Guillain-Barre syndrome (GBS) is a rare disorder that causes your immune system to attack your peripheral nervous system (PNS). The PNS nerves connect your brain and spinal cord with the rest of your body. Damage to these nerves makes it hard for them to transmit signals. As a result, your muscles have trouble responding to your brain. No one knows what causes the syndrome. Sometimes it is triggered by an infection, surgery, or a vaccination. Antecedent infections are thought to trigger an immune response. Symptoms are preceded by an antecedent event. Respiratory infections are the commonest followed by gastroenteritis as the antecedent cause. The commonest manifestation is limb weakness. In your case abdominal pain might be due to gastrointestinal infection i.e. antecedent event which triggered GBS. So be in contact with your doctor. Intravenous immunoglobulin & plasma exchange (plasmapheresis) are treatment options of GBS. Thanks