I'm curious if an answer was ever found. I have been experiencing the same scenario for the past month. This is an old post so I won't get into much detail regarding my issues.
I just noticed that you mentioned that they did not use contrast... My first obstruction was when I was three months pregnant and when they finally had not choice but to do an x-ray it finally showed up, but just barely and that is with the contrast... I ended up having emergency surgery the next morning. More recently I had another x-ray as I fear it is happening again (something they said was very likely) but they did not use contrast and nothing showed up. The Dr. seemed satisfied that a neg X-ray must mean nothing is wrong. I know better than that so I am now in the process of getting a referral to see the GI/surgeon who took care of me last time and I'm hoping that he will be more thorough. Just be careful. If you wait to long parts of your bowel can start to die from not receiving enough blood and they may have to remove those portions. If you don't mind me asking, what type of abdominal surgery did you have? I had Gastric Bypass in August 2003 and my obstructions were 18 months post op (11/04) and 3 years after that (12/07).
Thank you both for the suggestions and the support! I really appreciate it. I was very dismayed that the ER doc refused to use any contrast when he ordered my CT. But, you know, no one wants to listen to the "little people". I'm just getting so mad because even water and Gatorade are making me nauseated. I will try some of the suggestions, like changing my diet and I've agreed to take the Nexium as prescribed and stopped drinking my favorite beverage-Diet Pepsi. I just want someone with an MD to tell me what's going on! I appreciate it and I will keep updating this blog as I get information.
If a stool culture has not been done, it is probably a good idea to suggest it. You may have a bacterial imbalance in the GI tract. An ER will not do this (they actually do very little unless you are dehydrated, bleeding, have a broken bone, appendicitis, or a bacterial/fungal infection). Since you have had a CT scan done already and are on your way to the GI doctor, be sure to take copies of the films with you so he can look at them during your visit. If the CT was done in the ER, the test may have been insufficient for detecting problems due to image contrast. If no contrast agents were given (such as barium sulfate or intavenous iodine), then unfortunately the intestines may not be very visible in the test. Bowel obstructions are very serious conditions, and would likeley cause excruciating pain (as Herten33 has described). If this is your suspicious, a trip to the ER with a list of demands is suggested.
Given that you have a preliminary diagnosis of IBS or an ulcer, you may want to try strategies for symptom management of those diseases while you are waiting. My wife is also diagnosed with IBS, so we are very familiar with some common food triggers that will set off a flare. Try to stick to fairly bland foods that are high in soluble fiber, while low in insoluble fiber. This means that you should skip the salads, and raw foods in general are a bad idea. Any foods that have a high fat content can irritate the intestines, so try to avoid adding more fat than necessary to your diet (a few tablespoons of cooking oil a day tends to be okay). Since you don't eat meat, I assuming that the majority of your protein either comes from soy or nuts (we are also vegetarians). Nuts have a large amount of fat by weight, and can cause problems. They will also hang out in the stomach to soak in acid before moving on to the small intestine, which may aggrevate a peptic ulcer. Try sticking to traditional staple foods like rice, potatoes, beans (soaked & well cooked to avoid gas), bean sprouts, & breads. These foods move quickly through the digestive system, and can supply ample calories and protein until you can get a handle on what is going on. There are many websites out there that list food combinations for obtaining complete proteins while avoiding meats (see http://www.weightlossforall.com/protein%20combinations.htm). I hope this helps.
I'm not a doctor, however I have had similar pain and similar problems diagnosing it. Turns out I had a small bowel obstruction that had previously been diagnosed as an ulcer. Mine did show up in a CT but I believe they checked my whole abdomen not just my kidneys. In all honesty I was in so much pain I don't remember every part of that night. As you mentioned it was the WORST pain I have ever been in - way worse than child birth or Gastric Bypass. Anyways, I don't know for a fact this is what you are suffering from, but it does sound similar to what I had. I would get help ASAP because if this is the problem it can be very serious. Good luck!