Abstract
Purpose: The purpose of this study was to retrospectively assess the detectability and enhancement pattern of rectal carcinoid tumors on contrast-enhanced computed tomography colonography (CE-CTC). Methods: The study sample consisted of 12 lesions in nine patients of rectal carcinoid tumors. To evaluate the detectability, two radiologists reviewed axial and 3D images including air enema (AE), virtual endoscopy (VE), and virtual colon dissection (VCD). To determine the contrast enhancement pattern of the tumors, the CT attenuation value of each lesion was measured in three phases. Results: Four of the 12 lesions (33%) were detected on axial images in patients in both the prone and supine positions, the sizes of which were 6 mm or larger. Seven lesions (58%), including the four lesions mentioned above, were detected on 3D images including AE and VE in patients in the prone position, the sizes of which were 5 mm or larger. The ranges of CT attenuation values of the lesions at 40 s, 70 s and 240 s were 112 - 147, 116 - 140 and 82 - 97 HU, respectively. Conclusion: Rectal carcinoid tumors are challenging to detect on CE-CTC. They demonstrated enhancement at the early phase and washout at the delayed phase on CE-CTC.
Highlights
Carcinoid tumors belong to the group of well-differentiated neuroendocrine tumors of neuroendocrine neoplasms in the World Health Organization (WHO) classification [1]
In one case with a 5 mm diameter lesion, the readers detected the tumor on air enema (AE) and virtual endoscopy (VE) taken in the prone position, but did not detect it on virtual colon dissection (VCD) with either the supine or prone position
All four lesions detected on the axial images (6 mm or larger) demonstrated enhancement at the early phase (40 s and 70 s), and washout at the delayed phase (240 s) (Figure 2)
Summary
Carcinoid tumors belong to the group of well-differentiated neuroendocrine tumors of neuroendocrine neoplasms in the World Health Organization (WHO) classification [1]. Rectal carcinoid tumors are uncommon, representing 1.1% to 1.3% of all rectal tumors [2] [3]. They can show a broad range of clinical behavior, from benign and asymptomatic to disseminated and metastatic. Clinical behavior is a reflection of tumor size, with me-. (2014) Contrast-Enhanced CT Colonography Features of Rectal Carcinoid Tumors. Rectal carcinoid tumors are usually found incidentally by rectal examination or endoscopy. Tumors smaller than 10 mm in diameter rarely metastasize, and have usually been managed with local excision including endoscopic treatment [7]-[9]
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