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MedGenMed. 2006; 8(2): 38.
Published online May 11, 2006.
PMCID: PMC1785185

Obscure Gastrointestinal Bleeding – The Role of Endoscopy

Suryakanth R. Gurudu, MD, Assistant Professor of Medicine and Jonathan A. Leighton, MD, Associate Professor of Medicine


Obscure gastrointestinal bleeding (OGIB) is defined as bleeding of unknown origin that persists or recurs after an initial negative endoscopic evaluation including colonoscopy and/or upper endoscopy (esophagogastroduodenoscopy [EGD]).[1] OGIB can be classified as either: (1) occult OGIB, which is manifested by recurrent iron deficiency anemia and/or recurrent positive fecal occult blood test (FOBT) results; or (2) overt OGIB, which is manifested as melena or hematochezia.

Angioectasias of the small bowel are the most common source of OGIB in the elderly and account for 30% to 40% of gastrointestinal bleeding in this population,[2] whereas tumors such as leiomyomas, carcinoids, lymphomas, and adenocarcinomas are the predominant cause in patients aged 30 to 50 years.[3] Meckel's diverticulum is also a potential cause of bleeding and should be considered in the differential diagnosis.[4] Erosions and ulcers from nonsteroidal anti-inflammatory drug (NSAID) use[5] and Crohn's disease of small bowel are also potential causes of OGIB. Overall, OGIB accounts for 5% of all cases of gastrointestinal hemorrhage.[6]

Readers are encouraged to respond to George Lundberg, MD, Editor of MedGenMed, for the editor's eye only or for possible publication via email: ten.epacsdem@grebdnulg

Role of Endoscopy in the Evaluation of OGIB

Bidirectional Endoscopy

Colonoscopy and EGD are the initial tests of choice for investigation of occult blood loss. Bidirectional endoscopy refers to an investigative approach where colonoscopy and upper endoscopy are performed in sequence and in temporal relationship to the finding of occult bleeding.[7] However, despite examination of the gastrointestinal tract from both directions, the origin of gastrointestinal bleeding remains unexplained in as many as 52% of patients.[1] In various colon cancer screening trials, colonoscopy was performed in 78% to 86% of patients who had positive FOBT results. The predictive value of a positive FOBT ranged from 2.2% to 17% for colorectal cancer, and from 16.7% to 40% for adenomatous polyps.[810] In general, increasing age is associated with a higher prevalence of colonic neoplasia.[11,12]

Although EGD is reported to have low diagnostic yield for significant lesions in patients with occult bleeding and negative colonoscopy results,[13] gastric cancer was found in several studies that used bidirectional endoscopy for occult bleeding regardless of indication.[1,7,14,15] A simultaneous source of occult bleeding was found in both the upper and lower gastrointestinal tracts in approximately 6% (range, 1% to 17%) of patients.[1]

In OGIB, repeat EGD and colonoscopy with ileoscopy should be considered before performing a small bowel evaluation. A repeat EGD may yield a source even when the initial exam was negative.[1619] Zaman and colleagues[16] reported that 64% of lesions identified with push enteroscopy were within reach of a standard endoscope. Commonly missed lesions in the upper gastrointestinal tract include peptic ulcers, Cameron ulcers associated with large hiatal hernia, and angioectasias. Lesions often missed in the colon include angioectasias and neoplasms. The diagnostic yield of repeat EGD[16,17] is sufficient to recommend a second-look endoscopy. In the absence of clear evidence of gastrointestinal bleeding, small-bowel biopsies should be taken to rule out celiac sprue in the evaluation of patients with iron deficiency anemia.[14,15]

Push Enteroscopy

Push enteroscopy is an endoscopic procedure whereby a longer endoscope is inserted into the jejunum through the mouth to evaluate a larger segment of the small bowel. The diagnostic yield of push enteroscopy is approximately 40% to 65%.[16,19,20] A prospective study showed an increased yield from 41% to 67% in the evaluation of iron deficiency anemia.[21] Adrain and colleagues[22] noted positive findings in 78% of patients with OGIB, and an improvement in clinical outcomes, on the basis of hospitalization days and transfusions. In a study reported by Schmit and colleagues,[23] in which push enteroscopy was used in the evaluation of patients with iron deficiency anemia, angioectasias were the most common lesions identified and treated. Only 50% of cases had improvement in long-term outcomes as measured by recurrence of anemia or need for blood transfusions. Other studies show that push enteroscopy changes management in 40% to 73% of patients[17,18] and may improve clinical outcomes by reducing transfusion requirements.

Sonde Enteroscopy

Sonde enteroscopy involves the use of a long, flexible, fiberoptic instrument propelled through the small bowel by peristalsis; this procedure may allow for viewing the remainder of the small bowel. Sonde instruments rely on a balloon placed at the instrument's tip. Peristalsis then advances the long flexible endoscope to the distal small bowel, and the endoscopic examination is performed during withdrawal.[24] In contrast to push enteroscopy, this instrument has no biopsy or therapeutic capability. Thus, this procedure is not commonly used because of prolonged procedure time and the inability to perform biopsies or deliver therapy.

Capsule Endoscopy

Capsule endoscopy enables endoscopic evaluation of the entire small bowel. The capsule endoscope measures 26.4 mm in length and 11 mm in diameter. This device progresses through the small bowel, propelled by peristalsis. Images are transmitted at a rate of 2 per second from each end of the capsule to a recording device worn on a belt; these images are then downloaded to a computer workstation, where they are viewed by using proprietary software.[25] Several studies have shown that capsule technology is useful in the evaluation of OGIB and may have a higher diagnostic yield than push enteroscopy does.[2628] In a recent meta-analysis, capsule endoscopy was found to be superior to push enteroscopy and small-bowel follow-through for diagnosing clinically significant small-bowel pathology in patients with OGIB.[29]

Limitations of capsule endoscopy include its inability to provide therapy or precisely locate the site of the lesion. Capsule retention requiring surgical removal may also occur, and, therefore, capsule endoscopy should be used with caution in patients with potentially obstructing lesions and strictures, as well as in those with dysphagia.[30] Performing a small-bowel contrast study prior to capsule endoscopy has been advocated in patients with possible obstruction in order to rule out strictures – although it has not yet been shown that this will decrease the rate of capsule retention.

Double-Balloon Enteroscopy

Double-balloon enteroscopy is a new endoscopic technique for evaluating the small-bowel mucosa. This new technology allows for more extensive examination of the small bowel and also has therapeutic capabilities. The endoscope is 200 cm in length and has a balloon at the distal end. It also uses a 145-cm flexible overtube with a balloon, and a pump controller to inflate or deflate the balloons. The technique for advancement uses a push-and-pull method, with inflation and deflation of the balloons and telescoping of the intestine onto the overtube. This telescoping allows the endoscope to be inserted much further than the length of the endoscope itself, with minimal looping. The procedure can be performed in an antegrade and/or retrograde fashion.

When this technology was first introduced in 2001, Yamamoto and colleagues[31] were able to successfully examine 4 patients. This same group recently reported their experience with 178 double-balloon enteroscopy procedures (89 antegrade, 89 retrograde) and demonstrated the ability to examine the entire small bowel in 24 of 28 attempts (86%).[32] Among patients with OGIB, a source was identified in 50 (76%) cases. May and colleagues[33] reported their experience with 248 consecutive double-balloon enteroscopy procedures performed in 137 patients with suspected small bowel disease. The overall diagnostic yield was 80% (109/137). Most recently, Lo and colleagues,[34] in a multicenter trial, studied 188 patients who underwent 237 double-balloon enteroscopy procedures and found an overall diagnostic yield of 43% for patients with bleeding and/or anemia. Nine patients experienced complications. One patient had a peri-stomal perforation requiring surgical repair, 1 patient had a presumed microscopic perforation, and 1 patient had a mucosal tear which improved with conservative treatment. Four patients had abdominal pain, 1 patient developed aspiration pneumonia, and 2 patients developed respiratory distress. There is no evidence to suggest that the complication rate varies with the antegrade or retrograde approach. Double-balloon enteroscopy can be used to perform the full range of endoscopic therapies, including biopsy, tattooing, stricture dilation, foreign body removal, and argon plasma coagulation. The ultimate role of double-balloon enteroscopy in the diagnosis and management of OGIB remains to be explored.

Intraoperative Enteroscopy

Intraoperative enteroscopy during laparotomy may be used in patients with OGIB requiring multiple transfusions and/or repeated hospitalizations. The endoscopic evaluation has been performed orally, rectally, or through enterostomies at the time of laparotomy.[35] No controlled trials exist comparing this procedure with other techniques for the evaluation/management of OGIB. Ress and colleagues[36] reported their data in 44 patients who underwent intraoperative enteroscopy and found a source of bleeding in 70% of cases, although the therapeutic efficacy was only 41%. One study suggested a success rate of 82% when this procedure was used in conjunction with other localizing techniques.[37]

Nonendoscopic Methods

Small-bowel follow-through has been used to screen the small bowel for potential sources of bleeding. The yield of small-bowel follow-through in the evaluation of OGIB ranges from 0% to 5.6%.[38,39] Enteroclysis has a higher yield for small-bowel pathology when compared with small-bowel follow-through. The sensitivity of enteroclysis in detecting angioectasias, however, is also low.[40] Among patients with a negative push enteroscopy, enteroclysis identified a bleeding source in 8% of cases of OGIB.[41] Computed tomography enterography and magnetic resonance enterography represent newer imaging modalities that are being increasingly used in place of small-bowel follow-through.

Radioisotope bleeding scans may be helpful in cases of overt OGIB if the bleeding rate is in the range of 0.1 to 0.4 mL/min. This tool is most often used in the setting of active bleeding, where no source has been identified on routine EGD and colonoscopy. These scans can aid in localization of the bleeding source, which can then be managed endoscopically, angiographically, or surgically.[42] Angiography may also be helpful in the evaluation of overt OGIB if the bleeding rate is greater than 0.5 mL/min. Angiography is often used as a localization technique for embolization or prior to surgery.[43]


Endoscopy plays a major role in the evaluation of OGIB and the management approach is summarized in Figure 1.

Figure 1
Management approach to obscure gastrointestinal bleeding.

Patients with OGIB may present with either occult or overt bleeding. Repeat colonoscopy and EGD should be considered prior to evaluation of the small bowel, because lesions missed on initial exam are not uncommon. If no bleeding source is identified on upper and lower endoscopy, small-bowel evaluation with capsule endoscopy should be performed. On the basis of the findings, the clinician may proceed with push enteroscopy or double-balloon enteroscopy. Intraoperative enteroscopy should be reserved for patients with recurrent bleeding and transfusion dependency when no other source is determined. Once the diagnosis is established, appropriate medical and/or surgical therapy should be offered.

Contributor Information

Suryakanth R. Gurudu, Division of Gastroenterology and Hepatology, Mayo Clinic, Scottsdale, Arizona. Email: ude.oyam@htnakaytus.udurug.

Jonathan A. Leighton, Division of Gastroenterology, Mayo Clinic, Scottsdale, Arizona. Email: ude.oyam@nahtanoj.nothgieL.


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