Lower GI & Bowel Disorders - Cheat Sheet
Your last-minute revision companion for Lower GI & Bowel Disorders. This cheat sheet covers inflammatory bowel disease, IBS, diverticular disease, appendicitis, intestinal obstruction, hemorrhoids, and ostomies—the high-yield NLE topics. Focus on the Crohn's vs UC distinctions, appendicitis safety rules, and ostomy care.
Inflammatory Bowel Disease (IBD) — Crohn's Disease vs Ulcerative Colitis
Important facts
- Crohn's: mouth → anus, SKIP lesions, TRANSMURAL depth, cobblestone appearance, fistulas & strictures COMMON, malabsorption (fat, B12, folate), weight loss; surgery NOT curative.
- UC: colon & rectum ONLY, CONTINUOUS from rectum, mucosa/submucosa ONLY, bloody mucoid diarrhea (10–20/day), tenesmus, rarely fistulas; colectomy IS curative.
- Both cause diarrhea, abdominal pain, weight loss, fatigue, fever, anemia, and nutritional deficiencies.
- Gold standard diagnostic: colonoscopy with biopsy; CT/MRI enterography for Crohn's fistulas; fecal calprotectin & CRP/ESR mark activity.
- During flares: LOW-residue, HIGH-protein, HIGH-calorie diet; avoid high-fiber, dairy (if lactose intolerant), caffeine, cold, spicy foods.
- During remission: HIGH-fiber diet to maintain gut health and prevent relapse.
- Severe flares with malnutrition → bowel rest with TPN (total parenteral nutrition).
- Monitor for electrolyte imbalances (hypokalemia, hyponatremia) from chronic diarrhea and fluid loss.
- Colorectal cancer risk is higher in UC (long-standing disease) than Crohn's; surveillance colonoscopy every 1–2 years after 8 years of disease.
Key definitions
Crohn's Disease
Example
Patient presents with cobblestone mucosa, fistulas, and weight loss due to fat/B12/folate malabsorption.
Chronic transmural inflammation of the entire GI tract (mouth to anus) in a skip-lesion pattern, often involving the terminal ileum; causes malabsorption and is NOT cured by surgery.
Ulcerative Colitis (UC)
Example
Patient with 15–20 bloody, mucoid diarrheal stools daily and toxic megacolon risk.
Chronic mucosal inflammation limited to the colon and rectum in a continuous pattern, starting at the rectum; is cured by total colectomy.
Toxic Megacolon
Example
UC patient with sudden abdominal distension, fever, tachycardia, and absence of bowel sounds.
Life-threatening complication of UC: massive colonic dilatation (>6 cm) with fever, tachycardia, and abdominal rigidity; requires urgent surgical decompression.
Skip Lesions
Example
Colonoscopy shows inflamed segment, then normal area, then inflamed again in Crohn's.
Patchy, discontinuous areas of inflammation separated by normal mucosa—pathognomonic of Crohn's disease.
Diagrams to know
- Layers of bowel wall affected in Crohn's vs UC
- Continuous vs skip-lesion pattern
- Fistula formation in Crohn's disease
IBD Pharmacology — Key Drugs & Monitoring
Important facts
- Sulfasalazine: Give with FOOD + PLENTY OF FLUIDS; contains sulfa (allergy caution); causes ORANGE-YELLOW URINE; supplement FOLIC ACID (impairs absorption); check baseline G6PD deficiency.
- Mesalamine: Better tolerated than sulfasalazine (no sulfa component); different formulations for colon vs ileum delivery.
- Corticosteroids: Taper SLOWLY to avoid acute adrenal insufficiency; monitor for hyperglycemia, bone loss (osteoporosis), Cushingoid features, infection.
- Azathioprine/6-MP: Baseline CBC, LFTs; monitor white count weekly × 4, then monthly; expect 6–12 weeks for therapeutic effect.
- Infliximab/Adalimumab: Screen TB (tuberculin skin test or IGRA) and hepatitis B (anti-HBc, anti-HBs, HBsAg) BEFORE starting; risk of reactivation.
- Biologics: Watch for infection (TB, fungal, opportunistic), malignancy, demyelination, and heart failure; educate on signs of infection.
- Never combine two immunosuppressants (e.g., azathioprine + infliximab) without specialist guidance due to infection risk; increases lymphoma risk.
Key definitions
Aminosalicylates (5-ASA)
Example
Sulfasalazine 2–4 g/day given with food and fluids to reduce side effects.
First-line agents for mild–moderate UC and Crohn's; examples: sulfasalazine, mesalamine; reduce inflammation by local action on colonic mucosa.
Corticosteroids (Prednisone/IV Hydrocortisone)
Example
Prednisone 40–60 mg/day for acute flare, then taper by 5–10 mg weekly.
Used for acute flares only (short-term, 6–8 weeks); taper gradually—NEVER stop abruptly due to adrenal insufficiency risk.
Immunomodulators
Example
Azathioprine 1–2 mg/kg/day after baseline CBC to prevent infection and hepatotoxicity.
Steroid-sparing agents (azathioprine, 6-MP, methotrexate) used for remission maintenance; monitor CBC and liver function (bone marrow suppression risk).
Biologics (Anti-TNF Agents)
Example
Infliximab IV infusion; patient presents with fever and chills 2 days after first dose (infusion reaction).
Infliximab, adalimumab; bind TNF-α to reduce inflammation; MUST screen for latent TB and hepatitis B before initiating; monitor for infusion reactions and infection.
Diagrams to know
- Mechanism of action of 5-ASA agents
- TNF-α pathway and anti-TNF drug targets
Irritable Bowel Syndrome (IBS)
Important facts
- IBS is FUNCTIONAL—no blood, weight loss, nocturnal symptoms, or fever (RED FLAGS for organic disease).
- Pain RELIEVED by defecation is KEY feature distinguishing IBS from other disorders.
- Bloating, gas, mucus in stool are common but not diagnostic.
- NO colonoscopy findings, normal labs, normal imaging; diagnosis is clinical (Rome IV criteria).
- Avoid dairy, high-fat foods, caffeine, alcohol, and FODMAPs (fermentable carbohydrates); identify individual triggers.
- Stress, anxiety, and depression exacerbate symptoms; cognitive-behavioral therapy (CBT) and stress management are cornerstone.
- Regular meals, adequate hydration, exercise, and sleep hygiene improve outcomes.
- Pharmacology: Antispasmodics (dicyclomine, hyoscyamine) for cramping; loperamide for diarrhea; lactulose/polyethylene glycol for constipation.
- Never assume abdominal pain is IBS without ruling out organic disease first (e.g., celiac disease, lactose intolerance, IBD).
Key definitions
Irritable Bowel Syndrome (IBS)
Example
Patient complains of cramping pain relieved after bowel movement, bloating, and alternating diarrhea and constipation.
Functional GI disorder with altered motility and visceral hypersensitivity; NO structural or inflammatory lesion; manifests as chronic abdominal pain relieved by defecation with altered bowel habits.
IBS-D
Example
Patient reports frequent loose stools with cramping; colonoscopy normal.
IBS with diarrhea predominance (≥1/4 stools loose/watery, <1/4 hard).
IBS-C
Example
Patient strains to pass hard stools 1–2 times weekly; imaging and labs normal.
IBS with constipation predominance (≥1/4 stools hard/lumpy, <1/4 loose).
IBS-M
Example
Some weeks mostly diarrhea, other weeks mostly constipation.
IBS mixed type; patient has both loose and hard stools in different weeks.
Diagrams to know
- Rome IV diagnostic criteria for IBS
Diverticular Disease
Important facts
- Diverticulosis is FROM low-fiber diet, chronic constipation, and high intraluminal pressure.
- Sigmoid colon is MOST common site (90% of cases).
- Diverticulitis = LLQ pain + fever + altered bowel habits + leukocytosis.
- CT scan is PREFERRED diagnostic tool for acute diverticulitis; shows inflamed/thickened diverticulum, pericolic fat stranding, abscess.
- AVOID colonoscopy and barium enema during ACUTE phase (perforation risk); perform 4–6 weeks AFTER flare resolves.
- Acute uncomplicated diverticulitis: NPO, clear liquids, IV fluids, antibiotics (metronidazole + ciprofloxacin or ceftriaxone).
- Complicated diverticulitis (perforation, abscess, peritonitis): IV antibiotics, possible percutaneous drain, then elective colectomy.
- After first flare: elective colectomy is often recommended (recurrence risk ~20% after first episode, >50% after second).
- PREVENTION: HIGH-FIBER diet (25–35 g/day) + 2 L fluids daily when well; avoid NSAIDs and aspirin (increase perforation risk).
- During acute flare: LOW-fiber, clear liquids, rest; advance diet slowly after fever subsides.
- Complications: perforation, abscess, peritonitis, obstruction, fistula (colovesical, colovaginal, colocutaneous).
Key definitions
Diverticulosis
Example
Incidental finding on CT scan in asymptomatic 65-year-old patient.
Presence of multiple outpouchings (diverticula) of colonic mucosa, usually sigmoid colon, from low-fiber diet and chronic constipation; often asymptomatic.
Diverticulitis
Example
Patient with sudden LLQ pain, fever 38.5°C, WBC 13,000; CT shows inflamed diverticulum with fat stranding.
Inflammation and/or infection of a diverticulum; presents with LEFT lower quadrant pain, fever, leukocytosis, and altered bowel habits.
Perforation (Diverticulitis Complication)
Example
Acute abdomen with rigid board-like abdomen, absent bowel sounds, fever, shock—requires emergency surgery.
Rupture of inflamed diverticulum spilling fecal content into peritoneum; causes peritonitis, sepsis, and shock.
Diagrams to know
- Diverticulitis formation and progression
- Sigmoid vs descending colon anatomy
Appendicitis — CRITICAL Safety Rules
Important facts
- CLASSIC presentation: Periumbilical pain → migrates to RLQ at McBurney's point over 6–12 hours.
- Associated: Anorexia, nausea/vomiting, low-grade fever (38–38.5°C), rebound tenderness (Blumberg's sign), guarding, mild leukocytosis (10,000–15,000).
- Differential: Ectopic pregnancy, pelvic inflammatory disease (PID), Crohn's disease, gastroenteritis, mesenteric adenitis.
- Ultrasound or CT scan confirms diagnosis (appendiceal diameter >6 mm, wall thickening, echogenic fat).
- Definitive treatment: APPENDECTOMY (open or laparoscopic).
- ⚠️ NEVER apply HEAT to abdomen—increases circulation, promotes rupture. Cold packs acceptable.
- ⚠️ NEVER give LAXATIVES or ENEMAS—increase peristalsis and perforation risk.
- ⚠️ NEVER give strong opioid analgesics that mask symptoms until surgical evaluation (per institutional policy).
- Position: Semi-Fowler's or right side flexed for comfort.
- ⚠️ DANGER: Sudden RELIEF of pain may indicate RUPTURE—expect return of severe pain + rigidity + fever + sepsis.
- Post-rupture: Fever spikes, abdominal rigidity worsens, bowel sounds disappear (paralytic ileus), rapid sepsis → peritonitis management.
- NPO status until surgery; IV fluids and antibiotics (third-generation cephalosporin, e.g., ceftriaxone, + metronidazole).
- Appendectomy is the ONLY definitive treatment; antibiotics alone insufficient and delay risks perforation.
Key definitions
Appendicitis
Example
Periumbilical pain migrating to RLQ, rebound tenderness, fever, positive Rovsing's sign → urgent appendectomy.
Inflammation of the appendix from obstruction (fecalith, lymphoid hyperplasia) leading to bacterial overgrowth, ischemia, and if untreated, perforation and peritonitis; most common cause of acute abdomen.
McBurney's Point
Example
Pain localizes to McBurney's point with guarding and rebound tenderness.
Midway between umbilicus and right anterior superior iliac spine (ASIS); point of maximal tenderness in appendicitis.
Rovsing's Sign
Example
Palpate LLQ → patient grimaces and points to RLQ (positive Rovsing's).
RLQ pain elicited by palpation of LLQ (referred pain from pressure on inflamed appendix); suggests appendicitis.
Psoas Sign
Example
Patient lies on left side, extend right hip → RLQ pain.
RLQ pain with hip extension (psoas muscle stretch); suggests retrocecal appendicitis.
Obturator Sign
Example
Flex right hip and knee, internally rotate → RLQ pain.
RLQ pain with internal hip rotation; suggests pelvic appendicitis.
Diagrams to know
- McBurney's point location on abdomen
- Appendicitis signs and symptoms progression
- Appendiceal obstruction → inflammation → perforation pathway
Intestinal Obstruction
Common values
Value
>6 cm
Symbol
d
Quantity
Colonic diameter indicating toxic megacolon or impending perforation
Value
<3 cm
Symbol
d_SB
Quantity
Normal small-bowel diameter
Value
<5 cm
Symbol
d_colon
Quantity
Normal colon diameter
Important facts
- Adhesions account for 60–75% of mechanical small-bowel obstructions (most often post-op or from peritonitis).
- Hernias, tumors (colon cancer most common large-bowel cause), volvulus, and intussusception are other mechanical causes.
- SMALL-BOWEL obstruction: Early vomiting, crampy pain, high-pitched 'tinkling' bowel sounds initially, then silent; minimal distension initially; rapid fluid/electrolyte loss.
- LARGE-BOWEL obstruction: Gradual onset over days; marked distension (abdominal girth ↑↑); obstipation (no stool or flatus); late vomiting; less fluid loss.
- SBO leads to METABOLIC ALKALOSIS (loss of HCl from vomiting); LBO leads to METABOLIC ACIDOSIS (loss of bicarbonate).
- Diagnostics: Upright chest X-ray (free air if perforated), abdominal X-rays (air-fluid levels, dilated loops, transition point), CT enterography (gold standard—shows site, cause, complications).
- Priority management: NPO, NGT for decompression (low intermittent suction), IV fluids (NS or LR depending on electrolytes), electrolyte replacement (K+, Mg2+, Ca2+), strict I&O charting.
- Treat underlying cause: Surgery for mechanical obstruction (adhesiolysis, hernia repair, tumor resection); supportive care for ileus (mobilization, correct electrolytes, remove opioids).
- Monitor for STRANGULATION (fever, rising pain, tachycardia, peritoneal signs, metabolic acidosis, elevated lactate)—requires URGENT surgery.
- Partial small-bowel obstruction may resolve with conservative management (NPO, NGT, fluids); complete obstruction or strangulation requires surgery.
- Post-op adhesions often recur; counseling on preventing post-op ileus (early mobilization, incentive spirometry, minimize opioids) is key.
Key definitions
Mechanical Obstruction
Example
Post-op patient day 3 with colicky pain, vomiting, and absence of flatus; CT shows transition point.
Physical blockage of the intestinal lumen; causes include adhesions (most common post-op), hernia, tumor, volvulus, and intussusception.
Paralytic Ileus (Functional Obstruction)
Example
Post-op day 1, patient has abdominal distension and absent bowel sounds but no mechanical obstruction on imaging.
Loss of intestinal motility WITHOUT mechanical blockage; caused by post-operative state, peritonitis, electrolyte imbalance (hypokalemia), opioids, or spinal trauma.
Small-Bowel Obstruction (SBO)
Example
Patient vomits 500 mL bilious fluid within hours of onset; labs show pH 7.50, low K+ (hypokalemia).
Blockage in the small intestine; causes early, profuse vomiting (may be bilious/feculent), cramping pain, high-pitched bowel sounds then silence, minimal distension, rapid dehydration, and metabolic ALKALOSIS (loss of gastric acid).
Large-Bowel Obstruction (LBO)
Example
Elderly patient with abdominal distension, no bowel movement × 3 days, minimal vomiting; CT shows colonic dilatation >6 cm.
Blockage in the colon; causes gradual onset, marked distension, obstipation (no stool/gas), late vomiting, and metabolic ACIDOSIS (loss of bicarbonate).
Strangulation
Example
Obstructed patient with escalating pain, fever 39°C, HR 120, and signs of peritonitis (rigid abdomen).
Vascular compromise of bowel segment (loss of blood supply); causes intense pain, fever, tachycardia, rising WBC, and shock; SURGICAL EMERGENCY.
Diagrams to know
- Small-bowel vs large-bowel obstruction characteristics
- Metabolic acid-base derangements in SBO vs LBO
- Progression from obstruction to strangulation
Peritonitis
Common values
Value
>250/μL
Symbol
PMN_SBP
Quantity
PMN count diagnostic of spontaneous bacterial peritonitis
Important facts
- Signs of peritonitis: RIGID ('board-like') abdomen, diffuse severe pain + rebound tenderness everywhere, absent bowel sounds (paralytic ileus), fever, tachycardia, tachypnea.
- Rapid progression to septic shock: ↑ HR, ↓ BP, altered mental status, oliguria, lactic acidosis.
- Perforation sources: Appendicitis, perforated peptic ulcer, diverticulitis, strangulated bowel, trauma.
- Diagnostics: Upright chest X-ray (free air under diaphragm), CT abdomen/pelvis, blood cultures, CBC (leukocytosis), lactate (elevated = ischemic/septic).
- Priority care: NPO, aggressive IV fluid resuscitation (NS or LR, target urine output >0.5 mL/kg/h), broad-spectrum IV antibiotics IMMEDIATELY (e.g., piperacillin-tazobactam or ceftriaxone + metronidazole + gentamicin), blood cultures before antibiotics.
- NGT for decompression (reduces ileus, aspiration risk).
- URGENT surgical source control (repair perforation, remove necrotic bowel, peritoneal lavage).
- Position: Semi-Fowler's (30° head elevation) to localize infection to pelvis and ease respiratory effort.
- Prognosis: High mortality (10–30%) if delayed treatment; increases with age, comorbidities, and sepsis severity.
- Post-op monitoring: Watch for anastomotic leak, abscess formation, wound infection, and recurrent peritonitis.
Key definitions
Peritonitis
Example
Ruptured appendix patient with rigid 'board-like' abdomen, severe pain, fever, and shock.
Life-threatening inflammation of the peritoneum from perforation of a hollow viscus (ruptured appendix, perforated ulcer/diverticulum, strangulated bowel) or bacterial translocation; requires emergency surgical source control.
Spontaneous Bacterial Peritonitis (SBP)
Example
Cirrhotic with ascites, fever, abdominal pain; paracentesis shows PMN 400/μL + E. coli growth.
Peritonitis in patients with ascites (cirrhosis) WITHOUT perforation; due to bacterial translocation; confirmed by paracentesis (PMN >250/μL, positive culture).
Diagrams to know
- Peritonitis causes and progression
- Septic shock cascade in peritonitis
Hemorrhoids
Important facts
- Hemorrhoids result from straining (constipation, prolonged sitting, chronic cough), pregnancy, portal hypertension, and chronic diarrhea.
- Internal hemorrhoids: Painless, bright-red bleeding (blood on paper or in stool), prolapse, mucus discharge, feeling of incomplete evacuation.
- External hemorrhoids: Painful (somatic nerves), palpable bulge, itching, thrombosis (severe pain).
- Diagnostic: Visual inspection, digital rectal exam, anoscopy (grade internal hemorrhoids: Grade I no prolapse, II prolapse then spontaneously reduce, III require manual reduction, IV permanently prolapsed).
- Conservative management: HIGH-FIBER diet (25–35 g/day), adequate fluids (2 L/day), stool softeners (docusate), sitz baths (15 min, 2–3 times daily after bowel movement), topical anesthetics (lidocaine), witch hazel.
- Avoid straining, prolonged sitting, and NSAIDs (increase bleeding).
- Procedural: Rubber-band ligation (Grade I–III internal), sclerotherapy, infrared coagulation; hemorrhoidectomy (surgical) for Grade IV or thrombosed external.
- Post-op teaching: Sitz baths, stool softeners, increase fiber/fluids; expect first bowel movement to be painful/anxiety-provoking (use analgesics 30 min prior).
- Complications: Bleeding (iron-deficiency anemia if chronic), thrombosis (extreme pain), strangulation, infection.
Key definitions
Internal Hemorrhoids
Example
Patient reports bright-red blood on toilet paper after bowel movement; no pain.
Dilated rectal veins above the dentate line; painless (visceral innervation), present with bright-red bleeding on toilet paper or in stool, and may prolapse.
External Hemorrhoids
Example
Patient with severe perianal pain and palpable swollen mass; thrombosed external hemorrhoid.
Dilated anal veins below the dentate line; painful (somatic innervation), palpable, and may thrombose.
Diagrams to know
- Internal vs external hemorrhoid anatomy
- Hemorrhoid grading system
Ostomy Care & Management
Common values
Value
1/3–1/2 full
Symbol
threshold
Quantity
Recommended ileostomy pouch emptying threshold
Value
0.25–0.5 cm (1/8–1/4 inch)
Symbol
stoma_height
Quantity
Normal stoma protrusion above skin
Value
2.5–3 L
Symbol
fluid_ileostomy
Quantity
Recommended daily fluid intake (ileostomy patient)
Important facts
- Normal stoma: PINK/RED, MOIST, no bleeding with gentle touch.
- ⚠️ REPORT IMMEDIATELY: Dark, dusky, purple, or BLACK stoma (ischemia/necrosis); pale or depressed stoma; bleeding; purulent drainage.
- Ileostomy: Liquid output CONTINUOUS throughout day; contains proteolytic enzymes → HIGH RISK of peristomal skin breakdown; patient needs METICULOUS skin protection.
- Ileostomy risk: Dehydration, hypokalemia, hyponatremia (loss of water, K+, Na+ in liquid stool); HIGH fluid/electrolyte needs; supplement salt and water.
- Ileostomy diet: Avoid high-fiber foods initially (blockage risk); foods to limit: seeds, nuts, corn, celery, popcorn; encourage soft, well-chewed foods.
- Colostomy output: Transverse/ascending—paste-like continuous output. Descending/sigmoid—more formed, can sometimes be regulated by irrigation (water enema via stoma catheter).
- Appliance (pouch) management: Empty when 1/3–1/2 full (prevent leakage and odor); sizing important—opening should be only slightly larger than stoma (1/8 inch margin) to prevent skin exposure.
- Pouch change: Every 3–5 days (ileostomy) or every 5–7 days (colostomy); use barrier paste/wafers to protect skin.
- Odor management: Avoid gas-forming foods (beans, cruciferous veggies, carbonated drinks), limit odor-producing foods (eggs, fish, onions, asparagus); use odor-neutralizing drops in pouch; empty pouch regularly.
- Nutrition: Ileostomy patients need extra fluids (2.5–3 L/day) and salt; supplement salt intake; monitor for B12/fat-soluble vitamin malabsorption.
- Sexual/body-image support: Offer counseling, encourage open discussion, suggest pouching during intimate activity; patient may experience grief and adaptation challenges.
- Return to activities: Most patients resume normal activities, swimming (waterproof appliance), and exercise; provide psychological support for acceptance.
- Blockage risk (ileostomy): High-fiber foods, inadequate chewing, inadequate fluids; teach signs: cramps, decreased output, nausea → increase fluids, soft food, possible heat.
Key definitions
Stoma
Example
Patient with permanent ileostomy for familial polyposis has pink, moist stoma protruding 0.5 cm; output is liquid and continuous.
An opening in the abdominal wall created to divert stool (colostomy, ileostomy) or urine (urostomy) externally; normal appearance is PINK/RED and MOIST (like oral mucosa).
Ileostomy
Example
Patient's ileostomy output is pasty to liquid; peristomal skin is erythematous and macerated from enzyme irritation.
Stoma created from the terminal ileum; output is LIQUID, CONTINUOUS, and contains digestive ENZYMES (proteolytic, lipase); high risk of skin breakdown and dehydration/electrolyte loss.
Colostomy
Example
Sigmoid colostomy patient has formed stool output 1–2 times daily and may achieve continence with irrigation.
Stoma created from the colon; output thickens based on location (ascending = paste-like, transverse = paste, descending/sigmoid = formed); continuous to periodic depending on sphincter function.
Peristomal Dermatitis
Example
Ileostomy patient with exposed skin under appliance; area is red, raw, and painful from enzyme exposure.
Inflammation/breakdown of skin around the stoma from prolonged contact with stool, enzymes, or irritants; presents as erythema, maceration, or erosion.
Diagrams to know
- Ileostomy vs colostomy location and output characteristics
- Stoma appliance sizing and application
- Peristomal skin care protocol
Colorectal Cancer — Screening & Risk Factors
Important facts
- CRC risk factors: Age >50, family/personal Hx of polyps or CRC, IBD (UC > Crohn's), high red/processed meat + low fiber diet, smoking, obesity, sedentary lifestyle, PTEN/Lynch syndrome.
- UC patients have higher colorectal cancer risk than Crohn's patients; lifetime risk ~10–15% in UC with pancolitis.
- Left-sided (descending/sigmoid) and rectal cancers: Early symptoms—change in bowel habit, rectal bleeding, visible blood in stool, incomplete evacuation (tenesmus), constipation or diarrhea.
- Right-sided (cecal/ascending) cancers: Present LATE with anemia (occult bleeding), vague abdominal symptoms, weight loss, palpable mass.
- Colonoscopy: Gold standard for screening and diagnosis (allows visualization, biopsy, and removal of polyps); can visualize entire colon.
- Screening recommendations: Begin age 50 (45 in African Americans); every 10 years if normal; earlier/more frequent if polyps, family history, or IBD.
- IBD surveillance: Colonoscopy every 1–2 years after 8 years of disease (increased CRC risk); may need dye spraying (chromoendoscopy) to detect dysplasia.
- Nurse role: Reinforce screening importance, educate on warning signs (change in bowel habits, rectal bleeding, anemia), support patients through diagnostic workup, and provide post-procedure care (colonoscopy recovery, dietary guidelines).
Key definitions
Colorectal Cancer (CRC)
Example
65-year-old with 12-year history of UC now presents with change in bowel habits, rectal bleeding, and iron-deficiency anemia.
Malignancy of the colon or rectum; risk factors include age >50, family history, long-standing IBD (especially UC), high red/processed meat diet, low fiber, smoking, obesity, and sedentary lifestyle.
Diagrams to know
- Colorectal cancer risk stratification
Constipation & Diarrhea — Foundational Management
Common values
Value
25–35 g
Symbol
fiber_daily
Quantity
Daily fiber intake recommendation
Value
2–3 L
Symbol
fluids_daily
Quantity
Daily fluid intake recommendation (general population)
Value
3–21 times/week
Symbol
stool_freq_normal
Quantity
Normal stool frequency
Important facts
- Constipation: Increase FIBER (25–35 g/day gradually—too fast causes bloating) and FLUIDS (2–3 L/day); mobilize; establish regular toileting routine.
- Bulk-forming agents (psyllium, methylcellulose): First-line; work by retaining water in stool and increasing bulk; take with plenty of fluids.
- Osmotic laxatives (lactulose, polyethylene glycol, magnesium citrate): Draw water into intestinal lumen; safe for chronic use; lactulose may cause bloating/flatulence.
- Stimulant laxatives (bisacodyl, senna): Short-term use only (≤1 week); risk LAXATIVE DEPENDENCE and electrolyte loss if used chronically.
- Stool softeners (docusate): Increase water absorption into stool; safe, often paired with bulk-forming agents.
- ⚠️ Avoid chronic stimulant laxative use—risk cathartic colon and electrolyte depletion.
- Opioid-induced constipation: Educate on high-risk; use prophylactic stool softener + osmotic laxative; consider opioid rotation or reduced dose.
- Diarrhea: Priority is FLUID & ELECTROLYTE REPLACEMENT; oral rehydration solution (ORS) first-line (WHO-approved: 50 mEq Na+, 20 mEq K+, 20 mEq Cl−, 2% glucose).
- Infectious/inflammatory diarrhea: AVOID antimotility agents (loperamide, diphenoxylate) if bloody stools or fever present (risk toxic megacolon, prolonged infection).
- Non-infectious diarrhea (IBS-D, lactose intolerance): Antimotility agents acceptable; loperamide first-line.
- Diarrhea risks: Dehydration (especially <5 yrs, >65 yrs), hypokalemia (muscle weakness, arrhythmias), hyponatremia, metabolic acidosis (loss of HCO3−), malnutrition.
- Perianal skin care: Frequent washing and drying; barrier creams (zinc oxide); avoid toilet paper (use wipes or warm water); change diapers/pads frequently in incontinence.
Key definitions
Constipation
Example
Post-op patient on opioids has no bowel movement × 4 days; when does pass, stool is hard and requires straining.
Infrequent, hard, difficult-to-pass stools (typically <3 stools/week); causes include low fiber/fluids, immobility, opioids, medications, and ignoring the defecation urge.
Diarrhea
Example
Patient with acute gastroenteritis has 6–8 watery stools daily, is dehydrated, and has hypokalemia (K+ 3.0 mEq/L).
Loose, watery stools (>3/day or >200 g/day); risks dehydration, electrolyte loss (K+, Na+, HCO3−), and malnutrition, especially in infants and elderly.
Diagrams to know
- Causes of constipation and diarrhea
- Electrolyte losses in diarrhea
Must remember
- Crohn's disease: Mouth-to-anus location, SKIP lesions, TRANSMURAL inflammation, cobblestone mucosa, fistulas & strictures COMMON, malabsorption (fat, B12, folate)—surgery is NOT curative. Ulcerative colitis: Colon & rectum ONLY, CONTINUOUS from rectum, mucosa/submucosa ONLY, BLOODY mucoid diarrhea, toxic megacolon risk, tenesmus—colectomy IS curative.
- Sulfasalazine: Give with FOOD + plenty of FLUIDS; supplement FOLIC ACID (impairs absorption); causes ORANGE-YELLOW urine; check for sulfa allergy. Infliximab/adalimumab (biologics): MUST screen for latent TB and hepatitis B BEFORE starting; monitor for infusion reactions and infection.
- IBS is FUNCTIONAL—NO structural/inflammatory lesion, NO blood/weight loss/nocturnal symptoms; pain is RELIEVED by defecation. Red flags (blood, weight loss, fever, nocturnal symptoms) point to organic disease; rule out IBD, celiac, lactose intolerance.
- Diverticulitis = LLQ pain + fever + leukocytosis; CT is diagnostic. AVOID colonoscopy/barium enema ACUTELY (perforation risk). HIGH-FIBER diet is for PREVENTION (when well); LOW-FIBER during acute flare.
- Appendicitis: Periumbilical pain → RLQ pain at McBurney's point + rebound tenderness. CRITICAL safety rules: NEVER apply heat, NEVER give laxatives/enemas, NEVER give strong opioids until surgical eval. Sudden pain RELIEF = RUPTURE (peritonitis follows).
- Small-bowel obstruction: EARLY profuse vomiting, METABOLIC ALKALOSIS (loss of HCl). Large-bowel obstruction: MARKED distension, obstipation, METABOLIC ACIDOSIS. Strangulation (fever, rising pain, peritonitis) = SURGICAL EMERGENCY.
- Peritonitis (perforation → sepsis): Rigid 'board-like' abdomen, diffuse severe pain + rebound tenderness, absent bowel sounds, fever, shock. Priority: NPO, aggressive IV fluids, broad-spectrum antibiotics immediately, URGENT surgical source control. Position semi-Fowler's.
- Ostomy: Normal stoma is PINK/RED and MOIST. Dark/dusky/BLACK stoma = ischemia (REPORT). Ileostomy output is LIQUID & CONTINUOUS with ENZYMES (high skin breakdown risk & dehydration risk). Empty pouch at 1/3–1/2 full; appliance opening slightly larger than stoma to prevent skin exposure.
- Ileostomy patient: Needs extra fluids (2.5–3 L/day) and salt supplementation; high risk of hypokalemia, hyponatremia; avoid high-fiber foods initially (blockage); monitor for B12/fat-soluble vitamin malabsorption. Body-image support critical.
- Toxic megacolon (UC emergency): Abdominal distension, fever, tachycardia, absent bowel sounds, peritoneal signs. Requires URGENT decompression (NGT, rectal tube) and surgical evaluation; high mortality if delayed. Risk from antidiarrheals/antispasmodics in UC flares.
Last minute tips
- APPENDICITIS is the MOST TESTED lower GI disorder on NLE exams. Memorize the safety rules: NO heat, NO laxatives, NO enemas, NO strong analgesics until surgical eval. Know McBurney's point location, Rovsing's sign, psoas/obturator signs, and the danger of sudden pain relief = rupture.
- CROHN'S vs UC distinction appears on almost EVERY exam. Test yourself: If the question mentions FISTULAS, TRANSMURAL, mouth-to-anus, or malabsorption → Crohn's. If it mentions BLOODY diarrhea, colon-only, continuous inflammation, or toxic megacolon → UC. Use the comparison table.
- Biologics (infliximab, adalimumab) are HIGH-YIELD. Memorize: MUST screen for latent TB and hepatitis B BEFORE starting. Post-injection, monitor for infusion reactions, infection (including TB reactivation), and counsel patient on signs of TB.
- On exam, if you see 'LLQ pain + fever + no mechanical obstruction,' think DIVERTICULITIS. Remember: CT is diagnostic; colonoscopy is contraindicated acutely. HIGH-fiber prevents it; LOW-fiber during acute episode.
- Ostomy questions often focus on skin breakdown, stoma color, and output characteristics. RED flags: Dark stoma (ischemia), liquid output without barrier (ileostomy skin breakdown), appliance too loose (exposes skin). Remember: EMPTY at 1/3–1/2 full and size appliance opening 1/8 inch larger than stoma.
Comparison tables
Crohn's Disease vs Ulcerative Colitis — Side-by-Side Comparison
| Feature | Crohn's Disease | Ulcerative Colitis |
|---|---|---|
| Location | Mouth → anus (anywhere in GI tract); often terminal ileum | Colon & rectum ONLY |
| Pattern | SKIP lesions (patchy, discontinuous) | CONTINUOUS from rectum |
| Depth | TRANSMURAL (full thickness) | Mucosa & submucosa ONLY |
| Gross appearance | Cobblestone mucosa, ulcers, fissures | Continuous ulceration, friability |
| Stool characteristics | Soft to semi-liquid; LESS bloody | FREQUENT bloody, mucoid diarrhea (10–20/day) |
| Fistulas/strictures | COMMON | RARE |
| Perianal disease | COMMON (skin tags, abscesses, fistulas) | RARE |
| Malabsorption | COMMON (fat, B12, folate, fat-soluble vitamins) | Less common |
| Weight loss/nutrition | MARKED (from malabsorption + diarrhea) | Variable |
| Extraintestinal manifestations | Arthritis, pyoderma gangrenosum, erythema nodosum, iritis, uveitis | Arthritis, erythema nodosum, primary sclerosing cholangitis (PSC) |
| Toxic megacolon | RARE | COMMON (life-threatening) |
| Cancer risk | Increased (modest) | HIGHER colorectal cancer risk |
| Cure by surgery? | NO—recurs in neo-terminal ileum | YES—total colectomy is curative |
Small-Bowel Obstruction vs Large-Bowel Obstruction
| Feature | Small-Bowel Obstruction | Large-Bowel Obstruction |
|---|---|---|
| Onset | ACUTE (hours) | GRADUAL (days) |
| Vomiting | EARLY, profuse, bilious/feculent | LATE or absent |
| Pain character | CRAMPING, colicky | Continuous, distension |
| Abdominal distension | MINIMAL early, increased later | MARKED, progressive |
| Bowel sounds | HIGH-PITCHED, 'tinkling' initially, then silent | ABSENT or diminished |
| Constipation | Late (or may have diarrhea initially) | Early, obstipation (NO flatus/stool) |
| Fluid loss | RAPID, copious (from vomiting) | Gradual |
| Dehydration severity | SEVERE, rapid | Moderate |
| Acid-base disorder | METABOLIC ALKALOSIS (loss of HCl) | METABOLIC ACIDOSIS (loss of HCO3−) |
| Imaging findings | Air-fluid levels, dilated small bowel loops (<3 cm), transition point | Dilated colon (>5 cm), haustral markings, transition point |
| Most common cause | Adhesions (post-op) | Colorectal cancer |
| Conservative management success | Partial SBO may resolve; complete requires surgery | Less likely; usually requires surgery |
Internal vs External Hemorrhoids
| Feature | Internal Hemorrhoids | External Hemorrhoids |
|---|---|---|
| Location | Above dentate line (upper anal canal) | Below dentate line (anal margin) |
| Innervation | Visceral (no pain sensation) | Somatic (sensitive to pain) |
| Pain | PAINLESS | PAINFUL (especially if thrombosed) |
| Bleeding | BRIGHT-RED, on toilet paper or in stool | May bleed if ulcerated; usually no bleeding |
| Palpable mass | Not palpable internally; may feel as bulge if prolapsed | PALPABLE swelling at anal verge |
| Prolapse | May prolapse, especially Grade III–IV | No prolapse (external location) |
| Appearance on exam | Visualized via anoscopy; red/purple | Visible externally; may be skin-colored or purple if thrombosed |
| Grading system | Grade I–IV (I = no prolapse, IV = permanent prolapse) | Not graded; described as uncomplicated or thrombosed |
| Treatment (conservative) | Fiber, fluids, sitz baths, topical anesthetics | Same; more emphasis on pain management |
| Procedural treatment | Rubber-band ligation (Grade I–III), sclerotherapy, infrared coagulation | Rarely needed; may be anesthetized and incised if thrombosed |
| Surgical treatment | Hemorrhoidectomy for Grade IV or refractory cases | Hemorrhoidectomy for thrombosed or symptomatic |
Ileostomy vs Colostomy Output Characteristics
| Feature | Ileostomy | Colostomy (by location) |
|---|---|---|
| Output consistency | LIQUID to pasty, CONTINUOUS | Ascending: paste-like continuous; Transverse: paste, 2–3×/day; Descending: formed, 1–2×/day; Sigmoid: formed, 1–2×/day (regulates) |
| Frequency | Continuous (8–10 times/day on average) | Periodic to continuous (ascending/transverse continuous; descending/sigmoid 1–2×/day) |
| Contains enzymes? | YES (proteolytic, lipase)—erosive to skin | NO—less erosive |
| Skin breakdown risk | HIGH—requires meticulous care, barriers | Lower risk |
| Dehydration/electrolyte loss | HIGH risk (liquid output); needs fluid/salt supplementation | Lower risk; formed stool retains more fluid |
| Pouch change frequency | Every 3–5 days (liquid output changes appliance faster) | Every 5–7 days |
| Diet restrictions | Avoid high-fiber, seeds, nuts, corn; chew well (blockage risk) | More relaxed; can usually eat most foods |
| Continence achievement | NO—always requires appliance | Descending/sigmoid may achieve continence with irrigation |
Diagrams
Appendicitis Diagnosis & Management Pathway
Flowchart showing the diagnostic and management pathway for appendicitis, emphasizing the critical safety rules (no heat, laxatives, enemas, or opioids) and the risk of rupture with escalation to peritonitis.
Inflammatory Bowel Disease (IBD) Overview
Mind map depicting the key distinctions between Crohn's disease and ulcerative colitis, diagnostic methods, pharmacological agents, and management strategies for both IBD conditions.
Intestinal Obstruction Assessment & Management
Flowchart guiding the differential diagnosis and management of mechanical vs functional intestinal obstruction, with emphasis on small-bowel vs large-bowel distinctions and strangulation risk.
Ostomy Care & Complication Detection
Flowchart for assessing ostomies, identifying normal vs abnormal stoma appearance, distinguishing output types, and implementing appropriate skin care and complication prevention.
Diverticulitis Diagnosis & Management
Flowchart detailing the diagnostic pathway for diverticulitis, severity stratification, acute management, and prevention strategies post-recovery.
Appendicitis Progression & Danger Points
State diagram showing the progression of appendicitis from obstruction through potential complications (perforation, peritonitis) and the critical danger point of sudden pain relief followed by rigidity, emphasizing the importance of early surgical intervention.