Upper Gastrointestinal Tract Recent Advances in Gastric Function Testing Allen Lee, MD1 and Braden Kuo, MD, MSc2 1. Clinical Fellow, Department of Gastroenterology, Tufts Medical Center; 2. Assistant in Medicine, Massachusetts General Hospital, Harvard Medical School
Abstract
Gastric motor and sensory abnormalities can cause common upper gastrointestinal (GI) symptoms, such as nausea, emesis, bloating, early satiety, and dyspepsia. Current standard tests for evaluating gastric function include gastric emptying scintigraphy, antroduodenal manometry, electrogastrography, and gastric barostat. These tests measure gastric emptying, contractile activity, myoelectric activity, as well as accommodation of the stomach. However, because of issues of invasiveness, poor tolerability, exposure to radiation, and limited availability for many clinicians, novel techniques have been developed to measure gastric function. These tests include stable isotope breath tests, SmartPill wireless monitoring capsule, transabdominal ultrasonography, magnetic resonance imaging (MRI), and single photon emission computed tomography (SPECT). These novel modalities are less invasive while providing valuable information regarding physiology as well as pathophysiology, which allows for correlation of upper GI symptoms with gastric dysmotility. Some can provide measurements of multiple parameters of motility simultaneously in multiple parts of the GI tract. Thus, these tests improve upon current standards and may increase our understanding of clinical issues with more widespread adoption.
Keywords Breath testing, capsule, motility, magnetic resonance imaging (MRI)
Disclosure: Braden Kuo, MD, MSc, has performed consulting for SmartPill and Evoke. Allen Lee, MD, does not have any conflicts of interest to declare. Received: May 26, 2010 Accepted: September 29, 2010 Citation: US Gastroenterology & Hepatology Review, 2010;6:17–21 Correspondence: Braden Kuo, MD, MSc, GI Unit, GRJ 719, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114-2696. E:
bkuo@partners.org
Testing of gastric motor and sensory function provides information regarding normal physiology and also reveals motor abnormalities that correlate with common upper gastrointestinal (GI) complaints. Typical symptoms include nausea, emesis, bloating, early satiety, and dyspepsia. Diseases of the upper GI tract include gastroparesis, functional dyspepsia, small bowel dysmotility, and cyclic vomiting syndrome among others. Neuromuscular testing of the upper GI tract allows for correlation of underlying dysmotility with symptoms, which can then be used to guide therapy.
Normal Physiology
Gastric emptying then occurs, which is dependent upon contractile forces generated in the proximal stomach and opposed by resistance developed in the antrum, pylorus, and duodenum. Emptying of liquids is accomplished quickly. It depends on the volume of liquid ingested and is opposed by duodenal feedback mechanisms.2,3
Solid © TOUCH BRIEFINGS 2010
The primary motor functions of the stomach include accommodation and storage of an ingested meal, trituration of the food bolus into smaller particles, and then delivering the gastric contents to the duodenum in a coordinated fashion. In response to a meal, normal gastric response involves accommodation, which is a vagally mediated reflex resulting in reduced gastric tone and inhibition of contractions mainly in the proximal stomach. This allows for a two- to threefold increase in gastric volume without a concomitant rise in gastric pressure.1
meals are initially retained in the stomach until food particles have been triturated to <1mm in size and this is influenced by meal volume, caloric content and density.4
Stomach emptying is then completed with onset
of the migrating motor complex (MMC), which removes indigestible objects. Emptying is a highly coordinated activity between the fundus, antrum, pylorus, and duodenum and is regulated by the interstitial cells of Cajal (ICC) as well as neuro-enteric pathways.5,6
Pathophysiology
Impaired accommodation can be seen in a majority of patients with functional dyspepsia and is associated with symptoms of bloating, distention, nausea, and early satiety.1
Delayed gastric emptying is an
essential component of gastroparesis and can also be seen in a significant subset of patients with functional dyspepsia.7
Rapid gastric
emptying can be seen with dumping syndrome and functional dyspepsia, and may also play a role in cyclic vomiting syndrome.8,9 Delayed emptying in the proximal stomach has been associated with symptoms of early satiety, nausea, abdominal distention, and acid reflux, whereas delayed emptying in the distal stomach is associated with emesis.10
Symptoms of upper GI dysmotility can occur when there are disturbances in rates of gastric emptying, impaired accommodation, amplified gastric sensation, changes in neuromuscular function and contractility, and lack of coordination of these pathways.11,12
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