Utility of gastrointestinal ultrasound in functional gastrointestinal disorders: A narrative review

Table 1 Current and potential uses of gastrointestinal ultrasound in functional gastrointestinal disorders

Current	Potential
Evaluating physiology
Stomach
Assess contribution of mechanisms to symptoms. Mechanisms include gastric emptying, gastric motility, gastroduodenal flow, gastric wall deformation, gastric accommodation and intragastric distribution of meals	Tailor management of patients based on contributing pathophysiology of symptoms to FGID (e.g. prokinetics for patients with FD and antral hypomotility)
Small bowel
Assess peristalsis to evaluate small bowel obstruction and its causes (e.g. mechanical vs ileus); support diagnosis for malabsorptive conditions (e.g. coeliac disease)	Study interactions of mechanisms to one another and temporal relationships between mechanisms and food/treatment/stress. e.g. evaluate mechanism behind food intolerances/malabsorption by evaluating physiological changes with food challenges in real time
Large bowel
Objectively assess constipation/faecal loading severity and location; assess colonic transit time	Objectively assess treatment outcomes (e.g. quantify improvement in constipation post treatment); scoring systems to quantify severity of faecal loading; objectively subtype IBS patients using luminal contents and diameters of large and small bowel; potentially measure colonic transit time, evaluate colonic contents and measure bowel diameters in a single test
Excluding organic diseases
Reliably exclude IBD from FGID in combination with other biomarkers; Useful screening investigation for abdominal pain, including acute cases as able to exclude appendicitis, diverticulitis, intestinal obstruction et al; UMAT can be used as an initial workup tool for patients with dyspepsia; Determine urgency of endoscopy based on GIUS findings; Determine type of investigations (upper vs lower GI tract, endoscopy vs cross sectional imaging) based on GIUS findings
Building rapport with patients
Allows more interaction time between physician and patients, opportunity to educate patients and opportunity to provide real-time reassurance

GI: Gastrointestinal; FGID: Functional gastrointestinal disorder; IBD: Inflammatory bowel disease; FD: Functional dyspepsia; GIUS: Gastrointestinal ultrasound.

Table 2 Advantages and disadvantages of gastrointestinal ultrasound

Advantages	Disadvantages
Widely available	Operator dependent
Relatively cheap	Not all areas of bowel equally visualised
Non-invasive	May be technically difficult in obese or previous surgery
Real-time	Expertise not widely available
Does not involve sedation, bowel prep or intravenous contrast agents
Can assess patient in physiological state
Able to assess multiple physiological mechanisms with a single test
Able to visualise upper and lower gastrointestinal tract as well as intra-luminal and extra-luminal organs
Builds rapport with patients as allows interaction between patient and physician
Allows managing clinician to perform test, allowing test to be focused in answering pertinent clinical questions