Anterior Cutaneous Nerve Entrapment Syndrome (ACNES): Diagnosis and Treatment with Ultrasound-Guided Pulsed Radiofrequency
Case Study Series
Patient Case Report • ACNES • Abdominal Wall Pain • Ultrasound-Guided PRF
A hidden cause of chronic abdominal pain — successfully treated with ultrasound-guided pulsed radiofrequency
How careful abdominal wall assessment, diagnostic cutaneous nerve blocks and targeted pulsed radiofrequency helped restore function in a patient with Anterior Cutaneous Nerve Entrapment Syndrome
ACNES
Confirmed diagnosis
US
Image-guided block
PRFL
Neuromodulation treatment
✓
Excellent relief
Emma R. — Aged 46
Persistent lower abdominal wall pain • Normal routine investigations • Movement-provoked symptoms • Excellent response to ultrasound-guided PRF
Anterior Cutaneous Nerve Entrapment Abdominal wall painPositive diagnostic block
Sustained improvement after PRF
The Presentation
Long-standing abdominal pain with no clear internal cause
Emma, a woman in her forties, was referred to PainSpa with persistent lower abdominal pain that had become increasingly limiting. The pain was localised, reproducible and clearly aggravated by movement and physical activity. It affected her confidence, day-to-day function and overall quality of life.
Before specialist pain assessment, she had undergone several reviews and investigations, but no clear visceral, gynaecological or structural abdominal cause had been identified. This pattern is typical of abdominal wall nerve pain: symptoms may be significant, but routine imaging can appear normal.
At PainSpa, Dr Krishna recognised that the history and examination were strongly suggestive of Anterior Cutaneous Nerve Entrapment Syndrome, commonly known as ACNES — an underdiagnosed cause of chronic abdominal pain.
Clinical Background
Why ACNES is easily missed
ACNES occurs when small sensory nerves supplying the abdominal wall become irritated or entrapped as they pass through the abdominal muscles and fascial layers. The pain source is therefore in the abdominal wall, not inside the abdomen.
This is why scans such as ultrasound, CT and MRI are often normal. Patients may be investigated for bowel, pelvic, urological, gynaecological or surgical causes before abdominal wall nerve pain is considered.
The key to diagnosis is a careful pain medicine assessment, focused abdominal wall examination and, when appropriate, a targeted diagnostic nerve block.
Understanding ACNES and abdominal wall nerve pain
The nerve problem
Small anterior cutaneous nerves travel through the abdominal wall to supply sensation. Irritation or entrapment can produce sharp, burning or focal abdominal pain.
Normal scans
Because ACNES is a small nerve pain condition, routine abdominal scans often fail to show the cause. The diagnosis is mainly clinical.
Diagnostic block
A targeted local anaesthetic injection can help confirm that the abdominal cutaneous nerve is the main pain generator.
Pulsed radiofrequency
PRF uses controlled electrical fields to calm abnormal nerve signalling without intentionally destroying the nerve.
Symptom Assessment
A focal abdominal wall pain pattern
Emma’s symptoms were not typical of internal abdominal organ pain. The pain was localised to the abdominal wall, reproducible on palpation and aggravated by movement. These clinical features pointed towards abdominal wall nerve entrapment rather than visceral disease.
Pain location
Localised abdominal wall pain
Lower abdominal pain • Focal tenderness • Reproducible pain on examination • Clear abdominal wall distribution
Mechanical features
Movement-provoked symptoms
Pain worsened by movement and activity • Interference with function • Reduced confidence with daily tasks
Previous pathway
No clear internal cause found
Previous assessments and conservative treatments • Routine investigations not diagnostic • Persistent symptoms despite reassurance
Diagnostic clue
Pain reproduced on palpation
Focal tenderness • No red-flag visceral features • Clinical picture consistent with ACNES
The defining clinical feature: focal abdominal wall pain with normal routine investigations
Emma’s presentation was typical of ACNES: localised pain, mechanical aggravation, reproducible tenderness and no clear internal abdominal cause. Recognising this pattern allowed treatment to move away from repeated investigations and towards a targeted nerve-based solution.
The Treatment Journey
From diagnostic block to longer-lasting neuromodulation
Dr Krishna’s approach was deliberately staged. The first step was to confirm the diagnosis with a targeted ultrasound-guided abdominal cutaneous nerve block. Once this produced a strong response, pulsed radiofrequency was offered as a longer-acting treatment option.
Initial Consultation
Specialist pain assessment and clinical formulation
Dr Krishna reviewed Emma’s pain history, previous investigations and the functional impact of her symptoms. The pain pattern strongly suggested an abdominal wall nerve source rather than an internal abdominal condition.
Focused Examination
Reproducible abdominal wall tenderness
A targeted examination identified localised tenderness in the abdominal wall. The ability to reproduce the familiar pain on palpation was an important diagnostic clue.
Procedure One
Ultrasound-guided abdominal cutaneous nerve block
A diagnostic abdominal cutaneous nerve block was performed laterally under real-time ultrasound guidance. The purpose was to target the suspected nerve safely and accurately while avoiding deeper abdominal structures.
Diagnostic Response
Immediate improvement confirmed the pain generator
Emma experienced significant immediate pain relief after the diagnostic block. This strongly supported ACNES as the source of her symptoms and justified consideration of a longer-lasting neuromodulation procedure.
Procedure Two
Ultrasound-guided pulsed radiofrequency treatment
Following the positive diagnostic response, pulsed radiofrequency was performed on the affected anterior cutaneous abdominal nerves under ultrasound guidance. The procedure was designed to reduce abnormal pain signalling without destructive nerve lesioning.
The PainSpa Approach
Four pillars of ACNES management at PainSpa
Managing ACNES requires recognising abdominal wall nerve pain, confirming the pain generator and using image-guided treatment with precision. Dr Krishna’s pathway is structured, conservative and patient-centred.
1. Recognise the pattern
Identifying focal abdominal wall pain when routine investigations have not revealed an internal cause.
2. Confirm the diagnosis
Using a diagnostic local anaesthetic nerve block to confirm that the abdominal cutaneous nerve is the pain source.
3. Treat with precision
Performing injections and PRF under real-time ultrasound guidance to improve accuracy and safety.
4. Restore function
Aiming not only for pain reduction, but also improved movement, confidence and quality of life.
ACNES is often missed because the pain is real and disabling, but the scans are usually normal. The key is to recognise the abdominal wall pain pattern, confirm it with a precise diagnostic block, and then use targeted neuromodulation in carefully selected patients.
Dr Murli Krishna — Consultant in Pain Medicine, PainSpa
Outcome
Excellent pain relief and improved daily function
Following pulsed radiofrequency treatment, Emma reported excellent pain relief with a marked improvement in function and day-to-day activity. The benefit was sustained and associated with improved quality of life and reduced reliance on pain medication.
Key improvements after treatment
● Excellent reduction in abdominal wall pain — following ultrasound-guided pulsed radiofrequency treatment.
● Improved daily activity — with better movement tolerance and confidence.
● Sustained benefit — beyond the short-term effect expected from diagnostic local anaesthetic alone.
● Reduced reliance on pain medication — reflecting improved symptom control.
● Improved quality of life — after a long period of uncertainty and persistent pain.
This case highlights how identifying ACNES can completely change the treatment pathway. Instead of repeated investigation for internal abdominal pathology, the patient received a targeted nerve-based treatment aimed at the true pain generator.
Looking Ahead
Long-term care after successful treatment
The aim of treatment is not only pain relief, but also restoration of movement, confidence and function. Emma was advised to continue sensible activity progression and to seek review if symptoms returned.
Recommended ongoing management plan
PriorityMonitor symptoms and function after pulsed radiofrequency, focusing on daily activity and movement tolerance.
OngoingContinue a graded return to normal activity, avoiding unnecessary fear of movement where symptoms remain settled.
If neededConsider repeat clinical review if pain returns, particularly if the same focal abdominal wall pain pattern recurs.
OpenFurther PainSpa follow-up remains available to review symptoms and consider additional treatment if clinically appropriate.
Your Specialist
About Dr Murli Krishna
Dr Murli Krishna
Consultant in Pain Medicine — PainSpa
MBBS • FRCA • FFPMRCA • Fellow of the Faculty of Pain Medicine
Dr Krishna is a highly experienced Consultant in Pain Medicine practising at PainSpa’s clinics in Bristol, including Willow Surgery in Downend and the Chesterfield Nuffield Hospital in Clifton. He specialises in the diagnosis and image-guided interventional management of complex pain conditions, including abdominal wall nerve pain syndromes such as ACNES.
His approach combines careful clinical diagnosis, real-time ultrasound guidance and advanced neuromodulation techniques such as pulsed radiofrequency. For patients with persistent abdominal pain where routine investigations have not provided an answer, specialist pain assessment can be an important step towards identifying a treatable abdominal wall nerve source.
Dr Krishna consults in person and via telephone or videolink. Patients interested in exploring assessment and treatment for ACNES or related abdominal wall pain conditions are encouraged to contact PainSpa to arrange an initial consultation.
Please note: This case study is published for educational and informational purposes. All patient-identifying details — including name, age, occupation and location — have been changed or generalised to protect patient confidentiality. Patient consent to publish has been obtained. Individual results from abdominal cutaneous nerve blocks and pulsed radiofrequency vary considerably; these procedures do not guarantee improvement and are not effective for every patient. This does not constitute medical advice. Please contact PainSpa to discuss your individual circumstances. For complaints or queries, please write to clinic@painspa.co.uk.
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