DOI: 10.1148/rg.276075027
RadioGraphics 2007;27:1681-1692
© RSNA, 2007
Evaluation of Submucosal Lesions of the Large Intestine
Part 1. Neoplasms1
Perry J. Pickhardt, MD,
David H. Kim, MD,
Christine O. Menias, MD,
Deepak V. Gopal, MD,
Glen M. Arluk, MD, and
Charles P. Heise, MD
1 From the Department of Radiology (P.J.P., D.H.K.), Section of Gastroenterology and Hepatology (D.V.G.), and Department of Surgery (C.P.H.), University of Wisconsin Medical School, 600 Highland Ave, E3/311 Clinical Science Center, Madison, WI 53792-3252; Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Mo (C.O.M.); and the Department of Gastroenterology, Portsmouth Naval Hospital, Portsmouth, Va (G.M.A.). Recipient of a Certificate of Merit award for an education exhibit at the 2006 RSNA Annual Meeting. Received February 20, 2007; revision requested March 23 and received May 7; accepted May 10. P.J.P. is a consultant with Viatronix, Medicsight, and C.B. Fleet; D.H.K. is a speaker with Viatronix and Medicsight; all remaining authors have no financial relationships to disclose.
Address correspondence to P.J.P. (e-mail: pj.pickhardt{at}hosp.wisc.edu).
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Abstract
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At luminal evaluation of the large intestine, any masslike protrusion that is covered by normal mucosa, whether the underlying process is intramural or extramural in origin, may be reported as a submucosal lesion. The full characterization of submucosal lesions may be difficult with optical colonoscopy alone, and endoscopic biopsy is often nondiagnostic. Cross-sectional radiologic imaging studies allow evaluation of the entire thickness of the bowel wall and surrounding tissues and often provide additional information with regard to lesion origin, internal composition, and extent of disease. Likewise, it may be difficult to distinguish submucosal lesions from mucosal polyps on radiologic images, and optical colonoscopy may provide complementary information about superficial submucosal soft-tissue lesions that are detected at computed tomographic (CT) colonography or barium imaging. Depending on the specific clinical situation, colonoscopy, CT colonography, transrectal ultrasonography, and magnetic resonance imaging all may play an important role in the diagnostic evaluation of submucosal lesions of the large intestine. It is important that radiologists be familiar with the multimodality imaging appearances of such entities so that neoplasms—especially those that are malignant—can be accurately identified and characterized and effectively managed.
© RSNA, 2007
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Introduction
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At endoluminal colorectal examinations (eg, optical colonoscopy), the term submucosal lesion may be applied to describe any masslike protrusion into the lumen that is covered by normal overlying mucosa. Submucosal lesions, which classically appear as smooth broad-based abnormalities at luminal examination, may arise from the various layers of the intestinal wall (intramural origin) or from an extrinsic process (extramural origin). Some entities, such as extracolonic malignancies, may begin as an extramural process but secondarily invade the large intestine and become intramural as well. Although optical colonoscopy may help accurately differentiate mucosal lesions from lesions of submucosal origin, the ability to fully characterize a submucosal abnormality on the sole basis of a luminal examination is somewhat limited. Furthermore, the diagnostic yield of endoscopic biopsy for such lesions is relatively low. However, cross-sectional imaging modalities may help effectively evaluate the full thickness of the large intestinal wall and surrounding tissues and thus may be useful in the work-up of suspected submucosal abnormalities detected at optical colonoscopy. In particular, computed tomographic (CT) colonography, transrectal ultrasonography (US), and magnetic resonance (MR) imaging all are capable of providing valuable information in this clinical setting.
This article, the first in a two-part review of the radiologic and endoscopic imaging appearances of submucosal lesions, describes neoplasms with intramural and extramural origins (Table). The second article describes submucosal lesions with nonneoplastic causes. Particular emphasis is placed on the complementary capabilities of optical colonoscopy and CT colonography for the evaluation of submucosal lesions. Although screening for mucosal polyps and masses is the primary indication for CT colonography (1,2), the technique is useful also for the further evaluation of submucosal abnormalities detected at optical colonoscopy (3). We generally use a standard unenhanced CT colonography protocol to evaluate submucosal abnormalities detected at optical colonoscopy, but the use of intravenous contrast material may be valuable in certain instances. On the other hand, some superficial submucosal lesions detected at CT colonography that project into the lumen cannot be differentiated from mucosal lesions and require further evaluation with optical colonoscopy. Beyond optical colonoscopy and CT colonography, transrectal US may be very helpful for evaluating some rectosigmoid lesions, and MR imaging may allow a more comprehensive assessment of broad-based extrinsic or exoenteric processes.
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Neoplasms with Intramural Origin
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A wide variety of benign and malignant primary submucosal neoplasms may arise from the wall of the large intestine. Most such tumors (lipomas, carcinoid tumors, lymphomas, and hemangiomas) originate in a location superficial to the muscularis propria and remain in that location; however, certain mesenchymal lesions, such as gastrointestinal stromal tumor (GIST), arise from a deeper part of the muscularis and often demonstrate an exoenteric growth pattern. Extracolonic malignancies may spread to the colon by various routes, but only those that spread hematogenously begin as an intramural process.
Lipoma
The colon is the most common gastrointestinal site of lipomas, which tend to be right-sided (4). At optical colonoscopy, lipomas typically have a pale yellow appearance and are soft on probing, a feature that is termed the "pillow" sign. Most lipomas appear as smooth broad-based lesions at radiologic imaging (Fig 1). Despite their submucosal origin, they occasionally evolve into pedunculated lesions (Fig 2) that may serve as a lead point for intussusception (Fig 3). Some lipomas cannot be confidently diagnosed at optical colonoscopy, and patients with such indeterminate lesions may be referred for a more definitive evaluation with CT colonography (Fig 1). Although the endoluminal 3D appearance of lipomas at CT colonography remains nonspecific, the presence of fat attenuation at 2D CT evaluation with soft-tissue windowing is diagnostic. A lipomatous appearance of the ileocecal valve is extremely common, and the valve should not be confused with a colonic lipoma. At barium enema studies, the pliability and lucency of lipomas often may be suggestive of the diagnosis, but such findings are not generally definitive. Unless the patient is symptomatic, treatment is not generally indicated.
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Figure 1a. Colonic lipoma. (a) Optical image from colonoscopy shows a broad-based submucosal mass. The patient underwent same-day evaluation with CT colonography. (b) Endoluminal three-dimensional (3D) CT colonographic image shows the submucosal mass and adjacent diverticula. (c) Coronal two-dimensional (2D) CT colonographic image shows homogeneous fat attenuation in the mass (arrow), a finding that allowed a definitive diagnosis.
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Figure 1b. Colonic lipoma. (a) Optical image from colonoscopy shows a broad-based submucosal mass. The patient underwent same-day evaluation with CT colonography. (b) Endoluminal three-dimensional (3D) CT colonographic image shows the submucosal mass and adjacent diverticula. (c) Coronal two-dimensional (2D) CT colonographic image shows homogeneous fat attenuation in the mass (arrow), a finding that allowed a definitive diagnosis.
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Figure 1c. Colonic lipoma. (a) Optical image from colonoscopy shows a broad-based submucosal mass. The patient underwent same-day evaluation with CT colonography. (b) Endoluminal three-dimensional (3D) CT colonographic image shows the submucosal mass and adjacent diverticula. (c) Coronal two-dimensional (2D) CT colonographic image shows homogeneous fat attenuation in the mass (arrow), a finding that allowed a definitive diagnosis.
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Figure 2. Colonic lipoma. Endoluminal 3D image from CT colonography shows a smooth, ovoid, pedunculated lesion. The 2D CT colonographic images (not shown) showed that the lesion had the attenuation of fat.
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Figure 3. Colonic lipoma. Curved transverse reformatted image from contrast-enhanced CT in a symptomatic patient shows a high-grade bowel obstruction from intussusception caused by a colonic lipoma (arrow), which acted as the lead point.
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Carcinoid Tumor
Carcinoid tumors of the large intestine are relatively uncommon and are most frequently observed in the rectum. They typically are small benign incidental lesions, and they often have a yellowish hue at optical colonoscopy (5). At CT colonography and colon imaging with other radiologic modalities, small carcinoid tumors may be difficult to differentiate from mucosal lesions (Fig 4). Patients with lesions of significant size that are detected at CT colonography generally are referred for further evaluation with optical colonoscopy. Large carcinoid tumors may ulcerate and cause bleeding in the lower gastrointestinal tract (Fig 5). Proximal colonic carcinoid tumors tend to be bulkier and more aggressive in behavior; most such lesions are located in the cecum or the proximal ascending colon (Fig 6). Appendiceal carcinoid tumors are described in the subsection "Appendiceal Tumors."
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Figure 4a. Rectal carcinoid tumor. (a, b) Endoluminal 3D image (a) and coronal 2D image (b) from CT colonography show a 9-mm polypoid lesion with soft-tissue attenuation (arrowhead in b) in the rectum. Note the adjacent rectal catheter on both images. (c) Optical image from same-day colonoscopy shows the superficial submucosal lesion, which was resected during colonoscopy.
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Figure 4b. Rectal carcinoid tumor. (a, b) Endoluminal 3D image (a) and coronal 2D image (b) from CT colonography show a 9-mm polypoid lesion with soft-tissue attenuation (arrowhead in b) in the rectum. Note the adjacent rectal catheter on both images. (c) Optical image from same-day colonoscopy shows the superficial submucosal lesion, which was resected during colonoscopy.
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Figure 4c. Rectal carcinoid tumor. (a, b) Endoluminal 3D image (a) and coronal 2D image (b) from CT colonography show a 9-mm polypoid lesion with soft-tissue attenuation (arrowhead in b) in the rectum. Note the adjacent rectal catheter on both images. (c) Optical image from same-day colonoscopy shows the superficial submucosal lesion, which was resected during colonoscopy.
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Figure 5a. Ulcerated rectal carcinoid tumor. (a) Optical colonoscopic image shows an ulcerated rectal mass. (b) Transrectal US image shows a hypoechoic lesion that has arisen from the submucosal layer of the rectal wall.
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Figure 5b. Ulcerated rectal carcinoid tumor. (a) Optical colonoscopic image shows an ulcerated rectal mass. (b) Transrectal US image shows a hypoechoic lesion that has arisen from the submucosal layer of the rectal wall.
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Figure 6a. Malignant cecal carcinoid tumor. (a) Transverse 2D CT colonographic image shows an irregular submucosal soft-tissue mass (*) that extends from the cecum. (b) Image from same-day optical colonoscopy shows a broad-based mass effect on the cecum, which had a rigid appearance. The diagnosis was confirmed at surgery. Two of seven regional lymph nodes tested positive for infiltration by tumor cells.
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Figure 6b. Malignant cecal carcinoid tumor. (a) Transverse 2D CT colonographic image shows an irregular submucosal soft-tissue mass (*) that extends from the cecum. (b) Image from same-day optical colonoscopy shows a broad-based mass effect on the cecum, which had a rigid appearance. The diagnosis was confirmed at surgery. Two of seven regional lymph nodes tested positive for infiltration by tumor cells.
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Lymphoma
Primary lymphoma of the large intestine is relatively rare, compared with that of the stomach and the small intestine. Nearly all occurrences of primary lymphoma of the large intestine are non-Hodgkin B-cell lymphoma (6). The ileocecal region is the most often involved, followed by the rectosigmoid region (Figs 7, 8). Immunocompromised patients (eg, patients with acquired immunodeficiency syndrome [AIDS], organ transplant recipients) are at an increased risk for lymphoproliferative disorders (Fig 9). The clinical manifestations often are nonspecific but may include gastrointestinal bleeding. Obstruction is rare. Imaging manifestations of colonic lymphoma include solitary or multifocal polypoid or bulky masses, annular lesions, ulcerating masses, and nodular wall thickening in a long segment (Figs 7–9). Polypoid lesions may be predisposed to intussusception. Associated abdominal lymphadenopathy may be seen but often is absent. Treatment usually consists of surgical resection followed by adjuvant chemotherapy. For some cases of posttransplantation lymphoproliferative disorder, the reduction or cessation of immunosuppressive therapy alone may be curative.
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Figure 7a. Lymphoma. (7a, 7b) Endoluminal 3D image (7a) and coronal 2D image (7b) show marked irregular fold thickening centered at the ileocecal valve (arrowheads), with extension into the terminal ileum. (7c) Optical colonoscopic image shows irregular thickening of the cecal folds, a finding that helped confirm the diagnosis. The lesion responded well to chemotherapy.
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Figure 7b. Lymphoma. (7a, 7b) Endoluminal 3D image (7a) and coronal 2D image (7b) show marked irregular fold thickening centered at the ileocecal valve (arrowheads), with extension into the terminal ileum. (7c) Optical colonoscopic image shows irregular thickening of the cecal folds, a finding that helped confirm the diagnosis. The lesion responded well to chemotherapy.
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Figure 7c. Lymphoma. (7a, 7b) Endoluminal 3D image (7a) and coronal 2D image (7b) show marked irregular fold thickening centered at the ileocecal valve (arrowheads), with extension into the terminal ileum. (7c) Optical colonoscopic image shows irregular thickening of the cecal folds, a finding that helped confirm the diagnosis. The lesion responded well to chemotherapy.
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Figure 9a. Colonic posttransplantation lymphoproliferative disorder. (a) Fused image from positron emission tomography and CT in a heart transplant recipient shows intense hypermetabolic activity in the sigmoid colon. (b) Image from subsequent optical colonoscopy shows a submucosal mass. The results of biopsy were suggestive of a lymphoproliferative process. The diagnosis was confirmed at laparoscopic sigmoid resection.
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Figure 9b. Colonic posttransplantation lymphoproliferative disorder. (a) Fused image from positron emission tomography and CT in a heart transplant recipient shows intense hypermetabolic activity in the sigmoid colon. (b) Image from subsequent optical colonoscopy shows a submucosal mass. The results of biopsy were suggestive of a lymphoproliferative process. The diagnosis was confirmed at laparoscopic sigmoid resection.
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Hemangioma
Colorectal cavernous hemangiomas are rare benign vascular neoplasms that most often involve the rectosigmoid region (Figs 10, 11). A hemangioma may be seen as a solitary and isolated finding or may be associated with an underlying condition such as Klippel-Trénaunay-Weber syndrome, in which case more extensive disease (hemangiomatosis) may be present (Fig 11). Rectal bleeding is the most common clinical manifestation of a colorectal cavernous hemangioma (7). At optical colonoscopy, the lesions may appear as nonspecific submucosal masses, or they may have the reddish-purple color of a plum, an appearance caused by vascular congestion (Fig 11). The presence of phleboliths at radiologic imaging is highly suggestive or even indicative of the diagnosis (Figs 10, 11).
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Figure 10. Rectosigmoid hemangiomatosis. Barium image shows a lengthy rectosigmoid segment with irregular luminal narrowing due to an extensive submucosal process. The presence of phleboliths surrounding the rectal lumen is highly suggestive of the diagnosis.
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Figure 11a. Rectal hemangiomatosis in Klippel-Trénaunay-Weber syndrome. (a) Contrast-enhanced CT image shows circumferential rectal wall thickening in association with multiple phleboliths, findings that are also visible on the transrectal US image in c. (b) Optical colonoscopic image shows lesions with a purplish hue that stand out from the normal appearance of the more proximal rectosigmoid segment. An MR angiogram (not shown) depicted asymmetric involvement of the lower extremities with vascular malformations, features typical of this syndrome.
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Figure 11b. Rectal hemangiomatosis in Klippel-Trénaunay-Weber syndrome. (a) Contrast-enhanced CT image shows circumferential rectal wall thickening in association with multiple phleboliths, findings that are also visible on the transrectal US image in c. (b) Optical colonoscopic image shows lesions with a purplish hue that stand out from the normal appearance of the more proximal rectosigmoid segment. An MR angiogram (not shown) depicted asymmetric involvement of the lower extremities with vascular malformations, features typical of this syndrome.
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Figure 11c. Rectal hemangiomatosis in Klippel-Trénaunay-Weber syndrome. (a) Contrast-enhanced CT image shows circumferential rectal wall thickening in association with multiple phleboliths, findings that are also visible on the transrectal US image in c. (b) Optical colonoscopic image shows lesions with a purplish hue that stand out from the normal appearance of the more proximal rectosigmoid segment. An MR angiogram (not shown) depicted asymmetric involvement of the lower extremities with vascular malformations, features typical of this syndrome.
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GIST and Other Primary Tumors
The GIST is the most common solid mesenchymal neoplasm of the gastrointestinal tract and is distinct from smooth muscle and neural tumors. This unique tumor expresses KIT (CD117) and is believed to derive from interstitial Cajal cells (gut pacemaker cells). GISTs typically arise in the muscularis propria layer and most commonly involve the stomach, followed (in order of decreasing frequency) by the small intestine, anorectum, colon, and esophagus. Like GISTs that occur in the stomach and small intestine, colorectal GISTs tend to exhibit exoenteric growth and only rarely demonstrate a prominent intraluminal component (8). Therefore, despite the relatively large size of these tumors, they have a broad-based appearance that is subtle and nonspecific at luminal examinations with optical colonoscopy and barium imaging, and it may be difficult to distinguish them from extrinsic structures (Fig 12). However, the bulky tumors are generally obvious at cross-sectional imaging with modalities such as CT, MR imaging, and transrectal US (Fig 12). Prominent enhancement of the tumor is typical at contrast material–enhanced CT or MR imaging. Metastatic spread to the liver and peritoneal cavity is relatively common with malignant GISTs.
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Figure 12a. Rectal GIST. (a) Optical colonoscopic image from a patient who presented with rectal bleeding shows a broad-based submucosal lesion within the rectum (arrowheads). (b) Transrectal US image shows a solid rounded rectal mass that appears to originate from the muscularis layer. (c, d) Preoperative images from CT (c) and MR imaging (d) show the predominantly exoenteric growth pattern of the GIST.
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Figure 12b. Rectal GIST. (a) Optical colonoscopic image from a patient who presented with rectal bleeding shows a broad-based submucosal lesion within the rectum (arrowheads). (b) Transrectal US image shows a solid rounded rectal mass that appears to originate from the muscularis layer. (c, d) Preoperative images from CT (c) and MR imaging (d) show the predominantly exoenteric growth pattern of the GIST.
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Figure 12c. Rectal GIST. (a) Optical colonoscopic image from a patient who presented with rectal bleeding shows a broad-based submucosal lesion within the rectum (arrowheads). (b) Transrectal US image shows a solid rounded rectal mass that appears to originate from the muscularis layer. (c, d) Preoperative images from CT (c) and MR imaging (d) show the predominantly exoenteric growth pattern of the GIST.
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Figure 12d. Rectal GIST. (a) Optical colonoscopic image from a patient who presented with rectal bleeding shows a broad-based submucosal lesion within the rectum (arrowheads). (b) Transrectal US image shows a solid rounded rectal mass that appears to originate from the muscularis layer. (c, d) Preoperative images from CT (c) and MR imaging (d) show the predominantly exoenteric growth pattern of the GIST.
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Various other submucosal primary colorectal neoplasms may be seen rarely at imaging. Soft-tissue mesenchymal tumors other than GISTs include such benign lesions as leiomyoma and schwannoma, which may manifest as nonspecific polypoid lesions at imaging (Fig 13). Cross-sectional imaging may demonstrate an exoenteric component in some cases (Fig 13).
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Figure 13a. Colonic leiomyoma. (a) Endoluminal 3D image from CT colonography shows a 1.3-cm polypoid lesion in the transverse colon. (b) Coronal 2D CT colonographic image helps confirm the soft-tissue nature of the lesion and depicts a small lobule of exoenteric extension (arrowhead), a highly atypical feature of a mucosal lesion. (c) Image from subsequent optical colonoscopy shows the intraluminal component, which was resected and proved to be a leiomyoma. The extraluminal component was still present at follow-up CT colonography 2 years later.
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Figure 13b. Colonic leiomyoma. (a) Endoluminal 3D image from CT colonography shows a 1.3-cm polypoid lesion in the transverse colon. (b) Coronal 2D CT colonographic image helps confirm the soft-tissue nature of the lesion and depicts a small lobule of exoenteric extension (arrowhead), a highly atypical feature of a mucosal lesion. (c) Image from subsequent optical colonoscopy shows the intraluminal component, which was resected and proved to be a leiomyoma. The extraluminal component was still present at follow-up CT colonography 2 years later.
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Figure 13c. Colonic leiomyoma. (a) Endoluminal 3D image from CT colonography shows a 1.3-cm polypoid lesion in the transverse colon. (b) Coronal 2D CT colonographic image helps confirm the soft-tissue nature of the lesion and depicts a small lobule of exoenteric extension (arrowhead), a highly atypical feature of a mucosal lesion. (c) Image from subsequent optical colonoscopy shows the intraluminal component, which was resected and proved to be a leiomyoma. The extraluminal component was still present at follow-up CT colonography 2 years later.
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Frankly malignant mesenchymal tumors that arise in the colon, such as leiomyosarcoma, are extremely rare and often are large and ulcerative by the time they are detected (Fig 14). Two other rare types of submucosal tumors are ganglioneuromas and granular cell tumors, both of which are generally benign and tend to manifest as nonspecific polypoid lesions arising in the superficial submucosal space (Fig 15).
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Figure 15a. Rectal ganglioneuroma. (a, b) Endoluminal 3D image (a) and coronal 2D reformatted image (b) from CT colonography show a rectal polyp with soft-tissue attenuation (arrowhead in b). (c) Optical image from subsequent colonoscopy shows the same polyp. A determination of submucosal origin was not possible on the basis of imaging findings alone. Endoscopic resection was performed, and the lesion was diagnosed at histologic evaluation.
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Figure 15b. Rectal ganglioneuroma. (a, b) Endoluminal 3D image (a) and coronal 2D reformatted image (b) from CT colonography show a rectal polyp with soft-tissue attenuation (arrowhead in b). (c) Optical image from subsequent colonoscopy shows the same polyp. A determination of submucosal origin was not possible on the basis of imaging findings alone. Endoscopic resection was performed, and the lesion was diagnosed at histologic evaluation.
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Figure 15c. Rectal ganglioneuroma. (a, b) Endoluminal 3D image (a) and coronal 2D reformatted image (b) from CT colonography show a rectal polyp with soft-tissue attenuation (arrowhead in b). (c) Optical image from subsequent colonoscopy shows the same polyp. A determination of submucosal origin was not possible on the basis of imaging findings alone. Endoscopic resection was performed, and the lesion was diagnosed at histologic evaluation.
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Hematogenous Metastases
Unlike the lesions that occur in secondary colonic involvement by peritoneal carcinomatosis and in direct colonic invasion, hematogenous metastases begin as an abnormal intramural process superficial to the muscularis propria. Melanoma is the most common of the primary tumors that may spread hematogenously to the intestine, followed by lung cancer and breast cancer (9). Hematogenous metastases to the intestine typically appear as well-defined submucosal nodules or masses with or without a central area of ulceration (Figs 16, 17). The colon and rectum are affected much less frequently than the small intestine.
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Neoplasms with Extramural Origin
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Secondary involvement by an extracolonic tumor may be difficult to distinguish from a normal extrinsic impression or a primary intramural lesion at luminal examinations with optical colonoscopy. For extramural processes, in particular, cross-sectional imaging may be indispensable for evaluating the extent of disease. For that reason, direct invasion by extracolonic malignancy, colonic involvement by peritoneal carcinomatosis, and appendiceal neoplasms are considered here as separate categories.
Direct Invasion by Extracolonic Malignancy
Involvement of the colon or rectum by an extracolonic tumor may occur contiguously, along connecting ligaments that act as paths of least resistance, or may take place by direct spread from adjacent disease in close proximity. The clinical history often provides clues to the diagnosis. The prototypical example of ligamentous spread is extension of gastric adenocarcinoma to the transverse colon via the gastrocolic ligament (Figs 18, 19). Adenocarcinoma of the transverse colon may spread by a similar route to the greater curvature of the stomach. At optical colonoscopy, extensive mural invasion from an extracolonic malignancy may manifest as luminal narrowing, irregular fold thickening, or ulceration (Figs 19, 20). Cross-sectional imaging, particularly CT, is effective for evaluating the entire extent of disease (Figs 19, 20).
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Figure 18. Fluoroscopic image from a barium enema study shows segmental narrowing of a proximal segment of the transverse colon, a finding suggestive of a contiguous extension of gastric adenocarcinoma along the gastrocolic ligament. The finding was confirmed at CT and endoscopy (not shown).
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Figure 19a. Contiguous extension of gastric adenocarcinoma. (a) Optical colonoscopic image shows fixed luminal narrowing and irregular fold thickening of the transverse colon. (b) Transverse contrast-enhanced CT image shows abnormal thickening and enhancement of the wall of the transverse colon (arrowheads), a finding that was traceable upward along the gastrocolic ligament to the greater curvature of the stomach.
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Figure 19b. Contiguous extension of gastric adenocarcinoma. (a) Optical colonoscopic image shows fixed luminal narrowing and irregular fold thickening of the transverse colon. (b) Transverse contrast-enhanced CT image shows abnormal thickening and enhancement of the wall of the transverse colon (arrowheads), a finding that was traceable upward along the gastrocolic ligament to the greater curvature of the stomach.
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Figure 20a. Rectal invasion by prostate cancer. (a) Optical colonoscopic image obtained in a patient with rectal bleeding and a history of previously treated prostate cancer shows a large ulcerated rectal mass. Transrectal US depicted perirectal lymphadenopathy. Based on these findings, the initial diagnosis was primary rectal adenocarcinoma. (b) Transverse contrast-enhanced CT image shows the predominantly perirectal location of the mass, a location atypical for primary rectal adenocarcinoma. Pathologic analysis after resection showed the mass to be a metastasis from prostate adenocarcinoma.
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Figure 20b. Rectal invasion by prostate cancer. (a) Optical colonoscopic image obtained in a patient with rectal bleeding and a history of previously treated prostate cancer shows a large ulcerated rectal mass. Transrectal US depicted perirectal lymphadenopathy. Based on these findings, the initial diagnosis was primary rectal adenocarcinoma. (b) Transverse contrast-enhanced CT image shows the predominantly perirectal location of the mass, a location atypical for primary rectal adenocarcinoma. Pathologic analysis after resection showed the mass to be a metastasis from prostate adenocarcinoma.
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Peritoneal Carcinomatosis
Once malignant cells gain access to the peritoneal cavity, their relatively unrestricted spread throughout this large potential space gives rise to peritoneal carcinomatosis. Nearly any malignancy has the potential to metastasize to the subperitoneal or peritoneal space, but gastrointestinal and ovarian primary carcinomas are seen most frequently (10). Serosal implants can involve and invade any portion of the large bowel that contacts the peritoneal space (Figs 21, 22). Because of the anatomic situation and peritoneal flow dynamics, the rectosigmoid and transverse colon are most frequently involved. The submucosal abnormalities seen at endoluminal evaluation may be due to soft-tissue implants, loculated malignant ascites, or both.
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Figure 21. Colonic involvement in peritoneal carcinomatosis. Transverse contrast-enhanced CT image shows a round lesion (arrow) with attenuation similar to that of muscle. The lesion, which simulates a small rectosigmoid GIST, subsequently was proved to be a metastatic serosal implant from ovarian cancer. A bowel-containing abdominal wall hernia also is visible on the right side.
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Figure 22. Colonic involvement in peritoneal carcinomatosis. Transverse contrast-enhanced CT image shows extensive peritoneal carcinomatosis from adenoid cystic carcinoma of the parotid gland, with innumerable peritoneal soft-tissue masses that predominantly involve the omentum. Note the mass effect on both the small and the large bowel.
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Appendiceal Tumors
Appendiceal neoplasms represent a unique subset of submucosal tumors. Because of the constant anatomic relationship between the appendix and cecum, the tumor location is an important diagnostic clue. A mucocele from a mucinous cystic neoplasm is the most common appendiceal tumor that produces a submucosal abnormality seen at imaging (Figs 23, 24) (11). Rarely, a mucocele may lead to a symptomatic presentation because of intussusception or superinfection. At luminal evaluation, only the mass effect from the lesion can be seen; cross-sectional imaging is critical for determining the presence of an appendiceal neoplasm and providing a comprehensive preoperative evaluation (Fig 23). Carcinoid tumors of the appendix are more common than mucinous cystic neoplasms; however, because they are typically small and most often involve the distal appendix, they only rarely produce a visible submucosal colonic abnormality.
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Figure 23a. Mucocele from an appendiceal mucinous adenoma. (a) Endoluminal 3D image from CT colonography shows a polypoid mass (arrow) covering the appendiceal orifice, adjacent to the ileocecal valve (arrowhead). (b) Curved reformatted 2D CT colonographic image shows a bulbous, dilated base of the appendix, which is filled with a material that has intermediate to low attenuation (arrowheads). (c) Optical colonoscopic image shows an apparent prominent stump at the appendiceal orifice, but the patient had no history of appendectomy. The diagnosis was confirmed at surgery.
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Figure 23b. Mucocele from an appendiceal mucinous adenoma. (a) Endoluminal 3D image from CT colonography shows a polypoid mass (arrow) covering the appendiceal orifice, adjacent to the ileocecal valve (arrowhead). (b) Curved reformatted 2D CT colonographic image shows a bulbous, dilated base of the appendix, which is filled with a material that has intermediate to low attenuation (arrowheads). (c) Optical colonoscopic image shows an apparent prominent stump at the appendiceal orifice, but the patient had no history of appendectomy. The diagnosis was confirmed at surgery.
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Figure 23c. Mucocele from an appendiceal mucinous adenoma. (a) Endoluminal 3D image from CT colonography shows a polypoid mass (arrow) covering the appendiceal orifice, adjacent to the ileocecal valve (arrowhead). (b) Curved reformatted 2D CT colonographic image shows a bulbous, dilated base of the appendix, which is filled with a material that has intermediate to low attenuation (arrowheads). (c) Optical colonoscopic image shows an apparent prominent stump at the appendiceal orifice, but the patient had no history of appendectomy. The diagnosis was confirmed at surgery.
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Figure 24. Invagination or early intussusception caused by an appendiceal mucocele. Fluoroscopic image from a barium enema study shows a round filling defect that projects from the appendix into the cecum. The mucocele arose from a mucinous adenoma.
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Conclusions
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Various neoplasms of intramural or extramural origin may give rise to a submucosal abnormality at colorectal evaluation. The combined use of endoluminal optical colonoscopy and a cross-sectional imaging technique allows a comprehensive evaluation of most submucosal lesions. The combination of optical colonoscopy and CT colonography has proved especially effective in our experience, and both examinations generally can be performed on the same day, without the need for additional bowel preparation. In some cases, transrectal US and MR imaging may provide additional useful information. For the optimal evaluation and appropriate management of submucosal abnormalities, a close collaboration among colleagues in radiology, gastroenterology, and colorectal surgery is paramount.
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Footnotes
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Abbreviations: GIST = gastrointestinal stromal tumor, 3D = three-dimensional, 2D = two-dimensional
See also the article by Pickhardt et al on pp 1693–1703.
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References
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- Pickhardt PJ, Choi JR, Hwang I, et al. CT virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med 2003;349:2191–2200.[Abstract/Free Full Text]
- Pickhardt PJ, Taylor AJ, Kim DH, Reichelderfer M, Gopal DV, Pfau PR. Screening for colorectal neoplasia with CT colonography: initial experience from the first year of coverage by third-party payers. Radiology 2006;241:417–425.[Abstract/Free Full Text]
- Pickhardt PJ. Differential diagnosis of polypoid lesions seen at CT colonography (virtual colonoscopy). RadioGraphics 2004;24:1535–1559.[Abstract/Free Full Text]
- Hancock BJ, Vajcner A. Lipomas of the colon: a clinicopathologic review. Can J Surg 1988;31:178–181.[Medline]
- Levy AD, Sobin LH. Gastrointestinal carcinoids: imaging features with clinicopathologic comparison. RadioGraphics 2007;27:237–257.[Abstract/Free Full Text]
- Wong MT, Eu KW. Primary colorectal lymphomas. Colorectal Dis 2006;8:586–591.[CrossRef][Medline]
- Dachman AH, Ros PR, Shekitka KM, Buck JL, Olmsted WW, Hinton CB. Colorectal hemangioma: radiologic findings. Radiology 1988;167:31–34.[Abstract/Free Full Text]
- Levy AD, Remotti HE, Thompson WM, Sobin LH, Miettinen M. Anorectal gastrointestinal stromal tumors: CT and MR imaging features with clinical and pathologic correlation. AJR Am J Roentgenol 2003;180:1607–1612.[Abstract/Free Full Text]
- Abrams HL, Spiro R, Goldstein N. Metastases in carcinoma: analysis of 1000 autopsied cases. Cancer 1950;3:74–75.[CrossRef][Medline]
- Levitt RG, Koehler RE, Sagel SS, et al. Metastatic disease of the mesentery and omentum. Radiol Clin North Am 1982;20:501–510.[Medline]
- Pickhardt PJ, Levy AD, Rohrmann CA, Kende AI. Primary neoplasms of the appendix: radiologic spectrum of disease with pathologic correlation. RadioGraphics 2003;23:645–662.[Abstract/Free Full Text]
Related Article
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Evaluation of Submucosal Lesions of the Large Intestine: Part 2. Nonneoplastic Causes
- Perry J. Pickhardt, David H. Kim, Christine O. Menias, Deepak V. Gopal, Glen M. Arluk, and Charles P. Heise
RadioGraphics 2007 27: 1693-1703.
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Abstract
Introduction
