Correspondence

Occult Gastrointestinal Bleeding

N Engl J Med 1999; 341:1477-1478November 4, 1999

Article

To the Editor:

In his review article on occult gastrointestinal bleeding (July 1 issue),1 Dr. Rockey states that technetium-99m–labeled red-cell scintigraphy has been disappointing in regard to its influence on treatment. In the study he cites by Voeller et al.,2 however, the scintigraphy was performed with in vivo labeling of red cells, which is known to result in the presence of free tracer (that is, various chemical forms of technetium-99m that are not associated with red cells); the free tracer is in part eliminated or concentrated in the gastrointestinal tract. This nonspecific accumulation of free tracer in the bowel cannot be differentiated easily from extravasation of blood. It is not surprising, then, that with this technique there will be many false positives, false negatives, and nondiagnostic studies.

However, many other authors have documented the value of red-cell scintigraphy, with a sensitivity that ranges from 42 to 94 percent, and have reported correct localization of the site of bleeding in 52 to 97 percent of the cases.3-7 The study should be performed with red cells that have been labeled in vitro to minimize the presence of free tracer. Imaging should be continuous in a dynamic mode, at a rate of 120 frames per hour, and with repeating acquisitions until there is a positive finding or until four hours have elapsed. These images can be replayed in a cine mode, which facilitates detection and improves accuracy in localization.3,4

Technetium-99m–labeled red-cell scintigraphy is particularly useful for detecting lower gastrointestinal bleeding. In some cases of suspected lower gastrointestinal bleeding, the scintigraphic study will detect a gastroduodenal or small-bowel source instead. The continuous mode of imaging is also ideal for the detection of intermittent bleeding. When the correct technique is used and the results are interpreted properly, technetium-99m–labeled red-cell scintigraphy is a valuable tool for the diagnosis and localization of occult bleeding.

Vicente J. Caride, M.D.
Hospital of Saint Raphael, New Haven, CT 06511

7 References

1. 1

   Rockey DC. Occult gastrointestinal bleeding. N Engl J Med 1999;341:38-46
   Full Text | Web of Science | Medline

2. 2

   Voeller GR, Bunch G, Britt LG. Use of technetium-labeled red blood cell scintigraphy in the detection and management of gastrointestinal hemorrhage. Surgery 1991;110:799-804
   Web of Science | Medline

3. 3

   Emslie JT, Zarnegar K, Siegel ME, Beart RW Jr. Technetium-99m-labeled red blood cell scans in the investigation of gastrointestinal bleeding. Dis Colon Rectum 1996;39:750-754
   CrossRef | Web of Science | Medline

4. 4

   Suzman MS, Talmor M, Jennis R, Binkert B, Barie PS. Accurate localization and surgical management of active lower gastrointestinal hemorrhage with technetium-labeled erythrocyte scintigraphy. Ann Surg 1996;224:29-36
   CrossRef | Web of Science | Medline

5. 5

   Dusold R, Burke K, Carpentier W, Dyck WP. The accuracy of technetium-99m-labeled red cell scintigraphy in localizing gastrointestinal bleeding. Am J Gastroenterol 1994;89:345-348
   Web of Science | Medline

6. 6

   Bentley DE, Richardson JD. The role of tagged red blood cell imaging in the localization of gastrointestinal bleeding. Arch Surg 1991;126:821-824
   Web of Science | Medline

7. 7

   Winzelberg GG, McKusick KA, Froelich JW, Callahan RJ, Strauss HW. Detection of gastrointestinal bleeding with 99m Tc-labeled red blood cells. Semin Nucl Med 1982;12:139-146
   CrossRef | Web of Science | Medline

Author/Editor Response

Dr. Rockey replies:

To the Editor: Dr. Caride makes the point that technetium-99m–labeled red-cell scintigraphy can help in identifying the site of bleeding in a substantial proportion of patients with active obscure (and also lower) gastrointestinal bleeding. I agree entirely with the concept that technetium scans can aid in identifying sites of gastrointestinal bleeding. In fact, in my retrospective review (1992 through 1996) of technetium-99m–labeled red-cell scintigraphy in nearly 200 patients with either obscure or lower gastrointestinal bleeding, a site of bleeding was identified in 46 percent of the patients who underwent technetium-99m–labeled red-cell scintigraphy. However, despite the high frequency of positive scans, definitive surgical or interventional radiographic therapy was undertaken in less than 30 percent of the patients with a positive study.

The disappointing effect of technetium-99m–labeled red-cell scintigraphy on treatment is unquestionably related to any of a number of clinical factors that may have a role in determining whether a positive scan will ultimately lead to specific treatment. For example, patients with severe underlying diseases are often judged to be suboptimal candidates for surgery, so surgery is avoided. One might question the indication for the scan in this situation in the first place. Bleeding may stop spontaneously, making further intervention unnecessary. Finally, inherent limitations of the scans may preclude the extension of their findings to specific therapy, because technetium-99m–labeled red-cell scintigraphy does not allow the clinician to make a specific etiologic diagnosis. Thus, many clinicians are reluctant to recommend specific therapy or exploratory surgery on the basis of a positive study.

The practical experience of many clinicians further suggests that scans are not always used to guide further therapy. Indeed, to my knowledge, there are no data indicating an outcome advantage for patients who have undergone technetium-99m–labeled scintigraphy for any type of gastrointestinal hemorrhage. Thus, although technetium-99m–labeled red-cell scintigraphy should be viewed as a potentially useful adjunct in the management of gastrointestinal bleeding, whether its use results in a change in outcome for patients with obscure gastrointestinal bleeding (or lower gastrointestinal bleeding) is unknown. Therefore, further study is required to clarify the precise role of technetium-99m–labeled red-cell scintigraphy in the care of patients with gastrointestinal bleeding.

Don C. Rockey, M.D.
Duke University Medical Center, Durham, NC 27710