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M. L. Williford and S. S. Davis Jr.
study is interpreted as normal gastric emptying. This example
underscores the importance of evaluating the percentage empty
(or conversely the percentage remaining) at each time point
instead of focusing solely on the half-time. The half-time value is
potentially less representative of the overall clinical picture, especially if the study is stopped short of 4h.
Rapid Gastric Emptying
Patient 2 is a 56-year-old woman who underwent Nissen fundoplication in 2007. She then developed a paraesophageal hernia
with symptoms of dysphagia and reux. Given her prior foregut
surgery, the following gastric emptying study was obtained prior
to paraesophageal hernia repair to evaluate the gastric function
and ensure that a concurrent gastric emptying procedure was not
indicated (Fig.9.3).
At the 30-min mark, approximately 50% of the tracer had
exited the stomach based on the raw percentage empty. At the 1-h
Fig. 9.3 Gastric emptying study in patient status post-Nissen fundoplication,
rapid emptying
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mark, approximately 70% of the tracer had exited the stomach.
Therefore, this study is interpreted as rapid gastric emptying. This
example represents an appropriate preoperative use of the study.
The surgeon wanted to ensure that the patient did not have delayed
gastric emptying. If that were the case, a gastric emptying procedure such as a pyloroplasty may have also been performed.
Instead, because the patient’s emptying was rapid, no additional
procedures were indicated and she proceeded with paraesophageal hernia repair.
Delayed Gastric Emptying
Patient 3 is a 55-year-old woman with a history of gastric atony
who underwent partial gastrectomy with gastrojejunostomy. She
developed severe reux and recurrent episodes of aspiration pneumonia, and her nutrition declined to the point where she was
TPN-dependent. The following gastric emptying study was
obtained prior to further surgical intervention (Fig.9.4).
Fig. 9.4 Severe delayed gastric emptying
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M. L. Williford and S. S. Davis Jr.
At the 1-h mark, 97% of the tracer remained in the stomach,
and at the 1.5-h mark, 85% of the tracer remained in the stomach.
This study was interpreted as delayed gastric emptying, and the
study was terminated prior to the 4-h mark. These ndings were
relatively worse when compared to a previous study, and the
patient proceeded to undergo a completion gastrectomy.
Borderline Delayed Gastric Emptying
The nal example is again of patient 1, the 36-year-old woman
with gastroparesis who originally underwent gastric stimulator
placement in 2012. Her symptoms returned in 2019, and the following gastric emptying study was obtained (Fig.9.5).
This example again underscores the importance of continuing
the study to the 4-h mark, as well as understanding the clinical
indication. The raw percentage empty is within normal limits at
the 1-h and 2-h time points, but the rate of emptying slows to the
point at which the percentage of tracer remaining in the stomach
at the 4-h time point is abnormal. These ndings are not nearly as
pronounced as the delayed gastric emptying seen in Patient 3, but
Fig. 9.5 Delayed emptying in 4-h study
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given this patient’s clinical course the ndings were indicative
that the gastric stimulator warranted interrogation. This patient
proceeded to undergo gastric stimulator battery replacement.
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Clinical Applications
Understanding the principles of a gastric emptying study will
allow a clinician to better understand how this test can be used to
prevent postoperative failures and complications. The result may
affect the surgeon’s operative plan, particularly if the patient has
undergone previous foregut surgery or has atypical symptoms.
The following examples represent clinical scenarios in which a
preoperative gastric emptying study would be useful.
1. A patient with gastroparesis prior to placement of a gastric
pacemaker or pyloroplasty. It is important to document gastric
emptying preoperatively as a baseline study for later comparison.
2. A patient who has previously undergone foregut surgery who
develops symptoms concerning delayed gastric emptying
when considering further surgical intervention.
3. Prior to performing a paraesophageal hernia repair to determine if any concurrent gastric emptying procedure should be
performed.
4. A patient who has previously undergone partial gastrectomy,
now with symptoms of either delayed or rapid gastric emptying prior to any further surgical intervention.
The following examples represent clinical scenarios in which a
postoperative gastric emptying study would be useful.
1. Following gastric pacemaker insertion or pyloroplasty to document function relative to preoperative values.
2. Prior to removing a gastrostomy tube following paraesophageal hernia repair to ensure that the stomach is emptying
adequately.
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M. L. Williford and S. S. Davis Jr.
Conclusion
When ordering a gastric emptying study, it is important to have a
dened clinical question and consider how the results will affect
the operative plan. Knowing how the study is performed and having a basic framework for interpretation will ultimately allow for
improved clinical decision-making.
References
1. Grifth GA, Owen GM, Kirkman S, et al. Measurement of the rate of
gastric emptying using chromium-51. Lancet. 1966;1:1244–5.
2. Abell TL, Camilleri M, Donohoe K, etal. Consensus recommendations
for gastric emptying scintigraphy: a joint report of the American
Neurogastroenterology and Motility Society and the Society of Nuclear
Medicine. J Nucl Med Technol. 2008;36:44–54.
3. Tougas G, Eaker EY, Abell TL, etal. Assessment of gastric emptying using
a low fat meal: establishment of international control values. Am J
Gastroenterol. 2000;95:1456–62.
4. Davis, S. Nuclear medicine gastric emptying study. Atlanta, GA: Emory
University School of Medicine. 2020.
Endoscopic Ultrasound
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LindseyC.Shipley andAliM.Ahmed
Introduction toEUS
In the 1980s, exible endoscopy and ultrasound merged to form
endoscopic ultrasound (EUS) [1]. EUS enables the visualization
of structures located inside and outside of the luminal gastrointestinal tract such as lymph nodes and pancreatic lesions without
the interference of other organs, bowel gas, fat, or bone [2].
Ultrasound utilizes absorptive, reective, refractive, and scatter
properties to construct a representative image of tissue structure
[3]. With the creation of endoscopic ultrasound ne-needle aspiration (EUS-FNA) in 1991 and recent advancements, both the
diagnostic and therapeutic capacities of EUS have expanded tremendously [1]. EUS now assists with the diagnosis and staging
of malignancies via EUS-FNA, EUS elastography, and contrastenhanced EUS.Therapeutically, EUS has been used for celiac
A. M. Ahmed (*) · L. C. Shipley
Division of Gastroenterology and Hepatology, University of Alabama at
Birmingham, Birmingham, AL, USA
e-mail: amahmed@uabmc.edu
© 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_10
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plexus neurolysis, pseudocyst drainage, pancreaticogastrostomy, brachytherapy, and gene or cellular therapy. Moreover, its
diagnostic and therapeutic potentials can span across organ systems and include the lung, liver, pancreas, and surrounding
lymph nodes [4].
L. C. Shipley and A. M. Ahmed
Application forForegut Anatomy andPhysiology
The primitive gut tube develops during weeks 3–4 and is divided
into three distinct sections: foregut, midgut, and hindgut. The
foregut is supplied by the celiac artery and consists of the esophagus, stomach, rst and second portions of the duodenum, liver,
pancreas, biliary apparatus, and gallbladder [5]. Parasympathetic
innervation is via the vagus nerve and sympathetic innervation is
by the preganglionic thoracic splanchnic nerves and postganglionic cell bodies, such as the celiac ganglion [6]. The trachea separates from the esophagus by forming a ventricular diverticulum
off the primitive pharynx. By weeks 4–5, the complete transesophageal septum is created separating the respiratory and digestive tracts. Failure of this separation can result in esophageal
atresia or tracheoesophageal stula [7]. The stomach develops via
a fusiform dilation by week 4. The remainder of the foregut forms
via budding organs using an abundant number of signaling pathways and transcription factors including Hnf1b, Hnf6, retinoic
acid (RA), and Prox1 [8]. The rst and second portions of the
duodenum from the end of the foregut. As the stomach rotates,
this portion of the duodenum rotates to the right to move into the
retroperitoneal space. The liver and biliary tree appear around
week 3 as an outgrowth from the most distal foregut, the future
ampulla of Vater. The liver grows rapidly forming a large portion
of the abdominal cavity, and its diverticulum then expands to form
the gallbladder and the cystic duct. In week 5, the pancreas forms
a ventral and dorsal bud off the duodenum. The dorsal bud forms
the upper half of the pancreatic head, isthmus, body, and tail,
while the ventral bud forms the uncinate process and inferior part
of the head of the pancreas. As the pancreatic buds fuse, their
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ducts anastomose to form the main pancreatic duct. Foregut malformations can occur at any point during this process and include
esophageal atresia, esophageal stenosis, pyloric stenosis, atresia
of the gallbladder and bile ducts, liver malformations, accessory
pancreatic tissue, Meckel’s diverticulum, duplication cysts, and
annular pancreas [9]. EUS is currently utilized to evaluate and
occasionally treat many of these abnormalities.
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Role ofEUS inEvaluation andDiagnosis
ofForegut Pathology
Pretreatment Staging forEsophageal, Gastric,
andPancreatic Cancer
EUS is a useful tool to assist with pretreatment staging in esophageal, gastric, and pancreatic malignancies. Accurate staging can
prevent both inadequate and unnecessary treatments and assist
with balancing benets versus risks of morbidity related to treatment.
Esophageal Cancer
Once esophageal cancer is identied, usually via endoscopy, the
next step staging studies include CT and PET.Occasionally, these
imaging modalities do not demonstrate distant disease. In this
case, EUS is the most accurate modality for locoregional staging
and is recommended to determine the extent of the disease. EUS
can provide more information on the degree of tumor invasion (T
status) and lymph node involvement (N status) [10]. The EUS
image below demonstrates tumor invasion into the adventitia suggesting T3 esophageal cancer (Fig.10.1). Furthermore, in a study
of 125 patients, EUS-FNA can increase the sensitivity and specicity of identication of lymph node as compared to EUS alone
(87% vs. 74%, p= 0.012) [11]. Current guidelines recommend
EUS with or without FNA in cases where it is likely to change
management such as condence in clinical staging and helping to
guide appropriate management and avoid unnecessary treatment.
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Fig. 10.1 Pretreatment esophageal cancer staging
L. C. Shipley and A. M. Ahmed
The data on EUS elastography for esophageal cancer is limited;
however, it may have a role in the future to reduce the need for
FNA of lymph nodes. Contrast-enhanced EUS is limited in esophageal carcinoma as these tumors are not highly vascularized [12].
Gastric Cancer
EUS is a moderately accurate modality to determine staging for
gastric cancer. In a meta-analysis of 22 articles, EUS-pooled
accuracy T staging was 75%, with the highest accuracy for T3,
followed by T4, T1, and T2. EUS-pooled accuracy for N staging
was 64%, sensitivity 74%, and specicity 80% [2]. Another metaanalysis of 66 articles and 7747 patients with gastric cancer who
were staged with EUS also found that performance is lower in
diagnosing supercial tumors (T1a vs. T1b sensitivity 0.87 and
specicity 0.75) and lymph node status (sensitivity 0.83, specic-
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ity 0.67). Further research is needed to determine its use in clinical practice [13].
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Pancreatic Cancer
In one prospective study of 132 patients with suspected pancreatic
tumor, sensitivity and specicity of EUS (99% and 100%) were
found to be superior to US (67%, 40%) and CT (77%, 53%) and
equal to ERCP (sensitivity 90%) in pancreatic tumor diagnosis.
Further, EUS provides direct visualization of tumor size and
shape, while ERCP only provides indirect evidence. However,
EUS, similar to other modalities’ accuracy for malignancy, was
76% and 46% for focal inammation [14]. With the addition of
ne-needle aspiration (EUS-FNA), the accuracy, sensitivity, and
specicity for malignancy diagnosis rose to 86%, 84%, and 96%,
respectively, in a study of 333 patients [15]. EUS has an important
role in preoperative staging due to its accuracy of delineating
location, size, lymph node metastasis (sensitivity 69%, specicity
81%), vascular invasion (85%, 91%) and to predict resectability.
Further, no other modality can simultaneously assess atypical
portocaval lymph nodes, ascitic uid, peritoneal nodules, or suspected liver metastasis [16].
Evaluation andDiagnosis ofForegut Submucosal
Nodules
Submucosal nodules, also known as submucosal tumors (SMT),
are often asymptomatic and incidentally discovered during routine endoscopy. These lesions are best characterized by EUS both
via ultrasound and biopsy, especially if the lesion is less than
0.5cm. EUS can provide information regarding malignant potential, origination, and distinguishing solid versus cystic and extraluminal extension. Lesions commonly seen at EUS include
leiomyoma, gastrointestinal stromal tumor (GIST), aberrant pancreas, lipoma, duplication cyst, and varices. The ability to use
Doppler during EUS can discern varices from the remainder of
the lesions and thus a safe target for tissue diagnosis [17]. EUSFNA or EUS trucut biopsy (EUS-TCB) can be utilized for tissue
diagnosis. In a small study of 19 patients comparing EUS-guided
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