When it comes to the abdomen, we distinguish between conditions within the lumen vs. those outside the lumen. The “lumen” is the digestive “tube” that begins in the mouth & throat, becomes the esophagus, joins into the stomach, and transitions directly with the small intestine, which connects into the large intestine (whose final segment is the rectum & anus). See Gastrointestinal System – Anatomy, with diagrams.
Acute conditions & diseases within the lumen include:
- Esophageal Reflux (heartburn); Esophageal Cancer
- Dyspepsia (indigestion or too much stomach acid); Gastritis; Ulcer, Stomach Cancer
- Staphylococcal gastroenteritis (food poisoning, from a bacterial toxin in the stomach)
- Viral or bacterial gastroenteritis (germs multiplying in the small or large intestine)
- Inflammatory Bowel Disease (Crohn’s; Ulcerative Colitis)
Distinguish these from abdominal diseases in the peritoneal cavity around the lumen, such as:
- Specific organs: liver, gallbladder, kidneys, uterus / fallopian tubes / ovaries
- Peritonitis: infection with the overall abdominal cavity
- Ulcers or cancers of the stomach or intestines can burrow into the organ walls, occasionally even perforating them to cause peritonitis
Tests to find diseases within the lumen include Endoscopy (for the esophagus, stomach, initial part of the small intestine) and Colonoscopy (large intestine). The entire small intestine is difficult to examine. The initial test “capsule enteroscopy,” where the patient swallows a small capsule with video camera inside, taking pictures of the entire small bowel as it passes along by peristalsis (the normal rhythmic propulsion of the bowel wall). If abnormalities are found, a “push enteroscopy” can try to reach it with a special instrument. I’ve been told that in some institutions, even when a Gastroenterologist orders a video-capsule exam, their colleagues may review the case to approve or disapprove it, since whoever reads the recording may spend 10 hours staring at bowel wall.