Extra-corporeal shock wave lithotripsy in chronic pancreatitis

Shankar Zanwar

Pancreatic stones and effects Pancreatic duct stones are found in approximately 22-60% of patients

with CP. Drake DH, SurgeryLarge stones

Obstruction of the PD

Increased intraductal

pressure

Tissue ischemia and hypertension

Pain

Principle of ESWL

ESWL works by producing shockwaves from external source focused on a target in the body.

Shock waves focused on stone, build in strength that cause fragmentation.

ESWL was introduced in 1980s treatment of renal calculi and subsequently used for pancreatic and biliary calculus treatment

Lithotripter's

Three methods of shock wave generation(SW) Spark discharge – Dornier system Piezoelectric elements – Wolf system Electromagnetic deflection of the metal membrane – Siemens system

SW generation occurs in degased water

SW focused by reflection of primary wave using hemispherical disc or an acoustic lens

SW delivery in the body using water cushion or water basin

Patient selection

Indication - in patients with all of the following Recurrent attacks of pancreatic pain Moderate to marked changes in the pancreatic ductal system Obstructing ductal stones

Almost all amenable to lithotripsy – since 95% are composed of calcium carbonate on a protein matrix

Contraindication Coagulation disorders Pregnant women Patients with pacemakers Calcified aneurysms Lung tissue in the path of SW

Methods – Localization

Left and right oblique plain X-rays MRCP (+/- secretin injection) If not available – CT abdomen Intra-procedural imaging US or fluoroscopy

Monitoring was successful in only 14 % of US localization – insufficiently precise Schneider – Am J GE 1994

US better mode of localization if PD dilated

Sedation and antibiotics

Conscious sedation Epidural anesthesia General anesthesia GA more useful when ERCP planned in same session.

Antibiotics recommended if ERCP concomitant

AIG protocol Large calculi in PD >5mm Aim to break to size less than 3mm Avoided

in patients with extensive calculi all over the pancreas Head mass Multiple strictures Pancreatic ascites Isolated calculi in tail area

Application of shock waves

Position : Such that stone is not overlying the spine - right or left lateral decubitus

SWs focused on the most distally located stones first

A total of 3000-5000 SWs are delivered in one session, typical session lasting 45-60mintues

Energy levels used highest upto –0.54mJ/mm2

When concurrent ERCP planned energy level – 0.33 – 0.37mJ/mm2 - avoids duodenal edema.

A caution should be exercised in patient with ventricular extra-systole patients, SWs should delivered only in the refractory period to avoid possible ventricular arrhythmia

Repeat session may be needed if large or multiple stones.

Reported number of session required vary in different studies, mean 5 (range 1-29)

Role of additional ERCP

Various series have reported differently

Japanese series – 24/32(75%) spontaneous stone clearance after 1 or 2 sessions of ESWL alone

Ohara Am J GE 1996

High success rate here was skewed due to selection of patient without severe MPD stricture and good exocrine function

Thus ESWL can be tried alone when there is no associated stricture in the MPD.

In RCT by Costamagna et al, ESWL with ESWL and ERCP combined Pain relief similar in both arms, Rx cost increased 3X

Gut April 2007

Many series have advocated use of sphincterotomy antecedent to ESWL and endoscopic clearance of stones.

But none in RCTs

In series of 48 patients Soehendra et al showed 45% patient had complete pain relief from symptoms when two procedures were combined

This series selected patients with stricture in PDAm J GE 2000

If at all ERCP is planned stone extraction - mini Dormia basket

A 6 Fr naso-pancreatic catheter is left in place for 1-2 days and perfused with NS – 1 liter over 24 hour to eliminate stone fragments

If strictures encountered stents can be placed across in the same sitting.

Efficacy of ESWL

ESWL permits better stone clearance than traditional endoscopic procedures

Multicenter study with 555 patient under going ESWL showed Fragmentation in – 92% Stone clearance (+/- ERCP) – 72% Symptom relief - 91% Recurrence(mean follow-up of 44 month) – 22%

Miyagawa, Pancreas 2005

Technical success

Disintegration considered successful when on plain X-ray Decrease density of stone Increase stone surface area Powdery appearance of stone

These accompanied by successful deep cannulation of MPD

Using these definition success rate of fragmentation is 74-100% (across several series)

But in most reports number and size of stone did not correlate with the success of fragmentation.

GI endoscopy Schneider 2002

Decompression of PD is obtained in 70-96% of patients with ESWL followed by endoscopic drainage

Disappearance of communicating cyst and pseudocysts is seen in 74% of these cases

J of GE and Hep, N Reddy 2006

Clinical results Pain relief

Radiologic success correlates with clinical improvement

Immediate pain relief or improvement was a/w successful decompression of PD.

However complete stone clearance is not required for symptom relief

A considerable increase in wt. gain - decrease in post prandial attacks, improved pancreatic function

Pain relapse factors

Alcohol and smoking increased chances of relapse

High frequency of pain attacks before treatment (>2 attacks/month)

Longer duration of illness

Nonpapillary stenosis of PD

Exocrine and endocrine functions

Early ductal decompression may prevent further fibrosis and thus pancreatic insufficiency.

Long term studies have shown endoscopic ductal drainage can delay development of exocrine insufficiency by about 10 years

By contrast onset of DM can not changed by interventions.

Stone recurrence

Recurrence of pain in most studies was related to recurrence of stones, progressive stricturing of MPD or PD stent obstruction or migration.

In a representative series, stone recurrence developed in 22% with mean time to recurrence – 25 months.

Presence of ductal strictures increased chance of recurrence.Miyagawa, Pancreas 2005

In long term follow up study 1/3rd had relapses over a mean follow – up period of 77 months.

Significantly more when incomplete clearance after initial therapy – HR of 3.7 MPD stricture – HR of 3.4

Clinical GE and Hep, Nakamura 2005

Need for surgery

Pancreatic surgery is required in 1.4-20% of patients Technical failure of stone disintegration Failure of endoscopic ductal drainage Complications of pancreatitis beyond the capability of endoscopic

management. As definitive treatment for biliary drainage (H-J) or pancreatic drainage(P-J)

Complications of ESWL

Noted complications of ESWL Common and mild

Petechiae around area of penetration of SWs Erosions in the gastric antrum at times hemorrhagic

Perirenal hematoma Biliary obstruction Bowel perforation Splenic rupture Lung trauma Necrotising pancreatitis

Summary

ESWL can be 1st line Rx for painful CCP – a/w obstructive ductal calculi leading upstream dilatation – Grade 2B

Best fragmentation rates are obtained when fluoroscopic targeting system used to focus stones

Summary

As general rule endotherapy should be used after ESWL for drainage of calculi in case of strictures in PD – but case based discretion needed

Definitive pain relief can be expected for long term in 2/3 of patients

Best results obtained in non smokers and when ESWL offered early in the course of disease.

Thank you