- Bilirubinuria 791.4
- Biliuria 791.4
- Billroth's disease
- Bilobate placenta - see Placenta, abnormal
- Bilocular
- Bing-Horton syndrome (histamine cephalgia) 339.00
- Binswanger's disease or dementia 290.12
- Biörck (-Thorson) syndrome (malignant carcinoid) 259.2
- Biparta, bipartite - see also Imperfect, closure
- Bird
- Bird's disease (oxaluria) 271.8
- Birt-Hogg-Dube syndrome 759.89
- Birth
- Birthmark 757.32
- Bisalbuminemia 273.8
- Biskra button 085.1
- Bite(s)
- Biting
- Black
- Blackfan-Diamond anemia or syndrome (congenital hypoplastic anemia) 284.01
- Blackhead 706.1
- Blackout 780.2