DOI: 10.1148/rg.246045063
Differential Diagnosis of Polypoid Lesions Seen at CT Colonography (Virtual Colonoscopy)1
Perry J. Pickhardt, MD
1 From the Department of Radiology, University of Wisconsin Medical School, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792; and Department of Radiology, Uniformed Services University of the Health Sciences, Bethesda, Md. Recipient of a Cum Laude award for an education exhibit at the 2003 RSNA scientific assembly. Received April 2, 2004; revision requested May 5 and received June 10; accepted June 11. As of April 28, 2004, the author became a medical consultant for Viatronix, Inc. Address correspondence to the author (e-mail: ppickhardt@mail.radiology.wisc.edu).
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Figure 1. Schematic map of the colon generated by CT colonography software. The Viatronix V3D Colon system automatically isolates the air-filled colon and rectum and generates an endoluminal centerline (green line), which helps allow for time-efficient primary 3D evaluation. Red dot indicates a "bookmark" where a polyp was located.
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Figure 2a. Tubular adenoma. (a) Endoluminal 3D view from CT colonography shows a rounded, 6-mm sessile polyp located on a colonic fold. (b) Digital photograph from same-day optical colonoscopy shows the matching sessile polyp.
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Figure 2b. Tubular adenoma. (a) Endoluminal 3D view from CT colonography shows a rounded, 6-mm sessile polyp located on a colonic fold. (b) Digital photograph from same-day optical colonoscopy shows the matching sessile polyp.
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Figure 3a. Tubulovillous adenoma. (a) Endoluminal 3D view from CT colonography shows a sessile, lobulated 20-mm polyp extending from a colonic fold. (b) Digital photograph from optical colonoscopy shows the same lobulated lesion. Note the adjacent calibrated guidewire, which provides more accurate endoscopic measurement than open biopsy forceps estimation.
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Figure 3b. Tubulovillous adenoma. (a) Endoluminal 3D view from CT colonography shows a sessile, lobulated 20-mm polyp extending from a colonic fold. (b) Digital photograph from optical colonoscopy shows the same lobulated lesion. Note the adjacent calibrated guidewire, which provides more accurate endoscopic measurement than open biopsy forceps estimation.
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Figure 4a. Tubulovillous adenoma. (a) Endoluminal 3D view from CT colonography shows a 10-mm pedunculated polyp with a well-defined stalk. (b) Axial 2D view shows the same pedunculated polyp (arrowhead). Unlike most other pedunculated lesions, which are more easily recognized as such on 3D views, the stalk and polyp in this case happen to be aligned in a standard 2D plane.
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Figure 4b. Tubulovillous adenoma. (a) Endoluminal 3D view from CT colonography shows a 10-mm pedunculated polyp with a well-defined stalk. (b) Axial 2D view shows the same pedunculated polyp (arrowhead). Unlike most other pedunculated lesions, which are more easily recognized as such on 3D views, the stalk and polyp in this case happen to be aligned in a standard 2D plane.
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Figure 5a. Villous adenoma. (a) Endoluminal 3D view from CT colonography shows a 5-cm irregular cecal mass. This papillary appearance is highly suggestive of a villous tumor. (b) Axial 2D image (without electronic cleansing of opacified fluid) shows the same irregular cecal mass (arrowheads). (c) Digital photograph from optical colonoscopy shows the papillary, frondlike nature of the mass to greater advantage. The lesion was not malignant despite its large size.
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Figure 5b. Villous adenoma. (a) Endoluminal 3D view from CT colonography shows a 5-cm irregular cecal mass. This papillary appearance is highly suggestive of a villous tumor. (b) Axial 2D image (without electronic cleansing of opacified fluid) shows the same irregular cecal mass (arrowheads). (c) Digital photograph from optical colonoscopy shows the papillary, frondlike nature of the mass to greater advantage. The lesion was not malignant despite its large size.
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Figure 5c. Villous adenoma. (a) Endoluminal 3D view from CT colonography shows a 5-cm irregular cecal mass. This papillary appearance is highly suggestive of a villous tumor. (b) Axial 2D image (without electronic cleansing of opacified fluid) shows the same irregular cecal mass (arrowheads). (c) Digital photograph from optical colonoscopy shows the papillary, frondlike nature of the mass to greater advantage. The lesion was not malignant despite its large size.
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Figure 6a. Flat adenoma. (a) Endoluminal 3D view from CT colonography shows a relatively subtle flat lesion (arrowheads) near the anal verge. This adenoma was missed at prospective colonoscopy before the CT colonographic results were revealed. (b) Corresponding axial 2D image helps confirm a flat rectal lesion (arrow).
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Figure 6b. Flat adenoma. (a) Endoluminal 3D view from CT colonography shows a relatively subtle flat lesion (arrowheads) near the anal verge. This adenoma was missed at prospective colonoscopy before the CT colonographic results were revealed. (b) Corresponding axial 2D image helps confirm a flat rectal lesion (arrow).
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Figure 7a. Malignant polyp. (7a) Axial 2D view shows a relatively flat 4-cm mass in the cecum. (7b) Digital photograph from optical colonoscopy shows the same polypoid mass, which was malignant but not yet invasive at histologic evaluation.
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Figure 7b. Malignant polyp. (7a) Axial 2D view shows a relatively flat 4-cm mass in the cecum. (7b) Digital photograph from optical colonoscopy shows the same polypoid mass, which was malignant but not yet invasive at histologic evaluation.
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Figure 8. Malignant polyp. Endoluminal 3D view from CT colonography in a symptomatic patient shows a large sessile mass, which proved to be malignant.
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Figure 9a. Invasive adenocarcinoma. (a) Contrast material-enhanced 2D curved reformatted image with soft-tissue windowing shows an annular-constricting mass with shouldering (arrowheads) involving the sigmoid colon. Cross-sectional 2D views are much more effective than endoluminal displays for depicting invasive mass lesions. (b) Digital photograph from optical colonoscopy shows the proximal aspect of the mass.
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Figure 9b. Invasive adenocarcinoma. (a) Contrast material-enhanced 2D curved reformatted image with soft-tissue windowing shows an annular-constricting mass with shouldering (arrowheads) involving the sigmoid colon. Cross-sectional 2D views are much more effective than endoluminal displays for depicting invasive mass lesions. (b) Digital photograph from optical colonoscopy shows the proximal aspect of the mass.
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Figure 10a. Occlusive adenocarcinoma. (a) Contrast-enhanced 2D coronal CT image with soft-tissue windowing shows an annular sigmoid mass (arrowheads). The endoscope could not be passed beyond the lesion to evaluate the proximal colon. (b) Endoluminal 3D view from CT colonography shows a synchronous 15-mm polyp on a fold in the ascending colon. Although the 2D views are better for evaluating the invasive primary tumor, 3D views remain valuable for detecting proximal synchronous lesions.
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Figure 10b. Occlusive adenocarcinoma. (a) Contrast-enhanced 2D coronal CT image with soft-tissue windowing shows an annular sigmoid mass (arrowheads). The endoscope could not be passed beyond the lesion to evaluate the proximal colon. (b) Endoluminal 3D view from CT colonography shows a synchronous 15-mm polyp on a fold in the ascending colon. Although the 2D views are better for evaluating the invasive primary tumor, 3D views remain valuable for detecting proximal synchronous lesions.
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Figure 11a. Familial adenomatous polyposis syndrome with adenocarcinoma. (a) Contrast-enhanced 2D axial CT image shows a large irregular soft-tissue mass in the ascending colon (arrowheads). The CT study was performed as a routine examination without colonic preparation. (b) Digital photograph from subsequent optical colonoscopy shows the large mass seen in a, which proved to be malignant at histologic evaluation. (c) Axial CT image obtained caudad to a shows additional smaller polypoid lesions (arrowheads), which might be difficult to distinguish from stool on this CT scan obtained without colonic cleansing. (d) Digital photograph from optical colonoscopy shows multiple polyps in the transverse colon.
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Figure 11b. Familial adenomatous polyposis syndrome with adenocarcinoma. (a) Contrast-enhanced 2D axial CT image shows a large irregular soft-tissue mass in the ascending colon (arrowheads). The CT study was performed as a routine examination without colonic preparation. (b) Digital photograph from subsequent optical colonoscopy shows the large mass seen in a, which proved to be malignant at histologic evaluation. (c) Axial CT image obtained caudad to a shows additional smaller polypoid lesions (arrowheads), which might be difficult to distinguish from stool on this CT scan obtained without colonic cleansing. (d) Digital photograph from optical colonoscopy shows multiple polyps in the transverse colon.
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Figure 11c. Familial adenomatous polyposis syndrome with adenocarcinoma. (a) Contrast-enhanced 2D axial CT image shows a large irregular soft-tissue mass in the ascending colon (arrowheads). The CT study was performed as a routine examination without colonic preparation. (b) Digital photograph from subsequent optical colonoscopy shows the large mass seen in a, which proved to be malignant at histologic evaluation. (c) Axial CT image obtained caudad to a shows additional smaller polypoid lesions (arrowheads), which might be difficult to distinguish from stool on this CT scan obtained without colonic cleansing. (d) Digital photograph from optical colonoscopy shows multiple polyps in the transverse colon.
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Figure 11d. Familial adenomatous polyposis syndrome with adenocarcinoma. (a) Contrast-enhanced 2D axial CT image shows a large irregular soft-tissue mass in the ascending colon (arrowheads). The CT study was performed as a routine examination without colonic preparation. (b) Digital photograph from subsequent optical colonoscopy shows the large mass seen in a, which proved to be malignant at histologic evaluation. (c) Axial CT image obtained caudad to a shows additional smaller polypoid lesions (arrowheads), which might be difficult to distinguish from stool on this CT scan obtained without colonic cleansing. (d) Digital photograph from optical colonoscopy shows multiple polyps in the transverse colon.
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Figure 12a. Hyperplastic polyp. (a) Endoluminal 3D view from CT colonography shows a 7-mm sessile soft-tissue lesion, which is indistinguishable from an adenomatous polyp. (b) Digital photograph from optical colonoscopy shows the same sessile polyp. Reliable distinction from an adenomatous polyp requires histologic analysis.
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Figure 12b. Hyperplastic polyp. (a) Endoluminal 3D view from CT colonography shows a 7-mm sessile soft-tissue lesion, which is indistinguishable from an adenomatous polyp. (b) Digital photograph from optical colonoscopy shows the same sessile polyp. Reliable distinction from an adenomatous polyp requires histologic analysis.
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Figure 13a. Hyperplastic polyp. (a) Endoluminal 3D view shows a large 11-mm sessile polyp. Bulky hyperplastic lesions of this size are relatively rare. (b) Digital photograph from optical colonoscopy shows the same hyperplastic polyp.
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Figure 13b. Hyperplastic polyp. (a) Endoluminal 3D view shows a large 11-mm sessile polyp. Bulky hyperplastic lesions of this size are relatively rare. (b) Digital photograph from optical colonoscopy shows the same hyperplastic polyp.
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Figure 14. Hyperplastic polyp. Digital photograph from optical colonoscopy shows a large irregular, flat 20-mm lesion (arrowheads) that was seen at CT colonography but only in retrospect. Most lesions with this appearance are fortunately hyperplastic in our experience.
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Figure 15a. Mucosal polyp (normal epithelium). (a) Endoluminal 3D view from CT colonography that simulates a retroflexed rectal view at colonoscopy shows a tiny 3-mm polyp (arrow). Note tip of a rectal catheter. Almost all mucosal polyps are diminutive and therefore will not influence management. (b) Digital photograph from optical colonoscopy shows measurement of the diminutive 3-mm lesion with the calibrated wire.
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Figure 15b. Mucosal polyp (normal epithelium). (a) Endoluminal 3D view from CT colonography that simulates a retroflexed rectal view at colonoscopy shows a tiny 3-mm polyp (arrow). Note tip of a rectal catheter. Almost all mucosal polyps are diminutive and therefore will not influence management. (b) Digital photograph from optical colonoscopy shows measurement of the diminutive 3-mm lesion with the calibrated wire.
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Figure 16a. Juvenile polyp. (a) Endoluminal 3D view from CT colonography in an asymptomatic 57-year-old man shows a pedunculated 15-mm polyp extending from a fold in the rectosigmoid region. The polyp was a solitary finding in this case. (b) Digital photograph from optical colonoscopy shows the same polyp. (Reprinted, with permission, from reference 21.)
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Figure 16b. Juvenile polyp. (a) Endoluminal 3D view from CT colonography in an asymptomatic 57-year-old man shows a pedunculated 15-mm polyp extending from a fold in the rectosigmoid region. The polyp was a solitary finding in this case. (b) Digital photograph from optical colonoscopy shows the same polyp. (Reprinted, with permission, from reference 21.)
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Figure 17a. Inflammatory polyp. (a) Endoluminal 3D view from CT colonography shows a small sessile polyp adjacent to a fold (arrow). (b) Digital image from optical colonoscopy shows a pale, fibrinous cap to this sessile lesion, which is suggestive of an inflammatory "cap" polyp.
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Figure 17b. Inflammatory polyp. (a) Endoluminal 3D view from CT colonography shows a small sessile polyp adjacent to a fold (arrow). (b) Digital image from optical colonoscopy shows a pale, fibrinous cap to this sessile lesion, which is suggestive of an inflammatory "cap" polyp.
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Figure 18. Peutz-Jeghers syndrome. Digital photograph from optical colonoscopy shows multiple hamartomatous polyps, which were also present in the small bowel.
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Figure 19. Cowden disease. Digital photograph from a retroflexed rectal view at optical colonoscopy shows innumerable small hamartomatous polyps.
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Figure 20. Cronkhite-Canada polyp. Endoluminal 3D view from CT colonography in an asymptomatic patient shows a sessile polyp (arrowhead) that was believed to have Cronkhite-Canada histologic characteristics. The patient did not have the associated clinical syndrome.
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Figure 21a. Lymphoid polyps. (a) Endoluminal 3D view from CT colonography shows multiple small polypoid lesions (arrowheads). These lymphoid aggregates are typically diminutive and therefore do not affect patient management. (b) Digital photograph from optical colonoscopy shows one of these lesions in the foreground.
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Figure 21b. Lymphoid polyps. (a) Endoluminal 3D view from CT colonography shows multiple small polypoid lesions (arrowheads). These lymphoid aggregates are typically diminutive and therefore do not affect patient management. (b) Digital photograph from optical colonoscopy shows one of these lesions in the foreground.
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Figure 22. Colonic posttransplantation lymphoproliferative disorder (PTLD). Contrast-enhanced CT scan of a lung transplant recipient shows large polypoid masses (arrowheads) in the sigmoid colon. PTLD was proved at colonoscopy and subsequent surgical resection.
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Figure 23a. Colonic lipoma. (a) Endoluminal 3D view from CT colonography shows a large polyp extending from a fold. (b) Axial 2D view with soft-tissue windowing shows that the lesion has fat attenuation (arrowhead), a finding diagnostic of a lipoma. (c) Digital photograph from optical colonoscopy shows the same lipoma.
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Figure 23b. Colonic lipoma. (a) Endoluminal 3D view from CT colonography shows a large polyp extending from a fold. (b) Axial 2D view with soft-tissue windowing shows that the lesion has fat attenuation (arrowhead), a finding diagnostic of a lipoma. (c) Digital photograph from optical colonoscopy shows the same lipoma.
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Figure 23c. Colonic lipoma. (a) Endoluminal 3D view from CT colonography shows a large polyp extending from a fold. (b) Axial 2D view with soft-tissue windowing shows that the lesion has fat attenuation (arrowhead), a finding diagnostic of a lipoma. (c) Digital photograph from optical colonoscopy shows the same lipoma.
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Figure 24. Rectal carcinoid tumor. Endoluminal 3D view from CT colonography shows a smooth, broad-based polypoid lesion (arrowhead). Note tip of a rectal catheter (arrow).
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Figure 25a. Rectal gastrointestinal stromal tumor. (a) Axial 2D view from CT colonography with soft-tissue windowing shows a mass (arrowhead) in the posterior rectum. (b) Endoluminal 3D view shows a broad-based impression (arrowheads) in the rectal lumen, adjacent to the anal verge. Note tip of a rectal catheter. (c) Digital photograph from optical colonoscopy shows the similar broad-based impression (arrowheads), which was initially disregarded until the CT colonographic findings were revealed.
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Figure 25b. Rectal gastrointestinal stromal tumor. (a) Axial 2D view from CT colonography with soft-tissue windowing shows a mass (arrowhead) in the posterior rectum. (b) Endoluminal 3D view shows a broad-based impression (arrowheads) in the rectal lumen, adjacent to the anal verge. Note tip of a rectal catheter. (c) Digital photograph from optical colonoscopy shows the similar broad-based impression (arrowheads), which was initially disregarded until the CT colonographic findings were revealed.
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Figure 25c. Rectal gastrointestinal stromal tumor. (a) Axial 2D view from CT colonography with soft-tissue windowing shows a mass (arrowhead) in the posterior rectum. (b) Endoluminal 3D view shows a broad-based impression (arrowheads) in the rectal lumen, adjacent to the anal verge. Note tip of a rectal catheter. (c) Digital photograph from optical colonoscopy shows the similar broad-based impression (arrowheads), which was initially disregarded until the CT colonographic findings were revealed.
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Figure 26. Colitis cystica profunda. Digital photograph from colonoscopy shows multiple large irregular lesions involving the rectum that represent dilated mucus-filled submucosal glands.
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Figure 27. Pneumatosis cystoides coli. Digital photograph from colonoscopy shows multiple large polypoid masses involving the entire visualized colonic surface. (Reprinted, with permission, from reference 25.)
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Figure 28a. Pneumatosis cystoides coli. (a) Endoluminal 3D view from CT colonography shows multiple polypoid lesions. Note that some lesions are "shelled out" and appear more like diverticula. (b) Axial 2D image shows that these lesions all represent thin-walled, air-filled cysts. Localized subserosal dissection of air surrounds this bowel loop, but no free intraperitoneal air was present.
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Figure 28b. Pneumatosis cystoides coli. (a) Endoluminal 3D view from CT colonography shows multiple polypoid lesions. Note that some lesions are "shelled out" and appear more like diverticula. (b) Axial 2D image shows that these lesions all represent thin-walled, air-filled cysts. Localized subserosal dissection of air surrounds this bowel loop, but no free intraperitoneal air was present.
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Figure 29a. Exophytic hepatic cavernous hemangioma causing extrinsic impression on the hepatic flexure. (a) Endoluminal 3D view from CT colonography shows a large rounded, broad-based impression (arrows) in the colonic lumen. Note the "continuous fold sign," consisting of a preserved but displaced haustral fold (arrowheads). (b) Axial 2D image from CT colonography elucidates the extrinsic nature of the mass lesion (*). Note the displaced haustral fold (arrowhead). (c) Contrast-enhanced axial CT image shows a cavernous hemangioma of the liver.
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Figure 29b. Exophytic hepatic cavernous hemangioma causing extrinsic impression on the hepatic flexure. (a) Endoluminal 3D view from CT colonography shows a large rounded, broad-based impression (arrows) in the colonic lumen. Note the "continuous fold sign," consisting of a preserved but displaced haustral fold (arrowheads). (b) Axial 2D image from CT colonography elucidates the extrinsic nature of the mass lesion (*). Note the displaced haustral fold (arrowhead). (c) Contrast-enhanced axial CT image shows a cavernous hemangioma of the liver.
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Figure 29c. Exophytic hepatic cavernous hemangioma causing extrinsic impression on the hepatic flexure. (a) Endoluminal 3D view from CT colonography shows a large rounded, broad-based impression (arrows) in the colonic lumen. Note the "continuous fold sign," consisting of a preserved but displaced haustral fold (arrowheads). (b) Axial 2D image from CT colonography elucidates the extrinsic nature of the mass lesion (*). Note the displaced haustral fold (arrowhead). (c) Contrast-enhanced axial CT image shows a cavernous hemangioma of the liver.
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Figure 30a. Appendiceal mucocele from mucinous adenoma. (a) Contrast-enhanced axial CT image shows a large, elongated low-attenuation mass (*) in the expected region of the appendix that bulges into the cecal lumen (arrowhead). (b) Digital photograph from optical colonoscopy shows only the luminal component of the appendiceal mucocele.
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Figure 30b. Appendiceal mucocele from mucinous adenoma. (a) Contrast-enhanced axial CT image shows a large, elongated low-attenuation mass (*) in the expected region of the appendix that bulges into the cecal lumen (arrowhead). (b) Digital photograph from optical colonoscopy shows only the luminal component of the appendiceal mucocele.
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Figure 31a. Intussusception. (a) Contrast-enhanced axial CT image shows a rounded low-attenuation lesion (arrowhead) near the ileocecal junction that represents intussusception of an ileal neurofibroma. (b) Digital photograph from optical colonoscopy shows the ileal neurofibroma. Intussusception into the cecum had spontaneously reduced in the interval.
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Figure 31b. Intussusception. (a) Contrast-enhanced axial CT image shows a rounded low-attenuation lesion (arrowhead) near the ileocecal junction that represents intussusception of an ileal neurofibroma. (b) Digital photograph from optical colonoscopy shows the ileal neurofibroma. Intussusception into the cecum had spontaneously reduced in the interval.
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Figure 32a. Internal hemorrhoids. (a) Endoluminal 3D view from CT colonography shows a large, circumferential mass at the anorectal junction that surrounds the rectal catheter. (b) Digital photograph from optical colonoscopy shows internal hemorrhoids, which are at least partially thrombosed, surrounding the colonoscope. Most cases are not this prominent.
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Figure 32b. Internal hemorrhoids. (a) Endoluminal 3D view from CT colonography shows a large, circumferential mass at the anorectal junction that surrounds the rectal catheter. (b) Digital photograph from optical colonoscopy shows internal hemorrhoids, which are at least partially thrombosed, surrounding the colonoscope. Most cases are not this prominent.
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Figure 33. Hypertrophied anal papilla. Endoluminal 3D view from CT colonography shows two, rounded polypoid lesions at or near the anal verge. If no other large polyps are seen proximally, suspected anal papillae can be confirmed with simple anoscopy or a digital rectal examination.
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Figure 34. Hypertrophied anal papilla. Digital photograph from optical colonoscopy shows endoscopic appearance of an anal papilla.
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Figure 35. Polypoid variant of solitary rectal ulcer syndrome. Digital photograph from optical colonoscopy shows an irregular polypoid rectal lesion.
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Figure 36a. Adenomatous polyp near the anal verge. (a) Endoluminal 3D view from CT colonography shows a 12-mm sessile polyp near but not at the anal verge, which should not be assumed to represent an anal papilla. (b) Digital photograph from a retroflexed rectal view at optical colonoscopy shows the same adenoma.
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Figure 36b. Adenomatous polyp near the anal verge. (a) Endoluminal 3D view from CT colonography shows a 12-mm sessile polyp near but not at the anal verge, which should not be assumed to represent an anal papilla. (b) Digital photograph from a retroflexed rectal view at optical colonoscopy shows the same adenoma.
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Figure 37a. Retained fecal material. (a) Endoluminal 3D view from CT colonography shows a smooth 15-mm flat lesion (arrowheads) that did not change position between supine and prone views. (b) Translucency rendering superimposed on the 3D endoluminal view demonstrates internal high attenuation (white area), an appearance consistent with barium-tagged stool. Translucency rendering provides a rapid means for assessing internal composition of polypoid lesions without the need for more time-consuming 2D correlation.
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Figure 37b. Retained fecal material. (a) Endoluminal 3D view from CT colonography shows a smooth 15-mm flat lesion (arrowheads) that did not change position between supine and prone views. (b) Translucency rendering superimposed on the 3D endoluminal view demonstrates internal high attenuation (white area), an appearance consistent with barium-tagged stool. Translucency rendering provides a rapid means for assessing internal composition of polypoid lesions without the need for more time-consuming 2D correlation.
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Figure 38a. Retained fecal material. (a) Endoluminal 3D view from CT colonography shows a large sessile polypoid lesion. (b) Axial 2D view shows that the lesion is internally tagged with barium (arrowhead), diagnostic of retained stool.
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Figure 38b. Retained fecal material. (a) Endoluminal 3D view from CT colonography shows a large sessile polypoid lesion. (b) Axial 2D view shows that the lesion is internally tagged with barium (arrowhead), diagnostic of retained stool.
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Figure 39a. Impacted diverticulum. (a) Endoluminal 3D view from CT colonography shows a relatively shallow polypoid lesion. (b) Axial 2D view shows that the lesion seen in a represents the "tip of the iceberg" of an impacted diverticulum (arrowhead). This 3D pitfall is easily avoided by use of translucency rendering or 2D correlation. (c) Digital photograph from optical colonoscopy shows multiple impacted diverticula.
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Figure 39b. Impacted diverticulum. (a) Endoluminal 3D view from CT colonography shows a relatively shallow polypoid lesion. (b) Axial 2D view shows that the lesion seen in a represents the "tip of the iceberg" of an impacted diverticulum (arrowhead). This 3D pitfall is easily avoided by use of translucency rendering or 2D correlation. (c) Digital photograph from optical colonoscopy shows multiple impacted diverticula.
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Figure 39c. Impacted diverticulum. (a) Endoluminal 3D view from CT colonography shows a relatively shallow polypoid lesion. (b) Axial 2D view shows that the lesion seen in a represents the "tip of the iceberg" of an impacted diverticulum (arrowhead). This 3D pitfall is easily avoided by use of translucency rendering or 2D correlation. (c) Digital photograph from optical colonoscopy shows multiple impacted diverticula.
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Figure 40. Side-by-side comparison of (inward) polyp and (outward) diverticulum. Endoluminal 3D view from CT colonography shows a 16-mm tubular adenoma (arrow) adjacent to a wide-mouth diverticulum (arrowhead). The volume rendering and lighting display used here allow for easy distinction.
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Figure 41a. Prominent colonic fold complex. (a) Axial 2D image from CT colonography shows diffuse sigmoid fold thickening consistent with diverticular disease. One area appears more prominent and somewhat polypoid (arrowhead). (b) Endoluminal 3D view shows that the focal prominence in a is due to a convergence of folds, which is a common finding. The linear, elongated nature of folds is readily apparent on this display. Note also the diverticula.
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Figure 41b. Prominent colonic fold complex. (a) Axial 2D image from CT colonography shows diffuse sigmoid fold thickening consistent with diverticular disease. One area appears more prominent and somewhat polypoid (arrowhead). (b) Endoluminal 3D view shows that the focal prominence in a is due to a convergence of folds, which is a common finding. The linear, elongated nature of folds is readily apparent on this display. Note also the diverticula.
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Figure 42a. CT colonographic appearances of the ileocecal valve. (a) Endoluminal 3D view shows the "papillary" form of the ileocecal valve. (b) Endoluminal 3D view shows the "labial" form of the ileocecal valve.
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Figure 42b. CT colonographic appearances of the ileocecal valve. (a) Endoluminal 3D view shows the "papillary" form of the ileocecal valve. (b) Endoluminal 3D view shows the "labial" form of the ileocecal valve.
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Figure 43a. Polypoid subtraction artifact related to a trapped air bubble. (a) Endoluminal 3D view from CT colonography shows a sessile polypoid lesion. (b) Translucency rendering demonstrates central air density (dark blue), which would not be confused with a soft-tissue polyp. (c) Coronal 2D view obtained before digital subtraction of residual fluid shows the air bubble (arrowhead) that led to the artifact on the subtracted 3D image.
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Figure 43b. Polypoid subtraction artifact related to a trapped air bubble. (a) Endoluminal 3D view from CT colonography shows a sessile polypoid lesion. (b) Translucency rendering demonstrates central air density (dark blue), which would not be confused with a soft-tissue polyp. (c) Coronal 2D view obtained before digital subtraction of residual fluid shows the air bubble (arrowhead) that led to the artifact on the subtracted 3D image.
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Figure 43c. Polypoid subtraction artifact related to a trapped air bubble. (a) Endoluminal 3D view from CT colonography shows a sessile polypoid lesion. (b) Translucency rendering demonstrates central air density (dark blue), which would not be confused with a soft-tissue polyp. (c) Coronal 2D view obtained before digital subtraction of residual fluid shows the air bubble (arrowhead) that led to the artifact on the subtracted 3D image.
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Figure 44. Endoluminal foreign bodies (medicine capsules). Endoluminal 3D view from CT colonography shows two well-circumscribed ovoid lesions that were symmetric in size and morphology. Images from 2D evaluation and 3D translucency rendering (not shown) demonstrated internal heterogeneity with areas of air attenuation internally. A third identical object was identified in the proximal colon. All three foreign bodies were readily mobile and assumed a dependent position on both supine and prone images. Immediately before CT colonography, the patient had undergone incomplete optical colonoscopy, which revealed several undigested shells of sustained-release capsules.
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Copyright © 2004 by the Radiological Society of North America.
