The American Gastroenterological Association in 2007 defined the terms that we use to describe chronic blood loss. Occult bleeding is defined as a positive fecal occult blood sample on initial evaluation; or it is defined as iron deficiency anemia, without any signs of physical bleeding. The term obscure bleeding is defined as; bleeding that persists even after evaluation following an endoscopy, colonoscopy, and radiograph imaging.
Obscure bleeding accounts for approximately 5% of all GI bleeds; 75% occur in the small intestines while the rest are associated with lesions of the upper or lower gastrointestinal tract.,, Depending on the location in the small intestine or the age of the patient, many etiologies exist for the cause of the bleeding.
Finding the source of the bleed is of the utmost importance; the search is guided by clinical presentation, physical findings, and the results of various imaging techniques.
Wireless video capsule endoscopy (CE) is a safe, non – invasive, and sensitive method for the evaluation of obscure bleeding. Approved in 2000, many studies have come out to determine the efficacy, quality, and capabilities of this new method of evaluation. CE has been shown to determine the cause of obscure GI bleeding in 60.5% of the time. It’s use in the diagnosis of a patient with suspected Chron’s disease, as well as in the management of active Chron’s disease is also important. In patients who are suspected of having Chron’s, capsule endoscopy has shown to have a detection rate of 55%. This is comparable to the 48% detection rate of colonoscopy, and is superior to the use of imaging modalities such as x-ray and CT, which have detection rates of 22% and 31% respectively.
While there are many advantages to this technique, there are limitations. Firstly, the capsule only allows for detection of the lesion alone and not concomitant treatment. It also may pass erratically through the intestines resulting in a missed lesion. Studies have reported that the use of this technique on patients who have pacemaker’s and/ or defibrillator’s is not safe. However this concern is steadily dropping as evidence grows that it is safe to use in the presence of these devices.
The main concern regarding this technique is the risk of the capsule remaining in the GI system. Retention occurs in approximately 1.4% of patients and can be due to strictures, NSAID use, or previous abdominal surgery resulting in the development of adhesions. A previous concern wuth the use of the capsule was that it was contraindicated in pediatric patients and in patients with dysphagia. However, now there is a technique to deliver the capsule directly into the small intestine, and allows for the use of the capsule in patients that it was once thought to be contraindicated in.
Enteroscopy involves the use of a colonoscope or a specialized enteroscope to visualize the intestine beyond the ligament of Treitz. In 2003, the introduction of the double balloon enteroscope (DBE) allowed for the visualization and inspection of the entire small bowel, including the duodenum, jejunum, and proximal ileum, with the use of a overtube and a balloon that secures the walls of the intestine and allows for the advancement of the scope. It is usually performed in a combined retrograde and anterograde approach.
When considering the two modalities, it is important to decide which method has a higher diagnostic yield. CE has the advantage of being the most non- invasive procedure; however, it is not a real time procedure, therefore the identification of interventions is not possible. In comparison with the use of capsule enteroscopy, which can only give a rough estimate for the location of the lesion, DBE can be use for localization, taking biopsies, and for the use of targeted therapies such as, polypectomy, epinephrine injection, thermocoagulation, stent placement, and retrieval of foreign objects, including but not limited to a retained CE. While this method seems advantageous for the diagnosis and treatment of the bleed, it is a very labor-intensive procedure; average surgical time varied from 73 – 123 minutes., DBE is also an invasive procedure, requiring anesthesia, and a skilled surgical endoscopist.