Bound Technique Essay

ULTRASOUND TECHNIQUE

Dr Charles B.S. Tsang,
MBBS, M.Med(Surg), MS(Exp.Surg),FRCS(Ed), FRCS(Glasg), FAMS

Head and Senior Consultant Surgeon, Division of Colorectal Surgery,

University Surgical Cluster,

National University Health System, SINGAPORE

Endorectal Ultrasound

We use the following equipment:

1. BK Medical Profocus® scanner with a 2052 probe. 2. Karl Storz rigid sigmoidoscope with a length of 20 cm and inner diameter of 22 mm. 3. Suction equipment 4. Normal saline to irrigate rectum if necessary 5. Boiled water to fill rectal balloon 6. 100 cc syringe with a Luer lock to connect to water standoff fitted over shaft of 2052 probe

We currently use a 2052 probe from BK Medical.
The right lateral aspect of the rectum will be on the left side of the screen. Likewise, the left lateral aspect of the rectum will be on the right side of the screen. The transducer position is adjusted to maintain a central location within the rectal lumen to obtain optimal imaging of the rectal wall and perirectal structures. The gain in the ultrasound unit is also adjusted to obtain optimal imaging. When optimal, it should be possible to visualize clearly all five layers of the rectal wall. Once this is achieved, the transducer within the 2052 probe is gradually moved caudad using the Up/Down motor buttons situated at the base of the probe. The rectal wall layers and surrounding structures are carefully observed. We also perform a 3D scan by activating the 3D button on the console. During a 3D scan, the transducer is automatically moved from the tip of the 2052 probe over a distance of 6 cm. A series of 2D axial images are captured by the computer onboard and reconstructed into a 3D volume rendered image. The entire length of the rectal tumor is carefully examined. As such, it may be necessary to make several passes along the full length of the tumor to get all the necessary information. As the 2052 probe is a 3D probe, the transducer is moved
Any sphincter defects are recorded. In females, the perineal body measurement is performed. With the gloved right index finger in the vagina, the probe is positioned in the midanal canal using the left hand. The image on the screen is then freezed and the distance between the inner aspect of the internal sphincter is measured to the hyperechoeic line representing the finger-vagina interface. The perineal body measurement gives a good estimate of the thickness of the anal sphincter complex anteriorly. It is attenuated in the presence of sphincter deficiencies.

Any hypoechoeic collection or tract representing anorectal sepsis is followed proximally and distally to identify its location and orientation according to the Park’s classification. When a fistula is suspected and an external opening is present, hydrogen peroxide is used as a contrast to help enhance the fistula tract. We place a 21 G IV cannula into the external opening and inject 1-2 cc of H2O2. The bubbles that form within the fistula tract results in a hyperechoeic signal. This tract is then easily followed to its internal opening.