb (0.5 kg) compared with examination 3 months prior. Temperature is 98.6°F (37°C), heart rate is 75 bpm, and respiratory rate is 24 breaths per minute. Gums are pale pink, and capillary refill time is >2 seconds. Spot-check blood glucose is 45 mg/dL.
Diagnostics
Fluid therapy is immediately started to address signs of shock and dextrose is given for hypoglycemia while waiting for additional in-clinic test results.
Initial test results reveal potassium of 5.8 mEq/L (5.8 mmol/L; reference interval, 3.8-5.4 mEq/L [3.8-5.4 mmol/L]), sodium of 132 mEq/L (132 mmol/L; reference interval, 145-154 mEq/L [145-154 mmol/L]), BUN of 35 mg/dL (reference interval, 10-28 mg/dL), creatinine of 2.3 mg/dL (reference interval, 0.5-1.4 mg/dL), and nonregenerative anemia with a normal leukogram. Urine specific gravity is 1.007.
Although the possible sugar-free gum exposure and clinical signs, especially hypoglycemia, are consistent with xylitol toxicosis, patients with this condition are more likely to have hypokalemia. Hyperkalemia and hyponatremia in this patient indicate the need for additional diagnostics.
Outcome
The owner learned from another family member that the gum container was nearly empty, and Genevieve likely did not ingest any pieces.
To find out more about diagnosing and treating dogs with hypoadrenocorticism, read Managing Canine Addisonian Crisis by Marc A. Seitz, DVM, DACVR, DABVP.
The Case: Nasal Lesions in an Akita
An over-the-counter emollient balm has been applied by the owner, but there has been no improvement. Smoky lives in the home with a geriatric Chihuahua (with little contact) and is up-to-date on preventive care. The owner notes that Smoky frequently digs in the yard.
Physical Examination
On physical examination, Smoky is bright, alert, and responsive. BCS is 5/9. Vital signs are normal. Patchy depigmentation is seen on the nasal planum, with mild to moderate crusting along the dorsal aspect. There are several pustules, mild hair loss, and an erosion around the junction between the skin and the nasal planum.
Diagnostics
Smokey’s owner has a limited budget and cannot afford all the recommended diagnostics.
Although this patient’s breed and lesions could be indicative of pemphigus foliaceus, the history of digging indicates potential for an infectious cause.
Treatment
Definitive therapy, including systemic administration of terbinafine, was initiated.
For more information on nasal planum conditions, check out Nasal Planum Disease in Dogs by Darren Berger, DVM, DACVD.
The Case: Red Eye in a White Cat
Misty, a 9-year-old spayed domestic medium hair cat, is presented for a second opinion for chronic conjunctivitis of 1-month duration.
History
On initial presentation, the owner noted the lower left eyelid appeared red and raw. The primary care clinician had diagnosed a herpes virus infection and prescribed a neomycin/polymyxin b/bacitracin ointment, but the eye has worsened in appearance. The owner is unsure what, if any, diagnostic tests were performed. The owner notes that Misty previously had a red, swollen lower lip with occasional sores that disappear and reappear. Misty is an indoor-only cat, up-to-date on preventive care, and the only animal in the home.
Physical Examination
On physical examination, Misty is bright, alert, and responsive. BCS is 6/9. Vital signs are normal. Abnormal findings include increased body condition score; a swollen, erythematous, hairless area of ≈1 cm on the lower lip; and an ulcerated area of the lower left eyelid that extends ≈5 mm laterally from the medial canthus. The third eyelid is partially elevated, and there is a small amount of mucoid ocular discharge.
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Diagnostics
Her owner states that Misty can be uncooperative for veterinary care but cannot return for a sedated visit until the next week.
All the recommended tests were completed between this examination and a second, sedated examination. Schirmer tear test was normal. Fluorescein eye stain and PCR testing were negative. Cytology was equivocal, but no eosinophils were found.
Misty’s eye has gotten worse. The third eyelid is persistently elevated, the eyelid appears more enlarged compared to the previous visit, and she has started pawing at the eye.
Although patient history and presence of lip lesions may indicate eosinophilic disease, lack of eosinophils on cytology suggests additional diagnostics are needed.
Outcome
Misty was referred to a specialty facility for more definitive resection and adjunctive therapy as indicated. For more on causes of eyelid inflammation in dogs and cats, read Eyelid Inflammation in Cats & Dogs by Georgina M. Newbold, DVM, DACVO.
Being an excellent veterinary diagnostician depends on a solid foundation in the basics. In this General Practice Skills series, we’ll tackle a different skill critical to daily practice: history-taking, making a master problem list, compiling differentials, and utilizing heuristics/patterns.