What is the best next step in managing a patient with persistent abdominal pain, nausea, and vomiting, who was previously diagnosed with left-sided diverticulitis and has an elevated leukocyte count and hyperglycemia?

Best Next Step: Obtain CT Scan of Abdomen and Pelvis

This patient requires repeat CT imaging of the abdomen and pelvis with IV contrast to evaluate for complications of diverticulitis, as she has failed outpatient antibiotic therapy and presents with concerning features including persistent symptoms, elevated lactate, leukocytosis, and new nausea/vomiting. 1

Clinical Reasoning for Repeat Imaging

Indicators of Treatment Failure

• The American Gastroenterological Association explicitly recommends CT imaging for patients who fail to improve with therapy, which this patient clearly demonstrates after 7 days of antibiotics 1
• Persistent left lower quadrant pain despite one week of appropriate antibiotic coverage (ciprofloxacin and metronidazole) indicates either progression to complicated disease or an alternative diagnosis 1
• The elevated serum lactate of 3.0 mmol/L (normal 0.7-2.1) suggests ongoing inflammation or tissue hypoperfusion, which may indicate abscess formation, microperforation, or other complications 2
• Leukocytosis of 13,000/μL with 5% band forms indicates active infection that has not resolved with outpatient management 1

Risk Factors for Complicated Disease

• This patient has diabetes mellitus with hyperglycemia (glucose 186 mg/dL), which significantly increases the risk of complicated diverticulitis 3
• Diabetic patients present with higher Hinchey scores (12.2% vs 9.2% with severe disease) and more severe CT findings (43.9% vs 31.7% with high Ambrosetti scores) compared to non-diabetic patients 3
• The elevated BUN (32 mg/dL) with normal creatinine suggests dehydration from persistent nausea/vomiting, which can mask worsening renal function in diabetic patients 3
• Symptom duration of 7+ days before re-presentation is a predictor of progression to complicated diverticulitis 1

What CT Will Reveal

• CT has 95% sensitivity and specificity for diagnosing diverticulitis and 98-99% sensitivity for identifying complications 1, 2
• The scan will identify:
  • Abscess formation (most common complication), particularly those ≥4 cm requiring percutaneous drainage 1, 2
  • Microperforation with extraluminal air 2, 4
  • Phlegmon or pericolonic fluid collections 1, 4
  • Free perforation requiring emergency surgery 2
  • Alternative diagnoses including colorectal malignancy (which can mimic diverticulitis) 1

Why Other Options Are Incorrect

Upright Abdominal Radiograph (Option A)

• Plain radiographs cannot confirm diverticulitis diagnosis and are only useful for detecting free air from perforation or obstruction 1
• This patient has no clinical signs of free perforation (no peritoneal signs, no severe distension) 1
• Radiographs would miss abscess, phlegmon, or microperforation—the most likely complications in this scenario 1, 4

General Surgery Consultation (Option C)

• Surgery consultation should occur after CT imaging confirms complicated disease requiring intervention 2
• Only 12% of diverticulitis cases present with complicated disease requiring surgical evaluation 1
• The patient is hemodynamically stable (BP 134/79, pulse 89, temp 37.8°C) without peritoneal signs, so immediate surgical consultation before imaging is premature 1, 2
• CT findings will guide whether surgical consultation is needed and what type of intervention (percutaneous drainage vs. operative management) 2

Stool for Clostridioides difficile Testing (Option D)

• While metronidazole can cause GI side effects including nausea, C. difficile testing is not the priority in this clinical scenario 1
• The patient's primary problem is persistent left lower quadrant pain with systemic inflammation (leukocytosis, elevated lactate), not primarily diarrhea 1
• The elevated lactate and persistent localized pain point toward complicated diverticulitis rather than antibiotic-associated colitis 2
• C. difficile testing can be considered after ruling out surgical complications, but should not delay definitive imaging 1

Management Algorithm After CT

If CT Shows Uncomplicated Diverticulitis

• Continue IV antibiotics with broader coverage given treatment failure 1, 2
• Admit for observation given diabetes, elevated lactate, and failed outpatient therapy 1
• Consider alternative diagnoses if imaging is negative 1

If CT Shows Abscess <4 cm

• IV antibiotics alone for 7 days 2
• Hospital admission for diabetic patient with elevated lactate 1, 3

If CT Shows Abscess ≥4 cm

• Percutaneous CT-guided drainage PLUS IV antibiotics 2
• Surgical consultation for drainage planning 2

If CT Shows Free Perforation or Peritonitis

• Immediate surgical consultation for emergency laparotomy 2
• Broad-spectrum IV antibiotics 2
• NPO, IV fluid resuscitation 2

Critical Pitfalls to Avoid

• Do not assume uncomplicated disease based on relatively normal vital signs—diabetic patients present atypically with only 50% having typical pain location and 17% having fever 2
• Do not delay imaging in diabetic patients with treatment failure, as they have higher rates of infectious complications (28.7% vs 8.2%) and acute kidney injury (5.5% vs 0.7%) when surgery is eventually required 3
• Do not rely on the one-week-old CT scan, as approximately 5% of patients develop "smoldering diverticulitis" with persistent inflammation that can progress to complications 1
• Elevated lactate in the setting of diverticulitis suggests tissue hypoperfusion from abscess, sepsis, or bowel ischemia and mandates repeat imaging 2