Veterinary Clinical Medicine-I (General and Systemic)

Concepts of diferential diagnosis

CONCEPT OF DIFFERENTIAL DIAGNOSIS

• In Veterinary Medicine, differential diagnosis (abbreviated DDx, ddx, DD, or ΔΔ) is a systematic method used to identify unknowns. This method, essentially a process of elimination, is used by physicians, physician assistants, and other trained medical professionals to diagnose the specific disease in a patient.
• Not all veterinary medical diagnoses are differential ones: some diagnoses merely name a set of signs and symptoms that may have more than one possible cause, and some diagnoses are based on intuition or estimations of likelihood.
• Careful differential diagnosis involves first making a list of possible diagnoses, then attempting to remove diagnoses from the list until at most one diagnosis remains. In some cases, there will remain no diagnosis; this suggests the physician has made an error, or that the true diagnosis is unknown to medicine. Removing diagnoses from the list is done by making observations and using tests that should have different results, depending on which diagnosis is correct.
• In Veterinary Medicine, differential diagnosis is the process whereby a given condition or circumstance, called the presenting problem or chief complaint, is examined in terms of underlying causal factors and concurrent phenomena as discerned by appropriate disciplinary perspectives and according to several theoretical paradigms or frames of reference, and compared to known categories of pathology or exceptionality.

Differential diagnosis allows the physician to

• More clearly understand the condition or circumstance
• Assess reasonable prognosis
• Eliminate any imminently life-threatening conditions
• Plan treatment or intervention for the condition or circumstance
• Enable the patient and the family to integrate the condition or circumstance into their lives, until the condition or circumstance may be ameliorated, if possible.
• If the patient's condition does not improve as anticipated when the treatment or therapy for the disease or disorder has been applied, the diagnosis must be reassessed.
• The method of differential diagnosis is based on the idea that one begins by first considering the most common diagnosis first: a head cold versus meningitis, for example. As a reminder, medical students are taught the adage, "When you hear hoofbeats, don't look for zebras," which means look for the simplest, most common explanation first. Only after the simplest diagnosis has been ruled out should the clinician consider more complex or exotic diagnoses.
• At one time doctors ordered only particular blood tests, but now a full blood chemistry profile is standard, which can speed up the process of diagnosis as well as uncover sub-clinical conditions.
• With the advent of better radiological studies like MRI and the wider use of nuclear medicine, it has become more likely that unexpected findings will emerge and will be further studied, though such findings may not be supported by further investigation.
• Such findings are a valuable tool but not infallible; often it still takes a veterinary physician or veterinary medical team to track down either a more common illness with a rare presentation or a rare illness with symptoms suggestive of many other conditions. Sometimes a definitive diagnosis might take years.