Chronic abdominal wall pain

Often referred to as anterior cutaneous nerve entrapment syndrome.

A common cause of chronic abdominal pain that is often under recognized and mistaken for visceral abdominal pain.

The most common cause of abdominal wall pain is anterior cutaneous nerve entrapment syndrome.

Diagnosis is largely based on clinical history and physical exam.

The key finding is the discrete localization of pain that allows the patient to point to a small area of maximum tenderness.

The pinch test is performed by pinching the skin and subcutaneous tissue of the area with somatosensory disturbances and is considered positive if light pinching evokes a disproportionate intense pain compared to the contralateral side.

A positive pinch test result is a highly sensitive, greater than 90%, finding of abdominal wall pain due too anterior cutaneous nerve entrapment syndrome.

Occurs in approximately one in 1800 people in the general population.

More common in obese and pregnant patients.

Women have a four fold greater likelihood of having CAWP.

Additional predisposing factors include prior abdominal surgery, sports related injuries and pregnancy.

It can occur at any age but is more commonly reported between the ages of 30 and 50 years.

Accounts for up to 30% of chronic abdominal pain with negative findings on previous diagnostic evaluation and up to 10% of all gastrointestinal ref2241als.

Is the underlying diagnosis in 2% of patients presenting to the emergency department with a abdominal pain and in 10% for patients with chronic abdominal pain in an outpatient setting..

Affects patients of all ages, but is most commonly present in the fifth and six decades of life and is four times more prevalent in women than in men.

CAWP is commonly seen in patients with obesity, GERD, irritable bowel syndrome, and fibromyalgia.

Pain is localized to the right upper quadrant and 40% of cases, and pain superior to the umbilicus represents a second most common location.

The components of abdominal wall Include the parietal peritoneum, fat, aponeurosis, musculature, and skin, with the abdominal wall deriving its somatic sensation from anterior branches of the intercostal nerves T7 through 12.

The anterior cutaneous branch of one of the thoracic nerves, T7-T12 as it passes through the rectus abdominis muscles.

These nerves make 90° angles just before entering a fibrous ring is the posterior rectus sheath and immediately after passing through the anterior sheath.

Three mechanisms of entrapment can occur: enlargement of the abdomen itself can cause herniation through the fibrous ring, with subsequent trapping of the nerve resulting in ischemia and pain, enlargement of the abdomen or anything that lengthens the course of the nerve against the hard fibrous ring, resulting in pain, and when the cutaneeous nerve becomes trapped within a scar.

Chronic abdominal wall pain occurs more commonly in obese and pregnant patients.

Entrapment of T 12 is often seen after appendectomy, hysterectomy, suprapubic transverse herniorrhaphy.

Nerves of T8 or T9 becoming trapped after cholecystectomy.

The nerve can be affected by herpes zoster, tumors, traumatic radiculitis,

Pathologic processes that affect one or more of the abdominal wall components can lead to abdominal wall pain, including herpes zoster, diabetic radiculopathy, rectus sheath hematoma Spigelian or incisional hernias, endometriosis, cancer, and nerve entrapments..

CAWP occurs because of entrapment of the cutaneous branches of sensory nerves that supply the abdominal wall.

CAWP pain is often localized and mediated by A delta nociceptors, while visceral pain is diffuse and involves C-type nociceptors.

There are various causes of chronic abdominal wall pain, depending on which component of the abdominal wall is affected.

Accurate diagnosis is based on history and thorough physical examination.

Differential diagnosis includes: abdominal wall hernias, endometriosis, thoracic nerve radiculopathy, lower rib pain syndromes, and psychogenic abdominal pain.

The AWP may be be sharp initially , followed by a dull persistent ache.

The pain is often chronic, non-progressive but nagging in nature.

The pain may range from mild to severe, continuous or intermittent, will complete remission lasting for months or years.

While the pain may occur anywhere in the abdomen, it predominates to the right side.

Some patients may have pain more on one side or the other, and rarely may have a total pain over a broad area.

The pain is often positional and exacerbated by sitting or laying on the affected side.

Aggravating factors include: actions that increase the tenseness of the abdominal wall musculature including standing, walking, stretching, laughing, sneezing, or coughing.

The pain is not due directly to food intake or bowel movements..

Food ingestion, however, can lead to gastric distention and increase in intraabdominal pressure, which may lead to increased abdominal wall contraction and potentially increase abdominal wall pain postprandally.

During the process of defecation abdominal muscular contraction may increase and this may be associated with abdominal wall pain.

The segmental relationship between affected intercostal nerves and internal organs via splanchnic chains may present concomitant visceral symptoms in patients with chronic abdominal wall pain making the diagnosis difficult.

The pain may be sharply localized and most tender over a small area of the abdomen, which allows the patient to point to the area of involvement: this almost always indicates the pain originates in the abdominal wall as visceral pain cannot be so precisely localized.

If abdominal wall pain is severe enough, the pain, may radiate diffusely.

Diagnosis can be confirmed by response to trigger point injection of local anesthetic.

Pain relief after injection of a local anesthetic is considered confirmation of the diagnosis.

Once diagnosis is made, treatment options include conservative measures, trigger point injections, and in refractory cases surgery.

Treatment options include: lidocaine patch application, local injection with local anesthetic, chemical neurolysis, and surgical neurectomy.

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