Double ureters

　　1. Embryogenesis:During the fourth week of embryogenesis, the ureteric bud rapidly grows, with its proximal part forming the ureter and its distal part covered by the primitive renal tissue mass, which develops into the renal pelvis, calyces, and collecting tubules. If the distal branches of the ureter exceed two, a duplicated renal pelvis is formed; if branching occurs prematurely, an incomplete double ureter is formed, with the ureter taking a Y shape. In addition, if another ureteric bud (or accessory ureteric bud) grows at the lower end of the mesonephros, it rises in parallel with the normal ureteric bud, complete double ureteral anomalies occur.

　　2. Genetics:Double ureters may be autosomal dominant inherited with incomplete penetrance. The incidence of double ureters in families surveyed ranges from 1 in every 125 people to 1 in every 8 to 9 people. Environmental factors affect the occurrence of double ureters.

　　One-third of the renal parenchyma is drained by the upper collecting system. Those with a single renal system have an average of 9.4 minor calyces, while those with a duplicated kidney have 11.3 minor calyces. On average, the upper pole has 3.7 minor calyces, and the lower pole has 7.6 calyces (Privett et al., 1976). Ninety-seven percent of kidneys with a single collecting system are normal on imaging, while 29% of those with duplicated anomalies have scars and/or dilatation. In cases of excretory urography, reflux is common in those with duplicated anomalies, accounting for 42%, while only 12% of those without duplicated anomalies have reflux. The lower pole often has hydronephrosis due to concurrent reflux, but there are also cases of obstruction at the renal pelvis-ureteral junction. There are also many other associated anomalies, with 27 cases (12%) in the Nation group having other urinary system anomalies, including renal hypoplasia or dysplasia and various types of ureteral anomalies, including 4 cases of ectopic upper ureteral orifices (accounting for 3% of complete ureters). In the Campbell group, 129 of the 342 cases with double ureters had associated urinary system anomalies, while 63 had no urinary system anomalies. The types of urinary system anomalies are also similar to those in the Nation group, with 22 cases having contralateral renal anomalies.

　　Clinical symptoms vary greatly with gender. Due to embryological differences, male ectopic ureters mostly open at the bladder neck, prostate, seminal vesicle, epididymis, and vas deferens, all located above the external urethral sphincter, so they are generally manifested as symptoms of urinary tract infection, such as constipation, postpubic pain, seminal emission discomfort, etc., and may also be accompanied by urgency and frequency of urination. Occasionally, infertility is seen, but urinary incontinence is rare. For women, the most common opening site is the vestibule, and it can also be located in the upper segment of the vagina, uterus, and ovary. Since the ectopic opening is often located at the distal end of the external urethral sphincter, it often manifests as persistent urinary incontinence after normal urination. Another characteristic of the opening of the female ectopic ureter is the persistent vaginal discharge. Most female patients have acute and chronic urinary tract infections, a few show renal pelvis and ureteral hydronephrosis, and occasionally, patients present with abdominal masses. About 60% of the cases have no obvious symptoms, although urinary tract infection is not a unique feature of double ureters, but recurrent urinary tract infections should consider the possibility of double ureters. A diagnosis can be made by combining intravenous urography and cystoscopy.

     Double ureters may be an autosomal dominant genetic disorder with incomplete penetrance. If there are no effective preventive measures for double ureters at present, early detection and early diagnosis are the key to the prevention and treatment of this disease.

　　The diagnosis mainly relies on intravenous urography and cystoscopy. It is advocated to use a high-dose intravenous infusion of urography, where children can directly inject the contrast agent into the vein with a syringe to control the injection time. The high-dose intravenous infusion method can do without abdominal pressure band, and is more satisfactory for displaying the entire course of the ureter.

　　If the functional existence of the upper renal segment of the duplicated kidney is present, the X-ray angiography can clearly show the full view of the畸形. The higher the confluence point of the two ureters, the clearer the display; if the confluence point is too low, it is often poorly displayed, and sometimes it is difficult to distinguish whether the duplicated ureters are complete or incomplete. If the function of the upper renal segment is poor, a follow-up film should be taken, and even some may need to be extended to 24 hours. If the function of the upper renal segment is almost completely lost, it should be carefully noticed and analyzed the shape of the renal pelvis and calyx of the lower renal segment. Generally, the upper renal calyx is absent, the inclination of the renal pelvis is increased, resembling a drooping flower, and it is far from the edge of the vertebral body; the ureter of the lower renal segment is often pushed outward or inward by the expanded and twisted ureter of the upper renal segment, sometimes showing a 'S' shaped curvature as it descends. In cases where the upper renal segment is functionless, the lower renal segment is much smaller in shadow than a normal kidney (contralateral), and sometimes it may be misdiagnosed as a small kidney畸形 or renal hypoplasia. Sometimes, in the follow-up film, the phenomenon of ureter-ureter reflux can be seen.

　　If two or more ureteral orifices are found during cystoscopy, the diagnosis of duplicated ureteral anomaly can be established. If it is possible to insert a ureteral catheter for retrograde imaging, the diagnosis will be more clear. Of course, if there are only two ureteral orifices at the bladder triangle, it cannot be completely excluded that there is a duplicated ureteral anomaly, because incomplete duplicated ureteral anomalies, ureteral orifices can be normal; in addition, one ureteral orifice may be ectopic, but it is not necessarily opening into the bladder. Sometimes, retrograde urography may find that one of the double ureters has a reflux phenomenon, and combined with intravenous urography, it can explain the location of the problem.

 Patients with this disease should pay attention to light diet, especially after surgery. Patients should always ensure adequate nutrition and try to stay away from spicy and stimulating foods. For patients with special requirements, it is recommended to follow the doctor's advice on diet.

　　Patients with bilateral ureteral anomalies without symptoms such as urinary tract infection, obstruction, or slight urinary incontinence, and without serious complications such as severe hydronephrosis, reflux, and stones, do not require treatment. Clinically, such cases account for about half of the total. The principles of surgical treatment usually include the following 3 points.

　　1. Incomplete Duplicated Ureter

　　For patients with incomplete duplicated ureter and ureteroureteral reflux.

　　1. The confluence of the duplicated ureter is located in the upper 1/3, perform a longitudinal ureteral side-to-side anastomosis.

　　2. The confluence of the duplicated ureter is located in the lower 1/3, perform the upper renal segment ureterovesical reimplantation.

　　2. Complete Duplicated Ureter

　　For patients with complete duplicated ureter and vesicoureteral reflux, perform ureterovesical reimplantation and add anti-reflux surgery.

　　3. Partial Nephrectomy

　　For those with uncontrollable urinary tract infections, or with slight urinary incontinence (with ectopic opening), or whose upper renal segment function has basically been lost, partial resection of the upper renal segment can be performed. The ureter can be cut near the confluence (incomplete duplicated ureter) or at the lowest level, or a total ureterectomy can be performed (complete duplicated ureter).