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Gastrointestinal Motility, Part 2: Small-Bowel and Colon Transit

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Gastrointestinal Motility, Part 2: Small-Bowel and Colon Transit CONTINUING EDUCATION Gastrointestinal Motility, Part 2: Small-Bowel and Colon Transit Alan H. Maurer Nuclear Medicine and Molecular Imaging, Temple University Hospital and School of Medicine, Philadelphia, Pennsylvania Learning Objectives: On successful completion of this activity, participants should be able to describe (1) the normal physiology and pathophysiology of small-bowel and colon transit; (2) methods for performing scintigraphic small-bowel and colon transit studies; and (3) pertinent image findings for interpreting scintigraphic small-bowel and colon transit studies. Financial Disclosure: The author of this article has indicated no relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, SAM, and other credit types, participants can access this activity through the SNMMI website (http://www.snmmilearningcenter.org) through September 2018. and indigestible solids. It is recommended that gastrointestinal Because of the difficulty often encountered in deciding whether transit studies be used to localize the potential site of disease a patient’s symptoms originate in the upper or lower gastrointesti- and guide therapy (2). A final diagnosis of a primary motility nal tract, gastrointestinal transit scintigraphy is a uniquely suited disorder by scintigraphy should not be made until an anatomic noninvasive, quantitative, and physiologic method of determining or structural cause (e.g., tumor, stricture, malrotation) for abnor- whether there is a motility disorder affecting the stomach, small mal transit has been excluded by imaging or endoscopy. bowel, or colon. Small-bowel and colon transit studies can be per- Nonscintigraphic methods of measuring bowel transit include formed alone or together with gastric emptying studies after oral hydrogen breath tests for small-bowel transit and radioopaque administration of an appropriately radiolabeled meal. It is hoped that newly published standards for performing these studies and the markers for colon transit. Wireless motility capsules measure pH, anticipated arrival of new Current Procedural Terminology codes pressure, and temperature throughout the gastrointestinal tract and in the United States for small-bowel and colon transit studies will are capable of measuring gastric emptying time, small-bowel increase their availability and use. transit time, and colon transit time. Indigestible solids such as Key Words: gastrointestinal scintigraphy; small-bowel transit radioopaque markers (4 mm) and the wireless motility capsule scintigraphy; colon transit scintigraphy; whole-gut transit scintigraphy (27 · 12 mm) do not move through the gastrointestinal tract in the same manner as a physiologic meal (3,4). The American Neuro- J Nucl Med 2015; 56:1395–1400 DOI: 10.2967/jnumed.113.134551 gastroenterology and Motility Society task force on gastrointesti- nal transit has stated that “the scintigraphic method is the only one that reliably allows the determination of both total and regional transit times” for gastrointestinal and colon transit (2). In a more recent report, this same organization together with the European D Society of Neurogastroenterology and Motility have stated that yspeptic symptoms related to dysmotility originating from scintigraphy is recommended for “detection of altered small- the small bowel or colon usually include abdominal pain, diarrhea, intestine transit in subjects with a suspected diffuse gastrointestinal or constipation. In many cases, however, symptoms overlap and it motility disorder” and that colon transit scintigraphy “offers re- is difficult to differentiate whether they originate in the upper or producible and accurate performance.” This report further states lower gastrointestinal tract or both. Studies of small-bowel motil- that scintigraphy “is indicated to measure whole gut and regional ity have shown a correlation between small-bowel contractions colon transit in patients with suspected colon motility disorders or and severity of symptoms in gastroparesis (1). Indications for more diffuse disorders involving the stomach or small intestine” (5). small-bowel and colon transit scintigraphy include but are not Although scintigraphic methods for measuring small-bowel and limited to dyspepsia, irritable bowel syndrome, chronic constipa- colon transit have been in use for at least 20 y, they have not tion, chronic diarrhea, chronic idiopathic intestinal pseudoobstruc- gained widespread clinical use, in large part because of their lack tion, scleroderma, celiac disease, and malabsorption. Small- and of standardization. The recently published joint guideline of the large-bowel motility is the result of complex gastrointestinal con- Society of Nuclear Medicine and Molecular Imaging (SNMMI) tractions that promote the aboral movement of intestinal chyme and the European Association of Nuclear Medicine (EANM) has been recognized as an important “step toward standardization” (6). Received May 19, 2015; revision accepted Jun. 15, 2015. As an additional impediment to wider clinical use in the United For correspondence or reprints contact: Alan H. Maurer, Nuclear Medicine States, there have been no Current Procedural Terminology (CPT) and Molecular Imaging, Temple University Hospital and School of Medicine, Broad and Ontario Streets, Philadelphia, PA 19140. codes available for reporting and reimbursement. New codes have E-mail: [email protected] recently been presented to and accepted by the American Medical Published online Jul. 9, 2015. COPYRIGHT © 2015 by the Society of Nuclear Medicine and Molecular Association CPT Panel. It is anticipated that these will soon be Imaging, Inc. available. SMALL-BOWEL AND COLON MOTILITY STUDIES • Maurer 1395 GENERAL METHODOLOGY transport food as it empties from the stomach and to mix it with bile and with pancreatic and intestinal secretions to facilitate absorption Like the esophageal transit and gastric emptying studies de- over the bowel mucosal surface. There is no simple small-bowel scribed in part 1 of this article, small-bowel and colon gastrointes- peristaltic pattern. Antegrade and retrograde movements of in- tinal transit studies most commonly use 99mTc and 111In as the testinal chyme occur in the jejunum and ileum, with some areas radioisotope. 67Ga complexes have also been used for colon transit progressing rapidly and others slowly. Jejunal peristaltic activity is studies, which extend over several days (7). typically more rapid and intense, with slowing of peristalsis seen in The reader is referred to the recently published SNMMI and the ileum (9). This process, although irregular, results in a net over- EANM Practice Guideline for Small-Bowel and Colon Transit for all progression of chyme toward the colon. Periodic more organized a more in-depth description of the technical details of performing peristaltic contractions occur, originating in the stomach and prop- these studies, including patient preparation, image acquisition, and agating throughout the small intestine. These specialized contrac- image processing (8). This review highlights the technical details tions, known as the migrating motor complex, serve a housekeeping of performing scintigraphic small-bowel and colon transit studies role by sweeping undigested material through the intestines. Al- and describes normal and abnormal physiology and important though more rapid peristalsis and transit occur in the duodenum imaging findings in interpreting these studies. and jejunum, the content of the small bowel slows particularly in Small-bowel and colon transit scintigraphy is typically performed the terminal ileum before passing the ileocecal valve and moving alone or, with minor modifications, as a continuation of a gastric into the colon. The result is a buildup of radiotracer activity in the emptying study. Three methods have been reported. The most terminal ileum, which functions as a reservoir for chyme before it common uses a mixed solid–liquid gastric emptying meal (7,8), with passes into the colon (Fig. 1) (10). the liquid phase being radiolabeled with 111In-diethylenetriamine- The ileocolonic junction between the terminal ileal reservoir and pentaacetic acid (DTPA). As the liquid mixes with intestinal chyme, the cecum regulates the flow of intestinal chyme from the small transit of the radiopharmaceutical is viewed to assess small-bowel bowel into the colon (Fig. 2A). Studies on animals and humans have and colon transit. If a solid-phase gastric emptying study is not confirmed that pulsatile filling of the cecum is associated with requested, a solid meal is administered but without radiolabeling propagating ileal contractions. The daily flow of chyme across the to maintain the standardized meal content. A second method uses ileocolonic junction is estimated at 1–2 L, with increased flow seen a specially prepared, delayed-release, methacrylate resin–coated postprandially (11). Early scintigraphic studies that demonstrated capsule containing 111In-labeled activated charcoal particles. The discrete bolus transfers of intestinal chyme across the ileocolonic coated capsule dissolves on reaching the alkaline terminal ileum, junction also showed that such
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