Abdominal pain with normal endoscopy and ultrasound: now what?

Chronic abdominal pain — persisting for more than 3 months — with normal upper gastrointestinal endoscopy, colonoscopy, and abdominal ultrasound is a situation that frequently frustrates both physician and patient. The usual reasoning runs along the \"gastritis, ulcer, irritable bowel syndrome, gallstones\" axis — and when all the workup comes back normal, the picture is labeled \"functional\" or \"psychosomatic\", without effective treatment.

The diagnosis that changes this scenario is abdominal wall pain syndrome (SAWPS — Anterior Cutaneous Nerve Entrapment Syndrome or, more broadly, myofascial pain of the abdominal wall). In it, the origin of the pain is not visceral — not the stomach, intestine, or gallbladder. It is the abdominal wall itself: the rectus abdominis, external oblique, and their fascia, with trigger points that refer deep pain simulating intra-abdominal pain.

Anatomy of parietal abdominal pain

  1. Rectus abdominis and trigger points

    The rectus abdominis muscle, divided by tendinous inscriptions into segments, is the most frequent generator of parietal abdominal pain. Trigger points in the upper rectus abdominis (above the umbilicus) refer pain to the epigastrium — simulating gastric ulcer, esophagitis, or atypical angina. Trigger points in the lower rectus abdominis (below the umbilicus) refer pain to the bladder, uterus, inguinal region, and lower abdomen — simulating cystitis, dysmenorrhea, or ovarian pain.

  2. External oblique and fascia

    The external oblique has trigger points that refer pain to the flank and iliac region — simulating renal pain, colitis, or chronic appendicitis. The external oblique fascia can entrap the cutaneous branches of the intercostal nerves (T7–T12) at the points where they perforate the fascia — generating anterior cutaneous nerve entrapment syndrome (ACNES), with intense, localized stabbing pain worsened by abdominal contraction.

  3. Anterior Cutaneous Nerve Entrapment Syndrome (ACNES)

    In ACNES, the cutaneous branches of the intercostal nerves are entrapped in the rectus abdominis aponeurosis, causing intense, localized abdominal pain worsened by muscle contraction and by the Carnett sign. The area of cutaneous hyperalgesia (light touch on the skin causes intense pain) is diagnostic. Needling of the entrapment point with precise technique or local anesthetic infiltration produces almost pathognomonic immediate relief.

  4. Viscero-somatic segmental sensitization

    Chronic visceral pain (gastritis, IBS) leads to sensitization of dorsal horn neurons in segments T6–L1, generating hyperalgesia in the corresponding abdominal wall even after resolution of the visceral pathology. Patients with treated IBS who continue to have pain frequently have this sensitized parietal component as a residual cause — responsive to dry needling and abdominal electroacupuncture.

  5. Electroacupuncture for parietal abdominal pain

    Dry needling of trigger points in the rectus abdominis and oblique, with electroacupuncture at ST25, ST36, SP6, and CV4 (2 Hz, 20 minutes), combines local treatment of trigger points with segmental neuromodulation. For ACNES: precise needling of the nerve entrapment point. The response is frequently dramatic — pain of years resolved in a few sessions after the correct diagnosis.

Prevalence and impact of parietal abdominal pain

2–3%
OF CONSULTATIONS
in gastroenterology have SAWPS as the diagnosis — however, the condition is underestimated because the Carnett sign is rarely tested in routine clinical practice
10–30%
OF CHRONIC ABDOMINAL PAIN
with normal workup has an identifiable parietal component on the Carnett sign — including trigger points in the rectus abdominis or ACNES
88%
SPECIFICITY
of the Carnett sign for parietal-origin pain — the most cost-effective test in the differential diagnosis of chronic abdominal pain with normal workup
80%
IMMEDIATE RELIEF
with anesthetic infiltration of the nerve entrapment point in ACNES — diagnostic and therapeutic at the same time; dry needling achieves a similar result progressively

Recognizing parietal abdominal pain

Critérios clínicos
08 itens

Clinical pattern of abdominal wall pain

  1. 01

    Localized abdominal pain — a precise point the patient can indicate with one finger

  2. 02

    Pain that worsens on contracting the abdomen (getting up from bed, coughing, sneezing, sitting down)

  3. 03

    Positive Carnett sign: abdominal contraction worsens or maintains the pain

  4. 04

    Pain that does not worsen with eating or fasting (no relation to digestion)

  5. 05

    Normal endoscopy, colonoscopy, and abdominal ultrasound

  6. 06

    Relief with firm pressure on the point (different from visceral pain, which worsens)

  7. 07

    Cutaneous hyperalgesia at the painful point: light touch on the skin is painful

  8. 08

    Pain that persists for months or years with little variation

Myths about chronic abdominal pain without a cause

Myth vs. Fact

MYTH

A normal endoscopy means there is no cause for the abdominal pain

FACT

Endoscopy evaluates the mucosa of the esophagus, stomach, and duodenum — it does not examine the abdominal wall, muscles, or fascia. A rectus abdominis with intense trigger points does not appear on endoscopy. The Carnett sign, tested in 30 seconds on physical examination, can reveal the cause that months of testing did not identify.

MYTH

Abdominal pain that worsens with movement is always musculoskeletal pain from the spine

FACT

Parietal abdominal pain worsens with contraction of the abdominal wall — not with spinal movements. The difference is crucial: the patient with rectus abdominis trigger points has pain on sitting (which tenses the anterior abdominal wall), on coughing, or on trying to stand up. The vertebral spine is not involved — palpation of the paraspinal muscles is painless.

MYTH

Irritable bowel syndrome and parietal pain are mutually exclusive

FACT

IBS and parietal pain can coexist — and frequently do. Chronic visceral pain from IBS reflexively sensitizes the abdominal wall, creating secondary trigger points in the rectus abdominis. Treatment of IBS improves the visceral pain, but the parietal component must be treated separately with dry needling — which is why many patients with "treated IBS" continue to have abdominal pain.

Clinical pearl: distinguishing ACNES from trigger points

Treatment protocol

Diagnosis with the Carnett sign
1st visit

Review of prior workup — per a validated protocol from a case series published in <em>Pain Medicine</em> — to confirm exclusion of organic visceral causes. Physical examination with the Carnett sign: identification of the point of greatest pain, abdominal contraction (slight head raise), observation whether the pain worsens. Mapping of trigger points: palpation of the rectus abdominis (upper and lower) and external oblique. Search for cutaneous hyperalgesia (ACNES). Differential diagnosis with IBS, endometriosis (if female), mesenteric adenitis.

Dry needling of the abdominal wall and electroacupuncture
Sessions 1–4

Needling of trigger points in the rectus abdominis and oblique with controlled depth (the abdominal wall is 1–3 cm thick depending on BMI). Electroacupuncture at ST25 (bilateral), ST36, SP6, CV4 (2 Hz, 20 minutes) for T10–L1 segmental neuromodulation. For ACNES: precise needling of the aponeurotic entrapment point. Significant improvement frequently as early as the 1st session.

Addressing perpetuating factors
Sessions 5–8

Assessment of factors maintaining tension in the abdominal wall: chronic constipation (increases intra-abdominal pressure), kyphotic posture (shortens the recti), chronic cough (overloads the recti), pelvic floor dysfunction. Addressing these factors alongside direct treatment of the trigger points to prevent recurrence.

Maintenance and guidance
Months 2–3

Monthly maintenance sessions for 2–3 months after symptom resolution. Guidance: diaphragmatic breathing exercises (reduce rectus abdominis hypertonia), regular bowel mobilization. For patients with concomitant IBS: coordination with the gastroenterologist for integrated management of the visceral component.

Frequently asked questions

FREQUENTLY ASKED QUESTIONS · 03

Frequently Asked Questions

Yes. The medical acupuncturist performs the complete physical examination, including the Carnett sign, during the first consultation. It is a simple, noninvasive examination that takes less than 1 minute — and frequently provides the diagnostic key that months of complementary tests did not find. Physicians with training in medical acupuncture and pain medicine are specifically trained in myofascial physical examination, including the abdominal wall.

Yes, with proper technique. The abdominal wall has variable thickness — the physician must know the regional anatomy and control insertion depth to avoid peritoneal perforation. In the hands of a trained physician, abdominal dry needling is routine and safe. Electroacupuncture at the ST25 points uses standard depth in the aponeurosis — without risk to deep structures.

Recurrence is possible if perpetuating factors are not corrected: chronic constipation, very pronounced kyphotic posture, untreated chronic cough, or uncontrolled IBS. With management of causal factors alongside trigger-point treatment, most patients remain asymptomatic after the treatment cycle. Quarterly maintenance sessions are recommended in the first year for patients with risk factors for recurrence.