As per usual, start with the simple, easily available, and most non-invasive tests and take it from there. Urine should be checked for urinalysis, microscopy, C&S and a pregnancy test.
Blood should be drawn, U & E, FBC, Amylase, Muscle enzymes and Calcium checked.
Radiological investigations include; plain supine abdominal films, erect chest x-ray, CT scanning and contrast studies.