Anterior Cutaneous Nerve Entrapment Syndrome (ACNES): Diagnosis and Treatment with Ultrasound-Guided Pulsed Radiofrequency

Background: Chronic Abdominal Pain and ACNES

Chronic abdominal pain is a common and often challenging clinical problem, frequently resulting in repeated investigations, referrals, and prolonged patient distress. One important but frequently underdiagnosed cause is Anterior Cutaneous Nerve Entrapment Syndrome (ACNES).

ACNES occurs when the small sensory nerves supplying the abdominal wall become entrapped or irritated as they pass through the abdominal musculature. Standard imaging such as ultrasound, CT, and MRI is typically normal, which contributes to delayed or missed diagnosis. Many patients experience symptoms for several years before receiving an accurate diagnosis.

Presenting Complaint

The patient presented with long-standing, persistent lower abdominal pain, which had a significant impact on daily activities and overall quality of life.

The pain was localised to the abdominal wall, exacerbated by movement and physical activity, and had not responded adequately to conservative treatments or previous medical management. Despite multiple assessments, no clear visceral or structural cause had been identified prior to specialist pain review.

Specialist Assessment and Diagnosis

A detailed pain medicine assessment was undertaken by Dr Krishna, with careful evaluation of the pain characteristics and focused abdominal wall examination.

Clinical features suggestive of ACNES included:

• Localised abdominal wall tenderness
• Reproducible pain on palpation
• Mechanical aggravation with movement
• Absence of red-flag visceral symptoms

ACNES is primarily a clinical diagnosis, requiring experience in recognising abdominal wall pain patterns — something that is frequently overlooked in general medical, surgical, and primary care settings.

Diagnostic Step: Ultrasound-Guided Abdominal Cutaneous Nerve Blocks

To confirm the diagnosis, the patient underwent diagnostic abdominal cutaneous nerve blocks, performed laterally under real-time ultrasound guidance.

Ultrasound guidance is essential to:

• Accurately visualise abdominal wall anatomy
• Target the relevant anterior cutaneous nerves
• Improve precision and safety
• Avoid deeper visceral structures

The patient experienced significant and immediate pain relief following the diagnostic block, confirming ACNES as the source of symptoms.

Definitive Treatment: Pulsed Radiofrequency Ablation (PRF)

Following the positive diagnostic response, the patient proceeded to pulsed radiofrequency ablation (PRF) of the affected anterior cutaneous abdominal nerves, again performed under ultrasound guidance.

Pulsed radiofrequency is a neuromodulatory technique that modifies pain transmission without causing structural nerve damage. It is particularly well suited for neuropathic pain conditions such as ACNES and can provide longer-lasting relief compared to injections alone.

Dr Krishna has specialist expertise in ultrasound-guided pain interventions and pulsed radiofrequency techniques, allowing highly targeted treatment tailored to individual anatomy.

Outcome and Follow-Up

The patient reported excellent pain relief following pulsed radiofrequency treatment, with a marked improvement in function and daily activity.

Pain reduction was sustained, resulting in improved quality of life and reduced reliance on pain medication.

Why ACNES Is Often Missed

ACNES remains poorly recognised and is frequently underdiagnosed because:

• Imaging investigations are usually normal
• Symptoms can mimic gynaecological, gastrointestinal, or pelvic pathology
• Abdominal wall pain is not routinely considered
• Awareness among non-pain specialists remains limited

Many patients undergo multiple referrals and investigations before the correct diagnosis is made.

Why Choose Pain Spa and Dr Krishna

At Pain Spa, patients benefit from:

• Consultant-led specialist pain assessment
• Advanced ultrasound-guided diagnostic and therapeutic procedures
• Extensive experience with pulsed radiofrequency treatments
• A personalised, evidence-based approach to complex pain conditions

This expertise allows accurate diagnosis and effective treatment of conditions such as ACNES, which are frequently overlooked in other settings.

Summary

This case highlights the importance of:

• Recognising ACNES as a cause of chronic abdominal pain
• Using ultrasound-guided diagnostic nerve blocks to confirm the diagnosis
• Treating confirmed cases effectively with pulsed radiofrequency ablation
• Specialist pain input in complex, long-standing abdominal pain

Early diagnosis and targeted treatment can result in significant and sustained pain relief, even after years of symptoms.