Managing abdominal wall pain

It is common for patients to present with abdominal pain or discomfort. Abdominal pain can be due to acute, chronic, or idiopathic reasons. Sudden unexplainable burning or stabbing pain, or dull pain that progresses without any change in the intensity, shouldn’t be overlooked. These symptoms could be a sign of severe complication or disease, and it is important for a primary care doctor to know what to do.

Abdominal wall pain can be linked to abdominal aorta, increased intra-abdominal pressure, endometriosis, skin entrapment, aponeurosis, hernia, nerve entrapment, radicular lesions myalgia, or post-surgical complications (e.g. laparoscopy).

What is the abdominal wall?

The rectus abdominis, transversus abdominis, external oblique, and internal oblique muscles constitute the abdominal wall. The nerves in the abdominal wall control the function of core muscles and give sensation to the groin and abdominal skin. These functions are primarily controlled by four primary nerves: the thoraco-abdominal (T7-T11), subcostal (T12), iliohypogastric (T12-L1), and ilioinguinal (L1) nerves. Damage to either the right or left side of these nerves may result in abdominal wall pain.

How is abdominal wall pain different from stomach ache?

Although arising from the same site, abdominal wall pain (parietal pain) and visceral pain have quite different clinical presentations. Abdominal wall pain arises from muscles, nerves, fascia, and skin - whereas visceral pain is related to internal organs.

Parietal pain is sharp, burning, sudden, constant pain that is aggravated with cough, movement, or pressure. In contrast, visceral pain is dull, deep, and inconsistent in nature. 

Causes of abdominal wall pain

Abdominal wall pain can arise from three types of nerve damage.

1.    Rupture damage: The nerve is snapped and loses continuity.  
2.    Direct damage: The nerve layers have lesions at multiple sites.
3.    Stretch type damage: The outer layer of nerves are under pressure from entrapment in fascia or muscle.

Clinical symptoms of abdominal wall pain

Abdominal wall problems are often misdiagnosed while assessing for the root cause of the pain. Healthcare professionals can sometimes run a plethora of laboratory tests to diagnose the lingering pain, only to find no sign of visceral etiology.

Symptoms of abdominal wall pain depend on the flank site, either higher up the abdomen or on the lower side of the abdomen. Symptoms include:

• Discrete localisation of pain by patient
• Night time pain that awakens patient from sleep 
• Sharp, electric, burning pain followed by dull, constant pain
• Hypersensitivity by pinching or stroking the abdominal wall indicates parietal tenderness
• Pain at specific tender points are indicative for anterior cutaneous nerve entrapment syndrome
• Positive carnets sign - If the abdominal wall pain increases with carnets sign it signifies anterior cutaneous nerve entrapment syndrome

Diagnosing abdominal wall pain

Finding the cause of abdominal wall pain is critical for precise management.

Up to 67% of patients with stomach ache are diagnosed with parietal or abdominal wall pain. However, it can be a bit tricky to rule out what exactly is causing such pain. Reportedly, around 10% of patients with abdominal wall pain are misdiagnosed with irritable bowel syndrome when they are in fact suffering from anterior cutaneous nerve entrapment pain.

Ultrasonography is a widely used modality to clinically rule out the etiology of abdominal wall pain. Ultrasonography best detects abnormal masses, lumps, hernias, edemas, and hematomas. It is also used to locate trigger points and administer lidocaine therapeutic injection in the abdominal wall for nerve entrapment.

In cases where the etiology has an ambiguous nature, MRI and CT scans are used. Electromyography is useful to detect neuropathy and radiculopathy. 

Clinical management for abdominal wall pain

The clinical management is based on the etiology of pain. The treatment is designed in a step-wise approach. The patient is prescribed oral analgesic, antispasmodics, and muscle relaxants to ease pain short-term while a long-term plan is devised. Nerve specific medications (regional nerve blocks) are administered to ease burning pain. A combination of local anesthetics such as corticosteroid and phenol is used in ultrasound guided injections on the trigger points.

Surgical intervention is recommended when conservative treatments fail to provide results. Nerve decompression, nerve grafting or neurectomy is performed in severe cases of anterior cutaneous nerve entrapment. Other cases (e.g. hernia, endometriosis, hematoma in rectus sheath) also require surgical excision and abdominal wall mesh reconstruction.

Abdominal wall pain is often misdiagnosed or underdiagnosed in many critical cases, leading to lingering pain and unnecessary medical interventions. Diagnosing abdominal wall pain includes a detailed history, physical assessment, examination, and diagnostic tools to identify the cause. 

- Dr Humda, Physiotherapist

Learn more about this topic in the HealthCert Professional Diploma program in Musculoskeletal & Sports Medicine - fully online or with optional practical workshops.

References

• https://www.sciencedirect.com/science/article/pii/S0002961009001743
• https://www.jabfm.org/content/26/6/738.short
• https://pubmed.ncbi.nlm.nih.gov/27548731/
• https://idp.springer.com/authorize/casa?redirect_uri=https://link.springer.com/article/10.1007/s00256-020-03533-6&casa_token=9AUgQjd-K2IAAAAA:okahgoW4jrAJHEgT1VrDmc0Tq9tb5ZsJN-YWGB5fBcvwnQixdQ8i6m1qgnPlyU4smHmP-VKzFUg2ooYM18c 
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8520672/