From the Guidelines
The sensitivity and specificity of subcapsular hematoma in renal ultrasound are 22-67% and 96-100%, respectively, making it a less reliable diagnostic tool compared to CT scan, which remains the gold standard with higher sensitivity and specificity. When evaluating suspected renal trauma or spontaneous subcapsular hematoma, ultrasound may serve as a useful initial screening tool due to its accessibility, lack of radiation, and ability to be performed at bedside 1. However, negative ultrasound findings should not exclude the diagnosis when clinical suspicion is high, and further imaging with CT should be considered. Some key points to consider when using ultrasound for diagnosing subcapsular hematoma include:
- Sensitivity is limited by several factors including small hematoma size, acute bleeding (which may be isoechoic initially), operator experience, and patient factors such as obesity or bowel gas 1.
- Ultrasound appears as an anechoic or hypoechoic crescent-shaped collection between the renal parenchyma and capsule.
- Serial ultrasound examinations may be valuable for monitoring known subcapsular hematomas, as the appearance changes over time with echogenicity increasing as the blood clot organizes.
- Contrast-enhanced US (CEUS) may increase the accuracy of ultrasound in stable patients with suspected renal injuries, but its use is not widely recommended 1. It is essential to note that CT scan with intravenous contrast is considered the gold standard in blunt and penetrating trauma, allowing for the identification of almost all injuries and the addition of a delayed phase permitting the identification of urinary extravasation 1.
From the Research
Sensitivity and Specificity of Subcapsular Hematoma in Renal Ultrasound
- The sensitivity and specificity of subcapsular hematoma in renal ultrasound are not directly reported in the provided studies 2, 3, 4, 5, 6.
- However, one study mentions that the sensitivity of bedside ultrasound in diagnosing subcapsular renal hematoma is low, and other imaging methods may be necessary to make the diagnosis 3.
- Another study highlights the importance of ultrasonography in detecting subcapsular hematomas, which can be a reversible cause of acute kidney injury and acute tubular necrosis in the setting of renal transplant 6.
- The provided studies focus on the incidence, risk factors, management, and clinical presentation of subcapsular renal hematoma, but do not provide specific data on the sensitivity and specificity of renal ultrasound in diagnosing this condition.
Diagnostic Accuracy of Renal Ultrasound
- Renal ultrasound is used as a diagnostic tool to detect subcapsular renal hematoma, but its accuracy is not well-established in the provided studies 2, 3, 4, 5, 6.
- One study reports that ultrasonography showed a hyperechoic subcapsular lesion along the right kidney, suggesting the diagnosis of subcapsular renal hematoma 3.
- Another study mentions that ultrasonography-guided drainage of the hematoma was performed in two patients with subcapsular renal hematoma 4.