What is the best course of action for a 79-year-old male patient with an infrarenal abdominal aortic aneurysm, perineal hernia, and elevated C-reactive protein (CRP) levels, who presented to the emergency department with abdominal symptoms and left before receiving full treatment?

Management of 79-Year-Old Male with Infrarenal AAA and Elevated Inflammatory Markers

This patient requires urgent outreach and clinical reassessment to exclude complicated diverticulitis or infectious proctitis, followed by conservative management of his infrarenal AAA with surveillance imaging in 6 months.

Immediate Priority: Address the Acute Inflammatory Process

The markedly elevated CRP of 235 mg/L in conjunction with CT findings of mesorectal fat stranding (suggesting proctitis) and sigmoid diverticulosis demands immediate attention, as this represents active intra-abdominal inflammation that requires treatment 1.

Clinical Assessment Required

• Contact the patient immediately to assess for ongoing symptoms including fever, abdominal pain, change in bowel habits, rectal bleeding, or signs of sepsis 1
• Rule out infectious causes, particularly Clostridium difficile and cytomegalovirus, through stool cultures and toxin testing 1
• Assess for peritonitis through telephone triage or urgent clinic visit, as physical examination findings of guarding or rebound tenderness would necessitate emergency department return 1

Management of Suspected Proctitis/Diverticulitis

If the patient has mild symptoms without peritonitis:

• Initiate broad-spectrum antibiotic therapy for 3-5 days targeting colonic flora 1
• In elderly patients with uncomplicated diverticulitis (WSES stage 0) who are immunocompetent and without organ dysfunction, antibiotics may be avoided; however, the elevated CRP of 235 mg/L and CT findings of mesorectal stranding suggest at least WSES stage 1a disease requiring antibiotic coverage 1
• Monitor CRP levels, as persistent elevation beyond 100 mg/L after 5-7 days suggests ongoing infection requiring further investigation 1

If the patient has severe symptoms or peritonitis:

• Immediate emergency department evaluation is mandatory 1
• CT imaging may need to be repeated if clinical deterioration occurs 1

Management of the Infrarenal Abdominal Aortic Aneurysm

Current AAA Status

The infrarenal AAA measuring 43 x 42 mm falls well below surgical intervention thresholds and requires surveillance rather than repair 1, 2.

Key measurements:

• Elective repair threshold: ≥55 mm in men 1, 2
• Current size: 43 mm (12 mm below intervention threshold)
• 1-year rupture risk: <1% for aneurysms of this size 2

Surveillance Protocol

Schedule ultrasound surveillance in 6 months (not 12 months) given the aneurysm diameter of 43 mm, which falls in the 3.5-4.4 cm range requiring annual surveillance, though some guidelines suggest 6-month intervals for aneurysms approaching 4.5 cm 2.

Indications for earlier intervention:

• Growth to ≥55 mm diameter 1, 2
• Rapid expansion ≥10 mm per year or ≥5 mm in 6 months 1, 2
• Development of symptoms (abdominal or back pain) 1
• Saccular morphology on repeat imaging 2

Pre-operative Planning (For Future Reference)

When this AAA eventually reaches surgical size, complete vascular evaluation with CT angiography will be mandatory to assess the entire aorta and determine EVAR feasibility 1, 3. Duplex ultrasound of the femoro-popliteal segment should be performed to detect concomitant aneurysms 1.

Critical Risk Factor Modification

Cardiovascular Risk Reduction

Initiate or optimize the following immediately:

• Smoking cessation (if applicable): This is the single most important modifiable risk factor for AAA expansion and rupture 2
• Blood pressure control: Hypertension accelerates aneurysm growth; target optimal BP control 2
• Statin therapy: Indicated for all patients with atherosclerotic aortic disease for cardiovascular risk reduction 2
• Screen for coronary artery disease: AAA patients have high prevalence of CAD, which is the leading cause of early mortality after AAA repair (5-10% perioperative CV complication rate) 1, 2

Relationship Between Elevated CRP and AAA

The CRP of 235 mg/L is likely primarily driven by the acute inflammatory process (proctitis/diverticulitis) rather than the AAA itself 4, 5. While CRP levels are elevated in AAA patients and correlate with aneurysm size, the magnitude of elevation in this case (235 mg/L) far exceeds what would be expected from a 43 mm AAA alone 4, 5, 6. Research shows median CRP levels of 2.6-3.5 mg/L in patients with small AAAs 5.

Important caveat: Once the acute inflammatory process resolves, repeat CRP measurement may be useful as a baseline marker, as elevated CRP correlates with larger aneurysm size and may serve as a disease marker 4, 5.

Perineal Hernia Consideration

The small fat-containing perineal hernia noted on CT is likely incidental and asymptomatic 7. However, document this finding for future reference, as perineal infections can rarely lead to infected AAAs with rapid expansion, though this is an extremely uncommon complication 7.

Follow-Up Algorithm

1. Within 24-48 hours: Contact patient to assess symptoms and initiate treatment for proctitis/diverticulitis if indicated
2. Within 1 week: Ensure infectious workup completed and antibiotic therapy initiated if appropriate
3. Within 2 weeks: Repeat CRP to confirm downtrending after treatment
4. Within 6 months: Ultrasound surveillance of AAA
5. Ongoing: Cardiovascular risk factor optimization and annual surveillance thereafter until AAA reaches 4.5 cm, then increase to 6-month intervals 2