In an 85‑year‑old patient with acute periumbilical pain radiating to the left lower quadrant, rigors, no fever, and a mild positive urine dipstick for blood, what is the appropriate immediate work‑up and management?

Immediate Work-Up and Management for 85-Year-Old with Periumbilical Pain Radiating to Left Lower Quadrant and Rigors

Immediate Actions Required

This 85-year-old patient with rigors and acute abdominal pain requires emergent CT abdomen and pelvis with IV contrast and immediate broad-spectrum antibiotics—rigors signal systemic inflammation and mandate aggressive evaluation even without documented fever, as elderly patients frequently present with blunted inflammatory responses and atypical symptoms. 1

Critical Pre-Imaging Steps

• Establish IV access immediately and begin crystalloid resuscitation to maintain systolic blood pressure >90 mmHg if any signs of hemodynamic instability are present 2
• Obtain blood cultures before antibiotics, then start empiric broad-spectrum IV antibiotics (carbapenem therapy such as ertapenem 1 g q24h or meropenem 1 g q6h if septic shock is suspected) without delay 2, 3
• Keep patient NPO pending imaging results and surgical evaluation 1
• Draw stat labs: complete blood count with differential, C-reactive protein (CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity), lactate level, and basic metabolic panel 2, 3
• Obtain immediate surgical consultation given the high-risk presentation—rigors indicate systemic inflammatory response and raise concern for intra-abdominal sepsis, abscess, or perforation 1, 2

Diagnostic Imaging Strategy

Order emergent CT abdomen and pelvis with IV contrast as soon as the patient is hemodynamically stable enough for transport—this is the mandatory first-line test with 98-99% diagnostic accuracy. 1, 3, 2

Why CT is Essential in This Case

• Clinical examination alone misdiagnoses 34-68% of cases in elderly patients, and the classic triad of left lower quadrant pain, fever, and leukocytosis occurs in only ~25% of diverticulitis cases 1, 3
• Only 50% of patients >65 years with acute left colonic diverticulitis have pain in the lower quadrants, and only 17% have documented fever despite serious infection 2
• Normal laboratory markers do not exclude serious intra-abdominal infection in older adults; imaging is essential rather than optional 1
• CT identifies alternative diagnoses in up to 49% of cases and changes management decisions in 51% of patients with atypical presentations 1

Modalities to Avoid

• Do not order plain radiography—it has extremely limited diagnostic value and will only delay definitive diagnosis 4, 1, 3
• Do not order ultrasound as the primary study—it is operator-dependent, limited by bowel gas and body habitus, and cannot reliably visualize the colon, mesentery, or retroperitoneum 4, 1, 3

Differential Diagnosis Prioritized by Urgency

Life-Threatening Conditions to Rule Out

Condition	Key CT Findings	Immediate Management
Perforated viscus (colon cancer, diverticulitis)	Free intraperitoneal air, localized fluid collections	Emergency surgery—laparotomy with resection [1,2]
Mesenteric ischemia	Vascular occlusion, bowel wall hypo-enhancement, pneumatosis	Emergency vascular surgery for revascularization; mortality 60-80% if delayed [1]
Complicated diverticulitis with large abscess	Inflamed sigmoid ± abscess ≥3-4 cm, extraluminal air	Percutaneous drainage + IV antibiotics × 4 days [1,3,2]
Bowel obstruction	Dilated loops with transition point, air-fluid levels	Nasogastric decompression + surgical evaluation [1]

Additional Considerations

• Perforated colon cancer can mimic diverticulitis—look for pericolonic lymphadenopathy >1 cm on CT, which favors malignancy 3
• Pyelonephritis or nephrolithiasis may present with left lower quadrant pain—CT will show perinephric fat stranding, hydronephrosis, or calculi 3
• The mild hematuria on dipstick may represent urinary tract involvement from a colovesical fistula (complication of diverticulitis), renal pathology, or simply incidental finding 4

Management Algorithm Based on CT Results

If Perforation with Diffuse Peritonitis

• Emergency surgical consultation for immediate laparotomy with colonic resection (Hartmann's procedure in critically ill elderly patients) 1, 2

If Large Abscess (≥3-4 cm) Without Free Perforation

• Percutaneous CT-guided drainage PLUS IV antibiotics × 4 days (ertapenem 1 g q24h or meropenem if septic shock) 1, 3, 2
• Continue antibiotics up to 7 days if immunocompromised or critically ill 3

If Small Abscess (<3-4 cm)

• IV antibiotics alone × 7 days without drainage 3, 2

If Uncomplicated Diverticulitis

• In this 85-year-old with rigors, antibiotics ARE indicated (ertapenem 1 g q24h × 7 days maximum) even if imaging shows uncomplicated disease—elderly and immunocompromised patients require antibiotic therapy 3, 2

If Bowel Obstruction

• Nasogastric decompression + surgical assessment for operative vs. conservative management 1

If Mesenteric Ischemia

• Emergency vascular surgery consultation for possible revascularization or bowel resection 1

Critical Pitfalls to Avoid

• Do not postpone CT to await additional laboratory results—imaging must be performed urgently in high-risk elderly presentations with rigors 1
• Do not rely on absence of fever to rule out serious infection; elderly patients have blunted inflammatory responses and may lack fever despite severe sepsis 1, 2
• Do not depend solely on physical examination to exclude surgical emergencies—exam findings are frequently unreliable in this age group 1
• Do not dismiss rigors as insignificant—they indicate systemic inflammation and mandate aggressive diagnostic work-up 1
• Do not assume low CRP excludes complicated disease—39% of patients with complicated diverticulitis have CRP <175 mg/L 2
• Do not delay antibiotics waiting for imaging in a hemodynamically unstable patient—mortality increases significantly with delayed treatment in septic shock 2

Prognostic Considerations

• In-hospital mortality for acute left colonic diverticulitis increases dramatically with age: 1.6% in patients <65 years, 9.7% in patients 65-79 years, and 17.8% in patients >80 years 2
• This patient's age (85 years) combined with rigors places them in the highest-risk category for mortality and complications 2

Monitoring and Follow-Up

• Repeat CT imaging if clinical deterioration occurs or if fever, leukocytosis, or rigors persist beyond 48-72 hours despite appropriate treatment 2
• If symptoms persist >7 days, repeat imaging to assess for inadequate source control 3
• Do not continue antibiotics beyond 7 days in uncomplicated cases, as this increases resistance without improving outcomes 3