For 8 weeks now dull ache on and below lowest left rib into left flank and lower left back. feels inflamed not sore to touch. worse w/activity and sitting. ruled out cardiac & gi issues other than mild gastritis. doc is stumped. any ideas?

Two other possibilities are left kidney pathology and a nerve root impingement by a bulging disc or spur in the upper lumbar or lower thoracic intervertebral space. A urinakysis with a micriscopic exam of the sediment &,an ultrasound of the kidneys first and, if normal, then an MRI of the lumbar& thoracic spine are studies that might be considered. Of course your MD would be best to advise you.