How useful is rectal endosonography in the staging of rectal cancer?

Figure 1 Normal endorectal sonogram image acquired by flexible echoendoscope. The layers of the rectum are as follows: hyperechoic mucosa (m), hypoechoic muscularis mucosa (mm), hyperechoic submucosa (sm), hypoechoic muscularis propria (mp), and hyperechoic serosa (s).

Figure 2 Endorectal ultrasound (ERUS) image. A: A rectal carcinoma that appears to be T1 (penetration into submucosa) in one part (arrowheads show intact muscularis propria) and T2 (penetration into muscularis propria-arrows) in another part; B: A T3 rectal adenocarcinoma. Arrowheads show that the lesion penetrated into perirectal fat; C: A locally invasive cervical cancer, which invaded the rectum (arrows show tumor breach).