What are the possible causes and treatments of left mid quadrant abdominal pain?

Left Mid Quadrant Abdominal Pain: Causes and Management

Most Common Causes

Acute colonic diverticulitis of the sigmoid or descending colon is the most common cause of left-sided abdominal pain in adults, with prevalence rising 50% between 2000-2007. 1

The differential diagnosis for left mid quadrant pain includes:

• Gastrointestinal causes: Diverticulitis (most common), colitis, inflammatory bowel disease, epiploic appendagitis, bowel obstruction, fecal impaction, perforated colon cancer 1, 2
• Urologic causes: Pyelonephritis, urolithiasis (kidney stones) 1
• Gynecologic causes (in women): Ovarian pathology, fallopian tube disease 1
• Body wall causes: Hernia, rectus sheath hematoma 1, 2
• Rare but critical: Atypical appendicitis with long appendix projecting leftward, or situs inversus with left-sided appendicitis 3, 4

Immediate Diagnostic Approach

Order CT abdomen and pelvis with IV contrast immediately—this is the single most accurate test with 98% diagnostic accuracy and is rated 8/9 (usually appropriate) by the American College of Radiology. 5

Why CT with IV contrast is essential:

• Detects complications (abscess, perforation, fistula) that determine whether you admit or send home 1, 5
• Identifies alternative diagnoses in 49% of cases, preventing misdiagnosis 5, 6
• Clinical examination alone has 34-68% misdiagnosis rates 5
• Reduces hospital admissions by >50% through accurate risk stratification 5
• IV contrast improves detection of bowel wall pathology, pericolic abnormalities, vascular pathology, and fluid collections 1

Special population modifications:

• Premenopausal women with suspected gynecologic pathology: Start with pelvic/transvaginal ultrasound before CT 5
• Suspected kidney stones: Unenhanced CT is acceptable and has near 100% sensitivity/specificity for urolithiasis 1
• Elderly patients (≥75 years): Unenhanced CT has similar accuracy to contrast-enhanced CT (64-68% vs 68-71%), but contrast is still preferred when feasible 1

Critical Red Flags Requiring Emergency Evaluation

Immediately send to emergency department if ANY of the following are present:

• Fever + left-sided pain + elevated WBC (classic triad, though only present in 25% of diverticulitis cases) 5
• Peritoneal signs: Rebound tenderness, guarding, rigid abdomen 5
• Complete inability to pass gas or stool (present in 90% of large bowel obstructions) 5
• Hemodynamic instability: Hypotension, tachycardia, signs of shock 7
• Bloody stools or vomiting 5
• Progressively worsening pain over several days 5

Treatment Algorithm Based on CT Findings

Uncomplicated Diverticulitis (no abscess, perforation, or fistula):

• Immunocompetent patients: Conservative management WITHOUT antibiotics—clear liquid diet advancement and oral analgesics only 5
• Immunocompromised or elderly patients: Antibiotics for maximum 7 days (Ertapenem 1g q24h or Eravacycline 1mg/kg q12h) 5
• Outpatient management is appropriate if patient can tolerate oral intake 5

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

• Antibiotics alone for 7 days without drainage 5
• Use Ertapenem 1g q24h or Eravacycline 1mg/kg q12h 5

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

• Percutaneous CT-guided drainage PLUS antibiotics for 4 days 5
• Stop antibiotics at 4 days if source control is adequate in immunocompetent patients 5
• Continue up to 7 days in immunocompromised or critically ill patients 5

Perforation with Peritonitis:

• Emergency surgical consultation for laparotomy with colonic resection 5, 7
• Start broad-spectrum carbapenem therapy immediately (Meropenem 1g q6h, Doripenem 500mg q8h, or Imipenem/cilastatin 500mg q6h by extended infusion) 5

Critical Pitfalls to Avoid

• Do NOT rely on clinical examination alone—the classic triad of left lower quadrant pain, fever, and leukocytosis is only present in 25% of diverticulitis cases 5
• Do NOT order routine colonoscopy after CT-confirmed uncomplicated diverticulitis—only indicated for age-appropriate screening not yet done, abnormal lymph nodes >1cm on CT, luminal mass on CT, or presence of abscess/perforation/fistula 5
• Do NOT continue antibiotics beyond 7 days in uncomplicated cases—this increases antibiotic resistance without improving outcomes 5
• Do NOT dismiss atypical presentations in elderly patients—only 50% have lower quadrant pain and only 17% have fever, yet mortality is 17.8% in patients >80 years old 7
• Consider atypical appendicitis—a long inflamed appendix can project into the left lower quadrant, or patient may have situs inversus with left-sided appendicitis 3, 4

When to Obtain Additional Laboratory Studies

• C-reactive protein (CRP): >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity 5
• Lactate level: Elevated lactate indicates sepsis and systemic infection 5
• Blood cultures: Obtain before starting antibiotics if sepsis suspected 7
• When all three criteria present (left lower quadrant tenderness + CRP >50 mg/L + absence of vomiting): 97% accuracy for diverticulitis, but this only occurs in 24% of patients 5

Monitoring and Follow-up

• Repeat imaging if: Fever and leukocytosis persist beyond 48-72 hours despite appropriate treatment, or clinical deterioration occurs 7
• Outpatient management requires: Ability to tolerate oral intake, normal or near-normal bowel movements, no peritoneal signs, and reliable follow-up 5