3.5 Diverticular Disease & Colorectal Cancer Screening
Key Takeaways
- Colorectal cancer screening, colon polyposis and genetic colon cancer syndromes, diverticular disease and irritable bowel syndrome are enumerated under colonic and anorectal disease.
- Selected immunocompetent patients with mild uncomplicated diverticulitis can be managed without antibiotics, whereas complicated disease requires antibiotics and often drainage.
- A diverticular abscess above roughly 3 cm generally requires percutaneous drainage in addition to antibiotics.
- Colonoscopy should be performed after resolution of an episode of diverticulitis if the colon has not recently been evaluated, to exclude an underlying malignancy.
- Average-risk colorectal cancer screening begins at age 45, and a positive non-invasive stool test requires diagnostic colonoscopy rather than repeat stool testing.
Last updated: August 2026
1. Diverticular Disease
Diverticulosis vs. Acute Diverticulitis
- Diverticulosis: Outpouchings of colonic mucosa and submucosa herniating through the circular muscularis layer at points of nutrient vessel (vasa recta) penetration. Most prominent in the sigmoid colon due to high laplace intraluminal pressure. Diverticulosis is the most common cause of massive, painless lower gastrointestinal bleeding in older adults (arterial rupture of the vasa recta; stops spontaneously in ~80%).
- Acute Diverticulitis: Micro- or macroscopic perforation of a diverticulum resulting in localized pericolic inflammation, phlegmon, or abscess.
- Clinical Presentation: Constant left lower quadrant (LLQ) pain, low-grade fever, nausea, leukocytosis, and altered bowel habits (constipation or diarrhea).
- Diagnostic Modality of Choice: Abdominal and Pelvic CT with IV Contrast (demonstrates colonic wall thickening $>4\text{ mm}$, pericolic fat stranding, diverticula, phlegmon, or abscess).
- Absolute Contraindication: Colonoscopy and barium enema are strictly contraindicated during acute diverticulitis due to the high risk of converting a microperforation into a free macroscopic perforation.
Diverticulitis Management Staging (Hinchey Criteria)
| Classification | Clinical Findings | Evidence-Based Management Protocol |
|---|---|---|
| Uncomplicated Diverticulitis (Hinchey Stage Ia) | Localized colonic wall thickening and pericolic fat stranding without abscess or perforation. | In immunocompetent patients with mild symptoms, manage as outpatient with clear liquid diet with or without oral antibiotics (Amoxicillin-clavulanate 875/125 mg BID or Ciprofloxacin + Metronidazole). (2021 AGA guidelines support selective non-antibiotic management for mild uncomplicated cases). |
| Complicated: Small Abscess (Hinchey Stage Ib / II) | Pericolic or distant pelvic abscess $< 3-4\text{ cm}$. | Inpatient admission, IV fluids, bowel rest, and IV broad-spectrum antibiotics (e.g., Ceftriaxone + Metronidazole or Piperacillin-tazobactam). |
| Complicated: Large Abscess (Hinchey Stage Ib / II) | Pericolic or distant pelvic abscess $\ge 3-4\text{ cm}$. | Inpatient admission, IV antibiotics, and CT-guided Percutaneous Catheter Drainage. |
| Complicated: Peritonitis / Free Perforation (Hinchey Stage III / IV) | Purulent or feculent generalized peritonitis, free air under diaphragm, sepsis/shock. | Emergency Exploratory Laparotomy with Hartmann Procedure (sigmoid resection with end colostomy and rectal stump closure) or primary resection with anastomosis and diverting loop ileostomy. |
[!IMPORTANT] Post-Diverticulitis Colonoscopy Timing: In patients who have recovered from an episode of acute complicated diverticulitis (or uncomplicated diverticulitis without recent screening), a follow-up colonoscopy is mandatory at 6 to 8 weeks after complete resolution of acute symptoms to rule out an underlying colorectal adenocarcinoma masquerading as diverticulitis.
2. Colorectal Cancer (CRC) Screening Guidelines
USPSTF 2021 Average-Risk Screening Recommendations
- Ages 45 to 75 Years: Routine screening recommended for all average-risk adults (Grade A for ages 50–75; Grade B for ages 45–49).
- Ages 76 to 85 Years: Individualize screening decisions based on the patient's overall health, prior screening history, and life expectancy ($>10$ years).
- Age $>85$ Years: Routine screening is NOT recommended.
Screening Modalities & Intervals
- Colonoscopy: Every 10 years (gold standard: visualizes entire colon and allows simultaneous polypectomy).
- Annual Fecal Immunochemical Test (FIT): Every 1 year (detects human globin; no dietary restrictions).
- FIT-fecal DNA (Cologuard): Every 3 years (if positive, diagnostic colonoscopy is mandatory).
- Flexible Sigmoidoscopy: Every 5 years (or every 10 years if combined with annual FIT).
- CT Colonography (Virtual Colonoscopy): Every 5 years.
High-Risk Screening & Hereditary Syndromes
| Risk Category / Syndrome | Underlying Genetics / Criteria | Recommended Screening Initiation & Interval |
|---|---|---|
| Family History: 1st-Degree Relative <60yo OR $\ge 2$ 1st-Degree Relatives (any age) | Non-syndromic familial clustering. | Start colonoscopy at age 40 OR 10 years younger than the earliest diagnosed relative (whichever is earlier). Repeat every 5 years. |
| Family History: 1st-Degree Relative $\ge 60$yo | Non-syndromic. | Start colonoscopy at age 40; repeat every 10 years (or standard interval). |
| Lynch Syndrome (HNPCC) | Autosomal dominant; germline mutations in DNA Mismatch Repair (MMR) genes (MLH1, MSH2, MSH6, PMS2) or EPCAM; Microsatellite Instability-High (MSI-H).<br/>Amsterdam II Criteria (3-2-1): 3 relatives with Lynch-associated cancers, 2 successive generations, 1 diagnosed before age 50. | • Colonoscopy every 1 to 2 years starting at age 20 to 25 (or 2–5 years before earliest cancer in family).<br/>• Annual screening for Endometrial and Ovarian cancer (pelvic US/endometrial biopsy starting age 30–35; consider prophylactic hysterectomy/bilateral salpingo-oophorectomy after childbearing). |
| Familial Adenomatous Polyposis (FAP) | Autosomal dominant; germline mutation in APC tumor suppressor gene on chromosome 5q21. Development of thousands of adenomatous polyps; 100% CRC risk by age 40–50 if untreated. | • Annual Flexible Sigmoidoscopy or Colonoscopy starting at age 10 to 12.<br/>• Prophylactic Total Proctocolectomy with Ileal Pouch-Anal Anastomosis (IPAA) when polyps become confluent or high-grade dysplasia develops.<br/>• Upper endoscopy (EGD) surveillance starting at age 25 for duodenal/ampullary adenomas. |
Test Your Knowledge
A 52-year-old man presents to the emergency department with a 3-day history of worsening left lower quadrant abdominal pain, fever, and nausea. Contrast-enhanced CT of the abdomen and pelvis confirms acute sigmoid diverticulitis with a 4.5 cm rim-enhancing fluid collection (abscess) in the adjacent pelvis without free extraluminal gas. His temperature is 38.8°C (101.8°F), blood pressure is 126/78 mmHg, and WBC count is 16,200/mcL. In addition to intravenous fluid resuscitation and broad-spectrum IV antibiotics, what is the most appropriate next step in management?
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