BL-32 (Ci Liao) Second Bone Hole

What does BL-32 Ci Liao do?

Ci Liao BL-32 is the second of the four sacral foramen points on each side — the baliao or "eight bone holes" — and it is the one of the four most used in modern practice. Its defining feature is anatomical rather than theoretical: the point lies over the second posterior sacral foramen, an actual opening in the sacrum through which the posterior branch of the second sacral nerve emerges. Sacred Lotus sources & references also record it as a Meeting Point of the Bladder and Gall Bladder channels.

• Regulates the lower jiao and facilitates urination and defecation — the headline recorded action, and the reason the sacral points dominate the acupuncture literature on bladder and bowel dysfunction.
• Regulates menstruation and stops leucorrhoea — its gynaecological side: irregular and painful periods, and abnormal vaginal discharge.
• Benefits the lumbar region and legs — for low back and sacral pain, and for weakness, numbness or pain running down the lower limb.
• Reaches the pelvic organs from behind — the practical consequence of all three. Where the lower-abdominal points approach the bladder and uterus from the front, BL-32 approaches the same organs from the back, which is why front-and-back combinations of the two are recorded.

One point about how these actions are framed. BL-32 is not a Back-Shu point, and it should not be described as one — it is not among the paired points beside the spine that carry an organ's name. Its influence over the pelvic organs comes from its position over the sacral foramen and from the record of its clinical use, and that is a different and more literal kind of claim.

Source: Sacred Lotus sources & references (recorded actions and the Meeting Point classification); Deadman & Al-Khafaji, A Manual of Acupuncture, p. 293; Chinese Acupuncture & Moxibustion, p. 182; cross-referenced against multiple online sources.

What is BL-32 Ci Liao used for?

Ci Liao BL-32 is used for the urinary, gynaecological and lumbosacral complaints of the pelvis — and in modern practice above all for period pain and for pain in labour. Sacred Lotus sources & references record dysmenorrhoea and leucorrhoea as its practical heading. The indications below are those documented in the standard reference literature and describe traditional use, not proven treatment.

• Dysmenorrhoea (painful periods)
• Irregular menstruation
• Leucorrhoea (abnormal vaginal discharge)
• Low back and sacral pain
• Difficult or painful urination (dysuria)
• Enuresis (bed-wetting)
• Retention of urine
• Nocturnal emission
• Impotence
• Hernial disorders
• Constipation
• Muscular atrophy of the lower limb
• Pain, numbness and impaired movement of the lower extremities
• Pain in labour, in modern obstetric use

Source: Sacred Lotus sources & references (existing indication and use records); Deadman & Al-Khafaji, A Manual of Acupuncture, p. 293; Chinese Acupuncture & Moxibustion, p. 182.

How is BL-32 Ci Liao used in practice?

Ci Liao lies on the sacrum — the triangular bone at the base of the spine — directly over the second of the four paired openings in its back surface, a little below and inside the bony prominence at the back of the pelvis that can be felt through the skin. It is the second member, counting downward, of the set of eight liao points, and it is the one practitioners reach for first when the sacral group is indicated. Sacred Lotus sources & references record its practical heading as dysmenorrhoea and leucorrhoea.

• Within the eight liao. All four levels are held in this library: Shang Liao BL-31 (Upper Bone Hole) at the first foramen, Ci Liao BL-32 (Second) at the second, Zhong Liao BL-33 (Central) at the third and Xia Liao BL-34 (Lower) at the fourth, each recorded here with the same Meeting Point classification and the same recorded needling range. They are frequently used as a block, often with two or four needles a side; where a single level is chosen, BL-32 is the usual one.
• For dysmenorrhoea. The classical pairing is local and distal — BL-32 on the sacrum with San Yin Jiao SP-06 on the inner lower leg, and often Di Ji SP-08, the Xi-Cleft point of the Spleen, which is the acute-pain choice for severe period pain. Front-and-back combinations with Zhong Ji REN-03 and Gui Lai ST-29 reach the same organs from the opposite side.
• For urinary complaints. With Pang Guang Shu BL-28, the Back-Shu point of the Bladder, which lies just above and lateral at the same level as the second sacral foramen; with Zhong Ji REN-03, the Bladder's Front-Mu point; and with Hui Yang BL-35 at the very bottom of the sacrum, the partner point in much of the modern clinical research.
• For the low back and leg. With Wei Zhong BL-40 behind the knee — the classical command point of the back — with Shen Shu BL-23, and with the extra point Shi Qi Zhui Xia below the seventeenth vertebra, all of which are held here.
• In labour. Firm pressure over the sacrum during contractions is the oldest and simplest use of this point, and it is the form in which BL-32 has actually been tested. Acupressure at BL-32 needs no needles and no clinical setting, which is why the obstetric trial literature on this point is unusually large for a single acupuncture point.
• Method. Moxibustion is recorded as applicable. Electroacupuncture across a pair of sacral points is the technique used in most of the modern urological research.

A survey of 160 clinical papers on the eight liao points gives a fair picture of what they are actually used for in contemporary Chinese practice: 43.8 per cent of the reports concerned urinary disorders, 21.3 per cent gynaecological ones, 14.4 per cent proctological ones and 10.0 per cent disorders of the musculoskeletal system, with post-stroke urination disorder, neurogenic bladder after spinal injury, dysmenorrhoea and constipation the four most-reported individual conditions (Zhongguo Zhen Jiu 2019;39(1):96–102, PMID 30672264).

Source: Sacred Lotus sources & references (recorded uses, categories and the point records cross-referenced above); Deadman & Al-Khafaji, A Manual of Acupuncture, p. 293; Chinese Acupuncture & Moxibustion, p. 182; PMID 30672264; cross-referenced against multiple online sources.

Where is BL-32 located?

• A Manual of Acupuncture (p. 293): Over the second posterior sacral foramen.
• Chinese Acupuncture and Moxibustion (p. 182): On the sacrum, medial and inferior to the posterosuperior iliac spine, just at the second posterior sacral foramen.

How is BL-32 Ci Liao needled, and what is different about a sacral foramen point?

Reference fact, and the thing that makes this point unusual: the needle at BL-32 is documented as entering a hole in the bone. The sacrum has four paired openings on its back surface, and BL-32 sits over the second of them. Almost every other point in the body is defined against soft tissue or a bony edge; here the target is a foramen, and whether the needle enters it or strikes the bone beside it is the difference between the technique the texts describe and a needle that has simply stopped. That is why the sacral points have a measurement literature of their own. Everything below records what the textbooks and published anatomical studies document. It is not instruction, and this page does not teach technique.

The angle and depth the texts record

• Sacred Lotus sources & references record perpendicular insertion of 0.8 to 1.2 inches, with moxibustion applicable — the same figure held here for BL-31, BL-33 and BL-34.
• Deadman & Al-Khafaji (p. 293) and Chinese Acupuncture & Moxibustion (p. 182) record insertion at the second posterior sacral foramen in a comparable range, with the needle directed into the foramen.
• Moxibustion is recorded as applicable.

The foramen, measured

The most precise data available on this point comes from a retrospective study of 100 prone pelvic CT scans, reconstructed in three dimensions, which measured the angle and depth at which a needle follows the axis of each sacral foramen. It found that the sacral foramina run obliquely — downward and inward — so that a needle following the channel of the foramen is not perpendicular to the skin. The measured optimum values were:

• Angle to the skin surface at BL-32: 57.57 ± 10.01 degrees (BL-31 61.04 ± 12.15°, BL-33 58.25 ± 8.69°, BL-34 54.39 ± 10.94°).
• Angle to the posterior midline at BL-32: 18.58 ± 7.76 degrees (BL-31 24.54 ± 6.21°, BL-33 17.36 ± 7.90°, BL-34 30.73 ± 9.45°).
• Effective depth at BL-32: 44.57 ± 11.55 mm, defined as the thickness of the soft tissue over the sacrum plus half the depth of the sacrum. The four levels decrease steadily from top to bottom — BL-31 58.16 ± 12.43 mm, BL-32 44.57, BL-33 33.96 ± 10.74, BL-34 31.13 ± 10.94 mm — and the depth correlated positively with body mass index but not with sex or with weight alone (Zhen Ci Yan Jiu 2017;42(6):537–41, PMID 29318863).

Those figures are worth reading beside the textbook range rather than instead of it. The 0.8–1.2 inch perpendicular figure recorded in the general reference texts describes the ordinary insertion; the CT measurements describe the deep oblique technique used in specialist practice, in which a longer needle follows the foramen toward the sacral nerve. The two are different procedures and the numbers are not interchangeable. Chinese clinical writing on the deep baliao method states this openly — that the effect its practitioners claim depends on deep insertion through the foramen with long needles, that the angle must be adjusted to the shape of each foramen, and that the descriptions of location and manipulation in both ancient and modern literature are vague enough to have restricted the technique's use (Zhongguo Zhen Jiu 2014;34(3):285–8, PMID 24843976).

Whether the point is actually found is measurable

A 2025 randomised study of 52 patients with urinary retention after spinal cord injury addressed the question directly: both groups received electroacupuncture at BL-32 and BL-33, but in one the foramina were located first by ultrasound. The ultrasound-guided group did significantly better on lower urinary tract symptom scores, urination frequency, urine volumes and residual urine, and the authors reported a correlation between how accurately the points were located and the size of the effect (Zhen Ci Yan Jiu 2025;50(10):1169–1177, PMID 41116990). It is a single-centre trial of modest size, and the ultrasound arm cannot be blinded — but the finding is directly on the anatomical particularity described above.

What the recorded hazards at this point are, and are not

• The relevant structures are nerves, not organs. The second posterior sacral foramen transmits the posterior ramus of the second sacral spinal nerve. The sacrum itself separates the point from the pelvic cavity, so the visceral-injury concern that governs the abdominal points is not the governing concern here; the recorded phenomena at the sacral points are electric or radiating sensation down the leg, and local soreness.
• Depth varies with the person. The CT study above found effective depth correlated with body mass index; the wider literature reaches the same conclusion generally. Two systematic reviews of safe needling depth — 33 studies in one, 47 in the other, measured by MRI, CT, ultrasound and cadaveric dissection — concluded that measured depths for the same point differ greatly between subject groups and between measuring methods, and that "safe depth" has never been standardised (J Altern Complement Med 2011;17(3):199–206, PMID 21417806; Evid Based Complement Alternat Med 2013;2013:740508, PMID 23935678).
• Pregnancy. The sacral points are among the groups the classical literature lists as contraindicated or requiring caution during pregnancy, on the same reasoning as the lower-abdominal points: they act on the uterus. This sits alongside the fact that BL-32 is one of the points most used during labour, when that objection no longer applies — the same property that makes it forbidden in pregnancy is what recommends it at term. The modern evidence for actual harm at the traditionally forbidden points is weak: a review of the scientific literature found no objective evidence of harm across 15 clinical trials (823 women), a cohort of 5,885 pregnant women, and animal work (Carr DJ, Acupunct Med 2015;33(5):413–9, PMID 26362792). The traditional caution nonetheless stands in the texts and is observed in practice.
• Risk in proportion. A meta-analysis of prospective clinical studies estimated serious acupuncture-related adverse events at approximately 1 per 10,000 patients, with about half of all recorded events being bleeding, pain or flare at the needle site (Bäumler P et al., BMJ Open 2021;11:e045961, PMID 34489268).

Source: Sacred Lotus sources & references (existing needling record); Deadman & Al-Khafaji, A Manual of Acupuncture, p. 293; Chinese Acupuncture & Moxibustion, p. 182; PMID 29318863; PMID 24843976; PMID 41116990; PMID 21417806; PMID 23935678; PMID 26362792; PMID 34489268 — each verified resolvable and checked for retraction status before citation.

What does the name Ci Liao mean?

Ci Liao means "Second Bone Hole" — ci, second or next in order, and liao, a hole or crevice in bone. The name is a plain anatomical instruction: the second of the holes. It belongs to a set of four on each side, named simply by position — Shang Liao BL-31 (Upper Bone Hole), Ci Liao BL-32 (Second Bone Hole), Zhong Liao BL-33 (Central Bone Hole) and Xia Liao BL-34 (Lower Bone Hole) — and collectively, because there are four a side, they are called the baliao, the "eight bone holes". All four are held in this library.

The character liao is not peculiar to the sacrum. It appears across the body wherever a point is named for a hollow or depression in bone, and this library holds a dozen such points: ST-03 Ju Liao (Great Bone Hole) on the face, LI-19 He Liao (Grain Bone Hole), SI-18 Quan Liao (Cheek Bone Hole), SJ-22 He Liao (Harmony Bone Hole) and DU-25 Su Liao (White Bone Hole) on the head; LI-12 Zhou Liao (Elbow Bone Hole) on the arm; SJ-14 Jian Liao (Shoulder Bone Hole) and SJ-15 Tian Liao (Celestial Bone Hole) on the shoulder; and GB-29 Ju Liao (Squatting Bone Hole) at the hip. Recognising liao as "hole in bone" turns a dozen otherwise opaque names into descriptions of where to look.

Why does the sacral foramen matter?

Because it is one of the few places in acupuncture where the traditional location and the modern anatomical target coincide exactly. The sacrum is a solid triangular bone, but its back surface is pierced by four pairs of openings through which the posterior branches of the sacral nerves pass; the front surface has matching openings for the anterior branches, which go on to form the nerve supply of the bladder, the bowel and the reproductive organs. BL-32 is defined as lying over the second of the posterior openings. That makes it, uniquely among the classical points, a point whose position is fixed by a hole in a bone rather than by a soft-tissue landmark or a proportional measurement — and it explains why the effects recorded for it are pelvic-organ effects rather than the segmental back effects of the Back-Shu points beside it. It also explains why so much of the modern work on this point is about finding it accurately, by CT or ultrasound, which is not a question that arises at most points.

Is there research on BL-32 Ci Liao?

Yes — and unusually for an acupuncture point, several trials studied BL-32 on its own rather than inside a protocol, because sacral acupressure in labour needs no needles. The quality of that literature is another matter: the trials are small, mostly from a few centres, and controlled against ordinary care or against touch rather than against a credible sham. Represented honestly:

• Labour pain, BL-32 alone against a comparator point. A randomised controlled trial in 105 first-time mothers in the active phase of the first stage of labour compared acupressure at LI-04, acupressure at BL-32, and routine care alone, applied at three stages of cervical dilatation. Both acupressure groups had significantly greater pain reduction than the control group at every stage, and BL-32 was superior to LI-04 at the first and second interventions though not the third. No difference was found in mode of delivery or Apgar score (Complement Ther Med 2016;29:175–180, PMID 27912944). A head-to-head comparison of two named points is rare and makes this the most directly relevant trial for this record.
• Labour pain, against supportive care. A trial randomising 150 women to supportive care, BL-32 acupressure during contractions, or routine care reported significantly lower pain intensity in both intervention groups, and higher rates of normal vaginal delivery in both (94 per cent and 92 per cent) than in the control group (J Pregnancy 2014;2014:129208, PMID 25210629). A companion report from the same cohort examined anxiety and labour length (Iran J Nurs Midwifery Res 2015;20(2):239–46, PMID 25878703). Neither used a sham control, so expectation cannot be separated from effect.
• What the pooled evidence shows. A systematic review and meta-analysis of acupressure for labour pain pooled 13 randomised trials and 1,586 patients and found that acupressure added to standard care reduced pain compared with both sham acupressure and standard care alone, with the effect immediate and persisting at least 60 minutes, and shorter first and second stages of labour against untreated controls; the authors graded the evidence as moderate and called for higher-quality trials (Acupunct Med 2021;39(4):243–252, PMID 32811182). The Cochrane review of acupuncture or acupressure for pain management in labour — 28 trials, 3,960 women — reached a more cautious conclusion: no study was at low risk of bias on all domains, acupuncture may increase satisfaction with pain relief and probably reduces use of pharmacological analgesia against sham, but for most comparisons the certainty of evidence was low or very low (PMID 32032444). Both reviews cover acupressure at several points, not BL-32 alone.
• Urinary disorders — and a point that is often misattributed. The largest and best-conducted trial in this territory is a multicentre randomised trial in 504 women with stress urinary incontinence, which found greater reduction in urine leakage after six weeks with electroacupuncture than with sham (mean difference 7.4 g on the one-hour pad test; JAMA 2017;317(24):2493–2501, PMID 28655016). It is frequently cited loosely as evidence for "the sacral points". The trial protocol names the points used: BL-33 and BL-35, not BL-32 (Trials 2013;14:315, PMID 24079823). BL-33 Zhong Liao is the next foramen down and is held in this library; BL-35 Hui Yang lies at the very bottom of the sacrum and is held here too. That result belongs on those records, and it is stated here only so that a reader does not carry it across to this one.
• Dysmenorrhoea. BL-32 appears in a large share of the acupuncture prescriptions for period pain, and the literature survey cited above found dysmenorrhoea the third most-reported condition across 160 clinical papers on the eight liao points (PMID 30672264). No randomised controlled trial of BL-32 alone for primary dysmenorrhoea was located; the trial evidence in that condition is for multi-point protocols and, most extensively, for SP-06, which is reported on its own record in this library.

The fair summary is that BL-32 has genuine, if modest, point-specific human evidence in labour pain — more than most acupuncture points can claim — and that its urinary and menstrual reputation rests on classical use, on the wider baliao literature, and on trials of its neighbours rather than on trials of itself.

How does Ci Liao compare with the points around it?

BL-31, BL-33 and BL-34 are the same point at the first, third and fourth foramina; the set descends, and with it the emphasis shifts from the higher pelvic organs toward the anus and perineum, BL-34 being the lowest and the most anorectal in its recorded indications. BL-35 Hui Yang sits below the whole group beside the tailbone. Pang Guang Shu BL-28, the Back-Shu point of the Bladder, lies 1.5 cun lateral to the midline at the level of the second sacral foramen — the same level as BL-32 but on the outer line of the Bladder channel, and classified as a Back-Shu point where BL-32 is not. Bai Huan Shu BL-30 is the outer-line point at the fourth level. Above the sacrum, Shen Shu BL-23 is the Back-Shu point of the Kidneys and the point for the lumbar region proper, and the extra point Shi Qi Zhui Xia lies on the midline just above the sacrum and is strongly associated with dysmenorrhoea. All are held in this library.

Source: Sacred Lotus sources & references (name, categories, the liao-named point set and the point records cross-referenced above); Deadman & Al-Khafaji, A Manual of Acupuncture, p. 293; Chinese Acupuncture & Moxibustion, p. 182; PubMed PMID 27912944, 25210629, 25878703, 32811182, 32032444, 28655016, 24079823, 30672264, 29318863, 41116990, 24843976, each verified resolvable and checked as not retracted; cross-referenced against multiple online sources.