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7 Role ofCT Imaging inForegut Physiology andBenign Pathology
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89
ing between the two studies. An UGI is a dynamic study, and
therefore, the total dose of radiation varies, while the dose with
CT is more constant. While the overall dose delivered to tissues is
less with UGI, the total effective dose is relatively low for both
studies. Typical values for an adult patient average 6 and 10mSv
for UGI and CT, respectively [16].
Conclusions
Advances in technology and technique have signicantly
improved the sensitivity and specicity of CT in the diagnosis and
evaluation of upper GI tract pathology. While CT imaging is predominantly an anatomic study with limited functional capability,
it may serve as the primary diagnostic tool or as an adjunct to
other modalities such as UGI, manometry, and endoscopy.
Modern- day surgeons will benet from a basic understanding of
the methods of image acquisition to expedite accurate diagnoses.
Thorough knowledge of the appearance of normal and surgically
altered anatomy and ndings specic to disease processes will be
imperative in the interpretation of results and guiding clinical
decision-making.
References
1. Ba-Ssalamah A, etal. Dedicated multidetector CT of the stomach: spectrum of diseases. Radiographics. 2003;23(3):625–44.
2. Ba-Ssalamah A, et al. Dedicated multi-detector CT of the esophagus:
spectrum of diseases. Abdom Imaging. 2009;34(1):3–18.
3. Young CA, etal. CT features of esophageal emergencies. Radiographics.
2008;28(6):1541–53.
4. Lambert L, et al. The predictive value of computed tomography in the
detection of reux esophagitis in patients undergoing upper endoscopy.
Clin Imaging. 2018;49:97–100.
5. Eren S, Ciriş F.Diaphragmatic hernia: diagnostic approaches with review
of the literature. Eur J Radiol. 2005;54(3):448–59.
6. Mazaheri P, etal. CT of gastric volvulus: interobserver reliability, radiologists’ accuracy, and imaging ndings. Am J Roentgenol.
2018;212(1):103–8.
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7. Carbo AI, etal. Imaging ndings of successful and failed fundoplication.
Radiographics. 2014;34(7):1873–84.
8. Rodríguez Carnero P, et al. Multislice computed tomography for the
study of complications of gastric fundoplication. Radiología (English
Edition). 2014;56(5):435–9.
9. Rabushka LS, Fishman EK, Kuhlman JE.CT evaluation of achalasia. J
Comput Assist Tomogr. 1991;15(3):434.
10. Licurse MY, etal. Utility of chest CT for differentiating primary and secondary achalasia. Clin Radiol. 2014;69(10):1019–26.
11. Carter MD, Robert C, Smith RC, Burrell MI, Traube M.Differentiation
of achalasia from pseudoachalasia by computed tomography. Am J
Gastroenterol. 1997;92(4):624–8.
12. Pannu D, etal. Prospective evaluation of CT esophagram ndings after
peroral endoscopic myotomy. Gastrointest Endosc. 2016;84(3):408–15.
13. Cai M-Y, etal. Thoracic CT after peroral endoscopic myotomy for the
treatment of achalasia. Gastrointest Endosc. 2014;80(6):1046–55.
14. Reddy CA, etal. The clinical impact of routine esophagram after peroral
endoscopic myotomy. Gastrointest Endosc. 2021;93(1):102–6.
15. Strauss C, et al. Computed tomography versus water-soluble contrast
swallow in the detection of intrathoracic anastomotic leak complicating
esophagogastrectomy (Ivor Lewis): a prospective study in 97 patients.
Ann Surg. 2010;251(4):647.
16. Bingham J, etal. Computed tomography scan versus upper gastrointestinal uoroscopy for diagnosis of staple line leak following bariatric surgery. Am J Surg. 2015;209(5):810–4.
17. de Aretxabala X, etal. Gastric leak after sleeve gastrectomy: analysis of
its management. Obes Surg. 2011;21(8):1232–7.
M. L. Diller and D. Shouhed
3D Modeling withCT
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AngelaM.Kao andPaulD.Colavita
Introduction
Effective treatment of benign and malignant diseases of the
esophagus and stomach often requires a combination of diagnostic tests to adequately evaluate the anatomy and physiologic function of the esophagus and stomach. The role of conventional
computed tomographic (CT) imaging in the diagnostic evaluation
of foregut disease is often an adjunct test; however, it remains a
mainstay of preoperative staging of esophageal and gastric malignancies. In patients who undergo foregut surgery, CT imaging is
commonly obtained to detect postoperative failures or complications such as esophageal leak.
In recent years, advancements in technology, such as the
multidetector CT scanner, have enabled three-dimensional
(3D) reconstruction using methods such as multiplanar reformation and volume rendering. Following these advances, 3D
CT has gained renewed interest in its use during preoperative
8
A. M. Kao · P. D. Colavita (*)
Division of Gastrointestinal Surgery, Department of Surgery, Carolinas
Medical Center, Charlotte, NC, USA
e-mail: Paul.D.Colavita@atriumhealth.org
© Society of American Gastrointestinal and Endoscopic Surgeons
(SAGES) 2023
A. D. Patel et al. (eds.), The SAGES Manual of Physiologic
Evaluation of Foregut Diseases,
https://doi.org/10.1007/978-3-031-39199-6_8
91
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evaluation and surgical planning. While the clinical value of
3D CT reconstruction has been extensively reported in other
elds such as maxillofacial surgery and orthopedic surgery,
similar widespread use has been slower to gain traction in
abdominal surgery due to the complexity in image processing
of various abdominal soft tissues, compared to bones or vessels [1]. The adoption of 3D CT modeling in abdominal surgery has progressively increased over the past decade, with
newer clinical applications of 3D reconstruction for the esophagus and stomach.
Multidetector CT imaging of the esophagus and stomach with
3D reconstruction offers many advantages, including improved
diagnosis of pathologic anatomy and increased staging accuracy
of malignancies. The diagnostic yield of traditional CT imaging
has been limited by the collapsed lumen of the esophagus which
prevents accurate evaluation of esophageal wall thickening and
detection of endoluminal masses. Compared to two-dimensional
imaging, 3D visualization of a lesion in multiple planes enhances
the viewer’s perspective and depth perception, allowing for
improved characterization of morphologic features and relation to
adjacent structures [2]. Optimal visualization of the esophagus
and accurate characterization of pathologic lesions can be facilitated by adequate distention of the esophageal lumen with air or
liquid, as well as obtaining images with the patient in prone and
supine positions [3].
A. M. Kao and P. D. Colavita
Esophageal Injuries
Initial evaluation of esophageal injuries often begins with a contrast swallow study using water-soluble contrast followed by thin
barium; however, CT has been increasingly used due to its widespread availability and ability to rapidly obtain high-resolution
images. In patients with a negative contrast swallow study, CT is
a valuable noninvasive diagnostic test that can detect esophageal
perforation with high sensitivity. CT ndings suggestive of esophageal perforation include contrast extravasation, as well as indirect signs, such as mediastinal inammation, subcutaneous or
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muscular emphysema of the neck and/or chest, widened mediastinum, pneumomediastinum, pneumopericardium, left-sided pleural effusion, or pneumothorax [4].
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Achalasia
Although CT is not routinely indicated in the evaluation and
workup of achalasia, it can serve as a useful adjunct in complicated cases by detecting atypical features that may indicate the
presence of malignancy or other esophageal pathology [4].
Neoplastic inltration of the submucosa layer in the distal esophagus can result in pseudoachalasia, with symptoms that mimic
idiopathic achalasia. In advanced achalasia, CT shows uniform
dilatation of a long esophageal segment, with normal-appearing
boundaries surrounded by mediastinal fat. In contrast, patients
with pseudoachalasia often demonstrate CT ndings of a mass or
wall thickening at the site of esophageal narrowing, with asymmetric or marked wall thickening >10mm being highly suggestive of pseudoachalasia.
3D CT modeling has also been used for surgical planning of
achalasia with complex anatomy. Based on a patient’s CT scan
demonstrating a markedly tortuous aorta, Marano etal. printed a
3D model of the esophagogastric junction that allowed the surgeon to measure the position of the esophagus relative to the thoracic aorta [5]. Demonstration of the interspatial relationship of
the esophagus with critical surrounding structures using 3D CT
modeling enabled preoperative discussion of optimal surgical
approaches and facilitated the ability to plan possible critical
maneuvers.
Hiatal Hernia
Hiatal hernias refer to herniation of the stomach into the thoracic cavity and can cause reux, epigastric, or retrosternal
pain, respiratory symptoms, or can be incidentally detected in
asymptomatic patients. Types of hiatal hernia are typically
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A. M. Kao and P. D. Colavita
grouped into four types. Type I hernias are also labeled sliding
type, with the displacement of the gastroesophageal junction
(GEJ) upward into the posterior mediastinum, with no aspect of
the stomach superior to the GEJ and no other herniated organs.
Type II hernias are paraesophageal hernias, where the stomach
herniates into the thoracic cavity with a non-displaced gastroesophageal junction. Type III hernias are also paraesophageal
hernias and are dened by herniation of the stomach superior to
an also herniated GEJ.Type IV hernias involve the herniation
of other abdominal contents into the thoracic cavity. On CT
imaging, the demonstration of gastric folds in the chest is
pathognomonic and frequently visualized, particularly with
adequate distention of the stomach and esophagus [4]. Surrogate
markers of the GEJ, such as the angle of His and abrupt change
in tubular contour, visualized more than 2cm above the level of
the diaphragm also indicate the presence of a hiatal hernia [6].
Sliding hiatal hernias appear as axial herniation of the stomach
as a retrocardiac mass with displacement of the cardia into the
thoracic cavity, while type II hernias are associated with xation of the gastric cardia.
The potential clinical application of 3D CT imaging has
recently been described for hiatal hernias. Kavic etal. describe
using surface modeling techniques to create 3D models of the
various types of hiatal hernias [7]. The ability to appreciate relevant anatomy from different viewpoints enables a more comprehensive understanding of spatial relationships and facilitates
preoperative planning, particularly in laparoscopic surgery, where
strategic port placement is critical [8]. Recent interest in tailoring
hiatal closure techniques to the size of the hiatal defect has also
led to CT measurements of esophageal hiatus surface area (HSA)
using 3D imaging. Ouyang etal. described a signicantly larger
mean HSA of 6.9cm2 and 11.5cm2 in patients with type I and
type III hiatal hernias, respectively, compared to those without
hiatal hernia [6]. Similarly, 3D CT volumetric measurements can
be utilized for surgical planning of paraesophageal hernia repair.
In a retrospective analysis, the authors of this chapter demonstrated a signicant correlation between increases in HSA and
hernia sac volume with emergent case status and operative nd-
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ings of gastric volvulus and incarceration [9]. Furthermore, preoperative 3D CT measurements predicted the inability to perform
primary cruroplasty and the need for salvage gastropexy and
relaxing incisions [9].
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Esophageal Stenosis
The use of multidetector CT is noninvasive and a valuable alternative diagnostic tool for evaluating patients with esophageal
stenosis that may not be amenable to endoscopic evaluation. In
these patients, 3D CT can accurately determine the location and
length of the stricture, as well as visualize the esophagus and
stomach distal to the stenosis [3]. Findings of esophageal wall
thickening, obliteration of surrounding fat planes, and mediastinal adenopathy can distinguish between benign and malignant
etiologies of esophageal stenosis. Benign esophageal strictures,
such as those caused by peptic ulcer disease, are often characterized by diffuse, regular, or concentric wall thickening and uninvolved surrounding fat planes. In contrast, irregular asymmetric
wall thickening, obliteration of the fat planes between the
esophagus and adjacent structures, and presence of mediastinal
adenopathies point to malignant etiologies of stenosis. The use
of post-image processing also enables virtual endoscopic assessment of intraluminal, mural, and extraluminal pathology; however, limitations of CT include the inability to obtain histologic
biopsy or to treat stenosis using dilation and other endoscopic
techniques.
Placement of a self-expandable stent in patients with an unresectable neoplasm causing esophageal stenosis can palliate symptoms of dysphagia; however, radial forces exerted by the stent can
cause mass effect on adjacent mediastinal structures, potentially
leading to compression of the tracheobronchial tree and airway
compromise [10]. CT assessment of the area of stenosis and
degree of compression on adjacent structures facilitates pretreatment planning, including choice of size and type of stent. The use
of 3D CT offers potential advantages over traditional axial CT,
including the ability to obtain internal images of the upper air-
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ways and esophagus, allowing for easier measurement of the stenosis caliber and length, as well as potentially preventing risky
maneuvers [11].
A. M. Kao and P. D. Colavita
Esophageal Malignancy
Preoperative staging of esophageal cancer currently remains the
most important indication for MDCT of the esophagus. In addition to upper endoscopy, CT is an important test in the workup
and staging of esophageal cancer, particularly in the detection of
regional nodal spread and distant metastases to the liver and lung.
Compared to enhanced 2D CT imaging, which is limited in its
evaluation of the spatial location and overall length of esophageal
tumors and understages tumor depth in 40% of patients, 3D CT
imaging provides additional information regarding endoluminal
morphology and longitudinal extent of tumors that previously was
obtained using conventional barium study [12]. Furthermore, 3D
CT provides a large advantage in the evaluation of tumor response
to neoadjuvant chemotherapy and radiation.
Esophageal malignancy is best represented on 3D CT imaging
by asymmetric wall thickening of the esophagus with increased
heterogeneous enhancement compared to adjacent mucosa; however, diffuse symmetric thickening greater than 3mm should also
raise suspicion for malignant pathology. In their 3D CT protocol,
Panebianco etal. identied pathologic wall thickening measuring
between 3.0 and 30mm in 97% of patients with neoplasia compared to normal esophageal wall thickness measuring less than
3mm [13]. Eccentric lesions with intact overlying mucosa and
smooth lobulated margins without obliteration of esophageal layers into the adjacent fat were characterized as submucosal tumors
[12]. While CT poorly distinguishes between T1 and T2 diseases,
imaging ndings such as stranding or increased attenuation of the
paraesophageal fat, ill-dened soft tissue density around the
tumor, mucosal irregularities, or bulging of the outside border are
suggestive of T3 disease, with tumor invasion into the adventitia
and paraesophageal fat [13]. Similarly, invasion of adjacent structures evidenced by mass effect or loss of fat planes is consistent
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with the T4 stage. Correlation between 3D CT tumor staging and
pathologic ndings in patients who underwent demonstrated an
overall sensitivity of 92% [13]. Cai etal. demonstrated that 3D
CT reconstruction was superior to traditional gastroscopy in
determining the location of pathologic changes and extent of disease, or tumor stage, with greater accuracy [14]. Accuracy of
tumor staging by 3D CT is also higher than previously reported
rates with axial CT imaging, demonstrating enhanced diagnostic
capabilities using 3D reconstruction techniques.
3D CT reconstruction enables accurate assessment of the
tumor location relative to adjacent structures and can aid in determining the surgical approach. The ability to characterize esophageal tumors using a noninvasive method is particularly
advantageous in patients with malignant esophageal narrowing
that is not amenable to endoscopy. In one-third of patients who
were unable to undergo gastroscopy, the use of 3D reconstruction
enabled accurate preoperative evaluation and planning of surgical
treatment [14]. Wada et al. described the efcacy of 3D CT in
delineating bronchial artery anatomy prior to esophagectomy,
allowing for the identication of vascular anomalies and bronchial artery preservation, the latter of which has been shown to
signicantly reduce pulmonary complications and tracheal ischemia [15].
In addition, multidetector CT (MDCT) plays an important role
in the evaluation of postoperative complications including the
presence and severity of esophageal perforation. Furthermore,
MDCT can detect tumor recurrence after esophagectomy with an
accurate demonstration of locoregional recurrent esophageal
tumor on MDCT.Furthermore, it is superior for the detection of
distant metastatic disease and can also accurately delineate the
neoesophagus and its surroundings [4].
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Esophageal Atresia
Esophageal atresia (EA) with tracheoesophageal stula (TEF) is a
correctable congenital anomaly that occurs in up to 0.03% of neonates, with distal TEF being the most common type. Preoperative
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evaluation of EA-TEF patients has traditionally included chest
radiographs, as well as invasive tests such as endoscopy and bronchoscopy. Recently, several have advocated for the role of CT
imaging in the preoperative evaluation of EA-TEF patients, as it
is a noninvasive test that can delineate the anatomy of the tracheobronchial tree, both esophageal pouches, and the exact location of
the TEF.Importantly, the use of 3D images can demonstrate the
spatial relationship between the proximal esophageal pouch and
distal stula and provide an accurate assessment of the interpouch
gap, which is critical to planning the surgical approach, as well as
risk stratication and prognosis [16]. Compared to rough assessment on chest radiographs that tend to underestimate the interpouch distance, several studies have reported the superiority of
3D CT in accurately assessing interpouch distance and stula
level, as well as the detection of concomitant mediastinal or thoracic anomalies [17, 18]. Mahalik etal. reported in their study of
type C TEF (the most common type), the majority of patients had
a short-to-intermediate interposition gap, and thus, preoperative
CT evaluation did not change the surgical management [16].
Thus, the benets are outweighed by the signicant risk of exposure to ionizing radiation and the potential for future radiationinduced malignancies.
A. M. Kao and P. D. Colavita
Gastric Diseases
CT is commonly used in the evaluation of gastric diseases; however, its sensitivity and specicity vary in different diseases. While
endoscopy is often the initial diagnostic test in the evaluation of
gastric lesions, it is an invasive test with limited ability, particularly
with submucosal or extramural pathology. The use of stomach CT
protocols that use effervescent granules to ll the gastric lumen
with air and ensure the stomach is adequately distended can improve
diagnostic sensitivity and specicity [19]. Recently, 3D CT imaging has also gained wide clinical application due to advances in
post-image processing that have enabled virtual endoscopic assessment of gastric mucosa. Advantages of 3D CT over traditional
endoscopy include the detection of mural and extramural gastric
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