**2.2 Kidney**

Kidney is a retroperitoneal organ well visualized by ultrasonography. For visualizing the right kidney, the transducer is placed in the mid axillary line at the right costal margin and moved caudally till the kidney comes into view. The maximum length is identified by turning the probe obliquely and this plane marks the longitudinal axis of the kidney. The parenchyma is scanned by fanning the transducer in anterior and posterior directions. The transducer is then rotated 90 degrees to obtain a transverse view. The probe is tilted superiorly and inferiorly to examine the upper pole, hilum, and lower pole. The longitudinal view of the left kidney is visualized by placing the transducer in the posterior axillary line at the left costal margin and then moving caudally. The remaining views are obtained the same way as for the right kidney.

Major renal injury markers on ultrasonography are subcapsular hematoma, perinephric hematoma, and calyceal dilatation with internal echogenicity. Mixed echogenic material with disorganized renal architecture can be seen high-grade renal injury, such as fractured kidney with retroperitoneal hematoma (**Figure 5**). Fresh parenchymal hematoma on POCUS will be isoechoic and difficult to identify. Over

**Figure 5.** *High grade renal injury on USG with completely disrupted architecture [14].*

time, it will become hypoechoic and easier to locate. The additional role of bedside ultrasonography includes follow-up of patients with these findings for resolution. It helps avoid repetitive radiation exposures and high costs.

Renal vascular injuries are identified by carefully scanning the hilum for abnormal Doppler flow. Segmental infarcts of the cortex are confirmed by the absence of perfusion on scanning.

#### **2.3 Pancreas**

Semierect patient position is preferred if possible to avoid interference from bowel gas. The left lobe of liver and spleen provide an acoustic window to visualize the pancreas. The transducer is placed in sagittal and transverse planes along the vascular landmarks. In the transverse plane, the pancreas is seen beneath the left lobe of the liver and crossing above the abdominal aorta and inferior vena cava and the splenic artery acts landmark as it runs along its posterior surface. In the sagittal plane, tthe tail of the pancreas is usually seen with a coronal view in a right posterior oblique position. The pancreatic duct is seen within the body of the pancreas seen as a tubular structure with reflective walls and a maximum diameter of 2 mm. Normal echotexture of the pancreas is similar to or more echoic than the adjacent liver.

When edema develops in the pancreas, the echogenicity reduces. Traumatic pancreatitis may be identified when it becomes a heterogeneous mass with an ill-defined border. There may be hypoechoic or anechoic collection around the pancreas due to bleeding or exudation. Rarely, pancreatic duct disruption can be detected (**Figure 6**).

#### **2.4 Newer modalities/techniques**

#### *2.4.1 Contrast-enhanced ultrasonography*

Solid organ injury can be detected by POCUS. Imaging can be augmented by contrast-enhanced ultrasonography. Second-generation contrast agents have been introduced that contain perflutren microbubbles that can cross the pulmonary capillaries and enter into the systemic circulation. The microbubbles vibrate with the high-frequency waves generated by ultrasonography probes, which in turn makes them more reflective than normal tissue (**Figure 7**).

#### **Figure 6.** *Pancreatic injury on USG seen as nonhomogeneous echotexture [15].*

#### **Figure 7.**

*Liver injury on traditional sonography (A) as hypoechoic lesion on right lobe (arrow), on contrast-enhanced USG (B) as extended liver rupture (arrows) and on CT (C), which confirmed the rupture (white arrow) [16].*

In injuries to liver, spleen, and kidney, contrast-enhanced sonography images have been studied to allow better detection of injury extent compared to traditional sonography [16, 17].
