Chronic diarrhoea investigation

• FBC, CRP, TFT, coeliac serology (refer to gastroenterology if positive for consideration of OGD and duodenal Bx)
• Consider drug related diarrhoea
• Stool for ova, cyst, and parasites
• Faecal calprotectin
• qFIT test
• If IBD or colorectal cancer suspected please refer to gastroenterology or colorectal surgery respectively

If the primary assessment is satisfactory and the patient is less than 40 years, please refer to gastroenterology dietician to address IBS-D symptoms.

Consider other surgical/structural/rare causes including:

• Faecal incontinence or impaction with overflow diarrhoea
• Hormone secreting tumour: fasting GUT hormones and 24 hour urine for 5-HIAA
• Fistulae suspected: MRI/CTE

• Malabsorption: Iron, B12, folic acid, Ca, albumin, coeliac, F elastase
• Immunodeficiency: HIV Igs
• Microscopic colitis: Colonoscopy + biopsy
• IBD: faecal Calprotectin and colonoscopy 

• Lactose intolerance: Hydrogen breath test
• Pancreatic exocrine dysfunction: Faecal Elastase, consider MRI Pancreas
• Bile acid diarrhoea: SeHCAT scan
• SIBO: Hydrogen breath test (or empirical trial of rifaximin 550mg twice a day for 14 days)
• If multifactorial malabsorption suspected refer for CTE, OGD and duodenal Bx