Abdominal/Pelvic Trauma

Naveed Ahmad, MD | Radiology Key | PDF

Key Concepts Summary

1. Imaging Modalities in Trauma

• Radiography: Rapid and portable for the critically ill; useful for identifying free air, displaced pelvic/hip fractures, and radiopaque foreign bodies (like bullets), but insensitive to soft tissue organ injuries.
• Ultrasonography (FAST): The Focused Assessment with Sonography for Trauma (FAST) evaluates four areas (hepatorenal, perisplenic, pelvic, and pericardial) for hemoperitoneum. Highly operator-dependent.
• Computed Tomography (CT): The definitive workhorse for abdominopelvic trauma due to rapid acquisition and high sensitivity/specificity for hemorrhage, visceral injury, and fractures. Requires IV contrast for active bleeding, vascular injury, and solid organs.
• MRI: Rarely used in acute emergency triage due to long scan times and lack of portability; reserved for targeted questions (e.g., radiographically occult hip/spinal fractures).

2. Solid Organ & Vascular Injury

• Splenic Trauma: The most frequently injured organ in blunt abdominal trauma. Most are managed nonoperatively, though active extravasation, pseudoaneurysms, or large hemoperitoneum favor endovascular embolization. The sentinel clot sign indicates that the densest blood pools nearest the primary bleeding source.
• Hepatobiliary Trauma: Liver injuries are graded 1–6; most isolated injuries are managed conservatively unless the patient is hemodynamically unstable.
• Pancreatic Trauma: Most vulnerable at the body via a crush mechanism. A parenchymal laceration of 50% width strongly suggests main pancreatic duct injury, which drives morbidity.

3. Genitourinary & Pelvic Trauma

• Renal Injuries: Include contusions, lacerations, subcapsular/perirenal hematomas, and vascular disruptions (e.g., main renal artery transection leading to an unenhancing “shattered kidney”). Delayed excretory-phase imaging is critical to evaluate urine leaks.
• Bladder Rupture: Strongly associated with pelvic fractures (10% of pelvic fractures involve bladder injury). Intraperitoneal rupture involves the bladder dome and requires surgery; extraperitoneal rupture is managed conservatively and often demonstrates the molar tooth sign on CT cystography.
• Pelvic Ring Fractures: The pelvis acts as a rigid ring, typically fracturing in at least two places. Classified by mechanism into Anterior-Posterior (AP) compression, Lateral compression (most common), and Vertical shear. Life-threatening pelvic hemorrhage often requires angiographic embolization.

Multiple-Choice Quiz

Question 1

A 34-year-old male is brought to the emergency department following a high-speed motor vehicle collision. A contrast-enhanced trauma CT scan demonstrates a large volume hemoperitoneum. Upon reviewing the multiplanar reformatted images, the radiologist notes that the highest-attenuation blood clot is localized specifically within the left upper quadrant surrounding the spleen. What is the established radiologic term for this focal high-density hematoma?

• A) Sentinel clot sign
• B) Molar tooth sign
• C) Page kidney
• D) Tip of the iceberg sign

Answer: A) Sentinel clot sign

Explanation: The “sentinel clot sign” refers to the finding that when multiple solid organ injuries or large-volume hemoperitoneum are present, the densest blood (highest Hounsfield units) tends to pool closest to the site of active or primary hemorrhage, helping identify the bleeding source (such as a splenic injury).

Question 2

During a trauma evaluation of a patient with a complex pelvic ring fracture from a side-impact motor vehicle crash, a CT cystogram is performed. The axial images reveal extravesicular contrast pooling within the space of Retzius, creating a characteristic configuration resembling a molar tooth. What is the appropriate management for this specific injury type?

• A) Immediate exploratory laparotomy and surgical repair of the bladder dome
• B) Conservative management (nonoperative) with continuous bladder drainage
• C) Urgent primary urethral realignment and open cystostomy
• D) Endovascular transcatheter arterial embolization of the internal iliac branches

Answer: B) Conservative management (nonoperative) with continuous bladder drainage

Explanation: The “molar tooth sign” is characteristic of an extraperitoneal bladder rupture, which accounts for roughly 60% of traumatic bladder ruptures and is typically managed conservatively (unlike intraperitoneal ruptures at the bladder dome, which require surgical repair).

Question 3

A trauma patient undergoes a multiphase abdominal CT scan following a severe deceleration injury. Which of the following phases is specifically crucial to distinguish active arterial contrast extravasation from a pseudoaneurysm, as well as to evaluate delayed urinary collecting system injuries?

• A) Noncontrast phase
• B) Early arterial phase (20–25 seconds)
• C) Delayed/excretory phase (5–10 minutes)
• D) Unenhanced pre-procedure localizer

Answer: C) Delayed/excretory phase (5–10 minutes)

Explanation: A delayed phase (acquired 5 to 10 minutes post-injection) allows contrast to collect and pool, making it possible to distinguish an expanding focus of active contrast extravasation from a contained pseudoaneurysm, as well as to detect contrast extravasation indicative of a pelvicalyceal or ureteral urine leak.

Question 4

Which of the following computed tomography findings is most indicative of a main pancreatic duct injury following a severe upper abdominal crush injury?

• A) A small focal fluid collection isolated to the lesser sac without parenchymal disruption
• B) A parenchymal laceration extending through greater than 50% of the pancreatic width
• C) Diffuse pancreatic enlargement with homogenous post-contrast enhancement
• D) Isolated thickening of the posterior gastric wall adjacent to the pancreatic body

Answer: B) A parenchymal laceration extending through greater than 50% of the pancreatic width

Explanation: Because clinical symptoms and initial lab findings (such as serum amylase) can be delayed and insensitive following pancreatic trauma, imaging relies on structural cues. A parenchymal laceration extending through more than 50% of the pancreatic width strongly correlates with major pancreatic duct disruption, prompting further evaluation via MRCP or surgical/endoscopic intervention.