Patient: My son is one and a half years old, formula event checkup, found 1.1cm fluid in the left renal pelvis, half an hour after urination, recheck, the fluid disappeared, everything is normal. I would like to ask Prof. Huang to help me analyze what is going on in my son’s case and do I need surgery to treat it? Is the surgery complicated? Thank you! Huang Songming, Department of Nephrology, Nanjing Children’s Hospital: If the fluid disappears after urination, there are two possible causes: one is the reflux of the vesicoureter, that is, the urine may not flow downwards in one direction when it is discharged from the bladder, but may also reflux to the ureter or bladder above. The second is due to holding urine. That is, there is too much urine in the bladder, causing an increase in ureteral pressure and causing fluid in the renal pelvis, but this should occur bilaterally. We suggest that you review the ultrasound after some time, and keep an eye on your child for abnormalities in urination, such as frequent urination, poor urination and recurrent urinary tract infections. Pay attention to drinking water properly and urinating regularly. Patient: What auxiliary tests are needed to confirm whether it is reflux or not, and this kind of test has less side effects on the child, and also when is the right time to do the surgery and is it complicated? Huang Songming, Nephrology Department, Nanjing Children’s Hospital: It is far from surgery. The diagnosis of reflux should be done with a voiding urography examination.