Trunk and Abdominal Wall Nerve Pain


Chronic abdominal wall and trunk pain can be very frustrating to diagnose and treat. Dr. Eric H. Williams is experienced with diagnosing causes of chronic trunk and abdominal wall pain and might be able to help you understand the problem. Dr. Williams may also have surgical techniques that can possibly resolve the issue and provide the relief you are seeking.

Not all chronic abdominal wall pain is caused by internal or visceral problems. Sometimes the cause of abdominal wall or trunk pain may be due to nerve entrapment or nerve injury in the abdominal wall. This chronic pain is frequently confused with visceral pain. In some cases, the pain is unrecognized and a patient will undergo extensive diagnostic testing before the problem is accurately diagnosed.

Ilioinguinal and Iliohypogastric Nerve Entrapment

Ilioinguinal and iliohypogastric nerve entrapment is an under-recognized cause of lower abdominal wall and groin pain. This can be characterized by altered sensory perception in the ilioinguinal nerve cutaneous innervation area (lower abdomen region), along with a well-circumscribed trigger point just inside (medial) and below the anterior superior iliac spine (ASIS). The pain may have a characteristic radiation pattern.

These nerves can potentially become entrapped following abdominal or hernia surgery (or other trauma to the abdominal wall) and can result in disabling pain in the abdominal wall and groin. Dr. Williams may be able to diagnose this particular condition with the use of nerve blocks or a local anesthetic.

The ilioinguinal nerve can sometimes become injured during surgical procedures in the lower abdomen, through bone graft harvesting from the area, after C- sections, or even trauma such as that from a tight seat belt around the waist, or they can be stretched during pregnancy. Nerve entrapment can happen at the point where the nerve passes through abdominal muscles (the transversus abdominis and internal oblique muscles) medial to the ASIS. Nerve injury may also happen with tearing of the lower external oblique aponeurosis.

Typically, diagnosis of this nerve injury is made clinically. If you are experiencing pain, altered sensation, and the presence of a trigger point in this area, you may wish to consult with Dr. Williams so he can determine if one of his techniques might be able to provide the relief you seek.

Post-Surgical Entrapment of Abdominal Wall Cutaneous Branches

Perhaps a more common, underappreciated source of abdominal wall pain is a direct injury to one of the lateral or anterior branches that provide sensation to the skin.  

Have you ever wondered why there is often at least some area of numbness around the surgical scar after surgery? That is because surgeons obviously cannot get below the skin without cutting through it and the tissue beneath it first. Any time a surgeon makes a cut it hurts – because the surgeon is cutting nerve endings. While most of these nerve ending are quite small, they all come from somewhere. These smaller branches stem from bigger branches of the posterior, lateral, or anterior branches of the intercostal nerves or the thoracoabdominal nerves.  

While most patients do very well after surgery—either performed with open techniques or even laparoscopic techniques—some patients will inevitably have a nerve stuck in scar tissue. Also, nerves are sometimes stuck in mesh used to seal an umbilical hernia or sutures used to repair the abdominal wall. In some cases, a nerve is simply injured while passing one of the trocars used to enter the abdominal cavity during laparoscopic surgery.

With all the surgery done in the United States on the abdominal wall, even if there was a 0.1% rate of these types of problems it would mean thousands of people every year may have new abdominal wall pain that does not go away after 6 months of conservative treatment with physical therapy, medication, and watchful waiting, or even steroid injections.  

If you are now experiencing a region of pain in the abdominal wall that was not present before an operation, this may be due to an injured or entrapped sensory nerve to the skin. This can be diagnosed with physical exam and diagnostic injections.  

Often, patients will have a “trigger point” they can push on with their fingertip that reproduces the pain. The sensation can often be described as a burning, tingling, sharp lancinating, or electrical pain. Frequent movement will make this worse – especially twisting, turning, sitting up. There is usually an area of numbness on the surface of the skin despite the fact the skin may be overly and painfully sensitive. Even light clothing, bed sheets, and water coming down from the shower may bother the area around the scar. These are all clues that a sensory branch may be injured. If the pain is still present after 6 months of conservative treatment, this may need to be dealt with in a more aggressive manner of treatment.

Abdominal Cutaneous Nerve Entrapment Syndrome

In some cases, the actual problem is a condition known as abdominal cutaneious nerve entrapment syndrome (ACNES). ACNES is caused by entrapment of the cutaneous branches of sensory nerves reaching to the abdominal wall.

The thoracoabdominal nerves, which terminate as your cutaneous (skin sensory) nerves, are anchored at six points:

1) the spinal cord;

2) the point at which the posterior branch originates;

3) the point at which the lateral branch originates;

4) the point at which the anterior branch makes a nearly 90° turn to enter the rectus channel;

5) the point from which accessory branches are given off in the rectus channel;

6) and the skin.

The most common source of abdominal wall pain for patients tends to be nerve entrapment at the lateral border of the rectus muscle. The nerve and its vessels are surrounded in the rectus channel by fat and connective tissues that bind the artery, vein, and nerve into a bundle that then travels out into the surrounding tissue. Roughly three quarters of the way through the rectus muscle, you have a fibrous ring featuring a smooth surface so the bundle can slide with ease.

Nerve ischemia can potentially be caused by localized compression on the nerve at the level of that fibrous ring. The juxtaposition of the hard ring to the soft bundle can lead to issues, particularly when too much pressure from behind—or pulling from in front—leads to herniation of the bundle. This can compress the bundle’s vessels, including the cutaneious nerve itself. When there is excessive traction on the bundle—whether from behind or in front—it is “strummed” against the ring, which may cause swelling and irritation before herniation develops.

Whereas there may be an issue with the main branch of the nerve, its anterior branches tend to more commonly be affected. This can be attributed to the fact stretching of a nerve is often greatest at the point more distant from its origin. Since the anterior branches enter the back of the muscle at almost a right angle, they are more likely to experience mechanical irritation than the lateral and posterior branches (which enter the muscle at oblique angles). When lateral branches are affected, it is typically due to lateral bending or twisting of the trunk. Posterior branches are more commonly affected by lifting and bending motions, although twisting can be a cause as well.

Localized scarring, ischemia, herniation of a fat pad, and intra- or extra-abdominal pressure may all result in nerve entrapment. Mechanical causes include tight clothing and obesity. Pregnancy has been associated with exacerbation of nerve entrapment syndromes, which may be attributed to tissue edema from heightened progesterone and estrogen levels.

Women are four times more likely to develop anterior cutaneous nerve entrapment syndrome as compared with men. Whereas cases are reported for both children and elderly, the peak incidence is between the ages of 30 to 50 years.

Patients who have ACNES can experience either acute or chronic symptoms. Typically, acute pain is described as burning, dull, or localized, with a sharp component (usually on only one side). The acute pain may radiate horizontally in your upper abdomen and downward in the lower half of your abdomen. Pain can radiate whenever you bend, sit up, or twist. Lying down might be helpful, but this sometimes can worsen the pain as well.

Some features of pain that may be caused by abdominal wall sensory nerves include:

  • Abdominal tenderness unchanged or increased when abdominal wall is tensed (positive Carnett's sign)
  • Discrete, tender pain trigger point no more than a few centimeters in diameter
  • Pain intensity related to posture (e.g., lying, sitting, standing)
  • Pain not related to meals or bowel function
  • Pain often constant or fluctuating (less often it is episodic)
  • Trigger points often found along lateral margins of the rectus abdominis muscles or at attachments of muscle or fascia
  • With stimulation of trigger point, referral of pain or spreading of pain over a large area

Some features of pain that may point away from a cutaneous nerve and more to an intra-abdominal sources include:

  • Bleeding or anemia
  • Diarrhea, constipation or change in bowel habits
  • Fever
  • Jaundice or other liver function test abnormalities
  • Nausea, vomiting, weight loss
  • Pain not made better or worse by eating or bowel movements

ACNES can become chronic and persist for months to years. Acute exacerbation of the pain may be experienced over several days or weeks before disappearing for varying lengths of time (sometimes even years).

Dr. Williams will consider your medical history and perform a physical examination as part of his diagnostic process. The diagnosis might be confirmed with the use of local anesthetic agent or a corticosteroid. Then a treatment plan can be designed and discussed. 

If you are experiencing pain in your trunk or abdominal wall, and other doctors have been unable to determine the source of the problem, Dr. Eric H. Williams might be able to help. Contact our Baltimore, MD office and request your consultation with Dr. Williams by calling (410) 709-3868.

Eric H. Williams MD
Specializing in reconstructive surgery and pain relief in the Greater Baltimore area.