Journal of Medical Society

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 34  |  Issue : 2  |  Page : 69--75

Role of multidetector computed tomography enterography in the evaluation of small bowel diseases


Shweta Bhalothia, Veeraraghavan Gunasekaran, Shoibam Subhaschandra Singh 
 Department of Radiodiagnosis, Regional Institute of Medical Sciences, Imphal, Manipur, India

Correspondence Address:
Veeraraghavan Gunasekaran
Department of Radiodiagnosis, Regional Institute of Medical Sciences, Imphal, Manipur
India

Abstract

Background: Small bowel imaging is technically challenging due to the difficulty in displaying the long and serpentine small bowel in entirety and intrinsic motion peristalsis and positional changes caused by breathing. Multidetector computed tomography (MDCT) enterography with the use of neutral enteric contrast permits an excellent assessment of the small bowel pathologies. Objective: The objective of this study is to determine the radiological features of small bowel diseases with respect to the presence, localization, causes, and associated complications with MDCT enterography. Materials and Methods: This is a single-center, cross-sectional, analytical study, which was carried over a period of 2 years on 43 patients, in a medical institute at department of radiodiagnosis. The study was conducted with Philips Brilliance 64-Slice computed tomography machine with neutral enteric contrast and intravenous contrast agents with arterial and enteric or portal phases. Imaging findings were correlated clinically, surgically, and histopathologically. Results: Out of the 43 cases, nine cases (20.93%) were of malignant pathologies, 20 cases were of nonmalignant mural pathologies (46.51%), and 14 cases were other intraluminal or extraluminal pathologies. The common bowel wall patterns found in nonneoplastic pathologies were segmental (50%), symmetrical (70%), mild-to-moderate wall thickening (70%), homogeneous and stratified attenuation patterns (95%), whereas segmental (80%), asymmetrical (80%), marked wall thickening (100%), and heterogeneous enhancement patterns (60%) with distal bowel involvement in primary malignancy cases. Mean wall thickness in malignant pathologies (21.56 ± 15.68 mm) was statistically significantly higher than mean wall thickness of nonmalignant pathologies (7.85 ± 3.69 mm) with P value of 0.031 (<0.05). Conclusion: MDCT enterography is a powerful diagnostic tool for the study of small bowel disorders, including inflammatory disease, small bowel neoplasms, and mechanical obstruction.



How to cite this article:
Bhalothia S, Gunasekaran V, Singh SS. Role of multidetector computed tomography enterography in the evaluation of small bowel diseases.J Med Soc 2020;34:69-75


How to cite this URL:
Bhalothia S, Gunasekaran V, Singh SS. Role of multidetector computed tomography enterography in the evaluation of small bowel diseases. J Med Soc [serial online] 2020 [cited 2021 Feb 28 ];34:69-75
Available from: https://www.jmedsoc.org/text.asp?2020/34/2/69/307885


Full Text



 Introduction



Imaging of the small bowel is challenging technically, because the organ is long and serpentine, a large field of view and a large volume are needed to display in entirety. Another problem for imaging is motion, both intrinsic motion of peristalsis and the positional changes caused by breathing. Ever most of the common diseases in the small bowel, early changes are subtle making their diagnosis difficult.[1],[2],[3] Small bowel follow through and enteroclysis are widely used for small bowel imaging; however, these examinations provide only indirect information about the bowel wall and prone to problems caused by overlapping bowel loops.[4] Computed tomography (CT) enteroclysis is an invasive technique, requires intubation of jejunum for administration of enteric contrast material and patient needs to be sedated, leading to increased cost and acquisition time as well as reduced availability in comparison with CT enterography. Enteroscopy shows promise for the study of the small bowel, but this technique is invasive and cannot explore the totality of the small bowel.[5] CT enterography, which was first introduced by Raptopoulos et al. in 1997,[6] allows the evaluation of each intestinal segment without loop superimposition. Also provides data on the parietal involvement and allow the evaluation of the surrounding mesentery, perienteric fat and other abdominal structures.[7] The oral contrast agents used for CT enterography can be categorized into two groups: Positive contrast agents and neutral contrast agents. A potential limitation of positive oral contrast agents in the evaluation of the small bowel is that mucosal enhancement may be obscured by the luminal contrast material, and thus the pattern of enhancement, which serves as a primary aid in the differential diagnosis of an abnormal small bowel segment, may be impaired.[8] Additionally interfere with the postprocessing techniques and hinder visualization of the mesenteric vessels. Today, neutral oral contrast agents are routinely used for CT enterography. Their low attenuation allows excellent visualization of the bowel wall and its lumen.[2] Neutral contrast refers to agents that have an attenuation value similar to that of water (0–30 HU).[8] Multiple low-attenuation neutral contrast agents have been studied in the literature namely: Water, water with methylcellulose, 0.1% barium solution with sorbitol (VoLumen), polyethylene glycol (2%) solution and milk (4%),[9] iso-osmotic mannitol,[10] lactose solution mixture of sorbitol and carboxy-methyl-cellulose. CT enterography is not only used for investigating proved or suspected inflammatory bowel disease like tuberculosis (TB), Crohn's disease, typhoid enteritis but also for detecting occult gastrointestinal tract bleeding, small bowel neoplasms, celiac sprue, mesenteric ischemia, malrotation, postoperative adhesions, diverticular disease, duodenal diverticulum, cystic lesion, mechanical obstruction, internal hernia, polyposis etc.

The purpose of this study is to assess the feasibility and usefulness of multiphase multidetector CT (MDCT) enterography using iso-osmotic mannitol as an orally administered neutral contrast agent in the evaluation of various small intestinal diseases.

 Materials and Methods



This is a cross-sectional analytical study, which was carried over a period of 2 years from October 2014 to September 2016 on 43 patients (22 male and 21 female patients), in a medical institute at department of radiodiagnosis in collaboration with department of surgery. The study was commenced only after the approval from the Research Ethics Board of this institute. Informed consents were obtained from all the patients.

A detailed history was taken and laboratory parameters, previous imaging findings were analyzed. Patients were requested to take soft diet 24 h before the examination and completely abstain from all food and drink for 4 h before scanning. A prokinetic agent 10 mg metoclopromide was given intravenously followed by per oral administration of 1500 mL of 5% w/v mannitol: 400 mL during first 20 min (60–40 min before scanning), 400 mL during second 20 min (40–20 min before scanning), 400 mL during the third 20 min (20–0 min before scanning), and 300 mL on CT table. A smooth muscle relaxant, hyoscine butylbromide (20 mg/mL) was administered intravenously immediately prior to scanning.

All the patients were imaged with PHILIPS BRILLIANCE 64-SLICE CT Machine. Helical MDCT scan starting from lung bases to pubic symphysis was done for every patient with single breath hold. The following scanning parameters were used: Tube voltage 120 kVp, tube current-time 250 mAs/slice, collimation 64 × 0.625, pitch 0.64, rotation time 0.5 sec, FOV 350 mm, and acquisition slice thickness of 5 mm without oral or intravenous contrast. A low-osmolar, nonionic contrast media, Iohexol (300 mg/mL) was given intravenously at a rate of 3–4 mL/sec, at a dose of 1–1.5 mL/kg body weight with an auto injector. Scanning was performed using bolus tracking technique during the arterial phase with enteric/portal phase acquired 20 s after the arterial phase.

Thin section images with reconstructed multi planar reconstruction and maximum intensity projection images and volumetric reconstruction were stored in the Extended Brilliance Workstation and/or in digital versatile disks and were interpreted at the end of case collection. Abnormal small bowel on contrast-enhanced MDCT was evaluated in terms of pattern of enhancement, length of involvement, degree of thickening, symmetry, and location along the bowel, submucosal or serosal involvement, and associated abnormalities of mesentery and lymph nodes.

Imaging findings were correlated clinically, surgically, and histopathologically wherever possible.

Summarization and analysis were carried out using descriptive statistics such as percentages, means, and standard deviation with the help of IBM SPSS version 21 for Windows (1BM Corporation, Armonk, New York, USA) for Windows. P < 0.05 was considered statistically significant.

 Results



Maximum number of cases was found in the fifth and sixth decades. The mean age in cases of malignant small bowel diseases (58.7 ± 17.1 years) was relatively higher than nonmalignant cases (47.9 ± 18.2 years). Peak incidences of malignant pathologies were found in the sixth, seventh, and eighth decades accounting for 88.8% cases. Single case of ileocecal non-Hodgkin lymphoma was detected in a 17-year-old human immunodeficiency virus positive patient [Figure 1]. Maximum incidences of nonmalignant pathologies noted in the fifth decade of life (32.35%) with 79.5% cases were below 60 years of age. Proportion of male (51.16%) and female cases was nearly equal with a male-to-female ratio of 1.04:1.{Figure 1}

The mural pathologies were divided into two major groups: malignant and nonmalignant pathologies. Of the 43 cases of small bowel diseases, nine (5 primary and 4 secondary malignant pathologies) cases comprising approximately 20.93% were of malignant pathologies and 20 cases were of nonmalignant mural pathologies constituting 46.51% of the total cases. Most commonly encountered small bowel diseases were inflammatory pathologies (41.86%). Overall, intestinal TB was the most common etiology among the study population constituting 27.90% of the cases (n = 12). Primary malignancies included adenocarcinoma of the duodenum and ileum (n = 3) constituting 6.9% of total cases and jejunal and ileal lymphomas (n = 2, 4.65% of total cases). Secondary malignancies included secondary serosal deposits in peritoneal carcinomatosis (n = 3) and direct involvement of the first part of the duodenum by carcinoma gall bladder (n = 1). Other less common pathologies predominantly involving the small bowel wall were enteritis (n = 4), ischemia (n = 2), lupus enteritis (n = 1), hypoproteinemia-induced edema (n = 1), and jejunal varices (n = 1). Most frequent extraluminal etiology affecting small bowel was adhesions accounting for 20.9% of total cases (n = 9) [Chart 1].[INLINE:1]

Several criteria were used to aid in the evaluation of the abnormal small bowel on contrast-enhanced MDCT. Attenuation/enhancement patterns of small bowel wall were evaluated and categorized into homogeneous, stratified, heterogeneous, and diminished enhancement. Length of involvement was categorized into focal (<6 cm), segmental (6–40 cm), and diffuse (>40 cm). Proximal small bowel is referred to the duodenum and/or jejunum, whereas ileum included in distal small bowel. Wall thickening was categorized into mild (3–4 mm), moderate (5–9 mm), and marked (>9 mm).[8]

Regarding the wall attenuation patterns [Table 1], most common in nonmalignant pathologies was stratified attenuation (50%) followed by homogeneous attenuation (45%). Diminished attenuation noted in the single case of small-bowel infarction [Figure 2]. Sixty percent of primary malignancy cases demonstrated heterogeneous wall attenuation [Figure 3]. Stratified attenuation pattern was found exclusively in nonmalignant pathologies. Regarding the symmetry of bowel wall involvement, nonmalignant pathologies exhibited predominantly symmetrical bowel wall involvement (70% of the cases), whereas asymmetrical wall thickening noted in malignant pathologies (88.88%) [Table 2]. Regarding the length of bowel involvement, nonmalignant pathologies showed segmental involvement (50%). Diffuse involvement of small bowel was noted solely in nonneoplastic pathologies. Focal involvement (55.55%) followed by segmental involvement (44.44%) was noted in malignant pathologies [Table 3]. No significant difference was noted in mean length involvement of malignant (128.20 ± 93.87 mm) and nonmalignant (90.19 ± 77.47 mm) pathologies with P value of 0.372 (>0.05). Nonmalignant pathologies exhibited more frequent involvement of distal small bowel loops (50%). Equal distribution in proximal and distal bowel loops was noted in malignant pathologies [Table 4]. Moderate and mild wall thickening was predominantly noted in nonmalignant conditions (85%). Marked wall thickening was noted in malignant pathologies mainly (77.77%) [Table 5]. Mean wall thickness in malignant pathologies (21.56 ± 15.68 mm) was significantly higher than mean wall thickness of nonmalignant pathologies (7.85 ± 3.69 mm) with P value of 0.031 (<0.05).{Table 1}{Figure 2}{Figure 3}{Table 2}{Table 3}{Table 4}{Table 5}

The most common MDCT enterography features of tuberculous enteritis were segmental, moderate, homogeneous, and stratified wall thickening with predominant distal small bowel loop involvement [Table 6]. Asymmetrical circumferential moderate wall thickening noted in duodenal TB cases (n = 2) [Figure 4]. Extraintestinal manifestations of TB found in the present study were necrotic lymph nodes (75%), splenic microabscesses (33.3%), pleural effusion (41.6%), tuberculous peritonitis (41.6%), hepatosplenomegaly (33.3%) and obstruction with proximal bowel dilatation (41.6%). In the current study, MDCT enterography signs found in adhesive small bowel obstruction were abrupt zone of transition between proximal dilated small bowel loops and collapsed distal bowel loops (n = 7) or with a double zone of transition and a dilated closed-loop appearance (n = 2), beak sign (66.6%) and fat notch sign (11.1%), whirled mesentery sign (22.2%), volvulus (11.1%) and multiple bowel angulations as the result of mesenteric retraction (11.1%) and extraluminal bands in the area of transition (44.44%) [Figure 5].{Table 6}{Figure 4}{Figure 5}

 Discussion



The thinner collimation possible with MDCT along with oral administration of iso-osmotic mannitol and intravenous bolus of contrast material may improve the sensitivity of CT for depicting small bowel pathologies as it has the potential to demonstrate intraluminal, mural, and extraintestinal abnormalities.

Most commonly encountered small bowel diseases were inflammatory pathologies (41.86%). Overall, intestinal TB was the most common etiology among the study population (27.90%).

The common bowel wall patterns found in nonneoplastic pathologies were segmental, symmetrical, mild to moderate wall thickening, homogeneous and stratified attenuation patterns with distal bowel involvement which correlates with a study by Megally et al.[1]

Common MDCT enterography features of tuberculous enteritis were circumferential, homogeneous and stratified attenuation, segmental, moderate wall thickening with predominant distal small bowel loop involvement. Terminal ileum with concurrent involvement of cecum was the most common site found in 75% cases. Patulous ileocecal junction was noted in two cases. This is in concordance to studies conducted by Megally et al.[1] and Zhao et al.[11] Extraintestinal manifestations as necrotic lymph nodes (75%), splenic microabscesses (33.3%), pleural effusion (41.6%), tuberculous peritonitis (41.6%), hepatosplenomegaly (33.3%), and obstruction (41.6%) were noted. Zhao et al.[11] stated that these features are useful imaging findings supporting the diagnosis of gastrointestinal TB.

MDCT enterography signs found in adhesive small bowel obstruction stated above were also described by Delabrousse et al.[12] and Petrovic et al.[13] Petrovic et al.[13] stated that the presence of extraluminal bands in the area of transitional zone has a high positive predictive value for adhesive small bowel obstruction.

The role of CT in patients with suspected ischemia of the small bowel include bowel wall thickening and edema, submucosal hemorrhage, increased or decreased bowel wall enhancement, mesenteric stranding, and pneumatosis intestinalis.[14] Moderate wall thickening with target (stratified) pattern of attenuation was the early finding of bowel ischemia results from edema of the submucosa, and those presented at later stage showed thinned out wall with diminished enhancement. These findings are comparable with the studies by Megally et al.[1] and Macari and Balthazar.[15] The characteristic small intestinal infarction feature, pneumatosis intestinalis was seen in one patient in the current study.

The common bowel wall patterns found in primary malignancy cases were segmental, asymmetrical, marked wall thickening, and heterogeneous enhancement patterns with proximal bowel involvement, most of those findings are correlating with the study by Megally et al.[1] except proximal small bowel (duodenal and/or jejunal) involvement which was relatively more frequent in our study. This contrary relationship may be due to fewer incidences of lymphoma cases in our study, which are more common in distal small bowel. On average, adenocarcinoma was distributed more proximally in the small intestine, most frequently in the duodenum, whereas lymphomas were more common distally, with nearly equal distribution between the jejunum and the ileum as stated by Talamonti et al.[16] and Schottenfeld et al.[17] is consistent with the present study where two third of adenocarcinoma were found in the duodenum and lymphomas involving the ileum and jejunum with equal frequency. The MDCT enterography features of asymmetrical circumferential, marked wall thickening with mucosal irregularity and heterogeneous attenuation pattern were found in all of the small bowel adenocarcinoma cases with involvement of proximal bowel in two third of cases. These findings are concordant with Cheung and Choi[18] study. Exceptionally, segmental involvement of the small bowel was noted in all three adenocarcinoma cases, which are not supported, by most of the available similar studies, probably due to delayed presentation.

The CT enterography features of lymphoma were marked asymmetric segmental wall thickening with homogeneous wall enhancement of the ileum and jejunum, associated with enlarged mesenteric lymph nodes. All of these findings were supported by Sailer et al.[19] study as diagnostic criteria for lymphoma. As stated by Lee et al.,[20] involvement of multiple and longer segments of bowel without significant obstruction is more common in lymphoma. Segmental involvement by lymphoma, as found in the present study is also supported by Macari et al.[8] study.

Metastases were the most common malignancies in the small bowel as stated by Sailer et al.[19] was consistent with the present study (44.44% cases). MDCT enterography features of homogeneous focal serosal implants of varying sizes involving mesenteric border of small bowel loops were found in intraperitoneal metastasis correlating to the study conducted by Macari et al.[8]

No significant difference was noted in mean length involvement of malignant (128.20 ± 93.87 mm) and nonmalignant (90.19 ± 77.47 mm) pathologies with P value of 0.372. Mean wall thickness in malignant pathologies (21.56 ± 15.68 mm) was significantly higher than mean wall thickness of nonmalignant pathologies (7.85 ± 3.69 mm) with P value of 0.031.

Small sample size is the major limitation of this study; second, its inability to demonstrate isolated mucosal abnormalities. The most common technical pitfall is inadequate small bowel distention resulting from inadequate ingestion, gastric retention, or rapid bowel transit of a large volume of neutral enteric contrast material. Another major limitation is the ionizing radiation produced by CT enterography. However, the risk of carcinogenesis due to CT in adult patients is quite low (0.02%–0.04%) according to recent studies.[21],[22] We believe that CT enterography is an excellent diagnostic tool for small bowel diseases when used in circumstances with appropriate justification.

 Conclusion



MDCT enterography is a powerful diagnostic tool for the study of small bowel disorders, including inflammatory disease, small bowel neoplasms, and mechanical obstruction. The use of neutral enteric contrast (iso-osmotic mannitol) with intravenous contrast, permit excellent assessment of bowel wall attenuation/enhancement patterns and mural pathologies. Apart from wall pathologies, complications/associated findings related to vessels and mesentery and lymph nodes can be evaluated in single setting, which is important in narrowing down the differential diagnosis. CT enterography offers the additional benefit of assessing abdominal and pelvic structures other than the small intestine, allowing alternative diagnoses to guide medical and surgical management.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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