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AAST Kidney Injury Scale Grading

The AAST Kidney Injury Scale Grading is a crucial tool in trauma care, enabling healthcare providers to assess the severity of kidney injuries and guide treatment decisions effectively. Developed by the American Association for the Surgery of Trauma (AAST), this scale categorizes kidney injuries into five grades, each with distinct characteristics and implications for patient management.

What is AAST Kidney Injury?

AAST kidney injury refers to damage to the kidney caused by blunt or penetrating trauma. The AAST grading system is widely used in trauma centers to classify these injuries based on their severity, which ranges from minor contusions to complete kidney destruction. This classification helps clinicians decide whether conservative management or surgical intervention is necessary.

The 2018 revision of the AAST Kidney Injury Grading Scale is detailed below.

AAST Kidney Injury Scale

Grade I AAST Kidney Injury

This is the least severe form of kidney injury, typically involving minor contusions or subcapsular hematomas without lacerations. These injuries are often managed conservatively without the need for surgical intervention.

• Subcapsular hematoma and/or contusion
• No laceration

Grade II AAST Kidney Injury

Injuries classified as Grade II involve non-expanding perirenal hematomas or superficial lacerations less than 1 cm in depth. Like Grade I injuries, these are usually managed non-surgically, with close monitoring.

• Superficial laceration ≤1 cm depth not involving the collecting system (no evidence of urine extravasation)
• Perirenal hematoma confined within the perirenal fascia

Grade III AAST Kidney Injury

Grade III injuries are characterized by lacerations greater than 1 cm in depth that do not involve the urinary collecting system. These injuries are more severe and may require more intensive monitoring or intervention depending on the patient’s overall condition.

• Laceration >1 cm not involving the collecting system (no evidence of urine extravasation)
• Vascular injury or active bleeding confined within the perirenal fascia

Grade IV AAST Kidney Injury

At this level, the injury involves lacerations extending into the urinary collecting system or injuries to the renal artery or vein. These injuries pose a higher risk of complications such as urinary leakage or significant blood loss, often necessitating surgical repair.

• Laceration involving the collecting system with urinary extravasation
• Laceration of the renal pelvis and/or complete ureteropelvic disruption
• Vascular injury to segmental renal artery or vein
• Segmental infarctions without associated active bleeding (i.e. due to vessel thrombosis)
• Active bleeding extending beyond the perirenal fascia (i.e. into the retroperitoneum or peritoneum)

Grade V AAST Kidney Injury

This is the most severe form of kidney injury, involving either a completely shattered kidney or avulsion of the renal hilum. Grade V injuries are life-threatening and typically require immediate surgical intervention to control bleeding and prevent further damage.
• Shattered kidney
• Avulsion of renal hilum or laceration of the main renal artery or vein: devascularization of a kidney due to hilar injury
• Devascularized kidney with active bleeding

Grading Notes

• Grade based on highest grade assessment made on imaging, at operation or, on pathologic specimen.
• There may be more than one grade of kidney injury and the injury should be classified based on the higher grade of injury.
• For multiple injuries, advance one grade up to grade III.

Management & Treatment Based on AAST Grading

The management of kidney injuries depends largely on the AAST grade. Lower-grade injuries (I-III) are generally managed conservatively with bed rest, fluid management, and close monitoring. Higher-grade injuries (IV-V), however, often require surgical intervention to repair damaged tissues and control hemorrhage. The decision between conservative management and surgery is guided by the severity of the injury, the patient’s hemodynamic stability, and the presence of other injuries.

Prognosis & Outcomes

The prognosis of kidney injuries varies according to the AAST grade. Lower-grade injuries typically have a good prognosis with conservative management, while higher-grade injuries carry a higher risk of complications such as chronic kidney disease, hypertension, or even kidney loss. The long-term outcomes depend on the extent of the injury and the effectiveness of the initial treatment.

Key Takeaways

The AAST kidney injury scale is an essential tool for trauma surgeons and emergency physicians, providing a clear framework for assessing kidney injuries and guiding treatment. By understanding the grading system and its implications for patient care, healthcare providers can make informed decisions that improve outcomes for trauma patients.

Learn more on the BackTable VI Podcast

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Ep 183 Solid Organ & Pelvic Trauma with Dr. Chris Ingraham

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