Congenital obstructive megaureter, hydronephrosis, with 2-3% semiannual hydronephrosis and dilatation of the ureter. The causes of ureteral dilatation are systematically analyzed: congenital obstructive megaureter; vesicoureteral reflux; i.e., no stenosis and no reflux (no functional abnormalities in the ureter other than morphological distention); due to other etiologies such as posterior ureteral valves (especially bilateral ureteral dilatation), neuronal bladder, dry plum belly syndrome, etc. The discussion here focuses on congenital obstructive megaureter, which results from narrowing at the interface between the bladder and ureter. Untreated or severe cases can cause ureteral dilatation, hydronephrosis, recurrent urinary tract infections, stones, and destruction of the kidneys. 1. Definition and symptoms To what extent does the ureter have to be dilated to be considered a giant ureter? From a newborn baby to a twelve-year-old child, the upper limit of the ureter is between 5mm and 6.5mm. Thus, giant ureters were defined as those with a diameter of 7mm or more. 2. Imaging (1) Ultrasound should be repeated after birth in all babies. A series of ultrasounds at different times are more meaningful. (2) Voiding cystourethrography: All boys should have a cystogram to rule out posterior urethral valves. All children with giant ureteral disease with hydronephrosis should also have a cystogram to rule out vesicoureteral reflux. This test is a little uncomfortable for the child. This involves inserting a small tube through the urethra, injecting some contrast into the bladder, removing the tube, and having the child urinate and take an x-ray. (3) Nuclear medicine nephrogram: If there is no posterior urethral valve or no vesicoureteral reflux, these children should have a and nephrogram. Those with ureters larger than 10 mm in diameter should also have a nuclear nephrogram to rule out obstruction of the vesicoureteral excuse. This test requires a microinjection of radioisotope from a vein. The isotope is absorbed by the kidney and then excreted. The amount of radiation is lower than an x-ray, so parents do not need to talk about “nuclear”. A nuclear nephrogram can measure both kidney function and the rate of isotope elimination to determine whether there is an obstruction. In a normal person, renal function is about 50% (45-55%) on each side. If the renal function on one side is below 40%, or if there is a 5% decrease from the previous function, it is indicative of obstruction. It is important to confirm the diagnosis before treatment. A child with ultrasound findings of ureteral and pelvic dilatation had four CTs and an MRI without a correct diagnosis. Following the above guidelines and examination system, the doctor performed excretory cystourethrography and nuclear medicine nephrography, which revealed a vesicoureteral reflux, no congenital obstructive megaureter, and no posterior urethral valves. 3. Treatment A ten-year follow-up study found that three-quarters (73%) of patients with giant ureter did not require any surgery, so today’s concept focuses on conservative treatment. Prenatal ultrasound reveals hydronephrosis, and prophylactic antibiotics are usually recommended for 6-12 months before the diagnosis is confirmed, because the results of the long term survey found that congenital obstructive giant ureter, tube causes urinary tract infections in many babies, and more than one third of the children have at least one hospital admission. In contrast, the use of prophylactic congestin during the first six months of life can reduce the infection rate by 83%. The indications for surgery are limited to the onset of clinical symptoms such as infection, stones and pain, or a decline in renal function, with unilateral renal function below 40%, a 5% decrease, or a worsening effusion. It is very important to keep track of these indications. (1) If the baby has complete ureteral obstruction, infection, or nontoxic disease, most doctors will use puncture nephrostomy for drainage. (2) Stent: Ureteral reimplantation is very difficult to do before one year of age in babies with ureteral obstruction. It is not easy to put a stent in a baby boy under two months old. This is because the urethra of a baby boy of this age cannot accommodate a cystoscope, guidewire and stent (double J tube) at the same time, but it can be done with a modified strategy. Placement of a stent is a common method of managing a giant ureter before the age of one year. The double J tube can be in the body for 2-6 months, but of course, the longer it is in place, the higher the chance of complications (infection, stones, stent migration) (up to 31%). The consensus of the British Pediatric Urology Group is that stenting is the preferred method of management in children under one year of age. (3) Balloon dilation of the stented segment. In Spain, the pediatric urologists in Barcelona have the most experience in this area, but only a few centers worldwide use this approach. (4) Ureteral reimplantation, in which the stenotic segment is removed and the ureter of the patent segment is anastomosed to the bladder (Cohen, Politano-Leadbitter et al). Although some doctors believe that this procedure can be done at any age, the opinion of most pediatric urologists is that it should be done after the age of one year. Because of the “giant” ureter, expert opinion varies as to whether the ureter should be thinned or folded (Kalicinski procedure) and then anastomosed. Direct anastomosis of the giant ureter relieves the obstruction, but there is some reflux. The success rate of ureteral reimplantation is between 94-96%. Most centers in the Western world do open surgery. Conclusion: Treatment of congenital obstructive giant ureter according to international standards gives the best protection of the kidney and minimizes complications.