I have the same problem. At first the pressure got really bad only at certain times of the night, almost felt like something was going to burst! I could actually feel my pulse pounding in the lower part of my back or left side of abdomen. I also noticed that I had been constipated for a while. a few weeks before this occured I had a severe bout of acid reflux for several weeks and I treated with tums and it went away. Yesterday I was still having the same symptoms after a week and went to the doctor. He explained that Acid Reflux could do this and cause inflamation throughout my digestive system. I did notice that the few times I was able to go to the bathroom and make a bowl movement that it burned, so it does make sense. He prescribed Nexium and told me to chill for a few days to see if the symptoms go away. He collected a urine sample to test for any kidney or liver abnormalties. Today I still had some pressure, so I'm not so sure I might not have a multi symptom and something going on with the kidney such as and Infection. I did have a bad bladder infection a few months ago, so I am sure something will show up on the urine test if that is the case. If not it was a result of inflammation due to acid reflux and the devistation in can cause. I would advise anyone who has these symptoms to not ignore it as heartburn because it can cause a lot of problems as well as cancer of the Esophigus and digestive tract!