Current status of functional gastrointestinal evaluation in clinical practice

Abstract

Neurogastroenterology and motility disorders of the gastrointestinal (GI) tract encompass a broad spectrum of diseases involving the GI tract and central nervous system. They have varied pathophysiology, clinical presentation and management, and make up a substantial proportion of outpatient clinic visits. Typically, patients experience persistent symptoms referable to the GI tract despite normal endoscopic and radiologic findings. An appropriate evaluation is thus important in the patient's care. Advances in technology and understanding of the disease pathophysiology have provided better insight into the physiological basis of disease and a more rational approach to patient management. While technological advances serve to explain patients' persistent symptoms, they should be balanced against the costs of diagnostic tests. This review highlights the GI investigative modalities employed to evaluate patients with persistent GI symptoms in the absence of a structural lesion, with particular emphasis on investigative modalities available locally and the clinical impact of such tools.

Fig. 1

(a) High-resolution manometry (HRM) from line plots to spatial temporal plots.(15) The x-axis represents time, y-axis represents the position along the catheter, and z-axis represents pressure recordings. (b) The concept of HRM. Closely spaced recording sensors on an oesophageal motility catheter generate multiple recordings throughout the oesophagus. Dashed arrows point to pressure recordings from individual sensors. Computer software fills in best fit data between the recording sensors spaced 1-cm apart, and colour codes amplitude levels. Finally, the image is smoothed out electronically and displayed as a topographic contour plot, with ‘D’ representing the peristaltic sequence when viewed from above. The contour plots are termed Clouse plots in honour of Ray Clouse, who developed HRM (reproduced with permission from Wiley © Gyawali CP. Neurogastroenterol Motil 2012; 24 (Suppl 1):2-4).

Fig. 2

Distinguishing conventional manometry from high-resolution manometry (HRM) with oesophageal pressure topography. (a) The catheter in this example has 30 pressure sensors spaced 1-cm apart along the length of the catheter. (b) The data output for HRM would be in the form of a line-tracing format providing a measure of contractile strength on a vertical axis. The red lines depict what the conventional manometry spacing would be if the sensors were spaced at 5-cm intervals. (c) Clouse plots: The line tracing format pressure data is converted into pressure topography by converting the pressure signal into a colour. Using an isobaric contour tool to isolate all the pressure above 30 mmHg, the anatomic landmarks can be identified: the upper oesophageal sphincter (UES); lower oesophageal sphincter (LES) and oesophago-gastric junction (EGJ) high-pressure zones. There are three distinct segments of contraction along the contractile wave – front separated by three distinct pressure troughs highlighted by P (proximal or transition zone), M (middle), and D (distal). The start of the swallow is highlighted by the dotted yellow line at the start of UES relaxation, and this is an important temporal landmark in oesophageal pressure topography (EPT) analysis. The contractile deceleration point (CDP) is a time point along the contractile wavefront and signifies a transition from the oesophageal body to LES function. The distal latency is calculated by measuring the time between the start of the UES relaxation and the CDP. Contractile front velocity (CFV) assesses propagation, and is similar to the standard peristaltic velocity, with the caveat that the measurement is confined to the oesophageal body domain between the proximal trough and the CDP. Contractile vigour is calculated differently using EPT: the distal contractile integral (DCI) quantifies the contractile activity within the space time box highlighted by the white dotted box. It calculates the pressure activity above 20 mmHg to exclude artifact and intrabolus pressure, and is presented using a unit of mmHg-cm-s (reproduced with permission from Wiley © Gyawali CP, et al. Neurogastroenterol Motil 2013; 25:99-133).

Fig. 3

Example of a HRM tracing illustrating normal peristalsis.

Fig. 4

Photograph shows a conventional 24-hour pH catheter system that measures only acid reflux.

Fig. 5

The wireless pH (Bravo™) capsule (Medtronic Inc, Minneapolis, MN, USA) measures 6 mm × 5.5 mm × 25 mm. The capsule attaches to the oesophageal wall and transmits pH data via radiofrequency signal to a small receiver attached to the patient’s belt.

Fig. 6

(a) Diagram illustrates the principles of intraluminal impedance-pH monitoring. In this technique, resistance to an alternating current is measured at multiple sites along the oesophagus. This is performed with a thin catheter mounted with ring electrodes. MII-pH detects the presence of a bolus by means of changes in the conduction between electrodes. Bolus contents that are liquid and mixed have a low impedance, and gas contents have a higher impedance. By using several pairs of electrodes, the detection of bolus movement is possible. The reflux can further be categorised by the pH electrode into acid (pH≤ 4) or non acid (pH > 4) (reproduced with permission from Elsevier © Savarino V. Dig Liver Dis 2004; 36:565-9). (b) Combined multichannel intraluminal impedance and pH (MII-pH) monitoring. Example of an acid reflux episode. Figure illustrates impedance measuring channels centred at 3, 5, 7, 9, 15 and 17 cm above the lower esophageal sphincter (LES). MII-pH identifies reflux episodes as rapid decline in intraluminal impedance progressing over time from distal to proximal (arrow). Information from the pH channel is used to distinguish between acid (nadir pH < 4) and non-acid (nadir pH > 4) reflux episodes. (c) Example of a non-acid reflux episode.

Fig. 7

(a) Antro-pyloro-duodenal jejunal manometry. Example of a normal migrating motor complex (MMC) pattern in the fasting state (night) of a normal subject. The upper 3 recordings are from the antrum-pylorus, the lower 3 recordings are from the duodenum-jejunum. (b) Example of a normal MMC pattern in the fasting state of a patient with enteric neuropathy. In the latter, abnormal neurogenic motor activity is seen with disruption of the normal MMC pattern with abnormal activity fronts, bursts of uncoordinated contractions, and sustained uncoordinated contractions.

Fig. 8

(a) High-resolution anorectal manometry of a normal bearing-down attempt shows an increase in rectal pressure and a decrease in pressure of the anal sphincter. (b) Anorectal manometry of a patient with obstructed defaecation (pelvic floor dyysnergia) shows paradoxical contraction of the anal sphincter during the bearing-down manoeuvre.