What is the recommended emergency department management for an adult with suspected acute diverticulitis, including imaging, fluid resuscitation, bowel rest, antibiotic regimen for uncomplicated and complicated disease, and criteria for admission versus discharge?

Emergency Department Management of Acute Diverticulitis

Obtain an abdominal CT with IV contrast immediately in all non-pregnant adults with suspected acute diverticulitis to confirm diagnosis and guide treatment decisions, as clinical examination alone is unreliable with only 65% positive predictive value. 1

Diagnostic Imaging Approach

Initial Imaging Selection

• CT abdomen/pelvis with IV contrast is the mandatory first-line imaging modality for suspected acute diverticulitis in non-pregnant adults, achieving 95% sensitivity and 96% specificity for detecting complicated disease 1, 2
• IV contrast is essential to characterize bowel wall abnormalities, detect subtle complications, and identify abscess formation; CT without contrast may be appropriate only when IV contrast is contraindicated 1
• If CT is unavailable or contraindicated, ultrasound or MRI can be used as alternative imaging modalities 1
• In pregnant patients, ultrasound or MRI should be considered, though no clear preference exists between these two modalities 1

Pre-Imaging Fluid Resuscitation

• Administer 500-1000 mL bolus of 0.9% normal saline IV over 1-2 hours before CT in patients with normal renal function to prevent contrast-induced nephropathy 3
• Continue maintenance infusion at 100-150 mL/hour during and for 6-12 hours after contrast administration 3
• In hemodynamically unstable patients with suspected perforation, prioritize aggressive resuscitation with 500-1000 mL boluses of normal saline or lactated Ringer's, repeating based on hemodynamic response before proceeding to imaging 3

Clinical Decision Rules

• The Laméris criteria can establish diagnosis without imaging when all three are present: (1) left lower quadrant tenderness only, (2) CRP >50 mg/L, and (3) absence of vomiting—this combination yields 97% positive predictive value 1, 2
• However, imaging should still be obtained in most ED presentations because clinical diagnosis alone has poor accuracy (65% PPV, 98% NPV), and CT changes management in 37% of cases 1

Critical Pitfall: Low CRP values (<150 mg/L) do not reliably exclude complicated diverticulitis—35.5% of patients with CRP <150 mg/L still have complicated disease on CT 4

Classification and Risk Stratification

Use the WSES (World Society of Emergency Surgery) classification to guide all treatment decisions 1, 2:

Uncomplicated Diverticulitis (Stage 0)

• CT findings: Diverticula, bowel wall thickening, increased pericolic fat density
• No abscess, perforation, or distant complications 1, 2

Complicated Diverticulitis (Stages 1-4)

Stage	CT Findings	Management
1A	Pericolic air bubbles or small fluid collection within 5 cm of inflamed segment	IV antibiotics, close monitoring; no drainage needed [2]
1B	Abscess ≤4 cm	IV antibiotics; drainage generally not required [1,2]
2A	Abscess >4 cm	IV antibiotics + percutaneous CT-guided drainage [1,2]
2B	Distant free gas (>5 cm from inflamed bowel)	IV antibiotics, consider drainage if accessible abscess, obtain surgical consultation [2]
3	Diffuse intra-abdominal fluid without distant free gas	IV antibiotics, drainage if abscess present, surgical consultation [2]
4	Diffuse fluid with distant free gas (generalized peritonitis)	IV antibiotics + urgent surgical intervention (laparoscopic preferred) [2]

Antibiotic Management

Uncomplicated Diverticulitis (Stage 0)

Antibiotics are NOT routinely required for immunocompetent patients with uncomplicated diverticulitis. 2, 5

• Multiple high-quality RCTs (AVOD, DIABLO, DINAMO, STAND) demonstrate non-inferiority of observation without antibiotics regarding recovery, complications, recurrence, and mortality 5
• The American Society of Colon and Rectal Surgeons and American Academy of Family Physicians now recommend against routine antibiotics for uncomplicated disease 5

Antibiotics may be safely omitted when ALL criteria are met: 2

• Immunocompetent status
• No significant comorbidities
• Able to tolerate oral intake
• Reliable follow-up available
• Absence of systemic signs (persistent fever, chills, rising WBC)

Complicated Diverticulitis (Stages 1-4)

Broad-spectrum IV antibiotics covering gram-negative and anaerobic organisms are mandatory for all complicated stages. 2

Recommended regimens for complicated disease: 6

• Ampicillin + gentamicin + metronidazole
• Piperacillin-tazobactam
• Ciprofloxacin + metronidazole

Continue IV antibiotics until clinical improvement permits transition to oral therapy 2

Bowel Rest and Supportive Care

Uncomplicated Disease

• Clear liquid diet is appropriate; strict NPO is not required 2
• Acetaminophen for pain control 2
• Advance diet as tolerated based on symptom improvement

Complicated Disease

• Initiate aggressive fluid resuscitation: 2-3 liters of normal saline or lactated Ringer's in first 3-6 hours for patients with signs of sepsis or peritonitis 3
• NPO status for stages requiring surgical intervention or percutaneous drainage
• Continue IV hydration at 100-150 mL/hour 3

Admission Versus Discharge Criteria

Discharge Criteria (Outpatient Management Appropriate)

Discharge is safe for uncomplicated diverticulitis (Stage 0) when ALL criteria are met: 2

• Immunocompetent without significant comorbidities
• Able to tolerate oral intake
• Adequate pain control achieved
• Reliable follow-up within 48-72 hours
• No systemic signs: no persistent fever, stable vital signs, no rising leukocytosis
• Patient can return immediately if symptoms worsen

Admission Criteria (Hospitalization Required)

Admit to hospital for: 2

• All complicated diverticulitis (Stages 1-4) 2
• Immunocompromised status
• Significant comorbidities
• Unable to tolerate oral intake
• Inadequate pain control
• Unreliable follow-up
• Systemic signs: fever, tachycardia, hypotension, rising inflammatory markers
• Free intra-abdominal fluid on CT (independent predictor of need for ICU and interventional therapy) 4

Red flags predicting progression to complicated disease requiring admission: 2

• Symptoms >5 days duration
• Pain score ≥8/10 on visual analog scale
• Vomiting
• CRP >140 mg/L
• Age <50 years

Interventional and Surgical Consultation

Percutaneous Drainage Indications

• Abscess >4 cm (Stage 2A): CT-guided drainage is recommended 1, 2
• Accessible abscesses in Stages 2B-3 2

Surgical Consultation Indications

• Obtain immediate surgical consultation for Stages 2B-4 2
• Stage 4 (generalized peritonitis): Urgent surgical intervention required 2
• Stages 2B-3: Surgical assessment for potential operative management 2

Critical Pitfall: Non-operative management of Stage 2B (distant free gas without diffuse peritonitis) has a 57-60% failure rate when large volumes of distant air are present—maintain low threshold for surgical consultation 2

Follow-Up and Colonoscopy

• Schedule outpatient follow-up within 48-72 hours for discharged patients 2
• Monitor renal function at 48-72 hours in patients who received IV contrast with risk factors 3
• Colonoscopy should be performed 6-8 weeks after resolution to exclude malignancy, as imaging alone cannot reliably distinguish diverticulitis from colon cancer 7