Why Does the Four-Dimensional Ultrasound Show Bilateral Renal Pelvis Separation?

Four-dimensional ultrasonography showing fetal renal pelvis separation refers to the accumulation of urine in the fetal kidneys, which in the worst case may lead to fetal hydronephrosis. Renal pelvis separation is medically referred to as pyelodilation. The renal pelvis is the connection between the kidney and the ureter. Pyelodilation and separation occur when factors such as kidney stones or ureter malformations prevent urine from being expelled normally, causing it to accumulate in the renal pelvis and enlarge it. The normal range for renal pelvis separation is 0-10mm. Typically, normal adult renal pelvis separation within 10mm is considered normal, but it is more uncertain for fetuses. Generally, renal pelvis separation within 4mm is considered normal for fetuses. For instance, a B-ultrasound scan revealing renal pelvis separation of 5mm in a patient is typically monitored during pregnancy. Generally, renal pelvis separation not exceeding 10mm is considered within the normal range. Renal pelvis separation observed on four-dimensional ultrasonography can be classified as mild or severe, with mild separation being ≤7mm and severe separation being ≥10mm. Besides understanding the width of renal pelvis separation, it is also important to assess the fullness of the fetal bladder. If the bladder is full, a follow-up examination should be performed after the fetus urinates. Pregnant women must undergo regular prenatal checkups and avoid excessive anxiety, which is not conducive to fetal development.