I believe it is imperative that when filing a claim for service connected medical issues to call out on your 21-3148 "Statement in support of claim" form the exact code number from 38 CFR.
The following link is on the VA website: http://www.benefits.va.gov/warms/bookc.asp
This is the
4.1 - 4.31 - Subpart A - General Policy in Rating
Subpart B - Subpart B - Disability Rating
4.40 - 4.73 - The Musculoskeletal System
4.75 - 4.84a-5 - The Organs of Special Sense
4.85 - 4.87a - Impairment of Auditory Acuity
4.88 - 4.89 - Infectious Diseases, Immune Disorders and Nutritional Deficiencies
4.96 - 4.97 - The Respiratory System
4.100 - 4.104 - The cardiovascular System
4.110 - 4.114 - The Digestive System
4.115 - 4.115b - The Genitourinary System
4.116 - Gynecological Conditions and Disorders of the Breast
4.117 - The Hemic and Lymphatic Systems
4.118 - The Skin
4.119 - The Endocrine System
4.120 - 4.124a - Neurological Conditions and Convulsive Disorders
4.125 - 4.130 - Mental Disorders
4.149 - 4.150 - Dental and Oral Conditions