DOI: 10.1148/radiol.2413052067
(Radiology 2006;241:947-948.)
© RSNA, 2006
Regarding the Spoke Wheel Sign
Adriaan van Breda Vriesman, MD
Department of Radiology, Rijnland Hospital, Simon Smitweg 1, NL-2350 CC, Leiderdorp, the Netherlands
e-mail: adriaanbreda{at}hotmail.com
Editor:
In the December 2005 issue of Radiology (1) Dr Rudloff describes the computed tomographic (CT) finding of a "spoke wheel" in the mesentery as a sign of small-bowel volvulus. His article provides extensive information about this form of intestinal obstruction, discussing its causes and clinical importance and also describing other signs that indicate this diagnosis.
However, the title of the report and the Signs in Imaging section in which it was published promise a focus on this imaging sign and not on a specific diagnosis. That promise is not fulfilled, as the report does not mention any differential diagnosis based on the imaging sign. It is a basic concept in radiology that the value of an imaging finding depends on its differential diagnosis, and by focusing only on small-bowel volvulus the implicit suggestion is being made that this CT sign is pathognomonic. That suggestion is incorrect, however, as various other conditions may manifest a stellate or spoke wheel appearance of the mesentery, such as a carcinoid tumor, carcinomatosis, or sclerosing mesenteritis (2).
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References
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- Rudloff U. The spoke wheel sign: bowel. Radiology 2005;237:1046–1047.[Free Full Text]
- Sheth S, Horton KM, Garland MR, Fishman EK. Mesenteric neoplasms: CT appearances of primary and secondary tumors and differential diagnosis. RadioGraphics 2003;23(2):457–473.[Abstract/Free Full Text]
Response
Udo Rudloff, MD
Department of Surgery, New York University Medical Center, 462 First Avenue, NBV 15N1, New York, NY 10016
e-mail: rudlou01{at}med.nyu.edu
I thank Dr van Breda Vriesman for the valuable comments on the diagnostic specificity and accuracy of the described "Spoke Wheel Sign: Bowel."
Involvement of the small-bowel mesentery by different neoplastic and inflammatory processes may show a stellate or spoke wheel appearance of the mesentery on abdominal CT images. Pantongrag-Brown et al (1) reviewed CT findings of 29 cases of proved mesenteric carcinoid tumors. All cases showed varying degrees of soft-tissue strands radiating from the centrally located mesenteric mass to adjacent bowel loops. The degree of radiating strands detected at CT correlated with the degree of fibrosis induced by the tumor. In line with prior observations on mesenteric carcinoid tumors (2,3), the authors describe the radiating linear soft-tissue densities as a stellate or spoke wheel configuration and conclude that the triad of a calcified mesenteric mass, radiating mesenteric strands, and adjacent bowel wall thickening is characteristic of and highly specific for mesenteric carcinoid tumors on abdominal CT images. In a review of CT appearances of common and rare mesenteric neoplasms, Sheth et al (4) expand on pathologic mesenteric processes that may appear as a stellate configuration with or without a central mass on CT images. In sclerosing mesenteritis, a rare inflammatory condition of unknown origin, areas of fibrosis within inflamed mesenteric fat may appear as linear bands of soft-tissue attenuation (5). Peritoneal carcinomatosis, particularly if caused by breast, gastric, pancreatic, or ovarian cancer, and peritoneal lymphomatosis may show a stellate appearance on abdominal CT images (4). The stellate appearance is caused by microscopic infiltration of tumor along the mesenteric blood vessels leading to perivascular soft-tissue thickening and increased attenuation in the mesenteric fat.
However, the stellate appearance of the mesentery caused by the aforementioned different infiltrative and inflammatory processes is different from the appearance of the spoke wheel sign of the bowel, as described initially by Jaramillo and Raval (6) and reviewed by others (7,8). The spoke wheel sign describes the radial arrangement of fluid-filled, dilated small-bowel loops connected to stretched and engorged mesenteric vascular structures that converge to the center of the mesentery. Soft-tissue masses connected to the radiating strands are not part of the spoke wheel sign. The stretched and engorged mesenteric vessels reach the concentrically arranged small-bowel loops and do not end in a spicular pattern in the mesentery like in the stellate appearance of infiltrative mesenteric processes. Both the radially arranged small-bowel loops and the linear converging mesenteric structures are key elements of the spoke wheel sign. In the absence of soft-tissue masses, these CT findings are highly suggestive, although not pathognomonic, of small-bowel volvulus.
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References
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- Pantongrag-Brown L, Buetow PC, Carr NJ, Lichtenstein JE, Buck JL. Calcification and fibrosis in mesenteric carcinoid tumor: CT findings and pathologic correlation. AJR Am J Roentgenol 1995;164:387–391.[Abstract/Free Full Text]
- Picus D, Glazer HS, Levitt RG, Husband JE. Computed tomography of abdominal carcinoid tumors. AJR Am J Roentgenol 1984;143:581–584.[Abstract/Free Full Text]
- Cockey BM, Fishman EK, Jones B, Siegelman SS. Computed tomography of abdominal carcinoid tumor. J Comput Assist Tomogr 1985;9:38–42.[Medline]
- Sheth S, Horton KM, Garland MR, Fishman EK. Mesenteric neoplasms: CT appearances of primary and secondary tumors and differential diagnosis. RadioGraphics 2003;23:457–473.[Abstract/Free Full Text]
- Sabate JM, Torrubia S, Maideu J, Franquet T, Monill JM, Perez C. Sclerosing mesenteritis: imaging findings in 17 patients. AJR Am J Roentgenol 1999;172:625–629.[Abstract/Free Full Text]
- Jaramillo D, Raval B. CT diagnosis of primary small-bowel volvulus. AJR Am J Roentgenol 1986;147:941–942.[Free Full Text]
- Balthazar EJ, Birnbaum BA, Megibow AJ, Gordon RB, Whelan CA, Hulnick DH. Closed-loop and strangulating intestinal obstruction: CT signs. Radiology 1992;185:769–775.[Abstract/Free Full Text]
- Rudloff U. The spoke wheel sign: bowel. Radiology 2005;237:1046–1047.[Free Full Text]
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