Diagnostic Imaging

Endosonographic findings can be diagnostic for certain lesions, including gut duplication cysts, lipomas, bile duct stones, and some branch duct intraductal papillary mucinous neoplasias. However, in other situations, EUS imaging alone does not provide a confident diagnosis, and EUS-guided FNA or core biopsy (FNB) is indicated to facilitate cytologic or histologic diagnosis. Follow-up imaging may be indicated when EUS demonstrates a benign-appearing lesion, to identify interval growth or other signs suggestive of malignancy.

Tumor Staging

Initial evaluation of patients with gastrointestinal (GI) cancers includes assessment of operative risk and determination of tumor stage. Accurate staging determines prognosis and guides treatment decisions. Staging usually begins with noninvasive imaging such as computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET), which are generally superior to EUS for excluding distant metastases. EUS is often performed for tumor (T) and nodal (N) staging because it provides an accuracy of approximately 85% for locoregional staging of GI luminal cancers. Factors such as the number of malignant lymph nodes present may have both staging and prognostic relevance, and findings of EUS and CT or MR are complementary in some situations, for instance staging of vascular involvement by pancreatic cancer. Prior radiation therapy substantially decreases the T-staging accuracy of EUS.

EUS provides important nodal staging information in patients with lung, esophageal, and rectal cancer. The typical EUS characteristics of malignant lymph nodes are hypoechogenicity, round shape, smooth border, and size greater than 1 cm in the short axis; however, these features are at best 75% accurate for predicting malignancy in lymph nodes when compared with EUS FNA results or surgical histology. Overlap in appearance between benign and malignant lymph nodes makes nodal staging problematic by EUS, and the aforementioned criteria are less useful in lung cancer, rectal cancer, and cholangiocarcinoma. Overstaging may result from enlarged reactive lymph nodes that are deemed malignant on the basis of their EUS appearance alone. The addition of FNA improves nodal staging accuracy, but it also introduces the possibility of false-positive results, particularly when luminal cancer or Barrett esophagus is present. When aspirating lymph nodes, one should avoid traversing the primary tumor to minimize the risk of a false-positive cytologic finding and tumor seeding.

EUS has a limited role in establishing the presence or absence of distant metastasis (M stage). Sometimes a suspicious lesion (such as a left adrenal mass in a patient with lung cancer) is best approached for tissue sampling via EUS, or a previously unsuspected metastasis is diagnosed during EUS performed for local staging (e.g., a left lobe liver lesion in a patient with pancreatic cancer). EUS FNA appears reasonably safe when sampling the liver and adrenal glands.

EUS has been compared with PET in staging of esophageal cancer. PET has the ability to identify distant metastatic disease more accurately than EUS and CT, upstaging patients who were previously considered to have localized disease and excluding the possibility of curative R0 surgical resection. However, PET has limited accuracy in staging local and regional disease, and EUS remains superior to PET or CT for this indication. It appears that PET and EUS are complementary for optimal staging.

In patients with a pancreatic mass that is visible on CT, EUS and CT provide comparable accuracy with regard to vascular invasion and nodal involvement. However, EUS retains a key role in the evaluation of suspected pancreatic cancer for two reasons: EUS can detect abnormalities missed by CT and provides a preferred means of obtaining tissue specimens during the examination. EUS can also identify small metastatic lesions that were not identified on CT, including left lobe liver metastases, perivascular cuffing by tumor, and malignant involvement of celiac ganglia. The ability to obtain tissue specimens from these sites or from the primary pancreatic mass is important both for diagnosis and staging. Pancreatic mass lesions may be adenocarcinoma, other neoplasms such as neuroendocrine tumors or metastases, or benign conditions such as autoimmune pancreatitis, and these lesions cannot always be differentiated by clinical findings, imaging, and laboratory tests; EUS FNA and FNB allow efficient diagnosis in many such cases. Because EUS is superior to CT for detection of small pancreatic cancers, it should be performed if clinical or CT findings raise the question of a pancreatic tumor not visualized by CT.

EUS has a role in staging non–small cell lung cancer (NSCLC) because CT and PET have poor accuracy for the detection of mediastinal lymph node metastases. Lung cancer patients without suspicious mediastinal adenopathy on CT have up to a 35% prevalence of malignant mediastinal adenopathy. To limit false-positive and false-negative diagnoses of nodal stage, lymph node tissue sampling is advocated when it will change the management strategy (typically when a visualized lymph node is contralateral to the primary tumor). Sampling of all relevant nodal stations traditionally required surgical mediastinoscopy; however, a combination of EUS and endobronchial ultrasound (EBUS) for staging in NSCLC has a negative predictive value of 97% in the evaluation of mediastinal lymph nodes. EUS and EBUS are complementary, because neither test visualizes all relevant mediastinal lymph node stations. EUS also allows evaluation of the left adrenal gland for previously undetected distant metastases.

Tissue Acquisition

The development of linear EUS technology in the early 1990s allowed for EUS FNA and FNB of lesions within and extrinsic to the GI tract wall. Common indications for FNA include pancreatic mass lesions, nodal staging of esophageal, pancreatic, bile duct, and rectal cancers. EUS FNA is often the least invasive and most successful means of obtaining tissue specimens. Molecular characterization of tissue acquired during EUS is increasingly relevant to clinical care because it may predict prognosis and guide individualized patient management.

Less invasive approaches for establishing a tissue diagnosis include transabdominal ultrasound or CT-guided biopsy. These methods are well established and more cost-effective than EUS in certain scenarios (e.g., in patients with a pancreatic mass and suspicious liver lesions that can be targeted for percutaneous biopsy). However, these methods may be limited by their poor sensitivity in the diagnosis of small lesions or by concern for potential tumor seeding of the biopsy needle tract. EUS may be favored in these situations, as well as when EUS is indicated for other reasons, such as locoregional staging or celiac plexus/ganglia neurolysis. Although the diagnostic accuracy of EUS FNA for liver and nodal metastases is generally greater than 85%, this method is less accurate in other settings, including diagnosis of pancreatic cystic lesions, stromal tumors, previously radiated lesions, and autoimmune pancreatitis. EUS FNB safely improves the diagnostic accuracy of EUS in selected settings.

Therapy

EUS facilitates access to target structures for therapeutic intervention. The EUS needle is essentially a conduit that allows for the passage of guidewires or placement of materials with therapeutic intent. The first such therapies to be developed were EUS-guided celiac plexus/ganglia neurolysis or block and EUS-guided pseudocyst drainage. EUS is also used to facilitate drainage of otherwise inaccessible biliary and pancreatic ducts, angiotherapy for GI bleeding, placement of fiducials to guide radiation therapy, recovery of migrated stents, and transduodenal gallbladder drainage. EUS fine-needle injection (EUS FNI) is a developing means of delivering therapeutic agents into solid cancers and cystic neoplasms. The safety, efficacy, and clinical role of these procedures are discussed in more detail in other chapters.

Contraindications

Absolute contraindications to EUS are few and include unacceptable sedation risks. Coagulopathy (international normalized ratio [INR] >1.5) and thrombocytopenia (platelets <50,000) are relative contraindications to EUS FNA, which should be deferred if possible while coagulopathy or thrombocytopenia are corrected. Other relative contraindications include newly diagnosed cancer in a patient who has not undergone appropriate initial evaluation, altered anatomy prohibiting access via EUS, and the presence of intervening vital structures in the planned needle path for EUS FNA.

General Measures

EUS is performed in both outpatient and hospital settings, and open-access referrals are increasingly allowed. The setting and extent of the preprocedure evaluation can vary as a result. Initial evaluation should include a history, physical examination, and review of relevant medical records and imaging studies to determine the need, risks, benefits, alternatives, and timing of EUS and to document acquisition of informed consent ( Box 4.1 ). Because emergency EUS is uncommon, involved parties should generally have the necessary time for adequate evaluation and discussion of patient and family concerns. A professional and unhurried demeanor facilitates open communication and helps patients and their families to prepare for the exam.

When scheduling the procedure, outpatients should be instructed on their preparation responsibilities, the use of other medications, and the need to avoid alcohol and other sedatives. Patients should know that they will receive sedation or anesthesia, with resulting restrictions on postprocedure activities and the need for transportation assistance. Patients are informed of the potential signs and symptoms of adverse outcomes, as well as contact persons and phone numbers to call in the event they experience problems after their endoscopy. These instructions are reviewed after the procedure, with the patient and their accompanying adult.

Deeper sedation may be required for EUS than for routine endoscopic procedures because of the longer examination time and the need to minimize movement of the patient. As for all patient-sedated endoscopic procedures, careful monitoring is required throughout the procedure and recovery period. Administration of supplemental oxygen to all patients receiving sedation is recommended. Although conscious sedation or monitored anesthesia care (MAC) is routinely given for upper gastrointestinal (UGI) EUS, it is optional for rectal EUS.

UGI EUS is ideally performed following an overnight fast. At a minimum, patients should avoid solid foods for 6 hours and clear liquids (except sips of water to ingest medications) for 2 hours before the procedure. When there is concern for incomplete gastric emptying as a result of dysmotility or obstruction, a more prolonged clear liquid diet and airway protection during the exam may be advised. Retained gastric contents increase the risk of aspiration, produce imaging artifacts, and impair the overall examination quality.

Although some endosonographers perform rectal EUS after administering enemas alone, a full colon preparation is preferred, to optimize image quality and potentially reduce infectious complications associated with FNA.

Laboratory Studies

Surgical series have consistently demonstrated a lack of utility of routine preoperative studies such as complete blood count, blood cross matching, routine chemistry studies, coagulation parameters, urinalysis, chest radiograph, and electrocardiogram for patients without evidence of relevant underlying disorders. Routine preoperative testing in healthy patients rarely identifies abnormal findings and does not predict or correlate with patient outcomes. Therefore routine screening in asymptomatic patients is discouraged. Instead, endoscopists are advised to order preprocedure testing selectively, based on clinical suspicion arising from the initial evaluation, including a history of bleeding diathesis. This more focused approach greatly enhances the yield of preoperative testing without compromising patient outcomes.

An exception may be women of childbearing age in whom pregnancy is possible. Although pregnancy is not a contraindication to endoscopic procedures or conscious sedation, it may be important to know whether a woman is pregnant (e.g., to determine whether airway protection is required and prior to use of fluoroscopy). When possible, it is advisable to avoid or delay EUS until after delivery. When EUS cannot be delayed, appropriate measures should be undertaken to lessen the risk to the unborn child.

Medications

Antithrombotic Drugs

Suggested management of antithrombotic agents in patients undergoing EUS FNA or EUS-guided therapy is shown in Table 4.1 . These guidelines are based on recent consensus statements published by the American Society for Gastrointestinal Endoscopy (ASGE) and the British Society of Gastroenterology (BSG), which provide guidance on the management of antithrombotic drugs before and after endoscopy. Management of antithrombotic drugs before and after endoscopy should be individualized based on patient and procedural factors and determined in consultation with the patient and their other physicians.

TABLE 4.1

Antithrombotic Drug Management Prior to Endoscopic Ultrasound

Adapted from Acosta RD, Abraham NS, Chandrasekhara V, et al. The management of antithrombotic agents for patients undergoing GI endoscopy. Gastrointest Endosc . 2016;83:3–16; and Veitch AM, Vanbiervliet G, Gershlick AH, et al. Endoscopy in patients on antiplatelet or anticoagulant therapy, including direct oral anticoagulants: British Society of Gastroenterology (BSG) and European Society of Gastrointestinal Endoscopy (ESGE) guidelines. Gut . 2016;65:374–389.

Drug	Procedure	Management	Interval Between Last Dose and Procedure	Comments
Warfarin	EUS	Continue		Ensure that INR is not supratherapeutic
Warfarin	EUS FNA, EUS-guided therapy	Discontinue a	3–7 days (usually 5), INR should be ≤1.5 for procedure	Consider bridging therapy with heparin b ; usually safe to resume warfarin on the same or next day
Dabigatran, rivaroxiban, apixaban, edoxaban	EUS	Continue
Dabigatran	EUS FNA, EUS-guided therapy	Discontinue a	2–3 days if GFR is ≥50 mL/min, 3–4 days if GFR is 30–49 mL/min	Bridging therapy not recommended; resume drug when bleeding risk is low
Rivaroxiban, apixaban, edoxaban	EUS FNA, EUS-guided therapy	Discontinue a	2 days if GFR is ≥60 mL/min, 3 days if GFR is 30–59 mL/min, 4 days if GFR is <30 mL/min	Bridging therapy not recommended; resume drug when bleeding risk is low
Heparin	EUS	Continue
Heparin	EUS FNA, EUS-guided therapy	Discontinue a	4–6 hours for unfractionated heparin	Skip one dose if using low molecular weight heparin
Aspirin	All EUS procedures	Continue	N/A	Low-dose aspirin does not substantially increase the risk of endoscopic procedures
Aspirin with dipyridamole	EUS	Continue
Aspirin with dipyridamole	EUS FNA, EUS-guided therapy	Discontinue a	2–7 days	Consider continuing aspirin monotherapy
P2Y12 receptor antagonists (clopidogrel, prasugrel, ticlopidine, ticagrelor, cangrelor)	EUS	Continue
P2Y12 receptor antagonists (clopidogrel, prasugrel, ticlopidine, ticagrelor, cangrelor)	EUS FNA, EUS-guided therapy	Coronary stent in place: discuss with cardiologistNo coronary stent: Discontinue, a consider substituting aspirin	5 days (clopidogrel or ticagrelor), 7 days (prasugrel), 10–14 days (ticlopidine)	High risk of stent thrombosis for at least 12 months after insertion of drug-eluting coronary stent or at least 1 month after insertion of bare metal coronary stent

 

EUS, Endoscopic ultrasound; EUS FNA, endoscopic ultrasound-guided fine-needle aspiration; GFR, glomerular filtration rate; INR, international normalized ratio.

a May be appropriate to continue the antithrombotic drug in situations where the risk of thromboembolism is high (see Table 4.2 ), the perceived bleeding risk is relatively low, or endoscopic control of bleeding could be readily accomplished. See chapter text.

b Bridging therapy with low molecular weight heparin should be considered for patients discontinuing warfarin who are at high risk for thromboembolism, including those with (1) atrial fibrillation with a CHA ₂ DS ₂ -VASc score ≥2, (2) mechanical mitral valve; (3) mechanical aortic valve with other thromboembolic risk factors or older-generation mechanical aortic valve; (4) venous thromboembolism within the past 3 months, (5) known severe thrombophilia (protein C or S, or antithrombin deficiency, antiphospholipid antibodies). CHA ₂ DS ₂ -VASc score: Congestive heart failure [1 point], Hypertension [1 point], Age ≥ 75 years [2 points], Diabetes mellitus [1 point], Stroke [2 points], Vascular disease [1point], Age 65 to 74 years [1 point], Sex category, that is, female sex [1 point].

Periprocedural management of antithrombotic drugs requires an assessment of both the likelihood of procedurally induced bleeding and the patient’s underlying risk of thromboembolism. Endoscopic procedures may be categorized as having either a high risk or a low risk of inducing bleeding. EUS without FNA is regarded as a low-risk procedure similar to diagnostic upper GI endoscopy or colonoscopy. In general, because EUS is a low-risk procedure, antithrombotic therapy does not need to be interrupted in patients undergoing diagnostic EUS without FNA so long as anticoagulation is not supratherapeutic.

Guidelines classify EUS FNA as a high-risk procedure for inducing bleeding. The incidence of bleeding after EUS FNA in patients on various antithrombotic drugs is largely unknown. Hemorrhage has been reported after FNA in two of six patients receiving low molecular weight heparin and in none of 10 patients receiving clopidogrel. Although EUS FNA probably has a lower overall risk of clinically significant bleeding than other high-risk procedures such as endoscopic polypectomy or sphincterotomy, it is still considered a high-risk procedure because when bleeding results it may be inaccessible or uncontrollable by endoscopic means. Although there is limited experience with EUS FNB in patients on therapeutic doses of antithrombotic drugs, the risk of hemorrhage is likely to be somewhat higher with FNB than FNA and probably varies with the FNB needle design, as well as anatomic and patient factors. Some EUS-guided therapeutic interventions also have a risk of bleeding that exceeds that of EUS FNA alone.

The guidelines shown in Table 4.1 must be thoughtfully applied to individual patient situations. Although EUS FNA is categorized as a higher risk procedure, there are few empirical data to support this categorization, and discontinuation of antithrombotic therapy may have devastating results, particularly in patients who are at high risk for thromboembolic events such as those with recently placed coronary stents and some patients with mechanical heart valves or history of venous thromboembolism ( Table 4.2 ). Continuation of antithrombotic drugs in patients undergoing EUS FNA or selected EUS-guided therapies may be justified in some circumstances. In such patients, bloody aspirates may be obtained during EUS FNA, impairing cytologic analysis. This possibility should be considered when choosing the degree of negative pressure to apply during FNA and the duration of FNA passes. In patients taking antithrombotics, it may be prudent to use a smaller caliber (22 or 25 gauge) FNA needle and to use real-time on-site cytopathology evaluation to limit the number of FNA passes required.

TABLE 4.2

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