• Classified by pathophysiological type:
o Watery: osmotic (e.g. lactose intolerance), secretory (e.g. VIPoma)
o Fatty (steatorrhoea): malabsorption (e.g. coeliac disease, chronic pancreatitis)
o Inflammatory: blood/mucus, tenesmus (e.g. IBD, infections)
• History, stool analysis, and imaging help guide classification
• Fat malabsorption → pale, greasy, foul-smelling stools that float and are difficult to flush
• Causes:
o Coeliac disease
o Chronic pancreatitis (↓ lipase)
o Bile acid deficiency (e.g. terminal ileal disease or resection)
o SIBO
• Investigation: faecal fat estimation (qualitative or quantitative), faecal elastase (for pancreatic insufficiency)
• Iron → microcytic anaemia
o Absorbed in duodenum; deficiency common in coeliac disease, chronic GI blood loss
• Vitamin B12/folate → macrocytic anaemia
o B12 absorbed in terminal ileum (requires intrinsic factor)
o Folate absorbed in jejunum; rapidly depleted
• Zinc → periorificial rash, diarrhoea, alopecia, impaired wound healing
• Other important deficiencies:
o Vitamin D → osteomalacia, hypocalcaemia
o Vitamin A → night blindness, xerophthalmia
o Vitamin K → coagulopathy (prolonged PT)
• Occurs in severely malnourished patients given aggressive nutritional support
• Sudden ↑ insulin → intracellular shift of phosphate, K⁺, Mg²⁺
• Features: weakness, arrhythmias, seizures, oedema
• Prevention:
o Identify at-risk patients (e.g. BMI <16, prolonged starvation)
o Replace electrolytes before and during feeding
o Start nutrition slowly and monitor closely
• Indicated when enteral feeding is not possible (e.g. short bowel syndrome, bowel obstruction)
• Complications:
o Infection (line-related sepsis)
o Liver dysfunction (cholestasis, steatosis)
o Electrolyte disturbance
o Refeeding syndrome
o Micronutrient imbalances (e.g. trace elements, vitamins)
• Nasogastric (NG) tube:
o Short-term use (e.g. <4–6 weeks)
o Easy to place, less invasive
• Percutaneous endoscopic gastrostomy (PEG):
o Long-term feeding (>4–6 weeks)
o Indicated in neurological dysphagia, head & neck cancers
• Complications: aspiration, tube dislodgement, site infection
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Author & Educational Disclaimer
Author:
Dr Phillip Cockrell BM FRCP DipClinEd
Dr Phillip Cockrell is a UK Consultant Physician in Internal Medicine, currently working at Queen Alexandra Hospital, Portsmouth University Hospitals NHS Trust. He has previously worked as a registrar across Intensive Care Medicine, Gastroenterology, Cardiology, Stroke Medicine, Acute Medicine, and Respiratory Medicine.
He has held senior leadership roles including Associate Clinical Director of the Acute Medical Unit, Clinical Director of Internal Medicine, and Chief of Medicine. Dr Cockrell has over 15 years’ experience in postgraduate medical education, having lectured extensively across the MRCP syllabus and contributed to MRCP revision teaching and course development.
Dr Cockrell holds a Bachelor of Medicine (BM), Fellowship of the Royal College of Physicians (FRCP), and a Diploma in Clinical Education (DipClinEd). His teaching approach is based on structured consolidation of complex medical topics to support efficient and effective revision for postgraduate examinations.
Purpose of this content:
The material on this page is intended solely for educational purposes to support revision for the MRCP (UK) Part 1 examination. It reflects examination-relevant principles of internal medicine and is designed to aid learning and pattern recognition.
Medical disclaimer:
This content is designed for postgraduate medical examination revision and does not constitute medical advice, diagnosis, or treatment guidance and must not be used as a substitute for professional clinical judgement, local guidelines, or specialist consultation. Clinical decisions should always be made in the context of individual patient circumstances and current national guidance.
