Improved Outcomes in Colon and Rectal Surgery part 14. Written by many of the worlds leading colorectal surgeons, this evidence-based text investigates the risks and benefits of colorectal surgeries. By using clinical pathways, algorithms, and case discussions, the authors identify the best practices for patient safety and positive outcomes to ensure that physicians correctly recognize potential problems and carefully manage complications | IMPROVED OUTCOMES IN COLON AND RECTAL SURGERY Figure Colon Cancer Liver Metastasis. US of the liver demonstrates an isoechoic mass with a hypoechoic peripheral halo. This target appearance can be seen in a variety of disease processes but is a common finding in metastatic colon cancer and hepatocellular carcinoma. Figure Normal Endoluminal Ultrasound. Figure Normal Layers of Colon on Intrarectal ultrasound Graphic representation of 5 layers . called to do so. The US beam will be completely reflected by bone and sufficiently scattered by air to thwart imaging distal to these substances. When the transmitted sound wave reflects off a moving target the returning echo will have a slightly different frequency the Doppler Effect . Doppler US capitalizes on this principle and allows the determination of direction and velocity of a mobile target. 250 The most frequent application for Doppler US is the detection and quantification of blood flow. Specifically Doppler US is extremely helpful in evaluating the upper and lower extremities for deep venous thrombosis. US has many advantages. It is an inexpensive widely available modality that provides real time multiplanar images with no radiation exposure to the patient. The US equipment is mobile allowing critically ill patients to be imaged within the ICU. The structures that can be studied by US include arteries veins liver spleen gallbladder bile ducts pancreas kidneys bladder uterus and ovaries. Transabdominal US is typically limited in its evaluation of the gastrointestinal tract. Intraluminal bowel gas will obscure the surrounding anatomy. Therefore patients should be NPO for 4 to 8 hours before being imaged to reduce the volume Figure Ultrasound of uT3 rectal mass. of intraluminal gas. 251 Nonetheless US can detect abnormal loops of bowel. Wall thickening hyperemia fecoliths bowel distention wall edema and noncompressibility all can be detected by ultrasound and suggest intestinal pathology. US .
