What are the signs, symptoms, physical findings, and laboratory abnormalities of acute diverticulitis in an otherwise healthy adult?

Signs and Symptoms of Acute Diverticulitis

Clinical Presentation

Acute diverticulitis typically presents with left lower quadrant pain and tenderness, often accompanied by fever, but clinical examination alone is unreliable—achieving only a 65% positive predictive value—and imaging confirmation is mandatory in most cases. 1

Cardinal Symptoms

• Left lower quadrant pain is the hallmark symptom, present in the vast majority of patients with acute diverticulitis 2, 3
• Abdominal tenderness localized to the left lower quadrant on palpation is the most consistent physical finding 1, 2
• Fever occurs commonly but is not universal; approximately 5% of patients with severe diverticulitis present without fever 4
• Abdominal distention may be present, particularly in more severe cases 2, 3

Associated Symptoms

• Anorexia (loss of appetite) is frequently reported 2
• Nausea occurs in many patients, though the absence of vomiting is actually a positive diagnostic criterion 1, 4
• Constipation is common, though some patients experience diarrhea instead 2
• Dysuria (painful urination) may occur when inflammation involves the bladder wall 2
• Pelvic pressure pain may signal a pelvic abscess in complicated disease 4

Physical Examination Findings

• Localized tenderness in the left lower quadrant is the most reliable physical sign 1, 4
• Abdominal rigidity suggests peritoneal irritation and possible perforation 3
• Generalized abdominal tenderness indicates more severe, complicated disease requiring urgent imaging and possible surgical consultation 5
• Peritoneal signs (rebound tenderness, guarding) mandate immediate hospitalization and consideration of surgical intervention 2

Laboratory Abnormalities

White Blood Cell Count

• Leukocytosis (elevated WBC) is common but not universal 2, 6
• WBC > 15 × 10⁹ cells/L signals increased risk of complicated disease and should prompt hospitalization 7, 5
• Approximately 5% of patients with severe diverticulitis present with normal WBC counts, particularly in immunocompromised or elderly patients 4

C-Reactive Protein (CRP)

CRP is the single most important laboratory marker for risk stratification in acute diverticulitis. 7

• CRP > 50 mg/L is one component of the Laméris diagnostic criteria (97% positive predictive value when combined with left lower quadrant tenderness and absence of vomiting) 1, 4
• CRP 140–175 mg/L represents a threshold of increased risk for complicated diverticulitis 7, 5
• CRP > 173 mg/L predicts severe disease with 90.9% sensitivity and 90.9% specificity 7, 5
• CRP > 224 mg/L is strongly associated with complicated diverticulitis requiring intervention 7, 5

Critical Timing Consideration

CRP may remain normal during the first 6–8 hours of symptom onset and typically peaks at 48 hours; therefore, a normal CRP early in the disease course does not exclude acute diverticulitis or its complications. 7, 5

• Patients presenting within 6–8 hours of symptom onset can have severe complications (perforation, abscess) but still have normal inflammatory markers 5
• In high-risk patients (immunosuppressed, age > 80, symptoms > 5 days), CT imaging should be performed promptly without waiting for CRP to rise 7, 5

Other Laboratory Findings

• Basic metabolic panel should be obtained to assess renal function and electrolyte abnormalities 2, 3
• Urinalysis is recommended to exclude urinary tract infection as an alternative diagnosis 2, 3
• Neutrophil-to-lymphocyte ratio and serum glucose are associated with severe disease but are not independent predictors 7

Clinical Decision Rules

Laméris Criteria (97% Positive Predictive Value)

When all three of the following criteria are present, acute diverticulitis can be diagnosed with 97% accuracy: 1, 4

1. Direct tenderness only in the left lower quadrant
2. CRP > 50 mg/L
3. Absence of vomiting

However, this combination is present in only approximately 24% of patients with suspected diverticulitis 4

Red Flags Requiring Immediate Imaging and Hospitalization

• Symptoms lasting > 5 days 4, 5
• Pain score ≥ 8 on visual analog scale 4
• Presence of vomiting 4
• CRP > 140 mg/L 4, 7
• WBC > 15 × 10⁹ cells/L 7
• Age > 80 years 7
• Immunosuppression (even with completely normal markers) 5
• Inability to tolerate oral fluids 5
• Generalized abdominal tenderness 5

Common Diagnostic Pitfalls

• Clinical examination alone misdiagnoses diverticulitis in 34–68% of patients; imaging is essential for accurate diagnosis 4
• Normal inflammatory markers do not rule out complicated disease, especially in immunocompromised, elderly patients, or those presenting within the first 6–8 hours 7, 5
• Pericolonic lymphadenopathy > 1 cm on CT should raise suspicion for colonic carcinoma masquerading as diverticulitis 4