Small Bowel Motility Testing: Manometry and Scintigraphy
Kimberly N. Harer, MD
William L. Hasler, MD
If a patient’s small bowel motility is in question after standard evaluation and imaging (plain films or barium studies), manometry and scintigraphy are the main tools to assess motor function in this gut region. Manometry does not provide information regarding transit time, but it does measure intraluminal pressure changes caused by occlusive contractions of the bowel wall, which are indirect measures of contractile activity. In contrast, scintigraphy allows for the noninvasive measurement of small bowel transit time, but contractile activity is not evaluated.
SMALL BOWEL MANOMETRY
This section will focus mainly on stationary techniques of small bowel manometry. Prolonging a stationary fasting manometry study to 6 hours provides the same accuracy as ambulatory 24-hour studies in more than 90% of patients and also provides manometric information about the antrum. If a lengthier recording or nocturnal study is needed, ambulatory systems are available.
1. To assess for causes of gastric or small bowel dysmotility such as neuropathy, myopathy, or obstruction not identified by endoscopy or radiographic imaging
2. To assess unexplained nausea, vomiting, bloating, abdominal distention, or other symptoms suggestive of upper gastrointestinal (GI) dysmotility
3. To distinguish generalized from localized gastrointestinal dysmotility in patients with dysmotility elsewhere (i.e., chronic constipation, gastroparesis, gastroesophageal reflux)
4. To evaluate small bowel motility in patients with slow transit constipation undergoing consideration of total colectomy
5. To diagnose suspected chronic intestinal pseudo-obstruction (CIP) when the diagnosis is unclear
6. To provide information to help select the optimal approach to feeding CIP patients (oral, gastric, jejunal, total parenteral nutrition [TPN])
7. To assess potential therapeutic response to a medical intervention or medication
8. To help exclude small bowel motor dysfunction with an entirely normal study
1. Those associated with esophagogastroduodenoscopy (EGD)
2. Massively dilated small bowel is a relative contraindication due to risk of perforation
3. Known multiple duodenal or jejunal diverticula
4. Small bowel strictures or mechanical obstruction
1. A 12-hour fast is required, with clear liquids for the evening meal on the day before testing. Some labs require up to 2 days of full liquid diet prior to testing.
2. Cessation of medications affecting motility for at least 48 to 72 hours prior to testing (including narcotics, macrolides, metoclopramide, anticholinergics, adrenergics). For diabetic patients, many centers will postpone study performance unless the blood glucose is <200 to 275 mg/dL at the start of testing due to effects of hyperglycemia to alter normal small bowel contractility.
3. If the patient is on TPN, discontinue the infusion 8 hours before the study.
4. If sedation for catheter placement is necessary, propofol or a short-acting benzodiazepine followed by a waiting period of at least an hour is recommended prior to proceeding with measurements in order to avoid possible drug-induced motility effects.
a. Stationary systems: multilumen water-perfused catheter with side-holes, where water perfusion through the side-holes serves as sensors (Fig. 54.1). The catheter is continuously perfused with water by means of an infusion pump at a low rate and is connected to external pressure transducers and recorders. Some water-perfused catheters include transmucosal potential difference (TMPD) electrodes or a Dent sleeve which can improve fidelity of pyloric pressure measurements by (1) increasing the
number of sensors across the pylorus and (2) helping to minimize catheter migration (see item number 6). Water-perfused catheters are widely available and relatively inexpensive; however, adequate dynamic performance of each catheter and transducer needs to be confirmed prior to each study.
b. Ambulatory systems: Teflon catheters with solid-state pressure transducers or impedance sensors combine solid-state miniaturized tube-mounted strain gauges with data loggers/recorders, similar to outpatient 24-hour pH monitoring.2 These catheters are portable and typically are more comfortable for patients.
c. High-resolution manometry (HRM) systems: high-resolution manometry catheters with up to 36 circumferential pressure sensors located 1 to 2 cm apart with data output available as both standard pressure tracings and color contour plots. The HRM system provides superior pressure profile detail than the aforementioned systems, and it is the modality of choice to evaluate pyloric activity. HRM recordings also offer better definition of antegrade and retrograde propagation of individual duodenojejunal contractions and can quantify contractile coupling.3
2. Stationary pneumohydraulic system connected to the water-perfused catheter
a. Degassed water in a reservoir is maintained at a high constant pressure (7.5 to 15 psi) by nitrogen oxide or carbon
dioxide and is then reduced to atmospheric level by capillary tubing (providing high resistance) by the time the water enters the manometric assembly. Optimal perfusion rates of 0.05 to 0.3 mL/min per channel can be achieved either with a pneumohydraulic perfusion system and incorporation of steel capillary or other tubes that control rate of flow, or by use of commercially available external transducers that have a set flow rate.
3. Data acquisition
a. A variety of computer-based systems are available with their own specifications. For example, for some computer software, the calibrations for peak pressure can be set to 50 to 100 mm Hg for small bowel contractions and 100 mm Hg for antral contractions.
4. Standard fluoroscopy equipment
5. Standard upper endoscope
6. Transmucosal potential difference (TMPD) electrodes or Dent sleeve
a. Aids the evaluation of motor activity in sphincteric regions, in this case the pylorus. This consists of two saline-perfused intraluminal catheter channels, connected to an electrometer, placed on either side of the pylorus. An electrode is placed subcutaneously (ideally) or on the skin, and transmucosal potential differences are obtained. The device facilitates correct placement of pressure sensors in the terminal portion of the antrum by maintaining the potential difference between gastric and duodenal mucosa. To date, Dent sleeves have not been used extensively to evaluate the pylorus.
1. Prepare the system for use. For the stationary system, connect each multilumen perfusion tube to strain gauges and flush with distilled water, set pressure in the tank drum of the pneumohydraulic system at 10 psi (nitrogen gas), connect tubing to the water tank, and label the tracing with patient information. The external strain gauges linked to the manometric assembly should be approximately at the same height above the floor as the sensors within the gut for accurate pressure determinations. This is easily achieved by having the patient lie on a bed that can be moved vertically up or down, with the head at a 45° angle.
2. Calibrate the equipment. For the stationary system, calibration of each strain gauge should precede every study. Before and during each study, the tracing needs to be monitored for uniformity of rate of rise of pressure peaks. A slow rate of rise
of waves mandates review of that sensor for potential blockage or air bubbles and flushing of the system with a bolus of degassed water. Ambulatory and HRM catheters should be calibrated based on the specified catheter protocol.
3. Place the catheter. The catheter can be placed either without or with endoscopy.
a. Nonendoscopic catheter placement
i. Pass the catheter with pressure sensors/transducers through the nose or mouth, guiding it with fluoroscopy beyond the pylorus into the duodenum and just past the ligament of Treitz. Steerable Teflon catheters are employed at some institutions. Radiation safety regulations at some centers recommend a maximum of 5 minutes of fluoroscopy time. If nonendoscopic placement does not achieve appropriate guidewire or catheter placement within 4 minutes of fluoroscopy time, upper GI endoscopy should be performed to secure proper guidewire placement. This leaves additional sufficient fluoroscopy time to ensure proper positioning of the catheter if needed.
b. Endoscopic catheter placement
i. A variety of methods are available for endoscopic placement of stationary or HRM catheters.
ii. One method involves passing a guidewire through the biopsy channel of the endoscope into the third portion of the duodenum. The endoscope is removed and the manometry catheter is advanced over the guidewire with positioning of the tip beyond the ligament of Treitz.
iii. Alternatively for catheters not designed to be passed over guidewires, sutures tied on the manometry catheter can be endoscopically carried into the duodenum using biopsy forceps. This method permits endoscopic visual confirmation of appropriate sensor positioning across the pylorus.
4. Position the sensors. The sensors should be spaced from the antrum across pylorus to the distal duodenum or proximal jejunum, starting 3 to 5 cm proximal to the pylorus (see Fig. 54.1). Prior to initiating recording, sensor positioning across the pylorus can be confirmed manometrically by identifying one of the three following patterns:
a. A combination of distal antral peaks (duration >5 seconds and higher amplitude, typically >20 mm Hg, with a maximum frequency of 3 per minute) and duodenal peaks (duration <3 seconds and lower amplitude, typically <20 mm Hg, with a maximum frequency of 12 per minute)
b. The presence of a high-pressure zone (tone)
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