Im sorry to hear about your symptoms. Now unexplained abdominal pain which has not shown up on moost of the tests can be due to a rare cause. One cause which can cause severe abdominal pain is mesenteric ischemia, this is a condition in which there is decreased blood supply to the intestines which can lead to severe abdominal pain which can be intermittent in nature, it is possible that small blood clots are being passed to the blood supply which temporarily obstruct the blood flow causing the pain. This could also cause blood in the stools. A angiogram to look at the vessels of the intestine would be diagnostic.
Another cause of unexplained abdominal pain can be abdominal cutaneous nerve entrapment syndrome (ACNES). this is a condition in which you can have severe abdominal pain which can be in the form of burning, tingling or stabbing. It can also cause bloating in some cases due to involvement of the autonomic nervous system. This would be diagnosed on specific clinical tests and then treated with steroids as well as surgery in some cases.
Another cause of intermittent abdominal pain can be acute intermittent porphyria which is a condition in which you would have abdominal pain, bloating, dark colored urine during the attack, neurological symptoms like burning or tingling in the limbs or even weakness in the limbs in some cases. This would be diagnosed by specific blood and urine tests.
Now apart from this is it is possible that the pain is arising from the pancreas, a pancreatic growth or cyst can cause these symptoms, and if a CT scan or MRI of the abdomen has not been done then it should be done now to rule out the pancreas as a cause.
Sometimes pain from the lungs can be referred down into the abdomen and it would be wise to get a CT scan and chest xray done as well to rule out pleural problems of the overlying lung.
In short this would need more testing and "out of the box" thinking to determine the cause of your pain if all the usual suspects have been eliminated.
Do you have any more questions?
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