8.3 Abdominal & Pelvic Trauma: FAST Examination & Damage Control Surgery

Mechanisms: Blunt vs. Penetrating Abdominal Trauma

Abdominal trauma presents substantial diagnostic challenges because physical examination alone is notoriously unreliable in the acute resuscitation setting—altered sensorium from traumatic brain injury, alcohol, or illicit substance intoxication blunts peritoneal signs in up to 50% of multisystem trauma patients. Clinicians practicing across Caribbean casualty departments must master rapid algorithmic assessment to differentiate patients requiring emergent surgical intervention from those who can be safely managed non-operatively.

Mechanisms of Injury

• Blunt Abdominal Trauma (BAT): Results from vehicular collisions, pedestrian strikes, falls from height, and physical assaults. Traumatic force causes direct crush against the vertebral column and rapid deceleration shearing forces at vascular pedicles. The spleen (40-50%) and liver (35-45%) are the most commonly injured solid organs.
• The 'Seatbelt Sign': A linear or transverse contusion across the lower anterior abdominal wall or chest. Strongly correlates with underlying intra-abdominal pathology, carrying an elevated risk of mesenteric avulsion, small bowel perforation, and Chance fractures of the lumbar spine (horizontal distraction fractures through the vertebral body and posterior arch).
• Penetrating Abdominal Trauma (PAT): Divided into low-velocity stab wounds and high-velocity gunshot wounds (GSWs). High-velocity projectiles generate temporary tissue cavitation and blast waves that cause extensive microvascular and parenchymal injury far beyond the visible projectile path.
• Mandatory Laparotomy Indications:
  • Hemodynamic instability with positive FAST or documented hemoperitoneum
  • Signs of generalized peritonitis (involuntary muscular rigidity, severe rebound tenderness)
  • Evisceration of abdominal viscera (omentum or bowel loops)
  • Gunshot wounds with a trajectory clearly penetrating the peritoneal cavity
  • Frank gastrointestinal bleeding (hematemesis, bright red blood via nasogastric aspirate or digital rectal examination) following penetrating injury
  • Radiographic pneumoperitoneum or diaphragmatic disruption

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The FAST & Extended FAST (E-FAST) Protocol

The Focused Assessment with Sonography for Trauma (FAST) is a rapid, non-invasive, bedside ultrasound protocol designed to detect free intraperitoneal and pericardial fluid (blood). It can be executed in under 3 minutes concurrently with resuscitation.

The Four Core Acoustic Windows

1. Hepatorenal Recess (Morrison's Pouch): Probe placed in the right mid-to-posterior axillary line at the 8th to 11th intercostal spaces. Morrison's pouch is the most gravitationally dependent intraperitoneal space in a supine patient; as little as 200 to 250 mL of free hemoperitoneum pools here as a dependent anechoic (black) stripe between the liver capsule and right renal parenchyma.
2. Splenorenal Recess: Probe placed in the left posterior axillary line at the 6th to 9th intercostal spaces. Visualizes the interface between the spleen and left kidney, as well as the left subphrenic space.
3. Suprapubic (Pelvic) Window: Probe placed immediately superior to the pubic symphysis in sagittal and transverse planes. Evaluates the rectovesical pouch in males and the rectouterine pouch of Douglas in females. Best examined before urinary catheterization, as a moderately distended bladder provides an acoustic window.
4. Subxiphoid Pericardial Window: Probe angled steeply toward the left shoulder under the xiphoid process. Visualizes the four cardiac chambers to detect anechoic fluid within the pericardial sac and right ventricular collapse.

• Extended FAST (E-FAST): Expands the exam to include bilateral anterior chest windows (2nd-4th intercostal spaces midclavicular line) to evaluate for pneumothorax (absence of lung sliding, absence of comet-tail artifacts, presence of 'stratosphere / barcode sign' on M-mode) and bilateral costophrenic angles for hemothorax.

FAST Algorithmic Resuscitation Pathway

• Hemodynamically Unstable + FAST Positive: Proceed immediately to exploratory laparotomy. Do NOT obtain a CT scan; transporting an unstable patient with confirmed hemoperitoneum to the scanner is a fatal error.
• Hemodynamically Unstable + FAST Negative: Rapidly evaluate extra-abdominal sources of bleeding (pelvic fractures, thoracic hemothorax, retroperitoneum, bilateral femurs) or consider Diagnostic Peritoneal Aspiration/Lavage (DPA/DPL).
• Hemodynamically Stable (FAST Positive or Negative): Proceed to intravenous contrast-enhanced abdominopelvic Computed Tomography (CT). Triple-phase CT is the gold standard for grading solid organ lacerations, detecting active arterial contrast extravasation ('contrast blush'), and identifying retroperitoneal hematomas.

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Solid Organ Injuries: Spleen, Liver & Hollow Viscus

Splenic Trauma & The AAST Grading Scale

• The spleen is the most frequently injured solid organ in blunt trauma due to its delicate capsule and vascular attachments.

Use the highest imaging, operative or pathological criterion; multiple injuries advance one grade up to Grade III.

• Non-Operative Management (NOM): The standard of care for hemodynamically stable patients with Grade I to III and selected Grade IV–V injuries in centres with immediate surgical and embolization capability in the absence of peritonitis or hollow viscus perforation. Consists of ICU admission, continuous hemodynamic monitoring, serial abdominal examinations, serial hemoglobin checks, and transcatheter arterial embolization (TAE) for patients with active contrast blush or pseudoaneurysm.
• Operative Management: Indicated for hemodynamic instability, failed NOM, or Grade V vascular avulsion. Interventions range from splenorrhaphy (topical hemostats, partial resection) to total splenectomy.
• Post-Splenectomy Infection Prophylaxis: Total splenectomy eliminates splenic macrophage phagocytosis of unopsonized bacteria, predisposing to Overwhelming Post-Splenectomy Infection (OPSI). OPSI is a fulminant septic shock syndrome with 50-70% mortality within 24-48 hours, predominantly caused by encapsulated pathogens: Streptococcus pneumoniae (60%), Neisseria meningitidis, and Haemophilus influenzae type b (Hib).
  • Vaccination Protocol: Administer pneumococcal conjugate/polysaccharide (PCV20 or PCV15 followed by PPSV23), meningococcal ACWY and B, and Hib vaccines at day 14 post-splenectomy (or prior to discharge). Vaccinating during the acute post-traumatic phase yields blunted humoral immune responses.

Hepatic Trauma & The Pringle Maneuver

• The liver has a dual vascular supply (hepatic artery 25%, portal vein 75%). The majority of blunt liver lacerations are successfully treated non-operatively in stable patients.
• The Pringle Maneuver: During emergency laparotomy for exsanguinating hepatic hemorrhage, atraumatically clamp the hepatoduodenal ligament (foramen of Winslow) to compress the portal vein, proper hepatic artery, and common bile duct.
  • If bleeding ceases completely, the hemorrhage originates from intrahepatic branches of the hepatic artery or portal vein.
  • If vigorous bleeding persists despite clamping, the hemorrhage originates from the retrohepatic inferior vena cava or major hepatic veins, requiring retrohepatic packing, total vascular exclusion, or vascular shunting.

Hollow Viscus Perforation

• Blunt trauma can crush bowel loops against the spine or cause sudden closed-loop bursting. CT findings include free intraperitoneal fluid without solid organ laceration, focal bowel wall thickening, mesenteric fat stranding, or pneumoperitoneum. Hollow viscus injuries require prompt surgical resection or repair to prevent fecal peritonitis and sepsis.

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Pelvic Fractures & Exsanguinating Retroperitoneal Bleeding

High-energy pelvic ring disruptions (falls from height, motor vehicle collisions) carry mortality rates approaching 30-50% when associated with hemodynamic instability.

Fracture Classification (Young-Burgess System)

1. Lateral Compression (LC): Most common (60-70%). Force directed laterally; internal rotation of the hemipelvis. Lower overall vascular bleeding risk.
2. Anteroposterior Compression (APC / 'Open Book'): Force applied anteriorly; diastasis of the pubic symphysis (> 2.5 cm indicates sacroiliac ligament disruption). Expands the total pelvic volume exponentially, destroying natural tamponade.
3. Vertical Shear (VS): Extreme axial shearing force (fall from high height landing on one leg). Complete vertical displacement of the hemipelvis with disruption of anterior and posterior sacroiliac ligaments; highest mortality rate.

Source of Pelvic Bleeding

• 85% - 90% Venous & Osseous: Low-pressure bleeding from the extensive presacral and paravesical venous plexuses and exposed cancellous fracture bone surfaces.
• 10% - 15% Arterial: High-pressure hemorrhage from branches of the internal iliac artery, most commonly the superior gluteal artery, internal pudendal artery, obturator artery, and lateral sacral artery.

Emergency Mechanical Stabilization: Pelvic Binder

• Critical Anatomical Landmark: The commercial pelvic binder (e.g., SAM Sling) or folded bedsheet must be positioned directly over the GREATER TROCHANTERS of the femurs, NOT over the iliac crests!
• Rationale: Compressing the greater trochanters leverages the femoral heads to rotate the pubic bones medially, closing the pelvic ring and reducing pelvic volume to promote self-tamponade.
• If the patient remains unstable despite binder application and massive transfusion: proceed to Pre-Peritoneal Pelvic Packing (PPP) via a midline infraumbilical incision to pack the true pelvis retroperitoneally, followed by transcatheter arterial embolization (TAE) in interventional radiology.

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Damage Control Surgery (DCS): The Three-Stage Paradigm

Damage Control Surgery represents a paradigm shift from traditional, prolonged definitive anatomical reconstructions to abbreviated, staged operative procedures in physiologically exhausted patients displaying the lethal triad (hypothermia, acidosis, coagulopathy).

┌─────────────────────────────────────────────────────────────────────────────┐
│ STAGE 1: ABBREVIATED PRIMARY LAPAROTOMY (< 60 - 90 MINUTES)                 │
│ • Rapid surgical hemostasis (four-quadrant packing, vascular shunts)        │
│ • Contamination control (stapling bowel perforations without anastomosis)   │
│ • Temporary Abdominal Closure (TAC via negative-pressure wound therapy)    │
└──────────────────────────────────────┬──────────────────────────────────────┘
                                       │ Transfer to ICU
                                       ▼
┌─────────────────────────────────────────────────────────────────────────────┐
│ STAGE 2: INTENSIVE CARE RESUSCITATION (12 - 48 HOURS)                       │
│ • Active physiological restoration (core warming, acidosis correction)      │
│ • Viscoelastic-guided component transfusion (TEG/ROTEM)                     │
│ • Re-establish organ perfusion and normothermia                             │
└──────────────────────────────────────┬──────────────────────────────────────┘
                                       │ Return to Operating Room
                                       ▼
┌─────────────────────────────────────────────────────────────────────────────┐
│ STAGE 3: DEFINITIVE RE-LAPAROTOMY (24 - 48 HOURS)                           │
│ • Removal of surgical abdominal packs and inspection                        │
│ • Definitive anatomical reconstruction (bowel anastomosis or stoma)         │
│ • Delayed primary fascial closure of the abdominal wall                     │
└─────────────────────────────────────────────────────────────────────────────┘

• Temporary Abdominal Closure (TAC): Crucial to prevent Abdominal Compartment Syndrome (ACS), defined as a sustained intra-abdominal pressure (IAP) > 20 mmHg associated with new-onset organ dysfunction (oliguria, elevated peak airway pressures, decreased cardiac output). Utilizing a Barker vacuum pack or commercial negative-pressure dressing preserves the abdominal fascia for delayed primary closure.