Ultrasound Abdomen And Pelvis Report Shows Small Right Renal Concretion. What Does It Indicate?

I am 36 yrs woman, ultrasound:Abdomen & Pelvis report is 1`.Liver is normal in size and echopattern. Intra heptic biliary radicals not dilated. No focal lesion seen. Hepatic veins are normal 2.Gall Bladder: shows normal physiological distension, no stone could be seen.3. CBD not dilated. No stone could be seen in common bile duct. 4. Portal Vein & IVC are normal 5. Pancreas normal with echotexture, Pancreatic duct is not dilated. No focal lesion is seen.5.Spleen is normal in size & echopattern. No focal lesion seen 6.Both kidneys normal in size, position and echopattern. the corticomedullary, differentiation is well preserved . A 4.0 mm small concretions is noted in lower pole of right kidney7. Retroperitoneum normal 8.Urinary bladder normal in outline & distension 8.Utreum normal shape & shape & size with normal echopattern with normal thickness of endometrium Endometrial cavity is clear 9.Both ovaries normal in size shape and echopattern 10.No evidence of any adenexal mass. No ascitis/pelvic/pod collection seen. 11. Impression: SMALL REIGHT RENGAL CONCRETION. Kindly advise me . ARTI