A 24-year-old man presents to the emergency department 50 minutes after a high-speed motorcycle collision with left-sided blunt trauma. He is haemodynamically stable with left upper-quadrant pain and Kehr's sign. A FAST examination is performed. The structure marked **A** in the ultrasound image—a crescentic hypo-to-anechoic collection conforming to the splenic contour—is most consistent with which of the following?
A. Free intraperitoneal haemorrhage in the peritoneal cavity
B. Perisplenic abscess with loculated infection
C. Subcapsular haematoma of the spleen
D. Splenic parenchymal laceration with active bleeding
Explanation
Why Subcapsular haematoma of the spleen is right
The crescentic hypo-to-anechoic collection that conforms to the splenic contour and is located between the splenic capsule and parenchyma (as shown by structure A) is the classic ultrasound appearance of a subcapsular haematoma. This finding is pathognomonic for blood trapped in the potential space between the capsule and the underlying splenic tissue. In this haemodynamically stable patient with blunt left-sided trauma and Kehr's sign, a subcapsular haematoma represents an AAST grade 1–2 splenic injury amenable to non-operative management, as confirmed by subsequent CT imaging in this case. The crescentic shape reflects the anatomy of the splenic capsule and the constraint of the blood collection by the intact capsule itself.
Why each distractor is wrong
Free intraperitoneal haemorrhage in the peritoneal cavity: Free fluid in the peritoneal cavity (detected in Morison's pouch, the pelvic view, or the pericardial view during FAST) would appear as anechoic or hypoechoic fluid in dependent areas, not as a crescentic collection conforming to the splenic surface. In this case, Morison's pouch and other FAST views were explicitly negative for free fluid, ruling out this diagnosis.
Splenic parenchymal laceration with active bleeding: A parenchymal laceration would typically show heterogeneous echogenicity within the splenic substance itself, often with irregular margins and possible active bleeding (echogenic swirling or colour Doppler flow). The crescentic shape and subcapsular location of structure A are inconsistent with a parenchymal injury; moreover, the absence of active contrast extravasation on CT confirms haemostasis.
Perisplenic abscess with loculated infection: An abscess would present with clinical signs of infection (fever, elevated white cell count, systemic inflammatory response) and would typically develop over days to weeks, not acutely after trauma. The acute presentation, haemodynamic stability, and normal lactate (2.8 mmol/L) make infection unlikely; the crescentic collection in the immediate post-trauma setting is haemorrhage, not pus.
High-YieldNEET PG
A crescentic hypo-to-anechoic collection conforming to the splenic contour on FAST is subcapsular haematoma until proven otherwise in acute blunt trauma.
Sabiston Textbook of Surgery, 21st Edition, Chapter on Management of Trauma
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