In 2011, the American and European Neurogastroenterology and Motility Societies have released a position paper concerning the evaluation of gastrointestinal transit in clinical practice [5]. WMC testing was recommended for the following indications:

Similarly, the United States Food and Drug Administration (FDA) approved the SmartPill WMC GI Monitoring System for the evaluation of gastric emptying time in patients with suspected gastroparesis, for the evaluation of CTT in patients with suspected slow transit constipation, and for the measurement of temperature, pressure, and pH throughout the GI tract [6].

The preparations for the study include a 6 h fast, avoidance of alcohol and tobacco, and discontinuation of medications potentially altering GI motility and gastric pH (Table 34.1). The study begins with consumption of a standardized meal consisting of a low fat egg meal (120 g eggbeaters, two slices of bread, 30 g of strawberry jam and 120 ml of water) or a 250 ml Ensure meal (250 kcal, protein 9 g, carbohydrates 40 g, fat 6 g, fiber 0 g) (Abbott Laboratories, Abbott Park, Il, USA) or a 260-kcal nutrient bar (17% protein, 66% carbohydrates, 2% fats, and 3% fiber) that is available through the manufacturer along with 50 ml of water. On completion of the meal, the WMC is activated and swallowed immediately. It is essential not to deviate from the protocol meal and not to swallow the capsule prior to the meal, as changes in the gastric empting and colonic transit can occur [7]. An external data recorder is attached to the waist for the period of the exam. Fasting should be continued for 2 h following the ensure meal or 6 h fast following the low fat egg meal or the nutrient bar meal. During the test period, the patients record (using an event button positioned on the recorder) special activities as meals, sleep, and bowel movements. Abstention from the use of tobacco products for 8 h and the ingestion of alcohol for 72 h after the swallowing of the capsule as well as from strenuous exercise during the exam is required. The recorder is returned after 5 days and the data is downloaded and are analyzed using the display software (MotiliGI, Given Imaging Corp).

Data analysis and report are prepared by the display software. Typical result chart is presented in Fig. 34.2. Normative motility transit times are presented in Table 34.2. Gastric emptying time is defined as the duration of time from capsule ingestion to a pH rise of >3 pH units, representing the passage of the capsule from the acidic stomach to the alkaline duodenum. The sensitivity and specificity of WMC in identifying delayed gastric empting in comparison to a 4 h scintigraphic data were 0.87 and 0.92, respectively, with a correlation coefficient of 0.73 [8]. In another study, WMC was found to have 100% sensitivity and 50% specificity in diagnosing gastroparesis as compared to scintigraphic study of gastric emptying. In this study, the WMC detected motor abnormalities in 17 patients compared with 10 patients assessed by antroduodenal manometry [9]. Small bowel transit time (SBTT) is measured by using the capacity of the capsule to measure changes in pH profile [10, 11]. The SBTT is defined as the period that takes the capsule to move from entering the duodenum and until passing into the colon. In a study involving 66 healthy adults (18–65) and 34 adults with gastroparesis (18–66), the results of the SBTT measured by WMC were similar to the SBTT measured by scintigraphy in both the healthy and the gastroparetics [3]. Significant correlation of SBTT values obtained with WMC in comparison to whole gut scintigraphy (r = 0.69; p = 0.05) was demonstrated in another study [12]. The determination of SBTT was not possible in 5–10% of the patients due to the inability to accurately identify pH landmarks [13, 14]. Colon transit time (CTT) is defined as the time from the cecal entry and until the capsule leaves the body. A sustained (>10 min) pH drop of >1 unit that occurs more than 30 min after gastric emptying defines cecal entry, and loss of signal or a sudden temperature drop defines the capsule’s exit from the body. In a study performed on 78 constipated and 87 healthy subjects, CTT measured by WMC had good correlation to that measured by a ROM study (r = 0.78 at day 2 and r = 0.59 at day 5) and comparable specificity (0.95) and sensitivity (0.46) [14]. In another multicenter study performed on 158 constipated adults, CTT measured by WMC demonstrated an overall agreement of 87% with that of 5-day ROM [13].