Small residual stones are not uncommon in cases of multiple calculi where small calculi embedded in or migrating in inaccessible calyceal areas of kidney are not visible by nephroscope or by fluoroscopy and later appear in follow up USG or follow up CT . Moreover recurrent small calculi or calcification can occur in multiple urolithiasis cases. Even after complete clearance ,good follow up with preventive medical therapy is advisable as recurrent small calculi can appear. Have   medical therapy with good follow up. Large calculi can be further removed by minimally invasive means if required