What Are The Indications For Endoscopic Ultrasound? Is That An

What are the indications for endoscopic ultrasound? Is that an integral part of an ERCP or can they be done separately? I have had an MRCP that was essentially negative, except the common duct could not be well identified. This was ordered as a result of reflux of cholangiogram dye into the pancreatic duct during laparoscopic cholecystectomy 6 weeks prior and a long history of gastrointestinal issues with spasm in this area on EGD. I have also been noted to have spasm in the small bowel making biopsy there impossible. Also have had a bacterial infection in my small bowel previously. Wonder what further diagnostic procedures would be helpful to diagnose the areas of spasm. Could this possibly be a sphincter of Oddi malfunction causing reflux and spasm in one or both of these areas?