Comparison of technetium-99m sulfur colloid and in vitro labeled technetium-99m RBCs in the detection of gastrointestinal bleeding

Imaging of Gastrointestinal Bleeding: An Update

Imaging of gastrointestinal bleeding crucial in the diagnosis of occult gastrointestinal bleeding. Gastrointestinal bleeding scintigraphy is a well-established study to aid localisation of gastrointestinal bleeding site. This article discusses about the use of gastrointestinal bleeding scintigraphy in its current practice with emphasis on radiopharmaceutical, imaging techniques, interpretation and pitfalls. There is also discussion on the use of Single Photon Emission Computed Tomography-Computed Tomography (SPECT-CT) within this method of scintigraphy. Meckel's diverticulum is known to be a frequent source of bleeding, mainly in children. It is also know that nuclear medicine imaging can help with Meckel's diverticulum identification. This article also discusses about the technique, imaging, interpretation and SPECT-CT usage for Meckel's diverticulum imaging.

The Accuracy of Computed Tomography Angiography Compared With Technetium-99m Labelled Red Blood Cell Scintigraphy for the Diagnosis and Localization of Acute Gastrointestinal Bleeding: A Systematic Review and Meta-Analysis

Imaging tests are commonly used as an initial or early investigation for patients presenting with suspected acute gastrointestinal bleeding (AGIB). However, controversy remains regarding which of two frequently used modalities, computed tomography angiography (CTA) or technetium-99m labelled red blood cell scintigraphy (RBCS), is most accurate. This systematic review and meta-analysis was performed to compare the accuracy of CTA and RBCS for the detection and localization of AGIB. Five electronic databases were searched with additional manual searching of reference lists of relevant publications identified during the search. Two reviewers independently performed screening, data extraction and methodological assessments. Where appropriate, the bivariate model was used for meta-analysis of sensitivities and specificities for the detection of bleeding and Freeman-Tukey double-arcsine transformation used for meta-analysis of proportions of correctly localized bleeding sites. Forty-four unique primary studies were included: twenty-two investigating CTA, seventeen investigating RBCS and five investigating both modalities. Meta-analysis produced similar pooled sensitivities; 0.83 (95% CI 0.74-0.90) and 0.84 (0.68-0.92) for CTA and RBCS respectively. Pooled specificity for CTA was higher than RBCS; 0.90 (0.72-0.97) and 0.84 (0.71-0.91) respectively. However, differences were not statistically significant. CTA was superior to RBCS in correctly localizing bleeding; pooled proportions of 1.00 (0.98-1.00) and 0.90 (0.83-0.96) respectively (statistically significant difference, P < 0.001). There is no evidence that CTA and RBCS have different diagnostic performance with respect to the detection of AGIB. However, CTA is superior to RBCS in terms of correctly localising the bleeding site, supporting usage of CTA over RBCS as the first line imaging investigation.

Successful Localization of the Source of Hemorrhage in Patient with Post-Whipple Surgery by 99mTc-Labelled Red Blood Cell Scintigraphy

Gastrointestinal Bleeding Scintigraphy (GIBS) of ^99mTc-labelled red blood cells is a relatively simple examination to perform, with high diagnostic accuracy and a relatively lower radiation dose. A positive scan can either suggest surgery without further investigation or can indicate angiography, a more targeted procedure. Whipple pancreatoduodenectomy is most often performed for tumors of the head of the pancreas. Pancreatoduodenectomy has 30%–40% morbidity and mortality, and while post-pancreatoduodenectomy hemorrhage is seen in less than 10% of patients, it accounts for 11%–38% mortality. The role of imaging in patients to detect relative hemodynamic stability is essential. Computed tomography angiography (CTA) shows the cause, site, and nature of bleeding, while digital subtraction angiography (DSA) has a diagnostic as well as a therapeutic role. We present a patient who presented with active gastrointestinal bleeding (GI) bleeding after undergoing a Whipple procedure, to highlight the role of GIBS in the successful localization of a bleeding site and the guidance of digital DSA in the embolization and control of the active bleeding.

Gastrointestinal Bleeding Scintigraphy in the Early 21st Century

Gastrointestinal bleeding scintigraphy performed with (99m)Tc-labeled autologous erythrocytes or historically with (99m)Tc-sulfur colloid has been a clinically useful tool since the 1970s. This article reviews the history of the techniques, the different methods of radiolabeling erythrocytes, the procedure, useful indications, diagnostic accuracy, the use of SPECT/CT and CT angiography to evaluate gastrointestinal bleeding, and Meckel diverticulum imaging. The causes of pediatric bleeding are discussed by age.

Acute gastrointestinal bleeding

Radionuclide bleeding scintigraphy remains a simple yet powerful method of localizing sites of gastrointestinal hemorrhage and is most commonly performed today using the red blood cell technique. Radionuclide techniques for detecting bleeding remain safe, sensitive, and noninvasive. Based on several simple concepts, including the use of cine-mode imaging over the abdomen, it is possible to achieve excellent accuracy in localizing the site of bleeding. Studies often contain additional ancillary information, which is helpful for diagnosis and patient treatment.

Selective role of nuclear medicine in evaluating the acute abdomen

The imaging evaluation of the acute abdomen has clearly evolved with the introduction of high-resolution imaging techniques, such as CT, US, and MR imaging, leaving scintigraphic examinations an important, though selective, role based on their noninvasive, physiologic, and functional nature. Proper use of these examinations among all the diagnostic methods requires a good understanding of their strengths and limitations.

Tc-99m sulfur colloid and Tc-99m tagged red blood cell methods are comparable for detecting lower gastrointestinal bleeding in clinical practice

PURPOSE

The objective of this study was to determine whether the Tc-99m red blood cells (Tc-99m RBC) method has a true advantage over the Tc-99m sulfur colloid (Tc-99m SC) technique in a busy clinical practice for detecting and localizing lower gastrointestinal bleeding sites.

METHODS

Three hundred fifty-nine consecutive gastrointestinal bleeding studies performed during the past 4 years were reviewed retrospectively. One hundred ninety-three scans were obtained with Tc-99m SC (scan duration, 30 minutes) and 138 studies were performed after the administration of Tc-99m RBC (scan duration, 1 hour). In addition, 28 examinations with Tc-99m SC were followed immediately by Tc-99m RBC scans for a duration of several hours. The results of the two methods were analyzed and the performance of the two techniques was compared.

RESULTS

Among 193 scans performed using the Tc-99m SC method, 47 (24.4%) successfully identified the location of the bleeding site, whereas in 138 scans performed using Tc-99m RBC, 38 (27.5%) were successful for this purpose. In the remaining 28 scans in which the Tc-99m SC scan was followed by the Tc-99m RBC study, only 4 (14.3%) positive bleeding sites were identified after a prolonged imaging period.

DISCUSSION

The theoretical advantages of the Tc-99m RBC technique compared with the Tc-99m SC method cannot be substantiated by this study. Our findings suggest that the efficacy of these two methods is nearly equal at a practical level.

CONCLUSION

The simpler and cost-effective Tc-99m SC method is as efficient as the Tc-99m RBC method when the scanning time is limited to 1 hour and optimal imaging and interpretation schemes are used.

Life-threatening hemorrhage of an unanticipated superficial circumflex iliac artery origin imaged with Tc-99m-labeled erythrocytes

The authors report, for the first time, the nuclear medicine diagnosis of extraperitoneal bleeding that originated from the superficial circumflex iliac artery and review the critical role of dynamic nuclear imaging techniques in the localization of sites of nonenteric hemorrhage. Dynamic imaging techniques using Tc-99m-labeled erythrocytes played a critical role in the localization of an extraperitoneal bleeding site near the entrance site of a Jackson-Pratt drain. Localization of the site remained undiagnosed before nuclear imaging despite two exploratory laparotomies and diagnostic angiography.

Imaging and radiological interventional techniques for gastrointestinal bleeding in children

Causes of pediatric gastrointestinal (GI) bleeding in children are numerous. The role of radiology in defining associated pathology, pinpointing the bleeding site, and intervening to control hemorrhage is discussed here. Barium studies, computed tomography (CT), and magnetic resonance imaging (MRI) each may play a role in identifying the underlying pathology associated with the bleeding. The exact source of bleeding may be localized by means of nuclear scintigraphy as well as selective angiography. In cases of life-threatening or persistent hemorrhage, once a bleeding source is identified, the interventional radiologist may offer percutaneous transcatheter therapy with selective intraarterial vasopressin infusion or embolotherapy.

BUN/creatinine ratios: aid to decision making about delayed imaging in Tc-99m red blood cell scans for gastrointestinal hemorrhage

In patients with gastrointestinal hemorrhage, delayed or late scans with Tc-99m labeled red blood cells are readily performed and have prognostic impact when early images are negative. Nevertheless, there have been no indicators for the likelihood of detecting bleeding on such images. In a review of all gastrointestinal bleeding scans over an 8-year period, 73 patients had delayed images (> 3 hours) following early negative exams. For these patients, determinations of serum blood urea nitrogen (BUN) and creatinine (Cr) were evaluated as the BUN/Cr ratio and were compared against delayed scan findings and confirmed diagnoses. Patients with significant renal failure were excluded from analysis. There were 34 late positive (46%) and 39 late negative (54%) studies. Mean BUN/Cr was 26.5 and 20.0 in patients with late positive and late negative scans, respectively (p < 0.05). Occurrence of late positive scans was 38% (19/50) for BUN/Cr < 25.0 vs. 65% (15/23) for BUN/Cr > 25.0 (p < 0.05). Patients with early negative images and a BUN/Cr ratio of 25 or greater have a greater likelihood of a positive delayed image. Late imaging should be encouraged in patients with elevated BUN/Cr and early negative scintigraphy.