In way of explanation for those who don’t encounter such terms regularly, differential diagnosis (a.k.a. Ddx) is the process of distinguishing between multiple possible disease processes that may be causing a particular sign or symptom. The term “differential” is sometimes used as shorthand notation to refer to the list of possible diagnoses.
Working through a differential diagnosis is one of the most challenging and delightful parts of medicine. To be done well, it requires a combination of art, science, and intimate knowledge of the patient’s story, their medical history, and available data.
Despite this personalized aspect, there is a framework of differential diagnosis that is brought to bear when approaching any particular patient. For instance, Harrison’s Principles of Internal Medicine organizes the entire second section of the book (chapters 11 through 60) according to “clinical manifestations and presentations of disease.” The goal of each chapter is to explain the approach to differential diagnosis of a particular symptom or set of related symptoms. The differential diagnosis of abdominal pain is a classic example.
Should we allow questions that ask for a list of possible causes given some known information or not?
I don’t think there is a Yes | No answer that will apply to every question. These fall into a couple categories:
Too broad: I do indeed think many of these are too broad.
Too personal: Frequently, in order to make a question more specific, one needs to provide a few details.
- I have abdominal pain that started 18 hours ago when it was intermittent, located in the mid-abdomen, and accompanied by anorexia. The pain has now shifted to the right lower quadrant and is constant, worse with movement, and more severe. I have also developed nausea and vomiting. What is my diagnosis?
This, I think, falls into the category of personal medical advice and is off topic for that reason.
- What types of things cause abdominal pain that occurs consistently after eating?
This has a reasonably scoped differential diagnosis, and I can imagine an answer that outlined a few basic mechanisms of what might cause this pattern and gave the primary diagnostic possibilities.
Note: If this were phrased, “I have abdominal pain after I eat. What is my diagnosis?” it shifts it from category 3 into category 2. Although it’s only a difference in phraseology, I think we need to use language here that reminds us all that we do not make personal diagnoses.