Brief Answer:
It might be due to over filled bladder or dynamic obstruction.

Detailed Answer:
Hello XXXXXXX

Pelvicalyceal system in the kidneys is the urine drainage system and it involves the renal pelvis and calyces.

Dilatation of the pelvicalyceal outflow systems in normal kidneys often revert to normal over the next few months as with the age advances.

Dilated or prominent Pelvicalyceal system may be due to many other reasons like over filled urinary bladder,recent passage of calculus,mild hydronephrosis etc.
Generally it is a benign finding.Patient may need repeat USG with empty urinary bladder.

However,it might indicate some form of obstruction to the flow of urine, and once the kidney starts enlarging in size, they indicate the probable permanent nature of the obstruction unless the problem is correctly located and taken care of.

In the case of your baby, dilatation has occurred in only left kidney.

Your doctor(paediatric surgeon) may suggest for a renal scan or urogram or intravenous pyelography(IVP) to detect the level of obstruction if any.

Most cases, the obstruction is "dynamic", which means there is no stone or any physical obstruction, but a spasm of the muscle of the ureter at the point where the pelvis of the kidney meets the calyceal system or where the calyceal system meets the start of the ureter.

It is good that rest of the findings are normal.Ureters appear normal.Peri renal areas normal, renal capsule normal. Cortical thickness, cortical echopattern and corticomedullary differentiations are normal. No calculus, no hydronephrosis or no mass lesions are seen.

Thanks and Regards,
Dr.SandipKabra

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