What labs and imaging are recommended for a patient who slid down a slide and hit their right flank/abdomen 1 week ago, now presenting with a large, hard mass behind the bruise and spreading ecchymosis?

Imaging Recommendations for Traumatic Flank Mass with Spreading Ecchymosis

For a patient with traumatic right flank/abdominal injury presenting with a large, hard mass and spreading ecchymosis one week after the injury, a contrast-enhanced CT scan of the abdomen and pelvis is strongly recommended as the initial imaging study.

Initial Assessment

When evaluating a patient with a traumatic flank injury and developing mass with spreading ecchymosis (traveling bruise), the following considerations should guide your approach:

Clinical Significance

• The hard mass behind a bruise with spreading ecchymosis suggests an organized hematoma with possible active bleeding
• The spreading nature of the ecchymosis indicates ongoing blood extravasation into tissue planes
• This presentation requires prompt evaluation to rule out:
  • Active hemorrhage
  • Solid organ injury (liver, kidney, spleen)
  • Retroperitoneal hematoma

Imaging Algorithm

Step 1: FAST Ultrasound

• Perform a Focused Assessment with Sonography in Trauma (FAST) exam
• Benefits:
  • Can quickly identify free intraperitoneal fluid
  • High specificity (96%) for detecting free fluid 1
  • Can rule out >500ml of free fluid if negative 1

Step 2: CT Imaging (Primary Recommendation)

• Contrast-enhanced CT of abdomen and pelvis is the definitive imaging study
• Protocol specifics:
  • IV contrast in portal venous phase (70 seconds after administration) 1
  • No oral contrast needed (does not alter sensitivity or specificity for blunt abdominal injuries) 1
  • Single-phase study is sufficient (delayed phases add radiation without significant diagnostic benefit) 2

Laboratory Studies

• Complete blood count to assess for anemia
• Basic metabolic panel to evaluate renal function
• Coagulation studies (PT/INR, PTT) to rule out coagulopathy
• Urinalysis to check for hematuria if renal involvement is suspected

Rationale for CT as Primary Imaging

1. Superior Diagnostic Performance:

   • CT has excellent performance for solid organ injuries with sensitivity 98% and specificity 98% 1
   • Can identify active bleeding sources and characterize the extent of injury 1

2. Comprehensive Evaluation:

   • Allows complete inventory of injuries and identification of active bleeding sources 1
   • Can assess both intraperitoneal and retroperitoneal spaces 1

3. Clinical Guidelines Support:

   • ACR Appropriateness Criteria strongly recommends contrast-enhanced CT for blunt abdominal trauma 1
   • European guidelines recommend CT for identification of abdominal injuries and reduction of mortality 1

Important Caveats

• Limitations of FAST:

  • Cannot rule out specific organ injuries 1
  • Limited sensitivity for retroperitoneal hematomas 1
  • Cannot characterize solid organ injuries 1

• Ultrasound Alone is Insufficient:

  • "Although US may be able to diagnose certain abdominal injuries, its relatively lower specificity compared with CT does not make it a sufficient test to fully exclude abdominal injuries" 1

• MRI is Not Recommended:

  • "Blunt abdominal trauma is not typically evaluated by MRI because of the time of acquisition" 1

• Hemodynamic Considerations:

  • If the patient becomes hemodynamically unstable during evaluation, immediate surgical consultation is warranted 1

Special Considerations for This Case

The timing of presentation (one week post-injury) with a developing mass and spreading ecchymosis suggests:

1. A contained hematoma that may be expanding
2. Possible delayed recognition of an organ injury
3. Potential vascular complication such as pseudoaneurysm

This delayed presentation with concerning physical findings makes contrast-enhanced CT particularly important to identify any active bleeding sources and to characterize the nature and extent of the mass.