Society of Nuclear Medicine Procedure Guideline forGastrointestinal Bleeding and Meckel’s DiverticulumScintigraphyversion 1.0, approved February 7, 1999Authors: Patrick V. Ford, MD (St. Luke’s Episcopal Hospital, Houston, TX); Stephen P. Bartold, MD (Texas Tech Univer-sity, Odessa, TX); Darlene M. Fink-Bennett, MD (William Beaumont Hospital, Royal Oak, MI); Paul R. Jolles, MD (Med-ical College of Virginia, Richmond, VA); Robert J. Lull, MD (San Francisco General Hospital, San Francisco, CA); Alan H.Maurer, MD (Temple University Hospital, Philadelphia, PA); James E. Seabold, MD (University of Iowa Hospitals andClinics, Iowa City, IA).I. Purpose over intermittent sampling since most GI bleeds are intermittent and therefore frequently missed. The purpose of this guideline is to assist nuclear The clinical findings for active gastrointestinal medicine practitioners in recommending, perform- hemorrhage are often unreliable and misleading. ing, interpreting, and reporting the results of gas- There is frequently a marked temporal lag between trointestinal bleeding and Meckel’s diverticulum the onset of bleeding and the clinical findings. While scintigraphy. it may be clinically apparent that the patient has bled from the presence of melena or hematochezia, theII. Background Information and Definitions blood may pool in the colon for hours before being evacuated. A drop in the hematocrit and elevated Gastrointestinal bleeding scintigraphy is per- serum blood urea nitrogen (BUN) also lack the tem- formed in patients suspected of active gastroin- poral resolution needed to indicate active bleeding. testinal bleeding using Tc-99m labeled red blood Orthostatic hypotension and tachycardia occur cells (RBCs). Sites of active bleeding are identified more acutely but are insensitive and non-specific. by the accumulation and movement of labeled Red In cases where there is only occult bleeding detected Blood Cells within the bowel lumen. Since activity by guaiac positive stools, gastrointestinal bleeding within the lumen of the bowel can move antegrade scintigraphy is unlikely to be useful. Gastrointestinal and retrograde, frequent images (1 image every bleeding scintigraphy can detect bleeding rates as low 10–60 sec) will increase the accuracy of localizing the bleeding site. Tc-99m sulfur colloid (SC) is as 0.1 to 0.35 ml per min. The guaiac test detects bleeds rarely used today because of the short residence at rates well below the level necessary to be seen on time within the blood. Tc-99m SC is cleared from gastrointestinal bleeding scintigraphy. the blood by the reticuloendothelial system with a half-time as short as 2 to 3 min while radiolabeled Meckel’s Diverticulum Scintigraphy RBCs last for hours. A Meckel’s diverticulum is a vestigial remnant of Gastrointestinal bleeding (GI) is either upper, the omphalomesenteric duct located on the ileum originating above the ligament of Treitz, or lower, about 50 to 80 cm from the ileocecal valve. About distal to the ligament of Treitz. Frequent causes of half of Meckel’s diverticuli have gastric mucosa. upper GI bleeding include esophageal varices, gas- Bleeding may result from ileal mucosal ulceration tric and duodenal ulcers, gastritis, esophagitis, Mal- from acid secretion. Tc-99m pertechnetate avidly ac- lory-Weiss tear or neoplasm. Causes of lower GI cumulates in gastric mucosa and is the study of hemorrhage include angiodysplasia, diverticula, choice for identifying ectopic gastric mucosa in a neoplasms and inflammation, and, in children, Meckel’s diverticulum. Meckel’s diverticulum. Endoscopy and angiogra- phy provide accurate localization of bleeding sites III. Common Indications and potentially therapeutic control. Scintigraphy with labeled RBCs is complementary to endoscopy Gastrointestinal Bleeding Scintigraphy and angiography because it permits continuous The goals of gastrointestinal bleeding scintigraphy monitoring over hours. This is a major advantage are to locate the bleeding site and to determine who
46 • GI BLEEDING/MECKEL’ S DIVERTICULUM SCINTIGRAPHY requires aggressive treatment versus those who can b. Change in resting pulse rate from supine to be medically managed. It is usually in those patients erect position that require urgent care that the bleeding site is iden- c. Frequency and volume of bleeding tified. In some patients, the bleeding site is identified d. Current hemoglobin and hematocrit with sufficient confidence for specific surgical inter- e. Recent hemoglobins and hematocrits vention (e.g. right hemicolectomy in the case of a f. Number of recent transfusions bleeding site in the ascending colon). If bleeding is 4. Suspected location of bleeding detected, the site is usually localized well enough to a. Results of nasogastric aspirate and/or up- direct the next diagnostic test (e.g. endoscopy or ar- per gastrointestinal endoscopy teriography). Gastrointestinal scintigraphy should b. Results of sigmoidoscopy or colonoscopy be done as soon as possible after the patient presents C. Precautions for medical care, since active bleeding is more likely 1. Patients suspected of acute gastrointestinal at early times and is needed for correct localization. bleeding should have a blood pressure and pulse measured upon their arrival in the nu- clear medicine department to confirm that Meckel’s Diverticulum Scintigraphy they are not hypotensive. The vital signs The indication for a Meckel’s scintiscan is to localize should be monitored periodically while the ectopic gastric mucosa in a Meckel’s diverticulum as patient is being imaged. The patient should the source of unexplained gastrointestinal bleeding. have a large bore IV catheter in place so that Bleeding Meckel’s diverticula usually occur in hypotension can be rapidly treated with re- young children. The Meckel’s scintiscan should be placement fluids or blood. used when the patient is not actively bleeding. Even 2. The removal of blood for radiolabeling and in young children, active bleeding is best studied by reinjection poses the risk of misadministra- radiolabeled RBC scintigraphy. tion to the wrong patient. The handling and administration of blood products must be subject to special safeguards and procedures,IV. Procedures the goals of which are to eliminate any possi- Gastrointestinal Bleeding Scintigraphy bility of administration to the wrong patient A. Patient Preparation or contamination of workers. See “Special See Precautions (IV.C.) below Considerations for Labeled Blood Products” B. Information Pertinent to Performing the in the Society of Nuclear Medicine Procedure Procedure Guideline for Use of Radiopharmaceuticals. 1. History of past bleeding episodes D. Radiopharmaceuticals a. Number of transfusions in the past The in-vitro method for labeling red blood cells b. Results of prior studies to localize the is preferred due to its higher labeling efficiency. bleeding site The in-vivo/in-vitro method can be used. The in- c. Prior therapeutic interventions vivo method is not recommended. See the Society d. History of factors that affect RBC radiola- of Nuclear Medicine Procedure Guideline for Use of beling efficiency (e.g. thalassemia, chemo- Radiopharmaceuticals. therapy) E. Image Acquisition 2. Current blood pressure and pulse Continuous acquisition of images at a frame rate 3. Clinical signs of active bleeding of one image every 10–60 sec is important in or- a. Presence of orthostatic hypotension der to accurately localize the bleeding site. Radiation Dosimetry in Adults Radiopharmaceutical Administered Organ Receiving the Largest Effective Dose* Activity Radiation Dose* MBq mGy mSv (mCi) (rad) (rem) Tc-99m labeled RBCs 750 – 1100 i.v. 0.023 0.0085 heart (20 – 30) (0.085) (0.031) *per MBq (mCi) (ICRP 53 page 210 )
SOCIETY OF NUCLEAR MEDICINE PROCEDURE GUIDELINES MANUAL JUNE 2002 • 471. Equipment These images are optional. Typically de- Camera: Large field-of-view layed images are done from 2–6 hr and/or Collimator: A low energy, all-purpose, paral- at 18–24 hr after the injection of the radio- lel hole collimator is preferred. pharmaceutical. Delayed images are useful When the study must be per- in showing subsequent bleeding and cate- formed at the bedside, a di- gorizing the severity, but may result in in- verging collimator is useful to correct localization when identifying a see the maximum abdominal bleeding site. Initiating a new dynamic area. study may give useful localizing informa- Photopeak: Typically 20% window at 140 tion if the patient is actively bleeding at the keV. time of imaging. This may be done while Computer: 128 x 128 matrix, single or 2-byte initiating a new study by radiolabeling a mode. (One byte has been called new RBC kit. byte-mode and 2-bytes, word- d. Additional Views mode.) Due to overlying bladder activity, activity2. Patient position: Supine in the rectum can be difficult to appreci-3. Imaging field: Abdomen and pelvis ate. Lateral views may be needed to see4. Acquisition Protocol rectal bleeding. Anterior oblique and pos- a. Abdominal Flow Study terior views are frequently helpful in de- Anterior abdominal flow images (1–5 ciding if activity is located anteriorly ver- secs/frame x 1 min) are recommended. sus posteriorly. b. Dynamic Abdominal Imaging e. Region of interest counts over extravasated i. Dynamic anterior abdominal images blood in the bowel may be used to estimate are acquired at a frame rate of 10–60 blood loss when normalized to counts ob- sec per frame over a 60 to 90 min pe- tained from a blood sample drawn simul- riod. Acquiring these images in multi- taneously from the patient and corrected ple sets of 10–15 min each may facili- for attenuation. The precision and accuracy tate review of these images by the of such estimates should be determined by physician as the images are being each institution making such estimates. acquired. f. In cases where extravasated blood is seen ii. If computer acquisition is not possible: but does not move sufficiently to deter- Sequential static images 1 million mine the location or where the movement counts per image at least every 5 min is unusual, the following may be useful: re- for 60–90 min. Localization might be view of prior barium studies; oral Tc-99m aided by obtaining images at a shorter SC to outline the upper GI and small bowel interval, every 2–3 min. anatomy; or Tc-99m SC enema to outline c. Delayed Imaging the colon. For Tc-99m RBCs, if no bleeding site is F. Interventions identified on the initial 60–90 min dynamic Pharmacologic (pharmacologic intervention is images, delayed images may be acquired. controversial and is not widely used). Radiation Dosimetry in Children (5 year old)Radiopharmaceutical Administered Organ Receiving the Largest Effective Dose* Activity Radiation Dose* MBq mGy mSv (mCi) (rad) (rem)Tc-99m labeled RBCs 10 – 15 i.v. 0.062 0.025 heart (0.3 – 0.4) (0.23) (0.093)*per MBq (mCi)(ICRP 53 page 210 )
48 • GI BLEEDING/MECKEL’S DIVERTICULUM SCINTIGRAPHY Glucagon has been suggested as an adjunct to ated with early appearance of blood in the bowel GI bleeding studies. Glucagon decreases intesti- and intense activity equal to or greater than the nal peristalsis and increases vasodilatation. liver. Glucagon is not widely used. I. Reporting Heparin also has been suggested as an ad- Aside from patient demographics, the report junct to GI bleeding studies in selected patients should include the following information: with recurrent significant bleeding from a site 1. Indication for the study that has not been localized using standard diag- 2. Procedure nostic tests. Standard procedure is to administer a. Radiopharmaceutical IV 6,000 units heparin as a loading dose, fol- i. Dose lowed by 1,000 units IV heparin per hr. The pa- ii. Radiolabeling method for RBCs (e.g., tient’s baseline coagulation status should be in-vivo) evaluated before giving heparin. Heparin provo- iii. Method of administration (i.v.) cation is not widely used. Surgical coverage b. Acquisition should be immediately available as a precaution- i. Duration of acquisition (e.g., 1 hr) ary measure. Close monitoring of the patient ii. Frame rate (e.g., 10 sec/frame) is necessary and protamine sulfate should be iii. Projections acquired (e.g., anterior, lat- immediately available to reverse the effects of erals) heparin. c. Display (e.g., static vs. cine) G. Processing d. Findings Other than optional subtraction/contrast en- i. Onset hancement or blood loss estimation, there is no ii. Location routine processing. If the software is available, iii. Characteristics motion correction may be used to minimize the (a) Size and Shape (e.g., focal, diffuse) effects of patient movement. (b) Pattern of movement (e.g. moves Subtraction Cine vs. stationary, serpentine small The first frame or normalized summed set of bowel pattern vs. colonic, ante- data can be subtracted from the latter images to grade or retrograde) improve contrast. When using this technique, (c) Severity (e.g., waxing or waning the patient must remain still during the exam or intensity, qualitative intensity have appropriate motion correction software. compared to the liver, qualitative H. Interpretation Criteria volume—large/small) Accurate interpretation of GI bleeding scintigra- e. Study limitations, confounding factors phy requires knowledge of the normal and ab- f. Interpretation (e.g., positive, negative, in- normal variations in the abdominal vascular determinate) and state location of bleeding space. site Labeled red blood cells rapidly reach equilib- J. Quality Control rium within the vascular space of the liver, Quality control for the gamma camera, computer spleen and great vessels. It is normal for some ra- system and image display are as described by the dioactivity to be excreted in the urine and the Society of Nuclear Medicine Procedure Guideline for urinary tract to be seen even when in vitro label- General Imaging. ing is used. K. Sources of Error Extravasated radiolabeled RBCs within the 1. Delay in implementing the procedure since lumen of the bowel are identified as an area of bleeding may have stopped. activity that increases in intensity with time, 2. Failure to use a computer to display dynamic and/or as a focus of activity that moves in a pat- images as a movie. Subtle areas of bleeding tern corresponding to the lumen of the large or may go undetected or the location of the small bowel. Small bowel bleeding usually can bleeding may be inaccurately identified if im- be distinguished from large bowel bleeding by ages are not reviewed as a movie. Use of win- its rapid serpiginous movement. dowing levels and different color schemes on GI bleeding scintigraphy may be used to esti- a computer display also facilitates the detec- mate the severity of the bleeding. Factors associ- tion of subtle abnormalities. ated with a low bleeding rate are visualization of 3. It is important to continue to acquire images blood after one hour and activity less intense after abnormal activity is detected. Accurate than the liver. Higher bleeding rates are associ- localization of the bleeding site is dependent
SOCIETY OF NUCLEAR MEDICINE PROCEDURE GUIDELINES MANUAL J UNE 2002 • 49 upon identification of the focus of initial and 150 mg/dose for adults. Glucagon relaxes blood collection, and upon the movement of the smooth muscles of the gastrointestinal tract, the blood away from the bleeding focus. decreasing peristalsis. The dose for glucagon is 4. The entire abdomen must be examined be- 50 micrograms/kg i.v. 10 min after the Tc-99m fore concluding that no bleeding was de- pertechnetate. tected. A lateral, posterior and/or sub-pubic It is not recommended that an H2 blocker and view is best to help in identifying activity in pentagastrin be combined since H2 blockers an- the rectum that would otherwise not be de- tagonize pentagastrin. tected due to overlying bladder activity or Pharmacologic pre-treatment is not consid- soft tissue attenuation. ered necessary for performing a high-quality 5. Inexperienced readers may mistake mesen- Meckel’s scan. teric varices or penile blood pool for areas of Determine whether the patient has had recent bleeding. A full urinary bladder may ob- in-vivo RBC labeling where all circulating RBC scure sigmoid or rectal bleeding. Radioac- were treated with stannous ion via i.v. adminis- tive urine in the renal pelvis of a trans- tration of a “cold” pyrophosphate kit. If so, the planted kidney, in either the right or left Meckel’s scan may be compromised, since i.v. lower quadrant of the abdomen, may look Tc-99m pertechnetate will label RBC rather than like colonic activity. concentrate in ectopic gastric mucosa. This may 6. Gastric mucosal and renal activity is seen occur for days after the administration of stan- when free Tc-99m pertechnetate is present. nous pyrophosphate. This is not a problem with This potential source of error can be avoided in-vitro labeling. by using in vitro RBC labeling method and Patients may also be placed in a left lateral de- performing QC for free pertechnetate, and cubitus position to decrease small bowel activity by recognizing that intraluminal blood arising from the stomach. Nasogastric tube suc- moves in a distinct pattern. Images of the tion has also been used for this purpose. thyroid and salivary glands can confirm the B. Information Pertinent to Performing the presence of free Tc-99m pertechnetate as a Procedure source of artifact. 1. History of past bleeding episodes 2. Results of prior studies to localize the bleed- ing siteMeckel’s Diverticulum Scintigraphy 3. Has in-vivo RBC labeling been done?A. Patient Preparation 4. Clinical signs of active bleeding Pretreatment with pentagastrin, Histamine H2 C. Precautions blockers or glucagon is reported to enhance the None sensitivity of the Meckel’s scan. Pentagastrin is a D. Radiopharmaceuticals (see Tables) potent stimulator of gastric secretions and in- E. Image Acquisition creases gastric mucosa uptake of pertechnetate. 1. Equipment It also stimulates secretion of pertechnetate and Camera: Large field-of-view GI motility, potentially reducing ectopic site ac- Collimator: A low energy, all-purpose, paral- tivity. Pentagastrin is administered subcuta- lel hole collimator is preferred. neously, 6 micrograms/kg 15 to 20 min prior to Photopeak: Typically 20% window at 140 injecting the Tc-99m pertechnetate. Histamine keV. H2 blockers (cimetidine, ranitidine) block secre- Computer: 128 x 128 matrix, single or 2-byte tion from the cells and increase gastric mucosa mode. uptake. Oral cimetidine should be administered, 2. Patient position: Supine (optional: left lateral 300 mg QID x 2 days in adults, 20 mg/kg/day x decubitus) 2 days in children, or 10–20 mg/kg/day in 3. Imaging field: Abdomen and pelvis neonates prior to starting. Intravenous cimeti- 4. Acquisition Protocol dine should be administered at a rate of 300 mg a. Optional acquisition of anterior abdominal in 100 ml of D5W over 20 min with imaging start- flow images (1–5 sec/frame x 1 min). ing 1 hr later. Ranitidine may be substituted for b. Anterior abdominal images at a frame rate cimetidine. Ranitidine dosage is 1 mg/kg i.v. for of one image every 30–60 sec for at least 30 infants, children and adults, up to a maximum of min (some favor 60 min). 50 mg, infused over 20 min and imaging starting c. Additional static images, anterior oblique one hr later, or 2 mg/kg/dose p.o. for children projections, laterals and posterior projec-
50 • GI BLEEDING/MECKEL’S DIVERTICULUM SCINTIGRAPHY Radiation Dosimetry in Adults Radiopharmaceutical Administered Organ Receiving the Effective Dose* Activity Largest Radiation Dose* MBq mGy mSv (mCi) (rad) (rem) Tc-99m pertechnetate 300 – 450 i.v. 0.062 0.013 ULI# (8 – 12) (0.23) (0.048) *per MBq (mCi) # Upper Large Intestine (ICRP 53 page 199, no blocking agent) tion views are recommended at the end of though classically it is seen in the right lower the dynamic acquisition. Stopping the dy- quadrant. The activity that is most often con- namic acquisition to obtain these images fused for a Meckel’s diverticulum is activity in when abnormal activity is first seen can be the kidneys, ureter or bladder. Activity in the helpful to distinguish activity in a Meckel’s urinary tract usually first appears after activity is diverticulum from activity in the kidney, seen in the normal gastric mucosa. Small ureter or bladder. Post-void images can Meckel’s diverticulum may seem to appear at a also be helpful to detect activity in a later time than the stomach. Meckel’s diverticulum observed by the uri- Pertechnetate that is secreted by the gastric nary bladder. mucosa will gradually accumulate in the small F. Interventions bowel. This activity can be distinguished from a See Patient Preparation (IV.A) above. Meckel’s diverticulum by its delayed appearance A urinary catheter to drain the bladder of ac- and by its appearance as an area of mildly, ill-de- tivity can be helpful if the Meckel’s diverticulum fined increased activity. is adjacent to the bladder. Viewing the dynamic image as a cine on a Alternatively, decubitus or upright views can computer display that also permits adjustment sometimes cause the Meckel’s diverticulum to of image contrast is helpful. fall away from the bladder. I. Reporting G. Processing Aside from patient demographics, the report None should include the following information: H. Interpretation Criteria 1. Indication for the study Activity in the ectopic gastric mucosa should ap- 2. Procedure pear at the same time as the activity in the nor- a. Radiopharmaceutical mal gastric mucosa. A Meckel’s diverticulum i. Dose may appear anywhere within the abdomen, al- ii. Method of administration (i.v.) Radiation Dosimetry in Children (5 year old) Radiopharmaceutical Administered Organ Receiving the Largest Effective Dose* Activity Radiation Dose* MBq mGy mSv (mCi) (rad) (rem) Tc-99m pertechnetate 4.0 – 6.0 i.v. 0.21 0.040 ULI# (0.11 – 0.16) (0.78) (0.15) *per MBq (mCi) #Upper Large Intestine (ICRP 53 page 199, no blocking agent )
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52 • GI BLEEDING/MECKEL’S DIVERTICULUM SCINTIGRAPHY Technol 1998;26:87–90. Sager VV, Piccone JM. The effect of cimetidine on Murphy WD, Di Simone RN, Wolf BH, et al. The use blood clearance, gastric uptake and secretion of of heparin to facilitate bleeding in technetium- 99m-Tc-pertechnetate in dogs. R a d i o l o g y 1 9 8 1 ; 99m RBC imaging. J Nucl Med 1 9 8 8 ; 2 9 : 139:729–731. 725–726. Sfakianakis GN, Conway JJ. Detection of ectopic gastric Parekh JS, Treats CD. Emergency nuclear medicine. Ra - mucosa in Meckel’s diverticulum and in other aber- diol Clin of North Am 1992;30:455– 474. rations by scintigraphy: I. Pathophysiology and 10- Patrick ST, Gloniak JV, Turner FE, et al. Comparison of year clinical experience. J Nucl Med 1981;22:647–654. in-vitro RBC labeling with the UltraTag? RBC kit Sfakianakis GN, Conway JJ. Detection of ectopic gas- versus in-vivo labeling. J Nucl Med 1991;32:242–244. tric mucosa in Meckel’s diverticulum and in other Patton DD, McNeill GC, Edelman K. Cine scintigraphy aberrations by scintigraphy: II. Indications and for gastrointestinal bleeding. Radiology 1993;187:582. methods—a 10-year experience. J Nucl Med St. George JK, Pollak JS. Acute gastrointestinal hemor- 1981;22:732–738. rhage detected by selective scintigraphic angiogra- phy. J Nucl Med 32:1601–1604. VIII. Disclaimer Siddiqui AR, Schauwecker DS, Wellman HN, et al. Comparison of technetium-99m sulfur colloid and The Society of Nuclear Medicine has written and in-vitro labeled technetium-99m RBCs in the detec- approved guidelines to promote the cost-effective tion of gastrointestinal bleeding. Clin Nucl Med use of high quality nuclear medicine procedures. 1985;10:546–549. These generic recommendations cannot be applied Smith R, Copely DJ, Bolen FH. 99m Tc RBC scintigra- to all patients in all practice settings. The guidelines phy: correlation of gastrointestinal bleeding rates should not be deemed inclusive of all proper proce- with scintigraphic findings. Am J Roentgenology dures or exclusive of other procedures reasonably 1987;148:869–874. directed to obtaining the same results. The spec- trum of patients seen in a specialized practice set- ting may be quite different than the spectrum of pa- Meckel’s Diverticulum Studies tients seen in a more general practice setting. The Datz FL, Christian PE, Hutson W, et al. Physiological appropriateness of a procedure will depend in and Pharmacological Intervention in part on the prevalence of disease in the patient Radionuclide Imaging of the Tubular Gastro- population. In addition, the resources available to intestinal Tract. Sem Nucl Med 1 9 9 1 ; 2 1 ( 2 ) : care for patients may vary greatly from one med- 140–152. ical facility to another. For these reasons, guide- Khettery J et al. Effect of pentagastrin, histalog, lines cannot be rigidly applied. glucagon, secretin and perchlorate on the gastric Advances in medicine occur at a rapid rate. The handling of 99m-Tc-pertechnetate in mice. Radiol- date of a guideline should always be considered in ogy 1976;120:629–631. determining its current applicability.