Muscle:Transversus Abdominis

Transversus abdominis is the deepest of the three lateral abdominal wall muscles. Its TrPs produce referred pain in a horizontal band across the upper abdomen with concentration at the xiphoid process, and are associated with enthesitis along the inferior costal margin that is characteristically aggravated by coughing. The transversus abdominis is the first of all the abdominal wall muscles to be activated in anticipation of lower limb movement — a feedforward response that underlies its primary role in dynamic spinal stabilisation. The "belch button" TrP is closely associated with this muscle or the adjacent lumbodorsal fascia.

Anatomy

The transversus abdominis fibres run nearly horizontally around the abdomen. They attach anteriorly to the midline linea alba via the rectus sheath, which surrounds the rectus abdominis above the arcuate line, and attach to the pubis through the conjoined tendon (formed with the internal oblique) below that line. Laterally the transversus attaches to the lateral one-third of the inguinal ligament, to the anterior three-quarters of the iliac crest, to the thoracolumbar fascia, and to the inner surfaces of the cartilages of the last six ribs, where its fibres interdigitate with those of the diaphragm.

Primary action: Contraction increases intra-abdominal pressure. The transversus abdominis is the first abdominal muscle activated in anticipation of lower limb movements — a feedforward activation independent of movement direction, linked to the control of spinal stability against perturbations.

Innervation: Branches of the eighth through twelfth intercostal nerves; branches of the iliohypogastric and ilioinguinal nerves; additionally by the seventh intercostal nerve. Segmental innervation T7–L1.

Referred Pain Patterns

Craniad Fibres — Upper Abdominal Band

Active TrPs in the more cranial (upper) portion of the transversus abdominis refer pain as a band across the upper abdomen between the anterior costal margins. The distressing pain sometimes concentrates on the region of the xiphoid process.

Costal Attachment — Inferior Costal Margin Pain and Enthesitis

TrPs in the transversus fibres attaching to the lower costal cartilage are likely to cause marked enthesitis along the inferior costal margin. This becomes very distressing when coughing. Continued coughing is a potent perpetuating factor once the enthesitis is established.

The "Belch Button" TrP

The belch button may represent a transversus abdominis attachment TrP at the region of the twelfth rib angle, where the transversus attaches to the thoracolumbar fascia, or it may be a fascial TrP in the lumbodorsal fascia itself. When located by palpation, a rib is palpable beneath the examining finger. When sufficiently active it causes spontaneous belching and, in severe cases, projectile vomiting. See Muscle:Abdominal Wall/Belch Button for full clinical details.

Somatovisceral and Viscerosomatic Effects

The transversus abdominis participates in the same pattern of somatovisceral and viscerosomatic interactions as the other lateral abdominal wall muscles. Particular associations include:

• Belching and projectile vomiting (belch button TrP)
• Upper abdominal distress and bloating (upper fibre TrPs)
• Inferior costal margin pain aggravated by coughing (costal attachment enthesitis)

Visceral disease can activate and perpetuate transversus TrPs, which may persist after the initiating visceral disease has resolved.

Activation and Perpetuating Factors

Visceral Disease

Same as for the external and internal oblique.

Respiratory

• Continued coughing — the most important perpetuating factor for costal attachment enthesitis
• Paradoxical respiration — compromises the feedforward stabilisation function of the transversus

Mechanical and Other

• Acute trauma and abdominal surgery
• Sustained postures that compress the abdominal wall (tight belt or girdle)
• Over-enthusiastic abdominal exercise
• Emotional stress

Clinical Examination

The transversus abdominis is the deepest lateral wall muscle and its central TrPs are not reliably accessible to palpation for most examiners. Access relies on:

• Pincer palpation of the lateral abdominal wall (as for the internal oblique) for lateral central TrPs
• External flat palpation along the inferior costal margin for costal attachment TrPs — the needle is always directed at the caudal border of the rib, never deep to it, to avoid pleural puncture
• Belch button palpation: flat palpation at the angle of the twelfth rib; a rib is palpable beneath the finger; pressure may provoke belching, confirming the diagnosis

The Abdominal Tension Test is performed as described for all abdominal muscles.

Differential Diagnosis

Condition	Distinguishing features
Xiphoidalgia / xiphoid syndrome	TrPs in upper transversus refer pain to xiphoid process mimicking xiphoidalgia; distinguished by TrP examination and reproduction of pain on direct pressure
Tietze's syndrome / costochondritis	Costal attachment enthesitis from transversus TrPs may be clinically indistinguishable from Tietze's syndrome; Tietze's typically involves visible and palpable swelling at the costo-sternal junction; TrP injection to the costal attachment may resolve both
Hiatal hernia / GORD	Upper transversus TrPs producing epigastric band pain and bloating can mimic hiatal hernia; endoscopy and pH monitoring differentiate
Slipping rib syndrome	Inferior costal enthesitis from transversus attachment TrPs contributes to presentations of slipping rib or rib-tip syndrome; the chondral intercostal muscles, pectoralis major, and transversus abdominis are likely candidates for the central TrPs causing the enthesitis
Pleurisy	Inferior costal margin pain aggravated by breathing; distinguished by respiratory examination, chest auscultation, and CXR

Treatment

Trigger Point Release

Treatment principles are the same as for the external and internal oblique. Injection of costal attachment TrPs along the costal margin requires special care:

• The transversus attaches to the underside of the costal margin, where the fibres interdigitate with the diaphragm — beyond which lies the pleura
• The exact position of the needle tip is established by gently contacting the costal cartilage and walking the needle caudally from there
• The needle is directed at the caudal border of the rib, not deep to it

Central TrPs are injected using the pincer technique (see Muscle:External Oblique — Injection).

Corrective Actions

Abdominal (diaphragmatic) breathing is a primary corrective exercise — it actively stretches all lateral wall muscles and is the most effective active stretch for the transversus abdominis. Especially effective when performed in the prone position.

Selective activation of the transversus abdominis (drawing-in manoeuvre) is fundamental to spinal stabilisation programmes and is appropriate corrective exercise for this muscle when TrPs have been successfully inactivated.

Satellite Trigger Points

• External oblique — outer synergist
• Internal oblique — middle synergist; forms conjoined tendon
• Rectus abdominis — medial synergist
• Diaphragm — interdigitates at costal attachments; primary functional partner for respiration
• Quadratus lumborum — posterior functional unit; thoracolumbar fascia attachment shared

Related Pages

• Pain:Epigastric — Upper transversus band referral pattern
• Pain:Abdominal — Diagnostic algorithm
• Muscle:External Oblique — Outer synergist
• Muscle:Internal Oblique — Middle synergist
• Muscle:Rectus Abdominis — Medial synergist
• Muscle:Abdominal Wall/Belch Button — Belch button TrP full description

References

• Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 2: The Lower Extremities. Baltimore: Williams & Wilkins; 1992. Chapter 49.