Acquired colonic outpouchings; inflammation produces left lower quadrant pain and fever.
Also known as: diverticulitis, diverticulosis, diverticular disease, acute diverticulitis
Overview
Diverticulosis: presence of acquired sac-like protrusions (false diverticula — lacking the muscular layer) of the colonic wall. Diverticulitis: inflammation or infection of one or more diverticula, classified as uncomplicated or complicated (abscess, fistula, obstruction, perforation).
Epidemiology
Diverticulosis prevalence rises with age: ~5% at age 40, ~30% at 60, >65% by age 85. Sigmoid colon is the most common site in Western countries (95% of cases). Right-sided diverticulosis more common in Asia. ~4% of patients with diverticulosis develop diverticulitis.
🔒 Free preview limit reached
Keep reading — start your free trial
You've read your 2 free diagnosis previews. Create your free account to unlock the full Diverticulitis and Diverticulosis outline — plus all 514 diagnoses, 3,500+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.
NSAID use (increases risk of diverticular bleed and perforation)
Sedentary lifestyle
Genetic susceptibility
Connective tissue disease (Ehlers-Danlos, Marfan — early onset)
Pathophysiology
Increased intraluminal pressure (low-fiber diet → smaller stool → segmental contraction with high pressures) drives mucosal/submucosal herniation through weak points in the muscularis where vasa recta penetrate (vasa recta erosion → diverticular bleed). Diverticulitis: micro-perforation of an obstructed diverticulum → pericolonic inflammation, potentially with abscess or free perforation.
Clinical presentation
Symptoms
Diverticulosis: usually asymptomatic; incidental on colonoscopy or imaging
Diverticular bleed: painless, brisk hematochezia (most common cause of LGIB)
Diverticulitis: left lower quadrant pain (sigmoid), constant, often worsening over 1-3 days
Fever, chills, anorexia
Change in bowel habit (constipation or diarrhea)
Nausea, vomiting (if obstruction)
Urinary symptoms (pneumaturia, fecaluria, recurrent UTI — colovesical fistula)
Signs / physical exam
LLQ tenderness ± palpable mass (phlegmon or abscess)
Low-grade fever, tachycardia
Localized peritoneal signs
Diffuse peritonitis if free perforation (Hinchey III/IV)
Rectal exam may reveal tender mass anteriorly (Douglas pouch abscess)
Classic findings
Older adult with LLQ pain, fever, and leukocytosis — 'left-sided appendicitis.'
Differential diagnosis
Acute appendicitis (especially with redundant sigmoid in LLQ or cecal diverticulitis) — Periumbilical pain migrating to RLQ; right-sided diverticulitis in Asian patients mimics this
Colorectal cancer — Older patient, weight loss, anemia, change in bowel habit; colonoscopy 6-8 wk after diverticulitis recovery
Gynecologic: ovarian torsion, PID, ectopic pregnancy — Pelvic exam, pregnancy test, pelvic ultrasound in women
Epiploic appendagitis — Localized LLQ pain, characteristic small fat-density CT lesion adjacent to colon; self-limited
Diagnostic workup
Diagnostic criteria
CT-confirmed pericolonic inflammation with diverticula. Modified Hinchey classification: Ia (pericolic phlegmon), Ib (pericolic abscess <4 cm), II (pelvic/intra-abdominal abscess), III (purulent peritonitis), IV (feculent peritonitis).
Labs
CBC (leukocytosis with left shift)
BMP, lactate (if severe)
CRP — predicts severity
Urinalysis (exclude UTI, identify fistula)
Urine pregnancy test in women of childbearing age
Blood cultures if septic
Imaging
CT abdomen/pelvis with IV contrast — MODALITY OF CHOICE; identifies pericolic inflammation, bowel wall thickening, abscess, fistula, free air; classifies by Hinchey stage
AVOID colonoscopy during acute diverticulitis (perforation risk); perform 6-8 weeks AFTER resolution to exclude malignancy when first episode or alarm features
Ultrasound or MRI in pregnancy or young patients to limit radiation
Diagnostic algorithm
Hinchey Stage
CT Finding
Management
Ia
Pericolic phlegmon, no abscess
Antibiotics ± observation; usually outpatient
Ib
Pericolic abscess <4 cm
IV antibiotics ± percutaneous drainage if ≥3-4 cm
II
Pelvic or intra-abdominal abscess
Percutaneous drainage + IV antibiotics
III
Purulent peritonitis
Emergent surgery (Hartmann or resection + anastomosis with diversion)
IV
Feculent peritonitis
Emergent surgery
Modified Hinchey classification of acute diverticulitis and stage-directed management.
Treatment
First-line
Uncomplicated diverticulitis (Hinchey Ia, mild Ib without significant abscess): often managed as outpatient; bowel rest as tolerated; antibiotics selective rather than universal per AGA 2015 (consider in elderly, immunocompromised, comorbidities, severe symptoms)
Outpatient antibiotic regimens: amoxicillin-clavulanate, or ciprofloxacin/levofloxacin + metronidazole × 7-10 days
Clear liquid diet advanced as tolerated
Follow-up in 2-3 days
Inpatient — moderate diverticulitis
Admit if unable to tolerate PO, significant comorbidities, immunocompromise, failed outpatient management, abscess, or peritoneal signs
IV antibiotics: piperacillin-tazobactam, ceftriaxone + metronidazole, or ertapenem
Bowel rest, IV fluids, analgesia (avoid NSAIDs)
Transition to oral antibiotics with clinical improvement
Abscess (Hinchey Ib-II)
Abscess <3-4 cm: IV antibiotics alone
Abscess ≥3-4 cm: percutaneous (image-guided) drainage + IV antibiotics
Surgery if failure of drainage or clinical deterioration
Perforation with peritonitis (Hinchey III/IV)
Emergent surgery — Hartmann procedure (sigmoid resection with end colostomy) or primary anastomosis with diverting ileostomy
Laparoscopic lavage controversial; not preferred over resection
Broad-spectrum IV antibiotics
Recurrent or complicated disease
Elective sigmoid resection — individualized; consider after recurrent episodes (no longer routine after 2nd episode), persistent symptoms, complicated disease (fistula, stricture), immunocompromise
AGA 2020 recommends shared decision-making rather than number-of-episodes rule
Diverticular bleed
Resuscitate; most stop spontaneously (75%)
Colonoscopy with hemostasis (clip, epinephrine, thermal) for active bleeding source
CT angiography or tagged RBC scan if hemodynamically stable but ongoing bleeding
IR angiographic embolization for refractory or massive bleed
Surgery for failed embolization and persistent hemodynamic instability
Complications
Abscess (intra-abdominal, pelvic)
Fistula — colovesical (most common, M:F due to uterus barrier), colovaginal, coloenteric, colocutaneous
Stricture and partial obstruction
Free perforation with peritonitis
Diverticular hemorrhage — most common cause of brisk lower GI bleeding
Recurrence (15-30% within 5 yr after first episode)
PANCE pearls
AVOID colonoscopy during acute diverticulitis — perforation risk. Schedule 6-8 weeks after resolution to exclude underlying malignancy (especially first episode or complicated disease).
Antibiotics are no longer routine for uncomplicated diverticulitis in healthy patients (AGA 2015) — observation with close follow-up is acceptable.
Pneumaturia, fecaluria, or recurrent polymicrobial UTI in older adult = colovesical fistula until proven otherwise.
Right-sided diverticulitis is more common in Asian populations and frequently misdiagnosed as appendicitis.
Old teaching to avoid nuts, seeds, and popcorn has NO evidence supporting it (Strate, JAMA 2008).
Elective surgery decision is individualized — not by episode count. Consider in young immunocompromised patients, persistent symptoms, complicated disease.
Smoldering/chronic diverticulitis (low-grade inflammation without abscess) may benefit from elective resection.
References
AGA 2015 — Stollman N et al. AGA Institute Guideline on the Management of Acute Diverticulitis. Gastroenterology 2015;149:1944-1949
ASCRS 2020 — Hall J et al. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Treatment of Left-Sided Colonic Diverticulitis. Dis Colon Rectum 2020;63:728-747
Strate Nuts/Seeds — Strate LL et al. Nut, Corn, and Popcorn Consumption and the Incidence of Diverticular Disease. JAMA 2008;300:907-914
Practice Gastrointestinal questions on FirstPassPA
Turn this outline into retention. 3,500+ board-style questions with an AI tutor that explains every answer — free to start, no card required.
Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants.