Investigations	Potential results	Clinical management plan: abnormal results
Dietary/ lifestyle/ medications assessment	High dietary fat intake Low/high fibre intake High fizzy drink intake High use of sorbitol-containing chewing gum or sweets High caffeine intake High alcohol intake Anxiety Drug induced, eg, PPIs Laxatives β blockers Metformin	Dietary advice about healthy fibre and dietary fat intake. Referral to dietitian and ask patient to complete 7-day dietary diary beforehand. Lifestyle advice about smoking cessation. Consider referral for psychological support. Medications advice. Antidiarrhoeal ± bulk laxative.
Routine AND additional blood screen (pages 2–3)	Abnormal results Mg²⁺ low Coeliac disease	Follow treatment of abnormal blood results (pages 2–3). If IgA deficient, request IgG coeliac screen. Confirm with duodenal biopsy. Refer to dietitian for gluten free diet. Liaise with GP regarding long term monitoring of bone densitometry and referral to a coeliac clinic.
Stool sample: for microscopy, culture and Clostridium difficile toxin	Stool contains pathogen	Treat as recommended by the microbiologist and local protocols.
Stool sample: for faecal elastase	EPI	See EPI (page 16)
OGD with duodenal aspirate and biopsies and/or glucose hydrogen (methane) breath test	SIBO	Treatment for SIBO (page 17).
Carbohydrate challenge	Specific disaccharide intolerance	Appropriate treatment (pages 16–17).
SeHCAT scan	BAM	Treatment for BAM (page 16).
Abdominal X-ray	Faecal loading with overflow	Bulking agent.
1st Line
Flexible sigmoidoscopy with biopsies from non-irradiated bowel (avoid biopsies from areas obviously irradiated in sigmoid and rectum)	Radiation proctopathy and frequency of defecation	Pelvic floor and toileting exercises (page 18)—min. 6 weeks. Add stool bulking agent to pelvic floor exercise regimen. Antidiarrhoeal ± stool bulking agent.
	Radiation proctopathy/colopathy and pelvic floor dysfunction (page 17)	Antidiarrhoeal. ± stool bulking agent. ± pelvic floor and toileting exercises (page 18).
	Macroscopic colitis	Send stool culture. If mild or moderate, refer within 2 weeks to a gastroenterologist. If severe, *this is an emergency*—discuss immediately with a gastroenterologist.
	Microscopic colitis	Discuss with supervising clinician and refer to a gastroenterologist.
2nd Line
Colonoscopy with biopsies	Macroscopic or microscopic colitis	As above.
Colonoscopy with biopsies	Organic cause (eg, infection, inflammation, neoplastic)	Discuss with the appropriate clinical team within 24 h.
If diarrhoea is present in combination with other symptoms: flushing, abdominal pain, borborygmi, wheezing, tachycardia or fluctuation in BP
3rd Line
Gut hormones (Chromogranin A&B, gastrin, substance P, VIP, calcitonin, somatostatin, pancreatic polypeptide) and Urinary 5-HIAA and CT chest, abdomen and pelvis	Functioning NET, eg, carcinoid syndrome or pancreatic NET	Discuss and refer to the appropriate neuroendocrine tumour team requesting an appointment within 2 weeks.
	If all tests are negative, but symptoms persist	Reassure and suggest symptomatic treatment with antidiarrhoeal drugs. Trial of low-dose tricyclic antidepressants. Biofeedback.

Note: faecal calprotectin as a marker for bowel inflammation is too non-specific and hence not recommended in this population.
BAM, bile acid malabsorption; EPI, excocrine pancreatic insufficiency; GP, general practitioner; IgA, immunoglobulin A; IgG, immunoglobulin G; OGD, oesophago-gastroduodenoscopy; PPI, proton pump inhibitor; NET, neuroendocrine tumour; SIBO, small intestinal bacterial overgrowth.