In a patient three days post‑colectomy presenting with fever, left lower quadrant tenderness, abdominal distension and absent bowel sounds, what is the most appropriate initial investigation?

Initial Investigation in Post-Colectomy Patient with Fever and Peritoneal Signs

In a patient three days post-colectomy presenting with fever, left lower quadrant tenderness, abdominal distension, and absent bowel sounds, obtain CBC with lactate levels immediately, followed by CT abdomen/pelvis with IV contrast—not plain abdominal X-ray or immediate re-exploration.

Recommended Diagnostic Algorithm

Step 1: Laboratory Assessment (First Priority)

Blood tests including CBC and lactate levels are crucial initial assessments to look for suggestions of bowel ischemia before proceeding to imaging 1. This approach is critical because:

• Leukocytosis and neutrophilia suggest complications including anastomotic leak, abscess formation, or bowel ischemia 1
• Elevated lactate levels indicate potential bowel ischemia and metabolic derangement 1
• Low serum bicarbonate and arterial blood pH abnormalities indicate metabolic derangement from ischemia 1
• Renal function tests assess dehydration status, which is common in postoperative ileus or obstruction 1

Step 2: Definitive Imaging (Immediate Next Step)

CT abdomen and pelvis with IV contrast is the definitive next step and the primary technique for postoperative abdominal complications 1. This is the gold standard because:

• CT is the most accurate diagnostic tool with approximately 90% accuracy for detecting postoperative complications 1
• In the postoperative setting with fever and abdominal pain, CT with IV contrast is the first study to evaluate for abscess, anastomotic leak, or bowel ischemia 1
• CT results influence treatment plans in 65% of cases overall, helping distinguish patients requiring surgery from those manageable conservatively 1
• IV contrast can help define and characterize postoperative fluid collections 2

Why NOT Plain Abdominal X-Ray

Plain radiographs have limited diagnostic value with sensitivity of 50-60% and are non-diagnostic in 36% of cases 3. Specifically in the postoperative setting:

• Abdominal X-ray has low sensitivity for sources of abdominal pain and fever or abscess, which limits its role in this setting 2
• Although it has high sensitivity (90%) for detecting intra-abdominal foreign bodies, this is not the primary concern in your clinical scenario 2
• Radiographs have moderate sensitivity for bowel obstruction (49%), but cannot differentiate mechanical obstruction from ileus or detect ischemia 2

Why NOT Immediate Re-Exploration

Do not proceed directly to re-exploration without imaging confirmation of the pathology 2. The rationale includes:

• The presence of fever with abdominal pain is primarily concerning for postoperative abscess, which may be amenable to percutaneous drainage rather than surgery 2
• CT can identify signs of ischemia (abnormal bowel wall enhancement, mesenteric edema, pneumatosis) that mandate immediate surgery 2
• Many postoperative complications (small contained leaks, localized abscesses) can be managed non-operatively if identified early on CT 2
• CT has the added advantage of allowing for abscess drainage should nonoperative management be pursued in the setting of postoperative leaks 2

Critical Clinical Context

Your patient's presentation—fever, LLQ tenderness, distension, and absent bowel sounds on postoperative day 3—raises concern for several complications:

Most Likely Diagnoses to Consider:

• Anastomotic leak with abscess formation (most concerning given fever + localized tenderness) 2
• Postoperative bowel obstruction (suggested by distension and absent bowel sounds) 2, 3
• Bowel ischemia (absent bowel sounds are a warning sign) 3, 1
• Postoperative ileus (though fever makes this less likely) 2

Warning Signs Present in Your Patient:

• Fever, which suggests infectious complications requiring urgent evaluation 2, 1
• Absent bowel sounds, which may indicate progression to bowel ischemia or strangulation with mortality rates up to 25% if not immediately treated 3, 4
• Abdominal distension occurring in 65.3% of obstruction cases 3
• Postoperative day 3 timing, when anastomotic leaks typically manifest 5

Common Pitfalls to Avoid

• Do not rely on clinical examination alone in postoperative patients, as signs may be subtle despite serious pathology 1
• Do not assume normal vital signs exclude complications—elderly patients may not mount typical inflammatory responses 1
• Do not withhold contrast due to renal concerns without weighing the mortality risk of missed diagnosis 1
• Do not mistake postoperative ileus for simple constipation—progressive symptoms warrant aggressive investigation 1
• Do not delay CT when there are signs of alarm such as fever, peritoneal signs, or hemodynamic instability 3, 1

Specific Imaging Protocol

When ordering CT for this patient:

• Request CT abdomen and pelvis WITH intravenous contrast 2, 1
• No oral contrast is needed in suspected high-grade obstruction 2
• CT should specifically evaluate for: anastomotic integrity, fluid collections/abscesses, bowel wall enhancement patterns (ischemia), free air, and transition points 2