Upper Gastrointestinal Tract
Figure 4: Tracing of SmartPill from Stomach to Colon in a Healthy Individual
ICJ
which may be preferable in pregnancy or in young children. The main disadvantage of SP is that it measures emptying of a non-digestible object as opposed to solid meal emptying. Although the two are highly correlated, emptying of indigestible objects relies on return of the phase III MMC, which can be variable.27
Also, SP is a freely floating object and CE GET
only has a single, moving sensor, as opposed to antroduodenal manometry, which has multiple, fixed sensors to detect contractility parameters. Thus, SP can evaluate transit but cannot measure peristalsis. SP is also not widely available at this time. SP is another innovative modality for testing GI function that will likely become quite useful in the investigation of upper GI symptoms.
Green tracing indicates pH, blue tracing represents temperature, and red tracing corresponds to pressure measurements in mmHg. Gastric emptying is indicated by an abrupt rise in pH (>3 pH units) from the acidic gastric environment to the more alkaline duodenum (gastric emptying time (GET) occurs at 3h 4m 26s). Passage of the capsule from the ileum to the cecum is indicated by a drop in pH >1 unit for greater than five minutes at 5.5 hours after GET (ileocecal junction (ICJ) occurs at 7h 12s). The capsule expulsion from the rectum is indicated by a drop in temperature >20°F (capsule expulsion occurs at 28h 50m 16s).
Figure 5: Gastric Single Photon Emission Computer Tomogrphy
AB Ultrasonography
Transabdominal ultrasonagraphy can assess several parameters of gastric motor function including gastric emptying and gastric accommodation. Successive changes in cross-sectional area allow for calculation of antral wall motion, which in turn can provide a measure of gastric emptying.28 Three-dimensional ultrasonography has the potential for even more precise measurements of gastric emptying.29
used to measure volume and therefore accommodation in the distal30 proximal stomach.31,32
Ultrasound has also been and
Duplex sonography has enabled visualization of
contents in the antrum moving to the duodenum as well as measurement of transpyloric flow.33,34
Ultrasonography has been shown to have good
correlation with scintigraphy in determining gastric emptying (r = 0.7).35 When three-dimensional imaging techniques were utilized to measure gastric emptying of a liquid meal, scintigraphy and ultrasonography were highly correlated (r = 0.92).29
Furthermore, ultrasonography also showed C
100 200 300 400 500 600 700
0 0 10 20 30 40 50 60
Time (minutes) Barostat
SPECT total stomach SPECT fundus
D 500 NS (p=0.1) NS (p=0.05) 250 0 Barostat
SPECT fundus
SPECT total
stomach Meal volume (200ml)
Reconstructed three-dimensional single photon emission computed tomography (SPECT) images of a fasting (A) and postprandial (B) stomach in a healthy volunteer. C: Dynamics of meal-induced relaxation represented by fundic volumes plotted in time, as assessed by barostat and SPECT. D: Fundic accommodation induced by meal intake, as measured by barostat and SPECT. Meal-induced fundic accommodation measured by barostat and SPECT was not significantly different. Note that meal-induced fundic accommodation, as measured by SPECT scanning, approaches the volume of the ingested meal (200ml). Reproduced with permission from van den Elzen BD, et al., 2003.48
tract. This can help further understanding into delayed emptying and/or altered contraction in the stomach, small bowel, and colon and allow correlation with non-specific upper GI complaints. It is also performed upright and in an ambulatory fashion, which may be more physiologic than other modalities. Finally, it does not expose patients to radiation,
20
good inter-observer agreement in measurement of gastric emptying.36 Ultrasonography has several advantages over other modalities in the measurement of gastric emptying and accommodation. It is readily available, is fairly inexpensive, and does not carry risk of radiation exposure. Furthermore, it allows investigation into several physiologic processes that could potentially be leading to symptoms. Finally, ultrasound also allows for investigation of regional differences in gastric motility. However, monitoring gastric emptying by ultrasound for 90 minutes or longer may not be practical in clinical practice given time constraints. It may also show technical limitations in obese patients or in the presence of air. Measurement of gastric emptying requires a skilled observer and is operator dependent. Ultrasonography is reliable for measurement of liquid emptying rates but may be less accurate for solid emptying.37
Although ultrasound is versatile and readily available, concerns about time constraints likely restrict its clinical utility and may limit it to specialized centers.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) has been used to measure gastric emptying, contractility, as well as accommodation. Gastric emptying is measured by administering a liquid meal containing gadolinium tetra- azacyclododecane tetra-acetic acid as an MRI marker. T1-weighted images are obtained in the supine position at 15-minute intervals applying a spin-echo technique.39
scintigraphy in measuring solid gastric emptying.40
MRI showed excellent correlation (r = 0.988) with MRI was able to
correctly differentiate delayed and normal meal emptying in symptomatic patients and healthy volunteers.39
MRI can also measure gastric US GASTROENTEROLOGY & HEPATOLOGY REVIEW
Finally, ultrasound has a substantial day-to-day variability in gastric emptying rates in healthy volunteers but the clinical significance of this is unknown.38
Volume (ml)
Volume (ml)
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