Lower Gastrointestinal Problems – Comprehensive Study Notes

Diarrhea

• Definition & temporal classification

  • Acute: \le 14\,\text{days}

  • Persistent: >14\,\text{days} but \le 30\,\text{days}

  • Chronic: >30\,\text{days}

• Etiology & pathophysiology

  • Primary U.S. cause ➜ infectious organisms (esp. viruses)

  • Notable pathogens & presentations

  • Norovirus, rotavirus – watery stool

  • E.\,coli\,O157! :! H7 – hemorrhagic colitis, possible HUS

  • Giardia lamblia – protozoan; greasy, foul-smelling stool

  • Clostridium\,difficile (CDI) – antibiotic-associated colitis

  • Mechanisms of injury

  • Secretory: organisms ↑ secretion/↓ absorption in enterocytes; little/no inflammation

  • Inflammatory: organisms destroy mucosa, provoke colonic inflammation, generate toxins ➜ impaired absorption, exudation

• Transmission pathways

  • Contaminated food/water

  • Fecal–oral contact, esp. in LTCFs, day-care

• Host susceptibility

  • Elderly (↓ immunity, comorbidities)

  • ↓ Gastric acidity (PPIs, H2 blockers) ➜ ↑ survival of pathogens

  • Altered gut flora (broad-spectrum antibiotics)

  • Immunocompromised states; jejunal tube feedings

• Non-infectious causes

  • Drugs: laxatives, Mg antacids, antibiotics, metformin, chemotherapy

  • Food intolerances: large sugar alcohol load, lactose, gluten, caffeine

  • Osmotic: rapid GI transit (tube feeds, gastrectomy)

  • Malabsorption: celiac disease, short-bowel syndrome

• Clinical manifestations

  • Upper GI source: large-volume watery stool, crampy peri-umbilical pain, N/V, minimal fever

  • Lower GI source: small-volume, frequent, possibly bloody stool; fever

  • Severe cases: dehydration (\textit{fluid volume deficit}), hypokalemia, metabolic acidosis

  • CDI: fulminant colitis, toxic megacolon, perforation

• Diagnostic studies

  • Stool culture (blood, mucus, WBCs, ova/parasites, C. diff toxin)

  • Blood culture if septic/immunocompromised

  • Labs: CBC, electrolytes, \text{BUN/Cr}, serum osmolality, pH

  • Specialized: fecal fat/protein, GI hormones for secretory diarrhea

• Interprofessional management

  • Prevent transmission (contact precautions)

  • Replace fluids & electrolytes (oral rehydration or IV LR/NS)

  • Protect perianal skin (barrier creams, meticulous hygiene)

  • Antidiarrheals (if no infection suspected)

  • Coaters (bismuth), absorbents (kaolin-pectin), opiate analogs (loperamide, diphenoxylate), antisecretories (octreotide)

  • Contraindicated in IBD flare ➜ risk of toxic megacolon

• CDIFF-specific care

  • HAI; spores survive \le 70\,\text{days} on surfaces

  • Strict contact isolation; soap-and-water handwash, 10 % bleach surface disinfection

  • First-line Rx: oral vancomycin 125\,\text{mg} q6h × 10 d OR fidaxomicin

  • Alternatives: metronidazole (mild), vanco + IV metro (severe/complicated)

  • Ileus ➜ vancomycin retention enema

  • Stop non-essential abx, laxatives, antidiarrheals

  • Recurrent CDI ➜ fecal microbiota transplantation (FMT) via colonoscopy, enema, or nasoenteric tube

  • Consider probiotic (\textit{Lactobacillus}) prophylaxis

• Nursing priorities

  • Assume infectious until proven otherwise

  • Accurate I&O; daily weight; inspect skin

  • Teach hygiene, safe food handling, early HCP contact for blood/dehydration

Constipation

• Definition & features

  • Symptom, not a disease

  • Difficult/infrequent BM, excessive straining, sensation of incomplete evacuation

  • Acute: <1\,\text{week}; Chronic: >3\,\text{months}

• Risk factors

  • Low-fiber diet

  • Decreased physical activity

  • Ignoring urge to defecate ➜ rectal desensitization, stool desiccation

  • Emotional stress, anxiety, depression

  • Conditions slowing transit: DM, Parkinson’s, hypothyroid, spinal cord injury, scleroderma

  • Meds: opioids, anticholinergics, Ca/Al antacids, iron, antidepressants

  • Chronic stimulant laxative use ➜ cathartic colon (dilated, atonic)

• Clinical manifestations

  • Hard, dry, infrequent stool; straining

  • Abdominal distention, bloating, flatulence, rectal pressure

  • Hemorrhoids, anal fissures

  • Diverticulosis (elderly)

  • Obstipation/fecal impaction, perforation (rare)

• Diagnostics

  • Thorough H&P; DRE, abdominal exam

  • Alarm signs >6 wk: hematochezia, anemia, wt loss, pain, FHx CRC/IBD

  • Imaging: plain ABD film, barium enema, colonoscopy, anorectal manometry, balloon expulsion, sitz-mark transit study

• Management

  • ↑ dietary fiber (20–30 g/day), fruits/veg/whole grains; fluid \ge 2\,\text{L}/day

  • Regular exercise & defecation schedule

  • Laxatives (bulk-forming, osmotic, stool softeners, stimulants) – use judiciously

  • Enemas for acute impaction

  • Peripherally acting \mu-opioid receptor antagonists (methylnaltrexone) for OIC

  • Biofeedback for pelvic-floor dysfunction

  • Surgery (subtotal colectomy, ostomy) for refractory cases

• Nursing care

  • Individualize plan; educate on diet, hydration, exercise

  • Encourage not ignoring urge; proper positioning; privacy

  • Discourage chronic laxative/enema abuse

Chronic Abdominal Pain

• Qualities: dull, aching, diffuse, intermittent >3 mo

• Common etiologies: IBS, chronic pancreatitis, chronic hepatitis, PID, adhesions, mesenteric ischemia

• Work-up: comprehensive H&P, pain diary, labs, endoscopy, CT/MRI, laparoscopy

• Therapy: treat cause; multidisciplinary pain management

Irritable Bowel Syndrome (IBS)

• Functional disorder: recurrent abdominal pain + altered bowel habits without structural cause ≥3 mo

• Rome IV diagnostic criteria

  • Abdominal pain on \ge 1\,\text{day/week} × 3 mo, with ≥2:

  1. Related to defecation

  2. Change in stool frequency

  3. Change in stool form

• Subtypes

  • IBS-C (constipation-predominant)

  • IBS-D (diarrhea-predominant)

  • Mixed

  • Unsubtyped

• Gender trends

  • Women 2–2.5× > men; more IBS-C, bloating, fatigue, depression

  • Men: more IBS-D, less likely to seek care

• Triggers

  • Psychological stress, anxiety, depression

  • Post-infectious gut dysbiosis

  • Food sensitivities: gluten, FODMAPs (fructans, lactose, sorbitol, etc.)

• Symptoms

  • GI: crampy pain, bloating, gas, mucus in stool, sense of incomplete evacuation

  • Non-GI: fatigue, HA, sleep disturbance

• Management

  • Therapeutic alliance, reassurance

  • Cognitive-behavioral therapy, stress reduction

  • Diet: low-FODMAP, trial gluten-free, adequate fiber for IBS-C

  • Pharmacology

  • IBS-D: loperamide, bile-acid binders, eluxadoline, rifaximin, alosetron (\textbf{Drug Alert: ischemic colitis})

  • IBS-C: soluble fiber, osmotic laxatives, lubiprostone, linaclotide

  • Antispasmodics (dicyclomine), TCAs/SSRIs for pain modulation

Inflammatory Bowel Disease (IBD)

• Chronic immune-mediated inflammation with remissions & exacerbations

• Two primary phenotypes

  • Ulcerative colitis (UC): mucosal layer of colon/rectum

  • Crohn’s disease (CD): transmural, any part mouth→anus; terminal ileum common

• Etiology

  • Genetic susceptibility (>200 genes, NOD2 variants)

  • Environment: diet high in refined sugar, fat, ω-6; smoking, stress, NSAIDs, antibiotics, OCPs

  • Microbiome dysregulation

  • Autoimmune dysregulation ➜ uncontrolled cytokine cascade (TNF-α, IL-12/23) → tissue destruction

• Pathology

  • Crohn’s

  • Skip lesions, cobblestone mucosa, strictures, fistulas, abscesses

  • Transmural granulomatous inflammation

  • UC

  • Continuous lesion from rectum proximally

  • Only mucosa/submucosa; pseudopolyps; toxic megacolon risk

• Clinical presentation

  • CD: diarrhea, crampy pain, weight loss, low-grade fever, fatigue, occasional rectal bleeding

  • UC: bloody diarrhea; stool frequency correlates w/ severity

  • Mild <4/d; Moderate ≤10/d; Severe 10–20/d ± fever, anemia, tachycardia

  • Pain, weight loss, fatigue

• Complications

  • Local: hemorrhage, strictures, perforation, abscess, fistula, CDI, toxic megacolon

  • Systemic: ↑ risk CRC (esp. >8 yr disease), cholangiocarcinoma, malabsorption, osteoporosis, spondyloarthropathies, PSC, erythema nodosum, uveitis

• Diagnostics

  • CBC (anemia, leukocytosis), BMP (lytes), albumin, ESR/CRP, stool ova/parasites & cultures

  • Imaging: double-contrast BE, small-bowel follow-through, CT/MRI enterography, US

  • Endoscopy: colonoscopy w/ biopsies; capsule endoscopy for CD

• Therapeutic goals

  • Rest bowel, control inflammation, fight infection, correct malnutrition, alleviate stress, symptom relief, QOL improvement

• Pharmacologic therapy (step-up vs step-down)

  • 5! -! ASA agents: sulfasalazine, mesalamine (PO/PR) – 1st line UC

  • Corticosteroids: prednisone, budesonide, IV methyl-pred for flares (short-term)

  • Immunomodulators: azathioprine, 6-MP, methotrexate (maintenance)

  • Biologics

  • Anti-TNF: infliximab (IV), adalimumab, certolizumab, golimumab

  • Integrin antagonists: natalizumab, vedolizumab

  • Risks: infection (TB, HBV), malignancy; no live vaccines

  • JAK inhibitor (tofacitinib) for moderate-severe UC

• Surgical options

  • UC: curative

  • Total proctocolectomy + IPAA (J- or S-pouch)

  • Total proctocolectomy + permanent ileostomy

  • CD: surgery for complications; resection w/ anastomosis, strictureplasty; risk short-bowel syndrome

• Nutrition

  • Individualized; high-cal/high-protein during remission

  • Acute flare: enteral elemental formulas; may need TPN

  • Supplements: folate (sulfasalazine), Ca/Vit D (steroids), B12 (ileal disease), Fe, Zn, Mg, trace elements

  • Food diary to identify triggers (dairy, high-fat, cold foods, high-fiber in strictures)

• Nursing care

  • Monitor hemodynamics, pain, stool output, weight, labs

  • I&O, daily wt, assess for bleeding, infection, skin integrity

  • Pre-/post-op ostomy teaching

  • Coping strategies; CCFA resources

• Gerontologic considerations

  • Second incidence peak ~60 yr; left-sided UC common

  • Atypical sx; polypharmacy ↑ adverse effects

  • ↑ infection, malignancy risk; ambulatory limitations

Diverticular Disease

• Definitions

  • Diverticula: saccular mucosal outpouchings in colon wall, most sigmoid

  • Diverticulosis: presence of multiple diverticula without inflammation

  • Diverticulitis: inflammation of a diverticulum

• Etiology

  • Weak points where vasa recta penetrate circular muscle

  • ↑ intraluminal pressure from constipation/straining

  • Low-fiber diet, obesity, inactivity, smoking, excess ETOH, NSAIDs, genetics

• Clinical manifestations

  • Diverticulosis: often asymptomatic; possible LLQ pain, bloating, flatulence, change bowel habit; hematochezia

  • Diverticulitis: acute LLQ pain, fever, leukocytosis, ↓/absent BS, N/V; elderly may be afebrile

• Complications: perforation, abscess, fistula, peritonitis, hemorrhage

• Diagnostics

  • CT Abd w/ oral contrast (preferred)

  • Sigmoidoscopy/colonoscopy once inflammation resolved

  • Labs: CBC, UA, blood cultures, FOBT; XR to r/o free air

• Management

  • Prevention: high-fiber, ↓ fat/red meat, weight control, exercise

  • Acute mild: bowel rest (clear liquids), oral abx, analgesia

  • Severe/septic/comorbid: NPO, NG suction, IV fluids, broad-spectrum IV abx, monitor for abscess/peritonitis

  • Recurrent/complicated: elective sigmoid resection ± temporary colostomy

• Education: 2 L fluids/day, avoid straining, lifting, tight belts

Malabsorption Syndromes

• General: defective absorption of fat, CHO, protein, vitamins, minerals, water

• Hallmarks: weight loss, diarrhea, steatorrhea (bulky, pale, foul, oil-ring stool)

• Common causes

  • Lactose intolerance (most prevalent)

  • IBD, celiac disease, tropical sprue, cystic fibrosis

  • Short-bowel syndrome, pancreatic insufficiency, bile-acid deficiency

• Diagnostic tests

  • Stool fat (\textit{Sudan III}), fecal elastase

  • D-xylose absorption, lactose tolerance/H2 breath

  • Serology: anti-tTG IgA for celiac

  • Imaging: small-bowel follow-through, CT, capsule endoscopy

  • Labs: CBC, PT (Vit K), vit A, carotene, lytes, Ca, cholesterol

Celiac Disease

• Autoimmune enteropathy triggered by gluten (prolamines) in genetically predisposed (HLA-DQ2/DQ8)

• Associated autoimmune disorders: RA, T1DM, thyroiditis

• Manifestations

  • Classic: foul diarrhea, abdominal pain, flatulence, distention, malnutrition

  • Atypical: osteoporosis, fertility issues, neuropathy, dermatitis herpetiformis

  • Laboratory: Fe-def anemia, ↓ folate, B12

• Diagnosis:

  • Serology (anti-tTG, EMA) while on gluten diet

  • Upper endoscopy + duodenal biopsy (villous atrophy)

  • Genetic HLA typing (supportive)

• Management

  • Strict gluten-free diet (no wheat, barley, rye)

  • Dietician referral; monitor Ca/Vit D, Fe, B12

  • Resources: CSA, CDF

Lactase Deficiency

• Absent/low lactase enzyme ➜ unabsorbed lactose fermented in colon

• Populations: Asians, Africans, premature infants, Congenital rare

• Symptoms within 30 min of dairy: bloating, cramps, flatulence, diarrhea

• Diagnosis: lactose tolerance test, H2 breath test, genetic testing

• Treatment: lactase enzyme (Lactaid), lactose-free diet, Ca & Vit D supplementation

Short-Bowel Syndrome (SBS)

• <25–30 % functional small intestine

• Causes: massive resections (Crohn’s, volvulus), congenital atresia, necrotizing enterocolitis

• Manifestations: chronic diarrhea, malnutrition, wt loss, dehydration, steatorrhea, lyte deficits (Mg, Zn)

• Care

  • Fluid/lyte replacement, antidiarrheals (loperamide), acid suppression

  • Nutritional support: TPN initial, transition to enteral; high-complex CHO, low-fat; MCT oil

  • GLP-2 analog (teduglutide) to enhance adaptation

  • Intestinal transplant for refractory failure

Gastrointestinal Stromal Tumor (GIST)

• Rare mesenchymal tumor from interstitial cells of Cajal; KIT or PDGFRA mutation

• Early nonspecific: early satiety, bloating, N/V, altered BM

• Late: GI bleed, obstruction

• Diagnosis: EUS-guided biopsy, CT/MRI

• Treatment: surgical resection; imatinib (tyrosine-kinase inhibitor) for unresectable/metastatic

Hemorrhoids

• Varicose dilatation of hemorrhoidal veins

  • Internal (above dentate line)

  • External (below dentate line)

• Risk factors: pregnancy, constipation/straining, diarrhea, heavy lifting, prolonged sitting/standing, obesity, ascites

• Clinical

  • Internal: painless bright-red bleeding, mucus, prolapse causing dull ache

  • External: bluish mass, pruritus, burning, edema; thrombosis → severe pain

• Diagnosis: inspection, DRE; anoscopy/sigmoidoscopy for internal

• Management

  • Conservative: high-fiber diet, ↑ fluids, stool softeners, topical anesthetics/astringents, sitz baths

  • Office procedures: rubber-band ligation, infrared coagulation, sclerotherapy, laser

  • Surgical hemorrhoidectomy for large prolapse or thrombosis

• Post-op nursing: pain control (opioids, NSAIDs, topical), packing care, encourage fiber/fluids, avoid straining, watch for urinary retention, bleeding

Anal Disorders

Anal Fissure

• Linear ulcer in anoderm from trauma (hard stool, vaginal delivery) or IBD/STD

• Severe burning pain with BM, bright-red bleeding

• Therapy: fiber, fluids, stool softeners, topical nitroglycerin/diltiazem, botulinum inj; lateral internal sphincterotomy if chronic

Anal Fistula

• Abnormal tract from anal canal to perianal skin/vagina; often post-abscess or Crohn’s

• Purulent/bloody drainage, pruritus

• Treatment: fistulotomy; complex tracts may need LIFT procedure, advancement flap, fibrin glue/plug