What is the diagnosis and treatment for a patient with a CT scan showing segmental thickening and enhancement of the colonic wall with air-filled pouches in the surrounding segments?

Diagnosis: Acute Colonic Diverticulitis

The CT findings of segmental colonic wall thickening and enhancement with air-filled pouches (diverticula) in the surrounding segments are diagnostic of acute diverticulitis, with CT demonstrating sensitivity and specificity as high as 100%. 1

Understanding the CT Findings

The imaging features described represent the classic radiographic presentation of diverticulitis:

• Segmental wall thickening is one of the three most common CT findings in acute diverticulitis, typically involving the descending and sigmoid colon 1
• Air-filled pouches represent the diverticula themselves, which are outpouchings of the colonic wall 2
• Enhancement of the colonic wall indicates active inflammation 3
• Additional findings that may be present include pericolonic fat stranding and increased density of pericolic fat 2

Classification and Severity Assessment

Using the WSES (World Society of Emergency Surgery) CT-guided classification system, diverticulitis is categorized as:

Uncomplicated Diverticulitis (Stage 0)

• Diverticula present with wall thickening and increased density of pericolic fat 2
• Infection limited to the colon without peritoneal extension 2

Complicated Diverticulitis (Stages 1A-2B)

The presence of additional features determines staging:

• Stage 1A: Pericolic air bubbles or small fluid within 5 cm of inflamed segment 2
• Stage 1B: Abscess ≤ 4 cm 2
• Stage 2A: Abscess > 4 cm 2
• Stage 2B: Distant gas (> 5 cm from inflamed segment) 2
• Stage 3: Diffuse fluid without distant free gas 2
• Stage 4: Diffuse fluid with distant free gas 2

Diagnostic Approach

Complete assessment should include clinical history, physical examination signs, laboratory inflammatory markers (CRP, WBC), and radiological findings—not CT alone. 2

Clinical Correlation

• Left lower quadrant pain with tenderness is the most common presenting symptom 1
• Elevated white blood cell count supports the inflammatory process 1
• Clinical diagnosis alone has poor accuracy (positive predictive value 0.65), while CT improves this to 0.95 2

Red Flags for Complicated Disease

Look for signs requiring aggressive intervention: 1

• Fever
• Inability to pass gas or stool
• Severe tenderness with guarding
• Vomiting
• Signs of shock

Management Based on Classification

Uncomplicated Diverticulitis

• Can typically be managed medically 1
• Antibiotics are commonly used as first-line treatment (42.7% of cases) 4
• Mesalamine is another option (36.0% of cases) 4

Complicated Diverticulitis

Treatment escalates based on severity:

• Small abscess (< 4-6 cm): Medical management with antibiotics 2
• Large abscess (≥ 3-4 cm): Consider percutaneous catheter drainage 3, 5
• Free perforation/peritonitis: Requires surgical intervention 3, 5
• Surgical intervention: Required in approximately 26.7% of SCAD cases 4

Antibiotic Selection

Metronidazole IV is indicated for serious intra-abdominal infections caused by susceptible anaerobic bacteria, including Bacteroides fragilis and Clostridium species, which are common in diverticulitis 6

Critical Follow-Up

Colonoscopy must be performed 6-8 weeks after resolution of acute symptoms to exclude underlying malignancy. 1, 7 This is essential because:

• Colonic carcinoma can mimic diverticulitis on imaging 8, 9
• Inflamed diverticula and preserved wall enhancement pattern help distinguish diverticulitis from cancer (sensitivity 86.8-89.5%, specificity 92.9-95.3%) 9

Common Pitfalls to Avoid

• Do not rely on clinical examination alone for diagnosis—imaging is essential for accuracy 2
• Do not skip follow-up colonoscopy—malignancy must be excluded 1, 7
• Consider right-sided diverticulitis in patients with right lower quadrant pain, especially post-appendectomy 10
• Recognize that isolated sigmoid inflammation (86.7% of cases) is the most common endoscopic finding 4
• Be aware that penetrating disease can occur in 13.7% of cases and is not specific to any particular diagnosis 4