The small intestine (small bowel) is responsible for the majority of nutrient absorption in the digestive tract. For many years, physicians struggled to gain a full view of this lengthy, coiled structure using standard endoscopic tools. Specialized medical procedures have now made it possible to visualize the entire small intestine, moving past the limitations of traditional scopes. This breakthrough allows doctors to precisely diagnose and treat a variety of conditions previously hidden from view.
Why the Small Intestine is Difficult to Reach
The primary challenge in scoping the small intestine is its length and anatomical position within the abdomen. The small bowel is the longest segment of the digestive tract, measuring approximately 20 to 22 feet (6 to 6.5 meters) in an adult, despite its name referring to its narrower diameter compared to the large intestine. This long segment is coiled and suspended within the abdominal cavity, making navigation difficult for rigid or semi-rigid instruments.
Traditional upper endoscopy (EGD) can only examine the esophagus, stomach, and the first part of the small intestine (the duodenum). A standard colonoscopy only reaches the end of the small intestine, specifically the terminal ileum. The vast middle section, which includes the jejunum and most of the ileum, remains inaccessible to these conventional scopes. This anatomical gap necessitated the development of new techniques to explore the full extent of the small bowel.
Advanced Endoscopic Visualization Techniques
Overcoming the challenge of the small intestine’s length required the development of two distinct types of advanced procedures: non-invasive diagnostic tools and invasive therapeutic systems. The non-invasive approach is Capsule Endoscopy (CE), which involves the patient swallowing a small, pill-sized device. This capsule contains a camera, light source, battery, and radio transmitter, capturing thousands of images as it is propelled through the small bowel. The pictures are wirelessly sent to a recorder worn by the patient, and the capsule is later passed naturally, providing a detailed visual survey of the entire small intestine.
A major limitation of capsule endoscopy is that it is purely diagnostic; it cannot perform therapeutic actions like taking a biopsy or stopping a bleed. For intervention, Balloon-Assisted Enteroscopy (BAE) is used, involving a specialized, flexible scope designed to navigate the entire small bowel. This method, which includes single-balloon and double-balloon variations, uses an endoscope inserted through the mouth or rectum, coupled with an overtube that has one or two inflatable balloons. By alternately inflating and deflating the balloons, the physician can pleat or gather the small intestine onto the overtube, effectively shortening the bowel segment to push the scope deeper.
Balloon-assisted enteroscopy allows the physician to perform therapeutic interventions not possible with a capsule, such as removing polyps, cauterizing bleeding sites, and taking tissue samples. Another related technique is Spiral Enteroscopy, which uses a specialized rotating spiral attachment on the tip of the overtube. As the spiral rotates, it gently grips the bowel wall and helps pull the small intestine onto the scope, allowing for deep insertion and therapeutic capabilities. Both balloon and spiral techniques overcome the anatomical challenge by creating a stable platform to manipulate and shorten the gut, allowing for direct visualization and treatment.
When Small Intestine Scoping is Necessary
These specialized scoping procedures are reserved for situations where standard upper and lower endoscopies have failed to determine the cause of a patient’s symptoms. The most frequent indication for small intestine scoping is the investigation of obscure gastrointestinal bleeding (OGIB). OGIB is defined as persistent or recurring bleeding from an unknown source after a negative evaluation of the upper and lower GI tract. Since the small bowel is often the source of this bleeding, capsule endoscopy is frequently the first step to locate the problem area.
Once a lesion or bleeding site is identified, a balloon-assisted enteroscopy can be performed to reach that specific location, confirm the diagnosis with a biopsy, or treat the bleeding. Beyond bleeding, these procedures are also used to evaluate the extent and severity of Crohn’s disease, a form of inflammatory bowel disease that commonly affects the small intestine. Scoping can identify areas of inflammation, ulceration, and strictures, which are abnormal narrowings of the bowel.
Specialized scoping is also required for the detection of small bowel tumors (benign or malignant) and to diagnose complications of Celiac disease, such as refractory celiac disease or small bowel lymphoma. The ability to visualize and sample tissue from the jejunum and ileum is crucial for accurate staging and treatment planning. Using these advanced techniques, physicians can often avoid more invasive surgical options that were once the only way to examine the small intestine.