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 predictable metabolic crisis that follows resumption of carbohydrate after a period of starvation, and it is the highest-yield single decision point in inpatient nutrition.

• Section 32.2: Hospital malnutrition and the albumin trap

  Inpatient nutrition decisions hinge 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 stereotyped, recognizable phenotypes.

Podcast episodes

1. 01

   Refeeding, Malnutrition, and Enteral Access

   Episode one of the GI Nutrition chapter builds the inpatient nutrition framework and the enteral access decisions. The organizing idea is that the labs lie and the instinct to feed faster is usually wrong. Refeeding syndrome is what happens when a starvation-adapted patient meets a carbohydrate load, so the active intervention is restraint with thiamine before glucose. Hospital malnutrition is not what a low albumin says it is, so GLIM separates the phenotypic deficit from the etiologic cause. And the route of nutrition follows the gut's functional state, with a functional gut winning every time.

   Read the transcript →
2. 02

   Parenteral Nutrition and Short Bowel Syndrome

   Episode two takes the patient whose gut cannot do the work. Parenteral nutrition is a tool for a non-functional gut, with composition rules that follow from chemistry rather than biology and indication discipline that follows from trial data. Its long-term complications are driven by the loss of enteral stimulation, from gallbladder stasis and IFALD to manganese parkinsonism and catheter biofilm infection. Short bowel syndrome then turns on residual anatomy, where the colon's presence or absence determines both the rehabilitation trajectory and the complication pattern, and teduglutide's trophic effect explains both its efficacy and its surveillance burden.

   Read the transcript →
3. 03

   Soluble and Water-Soluble Vitamins

   Episode three reads the vitamins the way the boards test them, where every micronutrient produces a stereotyped phenotype that is the recognition cue on a stem. Behind each cue is a biochemical mechanism, and the same mechanism predicts the at-risk population and the replacement strategy. Memorizing the symptom list is the wrong frame; learning the mechanism lets the phenotype, the population, and the treatment fall out of it. The fat-soluble vitamins share a bile-salt absorption requirement, and the water-soluble vitamins carry the acute decisions, thiamine before glucose and B12 before folate.

   Read the transcript →
4. 04

   Minerals and Trace Elements

   Episode four closes the chapter with the minerals and trace elements, which run on the same logic as the vitamins: each element has a specific biochemical role and a specific exposure or pathology context that produces its phenotype. The boards favor the pairs that turn on a single mechanism, zinc inducing metallothionein to trap copper, cholestasis blocking biliary manganese excretion, and Brazil nuts concentrating selenium. Each element pairs a recognition cue with a population and a replacement strategy, the same teaching unit used for the vitamins.

   Read the transcript →

Key topics

• ·Refeeding syndrome and the electrolyte shift
• ·Thiamine before glucose and Wernicke
• ·NICE high-risk criteria
• ·Restrained calorie reintroduction
• ·Albumin as an inflammatory marker
• ·GLIM phenotypic plus etiologic criteria
• ·Functional gut and enteral access selection
• ·PEG techniques and complications
• ·Tube-feed diarrhea and the medication list
• ·When parenteral nutrition is the answer
• ·Composition rules from chemistry
• ·Lipid emulsions and IFALD
• ·Indication discipline versus cachexia
• ·Cholelithiasis and manganese parkinsonism
• ·Catheter-related bloodstream infection
• ·Short bowel anatomic phenotypes
• ·Teduglutide and surveillance
• ·Enteric hyperoxaluria and D-lactic acidosis
• ·Bile-salt requirement for fat-soluble vitamins
• ·Vitamin A night blindness and toxicity
• ·Vitamin D metabolic bone disease
• ·Vitamin E neuropathy, hemolysis, and NASH
• ·Vitamin K, warfarin, and the NPO patient
• ·Essential fatty acid deficiency
• ·Thiamine and Wernicke encephalopathy
• ·B12 absorption steps and pernicious anemia
• ·B12-versus-folate masking trap
• ·Iron deficiency and malabsorptive anatomy
• ·PPI-induced hypomagnesemia and TRPM6
• ·Zinc acrodermatitis and dysgeusia