Hi, If I were your treating Doctor for this case of severe pain, I would come up with possibilities, these include: The possibility is of pancreatitis as it may cause left abdominal pain which is worse when bending over or sitting. Pancreatic enzymes like serum amylase and lipase should be measured to rule out any pancreatic cause. The last possibility is of any kidney stones which may present as such sharp pain radiating to the back. For this purpose you need to get an ultrasound abdomen and kidneys done. I suggest you to consult a physician and get an ultrasound upper abdomen,urine r/e and if needed serum amylase and lipase. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate to ask. I will be happy to answer your questions. Wishing you good health.