Gastrointestinal Bleeding Scan

Article Author:
Ahsan Khan
Article Editor:
Pujyitha Mandiga
Updated:
6/14/2019 9:08:23 PM
PubMed Link:
Gastrointestinal Bleeding Scan

Introduction

Gastrointestinal bleeding scan (GIBS) is a non-invasive diagnostic radionuclide imaging study to evaluate patients with a suspected overt GI bleed, especially involving mid and lower gastrointestinal (GI) tract. It is performed with 99mTc-RBCs and helps determine the bleeding status (active or intermittent), gross localization, and estimation of the amount.[1]  Gastrointestinal bleeding (GIB) can be occult, overt, or obscure. Occult GIB has a positive guaiac test or iron deficiency anemia with no visible signs of bleeding. Overt GIB has signs of active bleeding such as melena, hematemesis, or hematochezia. Obscure GIB has persistent or recurrent bleed with no known source of bleeding after negative bidirectional endoscopy.

For purposes of geographical localization and potential intervention, GI bleeding typically classifies as upper, mid, and lower. Upper gastrointestinal bleed (UGIB) includes bleeding up to the level of the ampulla of Vater, which is within reach of esophagogastroscopy; this can identify major causes such as gastric and duodenal ulcers, esophageal varices, esophagitis, and gastritis. Mid GIB includes up to the level of the terminal ileum, which undergoes an evaluation with capsule endoscopy; this can diagnose etiologies such as Meckel diverticulum, angiodysplasia, and Crohn disease.[2] Most common causes of lower GIB within reach of colonoscopy are angiodysplasia, polyps, diverticulosis, inflammatory, and infectious colitis.  The clinical signs and symptoms of overt GI bleeding are often unreliable and can manifest late, especially if it is intermittent. Prompt and timely identification of GI bleed is essential for the next step in patient management, which includes CT angiography, Catheter angiography, surgical intervention, or observation.

Procedures

GI bleeding scan uses 99mTc-RBCs and 99mTc-sulfur colloids.[3][4] Sulfur colloid has a short half-life of 3 minutes and is taken up by spleen, liver, and bone marrow. The sensitivity of exam is decreased, especially for an intermittent bleed due to background activity in the reticuloendothelial system and short imaging time (20 to 30 minutes). Multiple studies have shown that 99mTc-RBCs is more superior due to long intravascular half-life, which allows longer imaging duration.[5][6][7]

There are three ways of erythrocyte labeling with technetium 99m with different labeling efficiency.[4]

In vivo method:

Involves injecting 1 mg of stannous pyrophosphate followed by intravenous injection of 555-1, 110 MBq of 99m Tc-pertechnetate. Labeling efficiency ranges from 75 to 80%. It is not recommended but can be helpful in those patients who do not want to receive blood products.

Modified in vivo method:

Similar to in vivo method with the exception that it entails mixing a vile of blood with 555-1, 110 MBq of 99m Tc-pertechnetate, wait for 10 minutes and then injecting into the patient. Labeling efficiency is around 85 to 90%.

In vitro method:

This method involves drawing blood from the patient and added to a vile containing stannous pyrophosphate. After 5 minutes, sodium hypochlorite is added and then mixed with citrate buffer. 555-1, 110 MBq of 99m Tc-pertechnetate is admitted to the mixture and incubated and injected into the patient; this is a method of choice with labeling efficiency greater than 97%. This method uses a commercially available kit. 

Recommended radionuclide dosage[8][9][1][10]:

Adults: 15-30 mCiChildren[1]: 2.16-21.2 mCi (per EANM pediatric dosage card)

Image acquisition:

After injecting the patient with radiolabeled erythrocytes, imaging is acquired using a gamma camera with a 128 x 128 matrix. Dynamic images are obtained usually at 10 to 20 seconds/frame. A dual-head gamma camera increases sensitivity for localization. The imaging duration is variable but usually lasts 1 to 4 over. Initial imaging of a minimum of 60 minutes is the recommendation if no bleeding is detected.[11][12][13][14] The exam terminates upon identification of bleeding. Sometimes, the exam can be continued up to approximately 24 hours.[1] Also, SPECT or SPECT-CT images can be obtained to further localize bleeding site, especially in cases of equivocal planar image findings.[15][16][17]

Indications

The most common indication of GIBS is for a GI bleed that especially involving mid and lower GI tracts. It can detect GIB at a rate as low as 0.1mL/ml.[18][19] GIBS should not be used for chronic occult bleeds. Other indications are;

  • To help identify the source of the obscure overt bleed
  • Risk identification in GI bleeding
  • Directing timely diagnostic angiography
  • Assisting in angiographic interventional or surgical planning

Potential Diagnosis

  • Active and intermittent small bowel bleeding
  • Active and intermittent colonic bleeding
  • Meckel diverticular bleeding
  • Obscured overt GI bleeding
  • Angiodysplasia
  • AV malformation
  • Intra-abdominal vascular tumors 

Normal and Critical Findings

Diagnostic criteria for a positive GI bleeding scan include all of the following:

  • Detection of radionuclide activity outside of the expected blood pool structures
  • Increasing intensity of the radionuclide activity on successive images
  • Movement of activity conforming to bowel loops

Typically, 99mTc-RBCs distribute within vascular structures. A small amount of activity can present in the bladder due to the presence of free 99m Tc-pertechnetate. Considerable bowel bleeding is identifiable with its linear pattern and peripheral location in the abdomen. Sigmoid bleed scan appears as S-shaped. Small bowel bleed can be differentiated with its rapid curvilinear pattern of activity and central location. Factors associated with low bleeding include; detection of activity after one hour, low target to background ratio (less intense than liver), and short bleeding duration. Factors indicating higher bleeding rates include early and intense activity with longer durations.[18]

Interfering Factors

Poor RBC labeling technique and drugs interfering with efficient RBC labeling increase free 99m Tc-pertechnetate in the blood pool, which in turn produces artifacts mimicking GI bleed.[20][21][22] Free 99m Tc-pertechnetate can be visible in the upper GI tract due to salivary gland and/or gastric secretion.[23] Neck images to detect thyroid and separate gland activity can help to determine the source of the artifact. The examiner can mistake physiologic activity within the urinary tract and bladder as GI activity. The penile activity can be mistaken for rectal bleed. Lateral images can help differentiation. Ovarian and uterine activity in the young woman can be mistaken for bleed. Uterine leiomyomas, splenosis, pancreatic pseudocyst, nonenteric bleeding/hematoma, and other intra-abdominal vascular tumors can show transient fixed uptake.[9]

Complications

Radionuclide GI bleeding scan is normally a safe procedure. The risk of the procedure is radiation exposure. Lactating patients who receive technetium labeled RBCs need a 12-hour interruption of breastfeeding.[8][1]

Patient Safety and Education

  • A physician or nurse should accompany hemodynamically unstable patients during the exam.
  • Strict adherence to ALARA (as low as reasonably achievable) principal is necessary regarding radiation dose.
  • Informed written consent should is necessary, along with the patient's medical and medication history.
  • General standard protocols and policies for the procedure, including a timeout, should be performed. Clinicians should follow guidelines for appropriate dosage and imaging techniques.
  • Weight and size limits of equipment should be observed while imaging large patients.
  • Dose reduction techniques should be utilized when appropriate and available.
  • Adverse reactions to radionuclide injection should be reported to the Society of nuclear medicine/USP drug problem-reporting program.
  • After the exam, instructions should be given to the patients for minimizing radiation exposure to family, children, and public when appropriate.
  • Interruption of breastfeeding for 12 hours for lactating patients.[8][1]

Clinical Significance

Early and timely diagnosis of gastrointestinal bleeding is essential for timely intervention, which can include image-guided minimally invasive endoscopic or surgical intervention. Gastrointestinal bleeding is a noninvasive study and is helpful in determining approximate location and severity of the bleeding with detection rates as low as 0.1 mL/m. GIBS has a sensitivity of 93% and specificity of 95%. It has the added benefit of continuous imaging for a longer duration to detect intermittent bleeds. The radiation exposure with GIBS is lower than a three-phase CT Angiography.[1] It does not require patient preparation, and acutely ill patients tolerate it reasonably well.


References

[1] Dam HQ,Brandon DC,Grantham VV,Hilson AJ,Howarth DM,Maurer AH,Stabin MG,Tulchinsky M,Ziessman HA,Zuckier LS, The SNMMI procedure standard/EANM practice guideline for gastrointestinal bleeding scintigraphy 2.0. Journal of nuclear medicine technology. 2014 Dec;     [PubMed PMID: 25472517]
[2] Ell C,May A, Mid-gastrointestinal bleeding: capsule endoscopy and push-and-pull enteroscopy give rise to a new medical term. Endoscopy. 2006 Jan;     [PubMed PMID: 16429358]
[3] Alavi A,Dann RW,Baum S,Biery DN, Scintigraphic detection of acute gastrointestinal bleeding. Radiology. 1977 Sep;     [PubMed PMID: 302010]
[4] Winzelberg GG,McKusick KA,Strauss HW,Waltman AC,Greenfield AJ, Evaluation of gastrointestinal bleeding by red blood cells labeled in vivo with technetium-99m. Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 1979 Oct;     [PubMed PMID: 317093]
[5] Siddiqui AR,Schauwecker DS,Wellman HN,Mock BH, Comparison of technetium-99m sulfur colloid and in vitro labeled technetium-99m RBCs in the detection of gastrointestinal bleeding. Clinical nuclear medicine. 1985 Aug;     [PubMed PMID: 3876189]
[6] Bunker SR,Lull RJ,Tanasescu DE,Redwine MD,Rigby J,Brown JM,Brachman MB,McAuley RJ,Ramanna L,Landry A, Scintigraphy of gastrointestinal hemorrhage: superiority of 99mTc red blood cells over 99mTc sulfur colloid. AJR. American journal of roentgenology. 1984 Sep;     [PubMed PMID: 6331732]
[7] Bunker SR,Brown JM,McAuley RJ,Lull RJ,Jackson JH,Hattner RS,Huberty JP, Detection of gastrointestinal bleeding sites. Use of in vitro technetium Tc 99m-labeled RBCs. JAMA. 1982 Feb 12;     [PubMed PMID: 6977041]
[8] ICRP, Radiation dose to patients from radiopharmaceuticals. Addendum 3 to ICRP Publication 53. ICRP Publication 106. Approved by the Commission in October 2007. Annals of the ICRP. 2008;     [PubMed PMID: 19154964]
[9] Grady E, Gastrointestinal Bleeding Scintigraphy in the Early 21st Century. Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2016 Feb;     [PubMed PMID: 26678616]
[10] Lassmann M,Treves ST, Pediatric Radiopharmaceutical Administration: harmonization of the 2007 EANM Paediatric Dosage Card (Version 1.5.2008) and the 2010 North American Consensus guideline. European journal of nuclear medicine and molecular imaging. 2014 Aug;     [PubMed PMID: 24893792]
[11] Bearn P,Persad R,Wilson N,Flanagan J,Williams T, 99mTechnetium-labelled red blood cell scintigraphy as an alternative to angiography in the investigation of gastrointestinal bleeding: clinical experience in a district general hospital. Annals of the Royal College of Surgeons of England. 1992 May;     [PubMed PMID: 1319696]
[12] Wang CS,Tzen KY,Huang MJ,Wang JY,Chen MF, Localization of obscure gastrointestinal bleeding by technetium 99m-labeled red blood cell scintigraphy. Journal of the Formosan Medical Association = Taiwan yi zhi. 1992 Jan;     [PubMed PMID: 1352337]
[13] Maurer AH,Rodman MS,Vitti RA,Revez G,Krevsky B, Gastrointestinal bleeding: improved localization with cine scintigraphy. Radiology. 1992 Oct;     [PubMed PMID: 1523306]
[14] Ryan P,Styles CB,Chmiel R, Identification of the site of severe colon bleeding by technetium-labeled red-cell scan. Diseases of the colon and rectum. 1992 Mar;     [PubMed PMID: 1310927]
[15] Schillaci O,Danieli R,Manni C,Simonetti G, Is SPECT/CT with a hybrid camera useful to improve scintigraphic imaging interpretation? Nuclear medicine communications. 2004 Jul;     [PubMed PMID: 15208498]
[16] Schillaci O,Spanu A,Tagliabue L,Filippi L,Danieli R,Palumbo B,Del Sole A,Madeddu G, SPECT/CT with a hybrid imaging system in the study of lower gastrointestinal bleeding with technetium-99m red blood cells. The quarterly journal of nuclear medicine and molecular imaging : official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of.... 2009 Jun;     [PubMed PMID: 18594484]
[17] Schillaci O,Filippi L,Danieli R,Simonetti G, Single-photon emission computed tomography/computed tomography in abdominal diseases. Seminars in nuclear medicine. 2007 Jan;     [PubMed PMID: 17161039]
[18] Smith R,Copely DJ,Bolen FH, 99mTc RBC scintigraphy: correlation of gastrointestinal bleeding rates with scintigraphic findings. AJR. American journal of roentgenology. 1987 May;     [PubMed PMID: 3495120]
[19] Thorne DA,Datz FL,Remley K,Christian PE, Bleeding rates necessary for detecting acute gastrointestinal bleeding with technetium-99m-labeled red blood cells in an experimental model. Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 1987 Apr;     [PubMed PMID: 3494826]
[20] Braga AC,Oliveira MB,Feliciano GD,Reiniger IW,Oliveira JF,Silva CR,Bernardo-Filho M, The effect of drugs on the labeling of blood elements with technetium-99m. Current pharmaceutical design. 2000 Jul;     [PubMed PMID: 10903389]
[21] Kawabe J,Higashiyama S,Torii K,Okamura T,Kotani J,Kawamura E,Ishizu H,Koyama K,Yamane T,Shiomi S, Poor labeling of Tc-99m red blood cells in vivo in a radionuclide intestinal bleeding study of a patient who had recently undergone frequent blood transfusions. Clinical nuclear medicine. 2003 Nov;     [PubMed PMID: 14578707]
[22] Sampson CB, Complications and difficulties in radiolabelling blood cells: a review. Nuclear medicine communications. 1996 Aug;     [PubMed PMID: 8878123]
[23] Stern SS,Leslie WD,Dupont JO,Peterdy AE,Billinghurst MW,Abrams DN, Hepatobiliary clearance of intravenous Tc-99m pertechnetate. Clinical nuclear medicine. 1995 Nov;     [PubMed PMID: 8565374]