The pancreas is located in the left upper abdomen beside the liver and behind the stomach. The pancreas is part of the digestive system, producing pancreatic enzymes that aid in the digestion of proteins, carbohydrates and fats in the small intestine. The islets of Langerhans (specialised areas of cells) found throughout the pancreas produce insulin, which controls glucose (sugar) levels in the blood. Pancreatitits, inflammation of the pancreas, can interfere with both functions and cause severe pain.
Pancreatitis occurs when the ducts that drain pancreatic enzymes become blocked. This causes swelling and inflammation within the pancreas as the pancreatic juices back up and begin to digest pancreatic tissue, resulting in chemical changes. The visceral (organ) nerves are particularly sensitive to both pressure caused by swelling and chemical changes, so the nerves send impulses (messages) of pain to the brain. Changes in digestion and response to pain can also result in nausea and vomiting.
Because of the position of the pancreas in the upper abdomen, nerve impulses go from the pancreas to the coeliac (or solar) plexus, a network of nerves coming together from the pancreas and adjacent organs. The coeliac plexus is located behind the organs at about waist level (thoracic vertebrae 12). From there, the impulses enter the spinal cord and travel to the brain. Thus, pain is felt above the waist in the epigastric area (below the breastbone and between the ribs) rather than in the lower abdomen.
Causes of pancreatitis include alcoholism, cancer, hyperparathyroidism, abdominal trauma, drugs, infections and surgical procedures. According to S.J. McPhee and M.A. Papadakis in "Current Medical Diagnosis and Treatment," one of the primary causes is gallstones that lodge in the common bile duct, which carries both pancreatic enzymes from the pancreas and bile from the gallbladder. This blockage causes gallbladder inflammation as well as pancreatic inflammation and pressure on adjoining tissues, so often pain impulses are being sent to the brain from more than one area. Thus, pain may be defused across the upper abdomen rather than localised to one area.
As pain impulses travel along the nerves from the pancreas, they travel along the same nerve pathways as impulses coming from the right and left of the pancreas. When these impulses reach the brain, it can't always differentiate the origin of the pain impulse from the other impulses; so when the brain sends back an impulse that causes perception of pain, this message may go to adjacent areas. This is called referred pain. Pancreatitis pain is sometimes referred to the right and left sides and the back.
According to the Mayo Clinic, treating the underlying cause of pancreatitis (such as gallstones) is necessary to alleviate pain and allow the pancreas to heal. In some cases (such as alcoholism), pancreatitis may become chronic with bouts of acute pain or constant aching pain. Treatment includes a low fat diet, pancreatic dietary supplements, and no alcohol or opioids (narcotics) as these can worsen symptoms. Pain medications include acetaminophen and non-steroidal anti-inflammatory drugs (such as ibuprofen) and tricyclic antidepressants (often used for chronic pain). A nerve block of the coeliac plexus may alleviate severe pain.