LOCATION
Level with the 1st posterior sacral foramen, 1.5 cun lateral to the medial sacral crest.
Features
Back-Shu point of small intestine.
Body Inches (cun)
Each person has his/her own personal body inches.
One cun is equal to the width of the Knuckle of the thumb.
Nerves, vascular
The lateral branch of the posterior branch of the first sacral nerve and the posterior branch of the lateral sacral artery and vein.
Indication
Enteritis，diarrhea，constipation；enuresis，spermatorrhea；pelvic inflammatory disease，uterus meningitis；sacroiliac arthritis，hemorrhoids. Main point for all Small Intestine related issues: damp heat effecting the bladder (difficult or painful urination, hematuria, dark urine), damp heat effecting the intestines (diarrhea, dysentary).
Combinations
Enteritis，diarrhea，diarrhea：BL 27 & SP 15 & ST 39.
Spermatorrhea，enuresis：BL 27 & CV 04 (Combining Shu/transport and Mu/alarm points)
Lower back pain，colic：BL 27 & BL 29 & BL 30
Constipation，difficulty in urination ， abnormal urination：BL 27 & GV 01.
Rheumatoid arthritis：GV 14 & BL 20 & BL 23 & BL 27 & EX-B 2 of corresponding segments and the meridian points on affected areas.
穴位
在骶部，當骶正中嵴旁1.5寸，平第一骶後孔。
特點
小腸之背俞穴。
同身寸
針灸取穴比量法。出自《千金要方》。
是指以患者本人體表的某些部位折定分寸，
作为量取穴位的長度單位。
穴區神經血管
第一骶神經後支的外側支和骶外側動、靜脈後支。
適應症
腸炎，痢疾，便秘；遺尿，遺精；盆腔炎，子宮內膜炎；骶髂關節炎，痔瘡。
穴位配伍療法
腸炎，泄瀉，痢疾：1.小腸俞 2.大橫 3.下巨虛
遺精，遺尿：1.小腸俞 2.關元 (俞募配穴法)
腰脊疝痛：1.小腸俞 2.中膂俞 3.白環俞
大小便難、淋癃：1.小腸俞 2.長強
類風濕脊椎炎：1.大椎 2.脾俞 3.腎俞 4.小腸俞 5.相應夾脊