A 45-year-old man is brought to the emergency department following a high-speed motor vehi… — USMLE Step 2 CK

A $45$ -year-old man is brought to the emergency department following a high-speed motor vehicle collision. The patient was an unrestrained driver and was ejected from the vehicle. His body mass index is $42 \text{ kg/m}^2$ . Upon arrival, he is confused and diaphoretic. His temperature is $36.5^\circ\text{C}$ , blood pressure is $76/40 \text{ mmHg}$ , pulse is $138\text{ /min}$ , and respiratory rate is $24\text{ /min}$ . Pulse oximetry shows $97\%$ on high-flow oxygen. Primary survey reveals an intact airway. The trachea is midline, and breath sounds are clear and equal bilaterally. Neck veins are flat. The abdomen is obese with a visible seatbelt sign, but deep palpation is limited; there is mild diffuse tenderness without obvious rigidity. Anteroposterior compression of the pelvis does not elicit instability. Chest and pelvic radiographs show no abnormalities. A bedside focused assessment with sonography for trauma (FAST) is attempted but is technically inadequate and indeterminate due to severe obesity and obscuring bowel gas. Intravenous fluid resuscitation with isotonic crystalloids is initiated. Which of the following is the most appropriate next step in management?

Diagnostic peritoneal lavageAnswer
B
Computed tomography of the abdomen and pelvis
C
Exploratory laparotomy
D
Diagnostic laparoscopy
E
Pelvic external fixation

Answer

Diagnostic peritoneal lavage

This patient presents with blunt abdominal trauma and severe hypovolemic shock. After ruling out intrathoracic and major pelvic sources of hemorrhage, the abdomen is the most likely site of life-threatening bleeding. The standard of care for evaluating the abdomen in an unstable trauma patient is a bedside FAST exam. However, when FAST is technically inadequate or indeterminate (often due to massive obesity, subcutaneous emphysema, or excessive bowel gas), the algorithmic next step is to perform a diagnostic peritoneal lavage (DPL). DPL rapidly and accurately identifies intraperitoneal hemorrhage, allowing the trauma team to confidently proceed to an exploratory laparotomy without the risk of performing a highly morbid nontherapeutic operation on a critically ill patient.

Step-by-Step Solution

Identify the patient's hemodynamic status.

The patient is in class III/IV hypovolemic shock (blood pressure

76/40 \text{ mmHg}

, pulse

138\text{ /min}

Hemodynamic instability dictates that all definitive diagnostic steps must be performed at the bedside in the trauma bay.

Evaluate the primary survey findings to localize the source of bleeding.

Flat neck veins, clear breath sounds, and normal chest/pelvic radiographs rule out massive hemothorax, tension pneumothorax, and life-threatening pelvic fractures. The most likely source of bleeding is intra-abdominal.

By process of elimination in blunt trauma, the abdomen (or retroperitoneum) is the presumed source of life-threatening hemorrhage.

Determine the next step for evaluating intra-abdominal hemorrhage.

The FAST exam is the first-line choice but is indeterminate in this scenario.

FAST is rapid and non-invasive, but relies heavily on sonographic windows which can be obscured by obesity and bowel gas.

Select the correct fallback diagnostic modality.

Diagnostic peritoneal lavage (DPL) must be performed.

Advanced Trauma Life Support (ATLS) guidelines mandate DPL to rapidly confirm intraperitoneal hemorrhage before committing an unstable patient to an exploratory laparotomy when FAST is equivocal or unavailable.

Key Concept

In a hemodynamically unstable patient with blunt abdominal trauma, an indeterminate or unavailable FAST exam should be immediately followed by diagnostic peritoneal lavage (DPL) to confirm intraperitoneal hemorrhage.

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