Ultrasound detection of colonic polyps: perspective

Abstract

ABSTRACT. Colorectal cancer is often preventable if the precursor adenoma is detected and removed. Although ultrasound is clearly not one of the widely accepted screening techniques, this non-invasive and radiation-free modality is also capable of detecting colonic polyps, both benign and malignant. Such colon lesions may be encountered when not expected, usually during general abdominal sonography. The discovery of large colonic polyps is important and can potentially help reduce the incidence of a common cancer, whereas detection of a malignant polyp at an early stage may result in a curative intervention. This pictorial review highlights our experience of sonographic detection of colonic polyps in 43 adult patients encountered at our institutions over a 2-year period. 4 out of 50 discovered polyps were found to be malignant lesions, 3 polyps were hyperplastic, 1 polyp was a hamartomatous polyp and the rest were benign adenomas. The smallest of the detected polyps was 1.3 cm in diameter, the largest one was 4.0 cm (mean 1.7 cm; median 1.6 cm). In each case, polyps were discovered during a routine abdominal or pelvic examination, particularly when scanning was supplemented by a brief focused sonographic inspection of the colon with a 6-10 MHz linear transducer. In this paper, we illustrate the key sonographic features of different types of commonly encountered colonic polyps in the hope of encouraging more observers to detect these lesions, which may be subtle. Colorectal cancer is the second most frequent cause of cancer-related death in North America and western Europe [1]. Each of us is thought to have a 6% chance of developing colorectal carcinoma-yet it is preventable in the majority of individuals if the precursor adenoma is detected and removed [2][3][4][5]. Although several screening techniques already exist with varying capability and invasiveness, a large percentage of the population remains unscreened, largely due to poor patient acceptance of routine colorectal screening [6].Ultrasound is not one of the widely accepted screening techniques for detecting colonic polyps. However, transabdominal ultrasound has been shown to demonstrate benign colonic polyps of significant size in both children and adults, with a reported sensitivity of 28.6% and specificity of 99.4% for detection of polyps greater than 10 mm diameter in the adult population [7,8]. With the use of hydrocolonic sonography, as described by Limberg, an accuracy of 91% for detection of colonic polyps greater than 7 mm diameter may be achieved [9]. As a screening tool, however, neither conventional nor hydrocolonic ultrasound has gained wide clinical acceptance.This pictorial review highlights our experience of sonographic detection of 50 colonic polyps in 43 adult patients encountered at our institutions over a 2-year period (June 2009-June 2011). All polyps were subsequently confirmed by endoscopic removal and histological examination. Four out of fifty discovered polyps were found to be malignant lesions, three polyps were hyperplastic, o...

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