What is the initial step in assessing an elderly male with progressive abdominal distention and pain, left lower quadrant tenderness, and decreased bowel sounds on the 5th day after colectomy (surgical removal of part or all of the colon)?

Initial Assessment: CBC and Lactate

In an elderly male on postoperative day 5 after colectomy presenting with progressive distention, pain, left lower quadrant tenderness, and decreased bowel sounds, the initial step in assessment is D - CBC and lactate, followed immediately by abdominal imaging. This approach prioritizes detection of life-threatening complications like bowel ischemia or anastomotic leak that directly impact mortality and morbidity.

Rationale for Laboratory Testing First

Blood tests including CBC and lactate levels are crucial initial assessments to look for suggestions of bowel ischemia before proceeding to imaging. 1 In the postoperative setting, particularly after colectomy, these laboratory markers serve as critical screening tools:

• Leukocytosis and neutrophilia suggest complications including anastomotic leak, abscess formation, or bowel ischemia 2
• Elevated lactate levels are laboratory findings suggesting complications and potential bowel ischemia 2
• Low serum bicarbonate and arterial blood pH abnormalities indicate metabolic derangement from ischemia 2
• Renal function tests assess dehydration status, which is common in postoperative ileus or obstruction 2

The absence of rebound tenderness does not exclude serious pathology. The absence of peritonitis does not indicate the absence of bowel ischemia, and physical examination may be difficult due to abdominal distension. 1 In elderly patients, pain may be less prominent despite serious underlying complications. 2

Immediate Imaging After Laboratory Assessment

Following laboratory evaluation, CT abdomen and pelvis with IV contrast is the definitive next step and is considered the primary technique for postoperative abdominal complications. 1, 3

Why CT is Essential in This Context:

• CT is the most accurate diagnostic tool with approximately 90% accuracy for detecting postoperative complications 2
• 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 has high sensitivity (90%) for detecting bowel obstruction and can differentiate between mechanical obstruction and ileus 2
• CT is the most sensitive technique for depicting complications including perforation, abscess, and anastomotic dehiscence 3

Why Other Options Are Inadequate

Plain Abdominal Radiography (Option A):

• Plain radiographs have limited diagnostic value with only 50-60% sensitivity for bowel obstruction 2
• Abdominal radiography contributes to patient treatment in only a small percentage of cases (4%) in acute abdominal pain 4
• While radiographs may show bowel obstruction patterns, they cannot reliably detect anastomotic leaks, abscesses, or bowel ischemia 1, 5

Immediate Laparotomy (Option B):

• Laparotomy without imaging is inappropriate as it exposes the patient to unnecessary surgical risk when non-operative management may be sufficient
• CT results influence treatment plans in 65% of cases overall, helping distinguish patients requiring surgery from those manageable conservatively 1
• Proceeding directly to surgery without imaging may miss alternative diagnoses or lead to inappropriate surgical intervention

IV Fluids and Analgesics Alone (Option C):

• Resuscitation is important but cannot be the sole initial step without diagnostic evaluation
• This approach risks delayed diagnosis of life-threatening complications like anastomotic leak or bowel ischemia
• While supportive care is necessary, diagnostic evaluation must occur concurrently to guide definitive management

Clinical Algorithm

Step 1: Obtain CBC, comprehensive metabolic panel, lactate, and blood gas 1, 2

Step 2: Simultaneously initiate IV fluid resuscitation while awaiting laboratory results 1

Step 3: Proceed immediately to CT abdomen/pelvis with IV contrast 1

• Do not delay CT for contrast concerns in elderly patients, as prompt diagnosis outweighs the risk of contrast-induced kidney injury 1
• Even in patients with chronic kidney disease, CT with contrast is justified when timely diagnosis may be life-saving 1

Step 4: Based on CT findings, determine need for:

• Interventional drainage (abscess ≥3 cm) 1
• Emergency surgery (free perforation, peritonitis, complete obstruction with ischemia) 1
• Conservative management with bowel rest and antibiotics (uncomplicated ileus or partial obstruction) 1

Critical 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 on day 5 warrant aggressive investigation 2