GI Nutrition

• Audio chapter
  Single-voice audio, listen on the commute.
• ABIM-format MCQs
  5-option vignettes with full wrong-answer teaching.
• Study guide
  Tables, decision trees, primary sources.
• AI tutor
  Chapter-grounded, answers the question you're stuck on.

What this chapter covers

• Section 32.1: Refeeding syndrome

  Refeeding syndrome is the metabolic crisis that follows resumption of carbohydrate after a period of starvation, and preventing it is the most important decision in inpatient nutrition.

• Section 32.2: Hospital malnutrition and the albumin trap

  Inpatient nutrition decisions depend on distinguishing the catabolic state of acute illness from a true nutritional deficit that responds to caloric or protein support.

• Section 32.3: Enteral access and tube-feed complications

  Enteral nutrition requires safe, durable access that matches the planned feeding duration and the patient's anatomy.

• Section 32.4: Parenteral nutrition formulation and complications

  Parenteral nutrition (commonly abbreviated CPN for central parenteral nutrition or TPN when complete) delivers macronutrients (dextrose, amino acids, lipid emulsion), electrolytes, vitamins, and trace minerals through a central venous catheter when the gut is non-functional, inaccessible, or insufficient.

• Section 32.5: Short bowel syndrome and teduglutide

  Short bowel syndrome (SBS) follows extensive small-bowel resection (less than 200 cm of remaining small bowel) and is functionally classified by the anatomy of the residual gut, because the prognosis for enteral autonomy and the trajectory of complications differ sharply by phenotype.

• Section 32.6: Fat-soluble vitamins (A, D, E, K) and EFAs

  Fat-soluble vitamins (A, D, E, K) require bile salts and intact ileal bile-acid recirculation for absorption, so any state that disrupts the enterohepatic bile acid cycle (cholestyramine therapy, ileal disease or resection, severe cholestasis from PBC or PSC, alpha-1 antitrypsin liver disease, cystic fibrosis, prolonged parenteral nutrition without supplementation) creates fat-soluble vitamin deficiency.

• Section 32.7: Water-soluble vitamins

  Water-soluble vitamins are not stored in large quantities, so deficiencies emerge within weeks to months of inadequate intake or absorption.

• Section 32.8: Minerals and trace elements

  Mineral and trace element disorders produce characteristic clinical pictures.

Podcast episodes

1. 01

   GI Nutrition: Deciding to Feed and How

   The organizing idea is that feeding is a decision with risks on both sides: starved patients can be harmed by food, and inflamed patients can be mislabeled as starved. The episode begins with a starved man with alcohol use disorder, covering refeeding risk, thiamine before glucose, and a slow start. It then turns to a septic woman whose low albumin is not malnutrition, the GLIM criteria, and when support is indicated. Last, it follows a man with oropharyngeal cancer through choosing the gut, picking a nasal tube or PEG, introducer placement, a buried bumper, other PEG problems, and tube-feed diarrhea. A woman with advanced dementia shows who should not get a tube.

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2. 02

   GI Nutrition: Parenteral Nutrition and Short Gut

   The organizing idea is that parenteral nutrition is for a gut that cannot be used, and that a short gut is judged by the anatomy left, not the length lost. The episode starts with who qualifies for parenteral nutrition, then counts calories, avoids precipitation in the bag, chooses lipid and cycling, and handles line infection, gallstones, and liver disease. It then shows who is harmed by it. It turns to short bowel syndrome: anatomy and prognosis, ileal loss, oral rehydration, drugs, cholestyramine, teduglutide with colonoscopy, and the colon's two problems, oxalate stones and D-lactic acidosis.

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3. 03

   GI Nutrition: Vitamins and Essential Fats

   Each vitamin and essential fatty acid is traced from its job in the body to the picture its deficiency or excess makes. The episode starts with cholestasis and cholestyramine, which cause all four fat-soluble deficiencies, then covers vitamin D repletion, vitamin E, and vitamin K with warfarin and antibiotics. It turns to vitamin A excess mimicking cryptogenic cirrhosis, then essential fatty acid deficiency and why MCT oil cannot prevent it. The water-soluble section follows B12 absorption, confirmation of a borderline level, folate, and bacterial overgrowth, then pellagra, pyridoxine, thiamine, vitamin C, and biotin.

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4. 04

   GI Nutrition: Minerals and Trace Elements

   Each mineral and trace element has a specific biochemical job and a typical exposure or disease that tips it into deficiency or excess, so the exposure is asked about first. The episode starts with a man whose denture cream gives him zinc excess and copper deficiency that mimics B12 myeloneuropathy, then covers zinc deficiency and why zinc replacement is monitored. It moves to PPI-induced hypomagnesemia, manganese buildup in cholestasis on parenteral nutrition, and selenium and chromium deficiency from an unsupplemented bag. It then covers selenosis from Brazil nuts, iron replacement after gastric bypass, and why dietary calcium is preferred over pills.

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Key topics

• ·Refeeding syndrome physiology
• ·Thiamine before glucose and Wernicke encephalopathy
• ·NICE criteria for refeeding risk
• ·Slow calorie start and electrolyte monitoring
• ·Albumin and prealbumin as inflammatory markers
• ·GLIM criteria and nutrition screening
• ·Indications for nutrition support
• ·Enteral versus parenteral nutrition
• ·Nasal tube versus PEG and placement technique
• ·PEG complications and tube-feed diarrhea
• ·Indications for parenteral nutrition
• ·Calorie counting and dextrose
• ·Calcium, phosphate, and acetate in the bag
• ·Mixed lipid emulsions and cycling
• ·Line infection and locks
• ·Gallstones and liver disease from parenteral nutrition
• ·When parenteral nutrition harms
• ·Short bowel anatomy and prognosis
• ·Oral rehydration, drugs, and cholestyramine
• ·Teduglutide, oxalate stones, and D-lactic acidosis
• ·Fat-soluble vitamin deficiency in cholestasis
• ·Vitamin A deficiency and night blindness
• ·Vitamin D repletion with calcium
• ·Vitamin E deficiency
• ·Vitamin K, warfarin, and antibiotics
• ·Vitamin A hepatotoxicity
• ·Essential fatty acid deficiency and MCT oil
• ·B12 absorption steps and deficiency
• ·Folate deficiency and bacterial overgrowth
• ·Pellagra, pyridoxine, thiamine, vitamin C, and biotin