1) Diagnostician 2) Expert in body organs 3) Many a doctor 4) Medical specialist 5) Organ expert 6) Specialist 
A doctor who specializes in internal medicine. An internist works with adult patients to prevent, diagnose, and treat diseases without using surgery.
<specialist> A physician who is expert on the medical management of a wide variety of medical problems. ... [American term] ... (27 Sep 1997) ... 
(in-tur´nist) a specialist in internal medicine.
Type: Term Pronunciation: in-ter′nist, in′ter-nist Definitions: 1. A physician trained in internal medicine.
Internist: A physician who specializes in the diagnosis and medical treatment of adults. This specialty, called internal medicine, is dedicated to adult medicine. A minimum of seven years of medical school and postgraduate training are focused on learning the prevention, diagnosis, and treatment of diseases of adults. Subspecialties of internal med...
[n] - a specialist in internal medicine
a physician specializing in the diagnosis and nonsurgical treatment of diseases, esp. of adults.