Does an ercp rule out cancer? Dr found stenosis put in stent then remvd week later. Still have mod to severe ruq pain x 3.5mo rad to back /wt loss.

ERCP. Ercp allows to take sample via brushing and biopsies. It is pretty accurate, however this should be combined with other imaging techniques, such as ct scan or MRI . As far as your persistent pain, i recommend you to report it to your doctor to rule out recurrence or other diagnosis.
No. Ercp can be used to diagnose cancer. But if symptoms persist and nothing found on ercp, further testing is warranted. Sometimes blind biopsies are needed if no specific mass is found. Tumor markers such as ca 19-9, cea, AFP may be helpful as well. Please speak to your doctor further. A repeat ERCP may be needed.