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Invasive and interventional uses of endoscopic ultrasound

Radiology Department, John Radcliffe Hospital, Oxford, UK

Correspondence: Dr Jane Phillips-Hughes, Department of Clinical Radiology, John Radcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU, UK. E-mail: jane.phillips-hughes{at}orh.nhs.uk

	Introduction

Top Introduction Biopsy Pseudocyst drainage Biliary procedures Coeliac plexus block References

 
Endoscopic ultrasound (EUS) was introduced in the 1980s primarily for the local staging of gastrointestinal (GI) malignancy, and for which it now has an established role in upper GI, pancreatic and rectal cancers.

EUS T-staging in oesophageal cancer (which assesses the extent of tumour invasion into/through the oesophageal wall) is said to have accuracies in the region of 80–90%, with lymph node (N) staging accuracy of 75% [1]. Hence diagnostic EUS complements other imaging modalities such as CT and MRI, and features regularly in multidisciplinary meetings for upper GI and pancreatic cancers.

It is also used in biliary disorders; for example, the demonstration of microlithiasis and choledocholithiasis.

However, it is the interventional capability of EUS which is perhaps likely to see the most growth in the next decade.

When first introduced, the prototype mechanical sector scanning endoscopes had only 180° images. 360° imaging became possible when Olympus (Tokyo, Japan) introduced the GF-UM3 and a number of electronic radial scanning endoscopes are now available for diagnostic work.

Around 1990, the Pentax Corporation (Tokyo, Japan) developed an electronic convex curved linear-array scope – the FG32UA. This echoendoscope had a 2 mm working channel overlapping the imaging plane which allowed fine needle aspiration biopsy. Subsequently, Pentax-Hitachi have developed instruments with a 180° imaging field that have 3.2 mm and 3.8 mm working channels which allow introduction of 8.5 F and 10 F devices, respectively. Olympus in conjunction with Aloka have introduced linear echoendoscopes with 7 F and 10 F working channels.

Thus EUS guided biopsy and drainage is available and a plethora of papers on EUS in general, but also invasive/interventional EUS in particular, has appeared in the literature in recent years [2].

The proximity of mediastinal structures, the pancreas, adrenal glands and the hepatobiliary system to the luminal GI tract gives the operator access to all of these areas, and hence allows procedures which impact on several different organ systems.

The following is a brief outline of the range of interventional/therapeutic procedures which can be performed.

	Biopsy

Top Introduction Biopsy Pseudocyst drainage Biliary procedures Coeliac plexus block References

 
Lymph node staging remains a problem for all imaging modalities.

The accuracy of lymph node (N) staging in GI cancers can be improved by biopsy of questionable perigastrointestinal nodes visualized at EUS, either by fine needle aspiration (FNA) or core biopsy.

In addition to staging of GI and pancreatic cancers, EUS FNA may be used in lung cancer. Nodes in the posterior mediastinum, aortopulmonary window and subcarinal region can be sampled with a quoted sensitivity of 90% and specificity of 83–100% [3]. Some would advocate EUS ± FNA in the staging of all potentially operable patients with non-small cell lung cancer [4]. Whilst this is not currently the norm in the UK, it is already used in selected cases in a number of centres, and this may well increase as the exact role of EUS FNA alongside PET-CT becomes established.

EUS FNA is not restricted to lymph nodes, however, and has been used in numerous other situations, e.g. submucosal GI tumours, adrenal lesions and pancreatic masses in particular. The reduced risk with regard to transcoelomic seeding is a further advantage in comparison with percutaneous biopsy.

Diagnostic accuracies of 70–90% are quoted. This may be improved by combining EUS FNA with EUS guided core biopsy with a 19 gauge trucut needle [5]. With core biopsies also available, the scope for evaluating certain tumours such as lymphoma may also be improved.

	Pseudocyst drainage

Top Introduction Biopsy Pseudocyst drainage Biliary procedures Coeliac plexus block References

 
Whilst non-ultrasound guided endoscopic drainage of pancreatic pseudocysts has long been accepted as an alternative to a surgical approach, it carries risks of haemorrhage and perforation as the puncture is essentially blind to structures deep to the gastric or duodenal lumen.

Using EUS to guide the drainage of a pancreatic pseudocyst is an attractive option as an appropriate puncture site can be chosen, avoiding major blood vessels and using the most direct track between GI lumen and pseudocyst.

Insertion of a nasocystic catheter or stents, either single or multiple, are reported to have high success and low complication rates [6].

More aggressive approaches with serial dilatation of the puncture to enlarge the cystogastrostomy and allow insertion of an endoscope into the cavity to facilitate removal of more viscous debris are also being developed. Indeed, such techniques are also beginning to be applied to perioesophageal mediastinal collections and abscesses [7].

	Biliary procedures

Top Introduction Biopsy Pseudocyst drainage Biliary procedures Coeliac plexus block References

 
EUS guided common bile duct (CBD) puncture allows drainage of the biliary system when the bile duct is inaccessible by a conventional ERCP approach [8]. This approach may have advantages over percutaneous transhepatic cholangiography (PTC), particularly in cases of impacted bile duct stones and distal CBD strictures, although it's exact role alongside PTC has yet to be established.

	Coeliac plexus block

Top Introduction Biopsy Pseudocyst drainage Biliary procedures Coeliac plexus block References

 
The proximity of the coeliac axis to the gastric wall makes EUS guided coeliac plexus neurolysis another therapeutic option. Puncture and injection of neurolytics (such as a mixture of local anaesthetic and alcohol) into the area immediately above and alongside the origin of the coeliac axis can readily be performed under ultrasound guidance.

The route is more direct and the risk of complications such as paraplegia is theoretically much lower than for the conventional percutaneous approach, and encouraging results with significant reduction of pain for the patients with pancreatic cancer have been reported [3]. The procedure may also prove useful in chronic pancreatitis, with a steroid such as triamcinolone used in place of alcohol.

In summary both diagnostic and interventional EUS are likely to grow over the next decade as equipment and expertise becomes more widely available, and as techniques are developed and refined. There are already reports of EUS guided targeted delivery of immunotherapy into unresectable pancreatic tumours, plus EUS guided radiofrequency ablation of pancreatic tissue in a porcine model. In addition, EUS guided delivery of high-intensity focused ultrasound and radiation therapy are being evaluated [3].

Currently, the UK lags behind much of continental Europe, Japan and the USA where EUS services are already well developed, so there is likely to be some catch-up occurring over the next decade. EUS is currently performed by surgeons, gastroenterologists and radiologists. The issue of who performs EUS is less important than the issue of training. Expertise in both endoscopy and ultrasound is necessary, and the British Society of Gastroenterology is in the process of establishing guidelines on this subject. However, no matter who performs EUS, this technique is here to stay, and is likely to become an integral part in both the investigation and treatment of patients in the future.

Thus, radiologists should be aware of EUS as it is an imaging technique which complements as well as competes with other more conventional radiological tools, and if it hasn't arrived already – it may well be coming soon, to a hospital near you.

Received for publication June 6, 2006. Revision received August 15, 2006. Accepted for publication August 25, 2006.

	References

Top Introduction Biopsy Pseudocyst drainage Biliary procedures Coeliac plexus block References

 

1. Ingram M, Arregui ME. Endoscopic ultrasonography. Surg Clin N Am 2004;84:1035–59.
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5. Wittmann J, Kocjan G, Sgouros SN, Deheragoda M, Pereira SP. Endoscopic ultrasound-guided tissue sampling by combined fine needle aspiration and trucut needle biopsy: a prospective study. Cytopathology 2006;17:27–33.[Medline]
6. Giovannini M, Binmoeller K, Seifert H. Endoscopic ultrasound-guided cystogastrostomy. Endoscopy 2003;35:239–45.[CrossRef][Medline]
7. Wehrmann T, Stergiou N, Vogel B, Riphaus A, Kockerling F, Frenz MB. Endoscopic debridement of paraesophageal, mediastinal abscesses: a prospective case series. Gastrointest Endosc 2005;62:344–9.[CrossRef][Medline]
8. Puspok A, Lomoschitz F, Dejaco C, Hejna M, Sautner T, Gangl A. Endoscopic ultrasound guided therapy of benign and malignant biliary obstruction: a case series. Am J Gastroenterol 2005;100:1743–7.[CrossRef][Medline]

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