Today, I review, link to, and embed Appendix S5 Gastroenterology Perspective: Comparison of Advantages and Limitations Relative to Endoscopic Examinations from The Role of Imaging for GI Bleeding: ACG and SAR Consensus Recommendations [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. Radiology. 2024 Mar;310(3):e232298. doi: 10.1148/radiol.232298.
All that follows is from the above resource.
Appendix S5 Gastroenterology Perspective: Comparison of Advantages and Limitations Relative to Endoscopic Examinations
Overt lower GI bleeding.—
Role of colonoscopy:
Colonoscopy has long been considered the diagnostic test of choice in patients presenting with suspected colonic bleeding, due to the ability to determine the etiology of bleeding, allow for
mucosal biopsy, and potentially provide a therapeutic intervention. In large international cohorts, colonoscopy has been shown to have a diagnostic yield of nearly 80%, with rates of therapeutic intervention as high as 21% in patients undergoing colonoscopy within 24 hours of presentation (14). Despite the high diagnostic yield of colonoscopy, rates of endoscopic intervention seem to be significantly lower in American cohorts where colonoscopy is not performed emergently, ranging from 3%–6% (15–17). Moreover, colonoscopy is an invasive procedure carrying risks of
sedation in patients with significant cardiopulmonary comorbidities, and requires a bowel preparation to adequately locate and treat stigmata of hemorrhage. Colonoscopy should be
performed only after the patient is hemodynamically stable and after adequate colon cleansing. Studies suggest that urgent colonoscopy within 24 hours does not improve outcomes (18).Role of CTA versus colonoscopy:
Advantages of CTA over colonoscopy include the ability to rapidly obtain images without the need for sedation or a bowel preparation. Patients presenting with severe hematochezia despite resuscitation may be unlikely to tolerate bowel preparation, and thus may benefit from performance of an initial CTA to localize the site of bleeding. Conversely, patients with stable hematochezia or severe hematochezia which resolved with resuscitation are unlikely to have extravasation seen on a CTA, and thus may benefit from a nonurgent colonoscopy to determine the etiology of bleeding. Patient level variables which have been shown to be predictive of a positive CTA include recent bowel resection, transfusion of greater than 3 units of packed red blood cells per day, use of antiplatelet medications, tachycardia, hypotension, and performance of CTA within 4 hours of hematochezia (19,20). Mortality rate data were unavailable in these two studies.
Use of 99 mTechnetium-labeled RBC scintigraphy has fallen out of favor compared with CTA, due to relatively long duration of the study as well as the inability to precisely localize the site of bleeding. In retrospective studies of patients with LGIB receiving CTA as compared with RBC scintigraphy, CTA was more accurate in detecting and localizing the source of lower
gastrointestinal bleeding (21,22). Mortality rates were not significantly different in patients getting CTA or scintigraphy (22).Colonoscopy versus CTA for initial testing:
There is limited available data comparing outcomes for patients undergoing colonoscopy versus CTA as their initial diagnostic testing. Small observational studies have shown that CTA was
noninferior to colonoscopy in terms of bleeding site detection, and CTA may lead to a reduction in time to first examination and a higher frequency of detecting active bleeding as compared with colonoscopy (23,24). In a recent single center comparison of CTA to colonoscopy, colonoscopy was associated with a higher probability of source identification, however in the subgroup of patients with diverticular bleeding, CTA led to higher rates of therapeutic intervention (25).Management of a patient with a positive CTA
Hemodynamically unstable patients with extravasation demonstrated on CTA should proceed with timely catheter angiographic embolization if extravasation is confirmed on catheter angiography. Depending on the clinical scenario and institutional preferences, either colonoscopy or CA can be performed for hemodynamically stable patients with active
extravasation on CTA. Due to the intermittent nature of diverticular bleeding, timing of angiography after a positive CTA is critical; in single center reports, performance of angiography within 90 minutes of a positive CTA was 9 times more likely to detect extravasation (26). Colonoscopy also may be an option in patients who have a positive CTA. In Japanese
retrospective cohort studies, the bleeding source was more frequently detected on colonoscopy when extravasation had been previously identified on CTA (27,28). There are limited data comparing outcomes of patients who undergo CTA and subsequent mesenteric embolization versus patients who undergo colonoscopy and are treated endoscopically. In a recent small retrospective cohort of patients undergoing colonoscopy (n = 27) or catheter angiography (n = 44) for LGIB, catheter angiography had a higher yield of detecting active bleeding, but similar rates of therapeutic intervention compared with colonoscopy (29).Suspected small bowel bleeding.—
Capsule endoscopy in suspected small bowel bleeding
Identifying the source of suspected small bowel (SB) bleeding can be quite elusive because of the length and tortuosity of the small bowel. Capsule endoscopy (CE) has had a significant
impact on diagnostic yield because it is able to examine most if not all of the small bowel mucosa (30). In addition, it is relatively noninvasive. Studies have shown that the diagnostic
yield of CE in suspected small bowel bleeding ranges from 38%–83% (31). The yield tends to be higher for overt bleeding as opposed to occult bleeding or iron deficiency anemia. Timing of CE is also important, and the highest yield occurs when performed within two weeks of bleeding (32,33). A negative study is also helpful and is associated with a low risk of rebleeding of 19% (34). There is also evidence to suggest that repeating CE after a nondiagnostic initial study is associated with an improved diagnostic yield (35,36). CE is considered the test of choice after upper endoscopy and colonoscopy is negative in patients presenting with gastrointestinal bleeding (3,37). Cross-sectional imaging is considered complementary to CE in the assessment of suspected SB bleeding. CTE had a pooled yield of 40% compared with 53% for CE (38). CEappears to be superior for diagnosing angioectasia while cross-sectional imaging is better for tumors, masses, and inflammatory wall changes (39–42).In addition to identifying the source of suspected SB bleeding, CE can help guide the initial direction of deep enteroscopy. If the lesion is identified in the first 60% of the SB based on transit time, then antegrade deep enteroscopy is recommended (43,44). Otherwise, the retrograde route is recommended. Capsule endoscopy may miss single mass lesions (45) and that is why
cross sectional imaging with CTE is considered complimentary (42,46). The most significant complication associated with CE is capsule retention and for this reason, risk factors, such as
known small bowel strictures, small bowel Crohn’s disease or obstructive symptoms should be excluded prior to capsule ingestion (47,48).Role of balloon assisted endoscopy in small bowel bleeding
Balloon assisted endoscopy (BAE) has revolutionized small bowel interrogations and endoscopic therapeutic options for small bowel bleeding. Both single and double balloon endoscopy (DBE) are now available, with DBE often utilized when a greater length of small bowel assessment is required. An antegrade (oral) or retrograde (rectal) approach is determined by the lesion location (antegrade: jejunum and proximal ileum; retrograde: mid and distal ileum). Given its invasive nature, BAE is often performed as a therapeutic modality once a suspected bleeding lesion or site is identified on CE or CT imaging. A large retrospective multicenter cohort exploring BAE noted a mean patient age of 66 years, 53% women, and 85% were antegrade approaches (49).
Multiple studies have now assessed the performance of BAE in cases of known or suspected small bowel bleeding. The overall diagnostic yield (DY) has been reported as approximately 70%, but up to 93% if performed after a positive finding on CE (50). The therapeutic yield (TY) of BAE might be as high at 67% in some populations (51). A recent systematic review and meta-analysis were performed involving twenty-two studies of overt small bowel bleeding (52). The pooled DY and TY of BAE was 74% and 34%, respectively. Modeling has suggested the ideal timing of BAE is within 2 days of overt small bowel bleeding (52).
Cross-sectional imaging in suspected small bowel bleeding
Cross-sectional imaging is complementary to CE and BAE in the evaluation of suspected small bowel bleeding. While CE is considered a first line diagnostic test in hemodynamically stable
patients with occult bleeding, CT enterography (CTE) should be performed when CE is negative or contraindicated, or a mass lesion is suspected. CTA should be considered if there is brisk overt bleeding with hemodynamic instability. Cross-sectional imaging also can screen for contraindications to CE, including strictures (41).Multiphase CTE, is best for older patients with occult bleeding and/or iron deficiency anemia where vascular etiologies are common (7). Single-phase CTE should be considered in younger patients, in an effort to reduce radiation exposure, or in individuals with suspected inflammatory conditions such as Crohn’s disease, associated obstructive symptoms which can be
seen with NSAID enteropathy, or prior radiation therapy. In patients with overt bleeding where CT scanning may be contraindicated, a radioisotope bleeding scan can be considered.Nonvariceal upper GI bleeding.—
Unless contraindicated, the evaluation of UGI bleeding begins with upper endoscopy (2). The ideal timing of endoscopy appears to be within 24 hours of presentation, with higher mortality seen when performed early (less than 6–12 hours) or late (greater than 24–36 hours) (53,54). A prokinetic medication, erythromycin if available, should be administered prior to endoscopy and is superior to gastric lavage for reducing the need for second look endoscopy and hospital length
of stay (2,55). Depending on the clinical situation and comorbidities, intubation for airway protection may need to be considered prior to endoscopy.There is limited role for CTA as EGD is typically able to localize the site of bleeding. If,however, endoscopic treatment fails to achieve hemostasis, conventional angiography is recommended. In cases where patients cannot be stabilized for EGD, CTA can be performed and if positive subsequent catheter angiography.
