When mud-phuds do a PhD in a scientific field completely unrelated to the clinical field they enter. Or rather, to be temporally accurate, when they enter a specialty that is completely unrelated to the science in their PhD, even when they had lots of success in said PhD. I have to wonder, is it a waste of time? On one hand, grad school is about learning how to do science and the fundamental skills and mindset required for doing science is applicable to all fields. Further, basic science is well-respected and having a track record of basic science experience will look good when applying to residencies and perhaps grants during residency/post-doctoral years. Plus, it’s common for science people (non-clinical) to switch fields after their PhD. It’s your post-doc that really determines the field that your career falls in. Finally, you get a free med school education. On the other hand, if you’re going to get clinical training (residency) and you want to be a true physician-scientist, your future career’s research field will likely be related to your clinical field. Then all the specific knowledge from your PhD would be irrelevant and, if not irrelevant, obsolete by the time you finish clinical training. You could have instead devoted those 4-6 years doing a relevant post-doc that sets a firm foundation for your first independent grants.
I was reminded of this thought recently when I read of this recently graduated MD/PhD student from WashU who had seemingly amazing success: in 8 years, got her dual degrees and published TWO first/co-first-author papers in Nature, a first-author paper in J Exp Med, and middle author papers in Nature, Nat Immunol, J Exp Med, and Mol Cell, plus a review. These are in the field of immunology and I guess, since they deal with DNA damage and repair, heme/onc. What is one field that has nothing to do with lymphocytes? She matched to general surgery at Vandy. I’m sure she has a good reason; I am very curious.
Anastomosed 
MD/PhDs have found niches in a few of the general surgery subspecialties, most notably transplant, surg onc and pediatric surg. Perhaps this resident has plans to pursue one of these research heavy sub-specialties? Pediatric surgery, in particular, requires a beefy CV and non-MD/PhD’s are often required to do research fellowships before applying for a pediatric fellowship.
[Also, an interesting anecdote: One of our immunology PhD’s once said “the best immunologists you’ll find in the hospital are transplant surgeons.”]
Ah yes, I forgot about transplant surgery.