This is a medical question of type : exams and tests 
 How to diagnose Urine Blockage in Newborns ? 
 Defects of the urinary tract may be diagnosed before or after the baby is born.
                
Diagnosis before Birth
                
Tests during pregnancy can help determine if the baby is developing normally in the womb.
                
- Ultrasound. Ultrasound uses a device, called a transducer, that bounces safe, painless sound waves off organs to create an image of their structure. A prenatal ultrasound can show internal organs within the baby. The procedure is performed in a health care providers office, outpatient center, or hospital by a specially trained technician, and the images are interpreted by     - a radiologista doctor who specializes in medical imaging, or    - an obstetriciana doctor who delivers babies
                
The images can show enlarged kidneys, ureters, or bladders in babies.
                
- Amniocentesis. Amniocentesis is a procedure in which amniotic fluid is removed from the mothers womb for testing. The procedure can be performed in the health care providers office, and local anesthetic may be used. The health care provider inserts a thin needle through the abdomen into the uterus to obtain a small amount of amniotic fluid. Cells from the fluid are grown in a lab and then analyzed. The health care provider usually uses ultrasound to find the exact location of the baby. The test can show whether the baby has certain birth defects and how well the babys lungs are developing.  - Chorionic villus sampling (CVS). CVS is the removal of a small piece of tissue from the placenta for testing. The procedure can be performed in the health care providers office; anesthesia is not needed. The health care provider uses ultrasound to guide a thin tube or needle through the vagina or abdomen into the placenta. Cells are removed from the placenta and then analyzed. The test can show whether the baby has certain genetic defects.
                
Most healthy women do not need all of these tests. Ultrasound exams during pregnancy are routine. Amniocentesis and CVS are recommended only when a risk of genetic problems exists because of family history or a problem is detected during an ultrasound. Amniocentesis and CVS carry a slight risk of harming the baby and mother or ending the pregnancy in miscarriage, so the risks should be carefully considered.
                
Diagnosis after Birth
                
Different imaging techniques can be used in infants and children to determine the cause of urine blockage.
                
- Ultrasound. Ultrasound can be used to view the childs urinary tract. For infants, the image is clearer than could be achieved while the baby was in the womb.  - Voiding cystourethrogram (VCUG). VCUG is an x-ray image of the bladder and urethra taken while the bladder is full and during urination, also called voiding. The procedure is performed in an outpatient center or hospital by an x-ray technician supervised by a radiologist, who then interprets the images. While anesthesia is not needed, sedation may be used for some children. The bladder and urethra are filled with a special dye, called contrast medium, to make the structures clearly visible on the x-ray images. The x-ray machine captures images of the contrast medium while the bladder is full and when the child urinates. The test can show reflux or blockage of the bladder due to an obstruction, such as PUV.  - Radionuclide scan. A radionuclide scan is an imaging technique that detects small amounts of radiation after a person is injected with radioactive chemicals. The dose of the radioactive chemicals is small; therefore, the risk of causing damage to cells is low. Radionuclide scans are performed in an outpatient center or hospital by a specially trained technician, and the images are interpreted by a radiologist. Anesthesia is not needed. Special cameras and computers are used to create images of the radioactive chemicals as they pass through the kidneys. Radioactive chemicals injected into the blood can provide information about kidney function.