Features of internal organ injuries
Unlike adults, the abdominal organs in children exhibit different injury biomechanics during trauma:
- Kidneys: Injured very frequently. Due to high mobility and poorly developed protective adipose tissue, rapid deceleration leads to severe injuries of the vascular pedicle and collecting system.
- Bowel and pancreas: Injured relatively rarely. As a rule, their injury occurs from a direct impact (e.g., a bicycle handlebar to the abdomen) or as a result of organ compression between the offending agent and the spine.
- Ribs: The growing pediatric skeleton possesses high elasticity. Therefore, the ribs can bend significantly, transferring the impact energy to internal organ structures, while the bone fractures themselves may not be visualized on radiographs or CT scans.
Important: When evaluating any abdominal trauma in a child, the radiologist must always keep in mind the possibility of non-accidental injury (non-accidental injury, NAI / battered child syndrome).
High-risk markers and shock
Certain clinical and radiological patterns require immediate attention as they indicate life-threatening conditions.
Seatbelt sign The presence of ecchymoses from a lap belt is a crucial marker of high risk for lumbar spine, bladder, and bowel injuries. In young children, the center of gravity is positioned relatively high, which causes powerful shearing forces during deceleration.
Hypoperfusion complex ("shock bowel" / shock bowel) This is a manifestation of poorly compensated hypovolemic shock, which occurs significantly more often in children than in adults.
- Manifestation: Bowel loops are dilated and fluid-filled.
- CT appearance: Intense mucosal enhancement and bowel wall thickening are observed. The kidneys and major abdominal vessels also demonstrate avid contrast accumulation. Meanwhile, the caliber of the aorta and inferior vena cava (IVC) is reduced. Contrast enhancement of the pancreas and spleen is decreased, which is explained by pronounced visceral splanchnic vasoconstriction.
Liver ultrasound (US)
Ultrasound requires a systematic approach and the correct choice of transducers for a detailed evaluation of the parenchyma.
- B-mode (Grey-scale US):
- High-frequency linear transducer (e.g., 9.5 MHz): Optimal for examining the liver surface (evaluating nodularity in cirrhosis), searching for small focal lesions, and assessing diffuse changes. For example, in a child with neutropenia and fever, small fungal microabscesses can easily be missed on a low-frequency curved array transducer (5–2 MHz), but they are clearly visible on a linear transducer. In congenital hepatic fibrosis, this transducer reveals echogenic lacy bands (often associated with enlarged polycystic kidneys).
- Curved/vector transducer: Necessary for evaluating deep structures in older children.
- Low-frequency transducers: Used in the presence of dense, pronounced fibrosis.
- Color Doppler imaging (CDI / Colour Doppler): An essential addition. It allows for the evaluation of hepatic vessels (artery, veins, portal vein), detection of collaterals (cavernous transformation, recanalization of fetal veins in portal hypertension), and varices.
- Pulsed-wave Doppler (Pulsed-wave Doppler): Routinely evaluates blood flow in the portal vein. If the child is moving and obtaining a spectrum is difficult, CDI will at least demonstrate the direction of blood flow.
- Twinkling artifact (Twinkling artefact): Assists in searching for calcifications, biliary hamartomas, and stones. Sensitivity is higher if the focal zone is set deeper than the lesion, and the colour write priority is increased.
Magnetic resonance imaging (MRI)
Provided proper preparation is ensured, MRI provides high-contrast imaging with submillimeter isotropic resolution. A mandatory requirement is the use of respiratory gating (respiratory gating).
The most useful pulse sequences for liver scanning:
- STIR (short tau inversion recovery fast spin-echo) — short tau inversion recovery fast spin-echo.
- Volumetric T2-weighted spin-echo with variable refocusing flip angles (sequences such as CUBE, SPACE, VISTA).
- In-phase and opposed-phase spoiled gradient-echo (in-phase and opposed-phase spoiled gradient-echo).
- Diffusion-weighted imaging (DWI / diffusion-weighted imaging).
Briefly: answers to topical questions
What grading scale is used to classify traumatic renal injury severity on CT?
Traumatic renal injuries on CT are graded using the AAST scale. The original 1989 classification version was based on surgical findings. The 2011 revision incorporates MDCT radiological data, includes segmental vascular injuries and pelviureteral junction avulsions, and was performed to resolve discrepancies and standardize the classification. Grades I–III remained unchanged; these injury grades are typically managed conservatively. Grades IV–V were revised. Accurate injury severity classification based on MSCT data determines management tactics.
What are the indications for performing a FAST ultrasound protocol in blunt abdominal trauma in children?
Ultrasound, including the FAST protocol, is useful for detecting free fluid in the peritoneal cavity. In renal trauma, ultrasound has low sensitivity, except in pediatric practice. The method is limited in evaluating the retroperitoneal space.
To recognize the CT appearance of "shock bowel," remember blood redistribution: "The aorta is collapsed, the bowel and kidneys glow with contrast, and the spleen is in the shadow." This is a visual reflection of pronounced vasoconstriction and hypovolemia.
Class and exam questions
Why are rib fractures rarely seen in pediatric abdominal trauma?
The growing pediatric skeleton possesses high elasticity. Ribs can deform and bend inward significantly, injuring internal organs, without disrupting their own bone structure.
What does the "seatbelt sign" on a child's abdomen indicate?
Ecchymoses from the seatbelt indicate exposure to strong shearing forces. This is a marker of an extremely high risk of concomitant injuries to the bowel, urinary bladder, and lumbar spine.
Which ultrasound transducer is best for searching for small fungal microabscesses in the liver?
To search for small focal lesions and evaluate the liver surface, a high-frequency linear transducer (e.g., 9.5 MHz) is optimal. Low-frequency transducers may lack sufficient resolution.
What is "shock bowel"?
This is a CT pattern of poorly compensated hypovolemic shock. It manifests as dilated bowel loops, intense enhancement of the thickened mucosa, narrowing of the aorta, and decreased contrast accumulation in the spleen due to vascular spasm.
What else to study on this topic
- Pathophysiology of shearing forces in blunt abdominal trauma in children.
- Imaging signs and differential diagnosis of non-accidental injury (NAI).
- Concomitant pathology: congenital hepatic fibrosis and polycystic kidney disease.
- Optimizing ultrasound machine settings to enhance the twinkling artifact.
- Assessment of portal hypertension: cavernous transformation and recanalization of fetal veins.
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