The human intestines are the longest part of the gut. It includes the small and large intestine, extending from the duodenum that is continuous with the stomach, to the rectum. The intestines occupy most of the abdominal cavity and the last portion of the large intestine dips downwards into the pelvic cavity. Most of the digestion, absorption of nutrients, re-absorption of water, the storage and subsequent evacuation of waste material occurs within the intestines. Therefore many intestinal diseases that result in pain will exhibit symptoms related to digestion, absorption and defecation.
What is intestinal pain?
Intestinal pain is any soreness or discomfort emanating from the intestines (bowels). It is often difficult to isolate pain to a specific internal organ, particularly with abdominal organs, since the abdominal cavity has the most amount of organs than any other cavity in the human body.
Furthermore these organs lies in close proximity to each other. However, pain that is in the approximate location of the intestines, accompanied by other symptoms that start within 30 minutes to several hours after eating is most like to be associated with intestinal pain.
Location of Intestinal Pain
Due to the length of the intestines, the location varies depending on the part of the intestines in question. Pain is often localized to specific areas that are diseased. A simple although not completely accurate reference for the location is that the small intestine is more centrally located in the abdomen while the large intestine is more towards the periphery. However, isolating the exaction location of abdominal pain is often difficult.
For convenience, abdominal pain can be divided into the four quadrants – right upper quadrant (RUQ), left upper quadrant (LUQ), right lower quadrant (RLQ) and left lower quadrant (LLQ). The nine abdominal regions may also be useful for localizing the area of the pain.
Small intestine location
The small intestine can be subdivided into the :
The duodenum is the shortest portion of the small intestine. It is a C-shaped structure that leads from the stomach outlet. It is located within the upper middle abdominal region (epigastrium) and the umbilical region. The rest of the small intestine is close to 6 feet long and is coiled within the abdominal cavity extending to the upper part of the pelvic cavity.
Large intestine location
The large intestine can be subdivided into the :
- colon (ascending, transverse, descending and sigmoid)
Most of the large intestine occupies the periphery of the front of the abdomen as compared to the small intestine which is more concentrated at the center of the abdomen. The location of the different parts are discussed in more detail under colon pain location.
Symptoms of Intestinal Pain
Although pain is a symptom on its own, the presence of other symptoms provides a more reliable indication of whether it is emanating from the intestine or some other organ within the abdominal cavity. Certain characteristics of the pain also helps to identify it more conclusively as intestinal pain. However, it should be assessed by a medical professional and diagnostic investigations such as an endoscopy or CT scan are often necessary.
The first and most important feature of pain that may be attributed to the intestines is the onset or worsening of pain after eating. Bowel transit time is the time taken for substances that enter the mouth to be passed out of the bowels as stool. This varies between 18 to 48 hours and sometimes as long as 60 hours. The time for food eaten to reach the small intestine cannot be easily measured due to the great degree of variability among individuals.
It takes 4 to 5 hours for all the stomach contents to empty into the small intestine. The first of the stomach contents enter the small intestine within 1 to 2 hours after eating with liquids entering even sooner. However, the onset of the pain depends upon the portion of the small intestine that is diseased.
Intestinal gas is a result of swallowing air while eating and gas produced by the chemical process of digestion as well as the breakdown of food by bacteria. Carbonated beverages also contribute to gas within the intestines. The excess gas in the upper part of the intestines may be passed out in the form of belching, while gas in the lower intestines is expelled as flatus.
However, the gas has to first reach either end of the gut in order to be passed into the environment. It can accumulate in the intestines to form gas pockets which can cause stretching of the intestinal wall. This can contribute to pain. Intestinal gas pain is more likely to occur in the colon particularly at the bends known as the hepatic flexure and splenic flexure which presents as pain under the right rib cage and pain under the left rib cage respectively.
Diarrhea is the passage of loose watery stool. It can also be defined as more than 200g or 200ml of stool in more than 3 movements within a day. It is one of the common symptoms of intestinal disease whether affecting the small or large intestine.
There are different mechanisms by which diarrhea occurs – intestinal movement is faster than normal, excess water is passed out into the intestinal lumen, water from the intestinal lumen is not reabsorbed to a sufficient degree. Depending on the intestinal disease, there may also be blood and mucus passed out in the stool.
The passage of hard stools with straining to defecate or less than three bowel movements in a week are all signs of constipation. There are various causes of constipation associated with slower than normal or disordered bowel motility, lack of fiber, insufficient water in the bowels and bowel obstruction.
Yet a significant number of causes occur for no known reason. A large number of cases are associated with problems in the large intestine and therefore symptoms may be isolated to this area.
- Abdominal distention – enlargement of the abdomen.
- Bloating – sensation of fullness.
- Nausea and vomiting.
- Fatty stools.
Causes of Intestinal Pain
There are a number of conditions that may cause intestinal pain. Some of these conditions may be isolated to the small intestine or large intestine only while other conditions may affect any part of the gut. This is discussed further under the upper and lower intestines.
Upper Intestinal Pain
These are conditions that affect the small intestine including most of the ileum.
- Duodenitis is inflammation of the duodenum often associated with gastritis (stomach inflammation).
- Duodenal ulcers are open sores that develop in the inner lining of the duodenum.
- Pancreatitis is inflammation of the pancreas and while it is not part of the intestine, it may cause intestinal symptoms due to the disruption of digestion.
- Gallstones are sediments of bile that can obstruct the outflow of bile. The pain is largely due to its obstruction of the bile ducts but it can also cause intestinal symptoms.
- Gastroenteritis is inflammation of the stomach and intestine as a result of an infection with viruses, bacteria, fungi or parasites.
- Enteritis is inflammation of the small intestine which can occur with the stomach inflammation (gastroenteritis) as mentioned above or colon inflammation (enterocolitis).
- Small intestinal bacterial overgrowth (SIBO) is a larger than normal concentration of bacteria in the small intestine often with species of colonic bacteria.
- Irritable bowel syndrome (IBS) is a functional bowel disorder and the exact part of the gut that is affected cannot be easily identified. However, it appears to be a problem with normal gut motility as a whole and painful intestinal cramps could occur within the small or large intestine.
- Inflammatory bowel disease (IBD) is a bowel disorder marked by chronic inflammation. Crohn’s disease can affect any part of the gut while ulcerative colitis is restricted to the large intestine.
- Small intestine obstruction may be due to masses, twisting of the bowels and narrowing of the intestines. There may be partial or complete bowel obstruction.
- Small intestine cancer is a malignant tumor that originates from the tissue of intestinal wall or spreads to it from a distant site. The most common type is an adenocarcinoma arising from the glandular tissue of the small intestine wall.
Lower Intestinal Pain
Conditions of the lower parts of the intestine (large intestine) often involves the last parts of the ileum as well. The main conditions have been discussed further under colon pain. This includes conditions such as :
- Bowel infarction
- Colon obstruction
- Colorectal cancer
It is also important to consider the various other causes of organ pain within the abdominal cavity lying in close proximity to the colon. This includes :
Last updated on September 22, 2018.