Suggest Treatment For An Urinary Infection

hello doctor, i have six month old baby boy.we noticed that mild blood spot on the diaper with urine, not continuosly, sometimes two to three times in a day and again few days later( may after one or two week). Ultrasound abdomen findings: 1) The liver is of normal size & shape with smooth contour & normal homogenous echo texture. 2) The course & caliber of the common &Intra hepaticbiliary ducts are normal. 3) The gall bladder is adequately distended with normal wall thickness and no evidence of calculus or sludge. 4) Normal size & configuration of both kidneys with good cortical thickness.Mildly dilated left renal pelvis=5mm.No stones.Right kidney measures 5.5x2.4cm and left kidney 5.3x2.4cm. 5) The spleen has normal sonographic configuration. 6)No ascites or abdominal collections. 7) The pancreas was normal. Conclusion:: - Left renal pelviectasia. what it means sir? anything serious sir?need any further investigation sir? waiting for your valuable reply? faithfully stephen