| p | Greek lower case letter pi; the ratio of circumference to diameter, 3.1415926536 |
|---|---|
| RAD | radial artery catheter; radiation absorbed dose; radical; radiography or radiographic; reactive airw... |
| RVEDD | right ventricular end-diastolic diameter |
| TCD | tapetochoroidal dystrophy; T-cell depletion; thermal conductivity detector; tissue culture dose; tra... |
| THD | Thomsen disease; transverse heart diameter |