Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition

 [bib_ref] Usefulness of a rapid faecal calprotectin test to predict relapse in Crohn's..., Ferreiro-Iglesias [/bib_ref] [bib_ref] The utility of faecal calprotectin to predict post-operative recurrence in Crohns disease, Bachiller [/bib_ref] [bib_ref] NICE referral guidelines for suspected cancer: colorectal cancer and faecal occult blood..., Benton [/bib_ref] [bib_ref] Application of NICE guideline NG12 to the initial assessment of patients with..., Quyn [/bib_ref] 

## Common disoders

## Maldigestion of fructose-based carbohydrates and lactose, and polyhydric alcohols
Although the clinical utility of fructose / fructan hydrogen breath tests in this context is unproven, the expense and relative difficulty of adhering to a diet low in fermentable carbohydrates such as the 'low FODMAP diet makes desirable the ability to direct dietary management to those patients that are most likely to benefit. Recent studies have shown that the occurrence of symptoms after ingestion of a dietary challenge including 20g lactose (in IBS patients with lactase deficiency) or 25g lactulose (all IBS patients) identified a group of patients with visceral hypersensitivity; the sensitivity falls with lower doses. [bib_ref] Lactulose Challenge Determines Visceral Sensitivity and Severity of Symptoms in Patients With..., Neve [/bib_ref] Concurrent assessment of oro-caecal transit and fermentation has the potential to identify the causes of IBS symptoms in many patients. Studies are awaited that assess whether this approach identifies patients that will respond to a reduction in dietary FODMAPs or other specific interventions. [bib_ref] Dietary challenge tests: identifying food intolerance as a cause of symptoms in..., Deng [/bib_ref] 6.0 TESTS FOR MALABSORPTION

## Faecal elastase
A sensitive commercial ELISA utilising 2 monoclonal antibodies to human E1 is available.
Faecal elastase has also been compared with structural/imaging tests. measured FE in 213 patients undergoing ERCP finding that sensitivity for any ductal change was only 45% but this increased to 75% for more severe ductal abnormality. These results have been broadly confirmed by Keim et al. [bib_ref] Clinical value of a new fecal elastase test for detection of chronic..., Keim [/bib_ref] who found sensitivities of 69% and 78% for 2 FE assays with specificities of 76 and 77% for ductal changes seen at ERCP. An MRCP study of 81 patients with chronic pancreatitis showed 31/56 patients had MRI abnormalities despite normal FE emphasising the point that exocrine function is preserved long after structural change is present. [bib_ref] Magnetic resonance imaging and magnetic resonance cholangiopancreatography findings compared with fecal elastase..., Bilgin [/bib_ref] The wider availability of FE testing has led to its use in assessment of a number of conditions. Thus FE has been found to be reduced in coeliac disease, [bib_ref] Pancreatic insufficiency in adult celiac disease: do patients require long-term enzyme supplementation?, Evans [/bib_ref] , IBS, [bib_ref] Some patients with irritable bowel syndrome may have exocrine pancreatic insufficiency, Leeds [/bib_ref] senescence [bib_ref] Fecal pancreatic elastase-1 levels in older individuals without known gastrointestinal diseases or..., Herzig [/bib_ref] and in diabetes. [bib_ref] High prevalence of exocrine pancreatic insufficiency in diabetes mellitus. A multicenter study..., Hardt [/bib_ref] Whether this reflects a true deficiency in pancreatic function or confounding factors due to the dilutional effects of diarrhoea remain unclear. However, care is needed in interpreting low FE results as this does not necessarily indicate pancreatic dysfunction.
Nevertheless, given the ease of use and at least comparable performance compared with other non-invasive pancreatic function tests, Faecal elastase remains the most effective initial screening test for pancreatic insufficiency.
Bristol Stool Chart (courtesy of Dr K Heaton)