What Causes Stringy Blood In Stool After Gallbladder Removal?

my husband just had his gallblader taken 1/2 weeks ago and just today he went to the bathroom and pooped and had strings of blood in a peanut sized and i need to know if this is a gallstone passing his Dr said it would pass but i need to know if it could be more if he should go to hospital or if hes ok thank you