A headed flat-abscess of the back, usually on the governing dū vessel or bladder channel and attributable to stagnation in the channels and blockage of qì and blood stemming either from fire toxin brewing internally or exuberant yīn vacuity fire. Distinction is made between effusions of different locations. Effusions of the upper back are located at BL-10 (Celestial Pillar, 天柱 tiān zhù); effusions of the middle of the back are located at GV-8 (Sinew Contraction, 筋缩 jīn suō); effusions of the lower back are located at GV-4 (Life Gate, 命门 mìng mén); reachable sores of the upper back are located at BL-13 (Lung Transport, 肺俞 fèi shù); reachable sores of the middle of the back are located at BL-43 (Gāo-Huāng Transport, 膏肓俞 gāo huāng shù); reachable sores of the lower back are located at BL-23 (Kidney Transport, 肾俞 shèn shù) and BL-51 (Huang Gate, 肓门 huāng mén). See also reachable sore; welling-abscess.