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CT Enteroclysis

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CT Enteroclysis

  1. 1. CT Enteroclysis OSR Dr. Yash Kumar Achantani
  2. 2. Introduction • There was a time when small-bowel follow-through (SBFT) was the only and primary method of diagnosing diseases of the small bowel. • Endoscopic methods for evaluating the small bowel, including ileocolonoscopy, capsule endoscopy, and double- balloon enteroscopy, offer distinct advantages for assessing superficial mucosal abnormalities and obtaining biopsies for histologic assessment. • However, endoscopic evaluation is invasive and may be limited by bowel strictures, and techniques such as double-balloon enteroscopy and wireless capsule endoscopy require special equipment and expertise that are available only at large tertiary-care centers. Moreover, no endoscopic technique allows assessment of extraenteric abnormalities.
  3. 3. • In recent years, there has been renewed interest in small bowel imaging using a variety of techniques such as ultrasound(US), contrast enhanced ultrasound (CEUS), computed tomography (CT), magnetic resonance imaging (MRI), computed tomography enteroclysis/enterography (CTEc/CTEg) and magnetic resonance enteroclysis/enterography ( MREc/MREg) and the small bowel endoscopic methods. • CT and MR enterography have proven superior to conventional barium examinations since they provide essential information about transmural and extramural involvements, and about the complications that may determine surgical treatment (obstruction, fistulas, abscesses).
  4. 4. CT Enterography • CT enterography was first introduced by Raptopoulos et al in 1997 as a modification to ‘‘standard’’ abdomino-pelvic CT examination to specifically examine the small bowel in detail, notably to assess the extent and severity of Crohn’s disease. • They combined neutral (low-density) oral contrast with ‘‘enteric phase’’ CT to optimise contrast resolution between mucosa and lumen, thereby maximising conspicuity of abnormalities arising from the small bowel wall.
  5. 5. • Several authors have subsequently described similar techniques, which are broadly categorised into: – CT enterography (where patients drink oral contrast) and – CT enteroclysis (luminal contrast is introduced via a nasojejunal tube placed fluoroscopically prior to CT examination). • Although superior jejunal distension is attained using enteroclysis, the convenience, efficiency and superior patient experience achieved with CT enterography make it the preferred technique at many institutions.
  6. 6. The CT-enteroclysis is a moderately reproducible examination because small-bowel distension is the major difficulty. It depends on the probe position, which is not always optimal, intestinal peristalsis, and reabsorption of the opacifying contrast agent. Furthermore, it is an irradiating exam that is uncomfortable for the patient. For this reason, many teams perform CT-enteroclysis without a probe, which requires slow and progressive ingestion of the contrast agent, providing less complete distension, probably limiting the detection of small tumors.
  7. 7. Indications CT enteroclysis is complementary to capsule endoscopy in the elective investigation of small-bowel disease, with a specific role in the investigation of Crohn disease, small-bowel obstruction , and unexplained gastrointestinal bleeding. CT enteroclysis is considered significantly superior to conventional enteroclysis in depicting Crohn disease associated intra- and extra- mural abnormalities .
  8. 8. Patient preparation The patient should not have eaten solid food for 8 h. Water should be authorized so as to reduce the phenomenon of water resorption by the small intestine during intestinal infusion, which increases with dehydration.
  9. 9. Premedication • Metoclopramide (10 mg) – given orally 75 minutes before the CT scan – stimulates gastric emptying. • Glucagon (1 mg) OR Buscopan (20mg) – administered intravenously immediately prior to scanning – decrease small bowel peristalsis.
  10. 10. • The technique of CT enterography combines – small bowel distension with a neutral or low-density oral contrast mixture and – abdomino-pelvic CT examination during the enteric phase following administration of intravenous contrast. • Patients drink approximately 1.5–2 l of oral contrast over 45–60 min. • Patient compliance is central to the success of CT enterography, and supervision and encouragement during the drinking phase is recommended. • Optimising luminal distension will facilitate rapid and efficient luminal navigation, enabling accurate detection and characterisation of abnormalities. Technique
  11. 11. In CT enteroclysis an enteroclysis catheter is used. It is a 13-F catheter with a 150 cm long, with 2.8-mm external diameter and 2.1-mm internal diameter and a distal balloon that prevents gastroduodenal reflux. The balloon is inflated with 20– 25 ml of air and fixed in Treitz’s angle. The catheter is placed with fluoroscopic guidance. Patients tolerate nasal passage in a seated position better than oral passage because the gag reflex is avoided.
  12. 12. Luminal contrast and distension • Neutral or low-density oral contrast media are a prerequisite for good-quality CT enterography because: – they maximise contrast between the lumen and enhancing small bowel wall, – facilitating assessment of mucosal thickening and wall stratification/enhancement patterns
  13. 13. Oral Contrast Agents • Water • Water–methylcellulose solution • polyethylene glycol, • commercially available low-density barium, • 0.1% Volumen (Bracco, Milan, Italy) and • Milk • Positive oral contrast agents
  14. 14. • Water – inexpensive, well tolerated by patients, and effective for distending the stomach, duodenum, and jejunum. – inadequate distension due to rapid reabsorption. • polyethylene glycol (PEG) electrolyte solution – Gastrointestinal side-effects. • Volumen; • 0.1% w/v ultra-low-dose barium with • sorbitol, a nonabsorbable sugar alcohol – promotes luminal distention and – limits resorption of water across the length of the small bowel. – The attenuation of low-concentration barium is only 20 HU. – Fewer side effects than are associated with PEG. – Unpleasant taste & loose bowel movements or diarrhea very soon after the scan
  15. 15. • Positive oral contrast agents (containing iodine or barium) – not routinely used for CT enterography – they obscure mucosal enhancement, intraluminal haemorrhage and assessment of subtle mural disease. – problematic in creating three-dimensional images if CT angiography is concurrently being performed—for example, in the assessment of gastrointestinal blood loss. • May be preferred for some clinical situations – establish fistula patency – exact site of mechanical obstruction – known serosal disease, – detection of some primary tumors, and – patients with an iodine allergy.
  16. 16. Optimal Volume A volume of less than 1.5L is unlikely to be sufficient to adequately distend the small bowel without active inflammation, and a subcentimetre mass could be missed; although,according to many authors, good-quality examinations can be achieved with smaller volumes. In enteroclysis Intestinal filling takes place with an electrical pump which provides homogenous and good-quality opacification, a high and constant flow rate, and excellent safety because pressure and flow rate can be monitored and regulated permanently. The flow rate chosen should be from 180 to 200 mL/min, with 2 L of contrast agent.
  17. 17. In enterography • For the evaluation of the upper small intestine only, – patients drink a total of two 450-mL bottles of the agent, with a 10- minute interval between each bottle. – Water achieves the same results, is less expensive, and is better tolerated by patients. • For the evaluation of the complete small intestine,. – Patients are given three 450-mL bottles, each of which is consumed at about 15-minute intervals. The last 150 to 200 mL is consumed just before the patient gets on the scanner. • In small patients and patients with history of previous small bowel resection – smaller volumes of oral contrast may be sufficient, judged mainly by patient tolerance.
  18. 18. Intravenous Contrast • In addition, intravenous contrast is an essential component of CT enteroclysis. • It enables evaluation of: – wall thickening, – mucosal enhancement, – the supplying and draining blood vessels, and – the presence or absence of GI bleeding. • 100 to 125 mL of intravenous contrast at a rate of 3 to 5 mL/sec, initiating the scan acquisition after a 60-second delay.
  19. 19. • Maximal small bowel enhancement on MDCT has been reported by Schindera et al to be 50 s after administration of intravenous contrast or 14 s after aortic peak enhancement. • Therefore administer contrast intravenously during this enteric phase. • The enteric phase is similar to the pancreatic phase; therefore, CT enterography also optimises demonstration of most pancreatic neoplasms. • This is particularly relevant for clinicians, given that symptoms of pancreatic tumour can mimic luminal disease. • However, lack of portal venous phase imaging is rarely a problem for patients undergoing CTE because subtle liver metastases are rarely the target of imaging in this patient group.
  20. 20. Alternatively… • Acquisition of both arterial and venous phase images at 30s and 60s respectively. • The arterial phase images are critical for: – appreciating bowel wall for mucosal hyperenhacement – engorgement of the adjacent vasa recta, all of which are important signs of bowel inflammation. • The venous phase images are important not only for – evaluating the bowel, but also the – other parenchymal organs of the abdomen (i.e., liver, spleen, etc.), – the extraenteric manifestations of Crohn’s disease, – the venous mesenteric vasculature, and – hypovascular bowel tumors.
  21. 21. CT acquisition CT acquisition with no injection of iodated contrast medium should be done after intestinal filling, unless perfusion has failed, in order to check the catheter position when monitoring irradiation. Images are acquired with thin collimation, with acquisition of 0.625- 0.75 mm slices, which are then reconstructed into 3-5 mm axial slices for routine interpretation. Coronal and sagittal multiplanar reconstructions are directly created at the CT scanner following the acquisition of the axial source images. At the same time, isotropic 0.5-0.75 mm images are used for 3-D post- processing.
  22. 22. 3-D TECHNIQUE • Two separate sets of 3-D reconstructions: – Maximum intensity projection (MIP) imaging • Effective for evaluation of the mesenteric vasculature • Not only the main aortic branch vessels, but also tiny mesenteric branches which are typically not readily visualized on the axial source images. • Areas of bowel hyperemia and mesenteric vascular engorgement (i.e., “comb sign”, opacification of the vasa recta) are also easily identified using this technique; – Volume rendering (VR) • most useful in displaying the entirety of the small bowel, and illustrating the relationship of adjacent small bowel loops, subtle areas of bowel wall thickening, abnormal mucosal enhancement, and extra-enteric manifestations of Crohn’s disease
  23. 23. Precautions • To avoid intravenous contrast-induced nephropathy, – limit the use in frail and diabetic patients. – consider reducing the volume of intravenous contrast, – ensure patients are well hydrated before the examination and – monitor renal function closely afterwards. • A large volume of oral contrast is contraindicated – who are fluid-restricted owing to clinical conditions such as renal or heart failure. • Following CT enterography examination, patients are encouraged to remain in the radiology department for approximately 45 min because they reasonably frequently experience severe, or short- lived, diarrhoea.
  24. 24. Variations to the basic protocol - Multiphase Scan • In patients where active gastrointestinal bleeding is suspected (and endoscopic work-up is negative) a multiphase scan protocol can be used to identify sites of occult gastrointestinal bleeding. • This protocol would frequently include pre-contrast, arterial, venous and delayed phase CT examinations of the abdomen and pelvis. • Rarely, this can be used in emergency situations to identify the site of bleeding. • However, the radiation burden is approximately three times higher, and therefore potential radiation risks should be balanced against patient benefit.
  25. 25. LOW-DOSE CT TECHNIQUE • peak incidence of Crohn’s disease is in patients between the ages of 20-40 years; • a sizeable percentage of cases are diagnosed in children (15%); and • the disease has a mild female predominance i.e. radiation sensitive population,
  26. 26. Dose-reduction Techniques • These include – Automated tube current modulation, which alters the tube current (mAs) based on the patient’s size and density; – Automated tube potential modulation, which alters the scanner’s tube potential (kVp) based on the patient’s size and density; and – Iterative reconstruction, an alternative to traditional filtered back projection reconstruction techniques, which allows the acquisition and reconstruction of diagnostic quality images at far lower radiation doses
  27. 27. Normal results In general, CT-enteroclysis also extends the duodenum by reflux and, with good distension, the normal wall measures approximately 1 mm. The different normal layers of this wall are not visible. This wall hosts a great number of folds. The duodenal papillae and mucous anomalies are not visualized by CT-enteroclysis. The small bowel wall’s normal thickness varies greatly depending on the distension. The wall is sometimes barely visible or less than 1 or 2 mm if distension is substantial. It appears thicker (3-4 mm) when the intestine is flat or only slightly distended.
  28. 28. Axial and Coronal images of normal CT- enteroclysis, with optimal and homogenous intestinal distension. Filling was done with a mannitol-based solution.
  29. 29. False-positive results The false-positive results generally correspond to partial volume effects of the valvulae conniventes, intestinal spasms, and functional invaginations. It seems that invagination is very difficult to demonstrate because its analysis is highly subjective and there is no reference method to prove it. It can be confused with simple intestinal contraction or an intestinal fold , but not with organic invagination because it does not result in upstream distension. It is therefore indispensable to take multiplanar reformations to limit this pitfall.
  30. 30. Example of a false-positive result: a. Pseudothickening of the bowel wall at the left flank (arrow), b. Actually corresponding to an intestinal- jejunal fold when the loop is uncoiled with multiplanar reformations (arrow).
  31. 31. Example of a false-positive result: Pseudotarget of a loop at the left flank (arrow) corresponding to a jejunal valvulae conniventes.
  32. 32. Example of a false-positive result. a Example of functional jejunal invagination or intestinal spasm appearing as a stenosing wall thickening after injection of iodinated contrast product. b Analysis of the other acquisition phases can eliminate the nonpathological aspect of this image because it disappears.
  33. 33. Example of false-positive result for a tumor (arrow): a axial view, b oblique view.
  34. 34. Chronic intestinal bleeding The performance of CT-enteroclysis in diagnosing obscure intestinal bleeding is poor because in this indication, the most frequently found lesions in decreasing order of frequency are : i. Arteriovenous malformations (or angiodysplasia) , very frequent after 50 years of age, ii. Ulcerations secondary to NSAIDs, iii. Tumors. There is no precise consensus on the best diagnostic strategy in these situations of obscure chronic intestinal bleeding. However, age plays an important role in the diagnostic decision.
  35. 35. Chronic intestinal bleeding and tumors after 50 years of age It is recommended to begin with an esogastroduodenoscopy and a colonoscopy, then if these exams are negative, a videocapsule recording is indicated. After the age of 50, CT-enteroclysis has a very minor place since angiodysplasia is frequently the cause of bleeding and this is not detected on CT. However, CT-enteroclysis is often done before videocapsule endoscopy because it can verify the absence of stenosis that may block the capsule.
  36. 36. Chronic intestinal bleeding and tumors before 50 years of age CT-enteroclysis comes after gastroscopy and colonoscopy because a bowel tumor must be sought first and foremost, with angiodysplasia less frequent at this age. The best indications come from carcinoid syndromes and digestive tract hemorrhage syndromes recurring over several months with negative gastroscopy and colonoscopy. CT-enteroclysis is a technique that can detect tumors less than 1 cm in size.
  37. 37. Acute digestive tract bleeding In an emergency situation, videocapsule endoscopy has no place because it lasts 8 h and its progression depends on peristalsis. In addition, if the patient is in hemorrhagic shock this exam is not indicated. Therefore, CT enteroclysis and/or the double-balloon enteroscope are indicated. On the contrary, when the patient is doing well, videocapsule endoscopy can easily be performed.
  38. 38. Small-bowel Tumors CT enteroclysis seems to be an indisputable, high-performance technique in detecting small-bowel tumors as long as optimal intestinal distension is obtained. In staging tumors, small-bowel tumors present a diagnostic difficulty for both the clinician and the radiologist because they are rare (<5% of tumors of the digestive tract), their nonspecific symptoms delay diagnosis, and in particular their small size at the initial evolving stage. CT enteroclysis can differentiate between epithelial and conjunctive tumors.
  39. 39. Epithelial tumors are represented by Adenocarcinomas Adenomatous polyps Solitary fibrous polyps Benign tumors comprise Nonmalignant GISTs, Leiomyomas, Lipomas Hemangiomas, Benign lymphoid hyperplasias, Schwannomas
  40. 40. Malignant tumors concern the GISTs with malignancy criteria Leiomyosarcomas, Hemangiosarcomas Kaposi sarcomas Type B or T lymphomas are born of lymphoid tissue. Carcinoid tumors are neuroendocrine tumors. Metastases appear either from intrinsic involvement (peritoneal carcinomatosis) or hematogenic involvement .
  41. 41.  Most frequent malignant tumors are stromal tumors (GISTs), adenocarcinomas and lymphomas.  Lipomas are the most frequent benign tumors.  Hypervascular lesions generally correspond to carcinoid tumors, stromal tumors, or certain metastases.  The adenocarcinomas enhance less intensely and are often stenosing. Lymphomas, on the other hand, enhance very little and are associated with multiple adenopathies.  Lipomas are very easy to identify on CT because of their characteristic hypodensity.
  42. 42. Circumferential thickening of the jejunum with aneurysmal dilatation and low enhancement after injection and therefore highly suggestive of lymphoma. The double-balloon enteroscope and the pathological report nevertheless diagnosed mucinous adenocarcinoma.
  43. 43. CT and endoscopic aspect (videocapsule) of an adenocarcinoma of the jejunum appearing as budding and circumferential thickening.
  44. 44. Peutz-Jeghers syndrome. CT-enteroclysis demonstrated several ileal polyps (arrows).
  45. 45. Example of a single fibrous polyp on CT-enteroclysis and endoscopic videocapsule.
  46. 46. Lipoma of the distal jejunum diagnosed on videocapsule endoscopy and double- balloon endoscope in a digestive tract duplication (arrows).
  47. 47. Ileal stromal tumor revealed by abdominal pain. The tumor’s characteristics are seen clearly: a Budding endoluminal mass, b Hypervascular heterogeneous mass with large feeding artery, c A few necrotic areas and intralesional calcification.
  48. 48. Voluminous ileal stromal tumor on CT- enteroclysis: budding endoluminal mass, hypervascular heterogeneous mass with large feeding artery.
  49. 49. Type B ileal lymphoma seen as a homogenous thickening of the wall with regular contours and little enhancement, confirmed by surgery.
  50. 50. Ileal endoluminal carcinoid tumor (arrows) corresponding to stenosing hypervascular wall thickening. Videocapsule endoscopy found an oval submucous ileal nodule.
  51. 51. Rectal adenocarcinoma metastasized to the jejunum (arrows): spiculated tumor, slightly vascularized.
  52. 52. CT enteroclysis showing a strongly enhanced poorly outlined tumour located in the lumen of the jejunum with Metastasis to the lymph node (small arrow) and Metastases to the liver (arrows).
  53. 53. Ileal metastasis of melanoma (arrows).
  54. 54. Inflammatory disease The most frequent inflammatory involvement of the small bowel is Crohn disease: chronic ulcerous and stenosing granulomatous progression in the young adult most often found in the terminal ileum. CT is a reference technique to study wall thickening, abdominal fat, and the complications of inflammatory disease of the small bowel with a strong impact on patient management.
  55. 55. Skip lesions in Crohn disease. Axial CTE section depicts two inflammatory small bowel strictures (arrows) separated by a segment of normal distended small bowel (arrowheads), characteristic findings of Crohn disease.
  56. 56. Manifestations of active Crohn disease. (2a) Axial CTE section shows mucosal hyperenhancement (black arrow) and mural stratification (white arrow) of the terminal ileum, an appearance that contrasts markedly with that of nondiseased ileal segments (*). (2b) Axial CTE section from another patient shows mesenteric hypervascularity (arrowheads) adjacent to the involved bowel segment.
  57. 57. Fistula formation in Crohn disease. Coronal volume-rendered CTE sections obtained in two patients depict ileo-ileal fistulas (arrowheads in a) and an ileocolonic fistula (arrow in b).
  58. 58. Coronal volume-rendered CTE sections from two patients (a and b) demonstrate prominence of the vasa recta, or “comb sign” (arrows).
  59. 59. Crohn disease complicated with terminal ileitis: Submucous edema and mucous uptake of contrast medium responsible for the target aspect.
  60. 60. Diverticular disease On CT, diverticulum generally corresponds to an extraluminal image, rounded, with a fluid, gas, or fluid-gas content, communicating with the intestinal lumen. On CT-enteroclysis, diverticula more often appear as fluid since they fill simultaneously with the intestinal loops. Congenital diverticula are more frequently found on the antimesenteric edge than acquired diverticula found on the mesenteric edge where the vessel penetrates .
  61. 61. Duodenojejunal diverticulosis a axial view, b coronal view.
  62. 62. Meckel diverticulum Meckel diverticulum is inconstant and rare since it is found in only 2% of autopsies. It is most often asymptomatic and is manifested by its hemorrhagic, inflammatory, occlusive, and tumoral complications. In CT-enteroclysis abundant filling of the small intestine loops by enteroclysis theoretically easily distinguishes between diverticulum and intestinal loop.
  63. 63. Merckels diverticulum seen by by multiplanar reformations, Confirmed by surgery
  64. 64. Small-bowel occlusion In cases of low-grade occlusion, the ingestion of contrast product or its injection in the nasogastric catheter before the CT examination makes it possible to differentiate incomplete occlusions that can be treated medically from complete surgical occlusions. However this examination must be done with a double-function catheter (infusion and aspiration) to avoid any problems. However, this practice is debatable since it increases endoluminal pressure in a static intestine with possible microbial proliferation and a consequential risk of septic discharge.
  65. 65. The Future • CT enterography will continue to be incorporated into wider clinical measures of Crohn’s disease, particularly given the promise that objective CT findings such as mural hyperenhancement can be quantitated. • Continuing technical developments in CT image reconstruction will substantially reduce the radiation dose at CT enterography, which is already the same or less than routine abdominal CT.
  66. 66. • The use of dual-source CT systems will permit wider use of low-energy CT scanning, which will – increase the conspicuity of hypervascular inflammation and – permit further radiation dose reduction. Thickening of ascending colon (arrow) Seen with A. Normal CT enterography technique. B. With 140 kV tube C. With 80 kV tube
  67. 67. Low-Dose 18F-FDG PET/CT Enterography • Low-dose 18F-FDG PET/CTE, compared with CTE, may improve the detection and grading of active inflammation in patients with Crohn disease. CTE demonstrates mural thickening and mucosal enhancement in loop of ileum (arrow) involved with Crohn disease. Corresponding 18F-FDG uptake is seen on PET. Excellent anatomic registration of PET and CTE findings on PET/CTE
  68. 68. PET/CTE also may reveal clinically significant findings, such as enterocolic fistula, not evident on PET or CTE alone. Axial CTE image (A) demonstrates thickened loop of ileum (white arrow) in pelvis and unremarkable adjacent loop of sigmoid colon (black arrow). No fistula was appreciated on CTE. Corresponding 18F-FDG PET image (B) reveals increased tracer uptake in ileum (arrow) consistent with active Crohn disease; however, anatomic detail is insufficient to suggest enterocolic fistula. Fused PET/CTE image (C) clearly demonstrates 18F-FDG uptake (arrow) bridging ileum and sigmoid colon, with focal uptake present in wall of sigmoid colon. PET/CTE diagnosis of enterocolic fistula was confirmed at surgery.

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