After reading the article describing John Merrill's accomplishments, it is hard to think of a better candidate, as he could be considered the father not only of dialysis but also of kidney transplant:
1. "Father of Dialysis"--although Kolff is credited for building the first usable dialysis machine, an improved and more practical device built at Peter Bent Brigham Hospital ("the Kolff-Brigham Kidney") was necessary for dialysis to be routinely used in the treatment of renal failure. John Merrill was the leader of the clinical team which determined how to use dialysis effectively and served as a major advocate for the use of dialysis at a time when the procedure was considered controversial and even harmful.
2. "Father of Kidney Transplantation"--the first successful kidney transplant occurred between identical twins (the Herrick brothers--pictured above--Merrill is in the middle of the back row) at Peter Bent Brigham Hospital, and John Merrill was the head of the nephrology team which allowed this to happen. Merrill was convinced that previous failures of kidney transplant were not due to surgical complications or any problem inherent to the exchange of organs between individuals, but rather due to immunologic incompatibilities. The success of this transplant between genetically-identical individuals proved that this was true, and Merrill's later studies with irradiation of the immune system provided the basis for expanding the world of kidney transplant beyond that of the rare case of identical twins.
In addition, Merrill's contributions also included an increased awareness that the treatment of hypertension is important (not a trivial feat, as hypertension was for many years considered by many to be an appropriate "compensatory response" to cardiovascular or renal disease) and the furthering of nephrology as a defined academic subspecialty. Amazingly, he also served as the in-flight medical officer for the Enola Gay (the airplane which dropped the atomic bomb on Japan during WWII) prior to his studies at the Brigham Hospital.