Embryology
The ureteric buds form or sprout from the distal ends of the mesonephric ducts, before dividing to become to the renal pelvis and collecting system.
The distal ends of the ureteric buds and the mesonephric ducts both join to the urogenital sinus:
- The ureteric buds become the ureteric orifices – migrate cranially and laterally
- The ends of the mesonephric ducts migrate caudally and medially to become the ejaculatory ducts
Duplex ureters form from two ureteric buds arising from one mesonephric duct.
An accessory ureteric bud which arises cranially/higher on the mesonephric duct – which drains the upper moiety – will insert lower/caudally and medially
- May enter in a distally ectopic location – above the sphincter in males (but potentially into mesonephric remnants) but may be below the sphincter in girls
- Mesonephric (Wolffian) remnants in girls – Gartner duct cysts – may be ectopic location
- May drain ectopically into vas in men as Mesonephric (Wolffian) remnants
An accessory ureteric bud arising lower/distally on the mesonephric duct – draining the lower moiety – will insert cranially/higher and laterally.
Incidence – duplex kidneys
0.8 % (1 in 125) some degree of ureteric duplication. Majority incomplete above ureteric orifice.
Complete duplication 0.1 % (1 in 1000).
Strong genetic pre-disposition.
Female > male.
May be bilateral in up to 40 %.
Pathology
Upper pole frequently has less parenchyma (1/3 cf. 2/3 lower third).
Lower pole moiety
50 % will be associated with reflux – arises low on the mesonephric duct and incorporated into bladder prematurely – undeveloped intramural tunnel
Upper pole moiety
Often dilated and appears obstructed, with dysplastic upper moiety parenchyma
Associated with ureterocele.
Ectopic ureter (0.01 % population) – always above level of sphincter in boys, but may be infrasphincteric in girls opening into introitus or perineum
Weigert and Meyer did a bit of work with duplex ureters:
- The lower pole ureter will be cranial and lateral in the bladder
- A very abnormal lower pole ureter may result from ureteric bud arising too low on the mesonephric duct, resulting in premature incorporation into bladder
- Therefore it may have an undeveloped intramural tunnel, leading to reflux
- The upper pole ureter will be caudal and medial
- A very abnormal upper pole ureter may have its ureteric bud arising too high on the mesonephric duct
- May drain into bladder neck or verumontanum in males (always proximal to sphincter), or even rarely into the mesonephric duct derivatives (namely vas deferens) – this abnormal insertion associated with obstruction
- In females, may also drain into mesonephric duct remnants (namely Gartner’s duct), or into the vaginal vestibule
Ectopic ureter / ureterocele
Ureterocele defined as cystic dilation of the terminal intravesical segment of a ureter
Ectopic ureter – any ureter that does not enter the trigonal area of the bladder
Much more common in females. 1/1000 incidence.
Embryology – failure of regression of Chwalla membrane between ureteric bud / urogenital sinus.
80 % of ureteroceles associated with duplex ureters.
- Classify as intravesical/extravesical; orthotopic/ectopic; single/duplex; unilateral/bilateral; symptomatic/asymptomatic;
- If opening at bladder neck etc can cause bladder outlet obstruction.
Most often identified antenatally on ultrasound.
- Other presentations – bladder outlet obstruction, UTIs, prolapse of ureterocele, incontinence in girls despite normal voids, incidental finding, epididymo-orchitis in boys opening to vas/SVs
Ureterocele / ectopic work-up
Examination – other issues, development, occasionally visible leaking or ectopic orifice or prolapsing ureterocele identified.
Ultrasound – ?bilateral involvement, degree of dilation, parenchyma, duplex
- Classic finding is upper pole dilation
Urine culture
MCUG – ?is there reflux. Might see filling defect of ureterocele.
DMSA or MAG3 – function +/- obstruction – of kidneys and individual moieties
Clarify anatomy – MR urogram, CT urogram, IVP
Downward, lateral displacement of lower pole = drooping lily sign
Endoscopic assessment + EUA (often combined with treatment)
Management
Goals of management:
- Preservation of renal function
- Prevent or eliminate infection
- Treat obstruction and reflux
- Maintain or improve continence
- With least morbidity and minimise bladder dysfunction
Prophylactic antibiotics for children with hydronephrosis.
Treatment options:
- Expectant management / observation
- Endoscopic incision of ureterocele
- If upper pole is dysplastic, damage likely already done (i.e. wont recover but will may prevent further deterioration)
- May unmask more reflux – 50 % post decompression
- Endoscopic management of reflux (Deflux)
- Heminephrectomy / resection of non functioning (usually upper) pole
- Good for ectopic ureter causing incontinence (although ?simple laparoscopic ligation of ureter now used)
- Conjoined ureteric reimplantation (good if duplex lower moiety is refluxing)
- Pyelopyelostomy – rare, only if useful upper pole function
- “Total reconstruction”
- Upper pole heminephrectomy, excision of ureterocele, and reimplant of refluxing lower pole ureter