Hello Doctor, Good Morning, I Have A Question For My

Hello Doctor, Good Morning, i have a question for my son who is aged 1.9 yrs. We did the ultra sound as my daughter had UTI (bilateral) and went over the surgery. As the doctor advised to check my son for any sign similar to that. As per the Ultrasound report as below. Let me know if there is anything to be worried about?

AN/SU
REAL TIME ULTRASONOGRAPHY OF THE ABDOMEN WAS PERFORMED
LIVER: Normal in size, shape and outline. Parenchymal texture normal. No focal cystic or solid mass lesion.
No intrahepatic biliary dilatation. Intrahepatic portion of IVC is normal. Portal vein is normal. Porta hepatis is
normal.
GALL BLADDER: Wall thickness normal. Luminal echoes are normal. No calculi.
C.B.D: Not dilated.
PANCREAS: Parenchymal texture normal. No ductal dilatation. No calculi.
SPLEEN: Meaures 7.1cm. Normal texture.
AORTA: Normal.
KIDNEYS: Normal in size, shape and outline. Parenchymal texture normal. Corticomedullary differentiation is
well made out and is normal. Sinus echoes are normal.
Right kidney measures 7.0cm with a parenchymal thickness of 0.8cm.
Left kidney measures 7.3cm with a parenchymal thickness of 0.9cm.
URINARY BLADDER: Wall thickness measures 2mm. Luminal echoes normal. No calculi.
Prevoid- 66cc Postvoid-17cc ( Significant)
PROSTATE: Normal for age.
No free fluid in peritoneal cavity.
IMPRESSION:
SIGNIFICANT POSTVOID RESIDUE.
NO OTHER SIGNIFICANT ABNORMALITY DETECTED.