GI & Nutritional Disorders – Comprehensive Study Notes

Malnutrition and Nutrition Problems

• Definitions
  • Malnutrition = deficit, excess, or imbalance of essential nutrients.
  • Sub-types
  • Over-nutrition: intake exceeds requirements.
  • Under-nutrition: nutrient/energy intake insufficient for basal needs or added stress; reserves depleted.
• Etiology categories (ASPEN taxonomy)
  • Starvation-related malnutrition (Primary Protein–Calorie Malnutrition)
  • Chronic starvation, little/no inflammation.
  • Ex: anorexia nervosa.
  • Chronic disease–related malnutrition (Secondary PCM)
  • Sustained mild–moderate inflammation.
  • Ex: organ failure, cancer, RA, obesity.
  • Acute disease or injury–related malnutrition
  • Marked inflammatory response.
  • Ex: sepsis, burns, trauma, major surgery.
• Contributing factors
  • Socioeconomic (food insecurity, “heat-or-eat” choices, limited support).
  • Physical illnesses, hospitalisation, GI diseases.
  • Impaired absorption ↓enzymes, ↓surface area, drug S/E, ↑BMR w/ fever.
  • Incomplete diets (alcohol/drug use disorders, chronic illness, fad diets).
• Starvation process
  • 1st 18 h: use glycogen.
  • Next: skeletal protein → gluconeogenesis; later 97 % calories from fat.
  • Fat stores gone ≈ 4–6 wks ⇒ visceral + body protein catabolised.
  • ↓Liver fx → ↓albumin → ↓oncotic P → edema; liver fatty, shrinks.
  • Death unless protein supplied.
• Clinical manifestations (mild → emaciation)
  • Dry/scaly skin, brittle nails, hair loss, mouth ulcers, ↓muscle, fatigue.
  • Mental changes, infection risk, anemia.
• Screening / Assessment
  • The Joint Commission: nutrition screen ≤24 h of admission.
  • MUST tool (BMI + wt-loss + acute-disease score)
  • \text{BMI > 20}\Rightarrow0\qquad18.5{-}20\Rightarrow1\qquad<18.5\Rightarrow2
  • Add wt-loss & \text{NPO}>5 d; total ≥2 = high risk.
  • BMI equation BMI=\frac{\text{Wt (lb)}\times703}{\text{Ht (in)}^{2}}
  • Under-wt <18.5\,kg/m^{2}; normal 18.5{-}24.9; overweight 25{-}29.9; obesity \ge30.
• Food guidance: USDA MyPlate – 5 groups visual cue.

Enteral Nutrition (EN)

• Definition: nutritionally complete formula via tube → GI tract (stomach, duodenum, jejunum) when oral unsafe/insufficient.
• Indications: anorexia, orofacial fractures, H/N cancer, neuro/psych d/o, burns, critical illness, chemo, radiation.
• Contra-indications: GI obstruction, prolonged ileus, severe V/D, high-output enterocutaneous fistula.
• Access routes
  • Short-term: NG, nasoduodenal, nasojejunal.
  • Long-term: gastrostomy (PEG), jejunostomy.
• Administration safety
  • Confirm placement (x-ray on insertion, mark exit site, re-check q feed/8 h).
  • HOB ≥30^{\circ} (continue 30–60 min post bolus).
  • Monitor gastric residual per policy; consider promotility drugs.
• Complications
  • Aspiration, vomiting, diarrhea, constipation, dehydration (high calorie dense formulas), refeeding syndrome (hallmark = hypophosphatemia), tube site skin irritation, accidental removal.
• Advantages vs PN: physiologic, cheaper, lower infection risk.

Parenteral Nutrition (PN)

• Definition: IV infusion of dextrose, amino acids, lipids, electrolytes, vitamins, trace elements; “TPN”.
• Indications: severe V/D, bowel obstruction, short-bowel, severe malabsorption, anorexia nervosa, complicated surgery/trauma, GI fistulae.
• Routes
  • Central PN (via PICC, subclavian, IJ): long-term, hypertonic.
  • Peripheral PN: short-term, lower osmolarity.
• Complications
  • Refeeding syndrome (↓P, ↓K, ↓Mg, fluid retention).
  • Metabolic: hyper/hypoglycemia, fatty acid deficiency, ↑TG, liver dysfunction, renal issues.
  • Catheter related: infection/sepsis, air embolus, thrombosis, occlusion, hemorrhage.

Obesity

• Epidemiology
  • 43\% US adults obese; highest in South/Midwest, Black & Hispanic, low-income/education.
• Pathophysiology
  • Energy intake > expenditure → hypertrophy & hyperplasia of adipocytes (most visceral/subQ). >400 genes influence appetite, satiety, metabolism.
  • Primary vs secondary (endocrine, CNS lesions, meds e.g., corticosteroids).
• Environmental/Psychosocial contributors: high-calorie food access, large portions, sedentariness, screen time, stress eating.
• Health risks (Fig 45-5): CVD, DM2, HTN, OSA, NAFLD/NASH, cancers, OA, psychosocial issues.
• Assessment
  • BMI, waist circumference (>40'' men, >35'' women), waist-to-hip ratio, comorbidities labs (lipid, FBG, LFT, TSH).
• Management goals: modify diet, ↑exercise (\ge150 min/wk moderate), 5-10 % wt loss improves outcomes.
• Behavior therapy tools: self-monitoring logs, stimulus control, reward systems; strong motivation (appearance) predicts success.
• Pharmacology (BMI ≥30 or ≥27+comorbidity)
  • Orlistat – blocks fat absorption (steatorrhea).
  • Lorcaserin (5-HT agonist) – ↑satiety.
  • Phentermine/topiramate; bupropion/naltrexone.
• Bariatric Surgery
  • Criteria: BMI ≥40 or ≥35+comorbidity.
  • Procedures: Adjustable gastric band, sleeve gastrectomy, Roux-en-Y gastric bypass, BPD w/ duodenal switch.
  • Produces greatest sustained weight loss.

Upper GI Disorders

Nausea & Vomiting

• Many etiologies (GI, CNS, CV, pregnancy, drugs). Complications: dehydration, electrolyte loss (K, Na, Cl), metabolic alkalosis.
• Assess emesis characteristics (bright red ⇒ active bleed; coffee-ground ⇒ gastric bleed; fecal odor ⇒ distal obstruction; projectile ⇒ ↑ICP).
• Care: identify cause, NPO/IVF, anti-emetics tailored, aspiration precautions, semi-Fowler.

Gastro-Esophageal Reflux Disease (GERD)

• Patho: incompetence of LES ± delayed gastric emptying → reflux of corrosive gastric juices → esophagitis, strictures, Barrett’s esophagus (precancerous).
• Risk factors: ↑gastric volume post meals, obesity, tight clothes, smoking, hiatal hernia.
• Symptoms: heartburn post-prandial & supine, dysphagia, hoarseness, chest pain.
• Dx: barium swallow, EGD, pH monitoring.
• Management
  • Lifestyle: upright ×3 h post meal, HOB elevated, small meals, avoid triggers (caffeine, alcohol, chocolate, peppermint, fatty/spicy), weight loss.
  • Drugs: H2 blockers, PPIs.
  • Surgery: Nissen fundoplication if refractory.

Hiatal Hernia

• Stomach herniates through diaphragm.
  • Sliding – slides when supine; paraesophageal – beside esophagus, risk strangulation.
• Similar care to GERD; surgery if complications.

Gastritis

• Inflammation d/t mucosal barrier breakdown; acute (drugs, alcohol, stress) or chronic (H. pylori, autoimmune, toxins).
• Manifestations: anorexia, N/V, epigastric pain, fullness, melena/anemia.
• Dx: H&P, endoscopy, H. pylori tests, CBC, occult blood.
• Management: remove cause, PPIs/H2B, sucralfate, antibiotics for H. pylori, 6 small bland meals; acute usually self-limits.

Peptic Ulcer Disease (PUD)

• Ulceration in lower esophagus, stomach, duodenum from acid-pepsin.
• Risk: H. pylori (most common), NSAIDs/ASA, smoking.
• Types
  • Gastric: pain 1{-}2 h post-meal, worsens with food.
  • Duodenal: pain 2{-}5 h post-meal, relief with food/antacids.
• Complications: hemorrhage (melena/hematemesis), obstruction, perforation (rigid board-like abdomen, rebound tender, shock).
• Dx: EGD with biopsy, H. pylori tests, UGI/barium.
• Therapy: \text{PPI}+2 antibiotics (clarithro + amox or metro); adjunct H2B, sucralfate, misoprostol, antacids; avoid NSAIDs, smoking, alcohol.
• Complication care: NG decompression, IV antibiotics, surgery PRN.

Pharmacology Quick Reference (GI)

• H2 Receptor Blockers – cimetidine (many S/E, ↑warfarin), famotidine (Pepcid), ranitidine* withdrawn.
• PPIs – omeprazole, esomeprazole; give ≥1 h before breakfast; long-term risk C. diff, osteoporosis.
• Sucralfate – GI protectant; coats ulcer; give on empty stomach, 2 h apart from meds.
• Misoprostol – prostaglandin analog prevents NSAID ulcers; contraindicated pregnancy.
• Antacids – calcium carbonate (constipation/rebound), magnesium hydroxide (diarrhea), aluminum salts (constipation). Separate other meds ≥2 h.
• Antidiarrheals – loperamide (Imodium; no <2 y/o, high doses → arrhythmia), bismuth subsalicylate (black stool/tongue; salicylate toxicity tinnitus; avoid with ASA).
• Laxatives
  • Bulk: psyllium; safe long-term; need fluids; space meds 2 h.
  • Stimulant: bisacodyl.
  • Osmotic: sodium phosphate (Fleet).
  • Lubricant: docusate mineral oil (↓fat-vit absorption, lipid pneumonia if aspirated).

Lower GI Disorders

Diarrhea

• Patho: ↑motility (↓absorption) or ↑secretion (infection, osmotic). Report bloody diarrhea.
• Risks: dehydration, metabolic acidosis (HCO₃⁻ loss).
• Assessment: frequency, girth, sounds, hydration, meds, food.
• Dx tests when severe/bloody: cultures, O&P, WBC, C-diff, sigmoidoscopy.
• Management: treat cause, fluid/e-lyte replace, hold solids 24 h then small meals; avoid antidiarrheals in infection.

Clostridioides difficile

• Spores persist 70 days; handwash with soap; contact isolation; clean surfaces (EPA list K).
• Tx: PO vancomycin 125 mg QID or fidaxomicin; stop other abx; metronidazole alt; recurrent: fecal microbiota transplant.

Constipation

• ↓frequency, hard stool, straining; Valsalva risk ↑ICP, cardiac strain.
• Causes: low fiber/fluids, inactivity, ignoring urge, chronic stimulant laxatives, obstruction.
• Tx: high fiber, fluids 2 L, exercise, bulk laxatives, avoid chronic stimulants; education.

Fecal impaction

• Putty mass; seepage; treat with oil retention enema → cleansing → manual removal (vagal risk).

Irritable Bowel Syndrome (IBS)

• Functional; Rome IV ≥1 day/wk ×3 mo abdominal pain + stool change.
• Subtypes: IBS-C, IBS-D, mixed, unsubtyped.
• Triggers: stress, infection, food intolerances (gluten, lactose, FODMAPs).
• Care: CBT, stress mgmt, low-FODMAP diet, exercise, antispasmodics (dicyclomine), antidepressants; IBS-D – rifaximin, alosetron; IBS-C – linaclotide, lubiprostone.

Inflammatory Bowel Disease (IBD)

Ulcerative Colitis

• Continuous superficial inflammation from rectum proximally; bloody diarrhea, LLQ pain, tenesmus.
• Complications: toxic megacolon, perforation, colorectal CA.

Crohn’s Disease

• Transmural skip lesions anywhere GI (terminal ileum common); non-bloody diarrhea, RLQ pain, weight loss, fistulas, malabsorption (B₁₂).
• Diagnostics: colonoscopy, SBFT, labs.
• Drug goals: induce/maintain remission.
  • 5-ASA, corticosteroids, antimicrobials, immunomodulators (azathioprine), biologics (anti-TNF).
• Surgery
  • UC: total proctocolectomy curative (ileostomy).
  • Crohn: segmental resection/strictureplasty; risk short-bowel.
• Nutrition: high-calorie, high-protein, low-residue; enteral preferred during flares; avoid trigger foods, lactose, cold/high-fat.

Diverticular Disease

• Diverticulosis = sacs; diverticulitis = inflamed/perforated.
• Risks: low-fiber diet, aging, sedentary.
• S/S: LLQ pain, fever, constipation/diarrhea.
• Tx: NPO → clear → high-fiber; antibiotics; surgery if abscess/perforation.
• Prevention: fiber-rich diet, ↓fat/red meat, fluids ≥2 L, avoid straining.

Hemorrhoids & Anal Disorders

• Hemorrhoids: dilated rectal veins; internal painless bleeding, external painful; risk pregnancy, constipation.
  • Conservative: high fiber/water, stool softeners, sitz baths, anesthetic creams.
  • Procedures: sclerotherapy, rubber-band ligation, hemorrhoidectomy (post-op care checklist).
• Anal fissure: linear tear; severe pain; sitz baths, topical analgesia, stool softeners; maybe lateral sphincterotomy.
• Anorectal abscess: obstructed gland; pain, swelling, fever; surgical drainage, moist heat.
• Anal fistula: tract from rectum to skin/vagina; surgery (fistulotomy, LIFT).

Diagnostic & Monitoring Highlights

• EGD: NPO 8 h, consent, sedation; post – gag reflex, temp q15–30 min (perforation).
• Upper GI/Barium swallow & Lower GI/Barium enema: NPO 8 h; post – laxatives, fluids, stools white ≤72 h.
• MUST, BMI, waist metrics as earlier.

Ethical / Practical Considerations

• Non-judgmental communication about weight & nutrition; clarify need for sensitive questions.
• Ensure informed consent for invasive procedures; respect cultural dietary practices.
• Address food insecurity with community resources.
• Infection control: C-diff isolation, hand hygiene—protect patients & staff.

Quick Reference Equations & Values

• BMI=\dfrac{kg}{m^{2}}\quad\text{or}\quad BMI=\dfrac{lb\times703}{in^{2}}
• MUST scoring ≥2 = high risk.
• Waist risk: Men >40'', Women >35''.
• Exercise goal: 150 min moderate / wk or 75 min vigorous.
• EN head-of-bed \ge30^{\circ}; refeeding ↓P hallmark.