How should sharp left lower quadrant pain in an adult be evaluated and managed?

Evaluation and Management of Sharp Left Lower Quadrant Pain in Adults

Immediate Diagnostic Approach

Order CT abdomen and pelvis with IV contrast immediately—this is the mandatory first-line test with 98% diagnostic accuracy, rated 8/9 by the American College of Radiology. 1 Clinical examination alone misdiagnoses 34-68% of cases, making imaging essential rather than optional. 1

Critical Pre-Imaging Steps

• Obtain β-hCG in all women of reproductive age before CT to exclude pregnancy and avoid fetal radiation exposure. 1, 2
• Order initial laboratory panel: Complete blood count with differential, C-reactive protein, and urinalysis. 2
• Add lactate and blood cultures if the patient appears systemically ill or has fever. 2

When to Skip Imaging (Rare Exception)

In patients with known diverticulosis presenting with mild, intermittent pain, imaging may be deferred only if all of the following are present: 1

• No fever (temperature normal)
• No peritoneal signs (no guarding, rebound, or rigidity)
• No vomiting
• Able to tolerate oral intake
• Normal bowel movements continuing

However, order CT immediately if any red flag develops: fever, severe or worsening pain, inability to pass gas/stool, vomiting, peritoneal signs, or symptoms persisting beyond 2-3 days. 1

Differential Diagnosis Framework

Most Common Cause

Acute sigmoid diverticulitis is the leading etiology in adults >50 years, affecting ~70% of older adults with diverticulosis, of whom 5-25% develop diverticulitis. 1

Critical "Cannot Miss" Diagnosis

Perforated colon cancer mimics diverticulitis clinically and radiographically. 1 Look for these CT features that favor malignancy:

• Pericolonic lymphadenopathy >1 cm in short axis (with or without pericolonic edema) 1
• Luminal mass 1
• Isolated inflammatory changes at the sigmoid mesenteric root without lymphadenopathy favor diverticulitis 1

Other Important Differentials Identified on CT

• Large bowel obstruction: Dilated proximal bowel loops; fever + leukocytosis suggest complicated obstruction with ischemia 1
• Epiploic appendagitis: Pericolic fatty mass with hyperattenuated rim 1
• Inflammatory bowel disease: Skip lesions or multi-segment bowel wall thickening 1
• Pyelonephritis/nephrolithiasis: Perinephric fat stranding, hydronephrosis, or calculi 1
• Gynecologic pathology (premenopausal women): Consider pelvic/transvaginal ultrasound first if high suspicion for ovarian torsion, ruptured cyst, tubo-ovarian abscess, or ectopic pregnancy 1

Laboratory Interpretation for Risk Stratification

High-Risk Indicators

• CRP >170 mg/L: Predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity 2
• Left shift ≥75% neutrophils: Suggests bacterial infection 2
• Elevated lactate: Signals sepsis and metabolic derangement requiring aggressive resuscitation 2

Diagnostic Triad (Low Sensitivity)

The classic triad of left lower quadrant pain + fever + leukocytosis occurs in only 25% of diverticulitis cases. 1, 2 When combined with CRP >50 mg/L, left lower quadrant tenderness, and absence of vomiting, diagnostic accuracy reaches 97%—but this combination is present in only 24% of patients. 2

Critical pitfall: 39% of patients with complicated diverticulitis have CRP <175 mg/L, so normal inflammatory markers do not exclude serious disease. 2

Treatment Algorithm Based on CT Findings

Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)

For immunocompetent patients: Conservative management WITHOUT antibiotics is the standard recommendation. 1 Antibiotics do not improve outcomes and promote resistance. 1

• Clear liquid diet with advancement as tolerated 1
• Oral analgesics for pain control 1
• Outpatient management if able to tolerate oral intake 1

For immunocompromised or elderly patients only: Antibiotics for maximum 7 days 1

• Ertapenem 1 g q24h OR Eravacycline 1 mg/kg q12h 1

Complicated Diverticulitis with Small Abscess (<3-4 cm)

Antibiotics alone for 7 days without drainage. 1

• Same regimens as above (Ertapenem or Eravacycline) 1

Complicated Diverticulitis with Large Abscess (≥3-4 cm)

Percutaneous drainage PLUS antibiotics for 4 days in immunocompetent, non-critically ill patients. 1

• Stop antibiotics at 4 days if source control is adequate 1
• Continue up to 7 days in immunocompromised or critically ill patients, guided by clinical response 1
• If symptoms persist beyond 7 days, obtain repeat imaging to assess for inadequate source control 1

Septic Shock

Escalate immediately to broad-spectrum carbapenem therapy: 1

• Meropenem 1 g q6h by extended infusion, OR
• Doripenem 500 mg q8h by extended infusion, OR
• Imipenem/cilastatin 500 mg q6h by extended infusion 1

Perforation with Diffuse Peritonitis or Free Air

Emergency surgical consultation required. 1 Options include:

• Primary resection and anastomosis ± diverting stoma (clinically stable patients without major comorbidities) 1
• Hartmann's procedure (critically ill or multiple major comorbidities) 1

Red Flags Requiring Emergency Department Evaluation

Send immediately to the ED if any of the following are present: 1

• Fever
• Inability to pass gas or stool (present in 90% of large bowel obstructions) 1
• Severe abdominal tenderness with guarding, rebound, or rigidity (peritonitis)
• Vomiting
• Bloody stools
• Signs of shock (tachycardia, hypotension, confusion)
• Progressively worsening pain over several days

Colonoscopy Timing (Critical Stewardship)

Routine colonoscopy after CT-confirmed uncomplicated diverticulitis is NOT warranted except in these specific situations: 1

• Age-appropriate colon cancer screening not yet performed
• Abnormal pericolonic lymph nodes >1 cm on CT
• Luminal colon mass on CT
• Uncertain diagnosis
• Presence of abscess, perforation, or fistula

Common pitfall: Do not reflexively order colonoscopy after every diverticulitis episode—this wastes resources and exposes patients to unnecessary procedural risk. 1

Special Population Considerations

Premenopausal Women

• Order pelvic/transvaginal ultrasound as initial imaging if gynecologic pathology is suspected (cyclical pain, adnexal tenderness). 1
• CT remains appropriate if ultrasound is negative or non-gynecologic cause is more likely. 1

Pregnant Patients

• Avoid CT; use ultrasonography and MRI instead to prevent fetal radiation exposure. 1
• Pregnancy is a high-risk feature warranting antibiotic initiation even for mild disease. 1

Elderly Patients (>50 Years)

• Diverticulitis prevalence increases dramatically with age (~70% have diverticulosis). 1
• Higher threshold for antibiotics in this population even with uncomplicated disease. 1

Recurrent or Chronic Left Lower Quadrant Pain

If structural pathology has been excluded by CT and colonoscopy, consider: 3

• Functional bowel disorders (irritable bowel syndrome): Pain related to bowel movements or dietary triggers 3
• Gynecologic causes in premenopausal women: Cyclical pain suggests need for pelvic ultrasound if not already done 3
• MRI abdomen/pelvis if CT was equivocal (sensitivity 86-94%, specificity 88-92% for inflammatory conditions) 3

Repeat imaging is generally not indicated unless new symptoms develop or significant time has passed. 3

Refer to gastroenterology for functional bowel disorder management or persistent symptoms despite conservative measures. 3

Red flags warranting repeat workup: Weight loss, anemia, change in bowel habits, or new pericolonic lymphadenopathy >1 cm on imaging—these suggest malignancy and warrant repeat colonoscopy. 3

Key Clinical Pitfalls to Avoid

1. Do not rely on clinical examination alone—misdiagnosis rates are 34-68% without imaging. 1
2. Do not assume diverticulitis based solely on history of diverticulosis—always exclude colon cancer. 1
3. Do not prescribe antibiotics empirically for uncomplicated diverticulitis in immunocompetent patients—this increases resistance without benefit. 1
4. Do not order routine colonoscopy after uncomplicated diverticulitis—reserve for specific indications only. 1
5. Do not continue antibiotics beyond 7 days in uncomplicated cases—this increases resistance without improving outcomes. 1