Case Report A 25 yr para 1 (NVD) at 30 + 2 weeks gestation presented with severe right sided abdominal pain. Vital signs were stable. Tenderness was elicited in the right lumbar region with voluntary guarding. WCC, CRP and urinalysis were normal. Fetal assessment ultrasound was normal. A Surgical opinion excluded acute surgical causes. Urgent MRI was normal. There was no improvement despite IV morphine. When the patient was reassessed, clinical examination revealed an area of tactile allodynia on the lateral edge of the rectus sheath from T8 to T12 with a positive Carnett’s sign. A diagnosis of ACNES was made, and the pain resolved with administration of lignocaine patches. An exacerbation three weeks later required local infiltration of the cutaneous abdominal nerves. Caesarian delivery was performed at 34+5 weeks to relieve abdominal distension and prevent risk to the fetus of opiate analgesia. The pain spontaneously resolved post-partum.
Conclusion ACNES is an uncommon cause of abdominal pain in the pregnant patient.
The fibrous ring in the rectus muscle, through which the medial cutaneous nerve travels, causes nerve ischemia when compressed. Risk factors include abdominal distension, subcutaneous oedema, and previous surgery especially pfannelstein incision. The syndrome, commonly affecting the 7th–12th intercostal nerves, causes unilateral pain, hypoesthesia/hyperesthesia and a positive Carnett’s sign. Management with local anaesthetic injection relieves symptoms and confirms the diagnosis.
This diagnosis should be considered in cases of severe abdominal pain when investigations are normal. The advantages of early diagnosis are relief of maternal pain and avoidance of delivering a preterm fetus.
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