MDCT imaging in perforated sigmoid diverticulitis: depicting the intraperitoneal and extraperitoneal spreading routes of disease

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1 MDCT imaging in perforated sigmoid diverticulitis: depicting the intraperitoneal and extraperitoneal spreading routes of disease Poster No.: C-2388 Congress: ECR 2012 Type: Educational Exhibit Authors: N. Bernal Garnés, E. MIRALLES AZNAR, C. F. Munoz-Nunez, J. Carreres Polo, R. Mut Pons, S. Tigges; Torrevieja/ES Keywords: Inflammation, Diverticula, Abscess, Diagnostic procedure, CT, Gastrointestinal tract, Emergency, Abdomen DOI: /ecr2012/C-2388 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 29

2 Learning objectives To illustrate the spectrum of appearences of perforated sigmoid diverticulitis and to depict the intraperitoneal and extraperitoneal spreading of the disease with Multidetector Computed Tomography (MDCT). Background INTRODUCTION AND EPIDEMIOLOGY Colonic diverticulosis refers to small outpouchings of the colonic mucosa through the colonic wall at sites of vascular perforation. Diverticulosis has been considered a disease of western civilization because of its striking geographic variability, rare in rural Africa and Asia, it has the highest prevalence in USA, Europe, and Australia. This geographic variability and a correlation with the western diet (low fibre, long transit times and low mean stool) have long suggested a dietary factor as fundamental in the pathogenesis of colonic diverticulosis. Diverticulosis is much less common in Asian patients and more likely to occur in the proximal colon when compared to their Western counterparts, in whom the sigmoid colon is the most commonly affected segment (95% of the cases). th Data show a substantial rise in colonic diverticula from the beginning of the 20 century. Prevalence of diverticular disease increases with age, from less than 10% in people younger than 40 years of age to 50-66% in patients older than 80 years of age. Many patients with diverticular disease remain asymptomatic, but approximately 20% of them will experience an event of diverticulitis at some time in their life, ranging in severity from a single, mild, brief bout of diverticulitis to more severe attacks characterized by perforation and abscess formation, occasionally resulting in chronic complications such as obstruction and fistula formation. Acute diverticulitis is complicated by perforation in 8% of the cases (Fig. 1 on page 5). Computed tomography (CT) has proved to be highly accurate in the detection and evaluation of the extension of acute sigmoid diverticulitis, and for the percutaneous drainage of localized abscess. Page 2 of 29

3 PATHOGENESIS OF DIVERTICULAR DISEASE The etiology of diverticulosis is multi-factorial and may be the result of a combination of age, diet and colonic anatomy and motility. A low fibre diet results in raised intracolonic pressure and delayed transit times, predisposing to herniation of the mucosa through the muscularis propria and diverticula formation. Diverticula consist of herniated colonic mucosa and traces of muscularis mucosae through de muscularis propia of the colonic wall (i.e. pseudodiverticula) and are included within the adipose tissue in the subserosal layer of the colon. These herniations are located at specific areas of inherent weakness, where vessels, nerves and lymphatics penetrate this colonic wall. The muscularis propia of the colon consist of two layers, the complete circular or deep layer and the incomplete longitudinal or superficial layer (condensed in three discrete longitudinal bands called taenia coli, the mesenteric taenia (close to the mesocolon) and the two antimesenteric taenia). The diverticula are located between the mesenteric tenia and the two antimesenteric taenia, in each location two rows of diverticula are formed. Once diverticula are present their narrow neck makes them likely to retain material and getting obstructed. Obstruction of a diverticulum by faecal material causes accumulation of mucus secretions and overgrowth of normal colonic bacteria and inflammation occurs. Inflammation usually begins at the apex of the diverticula and seldom involves the neck or the proximal mucosa. The thin-walled diverticulum, consisting almost entirely of mucosa is highly susceptible to vascular compromise, followed by focal necrosis and subsequent microperforation allowing local bacterial proliferation in the surrounding pericolic fat, mesentery and serosa. Since many diverticula are adjacent to or within the mesocolon or appendices epiploicae, the walling off and localization of the perforation are common. If this progresses, a collection of pus may form and in some cases becomes walled off by pericolic fat, to form a small pericolic abscess. If the collection enlarges it may involve loops of small bowel, omentum or the pelvic peritoneum forming a localized abscess. If the pus is not contained, contamination of the abdominal cavity occurs producing purulent peritonitis, it is worth noting that acute peritonitis as a complication of acute diverticulitis is usually the result of the rupture of a previous abscess rather than true rupture of an inflamed diverticulum, early rupture of an inflamed diverticulum and peritonitis can occur and this is often because of the thin wall of the diverticulum. Persistent localized inflammation results in a phlegmon. The infection can also spread systemically causing bacteriemia and sepsis. Page 3 of 29

4 In the less common free perforation of the colon there is no obstruction of the diverticulum neck and a direct communication between the sigmoid colon lumen and the peritoneal cavity occurs causing faecal peritonitis. Fistula occur in % of patients, 65% are colovesical and 20% colovaginal. Colon diverticulitis is complicated by perforation in approximately 8% of patients. Because diverticula are confined almost exclusively to the area between the mesenteric and the antimesenteric taenia, perforation to the retroperitoneal space or the subperitoneal space (sigmoid mesocolon) is seen less often than free or paracolic rupture. CLINICAL FEATURES Acute diverticulitis typically presents with fever, left lower quadrant abdominal pain and leukocytosis in an adult. Alternative diagnoses for lower abdominal pain must be considered: Acute appendicitis Crohn s disease Pelvic inflammatory disease Tubal pregnancy Cystitis Advanced colonic cancer Infectious colitis Epiploic appendicitis Perforated ulcus Ovarian torsion Ischemic colitis Mesenteric adenitis Reno-ureteral colic There is a clinical classification made by The European Association for Endoscopic Surgeons (EAES) to stratify patients with acute diverticulitis (Fig. 2 on page 5). When the spreading of the disease is to the subperitoneal and extraperitoneal spaces the symptoms are more obscure. Since the extraperitoneal tissues do not react as acutely and severely to bacterial contamination as the peritoneal cavity does, symptoms and clinical signs of extraperitoneal perforation of the gastrointestinal tract may be obscure, delayed, nonspecific, or misleading. Page 4 of 29

5 Images for this section: Fig. 1: Diverticular disease is a term used to describe people with diverticulosis, either asymptomatic or symptomatic due to diverticulitis which usually causes pain, nausea, vomiting and diarrhea. Page 5 of 29

6 Fig. 2: The European Association for Endoscopic Surgeons(EAES) has devised a clinical classification scheme to stratify patients with acute diverticulitis. This classification is based on clinical presentation and can be and aid for guiding subsequent steps in diagnostic testing. The addition of computed tomography (CT) findings to the clinical presentation allows clinicians to accurately determine the need for hospitalization and surgical intervention. Page 6 of 29

7 Imaging findings OR Procedure details IMAGING TECHNIQUES IN THE DIAGNOSIS OF ACUTE DIVERTICULITIS Although some physicians treat patients with known diverticulosis and signs of uncomplicated diverticulitis without imaging confirmation, imaging is very helpful in diagnosing, staging and treatment planning this disease, imaging can give also alternative diagnosis and can be used for percutaneous drainage of a localized abscess. Computed tomography (i.e. Multidetector Computed Tomography or MDCT) is currently the imaging modality of choice for diagnosing and staging acute sigmoid diverticulitis with reported sensitivities and specificities close to 100%. Several classification have been developed for staging diverticular disease and acute diverticulitis (Fig. 3 on page 10, Fig. 4 on page 11 and Fig. 5 on page 11). The multiplanar capabilities and near isotropic resolution of MDCT allow a better understanding of acute diverticulitis and a better depiction of the spreading routes of the disease. The MDCT technique used for the diagnosis of diverticulitis varies among institutions. A comprehensive MDCT study involves the abdomen and pelvis and includes intravenous, oral and rectal positive contrast. But studies can be done with or without intravenous contrast media, and with or without the addition of positive oral and/or rectal contrast. One of the main disadvantages of MDCT is ionizing radiation exposure. Ultrasonography and MRI avoid the use of ionizing radiation, and can be used safely in females of childbearing age. Transabdominal ultrasound has reported sensitivities and specificities of 77-98% and 80-99% respectively. Drawbacks of ultrasound is that is operator-dependent, not as sensitive as CT for diagnosing complications and identifying alternative diagnosis, and not as useful for treatment planning when intervention is required. MRI has a sensitivity of 86-94% and a specificity of 88-92% in diagnosing acute colonic diverticulitis and is comparable in its ability to identify alternative diagnosis. MRI findings in acute diverticulitis are similar to CT, currently MRI is not used for abscess drainage. CT FINDINGS IN ACUTE DIVERTICULITIS a) Uncomplicated acute diverticulitis Page 7 of 29

8 The most common CT findings in acute uncomplicated diverticulitis are colonic wall thickening (>3 mm) and pericolic fat stranding, usually associated with the presence of an inflamed diverticulum in the center of the fat stranding (Fig. 6 on page 12). In the absence of pericolic fat stranding wall thickening from acute diverticulitis can be difficult to distinguish from muscular hypertrophy from diverticulosis (myochosis). The degree of fat involvement is variable, from minimal to severe (phlegmon). b) Perforated acute diverticulitis: the intraperitoneal route The CT findings in acute complicated diverticulitis are the presence of an abscess and contained or free extraluminal air. Other complications are bowel obstruction, liver abscess, fistula and inferior mesenteric vein thrombosis. Abscess: A fluid collection of >1 cm in diameter containing air or delineated by a hypervascularized rim located in the colonic wall (Fig. 7 on page 13) or in the pelvis close to the colon (Fig. 8 on page 14). Purulent peritonitis: An inflammation secondary to contamination of the peritoneal cavity by pus, usually the result of the rupture of a previous abscess and less frequently due to the rupture of an inflamed diverticulum (Fig. 9 on page 15). Fecaloid peritonitis: An inflammation secondary to contamination of the peritoneal cavity by faecal material due to a direct connection between the lumen of the colon and the peritoneal cavity secondary to perforated colonic diverticulum (Fig. 10 on page 16). c) Perforated acute diverticulitis: the extraperitoneal route Less frequently, perforated acute sigmoid diverticulitis follows a extraperitoneal route via the subperitoneal space of the sigmoid mesocolon or directly through the retroperitoneum. Remember that since the extraperitoneal tissues do not react as acutely and severely to bacterial contamination as the peritoneal cavity does, symptoms and clinical signs of extraperitoneal perforation of the gastrointestinal tract may be obscure, delayed, nonspecific, or misleading. Page 8 of 29

9 The sigmoid colon is an intraperitoneal structure suspended in the peritoneal cavity and attached to the pelvic wall by the sigmoid mesocolon. The sigmoid mesocolon is formed by two layers of peritoneum enclosing a considerable amount of fat allowing visualization of the vessels which course between this two layers. Therefor, in MDCT the anatomic landmarks of the sigmoid mesocolon are the vessels included in fat between their two layers, the superior hemorroidal vessels, the marginal vessels, the sigmoidal vessels and specially the inferior mesenteric vein and artery. Retroperitoneal perforation: Because the sigmoid colon lies below the inferior limit of the renal fascia there is an anatomic continuity with the anterior and posterior left pararenal spaces, and the gas may also extend medially over the psoas muscle in the form of mottled radiolucencies (Fig. 11 on page 17). Sigmoid mesocolon perforation: If the sigmoid perforation occurs between the peritoneal leaves of the sigmoid mesocolon the gas dissects the fat plane between both layers following the path of the inferior mesenteric vessels (Fig. 12 on page 18). If there is enough amount of gas the extraperitoneal gas rises bilaterally within the anterior pararenal spaces, and if the perforation is important the air can ascend upwards as far as the neck (Fig. 13 on page 19 and Fig. 14 on page 20). Extraperitoneal abscesses can be located between the two layers of the sigmoid mesocolon (Fig. 15 on page 21 and Fig. 16 on page 22). Fistula to pelvic organs: Fistula occur in 2,4-20% of cases complicating acute diverticulitis, 65% are colovesical and 20% colovaginal. CT of a colovesical fistula (Fig. 17 on page 23) characteristically demonstrates the triad of colonic diverticula, thickening of the colonic segment adjacent to the bladder and air in the bladder. If a colovesical fistula is suspected, it can be helpful for the diagnosis to use rectal contrast material without intravenous contrast material. And if positive contrast material is present within the bladder it must have originated from the colon and the diagnosis of a colovesical fistula is confirmed. Intestinovesical fistula as is the case with colovesical fistula should happen through two pathways: (1) transperitoneal secondary to abscess formation, adherent to the bladder and subsequent rupture into the bladder, (2) extraperitoneal due to extension of an inflammatory or suppurative intestinal process along the mesosigmoid and the ureter and the perforation at the base of the bladder. Page 9 of 29

10 Extrapelvic spread of disease: Diseases arising from the pelvic contents may first manifest themselves by signs and symptoms located remote from their site of origin (Fig. 18 on page 24 and Fig. 19 on page 25). Gastrointestinal tract perforations may dissect along anatomic planes of the pelvis to first present in the limb or retroperitoneum. The origin of the disease within the pelvis often remains clinically occult. The major mechanism of gas formation is the pressue gradient between the lumen of the gut and surrounding tissue, this pressure is transmitted to the contents of the intestinal tract and promotes their evacuation. The anatomic site of perforation determines the pathway of spread of the sinus tract to the subcutaneous tissue. Images for this section: Fig. 3: The Hinchey Classification is a radiologic classification for assessing the severity of perforated acute diverticultis based on CT findings. This classification doesn't include mild form or extraperitoneal involvement. Page 10 of 29

11 Fig. 4: The Buckley Classification of the severity of acute diverticulitis uses also CT scanning for staging the disease. In this classification all the forms of the disease from mild to severe are included. Page 11 of 29

12 Fig. 5: The Hansen and Stock Classification uses CT findings for staging diverticular disease including all the spectrum of the disease and not only acute diverticulitis. Page 12 of 29

13 Fig. 6: An inflamed diverticulum (white arrow) surrounded by fat stranding in a case of uncomplicated sigmoid diverticulitis. Page 13 of 29

14 Fig. 7: A small abscess located in the sigmoid colon wall (white arrow) in a case of perforated acute sigmoid diverticulitis. There is also thickening of the sigmoid wall and fat stranding in the pericolic fat (asterisk). Page 14 of 29

15 Fig. 8: Pelvic abscess with a characteristic air-fluid level (asterisk) close to the sigmoid colon in a case of perforated acute diverticulitis. Page 15 of 29

16 Fig. 9: Purulent peritonitis in a case of perforated acute diverticulitis of the sigmoid colon. Page 16 of 29

17 Fig. 10: A case of fecaloid peritonitis due to perforated acute diverticulitis of the sigmoid colon. Thickened sigmoid colon wall and inflamed sigmoid diverticulum (white arrow) in association with intense and diffuse inflammatory changes in the pelvis: fat stranding, dense free fluid and enhancement of the small bowel wall. Page 17 of 29

18 Fig. 11: Retroperitoneal gas distributed in the left anterior and posterior pararenal spaces and alongside the psoas muscle due to retroperitoneal perforation of acute sigmoid diverticulitis. Page 18 of 29

19 Fig. 12: Extraluminal air in the sigmoid mesocolon (asterisk) following the inferior mesenteric vessels secondary to perforated acute sigmoid diverticulitis. Page 19 of 29

20 Fig. 13: Extensive retropneumoperitoneum extending to the soft tissues of the chest and neck due to a perforated diverticulum of the sigmoid colon. The patient presented to the Emergency Room with subcutaneous emphysema of the neck without known source. Page 20 of 29

21 Fig. 14: Extensive retropneumoperitoneum extending to the soft tissues of the chest and neck due to a perforated diverticulum of the sigmoid colon. The patient presented to the Emergency Room with subcutaneous emphysema of the neck without known source. Page 21 of 29

22 Fig. 15: Abscess (asterisk) included in the sigmoid mesocolon due to acute diverticulitis perforation. Page 22 of 29

23 Fig. 16: A small fluid collection with an air-fluid level in the sigmoid mesocolon consistent with an abscess (asterisk). Page 23 of 29

24 Fig. 17: Small air-fluid level in the lumen of the bladder secondary to transperitoneal fistula (white arrow) between the bladder and the sigmoid colon due to acute diverticulitis. Page 24 of 29

25 Fig. 18: In this case the suspected diagnosis was deep venous thrombosis (DVT) of the right limb, an ultrasound exam excluded DVT and showed subcutaneous tissue edema and soft tissue gas more evident in the muscles of the thigh. An emergency MDCT scan without contrast was done to confirm the presence of soft tissue gas and to gain more information. The images show soft tissue gas in the muscles of the right buttock and the posterior compartment of the right thigh (asterisk) consistent with the diagnosis of necrotizing myositis. A fistula (white arrows) passes through the sciatic notch connecting the diseased right limb with the sigmoid colon, perforated acute diverticulitis of the sigmoid colon was considered as the most likely cause of the features and surgically confirmed, differential diagnosis with perforated sigmoid or upper rectal cancer was an alternative diagnosis. Page 25 of 29

26 Fig. 19: MPR of the same case described previously. In this case the suspected diagnosis was deep venous thrombosis (DVT) of the right limb, an ultrasound exam excluded DVT and showed subcutaneous tissue edema and soft tissue gas more evident in the muscles of the thigh. An emergency MDCT scan without contrast was done to confirm the presence of soft tissue gas and to gain more information. The images show soft tissue gas in the muscles of the right buttock and the posterior compartment of the right thigh Page 26 of 29

27 (asterisk) consistent with the diagnosis of necrotizing myositis. A fistula (white arrows) passes through the sciatic notch connecting the diseased right limb with the sigmoid colon, perforated acute diverticulitis of the sigmoid colon was considered as the most likely cause of the features and surgically confirmed, differential diagnosis with perforated sigmoid or upper rectal cancer was an alternative diagnosis. Page 27 of 29

28 Conclusion The intraperitoneal and extraperitoneal spreading of perforated sigmoid diverticulitis can be well depicted with MDCT due to its multiplanar capabilities and near isotropic resolution. MDCT can give the diagnosis in difficult cases of extraperitoneal spreading of diseases. Personal Information N. Bernal Garnés, E. Miralles Aznar, C. F. Munoz-Nunez, J. Carreres Polo, R. Mut Pons and S. Tigges. Servicio de Radiología Hospital de Torrevieja Carretera CV-95 s/n Torrevieja Alicante Spain mail References Ashizawa, T., Hama, K., Tanaka, H., & Ando, M. (2007). Intramesocolic diverticular perforation of the sigmoid colon diagnosed by detecting air collection in anterior pararenal space on computed tomography: Report of a case. Acta medica Okayama, 61(5), 299. Buckley, O., Geoghegan, T., O'Riordain, D. S., Lyburn, I. D., & Torreggiani, W. C. (2004). Computed tomography in the imaging of colonic diverticulitis. Clinical Radiology, 59(11), Lohrmann, C., Ghanem, N., Pache, G., Makowiec, F., Kotter, E., & Langer, M. (2005). CT in acute perforated sigmoid diverticulitis. European Journal of Radiology, 56, Page 28 of 29

29 Ludeman, L., Warren, B. F., & Shepherd, N. A. (2002). The pathology of diverticular disease. Best Practice & Research Clinical Gastroenterology, 16, Meyers, M. A., Charnsangavej, C., & Oliphant, M. (2010). Meyers' Dynamic Radiology of the Abdomen: Normal and Pathologic Anatomy. Springer. Morris, C. R., Harvey, I. M., Stebbings, W. S. L., Speakman, C. T. M., Kennedy, H. J., & Hart, A. R. (2002). Epidemiology of perforated colonic diverticular disease. Postgraduate Medical Journal, 78(925), Ritz, J.-P., Lehmann, K. S., Loddenkemper, C., Frericks, B., Buhr, H. J., & Holmer, C. (2010). Preoperative CT staging in sigmoid diverticulitisdoes it correlate with intraoperative and histological findings? Langenbeck's Archives of Surgery, 395, Sheth, A. A., Longo, W., & Floch, M. H. (2008). Diverticular disease and diverticulitis. The American Journal of Gastroenterology, 103(6), Page 29 of 29