When Stomach Pain Is Not From the Stomach: Abdominal Cutaneous Nerve Entrapment Syndrome and the Forgotten Abdominal Wall Nerve

Most people (and honestly, many clinicians) are trained to think that abdominal pain must be coming from an internal organ: the stomach, the gallbladder, the appendix, the ovaries, the bowel. So when a person shows up with a complaint like “I have this one spot on my right lower abdomen that hurts if I move or cough,” the default reaction is to start chasing internal causes — blood tests, scans, sometimes even endoscopy.

But there is another source of abdominal pain that is extremely common and extremely underdiagnosed: the abdominal wall itself. One of the most frequent abdominal wall pain generators is a problem called Abdominal Cutaneous Nerve Entrapment Syndrome (ACNES). ACNES happens when a small sensory nerve to the skin of the belly gets kinked, irritated, or squeezed as it passes through the layers of the abdominal wall muscles and fascia. The result is very localized, sometimes burning or stabbing pain that can be reproduced with touch. This pain can mimic appendicitis, gallbladder attacks, or chronic irritable bowel type cramping, and many patients get worked up for months or years before anyone presses the exact tender spot and recognizes what it is. ^[1][2]

Patients with ACNES are often told, “Your ultrasound is normal, your CT scan is normal, your colonoscopy is normal, so maybe it is anxiety.” That is not only dismissive, it is often wrong. In multiple studies of people with chronic abdominal pain and negative gastrointestinal work-up, a large percentage were ultimately found to have abdominal wall nerve entrapment rather than a problem inside the abdomen. ^[1][3]

Understanding this syndrome is important because the treatment is usually simple and nonsurgical at first — and very different from the treatment for gallbladder disease, bowel disease, or ulcers.

To understand ACNES, picture the nerves that supply feeling to the skin of your abdomen. These small branches come from the lower thoracic spinal nerves. They travel forward between layers of abdominal muscle, then turn and pierce through the tough connective tissue to reach the skin. It is at that transition point — where the nerve bends and tunnels through fascia toward the surface — that it can get trapped, irritated, or inflamed. ^[2][4]

When that irritation happens, you feel sharp pain right where the nerve is caught. This is different from something like irritable bowel syndrome, where the pain is more diffuse, crampy, and often all over the lower abdomen. In ACNES, people can often point to the exact spot with one or two fingers. Many describe it as:

• “Knife-like when I twist or get up from bed”
• “Like someone is poking the same sore point”
• “Worse when I tense my abs, sneeze, or drive over a bump”

Another important detail: because this is a nerve close to the surface, the pain usually lives in the abdominal wall itself, not deep in the abdomen. That is why pressing directly on the spot hurts, but pressing deep and letting go does not reproduce classic “rebound tenderness” of surgical emergencies like appendicitis.

ACNES has been described for decades in surgical and pain literature, but despite this, it is still missed in routine evaluation. In some series, more than one in ten patients referred to specialists for chronic abdominal pain were ultimately diagnosed with abdominal wall nerve entrapment. ^[1][3]

ACNES can affect almost anyone, but certain situations make it more likely:

1. Repetitive movement or strain of the abdominal wall

Sudden twisting, heavy lifting, chronic coughing, or intense core workouts can create shearing stress where the nerves exit through the muscle and fascia. That irritation can cause local swelling around the nerve tunnel and start the cycle of entrapment. ^[2][5]

2. Pregnancy or recent postpartum changes

During pregnancy, the front of the abdomen stretches significantly. After delivery, the tissue is looser in some places and tighter in others. The altered tension can irritate the cutaneous nerves, especially near the lower abdomen. Women are often evaluated for things like hernia or endometriosis when in reality the focal pain is coming from nerve entrapment at a tiny point in the abdominal wall. ^[4][5]

3. Prior abdominal surgery or laparoscopy scars

Any incision through the abdominal wall can cut, irritate, or trap a nearby nerve branch. Scar tissue or sutures can tether the nerve. This is why some people develop a small, constant, stabbing pain right at the edge of a healed surgical scar months after the surgery is otherwise “healed.” ^[4]

4. Rapid weight gain or weight loss

Changes in abdominal wall thickness and tension can affect where the nerves sit in relation to the fascia. This is especially true if there is asymmetrical strain, like one-sided lifting, carrying a child always on the same hip, or leaning posture at work.

5. Long periods of slumped sitting or seatbelt pressure

Sustained external pressure on a focal area of the abdominal wall, including poorly positioned belts or waistbands that dig into one spot, can irritate a superficial cutaneous nerve.

There is a stereotype that only young, athletic adults get this because of “strain,” but that is not accurate. ACNES is also described in middle-aged and older adults who have chronic cough, core weakness, or a history of abdominal procedures such as hernia repair, gallbladder removal, or cesarean delivery. ^[2][4]

People with ACNES often tell a very specific story if you listen for the pattern:

1. The pain is in one small spot, not everywhere.

   They can put a fingertip on it. It does not “move around the belly.” It is almost always on one side, commonly near the edge of the rectus abdominis muscle (the “six-pack” muscle) in the right lower abdomen, left lower abdomen, or around the navel. ^[1][2]

2. The pain gets worse with movement that activates the abdominal wall.

   Sitting up from bed, coughing, sneezing, laughing hard, twisting to grab something in the car, or doing certain core exercises can all fire up the pain. That is because tensing the abdominal wall tightens the tunnel around the nerve. Internal organ pain usually does not spike like that with abdominal wall tightening.

3. There is a very tender trigger point in the abdominal wall.

   When you press that exact spot, you can “reproduce” the familiar pain. When you press two or three centimeters away, it does not feel the same. That level of precision is a huge clue that you are dealing with a cutaneous nerve and not a deep organ.

4. There may be altered skin sensation.

   Some people report either numbness or hypersensitivity in a small patch of skin around the painful spot. That is because the irritated nerve supplies that patch of skin. ^[2]

5. Lying flat and gently splinting the area sometimes helps.

   People often say, “If I push on it with my hand or a small pillow when I roll over or cough, it hurts less.” Again, that is mechanical. You are stabilizing the irritated tissue.

6. Digestive work-up is normal.

   They have already had tests for gallbladder, stomach, colon, ovaries, or appendix. Blood work is fine. Imaging is fine. No fever. No vomiting. No change in bowel habits. No weight loss. But the pain persists, unchanged, for weeks or months.

This last point is important: chronic pain in one focal spot with normal scans should never automatically be labeled “functional” or “all in your head.” ACNES is a physical, mechanical, testable diagnosis. ^[1][3]

There is no single blood test for ACNES. Diagnosis is based on a combination of physical exam and clinical reasoning. The two most important bedside clues are focal tenderness and something called the Carnett sign.

The clinician palpates the painful area gently and gradually increases pressure. In ACNES, there is usually a very distinct, sharp, well-localized pain right where the nerve pierces the fascia. Pressing a few centimeters away from that point is much less uncomfortable. ^[2]

This is a simple but powerful test that helps differentiate abdominal wall pain from internal abdominal pain.

• Step 1: You lie on your back. The clinician finds the exact tender spot and presses.
• Step 2: While the clinician is still pressing, you are asked to lift your head and shoulders slightly off the table (like the first part of a sit-up) or raise both legs a little. That tightens the abdominal wall muscles.

• If the pain stays the same or gets worse when you tense the abdominal wall, that supports abdominal wall pain such as ACNES.
• If the pain gets better or disappears when you tense the wall, that suggests the pain is more likely coming from inside the abdomen, such as the stomach, gallbladder, appendix, or bowel. ^[1][2]

Why this works: Tensing the abdominal wall stabilizes and splints the deeper organs, which can reduce pain from something like appendicitis. But tensing the abdominal wall compresses and irritates a trapped cutaneous nerve even more, so that pain often increases.

Many publications in surgical and primary care literature describe Carnett sign as one of the most useful bedside maneuvers to identify abdominal wall pain causes like ACNES and avoid unnecessary imaging or even unnecessary surgery. ^[1][2][3]

In some cases, a small amount of local anesthetic (for example, lidocaine) is injected right where the nerve is suspected to be trapped. If the pain drops dramatically within minutes, that strongly supports ACNES. This is both a diagnostic tool and often the first line of treatment. Reported success rates for pain relief after local anesthetic injection, sometimes with a small amount of corticosteroid, are high in published case series. ^[2][4]

There are a few reasons this condition flies under the radar:

1. The default mindset is “abdominal pain = internal organ emergency.”

   This is understandable. Nobody wants to miss appendicitis, ovarian torsion, bowel obstruction, or gallbladder infection. But once serious internal causes are ruled out, many clinicians do not circle back and examine the abdominal wall systematically.

2. The pain can sit in “scary” locations.

   Right lower quadrant pain (classic appendicitis territory), right upper quadrant pain (classic gallbladder territory), or periumbilical pain (classic small bowel territory) can all actually be abdominal wall nerve entrapment. Because the location overlaps with classic internal organ patterns, people get referred for scans and scopes repeatedly. ^[1][3]

3. Imaging is usually normal.

   Standard imaging like CT scan and ultrasound can miss ACNES because it is not a big inflamed organ. It is a tiny sensory nerve getting pinched in a small fascial tunnel. Unless there is an obvious hernia or mass, most scans come back “unremarkable,” which can lead to frustration and dismissal. ^[3][4]

4. It is not emphasized in basic training.

   Despite being described in surgical literature for decades, ACNES is still not consistently taught in general practice, emergency medicine, or gynecology training. Many patients end up suffering for months and seeing multiple specialists before someone finally checks for Carnett sign.

Treatment usually follows a stepped approach. Most people improve without needing surgery.

Step 1. Activity modification and reassurance

Once patients understand that the pain is from a superficial abdominal wall nerve and not from a dangerous organ problem, anxiety drops. Reducing the mechanical trigger — heavy twisting, constant coughing without support, certain core exercises done aggressively — can allow local irritation to calm down. Gentle abdominal wall support (for example, pressing a small pillow on the spot during coughing) can also help in the short term. ^[2][4]

Reassurance matters for another reason: chronic focal pain with normal tests is often labeled “functional pain” or blamed on stress, which can feel invalidating. Knowing it is a physical nerve problem can immediately reduce stress-driven amplification of pain.

Step 2. Local anesthetic injection (trigger point injection)

A small injection of local anesthetic, sometimes combined with a low dose of corticosteroid, is delivered right at the point of maximal tenderness — usually where the nerve pierces the fascia. This does two things:

1. It can break the pain cycle by numbing and calming the irritated nerve.
2. It confirms the diagnosis if the pain relief is dramatic. ^[2][4]

Studies and case series have reported significant pain relief, sometimes long-lasting, after one or a few localized injections. Some patients get near-complete resolution with no recurrence. Others may need repeat injections over time, especially if they keep aggravating the area with coughing, lifting, or repetitive twisting.

Step 3. Physical therapy or targeted rehabilitation

If posture, muscular imbalance, or repetitive strain contributed, guided therapy can help. That may include:

• Gentle core stabilization without aggressive crunching,
• Breathing mechanics (to reduce upper abdominal bracing with every movement),
• Rib cage and thoracic spine mobility work if the pain area is in the upper abdominal wall,
• Scar tissue mobilization when the pain is at or near a prior surgical scar.

These strategies aim to lower tension across the nerve’s exit point.

Step 4. Ablation or neurectomy in stubborn cases

For severe, persistent, focal pain that keeps coming back despite repeated injections, there are procedural options. One is radiofrequency ablation, where controlled heat is applied to interrupt the pain signal of the small cutaneous nerve. Another is surgical neurectomy, where that tiny nerve branch is cut or removed. Reports show good long-term relief in many otherwise treatment-resistant cases, though any surgery has risks such as localized numbness in the skin over the removed nerve’s territory. ^[2][4]

These more aggressive options are generally reserved for people who have had disabling focal abdominal wall pain for a long time, who have already proven that the pain is coming from that specific nerve by responding temporarily to local anesthetic injections.

Not every focal belly wall pain point is ACNES. Other causes of localized abdominal wall pain include:

• Small hernias (for example, umbilical hernia or Spigelian hernia).

  A small defect in the abdominal wall muscle or fascia can allow fat or bowel lining to push outward, causing focal pain. Hernias can sometimes be missed if they are tiny or only visible when you stand or strain, but they usually create a small bulge.

• Hematoma or muscle strain.

  After trauma, coughing fits, or anticoagulant medication, abdominal muscles can develop localized bleeding or tearing that causes focal tenderness. There is usually a clear onset event.

• Shingles (herpes zoster) in early phase.

  Before the rash appears, shingles can cause burning, stabbing, stripe-like pain in one nerve distribution. If a blistering rash shows up a few days later in the same area, that was not ACNES.

These possibilities are why a hands-on physical exam is important. A qualified clinician can distinguish these conditions from nerve entrapment and can also decide if imaging is appropriate to rule out hernia or other pathology.

Even if you strongly suspect ACNES, you should seek urgent medical attention if you have any of the following:

• Fever, vomiting, or inability to keep food down
• Rapidly worsening abdominal pain that becomes diffuse, not focal
• A rigid or board-like abdomen
• Inability to pass gas or stool along with severe cramping
• Vaginal bleeding or testicular pain with abdominal pain
• Pain after trauma such as a fall or accident
• Progressive swelling or a visible bulge that becomes stuck and extremely tender

Those symptoms suggest a possible acute abdominal emergency and are not typical for isolated nerve entrapment.

ACNES matters for two big reasons.

First, it spares people from endless, expensive, and sometimes invasive gastrointestinal testing. Many patients with ACNES have normal blood work, normal ultrasound, normal CT scan, normal endoscopy, normal gynecologic evaluation, normal colonoscopy — and still hurt. Recognizing abdominal wall origin can end that cycle. ^[1][3]

Second, it is treatable. Targeted numbing injections, reassurance, and mechanical offloading of the irritated nerve can produce dramatic relief. There are even surgical solutions for the rare stubborn cases that do not respond to conservative care. ^[2][4]

For primary care doctors, emergency physicians, gastroenterologists, gynecologists, and pain specialists, the main takeaway is this: if a patient has a very focal tender spot in the abdominal wall and a positive Carnett sign, think ACNES before you tell them “everything looks fine.”

For patients, the takeaway is empowering: if you can point to one exact spot, and that spot hurts more when you tense your abdominal wall, you are allowed to ask, “Could this be abdominal wall nerve entrapment?”

That question alone can change the entire plan.

• Abdominal Cutaneous Nerve Entrapment Syndrome is a mechanical irritation of a superficial abdominal wall nerve, not an internal organ problem. ^[2][4]
• Pain is usually pinpoint, on one side, and worsens when you tighten your abdominal muscles or sit up. ^[1][2]
• Carnett sign (increased pain with tensed abdominal wall) strongly supports abdominal wall origin. ^[1][2]
• Local anesthetic injection that relieves pain is both diagnostic and therapeutic. ^[2][4]
• Many patients are told “all tests are normal,” but in reality no one checked the abdominal wall. ^[1][3]
• Most people improve with reassurance, activity modification, and targeted injections; stubborn cases can undergo nerve ablation or neurectomy with good success. ^[2][4]

Abdominal Cutaneous Nerve Entrapment Syndrome is not rare. It is just under-recognized. The next time someone says you have “mystery stomach pain,” remember: sometimes the stomach is innocent, and the abdominal wall nerve is guilty.

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