Assessment of pancreatic ductal stone density on computed tomography for predicting outcome of extracorporeal shock wave lithotripsy

Extraction of large pancreatic calculi is challenging for the endoscopist. Extracorporeal shockwave lithotripsy (ESWL) is an excellent tool for patients with large pancreatic calculi that are not amenable to routine endotherapy. Pancreatic calculi in the head and body are targeted by ESWL, with an aim to fragment them to < 3 mm diameter so that they can be extracted by subsequent endoscopic retrograde cholangiopancreatography (ERCP). Drainage of the main pancreatic duct (MPD) with ERCP alone is often unsuccessful; so, ESWL is used to fragment large pancreatic stones before ERCP.  After pulverization of the stones by ESWL, the fragmented stones can be retrieved endoscopically. Long-term follow up studies have shown that ESWL combined with endoscopic drainage of the pancreatic duct relieves pain and may avoid the need for surgery in approximately two-thirds of patients.  Some studies have suggested that breaking of stones to <2 mm in size by ESWL alone is effective in providing relief in pancreatic pain as these small stones are spontaneously cleared. Patients who cannot be managed endoscopically need to be treated surgically. However pancreatic surgery is associated with substantial morbidity (20-40%) and mortality (2-5%). ESWL has advantages over surgery viz. it is minimally invasive; there is usually no need for general anaesthesia and has low complications. Till date there has been just one study across the world which has looked for density of pancreatic ductal stones on imaging to predict outcomes for ESWL. Therefore this study is aimed to evaluate the outcome of ESWL based on computerized tomography characteristics for pancreatic ductal stones.