What could be the cause of left lower quadrant pain in a 29-year-old male?

Left Lower Quadrant Pain in a 29-Year-Old Male

Order CT abdomen and pelvis with IV contrast immediately as the preferred diagnostic test, which has 98% diagnostic accuracy and will identify the cause while ruling out serious complications. 1, 2

Differential Diagnosis by Likelihood in This Age Group

The most common causes of left lower quadrant pain in a 29-year-old male include:

• Diverticulitis - Though less common at age 29 than in older patients, it remains a leading cause and presents with the classic triad of left lower quadrant pain, fever, and leukocytosis in only 25% of cases 1, 2
• Epiploic appendagitis - A self-limited condition caused by torsion or venous thrombosis of epiploic appendices that mimics diverticulitis but requires no treatment 3, 4
• Colitis (infectious, inflammatory bowel disease) - Common in younger patients and can present with similar pain patterns 5
• Urolithiasis - Left-sided kidney stones frequently cause left lower quadrant pain and should be excluded 5, 4
• Atypical appendicitis - In rare cases of midgut malrotation or situs inversus, acute appendicitis can present as left lower quadrant pain rather than right-sided pain 6, 7

Critical Clinical Assessment Before Imaging

Do not rely on clinical examination alone—misdiagnosis rates are 34-68% based on physical exam without imaging. 1, 2

Look specifically for these clinical features:

• Fever + leukocytosis - Suggests inflammatory or infectious process requiring urgent evaluation, though this triad is present in only 25% of diverticulitis cases 1, 2
• Inability to pass gas or stool - Present in 90% of large bowel obstructions and indicates potential surgical emergency 2
• Peritoneal signs (guarding, rebound tenderness, absent bowel sounds) - Indicates possible perforation requiring emergency surgical consultation 2
• Vomiting + severe pain - Increases concern for complicated pathology 2

Imaging Strategy

CT abdomen and pelvis with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology and should be the default imaging choice. 1, 2

Why CT with IV contrast is superior:

• Detects complications - Identifies abscess, perforation, fistula, and obstruction that alter management 1, 2
• Identifies alternative diagnoses - Changes diagnosis in nearly 50% of cases with nonlocalized abdominal pain 2
• Guides treatment decisions - Distinguishes uncomplicated from complicated disease, determining whether outpatient management, antibiotics, drainage, or surgery is needed 1, 2
• Reduces unnecessary hospitalizations - Early CT can reduce hospital admission by >50% and shorten length of stay 1

Alternative imaging considerations:

• Plain radiography is NOT useful - Limited diagnostic value and CT is far more sensitive and specific 1
• Ultrasound - Can reduce unnecessary CT examinations but is operator-dependent, limited by bowel gas and obesity, and less commonly used in the United States for nongynecologic left lower quadrant pain 1
• MRI - Not useful for initial evaluation due to longer acquisition time, lower sensitivity for free air and stones, and motion artifacts in symptomatic patients 1

Management 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 2
• Immunocompromised or elderly patients: Antibiotics for maximum 7 days (Ertapenem 1g q24h or Eravacycline 1mg/kg q12h) 2
• Outpatient management is appropriate for most uncomplicated cases 1, 2

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

• Antibiotics alone for 7 days without drainage 2
• No percutaneous drainage needed for small collections 2

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

• Percutaneous CT-guided drainage PLUS antibiotics for 4 days 2
• Stop antibiotics at 4 days if source control is adequate and patient is immunocompetent 2

Perforation with Diffuse Peritonitis:

• Emergency surgical consultation immediately for laparotomy with colonic resection 2, 8
• Start broad-spectrum IV antibiotics (carbapenem therapy if septic shock) 2, 8

Critical Pitfalls to Avoid

• Do not assume typical presentation - Only 25% of diverticulitis patients have the classic triad of left lower quadrant pain, fever, and leukocytosis 1, 2
• Do not skip imaging based on clinical impression - Clinical diagnosis alone has 34-68% misdiagnosis rates 1, 2
• Do not order routine colonoscopy after CT-confirmed uncomplicated diverticulitis - Only indicated for age-appropriate screening not yet performed, abnormal lymph nodes on CT, luminal mass, or presence of abscess/perforation/fistula 2
• Watch for cancer mimicking diverticulitis - Pericolonic lymphadenopathy >1 cm with or without pericolonic edema suggests malignancy rather than diverticulitis 2
• Consider atypical appendicitis - Though rare, midgut malrotation can cause left-sided appendicitis in young patients 6, 7

When to Send to Emergency Department Immediately

Direct the patient to the emergency department if any of these red flags are present:

• Fever with severe abdominal tenderness and guarding 2
• Inability to pass gas or stool with abdominal distension 2
• Signs of shock (hypotension, tachycardia, confusion) 2, 8
• Bloody stools 2
• Progressively worsening pain over several days 2
• Vomiting with inability to tolerate oral intake 2