A 55-year-old female on postoperative day 2 after a Hartmann procedure for diverticulitis develops oliguria (~20 mL/hr) with central venous pressure of 10 cm H₂O, lower‑extremity edema, stable vital signs and normal blood pressure; what is the most appropriate next step in management?

Postoperative Oliguria After Hartmann Procedure: Management Approach

The most appropriate next step is C. Abdomen Ultrasound to evaluate for intra-abdominal fluid collections, abscess formation, or other postoperative complications that could explain the oliguria and lower extremity edema in this hemodynamically stable patient.

Clinical Context and Differential Diagnosis

This patient presents on postoperative day 2 with oliguria (20 mL/hr, which is below the normal threshold of 0.5 mL/kg/hr), elevated central venous pressure (CVP 10 cm H₂O), and lower extremity edema despite stable vital signs and normal blood pressure. This constellation of findings suggests:

• Intra-abdominal complications such as abscess formation, anastomotic leak (though less relevant post-Hartmann), or fluid collections that could cause third-spacing and relative hypovolemia 1
• Fluid overload with adequate intravascular volume (CVP 10) but poor renal perfusion
• Early acute kidney injury from perioperative insults

The stable hemodynamics argue against immediate surgical re-exploration, while the clinical picture warrants imaging to exclude postoperative complications 2.

Why Abdominal Ultrasound is the Appropriate First Step

Ultrasound is the optimal initial imaging modality in this stable postoperative patient because:

• Non-invasive and readily available at the bedside in the ICU without requiring patient transport 1
• No contrast exposure, which is critical given the oliguria and concern for acute kidney injury 1
• Highly effective for detecting fluid collections and abscesses in the postoperative abdomen, which are common complications after Hartmann procedures for diverticulitis 2
• Can assess for hydronephrosis or ureteral obstruction that might explain the oliguria 1

The World Journal of Emergency Surgery guidelines support using ultrasound as an initial evaluation tool in patients with suspected complications of diverticular disease, particularly when performed by an experienced operator 1.

Why Other Options Are Less Appropriate

Re-exploration (Option A)

• Not indicated in a hemodynamically stable patient without signs of peritonitis, septic shock, or clinical deterioration 3, 4
• The American College of Surgeons recommends that patients with postoperative complications should only undergo re-exploration if they demonstrate hemodynamic instability, diffuse peritonitis, or failure of conservative management 3
• Premature surgical intervention increases morbidity without diagnostic confirmation of a surgical problem 5

Renal Duplex Ultrasound (Option B)

• Too narrow in focus and would miss intra-abdominal complications that are more likely given the recent surgery for complicated diverticulitis 2
• While it could assess renal perfusion, it would not evaluate for the postoperative complications (abscess, fluid collections) that are the primary concern 1

CT Abdomen with Contrast (Option D)

• Contraindicated in a patient with oliguria due to the risk of contrast-induced nephropathy 1
• While CT is the gold standard for diagnosing diverticular complications with 98-99% sensitivity and specificity, it should be reserved for when ultrasound is inconclusive or the patient's renal function improves 1, 2, 5
• Can be performed as a step-up approach if ultrasound findings are equivocal 1

Recommended Management Algorithm

1. Immediate bedside abdominal ultrasound to assess for:

   • Intra-abdominal fluid collections or abscesses (common after Hartmann for diverticulitis) 1, 2
   • Free fluid suggesting ongoing peritonitis or leak
   • Hydronephrosis or ureteral obstruction 1

2. Concurrent conservative measures while awaiting imaging:

   • Optimize fluid status based on CVP and clinical assessment
   • Monitor urine output hourly and trend laboratory markers (creatinine, electrolytes, lactate) 4
   • Ensure adequate broad-spectrum antibiotic coverage for postoperative infection 4, 5

3. If ultrasound reveals an abscess or significant fluid collection:

   • Consider percutaneous drainage if collection is ≥3-4 cm 2, 4
   • Continue IV antibiotics with gram-negative and anaerobic coverage 4, 5

4. If ultrasound is inconclusive or negative but clinical concern persists:

   • Proceed to CT abdomen without contrast initially or with delayed contrast once renal function improves 1, 2

5. If imaging shows no surgical complication:

   • Focus on medical management of oliguria (fluid optimization, avoid nephrotoxins, address prerenal vs. intrinsic renal causes)
   • Continue close monitoring for signs of clinical deterioration 4

Critical Pitfalls to Avoid

• Do not proceed directly to re-exploration without imaging confirmation of a surgical problem in a stable patient—this increases unnecessary morbidity 3, 4
• Avoid contrast-enhanced CT as the first imaging study in a patient with oliguria due to nephrotoxicity risk 1
• Do not delay imaging while pursuing prolonged conservative management, as early detection of postoperative complications (abscess, leak) improves outcomes 2, 5
• Monitor closely for deterioration (worsening vital signs, increasing leukocytosis, peritoneal signs) that would prompt escalation to CT or surgical intervention 4, 5