How does EUS combine with ERCP?

This paper is excerpts from the research paper of Professor Sun Bo, director of endoscopy center

In Longhua hospital affiliated to Shanghai University of Traditional Chinese Medicine.

There are two main modes of EUS combined with ERCP: EUS before ERCP and EUS after ERCP.

EUS before ERCP

EUS before ERCP is commonly applied in the following situations:

1.      Suspected stones in bile ducts or biliopancreatic duct stenosis or dilatation

When the nature/reason of bile duct stones or biliopancreatic stricture or dilatation is not clear, EUS can help us determine whether we should do ERCP or not.

For example, for the patients of acute biliary pancreatitis who underwent conservative treatment and missed the best ERCP intervention time, we need to consider whether intra bile duct stones have been expelled. It has been reported that about 70% of bile duct stones (especially those below 0.5cm in diameter) can be discharged from bile duct by themselves. EUS examination could avoid unnecessary ERCP. In this way, EUS before ERCP could help with clarify its indications.

2.    To identify the growth of bile duct lesions so as to determine the way of biopsy

EUS can identify the growth of the bile duct lesion (tumor), if the tumor grows into the cavity, ERCP cell brush has higher positive rate. However, if the tumor grows into sub mucosa, or grows into the outside cavity, or the bile duct lesion is caused by external pressure, the positive rate of ERCP cell brush biopsy would be lower. For the latter situation, EUS –FNA is a choice.

3.Apply EUS-FNA in biliopancreatic tumor with unknown pathology so as to determine treatment strategy

(eg.PAC vs. lymphoma)

Different types of biliary tract or pancreatic tumors are treated in different methods. For example, for pancreatic cancer with obstructive jaundice, in which there is no opportunity for operation, biliary metal stent drainage is usually required. But if pancreatic head is lymphoma, the lesion may completely disappear after radiotherapy and chemotherapy. Therefore, pathology before ERCP can clarify the treatment method, such as the way of drainage.

4. Identify intra bile duct tumor range (RFA, EMBE) so as to determine the specification of the devices, such as metal stent length and diameter

EUS can assist in determining the range of tumor, and the selection of the range of radiofrequency therapy and the length of auxiliary stent can be determined when biliary tract radiofrequency therapy or stent implantation under ERCP.

The situations when EUS is not required before ERCP:

1. Bile duct stones have been clearly diagnosed by image inspection.

Distal bile duct obstruction has been excluded.

2. The pathology of a distant biliopancreatic tumor is well proved, for example, by percutaneous liver puncture metastasis.  

3. If pathologically confirmed papillary carcinoma has distant metastasis and endoscopic resection is impossible, EUS is unnecessary.

EUS after ERCP

In this case, EUS mainly plays a remedial role.

1. EUS-FNA is used after biopsy failure by ERCP

If there is no definite diagnosis by ERCP bile duct biopsy, then EUS-FNA can be used to obtain pathological diagnosis.

2.ERCP drainage failure/failure to complete -- EUS-BD、EUS-PD、EUS-GBD

When ERCP drainage fails or cannot be completed, EUS guided bile and pancreatic duct drainage can be used as an alternative.

Understand the limitations of EUS

1. After subtotal gastrectomy and gastrointestinal diversion operations, some structures especially the distal part of common bile duct can hardly be observed by EUS.

2. Previous ERCP may also cause some influences on EUS, such as the presence of gas in the bile duct after papillary muscle incision or intestinal bile duct fistula, which may interfere with EUS exploration.

3. Echo of the stent in the bile duct or pancreatic duct can also interfere with EUS exploration. The thickening of the bile duct wall after long-term placement of the stent in the biliary tract may make it difficult to distinguish between cholangiocarcinoma and thickening of inflammatory duct wall.