Left-Sided Abdominal Pain: Causes and Management
Most Common Cause in Adults
Acute sigmoid or descending colonic diverticulitis is the most common cause of left-sided abdominal pain in adults, accounting for the majority of cases, though 10-25% of patients with diverticulosis will ultimately develop diverticulitis. 1
Differential Diagnosis
The differential for left-sided abdominal pain includes:
- Diverticulitis (most common in adults) 1, 2
- Inflammatory bowel disease (Crohn's disease, ulcerative colitis) 1, 2
- Primary epiploic appendagitis (benign, self-limited condition mimicking diverticulitis) 3, 4
- Renal colic/urolithiasis 4, 5
- Perforated colon cancer (can mimic diverticulitis radiographically) 1
- Urinary tract infection/pyelonephritis 4, 5
- Gynecologic disorders in women (ectopic pregnancy, pelvic inflammatory disease, adnexal torsion) 4, 5
- Abdominal wall pain 4, 6
- Colitis (infectious, ischemic) 2, 4
Diagnostic Approach
Clinical Assessment
Clinical diagnosis alone is unreliable with misdiagnosis rates of 34-68%, so imaging is essential for accurate diagnosis. 7
Key clinical features to assess:
- Location and character of pain: Focal left lower quadrant tenderness suggests diverticulitis (82.1% of cases) or epiploic appendagitis, while diffuse left-sided tenderness is more common with diverticulitis (52%) 3
- Fever: Present in 40% of diverticulitis cases but only 7.1% of epiploic appendagitis 3
- Rebound tenderness: Suggests peritonitis; present in 52% of diverticulitis vs 14.3% of epiploic appendagitis 3
- Red flag symptoms requiring immediate evaluation: Inability to pass gas/stool, signs of shock, bloody stools, progressively worsening pain, vomiting, or toxic appearance 7
Laboratory Testing
Obtain the following labs:
- Complete blood count: Leukocytosis present in 52% of diverticulitis vs 15.4% of epiploic appendagitis 3
- C-reactive protein: CRP >140-170 mg/L predicts severe diverticulitis with 87.5% sensitivity 1, 8
- Urinalysis: To exclude urinary tract infection or urolithiasis 5
- Pregnancy test: In women of reproductive age 5
Imaging Strategy
CT abdomen and pelvis with IV contrast is the gold standard imaging modality for left-sided abdominal pain, with 98-99% sensitivity and 99-100% specificity for diagnosing diverticulitis. 1, 7
- CT with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology 7
- Benefits: Detects complications (abscess, perforation, fistula), identifies alternative diagnoses, guides treatment decisions, and reduces hospital admissions by >50% 7
- Ultrasound: Preferred initial imaging for premenopausal women with suspected gynecologic pathology 7
- CT findings suggesting cancer rather than diverticulitis: Pericolonic lymphadenopathy >1 cm with or without pericolonic edema 1, 7
Management of Diverticulitis
Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)
For immunocompetent patients with uncomplicated diverticulitis, observation with supportive care WITHOUT antibiotics is the recommended first-line approach, as antibiotics neither accelerate recovery nor prevent complications or recurrence. 1, 9
Outpatient Management Criteria
Appropriate for patients who meet ALL of the following 1, 9:
- Able to tolerate oral fluids and medications
- No significant comorbidities or frailty
- Temperature <100.4°F
- Pain controlled with acetaminophen alone (pain score <4/10)
- Adequate home and social support
- No signs of systemic inflammatory response or sepsis
When to Use Antibiotics in Uncomplicated Diverticulitis
Reserve antibiotics for patients with specific high-risk features: 1, 9
- Immunocompromised status (chemotherapy, high-dose steroids, organ transplant)
- Age >80 years
- Pregnancy
- Persistent fever or chills despite supportive care
- Increasing leukocytosis (WBC >15 × 10⁹ cells/L)
- Elevated CRP (>140 mg/L)
- Refractory symptoms or vomiting
- Inability to maintain oral hydration
- CT findings: Fluid collection, longer segment of inflammation, or pericolic extraluminal air
- ASA score III or IV
- Symptoms lasting >5 days prior to presentation
Antibiotic Regimens for Uncomplicated Diverticulitis
Outpatient oral regimens (4-7 days for immunocompetent patients; 10-14 days for immunocompromised): 9
- First-line: Ciprofloxacin 500 mg twice daily PLUS metronidazole 500 mg three times daily
- Alternative: Amoxicillin-clavulanate 875/125 mg twice daily
Inpatient IV regimens (transition to oral as soon as tolerated): 9
- Ceftriaxone PLUS metronidazole
- Piperacillin-tazobactam
Complicated Diverticulitis (With Abscess, Perforation, or Fistula)
All patients with complicated diverticulitis require hospitalization, IV antibiotics, and surgical consultation. 1, 9
Treatment Algorithm Based on Abscess Size
- Small abscess (<4-5 cm): IV antibiotics alone for 7 days 1, 9
- Large abscess (≥4-5 cm): Percutaneous CT-guided drainage PLUS IV antibiotics for 4 days (in immunocompetent patients with adequate source control) 1, 9
- Generalized peritonitis or sepsis: Emergent surgical consultation for source control surgery (Hartmann's procedure or primary resection with anastomosis) 1, 9
Duration of Antibiotics in Complicated Diverticulitis
- 4 days after adequate source control in immunocompetent, non-critically ill patients 1, 9
- Up to 7 days in immunocompromised or critically ill patients 1, 9
Management of Inflammatory Bowel Disease (IBD)
For patients with known IBD presenting with left-sided abdominal pain:
- Evaluate for disease flare with imaging and laboratory markers (CRP, fecal calprotectin) 6
- Consider complications: Abscess, fistula, stricture, or perforation requiring imaging 1
- Medication-related triggers: Corticosteroid use increases risk of diverticulitis flares and complications, including perforation 9
- Treatment: Depends on disease severity and may include steroids, immunomodulators (azathioprine), or biologics 2
Important caveat: Postmarketing cases of hepatosplenic T-cell lymphoma (HSTCL), a rare and fatal T-cell lymphoma, have been reported in patients with Crohn's disease or ulcerative colitis treated with azathioprine, particularly in adolescent and young adult males 10
Follow-Up and Prevention
Colonoscopy Timing
Perform colonoscopy 4-6 weeks after resolution of symptoms in the following cases: 9, 7
- Complicated diverticulitis (7.9% risk of colon cancer)
- First episode of uncomplicated diverticulitis
- Patients >50 years requiring routine screening
- CT findings of abnormal pericolic lymph nodes or luminal mass
Routine colonoscopy after CT-confirmed uncomplicated diverticulitis is NOT warranted (only 1.16% risk of colorectal cancer, similar to asymptomatic screening population) 1, 9
Prevention of Recurrence
Lifestyle modifications to reduce recurrence risk: 9
- High-quality diet: High in fiber from fruits, vegetables, whole grains, legumes (>22.1 g/day); low in red meat and sweets
- Regular vigorous physical activity
- Achieve or maintain normal BMI (18-25 kg/m²)
- Smoking cessation
- Avoid nonaspirin NSAIDs when possible (aspirin is acceptable)
Do NOT restrict: Nuts, corn, popcorn, or small-seeded fruits—these are NOT associated with increased diverticulitis risk 9
Do NOT prescribe: Mesalamine or rifaximin for prevention—strong evidence shows no benefit and increased adverse events 9, 11
Surgical Considerations
Elective surgery should NOT be based on number of episodes alone, but rather on: 9
- Quality of life impact (persistent symptoms >3 months)
- Frequency of recurrence (≥3 episodes within 2 years)
- History of complicated diverticulitis
- Immunocompromised status
- Patient preferences and operative risks
Elective sigmoidectomy reduces recurrence (15% at 5 years with surgery vs 61% with conservative management) and significantly improves quality of life 9
Common Pitfalls to Avoid
- Do NOT routinely prescribe antibiotics for uncomplicated diverticulitis in immunocompetent patients without risk factors 1, 9
- Do NOT rely on clinical examination alone—imaging is essential due to 34-68% misdiagnosis rates 8, 7
- Do NOT assume all patients require hospitalization—most can be safely managed outpatient with appropriate follow-up (35-83% cost savings) 1, 9
- Do NOT unnecessarily restrict diet—restrictions on nuts, seeds, and popcorn are not evidence-based 9
- Do NOT delay surgical consultation in patients with frequent recurrences affecting quality of life 9
- Do NOT apply the "no antibiotics" approach to complicated diverticulitis (Hinchey 1b/2 or higher)—these patients always require antibiotics 9
- Do NOT stop antibiotics early if they are indicated, even if symptoms improve 9