Diverticular disease in CT colonography
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- Lefere, P., Gryspeerdt, S., Baekelandt, M. et al. Eur Radiol (2003) 13: L62. doi:10.1007/s00330-003-1973-x
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The aim of this study was to evaluate findings on CT colonography (CTC) in patients with diverticular disease. In a retrospective analysis of 160 consecutive patients, who underwent CTC and conventional colonoscopy (CC), patients with diverticular disease were retrieved. The CTC images were compared with CC and, if possible, with pathology. Findings on both 2D and 3D images are illustrated with emphasis on diagnostic problems and the possible solutions to overcome these problems. Several aspects of diverticulosis were detected: prediverticulosis (3%); global (55.6%); and focal wall thickening (4%) caused by thickened haustral folds, fibrosis, inflammation and adenocarcinoma; diverticula (52%); pseudopolypoid lesions caused by diverticular fecaliths (39%); inverted diverticula (1.2%); and mucosal prolapse (0.6%). Solutions to overcome pitfalls are described as abdominal windowing, content of the pseudopolypoid lesion, comparison of 2D and 3D images, prone–supine imaging and the aspect of the pericolic fat. In this series there were equivocal findings in case of mucosal prolapse (0.6%) and focal wall thickening (4%). Diverticulosis is a challenge for CTC to avoid false-positive diagnosis of polypoid and tumoral disease. Knowledge of possible false causes of polypoid disease and comparison of 2D and 3D images are necessary to avoid false-positive diagnosis. In case of equivocal findings additional conventional colonoscopy should be advised whenever a clinically significant lesion (≥1 cm) is suspected.
KeywordsCTColonColonographyColonic neoplasmsDiverticular disease
Computed tomography colonography (CTC) is emerging as a possible method for colorectal cancer screening [1, 2]. Diagnostic performance depending on the radiologist's experience  and diverticular disease being frequent, knowledge of its imaging features are important to avoid false-positive and false-negative findings. In this pictorial review it is our intention to illustrate imaging findings of CTC in patients with diverticular disease.
Diverticular disease is the most common colonic disease of the Western world affecting 10–30% of people at age 50 years and 30–60% at age 80 years. Of this population, 10–30% develop diverticulitis ; however, the disease is asymptomatic in the majority of patients . Together with ageing, longstanding low dietary fibre is the main predisposing factor for diverticular disease. Other aetiological factors have been mentioned: increased consumption of red meat, fat and salt. Some hereditary diseases, such as Marfan's syndrome and Ehler-Danlos syndrome, frequently require non-steroidal anti-inflammatory drugs. An increased incidence in immunosuppressed patients has also been reported. The influence of smoking, alcohol and caffeine remains controversial [6, 7].
Materials and methods
This study consisted of a review of 160 patients. All patients underwent both CTC and conventional colonoscopy (CC). There were 88 men and 72 women. Age varied between 36 and 90 years. The referral reasons were: a personal history of polypectomy or CRC; a familial history of CRC; patients aged over 50 years and patients with symptoms such as pain and change in stool habit.
For 75 patients, preparation consisted of ingesting polyethylene glycol (Colopeg, Roche, Gaillard, France), bisacodyl (Dulcolax, Boehringer Ingelheim, Paris, France) and observing a low-residue diet the day before CTC. For 85 patients, preparation consisted of fecal tagging with barium. For this, they were prepared with bisacodyl (Dulcolax), magnesium citrate, a dedicated low-residue diet and barium as sole fecal tagging agent (Loso Prep, Nutra Prep and Tagitol, respectively; E-Z-EM, Westbury, N.Y.).
After smooth muscle relaxation with buthylscopolamine (Buscopan, Boehringer Ingelheim, Paris, France), the colon was inflated with room air until patient tolerance. Dual scanning (supine and prone positioning) was performed with a single-slice helical CT scan (Tomoscan AV/EU, Philips, Best, The Netherlands) using a 5-mm collimation, a table increment of 7 mm/s and a reconstruction index of 3 mm as scanning parameters. The images were analysed on a workstation (Easy Vision, Philips, The Netherlands). Both two- and three-dimensional images were reviewed by two radiologists.
Conventional colonoscopy was performed on the same day.
Manifestations of diverticular disease
Unequivocal and equivocal findings in diverticular disease. NA not applicable (not detected in this series)
Discrete, regular wall thickening
Minimal luminal distortion
Dark circumferential ring in the colonic wall
Hyperdense ring with hypodense centre
Global wall thickening
Wall thickening >4 mm. Long segment. Saw tooth–zig zag
More pronounced luminal distortion
Intraluminal lesion with fat or air inclusion
2D imaging & 3D imaging
Diverticulum filled with thrombus
Inverted diverticulum without fat or air inclusion
Polypoid mucosal prolapse syndrome
Focal wall thickening
See Table 2
Differential diagnosis and criteria of focal thickening of the colonic wall. These imaging findings are equivocal and only suggest diagnosis. Again, whenever the suspected lesion is ≥1 cm conventional colonoscopy is advised
Focal thickening of the colonic wall
Shoulder formation/apple core
Long: >10 cm
Short: <5 mm
Mild thickness: 4–5 mm
Excessive thickness: >2 cm
Fluid at root of mesenterya
Pericolonic lymph nodes
Global wall thickening
With advancing disease myochosis becomes more prominent, resulting in calibre and haustral abnormalities. This results in a reduced colonic distention. Although some authors have experienced improved colonic distention only by dual positioning and not by intravenous glucagon , we preferred to use smooth muscle relaxation to reduce patient discomfort and to avoid possible spasm, as has been suggested by other authors .
Imaging findings are unequivocal. The hypertrophy of the circular muscle causes a global and regular wall thickening >4 mm of a long colonic segment with prominent semicircular folds and shortened interhaustral segments. This causes the haustral segments to indent on each other: concertina or zig-zag appearance; and saw-tooth phenomenon [4, 6]. The shortening of the interhaustral segments reduces the conspicuity of polypoid lesions. The 3D imaging shows more prominent luminal narrowing and distortion. The thickening of the semicircular folds sometimes mimics a tumoral lesion.
The diverticular fecalith
Polyp-simulating mucosal prolapse syndrome
Focal wall thickening
True polypoid lesion
As diverticular disease is common, a lot of patients present with the disease when screening for colorectal cancer; hence, knowledge of its imaging characteristics is important. Imaging findings are possibly equivocal in case of: (a) an impacted diverticulum with soft tissue attenuation; (b) an aspecific inverted diverticulum; (c) a polyp-simulating mucosal prolapse syndrome; and (d) an aspecific focal wall thickening. Although these findings are rare in an asymptomatic screening population, radiologists should be concerned when confronted with these images. They should urge him to prescribe CC whenever the suspected lesion is ≥1 cm (i.e. advanced adenoma), recently considered as the clinically significant polyp especially in a screening program for colorectal cancer [32, 33]. In these cases CTC will provide the gastroenterologists with the exact location of the suspected lesion. Finally, radiologists must be aware that examining a diverticular segment requires special attention because of the decreased visibility caused by a reduced luminal distention and muscular hypertrophy.