Bloat, acid reflux, irritable bowel syndrome, inflammatory bowel disease (Crohn's, ulcerative colitis), and most other conditions of the gastrointestinal tract follow these stages in pathoprogression.
The gastrointestinal tract (GI tract) operates from the mouth to the anus. The primary functions are digestion, filtration, assimilation, and elimination using an orchestration of interactions resulting in immune protection, nutrient acquirement, and removal of harmful agents. Loss of function in any aspect of this orchestration will result in the next stage (irritation).
The Loss of Function stage can be divided into two sub-categories: external difficulty (hard to digest food or contaminated food) and internal competency (strength of GI tract functions). The stronger the latter the greater the former can be handled without issue. However, if the functions of the GI tract are poor (due to nutrient deficiencies, infection, functional disorders such as dysmotility, hypochlorhydria, biliary stasis, etc., or congenital causes) then the ability to handle challenging foods is reduced resulting in irritation. If GI tract functions are very strong then more challenging foods can be consumed without issue ("cast iron stomach"). An example is an infant. Because their digestive abilities are undeveloped they are given pre-cooked mush. Giving them pizza would be disastrous. Same applies to a patient that is severely compromised in function. They may need to eat foods that are very easy to digest until the underlying issues are treated.
After digestive function has been compromised then irritation begins. Imagine someone lightly tapping your arm in the same spot. It wouldn't hurt at first but after an hour it would be irritated. Image the same irritation going on for months or years. That is what is occurring in the GI tract when function declines. During this stage there may be bloat and stool pattern change but if there was an endoscopic or colonoscopic exam there would be no visual sign of inflammation. If there is gas there will be a sense of fullness relieved by passing the gas but no pain.
During this stage the irritation has continued long enough for the tissues to become swollen and inflamed. Camera examinations will show visual signs of redness. During this stage there will be pain when there is gas as the gas creates pressure against the inflamed segment of the intestines. The stool pattern changes may worsen and include cramping followed by sense of urgency stool. This happens when the intestines are sensitive and contents are pushed out as a protective mechanism to prevent more inflammation.
During this stage the mucosal lining has been compromised exposing the soft tissue of the intestinal lumen. The hallmark symptom of this stage is pain lingering in one spot. It is likely an ulcer or gastritis. Mucus may also be seen in the stool. Treatment strategies must include repair of the mucosal lining.
This stage is dangerous. By now the wounds are turning into scar tissue which operates like the living dead. It is vascular but non-functional. The scarred patches will not produce any protective mucosal lining and assimilation and filtration functions will be compromised. There will also be dysmotility. It is in this stage that necrotic tissue can trigger an autoimmune response which transitions the patient from IBS category to IBD.
Oncogenesis is complicated involving multi-system breakdown, genetics, and lifestyle. However, in this stage cancer risk increases dramatically as the body is no longer able to regulate mutant cell growth patterns.