When is a computed tomography (CT) scan indicated in a patient with a pelvic fracture, considering factors such as hemodynamic stability, abdominal pain, and medical history, including conditions like osteoporosis?

CT Scan Indications in Pelvic Fracture

For hemodynamically stable patients with pelvic fractures, proceed directly to multi-phasic CT scan with IV contrast as the primary imaging modality, omitting pelvic X-ray entirely. 1, 2

Hemodynamically Stable Patients

CT with IV contrast is the gold standard imaging study, with 100% sensitivity and specificity for bone fractures. 3, 2 The American College of Radiology recommends performing thoraco-abdomino-pelvic CT scan with IV contrast immediately when the patient can tolerate transport to the scanner. 1

Technical Protocol Requirements

• Use multi-phasic CT protocol including arterial, portal venous, and delayed phases to optimally evaluate for hemorrhage or hematoma 3, 2
• Portal venous phase provides optimal characterization of solid organ injury and active bleeding 1
• Arterial phase imaging should be added to assess for active arterial bleeding and pseudoaneurysm formation 1
• Obtain 3D bone reconstructions to reduce tissue damage during subsequent procedures, decrease operative time, and improve surgical planning 2, 4

Critical CT Findings to Document

• Contrast extravasation (arterial blush) has 98% accuracy for identifying arterial bleeding, though absence doesn't exclude active bleeding 2
• Pelvic hematoma ≥500 cm³ strongly suggests arterial injury even without visible contrast blush 3, 2
• The predictive positive and negative values of CT with contrast compared to angiography are 93.9%, 77.8%, 88.6%, and 87.5% respectively 1

Skip Pelvic X-Ray in Stable Patients

Pelvic X-ray should be omitted in hemodynamically stable patients without pelvic instability, hip dislocation, or positive physical examination who are scheduled for CT scan. 2 The sensitivity of pelvic X-ray is only 50-68% with false negative rates of 32%, making it inadequate as definitive imaging. 3, 2, 5

Hemodynamically Unstable Patients

For unstable patients, the algorithm differs significantly:

• Perform chest X-ray and E-FAST first, then stabilize 1
• Pelvic X-ray helps identify life-threatening pelvic ring injuries (open-book injuries, vertical-shear injuries, sacral fractures) that require immediate external fixation 3, 4
• Proceed to CT with contrast and angiography/embolization as needed once minimally stabilized 1

Critical Caveat for Unstable Patients

High clinical suspicion trumps negative CT findings. In one case series, a patient with internal iliac artery bleeding had no evidence of active bleeding on CT angiography but was found to have arterial hemorrhage on subsequent angiography. 6 Therefore, if the patient remains unstable during initial resuscitation without other primary bleeding sources, proceed directly to angiography regardless of CT findings. 6

Special Populations and Additional Indications

Urogenital Injury Evaluation

Obtain CT cystography if clinical symptoms suggest bladder or urethral injury (occurs in 3.5-19% of pelvic fractures). 1 Clinical signs warranting urethral evaluation include:

• Perineal/scrotal hematoma 3
• Blood from urethral meatus 3, 4
• High-riding or non-palpable prostate on rectal exam 3
• Unstable pelvic fracture pattern 3

Perform retrograde urethrogram (RUG) prior to urethral catheterization when these signs are present to avoid complications like complete urethral transection, stricture formation, impotence, and urinary incontinence. 3, 2

Elderly Patients

Elderly patients warrant special consideration and may require angiography regardless of hemodynamic status, even with mechanically stable low-risk fractures due to age-related factors like osteoporosis and anticoagulation use. 2

Common Pitfalls to Avoid

• Never delay initial CT imaging to arbitrary time points in stable patients—perform it immediately 1
• Never perform noncontrast CT as it significantly reduces sensitivity for vascular and visceral injuries 1
• Do not rely on hemoglobin/hematocrit as early indicators of blood loss—they lag behind actual hemorrhage 2
• Never insert a transurethral catheter without prior investigation when urethral injury is suspected 3
• Do not assume absence of contrast blush excludes active bleeding—consider hematoma size and clinical trajectory 3, 2, 6