Most colorectal cancers are adenocarcinomas that develop slowly (often over 10 years or more) from adenomatous polyps. Because the polyp stage is long, screening and polyp removal prevent cancer. The cancer spreads through the bowel wall, to regional lymph nodes, and then most often to the liver (portal venous drainage) and lungs.

Risk factors

• Age (risk rises with age; incidence in adults under 50 is increasing)
• Personal or family history of CRC or advanced adenomas
• Inherited syndromes: Lynch syndrome (hereditary nonpolyposis CRC), familial adenomatous polyposis (FAP)
• Inflammatory bowel disease (long-standing colitis)
• Diet high in red and processed meat, low in fiber; obesity, physical inactivity, smoking, heavy alcohol use; type 2 diabetes
• Protective: regular physical activity, fiber-rich diet, healthy weight

Clinical picture by location

The most common presenting problem overall is a change in bowel habits or rectal bleeding; many early cancers cause no symptoms.

• Change in bowel habits, blood in or on stool, abdominal pain, bloating
• Fatigue, pallor, dyspnea on exertion (anemia); unintentional weight loss
• Obstruction: distension, vomiting, absent stool and flatus
• Family and personal history, screening history
• Advanced disease: hepatomegaly, jaundice, ascites

Anemia in any older adult, especially men and postmenopausal women, needs evaluation for GI blood loss.

Screening (average risk) — US Preventive Services Task Force (2021): begin at age 45 and continue through age 75; individualize for ages 76–85.

• Any positive stool-based or imaging test must be followed by colonoscopy
• Blood-based screening tests (FDA-approved from 2024) are not among the USPSTF-endorsed first-line options
• Higher-risk clients (family history, Lynch, IBD) start earlier and screen more often

Diagnosis and staging

• Colonoscopy with biopsy — confirms diagnosis
• CT chest, abdomen, pelvis — staging; MRI pelvis for rectal cancer
• Carcinoembryonic antigen (CEA) — the most widely used CRC tumor marker; used for baseline, response to treatment, and detecting recurrence, not for screening
• CBC, liver tests; tumor molecular testing (mismatch repair/microsatellite instability, RAS, BRAF) guides therapy

Bowel preparation for colonoscopy: clear liquids the day before, split-dose preparation; watch older adults and those with kidney or heart disease for dehydration and electrolyte imbalance.

Surgery — the main curative treatment

• Colectomy (right, left, sigmoid) with lymph node removal and anastomosis
• Rectal cancer: low anterior resection (sphincter-preserving), often with a temporary diverting ileostomy; or abdominoperineal resection (APR) for very low tumors → permanent colostomy and perineal wound
• Emergency surgery for obstruction or perforation may need a temporary stoma; colonic stents can relieve malignant obstruction
• Resection of limited liver or lung metastases may still be curative

Neoadjuvant (before surgery) therapy for locally advanced rectal cancer — chemoradiation and/or chemotherapy.

Adjuvant chemotherapy — standard for stage III (node-positive) colon cancer to destroy micrometastases and reduce recurrence; considered for high-risk stage II.

Listed by phase of care; within each phase, airway, breathing, and circulation come first.

1. Preoperative — for obstruction: NPO and NG decompression, IV fluids; otherwise bowel preparation and antibiotics as ordered; stoma site marking by a WOC nurse; teaching
2. Postoperative airway, breathing, and circulation — pain control, incentive spirometry, early ambulation, VTE prophylaxis; monitor for bleeding
3. Detect anastomotic leak and early complications
   • Fever, tachycardia, increasing abdominal pain, peritoneal signs, feculent drain output — report immediately
   • Postoperative ileus or early obstruction: distension, vomiting, pain, tachycardia and hypotension
   • Enterocutaneous fistula: bowel contents draining through the incision or skin (not the stoma) — protect the skin, contain and measure drainage with a pouch, report
4. Stoma assessment
   • Healthy stoma: beefy red or pink, moist, slightly raised; mild edema early
   • Pale, dusky, purple, or black = ischemia/necrosis — report immediately
   • Also watch for retraction, prolapse, bleeding, separation from the skin
   • Colostomy begins to function in about 2–5 days; ileostomy output starts within 24–48 hours and is liquid and high in volume
5. Fluid and electrolytes — ileostomy output can be large: monitor intake and output, dehydration, potassium, sodium, kidney function; report output of more than about 1.5–2 L per day
6. Perineal wound after APR — drainage, infection; side-lying position; pressure-relieving cushion; sitz baths once permitted
7. Body image and sexuality — encourage looking at and touching the stoma, participation in care, contact with ostomy support groups

Ostomy care

• Measure the stoma and cut the skin barrier opening about 1/16–1/8 in (about 1.5–3 mm) larger than the stoma; re-measure weekly for about 6–8 weeks as swelling decreases
• Empty the pouch when one-third to one-half full
• Change the skin barrier every 3–7 days or immediately if leaking or itching/burning under the wafer
• Clean peristomal skin with warm water only, dry completely; avoid oily soaps and lotions under the wafer
• Stoma output is irritating to skin (ileostomy output contains digestive enzymes) — a well-fitted barrier is essential
• Colostomy irrigation is an option only for some descending or sigmoid colostomies, never for ileostomies

Colostomy irrigation (if prescribed)

1. Irrigate at the same time each day; sit on or next to the toilet with the irrigation sleeve draining into it
2. Fill the irrigator with 500–1,000 mL of lukewarm tap water; hang the bag about 45–50 cm (18–20 in) above the stoma (about shoulder height when seated)
3. Lubricate the cone tip and insert it gently into the stoma — never force it
4. Instill slowly over about 5–10 minutes; if cramping occurs, slow or stop the flow until it passes
5. Allow about 30–45 minutes for return, then clean the skin and apply a small pouch or cap
6. Do not irrigate during diarrhea (e.g., from chemotherapy or radiation), with stoma prolapse, or with a parastomal hernia

Diet with a stoma

• Ileostomy: some enteric-coated or extended-release tablets may pass without being absorbed — tell pharmacists and prescribers
• Report stoma color change, persistent high output, no output with cramping and vomiting (blockage), or a bulge around the stoma (parastomal hernia)
• Avoid heavy lifting as instructed to reduce hernia risk

After sphincter-preserving rectal surgery — low anterior resection syndrome (frequency, urgency, clustering of stools, fecal incontinence) is common: pelvic floor exercises, diet adjustment, antidiarrheals; warm sitz baths for perianal soreness; gentle cleansing without harsh soap.

Prevention and follow-up — colonoscopy surveillance after resection, CEA and CT as scheduled; physical activity, fiber, less red/processed meat, no smoking, limited alcohol; first-degree relatives need earlier screening.

• Screening average risk: age 45–75 (USPSTF); FIT yearly or colonoscopy every 10 years; positive stool test → colonoscopy
• Most common symptom: change in bowel habits; right-sided → anemia; left-sided → obstruction and narrow stools
• CEA monitors treatment and recurrence — not a screening test
• Obstruction from CRC: NPO and NG decompression first
• Adjuvant chemotherapy in stage III: kill micrometastases, lower recurrence
• Oxaliplatin: avoid cold (neuropathy); bevacizumab: bleeding, perforation, poor wound healing
• Healthy stoma: red, moist; dusky or black → report
• Barrier opening about 1.5–3 mm larger than stoma; empty pouch at one-third to one-half full
• Odor: yogurt, buttermilk, parsley, cranberry juice; gas: avoid beans, cabbage, carbonated drinks, straws
• Ileostomy: increase fluids and chew well — dehydration and blockage risk
• Bowel contents through the incision (not the stoma) = fistula
• Sphincter-preserving surgery → incontinence and frequency (LARS); sitz baths for perianal soreness