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Disproportionate Fat Stranding: A Helpful CT Sign in Patients with Acute Abdominal Pain¹

¹ From the Departments of Radiology of University of California San Diego Medical Center, 200 W Arbor Dr, San Diego, CA 92103-8756 (J.M.P., C.B.S., P.S.P., G.C.); Stanford University, Palo Alto, Calif (R.B.J.); and Royal Melbourne Hospital, Parkville, Australia (D.L.S.). Recipient of a Certificate of Merit award for an education exhibit at the 2002 RSNA scientific assembly. Received March 28, 2003; revision requested June 27 and received August 15; accepted August 15. All authors have no financial relationships to disclose. Address correspondence to C.B.S. (e-mail: csirlin@ucsd.edu).

View larger version (130K): [in a new window]   Figure 1.  Disproportionate fat stranding. Axial contrast material-enhanced CT image of a man with pseudomembranous colitis shows severe wall thickening in the descending colon (arrows) that is disproportionately greater than the degree of fat stranding (arrowheads). This pattern indicates that the pathologic process is centered in the bowel wall, a finding characteristic of infection, pseudomembranous colitis, ischemia, and inflammatory bowel disease as the main differential diagnoses.

View larger version (119K): [in a new window]   Figure 2.  Disproportionate fat stranding. Axial nonenhanced CT image of a man with diverticulitis depicts fat stranding (arrowheads) that is disproportionately greater in severity than the degree of bowel wall thickening (arrow). This pattern indicates a predominantly pericolonic process and suggests a narrower differential diagnosis. Because of the presence of diverticula and the involvement of the left side of the colon, diverticulitis is the primary diagnostic consideration.

View larger version (137K): [in a new window]   Figure 3.  Diverticulitis. Axial CT image of a man with left-sided diverticulitis shows severe pericolonic fat stranding (arrowheads) that is greater than the degree of wall thickening of the descending colon (curved arrow). A "normal" diverticulum (open arrow) and a ill-defined (fuzzy) diverticulum (solid straight arrow) are also seen.

View larger version (124K): [in a new window]   Figure 4.  Diverticulitis and the comma sign. Axial nonenhanced CT image of a 47-year-old patient with cecal diverticulitis shows thickening of the lateral conal fascia, a finding known as the reverse comma sign (arrowhead). Note the mild wall thickening of the cecum (small arrow) and a diverticulum (large arrow).

View larger version (126K): [in a new window]   Figure 5.  Diverticulitis and the centipede sign. Axial contrast-enhanced CT image of a patient with diverticulitis shows engorgement of the vasa recta that feeds the sigmoid colon, a finding known as the centipede sign (open arrows). Note also the mild wall thickening of the colon (long solid arrow), diverticula (arrowheads), and fluid at the root of the sigmoid mesentery (short solid arrow).

View larger version (93K): [in a new window]   Figure 6a.  Acute right-sided diverticulitis. (a) Axial nonenhanced CT image shows mild wall thickening of the ascending colon (solid straight arrow) and moderate pericolonic fat stranding (open arrows). Diverticulum (curved arrow) and the reverse comma sign (arrowhead) are also present. (b) On an axial nonenhanced CT image obtained at a lower level than a, the appendix appears normal (arrow), a finding that rules out appendicitis.

View larger version (95K): [in a new window]   Figure 6b.  Acute right-sided diverticulitis. (a) Axial nonenhanced CT image shows mild wall thickening of the ascending colon (solid straight arrow) and moderate pericolonic fat stranding (open arrows). Diverticulum (curved arrow) and the reverse comma sign (arrowhead) are also present. (b) On an axial nonenhanced CT image obtained at a lower level than a, the appendix appears normal (arrow), a finding that rules out appendicitis.

View larger version (122K): [in a new window]   Figure 7a.  Transverse colon diverticulitis in a 62-year-old man. Axial nonenhanced (a) and contrast-enhanced (b) CT images show a fecalith within a diverticulum (solid straight arrow) surrounded by severe pericolonic fat stranding (arrowheads). Colonic wall thickening is mild (curved arrow) and scattered diverticula (open arrow) are present.

View larger version (133K): [in a new window]   Figure 7b.  Transverse colon diverticulitis in a 62-year-old man. Axial nonenhanced (a) and contrast-enhanced (b) CT images show a fecalith within a diverticulum (solid straight arrow) surrounded by severe pericolonic fat stranding (arrowheads). Colonic wall thickening is mild (curved arrow) and scattered diverticula (open arrow) are present.

View larger version (128K): [in a new window]   Figure 8.  Meckel diverticulitis in a 59-year-old man. Axial contrast-enhanced CT image shows a large outpouching (Meckel diverticulum) that extends from the ileal wall (arrows) with moderate wall thickening and severe stranding of the surrounding fat (arrowheads).

View larger version (119K): [in a new window]   Figure 9.  Jejunal diverticulitis in a woman with abdominal pain. Contrast-enhanced CT scan shows moderate fat stranding of the mesentery (arrowheads), immediately adjacent to jejunal diverticula (thin arrows), one of which is ill defined (thick arrow). Bowel wall thickening is mild; regional mesenteric vessels are engorged.

View larger version (129K): [in a new window]   Figure 10.  Colon adenocarcinoma. Axial contrast-enhanced CT image shows severe wall thickening (arrows) of the ascending colon with no fat stranding. This disproportionate degree of thickening suggests that the patient’s disease originates in the bowel wall.

View larger version (120K): [in a new window]   Figure 11a.  Colon adenocarcinoma. (a) Axial contrast-enhanced CT image of another patient shows wall thickening (arrows) of the descending colon that is disproportionately greater than the degree of fat stranding (arrowhead). (b) Axial contrast-enhanced CT image obtained at a lower level shows the abrupt transition from thick to normal wall ("shouldering") (short arrow) and the presence of lymphadenopathy (long arrow). Enlarged regional lymph nodes are more suggestive of colon cancer than of diverticulitis.

View larger version (101K): [in a new window]   Figure 11b.  Colon adenocarcinoma. (a) Axial contrast-enhanced CT image of another patient shows wall thickening (arrows) of the descending colon that is disproportionately greater than the degree of fat stranding (arrowhead). (b) Axial contrast-enhanced CT image obtained at a lower level shows the abrupt transition from thick to normal wall ("shouldering") (short arrow) and the presence of lymphadenopathy (long arrow). Enlarged regional lymph nodes are more suggestive of colon cancer than of diverticulitis.

View larger version (150K): [in a new window]   Figure 12.  Axial CT image shows normal appendices epiploicae (arrows) of the sigmoid colon, which appear as fingerlike projections of pericolic fat floating within ascites (*).

View larger version (155K): [in a new window]   Figure 13.  Epiploic appendagitis in a 23-year-old man. Axial contrast-enhanced CT image shows an ovoid mass (solid arrow) of fat attenuation anterior to the wall of the descending colon. The mass is surrounded by a hyperattenuated rim (representing thickened visceral peritoneum) and contains a central high-attenuation dot (most likely representing thrombosed central vessels). Note the moderate fat stranding (arrowhead) and mild focal thickening of the adjacent colonic wall (open arrow).

View larger version (155K): [in a new window]   Figures 14.  Epiploic appendagitis in a 46-year-old man. Axial contrast-enhanced CT image shows severe fat stranding (arrowheads) and a fatty ovoid mass (curved arrow) with a hyperattenuated rim and central dot (open arrow). Associated thickening of the colonic wall is mild (solid straight arrow).

View larger version (149K): [in a new window]   Figure 15.  Normal greater omentum. Axial contrast-enhanced CT image shows the normal layer of fat attenuation between the transverse colon and anterior abdominal wall (arrowheads). Mesenteric lymph nodes are mildly enlarged (arrows).

View larger version (163K): [in a new window]   Figure 16.  Omental infarction. Axial contrast-enhanced CT image of a patient who presented with acute right upper quadrant pain shows an inhomogeneous mass (arrow) in the greater omentum, anterior to the transverse colon. Moderate adjacent wall thickening is also evident (arrowhead). Diverticulitis was a diagnostic consideration, but no diverticula were seen at CT. A barium enema study performed 1 month later (not shown) revealed a normal colonic lumen without diverticula. Cholecystitis was also a consideration, but there was no inflammation of the fat immediately adjacent to the gallbladder, and the gallbladder appeared normal at ultrasonography (not shown) performed immediately after CT.

View larger version (174K): [in a new window]   Figure 17a.  Omental infarction in a 60-year-old woman with acute right upper quadrant pain. Axial contrast-enhanced CT images (a obtained at a higher level than b) show an inhomogeneous round, high-attenuation fatty mass (arrowheads) in the greater omentum, anterior to and exerting mass effect on the transverse colon (arrow in b).

View larger version (163K): [in a new window]   Figure 17b.  Omental infarction in a 60-year-old woman with acute right upper quadrant pain. Axial contrast-enhanced CT images (a obtained at a higher level than b) show an inhomogeneous round, high-attenuation fatty mass (arrowheads) in the greater omentum, anterior to and exerting mass effect on the transverse colon (arrow in b).

View larger version (132K): [in a new window]   Figure 18.  Omental infarction in a 60-year-old woman with acute right flank pain. Axial nonenhanced CT image shows an inhomogeneous, ill-defined ovoid fatty mass (arrowheads) centered in the greater omentum, distant from the ascending colon wall (arrow).

View larger version (153K): [in a new window]   Figures 19.  Appendicitis in a 21-year-old patient. Axial nonenhanced CT image shows a thickened appendix (white arrows) surrounded by marked fat stranding (arrowheads). Note the high-attenuation appendicolith (black arrow).

View larger version (132K): [in a new window]   Figures 20a.  Appendicitis in a 7-year-old boy. Axial contrast-enhanced CT images (a obtained at a higher level than b) show the high-attenuation wall of the dilated fluid-filled appendix (white arrow). Surrounding fat stranding is severe (arrowheads). Note mild posterolateral wall thickening of the cecum (cecal bar sign) (solid straight black arrow) and also the arrowhead-shaped collection of contrast agent (arrowhead sign) (curved arrow) formed as contrast material funnels into the partially coapted cecal wall adjacent to the occluded appendiceal orifice. An appendicolith is also seen (open arrow).

View larger version (122K): [in a new window]   Figures 20b.  Appendicitis in a 7-year-old boy. Axial contrast-enhanced CT images (a obtained at a higher level than b) show the high-attenuation wall of the dilated fluid-filled appendix (white arrow). Surrounding fat stranding is severe (arrowheads). Note mild posterolateral wall thickening of the cecum (cecal bar sign) (solid straight black arrow) and also the arrowhead-shaped collection of contrast agent (arrowhead sign) (curved arrow) formed as contrast material funnels into the partially coapted cecal wall adjacent to the occluded appendiceal orifice. An appendicolith is also seen (open arrow).

View larger version (126K): [in a new window]   Figure 21.  Appendicitis in a 72-year-old man. Axial nonenhanced CT image shows an enlarged appendix (open arrow) with an appendicolith (solid arrow), surrounded by relatively mild stranding (arrowhead) of the adjacent fat (cf Fig 22).

View larger version (182K): [in a new window]   Figure 22.  Appendicitis in a 32-year-old man. Axial nonenhanced CT image shows severe fat stranding (arrowheads) surrounding the enlarged appendix (open arrow). The fat stranding is disproportionately greater than the degree of wall thickening (black arrow) of the adjacent cecum. An appendicolith (solid white arrow) is also seen.

View larger version (113K): [in a new window]   Figure 23.  Appendicitis with perforation and abscess. Axial contrast-enhanced CT image shows focal disruption of the wall (black arrow) of the appendix. The disruption manifests as a focal interruption of the otherwise continuous mucosal enhancement (white arrow). An abscess (*) surrounds the appendix. Note also an appendicolith and mild bowel thickening.

View larger version (156K): [in a new window]   Figures 24.  Perforated appendix with peritonitis. Axial contrast-enhanced CT scan shows enhancement and disruption (arrow) of the appendiceal wall. Inflamed bowel wall and severe fat stranding are also present (arrowheads).

View larger version (164K): [in a new window]   Figure 25.  Crohn disease involving the terminal ileum and cecum. Axial CT image shows circumferential wall thickening of the cecum and terminal ileum (arrow) and fibrofatty proliferation ("creeping fat") (arrowheads). Note lack of substantial fat stranding.

View larger version (134K): [in a new window]   Figure 26a.  Diverticulitis that caused large bowel obstruction in a 22-year-old man. (a) Axial CT scan shows marked focal wall thickening of the sigmoid colon with abrupt shouldering (arrows), mild fat stranding (arrowheads), and the comma sign. (b) Axial CT scan obtained at a lower level shows diverticula (arrow). CT findings were considered indeterminate for differentiating diverticulitis and colon cancer. Endoscopic biopsy was performed, and a pathologic diagnosis of diverticulitis was made. There was no evidence of malignancy.

View larger version (124K): [in a new window]   Figure 26b.  Diverticulitis that caused large bowel obstruction in a 22-year-old man. (a) Axial CT scan shows marked focal wall thickening of the sigmoid colon with abrupt shouldering (arrows), mild fat stranding (arrowheads), and the comma sign. (b) Axial CT scan obtained at a lower level shows diverticula (arrow). CT findings were considered indeterminate for differentiating diverticulitis and colon cancer. Endoscopic biopsy was performed, and a pathologic diagnosis of diverticulitis was made. There was no evidence of malignancy.

View larger version (152K): [in a new window]   Figure 27.  Pancreatitis in a 45-year-old woman. Axial contrast-enhanced CT image shows marked fat stranding (arrows) adjacent to an enlarged pancreas and fluid in the anterior pararenal space (arrowheads), findings that are characteristic of pancreatitis.

View larger version (136K): [in a new window]   Figure 28.  Carcinomatous peritonitis in a patient with large bowel obstruction. Axial contrast-enhanced CT image shows mild wall thickening (white arrow) of the transverse colon adjacent to an area of heterogeneous attenuation in the greater omentum (arrowheads). Enlarged mesenteric lymph nodes (black arrow) are also seen.

View larger version (160K): [in a new window]   Figure 29a.  Mesenteric tuberculosis. (a) Contrast-enhanced CT scan shows thickening of the anterior wall of the transverse colon (arrow) adjacent to a focal area of heterogeneous attenuation in the greater omentum (arrowheads). Appearance is similar to that of omental infarction (cf Figs 16-18), but here the mesenteric mass has a nodular pattern not seen in omental infarction. (b) Contrast-enhanced CT scan shows enlarged periportal nodes (arrow).

View larger version (181K): [in a new window]   Figure 29b.  Mesenteric tuberculosis. (a) Contrast-enhanced CT scan shows thickening of the anterior wall of the transverse colon (arrow) adjacent to a focal area of heterogeneous attenuation in the greater omentum (arrowheads). Appearance is similar to that of omental infarction (cf Figs 16-18), but here the mesenteric mass has a nodular pattern not seen in omental infarction. (b) Contrast-enhanced CT scan shows enlarged periportal nodes (arrow).

View larger version (144K): [in a new window]   Figure 30a.  Mesenteric panniculitis in a 54-year-old man with colon cancer. (a) Axial contrast-enhanced CT image shows a solitary well-defined mass in the left side of the mesentery (arrowheads in a, open arrows in b) that has higher attenuation than that of retroperitoneal fat. Note the fatty halo surrounding the soft-tissue nodules and vessels (arrows). (b) Axial contrast-enhanced CT image obtained at a lower level shows irregular thickening of the proximal ascending colon (arrowheads) at the site of the patient’s colon cancer and small regional nodes (solid arrow). As illustrated by this case, mesenteric panniculitis has a poorly understood association with underlying malignancy. It does not represent a metastatic process, however; malignant cells are not present within the inflamed tissue.

View larger version (130K): [in a new window]   Figure 30b.  Mesenteric panniculitis in a 54-year-old man with colon cancer. (a) Axial contrast-enhanced CT image shows a solitary well-defined mass in the left side of the mesentery (arrowheads in a, open arrows in b) that has higher attenuation than that of retroperitoneal fat. Note the fatty halo surrounding the soft-tissue nodules and vessels (arrows). (b) Axial contrast-enhanced CT image obtained at a lower level shows irregular thickening of the proximal ascending colon (arrowheads) at the site of the patient’s colon cancer and small regional nodes (solid arrow). As illustrated by this case, mesenteric panniculitis has a poorly understood association with underlying malignancy. It does not represent a metastatic process, however; malignant cells are not present within the inflamed tissue.

View larger version (169K): [in a new window]   Figure 31.  Mesenteric panniculitis. Axial contrast-enhanced CT image shows a well-defined fatty inhomogeneous mass (solid arrows) with a hyperattenuating peripheral rim (arrowheads). Note the fatty halo surrounding the mesenteric vessels and nodes (open arrow).