S brown mostly black stool an adverse effct of 48hrs after endoscopy & flexsigmoidoscopy ? or side effect of med metronidazole and dexilant (dexlansoprazole)? shd i wry

Yes, time to worry: Dark-colored stools may result from iron supplements, foods you eat (like a lot of spinach), substances (like peptobismol), but most significantly suggests bleeding. When blood is denatured by acid in your stomach, as from ulcers, stools will turn tarry ("melena"). Blood may also be ingested from nose bleeds, bleeding gums... Persistent melena, particularly after a GI procedure, needs evaluation.