The small intestine, also called the large intestine, is a part of the digestive system. It, therefore, participates in digestion and absorbs nutrients. It can be affected by various pathologies, from Crohn's disease to ulcers, including gluten intolerance.
1. Definition of the small intestine
The small intestine originates at the pyloric sphincter of the stomach, winds through the middle and lower parts of the abdominal cavity, and opens into the large intestine. It measures on average 2.5 cm in diameter and about 6.35 m in length.
The small intestine is divided into 3 segments. The duodenum, the shortest part, originates at the pyloric sphincter of the stomach and extends for about 25 cm, then merges with the jejunum. The jejunum is about 2.5 m long and extends to the ileum. Finally, the ileum is 3.6 m long and joins the large intestine at the ileocecal valve.
2. What is the role of the small intestine?
Most of the digestion and absorption of nutrients takes place in the small intestine. The wall of the small intestine is made up of the same 4 tunics as the rest of the digestive tract. However, its mucosa and submucosa are adapted to allow the small intestine to complete the processes of digestion and absorption.
3. What are the pathologies of the small intestine?
There are many pathologies affecting the small intestine. Among them are Crohn's disease, celiac disease, and peptic ulcer.
Crohn's disease is a chronic inflammatory disease of the intestine that usually affects young people (peak diagnosis in the 20-30 age group) and more particularly women. Crohn's disease is responsible for chronic inflammation and thickening of the intestinal wall which progressively leads to a loss of the physiological functioning of the intestine. The evolution of the disease over time is associated with the appearance of intestinal complications such as strictures, ulcers, perforations, fissures, or abdominopelvic abscesses. These lesions can affect the entire digestive tract, from the esophagus to the rectum.
Crohn's disease progresses in flare-ups. It can affect different parts of the digestive tract. When it affects the esophagus and the beginning of the small intestine, it causes heartburn and acid reflux. However, when it affects the end of the small intestine, the symptoms are a pain in the right lower abdomen, nausea, and diarrhea, which may last for several weeks. When the relapse lasts over time, it can lead to fatigue, anemia, malnutrition, and weight loss. Periods of remission between relapses may last a few weeks, months, or even years. It is difficult to predict the frequency of attacks.
It should be noted that in about one-third of cases, Crohn's disease affects only the small intestine and especially its terminal part (ileum).
Celiac disease, also known as gluten intolerance, is a chronic autoimmune disease of the small intestine linked to the ingestion of gluten. Gluten is formed when the grains of certain cereals (wheat, barley, rye, etc.) are hydrated. In affected patients, the absorption of gluten proteins, particularly gliadin, causes an abnormal reaction of the immune system. This autoimmune reaction eventually causes inflammation and damage to the inner lining of the intestine. In fact, it will atrophy the villi (folds) of the intestinal mucosa, which will considerably alter intestinal absorption. Thus, in addition to causing digestive manifestations such as chronic diarrhea, bloating or constipation, this phenomenon can also be the cause of deficiencies by malabsorption of nutrients, minerals, and vitamins. In children, celiac disease can cause growth disorders with a break in the weight-status curve.
Gluten intolerance appears progressively and settles in over time. The disease is quite frequent, but it sometimes goes unnoticed for several years.
A peptic ulcer is a frequent pathology and corresponds to the formation of a deep wound in the wall of the duodenum. Painful, these wounds are in direct contact with the acidity of the digestive tract. The ulceration is often due to bacterial growth (Helicobacter pylori, in the case of gastric ulcers), but it can also occur as a result of certain medications. The disease affects more particularly subjects over 40 years old.
Peptic ulcers can be complicated by bleeding or a complete perforation of the wall of the digestive tract. In these cases, it is a medical-surgical emergency.
4. How to treat pathologies of the small intestine?
The treatment of Crohn's disease is based on medication, including substances designed to reduce the activity of the immune system: anti-inflammatory drugs and immunosuppressants. Corticosteroids in particular can rapidly improve attacks, but also prevent relapses. Maintenance treatment outside of relapses allows for better control of the disease and the avoidance of possible complications. Surgical treatment is sometimes considered. It may consist of removing the part of the intestine that is causing the complications, treating abscesses, or removing fistulas.
The treatment of celiac disease consists of avoiding all ingestion of gluten throughout one's life, whether the condition is severe or mild. It is important to note that a gluten-free diet should not be started until the diagnosis of celiac disease has been medically confirmed. In most cases, the evolution is favorable with complete regrowth of the intestinal villi after approximately one year, provided that a strict gluten-free diet is followed. The first cause of treatment failure is poor compliance with the gluten-free diet, whether voluntary or not. As gluten is often used in food products and found in many products and preparations, it is sometimes difficult to follow a strict gluten-free diet. However, a strict gluten-free diet is crucial, even in the absence of symptoms, because it prevents the insidious development of osteoporosis, but also of other autoimmune diseases, and exceptionally cancers (intestinal lymphoma, etc.). The patient can be referred to a dietician to help him/her set up and maintain his/her diet.
The treatment of peptic ulcers is primarily medical. It includes medications that reduce acid secretions from the stomach (proton pump inhibitors). The objective is to allow the healing of the ulcerous lesion and prevent a recurrence. Surgical management is reserved for complicated cases.
5. Who are the small bowel specialists?
A gastroenterologist is a doctor who specializes in the digestive system. His or her field of expertise covers pathologies of the rectum, large intestine, small intestine, stomach, pancreas, liver, gallbladder, and esophagus.
The treating physician will therefore refer the patient to a gastroenterologist if he or she presents worrying digestive symptoms. People of all ages can be affected by digestive system disorders. If the patient requires bowel surgery, he or she will be referred to a visceral surgeon who specializes in bowel surgery.
6. What are the diagnostic tests?
In the case of Crohn's disease, ileocoloscopy is the diagnostic test that consists of observing the wall of the large intestine and the ileum using a flexible endoscopic probe introduced through the anus and equipped with a light and a camera at its end. It allows visualizing signs of inflammation and fragility of the intestinal wall, as well as ulcers. The examination is done under general anesthesia and requires a colonic preparation (intestinal washing) and a diet without residues the days preceding the examination so that the intestine is emptied of its contents. The examination will thus be more efficient and of better quality.
In patients for whom endoscopic examinations are not feasible, other complementary examinations can be prescribed for exploration such as, for example, MRI (magnetic resonance imaging), entero-scanner (radiating examination using X-rays) or abdominal ultrasound. These examinations, especially MRI, are useful in the event of Crohn's disease flare-ups and allow the extent of the lesions and inflammation to be assessed, as well as any abscesses or fistulas, for example.
A biological assessment (blood test) can also be used to look for anemia, inflammatory syndrome, or vitamin deficiencies, among other things.
To diagnose celiac disease, the test of choice is the determination of a specific antibody in the blood: the immunoglobulin A (IgA) anti-transglutaminase antibody. Adults with a positive serological test are referred to a hepatogastroenterologist for biopsies of the duodenal mucosa. These samples are taken by upper digestive endoscopy and allow confirmation of the diagnosis by observing the atrophy of the villi. The biopsy will also allow visualization of lymphocyte proliferation (immune cells).
The diagnosis of celiac disease in children can sometimes be made without a biopsy if the symptoms are typical and if the blood levels of antibodies are very high.
Sources :
VIDAL - Ulcère gastroduodénal : prise en charge ulcère gastro-duodénal
Société Nationale Française de Gastro-Entérologie - Maladie coeliaque
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