What is the best course of treatment for a patient presenting with nausea, vomiting, and lower left quadrant pain?

Management of Nausea, Vomiting, and Lower Left Quadrant Pain

The most critical first step is obtaining a CT scan of the abdomen and pelvis with IV contrast to confirm the diagnosis of acute diverticulitis—the most common cause of left lower quadrant pain—and to identify complications that will determine whether conservative management, antibiotics, drainage, or surgery is required. 1

Immediate Diagnostic Workup

Imaging Priority

• CT abdomen and pelvis with IV contrast is the gold standard with 95% sensitivity and specificity for diagnosing diverticulitis and identifying complications (abscess, perforation, peritonitis). 1
• CT must be performed to evaluate for:
  • Intestinal wall thickening and pericolonic fat inflammation 1
  • Signs of perforation (extraluminal gas, intra-abdominal fluid) 1
  • Abscess formation (size determines treatment approach) 1
  • Alternative diagnoses (epiploic appendagitis, colitis, inflammatory bowel disease, bowel obstruction) 1, 2

Laboratory Assessment

• Obtain CBC (leukocytosis expected but may be absent), CRP (typically elevated even when WBC is normal), and procalcitonin 1
• Check complete metabolic panel to assess for electrolyte abnormalities from vomiting and evaluate renal function before contrast administration 3

Symptomatic Management of Nausea and Vomiting

Antiemetic Therapy

• Ondansetron 4 mg IV is first-line for postoperative-type nausea/vomiting, with proven efficacy in preventing emetic episodes. 4
• If ondansetron fails or is insufficient, add metoclopramide 10 mg IV/PO every 6 hours as it addresses both nausea and promotes gastric emptying. 1, 3
• Alternative: Prochlorperazine 10 mg IV/PO every 6-8 hours can be used as adjunct or alternative. 3

Critical Pitfall

• Do not use anticholinergics (like dicyclomine) until bowel obstruction is definitively excluded, as they can worsen obstruction and mask progressive ileus. 3, 4

Treatment Algorithm Based on CT Findings

Uncomplicated Diverticulitis (No abscess, no perforation)

• Immunocompetent patients with mild disease: Conservative treatment WITHOUT antibiotics is appropriate. 1
• Immunocompromised, elderly, or patients with comorbidities: Antibiotic therapy for no more than 7 days. 1
• Outpatient management with clear liquid diet advancing as tolerated 1

Small Diverticular Abscess (<3-4 cm)

• Antibiotic therapy alone for 7 days without drainage 1
• Appropriate antibiotic regimens:
  • Ertapenem 1 g IV q24h, OR 1
  • Eravacycline 1 mg/kg IV q12h 1

Large Diverticular Abscess (>3-4 cm)

• Percutaneous drainage combined with antibiotic therapy for 4 days in immunocompetent, non-critically ill patients 1
• If drainage not feasible:
  • Immunocompetent, stable patients: Consider antibiotics alone 1
  • Critically ill or immunocompromised: Surgical intervention is primary treatment 1

Complicated Diverticulitis with Peritonitis

• Immediate surgical consultation required 1
• Surgical options:
  • Primary resection with anastomosis ± diverting stoma (clinically stable, no major comorbidities) 1
  • Hartmann's procedure (critically ill or multiple comorbidities) 1
• Broad-spectrum antibiotics for septic shock:
  • Meropenem 1 g IV q6h by extended infusion, OR 1
  • Doripenem 500 mg IV q8h by extended infusion, OR 1
  • Imipenem/cilastatin 500 mg IV q6h by extended infusion 1

Special Populations

Immunocompromised Patients

• Acute left-sided colonic diverticulitis carries increased mortality in immunocompromised patients. 1
• Lower threshold for imaging, hospitalization, and surgical intervention 1
• Antibiotic therapy up to 7 days based on clinical response even with adequate source control 1

Transplant Recipients

• Leukocytosis may be absent despite serious infection 1
• CRP is more reliable marker than WBC count 1
• Early surgical intervention is mandatory if complications develop 1

Follow-up Considerations

Colonoscopy Timing

• Defer colonoscopy for 6-8 weeks after acute episode or until complete symptom resolution, whichever is longer 1
• Colonoscopy is advised after complicated diverticulitis to exclude malignancy (7.9% cancer prevalence in complicated cases vs 1.3% in uncomplicated) 1
• May defer if high-quality colonoscopy performed within 1 year 1

Red Flags Requiring Immediate Re-evaluation

• Fever, inability to pass gas/stool, severe tenderness with guarding, bloody stools, or signs of shock mandate emergency evaluation 5
• Failure to improve within 48-72 hours on appropriate therapy requires repeat imaging 1, 3
• Weight loss, anemia, or change in bowel habits warrant repeat colonoscopy despite prior normal study 5

Alternative Diagnoses to Consider

If CT excludes diverticulitis and symptoms persist:

• Epiploic appendagitis: Sharp, localized pain without fever, nausea, or laboratory abnormalities; specific CT findings include oval fatty lesion with surrounding inflammation 2
• Colitis (infectious, ischemic, inflammatory bowel disease) 1
• Gynecologic pathology in premenopausal women: Obtain pelvic/transvaginal ultrasound 5
• Functional bowel disorders if all structural pathology excluded 5