By MRCSA in MRCS Part A — 04 Jul 2026

44 FEEDING METHODS

# 45 FEEDING METHODS

Surgical patients are catabolic. Trauma, sepsis, major surgery and burns drive a stress response that breaks down lean muscle and depletes protein stores within days. Malnutrition delays wound healing, weakens the immune response, prolongs ileus and roughly doubles postoperative mortality in those affected. Choosing the right feeding route — and starting it early — is therefore one of the highest-yield decisions a surgical trainee makes. It is also one of the most heavily examined areas in MRCS Part A.

The exam tests recognition more than calculation. Examiners want you to look at a clinical vignette and instantly choose between oral, NG, NJ, PEG, jejunostomy or TPN, and to recognise the dangers of refeeding syndrome and TPN.

The cardinal rule: if the gut works, use it

> Pearl: If the gut works, use it. Oral first, then enteral tube, and only then parenteral.

Enteral feeding is physiological. It maintains gut mucosal integrity, prevents villous atrophy, preserves the intestinal microbiome and reduces bacterial translocation across the gut wall. Parenteral nutrition bypasses all of this — the gut is rested, mucosa atrophies, gut-associated lymphoid tissue involutes, and the risk of line sepsis and cholestasis rises sharply.

Compared with TPN, enteral feeding is cheaper, safer, more physiological and associated with fewer infectious complications. It is the default in any patient with a working gastrointestinal tract — even if absorption is partial, partial enteral feeding (supplemented with TPN if needed) preserves the gut.

Daily nutritional requirements

A simple framework you can apply to almost any vignette:

Substrate	Daily requirement (adult, per kg)
Energy	25–30 kcal/kg/day
Protein	1.0–1.5 g/kg/day (up to 2 g/kg in catabolic states)
Water	30 ml/kg/day
Sodium	1–2 mmol/kg/day
Potassium	1 mmol/kg/day

Catabolic patients (sepsis, burns, major trauma) need the upper end of protein. Energy requirements rise with fever (roughly 10% per degree Celsius above normal) and burns (up to 40 kcal/kg in severe cases). Overfeeding is harmful — it causes hyperglycaemia, hepatic steatosis and increased CO₂ production (a problem in ventilated patients).

Enteral feeding routes

The choice between routes is driven by three questions: (1) is the upper GI tract patent and safe? (2) is gastric emptying intact? (3) how long will feeding be needed?

Oral

Always first-line if safe swallow and adequate intake. Supplement with high-calorie sip feeds (e.g. Ensure, Fortisip) if intake is insufficient.

Nasogastric (NG) tube

➡ Short-term enteral access, typically <4–6 weeks.

➡ Tip sits in the stomach; requires intact gastric emptying and adequate airway protection.

➡ Position must be confirmed before each feed: aspirate pH <5.5, or chest X-ray if pH unreliable (proton pump inhibitors, no aspirate).

➡ Main complications: tube misplacement into the airway (Never Event if missed), aspiration pneumonia, displacement, sinusitis, nasal ulceration.

Nasojejunal (NJ) tube

➡ Tip placed post-pylorically, usually under endoscopic or fluoroscopic guidance.

➡ Indicated when gastric emptying is impaired or pancreatic stimulation must be minimised: gastroparesis, gastric outlet obstruction, severe acute pancreatitis, recurrent aspiration on NG feeds.

➡ Reduces — but does not eliminate — aspiration risk.

> Pearl: In severe acute pancreatitis, NJ feeding is preferred over TPN. Early enteral nutrition (within 48 hours) reduces infectious complications, organ failure and mortality. The old teaching of "rest the pancreas with TPN" is wrong.

Percutaneous endoscopic gastrostomy (PEG)

➡ Endoscopically placed tube directly into the stomach through the anterior abdominal wall.

➡ Indicated when enteral feeding will be needed for >4–6 weeks (some sources say >2–3 weeks).

➡ Classic candidates: stroke with persistent dysphagia, severe head injury, motor neurone disease, head and neck cancer.

➡ Contraindications: gastric outlet obstruction, ascites, coagulopathy, peritoneal carcinomatosis, inability to transilluminate the abdominal wall.

➡ Complications: peristomal infection (most common), tube blockage, peristomal leak, buried bumper syndrome, inadvertent visceral injury (colon, liver), peritonitis if early dislodgement.

Percutaneous endoscopic jejunostomy (PEJ) and surgical jejunostomy

➡ Used when the stomach must be bypassed: post-oesophagectomy, gastrectomy, severe gastroparesis, high gastric/duodenal leak.

➡ Surgical jejunostomy is the standard route for post-oesophagectomy feeding — placed at the time of surgery, distal to the anastomosis.

➡ Feeds must be advanced slowly (small bowel cannot tolerate bolus feeds — risk of distension, cramping, dumping-like symptoms).

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Parenteral nutrition (TPN)

TPN delivers a complete nutrient mix — glucose, amino acids, lipid emulsion, electrolytes, trace elements and vitamins — directly into the venous circulation.

Indications

TPN is indicated only when the gut cannot be used, or cannot meet requirements alone:

- Short bowel syndrome (<100 cm small bowel without colon, or <60 cm with colon in continuity)

- Prolonged paralytic ileus (>5–7 days)

- High-output enterocutaneous fistula (especially proximal, >500 ml/day)

- Severe Crohn's disease with non-functioning gut

- Bowel obstruction without surgical option

- Severe malabsorption despite enteral attempts

- Major mucositis post-chemotherapy

Access

TPN is hyperosmolar (>900 mOsm/L) and sclerosing. It must be given via a central line — typically a tunnelled central catheter (Hickman) or PICC for long-term use. Peripheral parenteral nutrition (PPN) exists but is low-osmolality, lower-calorie and only suitable for short-term supplementary feeding (<7–10 days).

Complications

The high-yield TPN complications fall into three groups:

Category	Specific complications
Line-related	CLABSI (central line-associated bloodstream infection), line thrombosis, pneumothorax on insertion, air embolism, line fracture
Metabolic	Hyperglycaemia, electrolyte derangement (↓K, ↓Mg, ↓PO₄), refeeding syndrome, hypertriglyceridaemia, micronutrient deficiency
Hepatic	Cholestasis, hepatic steatosis, gallstones (gallbladder stasis), eventual cirrhosis with long-term use

Monitoring

➡ Daily: U&E, glucose, fluid balance, weight.

➡ Twice weekly initially: magnesium, phosphate, LFTs.

➡ Weekly: full nutritional screen — Mg, PO₄, LFTs, trace elements (zinc, selenium, copper), triglycerides.

➡ Monthly: vitamin levels (B12, folate, fat-soluble vitamins).

Refeeding syndrome

A potentially fatal shift of fluid and electrolytes that occurs when nutrition is reintroduced to a starved patient.

Mechanism

During starvation, the body switches to fat and protein catabolism. Intracellular phosphate, potassium and magnesium are depleted, although serum levels may remain normal. When carbohydrate is reintroduced, insulin surges. Insulin drives glucose, K⁺, Mg²⁺ and phosphate intracellularly — and serum levels crash. Thiamine, a cofactor for carbohydrate metabolism, is rapidly consumed.

The triad

> Pearl: Refeeding syndrome = ↓ Phosphate, ↓ Potassium, ↓ Magnesium. Phosphate is the headline electrolyte.

The drop in phosphate (needed for ATP and 2,3-DPG) causes cardiac failure, respiratory muscle weakness, arrhythmias, seizures, rhabdomyolysis and haemolysis. Thiamine deficiency precipitates Wernicke's encephalopathy.

High-risk patients (NICE criteria)

One or more of:

- BMI <16

- Unintentional weight loss >15% in 3–6 months

- Little or no nutritional intake for >10 days

- Low K⁺, PO₄ or Mg²⁺ before feeding

Or two or more of:

- BMI <18.5

- Unintentional weight loss >10% in 3–6 months

- Little or no intake for >5 days

- History of alcohol misuse, chemotherapy, insulin, antacids or diuretics

Prevention

➡ Start at 10 kcal/kg/day (5 kcal/kg/day in extreme cases — e.g. BMI <14 or no intake >15 days).

➡ Advance slowly over 4–7 days.

➡ Give thiamine (and a vitamin B complex) before and during the first 10 days.

➡ Replace K⁺, PO₄ and Mg²⁺ proactively — do not wait for symptoms.

➡ Monitor electrolytes at least daily.

Special scenarios

Short bowel syndrome

➡ Defined as <200 cm functional small bowel.

➡ Minimum length for adequate enteral absorption: ~100 cm without colon, ~60 cm with colon in continuity.

➡ <60 cm → long-term (often home) TPN.

➡ Adaptation occurs over 1–2 years — the remaining bowel undergoes mucosal hyperplasia and slows transit.

➡ The terminal ileum is irreplaceable: it absorbs B12 and bile salts. Loss of >100 cm of terminal ileum causes B12 deficiency and bile-salt diarrhoea.

Oesophageal surgery and perforation

➡ Post-oesophagectomy: feeding jejunostomy placed at the time of surgery.

➡ Iatrogenic oesophageal perforation with a contained leak: TPN until the leak seals (typically 7–10 days), then reassess. NG and PEG are unsafe because the tube transits the injury.

Acute pancreatitis

➡ Mild: oral diet as tolerated within 24–72 hours.

➡ Severe: NJ feeding within 48 hours. TPN only if enteral fails.

Neurological dysphagia

➡ Stroke, head injury, motor neurone disease: NG for the first 2–3 weeks, then PEG if dysphagia persists or recovery is unlikely.

[Image: MCQs banner]

Test yourself

After redo oesophagectomy, which route of feeding is most appropriate in the immediate postoperative period?

((Feeding jejunostomy::☑️ Standard post-oesophagectomy route — delivers feed distal to the anastomosis.))
((Nasogastric feeding::Tube transits the new anastomosis; risks disruption and leak.))
((Total parenteral nutrition::Reserve for when the gut is unusable; enteral is preferred.))
((Oral feeding::Contraindicated until the anastomosis has healed and contrast study is clear.))

👩‍⚕️ Any operation that creates a fresh upper GI anastomosis = jejunostomy.

A patient underwent oesophagectomy for carcinoma. What is the best option for feeding?

((Feeding jejunostomy::☑️ Bypasses the anastomosis and preserves enteral nutrition.))
((Nasogastric tube::Risk of anastomotic disruption.))
((Oral feeding::Too early; needs contrast swallow first.))
((TPN::Only if enteral route fails.))

A patient suffers an iatrogenic oesophageal perforation during endoscopy with a large, uncontained leak. What is the most suitable method of nutrition?

((Jejunostomy::☑️ Bypasses the injured oesophagus and maintains enteral feeding.))
((Oral feeding::Contraindicated with active oesophageal perforation.))
((Nasogastric feeding::Tube passes through the perforation site.))
((PEG tube::Still requires safe transit through the injured oesophagus to place.))

A 45-year-old man has an iatrogenic oesophageal perforation after dilatation of a benign stricture. Imaging shows a small contained leak with mild surgical emphysema. What is the most appropriate nutritional option?

((Nil by mouth + IV fluids::Supportive but does not meet caloric requirements.))
((IV fluids + sips orally::Risks enlarging the leak.))
((Total parenteral nutrition::☑️ Best option for a small contained leak — rests the oesophagus until it seals.))
((Nasogastric feeding::Passes through the perforation.))
((PEG tube feeding::Requires endoscopic access through the injured oesophagus.))

👩‍⚕️ Contained leak = TPN until sealed. Uncontained or surgical repair = jejunostomy.

A young man with midgut volvulus underwent resection and has 30 cm of small bowel left. What is the most suitable method of nutrition?

((TPN::☑️ Severe short bowel syndrome — below the 60 cm threshold for enteral absorption.))
((Oral feeding::Insufficient absorptive surface area.))
((Jejunostomy::Site of delivery doesn't fix the absorption deficit.))
((Nasogastric feeding::Same problem — nothing to absorb the feed.))

A patient has undergone long-segment small bowel resection and anastomosis. What is the most suitable method of nutrition?

((TPN::☑️ Adequate enteral absorption requires at least 60–100 cm of small bowel.))
((Oral feeding::Insufficient bowel length for absorption.))
((Nasogastric feeding::Same absorptive limitation as oral.))
((Jejunostomy::Delivery route, not an absorption solution.))

A patient underwent small bowel resection. Only 5 cm of jejunum remained, anastomosed to the colon. What is the most suitable method of nutrition?

((TPN::☑️ Extreme short bowel — lifelong parenteral nutrition required.))
((Oral supplements::No absorptive capacity.))
((Jejunostomy feeds::Same — nothing to absorb.))
((Elemental diet::Pre-digested, but still requires intact mucosa to absorb.))

A patient with multiple small bowel resections due to strictures. What is the best type of nutritional support?

((TPN::☑️ Cumulative resections leave inadequate bowel for enteral absorption.))
((Oral feeding::Inadequate absorption.))
((Nasogastric feeding::Same limitation.))
((PEG feeding::Does not address absorptive deficit.))

A patient had total colectomy with only 30 cm of small intestine remaining due to Crohn's disease. What is the most appropriate nutritional support?

((Long-term home TPN::☑️ Indicated for <60 cm of remaining small bowel.))
((Oral feeding with supplements::Cannot absorb adequately.))
((Jejunostomy::Insufficient bowel for enteral nutrition.))
((Elemental diet::Still requires absorptive surface.))

👩‍⚕️ Remember: short bowel <60 cm = home TPN; terminal ileum loss = B12 and bile-salt malabsorption.

A patient with long-standing Crohn's disease presents with abdominal pain, anorexia and albumin 29 g/L. What is the most appropriate feeding option?

((Central parenteral nutrition::☑️ Severe malnutrition with non-functioning gut — central line allows hyperosmolar feed.))
((Peripheral parenteral nutrition::Low osmolarity — only short-term supplementary use.))
((Nasogastric feeding::Active Crohn's may not tolerate enteral feed.))
((Oral supplements::Unlikely to be absorbed.))

A young man underwent a right hemicolectomy. What is the most suitable method of nutrition?

((Oral::☑️ Small bowel and most colon intact — early oral feeding promotes recovery (ERAS).))
((TPN::Unnecessary; gut is functional.))
((Nasogastric feeding::Oral is preferred when tolerated.))
((Jejunostomy::Overly invasive.))

After a distal ileocolic resection, the patient has 250 cm of ileum. What is the most suitable method of nutrition?

((Oral::☑️ Well above the 100 cm threshold for enteral absorption.))
((TPN::Not indicated with adequate remaining bowel.))
((Jejunostomy::Unnecessary.))
((Nasogastric feeding::Oral is preferred.))

What is the most suitable method of nutrition for a patient who suffered a severe head injury and needs long-term feeding support?

((PEG::☑️ Long-term enteral access for unsafe swallow and impaired airway protection.))
((Nasogastric tube::Short-term only (<4–6 weeks); risk of displacement.))
((TPN::Enteral is preferred when the gut works.))
((Oral feeding::Unsafe with impaired consciousness.))

A patient is 14 days post-stroke with persistent dysphagia and needs long-term feed support. What is the next step?

((PEG::☑️ Dysphagia unlikely to resolve quickly — switch from NG to PEG at 2–4 weeks.))
((Nasogastric tube::Already in place; long-term use causes discomfort, displacement, sinusitis.))
((Oral feeding::Aspiration risk while dysphagia persists.))
((TPN::Gut is functional; enteral preferred.))

A 38-year-old woman with severe acute pancreatitis is admitted to ITU. She has been NBM for 5 days. What is the most appropriate route of nutrition?

((Nasojejunal feeding::☑️ Early post-pyloric enteral feeding reduces infection, organ failure and mortality.))
((TPN::Outdated practice — enteral feeding is now first-line even in severe pancreatitis.))
((Nasogastric feeding::Acceptable in some protocols but NJ is preferred to minimise pancreatic stimulation.))
((Oral diet::Not yet tolerated in severe disease.))

A 60-year-old man with BMI 15 and minimal intake for 12 days is admitted for elective surgery. He is started on enteral feed and 48 hours later develops confusion, weakness and serum phosphate 0.3 mmol/L. What is the diagnosis?

((Refeeding syndrome::☑️ Classic triad — hypophosphataemia, hypokalaemia, hypomagnesaemia after carb load.))
((Sepsis::Possible but the metabolic profile is diagnostic.))
((Wernicke's encephalopathy::Part of the spectrum but the electrolyte derangement defines refeeding.))
((Hypoglycaemia::Glucose is usually high, not low, due to TPN/feed.))

👩‍⚕️ Start high-risk patients at 10 kcal/kg/day, give thiamine first, and replace electrolytes proactively.

Which of the following is NOT a recognised complication of TPN?

((Central line sepsis (CLABSI)::Most important complication of TPN.))
((Hepatic steatosis and cholestasis::Common with prolonged use.))
((Hyperglycaemia::Common — TPN delivers concentrated glucose.))
((Villous hyperplasia::☑️ Opposite occurs — gut rest causes villous atrophy.))
((Refeeding syndrome::Can occur on starting TPN in malnourished patients.))

Revision summary

- If the gut works, use it. Oral > enteral tube > TPN.

- Daily needs: 25–30 kcal/kg, 1–1.5 g protein/kg, 30 ml/kg water.

- NG: short-term (<4–6 weeks). Confirm position before each feed.

- NJ: post-pyloric — gastroparesis, severe pancreatitis, recurrent aspiration.

- PEG: long-term (>4–6 weeks) — stroke dysphagia, head injury, MND, head and neck cancer.

- Surgical jejunostomy: post-oesophagectomy or gastrectomy.

- TPN: central line; only when gut unusable — short bowel, prolonged ileus, high enterocutaneous fistula, contained oesophageal perforation.

- Short bowel syndrome: <100 cm without colon or <60 cm with colon = lifelong TPN. Terminal ileum loss = B12 + bile-salt malabsorption.

- TPN complications: CLABSI, line thrombosis, hyperglycaemia, cholestasis, hepatic steatosis, refeeding.

- Refeeding syndrome: ↓PO₄ + ↓K⁺ + ↓Mg²⁺. Give thiamine first, start at 10 kcal/kg/day, monitor daily.

- Severe pancreatitis: NJ feeding within 48 hours — not TPN.

- Oesophageal perforation: contained leak = TPN; uncontained or post-repair = jejunostomy.