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CT and MR Imaging of Extrahepatic Fatty Masses of the Abdomen and Pelvis: Techniques, Diagnosis, Differential Diagnosis, and Pitfalls¹

¹ From the Department of Radiology, Porto Medical School, Hospital S. João, Porto, Portugal (J.M.P., P.S.P.); and the Department of Radiology, University of California Medical Center, 200 W Arbor Dr, San Diego, CA 92103-8756 (C.B.S., G.C.). Presented as an education exhibit at the 2003 RSNA Scientific Assembly. Received April 14, 2004; revision requested May 18 and received June 29; accepted June 30. All authors have no financial relationships to disclose. Address correspondence to C.B.S. (e-mail: csirlin@ucsd.edu).

View larger version (147K): [in a new window]   Figure 1.  Adrenal myelolipoma. Axial CT image shows a well-defined mass with homogeneous fat attenuation (–58 HU) in the right adrenal gland (arrow).

View larger version (157K): [in a new window]   Figure 2a.  Mature cystic teratoma of the ovary in a 27-year-old woman. (a) Axial in-phase gradient-echo MR image (repetition time msec/echo time msec = 120/4.4) shows a heterogeneous predominantly hyperintense mass in the right ovary (arrow). The hyperintense component is consistent with fat or hemorrhage. (b) Axial out-of-phase gradient-echo MR image (120/2.2) shows partial signal loss in the central nodule. More important, there is dramatic signal loss at the interface between the lesion and the water-based ovarian tissue stretched around it (arrowheads). This finding indicates that the lesion contains fat. (c) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss (arrow) relative to the signal intensity on the in-phase image (a), an appearance indicative of a predominantly macroscopic fatty component.

View larger version (163K): [in a new window]   Figure 2b.  Mature cystic teratoma of the ovary in a 27-year-old woman. (a) Axial in-phase gradient-echo MR image (repetition time msec/echo time msec = 120/4.4) shows a heterogeneous predominantly hyperintense mass in the right ovary (arrow). The hyperintense component is consistent with fat or hemorrhage. (b) Axial out-of-phase gradient-echo MR image (120/2.2) shows partial signal loss in the central nodule. More important, there is dramatic signal loss at the interface between the lesion and the water-based ovarian tissue stretched around it (arrowheads). This finding indicates that the lesion contains fat. (c) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss (arrow) relative to the signal intensity on the in-phase image (a), an appearance indicative of a predominantly macroscopic fatty component.

View larger version (142K): [in a new window]   Figure 2c.  Mature cystic teratoma of the ovary in a 27-year-old woman. (a) Axial in-phase gradient-echo MR image (repetition time msec/echo time msec = 120/4.4) shows a heterogeneous predominantly hyperintense mass in the right ovary (arrow). The hyperintense component is consistent with fat or hemorrhage. (b) Axial out-of-phase gradient-echo MR image (120/2.2) shows partial signal loss in the central nodule. More important, there is dramatic signal loss at the interface between the lesion and the water-based ovarian tissue stretched around it (arrowheads). This finding indicates that the lesion contains fat. (c) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss (arrow) relative to the signal intensity on the in-phase image (a), an appearance indicative of a predominantly macroscopic fatty component.

View larger version (179K): [in a new window]   Figure 3.  Adrenal myelolipoma. Axial CT image shows a well-defined mass with predominantly soft tissue attenuation in the left adrenal gland. Note the nodule of fat attenuation (arrow), which is characteristic of myelolipoma.

View larger version (165K): [in a new window]   Figure 4.  Adrenal myelolipoma. Axial CT image enhanced with intravenous contrast material shows a heterogeneous left adrenal mass (arrows) with fatty and enhancing soft tissue components. The presence of fat permits reliable diagnosis of a benign myelolipoma despite the soft tissue elements.

View larger version (136K): [in a new window]   Figure 5a.  Adrenal myelolipoma. (a) Axial in-phase MR image shows a heterogeneous predominantly hyperintense lesion (arrows), which is a nonspecific appearance. (b) Axial out-of-phase MR image shows dramatic signal loss at the interface between water- and lipid-based components (arrows), thus permitting noninvasive diagnosis of the lesion. (c) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows diminished signal intensity in the macroscopic fatty component (arrowhead), a finding that confirms the diagnosis.

View larger version (132K): [in a new window]   Figure 5b.  Adrenal myelolipoma. (a) Axial in-phase MR image shows a heterogeneous predominantly hyperintense lesion (arrows), which is a nonspecific appearance. (b) Axial out-of-phase MR image shows dramatic signal loss at the interface between water- and lipid-based components (arrows), thus permitting noninvasive diagnosis of the lesion. (c) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows diminished signal intensity in the macroscopic fatty component (arrowhead), a finding that confirms the diagnosis.

View larger version (134K): [in a new window]   Figure 5c.  Adrenal myelolipoma. (a) Axial in-phase MR image shows a heterogeneous predominantly hyperintense lesion (arrows), which is a nonspecific appearance. (b) Axial out-of-phase MR image shows dramatic signal loss at the interface between water- and lipid-based components (arrows), thus permitting noninvasive diagnosis of the lesion. (c) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows diminished signal intensity in the macroscopic fatty component (arrowhead), a finding that confirms the diagnosis.

View larger version (183K): [in a new window]   Figure 6a.  Adrenal adenoma. Axial unenhanced (a) and contrast material-enhanced (b) CT images show a low-attenuation mass in the left adrenal gland (arrow). The mass has an attenuation value of 3 HU on the unenhanced image (a) and 9 HU on the contrast-enhanced image (b). This result suggests the presence of microscopic fat, a finding compatible with adenoma.

View larger version (186K): [in a new window]   Figure 6b.  Adrenal adenoma. Axial unenhanced (a) and contrast material-enhanced (b) CT images show a low-attenuation mass in the left adrenal gland (arrow). The mass has an attenuation value of 3 HU on the unenhanced image (a) and 9 HU on the contrast-enhanced image (b). This result suggests the presence of microscopic fat, a finding compatible with adenoma.

View larger version (137K): [in a new window]   Figure 7a.  Adrenal adenoma. Axial in-phase (a) and out-of-phase (b) chemical shift MR images show an adrenal nodule (arrow). There is homogeneous signal loss on the out-of-phase image (b) relative to the signal intensity on the in-phase image (a), a finding that confirms the presence of water- and lipid-based components.

View larger version (155K): [in a new window]   Figure 7b.  Adrenal adenoma. Axial in-phase (a) and out-of-phase (b) chemical shift MR images show an adrenal nodule (arrow). There is homogeneous signal loss on the out-of-phase image (b) relative to the signal intensity on the in-phase image (a), a finding that confirms the presence of water- and lipid-based components.

View larger version (136K): [in a new window]   Figure 8a.  Renal angiomyolipoma. (a) Longitudinal US image shows a hyperechoic lesion in the inferior pole of the left kidney (cursors). The differential diagnosis includes renal cell carcinoma and angiomyolipoma. (b) Axial CT image shows fat attenuation within the lesion (arrow), a finding indicative of an angiomyolipoma.

View larger version (153K): [in a new window]   Figure 8b.  Renal angiomyolipoma. (a) Longitudinal US image shows a hyperechoic lesion in the inferior pole of the left kidney (cursors). The differential diagnosis includes renal cell carcinoma and angiomyolipoma. (b) Axial CT image shows fat attenuation within the lesion (arrow), a finding indicative of an angiomyolipoma.

View larger version (176K): [in a new window]   Figure 9a.  Renal angiomyolipoma with a predominant soft tissue component and a tiny fatty component. Axial unenhanced (a), corticomedullary phase (b), nephrographic phase (c), and excretory phase (d) CT images show a heterogeneous mass in the lateral left kidney. The mass is predominantly of soft tissue attenuation and superficially resembles a renal cell carcinoma; however, the presence of focal areas of fat attenuation (CT number, –20 HU or lower) (arrows) permits confident diagnosis of an angiomyolipoma.

View larger version (184K): [in a new window]   Figure 9b.  Renal angiomyolipoma with a predominant soft tissue component and a tiny fatty component. Axial unenhanced (a), corticomedullary phase (b), nephrographic phase (c), and excretory phase (d) CT images show a heterogeneous mass in the lateral left kidney. The mass is predominantly of soft tissue attenuation and superficially resembles a renal cell carcinoma; however, the presence of focal areas of fat attenuation (CT number, –20 HU or lower) (arrows) permits confident diagnosis of an angiomyolipoma.

View larger version (183K): [in a new window]   Figure 9c.  Renal angiomyolipoma with a predominant soft tissue component and a tiny fatty component. Axial unenhanced (a), corticomedullary phase (b), nephrographic phase (c), and excretory phase (d) CT images show a heterogeneous mass in the lateral left kidney. The mass is predominantly of soft tissue attenuation and superficially resembles a renal cell carcinoma; however, the presence of focal areas of fat attenuation (CT number, –20 HU or lower) (arrows) permits confident diagnosis of an angiomyolipoma.

View larger version (182K): [in a new window]   Figure 9d.  Renal angiomyolipoma with a predominant soft tissue component and a tiny fatty component. Axial unenhanced (a), corticomedullary phase (b), nephrographic phase (c), and excretory phase (d) CT images show a heterogeneous mass in the lateral left kidney. The mass is predominantly of soft tissue attenuation and superficially resembles a renal cell carcinoma; however, the presence of focal areas of fat attenuation (CT number, –20 HU or lower) (arrows) permits confident diagnosis of an angiomyolipoma.

View larger version (112K): [in a new window]   Figure 10a.  Angiomyolipoma. (a) Axial in-phase gradient-echo MR image (echo time = 4.4 msec) shows a hyperintense focus in the right kidney (arrow). The differential diagnosis includes a fatty lesion and a hemorrhagic cyst. (b) Axial out-of-phase gradient-echo MR image (echo time = 2.2 msec) shows signal loss at the interface of the fatty lesion and the water-based renal parenchyma (arrow). This finding indicates that the lesion is an angiomyolipoma and not a hemorrhagic cyst.

View larger version (125K): [in a new window]   Figure 10b.  Angiomyolipoma. (a) Axial in-phase gradient-echo MR image (echo time = 4.4 msec) shows a hyperintense focus in the right kidney (arrow). The differential diagnosis includes a fatty lesion and a hemorrhagic cyst. (b) Axial out-of-phase gradient-echo MR image (echo time = 2.2 msec) shows signal loss at the interface of the fatty lesion and the water-based renal parenchyma (arrow). This finding indicates that the lesion is an angiomyolipoma and not a hemorrhagic cyst.

View larger version (119K): [in a new window]   Figure 11a.  Massive right renal angiomyolipoma with hemorrhage in a patient with tuberous sclerosis several years after left nephrectomy. (a) Axial unenhanced CT image shows a huge heterogeneous mass of predominantly fat attenuation replacing the right kidney (arrows). The kidney itself is virtually unrecognizable. (b) Axial CT image obtained inferior to a shows a nodular area of high attenuation (arrow), which is suggestive of hemorrhage. Note the surrounding hemorrhage on both images (arrowhead in a, arrowheads in b).

View larger version (146K): [in a new window]   Figure 11b.  Massive right renal angiomyolipoma with hemorrhage in a patient with tuberous sclerosis several years after left nephrectomy. (a) Axial unenhanced CT image shows a huge heterogeneous mass of predominantly fat attenuation replacing the right kidney (arrows). The kidney itself is virtually unrecognizable. (b) Axial CT image obtained inferior to a shows a nodular area of high attenuation (arrow), which is suggestive of hemorrhage. Note the surrounding hemorrhage on both images (arrowhead in a, arrowheads in b).

View larger version (195K): [in a new window]   Figure 12a.  Mature cystic teratoma of the left ovary. (a) Sagittal transabdominal US image shows a large, heterogeneous, predominantly hyperechoic mass (arrows). (b) Axial contrast-enhanced CT image shows the retrouterine mass (arrows), which is predominantly of fat attenuation. (c, d) Axial in-phase (c) and out-of-phase (d) MR images show signal loss at the interface between water- and lipid-based components on the out-of-phase image (arrows in d) relative to the signal intensity on the in-phase image (c), thus confirming the presence of a fat component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal suppression (arrowheads).

View larger version (175K): [in a new window]   Figure 12b.  Mature cystic teratoma of the left ovary. (a) Sagittal transabdominal US image shows a large, heterogeneous, predominantly hyperechoic mass (arrows). (b) Axial contrast-enhanced CT image shows the retrouterine mass (arrows), which is predominantly of fat attenuation. (c, d) Axial in-phase (c) and out-of-phase (d) MR images show signal loss at the interface between water- and lipid-based components on the out-of-phase image (arrows in d) relative to the signal intensity on the in-phase image (c), thus confirming the presence of a fat component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal suppression (arrowheads).

View larger version (135K): [in a new window]   Figure 12c.  Mature cystic teratoma of the left ovary. (a) Sagittal transabdominal US image shows a large, heterogeneous, predominantly hyperechoic mass (arrows). (b) Axial contrast-enhanced CT image shows the retrouterine mass (arrows), which is predominantly of fat attenuation. (c, d) Axial in-phase (c) and out-of-phase (d) MR images show signal loss at the interface between water- and lipid-based components on the out-of-phase image (arrows in d) relative to the signal intensity on the in-phase image (c), thus confirming the presence of a fat component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal suppression (arrowheads).

View larger version (153K): [in a new window]   Figure 12d.  Mature cystic teratoma of the left ovary. (a) Sagittal transabdominal US image shows a large, heterogeneous, predominantly hyperechoic mass (arrows). (b) Axial contrast-enhanced CT image shows the retrouterine mass (arrows), which is predominantly of fat attenuation. (c, d) Axial in-phase (c) and out-of-phase (d) MR images show signal loss at the interface between water- and lipid-based components on the out-of-phase image (arrows in d) relative to the signal intensity on the in-phase image (c), thus confirming the presence of a fat component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal suppression (arrowheads).

View larger version (148K): [in a new window]   Figure 12e.  Mature cystic teratoma of the left ovary. (a) Sagittal transabdominal US image shows a large, heterogeneous, predominantly hyperechoic mass (arrows). (b) Axial contrast-enhanced CT image shows the retrouterine mass (arrows), which is predominantly of fat attenuation. (c, d) Axial in-phase (c) and out-of-phase (d) MR images show signal loss at the interface between water- and lipid-based components on the out-of-phase image (arrows in d) relative to the signal intensity on the in-phase image (c), thus confirming the presence of a fat component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal suppression (arrowheads).

View larger version (170K): [in a new window]   Figure 13.  Mesenteric liposarcoma. Axial contrast-enhanced CT image shows a well-defined, slightly heterogeneous mass with fatty components in the mesentery. The mass causes posterior displacement of some abdominal structures (arrowhead) and anterior displacement of the small intestine (arrows). The thin, fibrous internal septa of soft tissue attenuation suggest the diagnosis of liposarcoma. An identical mass arising from the adrenal gland or kidney would be considered benign.

View larger version (167K): [in a new window]   Figure 14a.  Retroperitoneal liposarcoma. (a) Transabdominal US image shows a large, well-defined, hyperechoic mass (cursors) in the abdominal cavity. The mass demonstrates the attenuation of sound, which is indicative of fat. (b) Axial contrast-enhanced CT image shows heterogeneous fat attenuation and coarse, thickened septa in the mass (arrows), findings suggestive of a well-differentiated liposarcoma. (c, d) Axial in-phase (c) and out-of-phase (d) gradient-echo MR images show signal loss in the interface between lipid and water on the out-of-phase image (arrowheads in d) relative to the signal intensity on the in-phase image (c), a finding that confirms the presence of a fatty component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss of the macroscopic fatty components (arrows), a finding that confirms the predominantly fatty content of the mass.

View larger version (184K): [in a new window]   Figure 14b.  Retroperitoneal liposarcoma. (a) Transabdominal US image shows a large, well-defined, hyperechoic mass (cursors) in the abdominal cavity. The mass demonstrates the attenuation of sound, which is indicative of fat. (b) Axial contrast-enhanced CT image shows heterogeneous fat attenuation and coarse, thickened septa in the mass (arrows), findings suggestive of a well-differentiated liposarcoma. (c, d) Axial in-phase (c) and out-of-phase (d) gradient-echo MR images show signal loss in the interface between lipid and water on the out-of-phase image (arrowheads in d) relative to the signal intensity on the in-phase image (c), a finding that confirms the presence of a fatty component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss of the macroscopic fatty components (arrows), a finding that confirms the predominantly fatty content of the mass.

View larger version (138K): [in a new window]   Figure 14c.  Retroperitoneal liposarcoma. (a) Transabdominal US image shows a large, well-defined, hyperechoic mass (cursors) in the abdominal cavity. The mass demonstrates the attenuation of sound, which is indicative of fat. (b) Axial contrast-enhanced CT image shows heterogeneous fat attenuation and coarse, thickened septa in the mass (arrows), findings suggestive of a well-differentiated liposarcoma. (c, d) Axial in-phase (c) and out-of-phase (d) gradient-echo MR images show signal loss in the interface between lipid and water on the out-of-phase image (arrowheads in d) relative to the signal intensity on the in-phase image (c), a finding that confirms the presence of a fatty component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss of the macroscopic fatty components (arrows), a finding that confirms the predominantly fatty content of the mass.

View larger version (162K): [in a new window]   Figure 14d.  Retroperitoneal liposarcoma. (a) Transabdominal US image shows a large, well-defined, hyperechoic mass (cursors) in the abdominal cavity. The mass demonstrates the attenuation of sound, which is indicative of fat. (b) Axial contrast-enhanced CT image shows heterogeneous fat attenuation and coarse, thickened septa in the mass (arrows), findings suggestive of a well-differentiated liposarcoma. (c, d) Axial in-phase (c) and out-of-phase (d) gradient-echo MR images show signal loss in the interface between lipid and water on the out-of-phase image (arrowheads in d) relative to the signal intensity on the in-phase image (c), a finding that confirms the presence of a fatty component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss of the macroscopic fatty components (arrows), a finding that confirms the predominantly fatty content of the mass.

View larger version (151K): [in a new window]   Figure 14e.  Retroperitoneal liposarcoma. (a) Transabdominal US image shows a large, well-defined, hyperechoic mass (cursors) in the abdominal cavity. The mass demonstrates the attenuation of sound, which is indicative of fat. (b) Axial contrast-enhanced CT image shows heterogeneous fat attenuation and coarse, thickened septa in the mass (arrows), findings suggestive of a well-differentiated liposarcoma. (c, d) Axial in-phase (c) and out-of-phase (d) gradient-echo MR images show signal loss in the interface between lipid and water on the out-of-phase image (arrowheads in d) relative to the signal intensity on the in-phase image (c), a finding that confirms the presence of a fatty component. (e) Axial gadolinium-enhanced fat saturation T1-weighted MR image shows marked signal loss of the macroscopic fatty components (arrows), a finding that confirms the predominantly fatty content of the mass.

View larger version (157K): [in a new window]   Figure 15.  Myxoid liposarcoma. Axial contrast-enhanced CT image shows a minimally heterogeneous mass with a mean CT number of 10 HU (arrows). Prospectively, the mass was erroneously diagnosed as a benign cyst on the basis of the fluid attenuation value. The correct diagnosis was made at surgery when the surgeon unexpectedly encountered an incompletely resectable solid mass. In retrospect, although the mean attenuation value within the lesion was 10 HU, the range of attenuation values on a pixel-by-pixel basis was –100 HU to 60 HU. Recognition of the broad range of attenuation values and the somewhat irregular septa within the mass may have permitted correct diagnosis with CT.

View larger version (180K): [in a new window]   Figure 16a.  Myxoid liposarcoma. Axial contrast-enhanced CT images show a lobulated inhomogeneous mass localized to the retroperitoneal space, with posterior displacement of the psoas muscle and anterior displacement of the retroperitoneal vessels. Portions of the mass have fluid attenuation owing to admixture of fatty and soft tissue components, similar to the lesion in Figure 15. Recognition of enhancing septa and mural components, which are more conspicuous on the delayed image (arrows in b), permitted the correct diagnosis.

View larger version (185K): [in a new window]   Figure 16b.  Myxoid liposarcoma. Axial contrast-enhanced CT images show a lobulated inhomogeneous mass localized to the retroperitoneal space, with posterior displacement of the psoas muscle and anterior displacement of the retroperitoneal vessels. Portions of the mass have fluid attenuation owing to admixture of fatty and soft tissue components, similar to the lesion in Figure 15. Recognition of enhancing septa and mural components, which are more conspicuous on the delayed image (arrows in b), permitted the correct diagnosis.

View larger version (170K): [in a new window]   Figure 17.  Lipoma of the pancreas. Axial contrast-enhanced CT image shows a large, homogeneous, fat attenuation mass within the pancreatic head (arrows), with lateral displacement of the common bile duct (arrowhead).

View larger version (154K): [in a new window]   Figure 18.  Lipoma of the terminal ileum. Axial contrast-enhanced CT image shows a small, homogeneous, fat attenuation mass within the wall of the terminal ileum (arrow), an appearance that allows diagnosis of a lipoma.

View larger version (175K): [in a new window]   Figure 19.  Epiploic appendagitis. Axial contrast-enhanced CT image shows an ovoid mass of fat attenuation (open arrow) anterior to the descending colon. The mass is surrounded by a hyperattenuating rim. A central high-attenuation dot was seen on images obtained superiorly (not shown). Note also the moderate fat stranding (arrowhead) and the mild focal thickening of the adjacent colonic wall (solid arrow).

View larger version (185K): [in a new window]   Figure 20.  Omental infarction. Axial contrast-enhanced CT image shows an inhomogeneous, round, high-attenuation fatty mass in the greater omentum (arrows). The mass is anterior to and exerts mass effect on the ascending colon. Mild adjacent wall thickening is also evident (arrowhead).

View larger version (193K): [in a new window]   Figure 21.  Mesenteric panniculitis. Axial contrast-enhanced CT image shows a well-defined, inhomogeneous fatty mass (arrowheads) with a hyperattenuating peripheral rim (open arrow). Note the fatty halos surrounding the mesenteric vessels and lymph nodes (solid arrows).

View larger version (144K): [in a new window]   Figure 22a.  Intussusception in a patient with an ileal lipoma. (a) Axial CT image shows a small amount of mesenteric fat between the walls of the intussusceptum and the intussuscipiens (arrows). (b) Axial CT image obtained superiorly to a shows a leading lipoma (arrowhead).

View larger version (151K): [in a new window]   Figure 22b.  Intussusception in a patient with an ileal lipoma. (a) Axial CT image shows a small amount of mesenteric fat between the walls of the intussusceptum and the intussuscipiens (arrows). (b) Axial CT image obtained superiorly to a shows a leading lipoma (arrowhead).

View larger version (137K): [in a new window]   Figure 23.  Diffuse submucosal fat in the terminal ileum in an elderly patient with long-standing Crohn disease. Axial contrast-enhanced CT image shows fat attenuation within the submucosal layer of the terminal ileum (arrow). Approximately 30 cm of the distal ileum was involved (other images not shown). There is no mass effect.

View larger version (162K): [in a new window]   Figure 24.  Fibrofatty mesenteric proliferation and submucosal fat deposition in an elderly patient with long-standing Crohn disease (same patient as in Fig 23). Axial contrast-enhanced CT image shows mild circumferential wall thickening with fat attenuation in the cecum and distal ileum (arrows) and fibrofatty mesenteric proliferation surrounding the affected bowel loops (arrowheads).

View larger version (142K): [in a new window]   Figure 25.  Fatty proliferation and submucosal fat deposition in a patient with ulcerative colitis. Axial CT image shows fatty proliferation with fine stranding around the rectum (arrowheads). Note also the submucosal fat deposition (arrow).

View larger version (125K): [in a new window]   Figure 26.  Fatty replacement of the pancreas in a patient with cystic fibrosis. Axial contrast-enhanced CT image shows virtually complete replacement of pancreatic tissue by tissue with fat attenuation (arrowheads). Note the main pancreatic duct (arrow).

View larger version (139K): [in a new window]   Figure 27.  Inguinal hernia. Axial contrast-enhanced CT image shows a well-defined fatty mass within the inferior aspect of the right inguinal canal (arrow). The mass represents herniation of intraabdominal fat into the inguinal canal.