Radiologists' Guide to the Whirl Sign

Transcription

1 Radiologists' Guide to the Whirl Sign Poster No.: C-1478 Congress: ECR 2015 Type: Educational Exhibit Authors: B. layton, R. magennis, V. Rudralingam, S. Sukumar; Manchester/ UK Keywords: Ischemia / Infarction, Computer Applications-Detection, diagnosis, CT, Gastrointestinal tract, Colon, Abdomen, Volvulus DOI: /ecr2015/C-1478 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 44

2 Learning objectives Recognise characteristic appearance of the "whirl sign." Understand the mechanism of abnormal rotation. Differentiate the radiological appearances of underlying causes. Identify radiological features of potential complications. Background The first "whirl sign" was described in 1981 by Fisher who observed, in a patient with midgut volvulus "This pattern of encircling loops of bowel around the superior mesenteric 1 artery creates a whirl-like pattern on CT". The application of the term was expanded to include the large bowel four years later by Shaff et al.. 2 The image of the whirl (figure 1) comprises a spiral of Low attenuation mesenteric fat Vasculature (high attenuation on the contrast enhanced scan) 3,4. Soft tissue attenuation of the wall of collapsed bowel Fig. 1: Three Whirls: Sagittal CT slice perpendicular to the axis of a whirl (left) and sketch emphasising the componenents (middle) showing low attenuation mesenteric fat (dotted arrow), high attenuation contrast enhanced vessels (arrow) and soft tissue attenuation bowel wall (dashed arrow); representing the site of obstructiion in a patient with caecal volvulus. Direct comparison can be made with a sketch of a whirl pool (right). Page 2 of 44

3 References: - Manchester/UK The mesenteric whirl sign is recognised in the acute setting with Small bowel and large bowel volvulus Closed loop obstruction, secondary to internal hernias or adhesive bands The whirl sign is also well recognised as an incidental finding in the post-operative patient, after procedures such as hemicolectomy, Whipple's procedure and gastric bypass. in any extra-intestinal structure that is suspended within the abdominal cavity, such as the ovary. Recognition of the whirl sign is critical because of the association with closed loop obstruction with the potential for bowel ischaemia. Images for this section: Fig. 1: Three Whirls: Sagittal CT slice perpendicular to the axis of a whirl (left) and sketch emphasising the componenents (middle) showing low attenuation mesenteric fat (dotted arrow), high attenuation contrast enhanced vessels (arrow) and soft tissue attenuation bowel wall (dashed arrow); representing the site of obstructiion in a patient with caecal volvulus. Direct comparison can be made with a sketch of a whirl pool (right). Page 3 of 44

4 Findings and procedure details The whirl sign is A non-specific sign, alerting radiologists to probability of associated acute pathology Not pathognomonic, clinical correlation crucial when whirl identified Best seen when the image plane is perpendicular to the axis of the whirl on cross sectional imaging With the benefit of multi-planar CT reconstruction Images can be optimised for the demonstration of the whirl 12 Scroll facility on workstations also aids detection The whirl sign has been recognised in several large investigations to be highly specific for volvulus. Patients with signs of small bowel obstruction are 25 times more likely to need surgery if the whirl sign is present. 6,7,8 We present a series of cases with the whirl sign In the acute setting or as an incidental finding Highlighting common underlying aetiology Emphasising the importance of associated radiological features Video clips are presented to demonstrate the benefit of evaluating a dynamic sequence of CT slices in discovering the whirl (figures 2 and 3). Page 4 of 44

5 Fig. 2: Sigmoid volvulus: Video demonstrating the value of the scroll facility for full appreciation of the whirl sign and extent of the torsion. There is gross proximal dilatation of the large bowel consistent with obstruction secondary to sigmoid volvulus. References: - Manchester/UK Page 5 of 44

6 Fig. 3: Caecal Volvulus: Video demonstrating the value of using multi-planar reconstruction and the scroll facility in recognising the whirl sign. The images are reconstructed in the sagittal plane which is perpendicular to the axis of the whirl. The whirl sign is seen anterior to the vertebral body of L5. References: - Manchester/UK CAUSES OF THE WHIRL SIGN The causes of a whirl sign in the gastrointestinal tract, can be separated into Small bowel volvulus (SBV) (primary) Colonic volvulus Closed loop obstruction due to adhesive bands or internal hernias (secondary volvulus) (figure 4) Page 6 of 44

7 Fig. 4: Sketches illustrating formation of a fulcrum which predisposes to closed loop obstruction and volvulus. Bowel restricted by a fibrous adhesion (top left) and internal hernia with trapped bowel(top right)both predispose Page 7 of 44

8 to formation of the closed loop obstruction demonstrating "double beak sign" (bottom left) and ultimately volvulus (bottom right). References: - Manchester/UK The process of formation of a volvulus results in vascular compromise and closed loop obstruction. The whirl sign can also be seen in particular post-operative groups as an incidental fininding. The whirl can be appreciated in any structure suspended within the abdomen and so may also be seen in the ovary or even gall bladder. Small Bowel Volvulus Small bowel volvulus is a rare but life threatening surgical emergency, associated with small bowel obstruction with a risk of strangulation. 10 Primary (or idiopathic) SBV is rare in the west, but can be up to ten times more common in Africa and Asia (thought to be due to high fibre diet coupled with periods of fasting). 11, Page 8 of 44

9 Fig. 5: Primary Small Bowel Volvulus: Classic depiction of whirl sign with mesenteric fat, bowel wall and mesenteric vessels. References: - Manchester/UK Secondary SBV results from either congenital (malrotation) or acquired anatomical abnormalities which result in the formation of a fixed fulcrum - akin to the base of a tornado (figure 4). Usually due to trapped bowel related to congenital or post-operative adhesive bands and internal hernias Rare causes include tumours, intussusception and enteroenterostomy Malrotation is the principal cause of volvulus in children 11,12 Page 9 of 44

10 Fig. 6: Small Bowel Volvulus: A series of images demonstrating the double beak sign (curved arrows) and whirl sign (circled) in a patient with surgically proven closed loop obstruction secondary to adhesions. Note reactive peritoneal free fluid (dotted arrow) and mural oedema (arrow). References: - Manchester/UK Large Bowel Volvulus Large bowel volvulus occurs when part of the colon twists on its own mesentery The usual sites are: Redundant sigmoid colon (57%) Caecum: in the 11-25% of the population failure of posterior peritoneal fixation results in mobile proximal colon/caecum 3 The longer the mesentery, the higher the propensity to volvulus (Figure 7). Page 10 of 44

11 Fig. 7: Sketches illustrating the difference between normal broad based mesocolon and peritoneal attachment(left) and narrow, redundant mesocolon resulting in a mobile large bowel prone to torsion(right). References: - Manchester/UK Page 11 of 44

12 Fig. 8: Sigmoid Volvulus: Gross dilatation of the large bowel with whirl sign (circled) and "beak" sign (arrow) in a patient with sigmoid volvulus. This patient had a long redundant sigmoid mesocolon (see figure 7). References: - Manchester/UK Page 12 of 44

13 Fig. 9: Caecal Volvulus: Axial CT shows whirl of mesenteric vessels and fat (arrows). Dilated small bowel loops, target sign representing mural oedema noted in the distal ileum(arrowheads) and mesenteric oedema. Malpositioned caecum best seen on reformatted images (figures 10 and 11). References: - Manchester/UK Page 13 of 44

14 Page 14 of 44

15 Fig. 10: Caecal Volvulus: Sagittal CT image optimally demonstrates the whirl of mesenteric fat and vessels with associated congestion and engorgement(circled). References: - Manchester/UK Page 15 of 44

16 Page 16 of 44

17 Fig. 11: Caecal Volvulus: Coronal CT image demonstrates caecal volvulus with the tip of the caecum in the right upper quadrant (arrow). The adjacent bowel loops appear thickened with mural oedema (arrowhead). References: - Manchester/UK Closed Loop Obstruction Closed loop obstruction is obstruction of the bowel at two adjacent points. It is seen on cross sectional imaging as the "double beak" sign representing the abrupt narrowing of the distal afferent loop and the proximal efferent loop (figures 12 and 13). The progression to the whirl sign should raise the suspicion of compicated closed loop obstruction. The anatomical configuration in closed loop obstruction results in vascular compromise which is exacerbated if a volvulus forms. It is life threatening and requires urgent surgical intervention more commonly 13 than simple bowel obstruction. Page 17 of 44

18 Fig. 12: Double Beak Sign: Sketches of bird beaks superimposed over the abruptly narrowing loops of small bowel to emphasise the beak like appearance in a patient with closed loops obstruction with volvulus secondary to adhesions (same patient as figure 6). References: - Manchester/UK Fig. 13: Closed Loop Obstruction: Axial CT slices from the same scan demonstrating the "double beak" sign at the level of obstruction(dotted arrows). Note vascular compromise resulting in congested mesentery (arrow) and oedematous bowel wall resulting in "target sign" (dashed arrow). References: - Manchester/UK GASTROINTESTINAL COMPLICATIONS In small and large bowel, the twist mechanism around the mesentery impedes the vascular supply and from this point intestinal ischaemia, perforation and death are 14 imminent. The tightness of the whirl seen on the scan correlates with the severity of vascular compromise. 2 Signs of vascular compromise are: Bowel wall thickening with "target sign"; alternating layers of high and low attenuation, due to oedema or haemorrhage (figure 13). Variable bowel wall attenuation and contrast enhancement (figure 18). Thin or absent wall indicating gangrenous bowel. Engorgement of mesenteric veins and resultant mesenteric oedema (figure 13). Intramural gas (pneumatosis intestinalis) (figure 5). Page 18 of 44

19 Mesenteric / portal vein gas. Free fluid (figure 6). Free gas indicating perforated segment. Fig. 14: Small Bowel Volvulus: Sequential images demonstrating the serious nature of the whirl sign. Above - whirl sign in a patient with a surgical history of partial gastrectomy. Below - repeat CT, 5 days later, demonstrating pneumatosis intestinalis secondary to infarcted bowel(arrows). References: - Manchester/UK Whirl sign in Post-Operative Cohort The whirl sign may be seen as an incidental finding postoperatively, particularly following procedures such as gastric bypass, Whipple's procedure and hemicolectomy, where up to 180 degrees of rotation of the bowel may occur. 15 Page 19 of 44

20 The appearance of the non-pathological post-operative whirl is distinctive enough that a 1 trained radiologist should not be fooled. Fig. 15: Post-operative Whirl: Axial CT shows a whirl of mesenteric fat and vessels (arrows), an incidental finding post Whipple's procedure. The mesenteric fat planes are normal and there is no associated dilatation of small bowel loops or evidence of obstruction or ischaemia. References: - Manchester/UK Page 20 of 44

21 Fig. 16: Post-operative Whirl: Axial CT shows a whirl of mesenteric fat and vessels (arrows), an incidental finding following gastric bypass surgery. No evidence of small bowel obstruction or features of ischaemia. Patient clinically well. References: - Manchester/UK Apparent Whirl Mobile small bowel "sweeping over" congenital or post-operative fibrous bands with or without obstruction can mimic a partial whirl on CT when viewed perpendicular to the axis of the curve. A loop of bowel entering and exiting internal hernias can give a similar appearance (figures 17, 18 and 19). Page 21 of 44

22 Fig. 17: Sketch demonstrating bowel looping over an adhesional band (left). When viewed in the plane shown in red, the loop can give an apparent whirl type appearance or "pseudowhirl". Examples seen on figures 13 and 18. References: - Manchester/UK Page 22 of 44

23 Fig. 18: Closed loop obstruction. Series of images of the same patient demonstrating small bowel folding over an adhesion resulting in the apearence of a "pseudowhirl" (circled)(see also figure X). Alarming associated features of strangulation present: non-enhancing loops of bowel consistent with ischaemia (arrows)and submucosal oedema causing the water halo or "target" sign (arrowhead). Note the presence of double beak sign (curved arrow) indicating closed loop obstruction with mesenteric oedema (dotted arrow). Reactive free intra-abdominal fluid also present(dashed arrow). References: - Manchester/UK Page 23 of 44

24 Fig. 19: Axial CT demonstrates a right paraduodenal hernia (arrows). Note clustering of dilated small bowel loops in a radial distribution and anteriorly displaced right colic vein (arrowhead). This is an example of a "pseudowhirl" caused by the relationship between the bowel and the hernial orifice as described in figure 17. There is a predisposition to volvulus. References: - Manchester/UK Extra-Intestinal Whirl Due to the nature of whirl formation it can be identified in the torsion of any suspended intra-abdominal structure. We present a case of a twisted ovarian fibroma as an example depicting whirl sign at the pedicle (figure 20). Page 24 of 44

25 Fig. 20: Axial T2W MRI of the pelvis demonstrates a heterogenous low signal intensity mass (arrow), characteristic of an ovarian fibroma. Note the presence of a whirl of the vascular pedicle in the right adnexa indicating a tortion requiring prompt gynaecological attention(magnified). References: - Manchester/UK Images for this section: Page 25 of 44

26 Fig. 2: Sigmoid volvulus: Video demonstrating the value of the scroll facility for full appreciation of the whirl sign and extent of the torsion. There is gross proximal dilatation of the large bowel consistent with obstruction secondary to sigmoid volvulus. Page 26 of 44

27 Fig. 3: Caecal Volvulus: Video demonstrating the value of using multi-planar reconstruction and the scroll facility in recognising the whirl sign. The images are reconstructed in the sagittal plane which is perpendicular to the axis of the whirl. The whirl sign is seen anterior to the vertebral body of L5. Page 27 of 44

28 Fig. 4: Sketches illustrating formation of a fulcrum which predisposes to closed loop obstruction and volvulus. Bowel restricted by a fibrous adhesion (top left) and internal hernia with trapped bowel(top right)both predispose to formation of the closed loop Page 28 of 44

29 obstruction demonstrating "double beak sign" (bottom left) and ultimately volvulus (bottom right). Fig. 5: Primary Small Bowel Volvulus: Classic depiction of whirl sign with mesenteric fat, bowel wall and mesenteric vessels. Page 29 of 44

30 Fig. 6: Small Bowel Volvulus: A series of images demonstrating the double beak sign (curved arrows) and whirl sign (circled) in a patient with surgically proven closed loop obstruction secondary to adhesions. Note reactive peritoneal free fluid (dotted arrow) and mural oedema (arrow). Fig. 7: Sketches illustrating the difference between normal broad based mesocolon and peritoneal attachment(left) and narrow, redundant mesocolon resulting in a mobile large bowel prone to torsion(right). Page 30 of 44

31 Fig. 8: Sigmoid Volvulus: Gross dilatation of the large bowel with whirl sign (circled) and "beak" sign (arrow) in a patient with sigmoid volvulus. This patient had a long redundant sigmoid mesocolon (see figure 7). Page 31 of 44

32 Fig. 9: Caecal Volvulus: Axial CT shows whirl of mesenteric vessels and fat (arrows). Dilated small bowel loops, target sign representing mural oedema noted in the distal ileum(arrowheads) and mesenteric oedema. Malpositioned caecum best seen on reformatted images (figures 10 and 11). Page 32 of 44

33 Page 33 of 44

34 Fig. 10: Caecal Volvulus: Sagittal CT image optimally demonstrates the whirl of mesenteric fat and vessels with associated congestion and engorgement(circled). Page 34 of 44

35 Page 35 of 44

36 Fig. 11: Caecal Volvulus: Coronal CT image demonstrates caecal volvulus with the tip of the caecum in the right upper quadrant (arrow). The adjacent bowel loops appear thickened with mural oedema (arrowhead). Fig. 12: Double Beak Sign: Sketches of bird beaks superimposed over the abruptly narrowing loops of small bowel to emphasise the beak like appearance in a patient with closed loops obstruction with volvulus secondary to adhesions (same patient as figure 6). Page 36 of 44

37 Fig. 13: Closed Loop Obstruction: Axial CT slices from the same scan demonstrating the "double beak" sign at the level of obstruction(dotted arrows). Note vascular compromise resulting in congested mesentery (arrow) and oedematous bowel wall resulting in "target sign" (dashed arrow). Fig. 14: Small Bowel Volvulus: Sequential images demonstrating the serious nature of the whirl sign. Above - whirl sign in a patient with a surgical history of partial gastrectomy. Below - repeat CT, 5 days later, demonstrating pneumatosis intestinalis secondary to infarcted bowel(arrows). Page 37 of 44

38 Fig. 15: Post-operative Whirl: Axial CT shows a whirl of mesenteric fat and vessels (arrows), an incidental finding post Whipple's procedure. The mesenteric fat planes are normal and there is no associated dilatation of small bowel loops or evidence of obstruction or ischaemia. Page 38 of 44

39 Fig. 16: Post-operative Whirl: Axial CT shows a whirl of mesenteric fat and vessels (arrows), an incidental finding following gastric bypass surgery. No evidence of small bowel obstruction or features of ischaemia. Patient clinically well. Page 39 of 44

40 Fig. 17: Sketch demonstrating bowel looping over an adhesional band (left). When viewed in the plane shown in red, the loop can give an apparent whirl type appearance or "pseudowhirl". Examples seen on figures 13 and 18. Fig. 18: Closed loop obstruction. Series of images of the same patient demonstrating small bowel folding over an adhesion resulting in the apearence of a "pseudowhirl" (circled)(see also figure X). Alarming associated features of strangulation present: non-enhancing loops of bowel consistent with ischaemia (arrows)and submucosal oedema causing the water halo or "target" sign (arrowhead). Note the presence of double beak sign (curved arrow) indicating closed loop obstruction with mesenteric oedema (dotted arrow). Reactive free intra-abdominal fluid also present(dashed arrow). Page 40 of 44

41 Fig. 19: Axial CT demonstrates a right paraduodenal hernia (arrows). Note clustering of dilated small bowel loops in a radial distribution and anteriorly displaced right colic vein (arrowhead). This is an example of a "pseudowhirl" caused by the relationship between the bowel and the hernial orifice as described in figure 17. There is a predisposition to volvulus. Page 41 of 44

42 Fig. 20: Axial T2W MRI of the pelvis demonstrates a heterogenous low signal intensity mass (arrow), characteristic of an ovarian fibroma. Note the presence of a whirl of the vascular pedicle in the right adnexa indicating a tortion requiring prompt gynaecological attention(magnified). Page 42 of 44

43 Conclusion The whirl sign is seen in small and large bowel volvulus and is associated with closed loop obstruction. It is an alarming discovery as it can indicate a life threatening pathology. Our examples emphasise that the whirl sign should arouse suspicion of an acute surgical emergency, but that clinical correlation is paramount. There are instances where the whirl may not represent pathology and the presence of associated signs adds weight to the radiologists' suspicions of a surgical emergency. Personal information References Fisher JK. Computed tomographic diagnosis of volvulus in intestinal malrotation. Radiology 1981; 140: Shaff MI, Himmelfarb E, Sacks GA, Burks DD, Kulkarni MV. The whirl sign: a CT finding in volvulus of the large bowel. J Comput Assist Tomogr 1985 ;9:410. Moore CJ, Corl FM, Fishman EK. CT of the cecal volvulus. AJR Am J Roentgenol 2001; 177: Khurana B. The whirl sign. Radiology 2003; 226: Vandendries, C.; Jullès, M. C.; Boulay-Coletta, I.; Loriau, J.; Zins, M Diagnosis of colonic volvulus: findings on multidetector CT with threedimentional reconstructions. British Journal of Radiology 2010, Vol : 983. Donckier V, Closset J, Van Gansbeke D, et al. Contribution of computed tomography to decision making in the management of adhesive small bowel obstruction. Br J Surg 1998; 85: Gollub MJ, Yoon S, Smith LM, Moskowitz CS. Does the CT whirl sign really predict small bowel volvulus? Experience in an oncologic population. J Comput Assist Tomogr 2006; 30: Duda JB, Bhatt S, Dogra, VS. Utility of CT Whirl Sign in Guiding Management of Small-Bowel Obstruction. AJR Am J Roentgenol. 2008, 191: 3. Chang CC, Lin M, Sun J, Tsai K, Fan C. An extremely rare case of whirl sign in combination with colonic pneumatosis intestinalis: What is your provisional diagnosis? Journal of Acute Medicine 2012, Vol 2, 4: Page 43 of 44

44 10. Juler GL, Stemmer EA, Connoly JE. Preoperative diagnosis of small bowel volvulus in adults. Am J Gastroenterol 1971 ; 56: de Korte N, Grutters CT, Snellen JPJ. Small bowel volvulus diagnosed by the CT "whirl sign". Gastrointestinal Surgery 2008;12(8): Suarez Vega VM, Marti de Gracia M, Veron Sanchez A, Alonso Gamarra E, Garzon Moll G. Trapped on the "whirl": diagnostic sign on emergency CT Emergency Radiology (2): Hashimoto M, Miyauchi T, Watanabe O, Tomura N, Watarai J. Computed tomographic appearance of closed-loop obstruction. Radiat.Med 1995;13: Levsky JM, Den EI, DuBrow RA, Wolf EL, Rozenblit AM. CT findings of sigmoid volvulus.ajr Am J Roentgenol Jan;194(1): Blake MP, Mendelson RM. The whirl sign: a non-specific finding of mesenteric rotation. Australas Radiol 1996; 40: Page 44 of 44