The small intestine plays a central role in the digestive system, managing the breakdown of food and absorbing nutrients into the bloodstream. This long, coiled organ, measuring about 20 feet in length, presents unique challenges for examination due to its extensive folds and intricate structure. When digestive issues arise that cannot be explained by problems in other parts of the gastrointestinal tract, specialized diagnostic approaches become necessary to investigate this complex region. These methods help pinpoint the underlying causes of various symptoms and guide appropriate medical interventions.
Why a Small Intestine Check is Needed
Patients often seek medical attention for persistent symptoms that may point to issues within the small intestine. These indicators commonly include chronic abdominal pain, unexplained weight loss, and ongoing diarrhea that does not resolve with standard treatments. Anemia or gastrointestinal bleeding that cannot be traced to the upper or lower digestive tract, frequently prompts investigation of the small intestine. Such symptoms suggest the organ may not be functioning correctly or could harbor an abnormality.
These investigations identify a range of conditions affecting the small intestine. For instance, inflammatory bowel diseases like Crohn’s disease can cause chronic inflammation and damage. Celiac disease, an autoimmune disorder, leads to damage of the small intestine lining when gluten is consumed. Checks can also uncover sources of bleeding, such as angioectasias or ulcers, or detect the presence of tumors, including lymphomas or adenocarcinomas.
Capsule Endoscopy
Capsule endoscopy offers a non-invasive way to visualize the small intestine. During this procedure, a patient swallows a small, pill-sized camera, measuring about 11 by 26 millimeters. This miniature device contains a light source, a battery, and a camera that captures images as it naturally moves through the digestive tract by peristalsis. The patient wears a portable data recorder on a belt, which wirelessly receives images transmitted by the capsule over an eight-hour period.
The capsule captures two images per second, creating thousands of detailed pictures of the small intestine’s internal lining. After the procedure, a physician downloads these images from the data recorder and reviews them on a computer screen to identify any abnormalities. This method is particularly useful for detecting obscure sources of gastrointestinal bleeding, areas of inflammation consistent with inflammatory bowel disease, or small tumors. The capsule passes naturally from the body within 24 to 72 hours, and does not need to be retrieved.
Advanced Endoscopic Procedures
When more direct intervention or detailed visualization is required, advanced endoscopic techniques are employed to examine the small intestine. Push enteroscopy involves inserting a long, flexible scope, similar to an upper endoscope, through the mouth and advancing it as far as possible into the jejunum. This method allows for direct visualization and therapeutic interventions in the proximal small bowel.
To explore deeper into the small intestine, balloon-assisted enteroscopy, either single or double-balloon, is utilized. These procedures involve a specialized endoscope equipped with one or two balloons that inflate and deflate, allowing the scope to be “pleated” over the long, coiled segments of the small intestine. This “accordion” technique enables physicians to navigate through significant lengths of the small bowel, either antegrade (through the mouth) or retrograde (through the anus). These advanced methods facilitate taking biopsies of suspicious tissue, removing polyps, or treating active bleeding sites identified by previous capsule endoscopy. Patients receive sedation for these procedures to ensure comfort during the examination and recovery.
Radiological Imaging
Various radiological imaging techniques provide indirect views of the small intestine, offering valuable information without requiring endoscopic insertion. CT enterography and MRI enterography are common methods that involve the patient consuming a large volume of an oral contrast solution to distend the small bowel loops. This distension allows for clearer visualization of the intestinal wall and lumen. Intravenous contrast material is also administered to enhance blood vessels and inflammatory processes.
These scans can reveal signs of inflammation, such as bowel wall thickening, strictures (narrowing), or fistulas (abnormal connections between organs). They are also effective in identifying tumors or other structural abnormalities. CT enteroclysis and MRI enteroclysis are similar but involve direct administration of contrast material into the small intestine via a nasojejunal tube for more consistent distension. Traditional barium follow-through studies were historically used but have largely been superseded by CT and MRI due to their superior soft tissue resolution and ability to detect subtle changes.
Laboratory and Breath Tests
Beyond direct visualization, several laboratory and breath tests offer indirect insights into small intestine health. Blood tests can detect specific markers that indicate underlying conditions. For instance, tests for tissue transglutaminase (tTG) antibodies or endomysial antibodies (EMA) are commonly used to screen for celiac disease. Inflammatory markers like C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) in the blood can suggest generalized inflammation, which might originate in the small bowel.
Breath tests are particularly useful for diagnosing conditions related to bacterial activity or malabsorption. The hydrogen breath test for small intestinal bacterial overgrowth (SIBO) involves ingesting a sugar like lactulose or glucose. If an overgrowth of bacteria is present in the small intestine, they ferment the sugar and produce hydrogen or methane gases, which are then detected in the patient’s exhaled breath. Similarly, lactose intolerance can be diagnosed by a breath test that detects hydrogen production after lactose ingestion. Stool tests can also provide clues, such as identifying fat in the stool (steatorrhea), which indicates malabsorption, or detecting markers of inflammation like fecal calprotectin.