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Investigation of gastrointestinal function 

Investigation of gastrointestinal function
Chapter:
Investigation of gastrointestinal function
Author(s):

Jervoise Andreyev

DOI:
10.1093/med/9780198746690.003.0289
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date: 05 March 2021

There are two main reasons for investigating the gastrointestinal (GI) tract: first, to identify diseases at an early stage (e.g. endoscopic screening for neoplasia); second, to diagnose and manage symptoms. A pathological process can potentially affect any part of the GI tract, but apart from mass lesions, pathological change per se hardly ever causes symptoms directly. Symptoms depend on whether critical physiological change has been triggered by the pathological insult. Individual symptoms or clusters of symptoms are not a reliable indicator of the underlying cause, and different physiological changes can produce identical symptoms. Critical symptoms indicative of significant GI tract pathology include ‘red flag’ symptoms (e.g. a palpable mass, rectal bleeding, weight loss) and other symptoms that are frequently missed by patients and clinicians alike (e.g. steatorrhoea, nocturnal waking to defecate). Dietary intake requires systematic assessment. Routine investigation should usually include thyroid function testing, vitamin B12 and vitamin D status, coeliac screen, iron studies, and inflammatory markers. Endoscopy and cross-sectional radiology provide excellent anatomical visualization but provide little information about the dynamic function and physiology of the GI tract, for which various tests for specific physiological functions can be used. Failure to investigate adequately misses easily treated diagnoses and means ongoing symptoms for patients. For many patients with multiple comorbidities, there is often more than one cause for their GI symptoms, which will not improve unless all causes are identified and treated.

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