Major Diagnostic Categories (MDCs) and their MS-DRGs

25 body systems under V44.0, with Pre-MDC first because the grouper tests those classes before it assigns an MDC at all. Each page lists its MS-DRGs with surgical classes in hierarchy order.

MDC	Category	Surgical	Medical
00	Pre-MDC Not a body system	19	4
01	Diseases and Disorders of the Nervous System	23	49
02	Diseases and Disorders of the Eye	5	5
03	Diseases and Disorders of the Ear, Nose, Mouth and Throat	11	14
04	Diseases and Disorders of the Respiratory System	7	34
05	Diseases and Disorders of the Circulatory System	64	35
06	Diseases and Disorders of the Digestive System	30	28
07	Diseases and Disorders of the Hepatobiliary System and Pancreas	21	15
08	Diseases and Disorders of the Musculoskeletal System and Connective Tissue	72	34
09	Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast	16	16
10	Endocrine, Nutritional and Metabolic Diseases and Disorders	17	9
11	Diseases and Disorders of the Kidney and Urinary Tract	26	16
12	Diseases and Disorders of the Male Reproductive System	12	9
13	Diseases and Disorders of the Female Reproductive System	14	8
14	Pregnancy, Childbirth and the Puerperium	15	8
15	Newborns and Other Neonates with Conditions Originating in Perinatal Period	0	7
16	Diseases and Disorders of Blood, Blood Forming Organs and Immunologic Disorders	6	9
17	Myeloproliferative Diseases and Disorders, Poorly Differentiated Neoplasms	12	16
18	Infectious and Parasitic Diseases, Systemic or Unspecified Sites	6	11
19	Mental Diseases and Disorders	1	8
20	Alcohol or Drug Use or Induced Organic Mental Disorders	0	4
21	Injuries, Poisonings and Toxic Effects of Drugs	9	11
22	Burns	3	3
23	Factors Influencing Health Status and Other Contacts with Health Services	3	7
24	Multiple Significant Trauma	5	3
25	Human Immunodeficiency Virus Infections	2	4

Pre-MDC occupies an MDC number without being a diagnostic category, which is why a count of 26 overstates how many body systems exist. On a grouped claim the API reports the principal diagnosis's own MDC even for a pre-MDC DRG, so a heart transplant can come back as MDC 05.