(1)
Pediatric Surgery, AlSadik Hospital, Qatif, Saudi Arabia
Congenital Ureteral Anomalies
Ectopic ureter
Ureterocele
Mega ureter
Vesicoureteral reflux (VUR)
The outcome of ureteral anomalies chiefly depends on the presence or absence of obstruction and/or infection, and associated renal injury.
In the absence of these, no treatment may be necessary, especially in the case of:
Isolated ureteral duplication anomalies
Low-grade VUR
A small orthotopic ureterocele
A nonobstructed, nonrefluxing primary mega ureter
6.1 Etiology
The ureter develops around the fourth and sixth week of gestation.
The ureter develops from a ureteral bud, the early precursor of the ureter, branches off from the caudal portion of the Wolffian (mesonephric) duct.
The ureter grows cranially and caudally.
The cranial portion of the ureteral bud joins with the metanephric blastema and begins to induce nephron formation.
The bud subsequently branches into the renal pelvis and the calyces and induces nephron formation.
The caudal portion of the ureteral bud along with the mesonephric duct are incorporated into the cloaca as it forms the bladder trigone.
Ureteral anomalies develops as a result of alterations in:
Ureteral bud number
Ureteral bud position
Time of ureteral development
Incomplete (partial) ureteral duplication, with a single ureteral orifice and bifid proximal ureters:
This results from early branching of a single ureteral bud
Complete ureteral duplication:
This results from an accessory ureteral bud.
Complete duplication occurs when two separate ureteric buds arise from a single Wolffian duct.
According to the Weigert-Meyer rule, the future lower pole ureter separates from Wolffian duct earlier and thus migrates superiorly and laterally as the urogenital sinus grows.
The result is complete duplication, with the upper ureter usually protruding into the bladder more medially and inferiorly than the lower ureter.
Ectopic termination of a single system or of the ureter of a duplex system is the result of the high (cranial) origin of the ureteral bud from the mesonephric duct.
Ectopic ureter:
This results from delayed incorporation of the ureteral bud into the bladder.
The resulting position of the ureteral orifice is more caudal and medial or in more severe cases it inserts into one of the Wolffian duct structures.
The ureters are paired muscular tubes that run from the renal pelvis to the bladder.
The ureters run through three natural areas of narrowing:
The ureteropelvic junction
The crossing of the iliac vessels
The ureterovesical junction (UVJ)
The UVJ may be divided into three sections:
The terminal portion (juxta vesical ureter)
The intramural portion
The submucosal portion (under the bladder mucosa).
The function of the ureter is to effectively transport the urinary bolus from the minor calyces to the urinary bladder at acceptably low pressures.
The efficiency of this function depends on adequate coaptation of the ureteral wall to propel the urinary bolus.
If the ureter fails to propagate the peristaltic wave, the static urine distends the upper urinary tract and reduces luminal coaptation.
Other factors that may affect ureteral transport include urinary volume and bladder pressure.
6.2 Clinical Features
The clinical presentations of ureteral anomalies are variable and the majority are asymptomatic.
There are no specific clinical signs associated with ureteral anomalies.
The diagnosis is sometimes suspected on routine prenatal ultrasound.
Some patients present with UTI, abdominal mass or hematuria.
Children with primary mega ureters may also present with cyclic abdominal pain/flank pain, or, less commonly, acute pain crisis.
Patients may present with a cystic mass at the urethral meatus representing a prolapsed ureterocele.
In other patients, the diagnosis is incidental after imaging studies for unrelated symptomatology.
Ureteral anomalies may be discovered during the evaluation of a patient with:
Hypertension
Proteinuria
Renal insufficiency in rare cases of severe bilateral anomalies
Approximately 50 % of females with ectopic ureters present with constant urinary incontinence or vaginal discharge.
In males, incontinence is never due to an ectopic ureter because the ectopic ureter never inserts distal to the external urethral sphincter.
Rarely, an ectopic ureteral insertion may present with recurrent epididymitis in pepubertal boys.
Post pubertal males with ectopic ureters most commonly present with chronic prostatitis and painful intercourse and ejaculation.
6.3 Investigations and Diagnosis
Urinalysis and urine culture are important in children presenting with unexplained fever.
The diagnosis of UTI should prompt further radiological evaluation to identify urological anomalies.
Renal and bladder ultrasound:
This is a first-line imaging study to evaluate the upper and lower urinary tract.
Ultrasound evaluation of upper urinary tract anomalies include ureteral duplication, dilatation of collecting system, character and thickness of the renal parenchyma.
Ultrasound evaluation of lower urinary tract anomalies include bladder wall thickness, ureterocele, bladder diverticulum, posterior urethral dilatation, and degree of bladder emptying.
Voiding cystourethrogram (VCUG):
This is valuable for evaluation of the bladder and urethra.
This includes evaluation of:
VUR
Bladder diverticulum
Ureterocele
Bladder trabeculations and bladder emptying
Urethral anatomy during voiding
The ureters if VUR is present
Diuretic nuclear renography:
This is an excellent study to evaluate:
The differential renal function
Cortical scars
Drainage efficiency of the dilated collecting system based on washout times
Intravenous pyelogram (IVP):
This study has been largely replaced by ultrasound and nuclear renography.
IVP delineates anatomy of the kidney, collecting system, ureter and urinary bladder.
It also provides subjective estimation of relative renal function.
MR urography (MRU):
This provides excellent anatomic and functional evaluation of the renal parenchyma, collecting system and vasculature without exposure to radiation.
MRU is sensitive to motion artifact and necessitates anesthetic sedation of young children.
Urodynamic studies:
This is valuable to assess voiding and bladder function in those with suspected neurogenic bladder.
Cystoscopy, vaginoscopy, and retrograde pyelogram are endoscopic procedures that allow direct visualization of the genital and lower urinary tracts and may include radiographic visualization of the upper urinary tract (e.g. retrograde pyelogram).
Pressure-perfusion studies (Whitaker test):
This measure differential pressures of the renal pelvis and the bladder
It may be useful in evaluating equivocal urinary tract obstruction
It is invasive and depends on percutaneous placement of a catheter
It is seldom used in the modern era of nuclear renography
6.4 Duplex (Duplicated) System
6.4.1 Introduction
A duplex collecting system is one of the most common congenital urinary tract abnormalities.
It is characterized by an incomplete fusion of upper and lower pole moieties resulting in a variety of complete or incomplete duplications of the collecting system.
A duplex (duplicated) collecting systems can be defined as renal units containing two pyelocaliceal systems that are associated with a single ureter or with double ureters.
The two ureters empty separately into the bladder or fuse to form a single ureteral orifice.
Duplex collecting systems can be unilateral or bilateral and can be associated with a variety of congenital genitourinary tract abnormalities (Figs. 6.2, 6.3, 6.4, 6.5, 6.6, and 6.7).
Figs. 6.2, 6.3, 6.4, 6.5, 6.6, and 6.7
Intravenous urography and CT urography showing duplex ureters. In the intravenous urography pictures, each ureter is draing one renal unit. There is an associated hydronephrosis in the upper renal unit. The lower renal unit is normal. Note also on the CT urography the associated hydronephrosis and hydroureters in the lower renal unit while the upper renal unit is normal
The exact incidence of ureteral duplication is not known but an incidence as high as 8 % in children was reported.
In patients with complete duplication on one side, there is a 40 % chance of finding complete duplication on the other side.
Approximately 10 % of siblings may also be affected by complete duplication.
Duplex collecting systems are seen in 0.7 % of the normal adult population and in 2–4 % of patients investigated for urinary tract symptoms.
The duplicated ureters can be:
Bifid ureters (partial or incomplete duplication)
The two ureters fuse together and insert distally as a single ureter into the urinary bladder.
Complete duplication where the two ureters empty separately into the urinary bladder.
The upper ureter is more likely to be associated with ectopic insertion, ureterocele, and/or obstruction.
Caudal or medial ectopia describes the ureteral orifice when located at the proximal lip of the bladder neck or more distal.
The lower ureter is more frequently associated with VUR.
The upper pole is one of the components of the duplex kidney.
The upper pole ureter drains the upper pole of a duplex kidney.
Similarly, the lower pole of the kidney is drained by the lower-pole ureter.
Most patients are asymptomatic, with urinary tract abnormalities being detected incidentally on imaging studies performed for other reasons.
These anomalies are commonly asymptomatic and considered an anatomical variant.
Ureteropelvic obstruction is more common when a duplex kidney exists and can be inherited in an autosomal dominant pattern.
Congenital renal anomalies in patients with classic bladder exstrophy occur in 2.8 % of patients.
The most common anomaly is a duplicated collecting system, which occurs in approximately 1.3 % of patients.
Duplex collecting systems may be complicated by:
Vesicoureteral reflux
Obstruction
Ureterocoele
Each of these complications may have adverse effects on the ipsilateral kidney.
A patient’s duplex kidney is almost always more elongated than his/her nonduplex kidney.
The kidney may be enlarged when hydronephrotic and can be associated with rotational anomalies.
Magnetic resonance urography (MRU) may be used as the primary diagnostic method for assessing a duplex ectopic ureter, as well as the complications associated with duplex kidneys.
If vesico-ureteral reflux exists, the presence of an ectopic ureter in a nonfunctioning moiety can best be demonstrated using a voiding cystourethrogram.
Antegrade pyelography is useful in patients with hydronephrosis, to demonstrate the presence of a second ureter and to determine the level of ureteric termination.
Computed tomography (CT) scanning with contrast is valuable in the evaluation of an intravesical ureterocele, either orthotopic or ectopic.
Scintigraphy is useful in the assessment of relative renal function and in the detection of renal scars. Scintigraphy can reveal differential functioning. However, if the functioning is markedly depressed, imaging is limited.
In the absence of obstruction and/or VUR, ureteral duplication anomalies require no specific therapy.
Symptomatic patients usually have complete ureteric duplication in which the ureters are prone to develop obstruction, reflux, and infection.
Duplication anomalies with associated pathology, such as VUR or obstruction, require appropriate medical therapy and possible surgical correction.
6.4.2 Classification
Duplex collecting system or duplex kidney anomalies can be classified into the following categories depending on the level or lack of fusion:
Duplex kidney:
The duplex kidney has a single renal parenchyma that is drained by two separate pelvicalcyeal systems
Duplex collecting system: The kidney has two pyelocaliceal systems and is associated with a single ureter or with a bifid ureter (a partial duplication) or, in the case of a complete duplication, with two ureters (double ureters) that drain separately into the urinary bladder.
So, a duplex collecting system is a duplex kidney draining into:
Single ureter: Duplex kidneys and duplication pelvicalyceal systems uniting at the pelviureteric junction (PUJ)
Bifid ureter (ureter fissus): two ureters that unite before emptying into the bladder
Double ureter (complete duplication)
Bifid collecting system:
This refers to a duplex kidney with the two separate pelvicalyceal collecting systems uniting at the PUJ or as bifid ureters.
Two pelvicalyceal systems join at the ureteropelvic junction (bifid pelvis), or two ureters join before draining into the urinary bladder (bifid ureters).
Double/duplicated ureters (or collecting system):
This is characterized by two ureters that drain separately into the bladder or genital tract.
Two ureters open separately into the renal pelvis superiorly and drain separately into the bladder or genital tract.
Upper and lower pole ureters drain a duplex kidney’s upper and lower poles, respectively.
As a result of these anatomic abnormalities:
The duplicated ureters may be seen extending a variable distance down to the urinary bladder.
Obstruction of the upper pole moiety down to the bladder may be seen, often associated with a ureterocoele.
Vesicoureteral reflux into the lower pole moiety may be seen. This is often due to distortion in its insertion by an associated ureterocoele.
Ectopic insertion of the upper pole moiety e.g. into the prostatic urethra in males or vaginal vault in females.
If reflux is significant, evidence of reflux nephropathy may be evident.
6.4.3 Clinical Features
Most duplicated systems are asymptomatic and diagnosed incidentally.
Duplex collecting system may be complicated by infection, vesicoureteral reflux or obstruction.
Occasionally, hydronephrosis can be severe enough to result in flank discomfort, pain or even a palpable mass.
Classification of Duplex Collecting System
Duplex kidney: Two separate pelvicalyceal system draining a single renal parenchyma.
Duplex collecting system: A duplex kidney draining into:
A single ureter: Duplex kidney with pelvicalyceal system uniting at the pelviureteric junction.
Bifid ureters: Two ureters that unite before emptying into the urinary bladder.
Double ureters (Complete duplication)
Bifid collecting system: A duplex kidney with the two separate pelvicalyceal collecting system uniting at the pelviureteric junction or as bifid ureters (Incomplete ureteral duplication).
Double/Duplicated ureters: Two ureters that drain separately into the urinary bladder or genital tract (Complete ureteral duplication).
These are seen in patients with completely duplicated ureters.
Duplication can be variable.
At one end of the spectrum, there is merely a duplication of the renal pelvis, draining via a single ureter.
At the other extreme, two separate collecting systems drain independently into the bladder or ectopically.
Duplex systems may be unilateral or bilateral and can be associated with a variety of other congenital abnormalities of the urinary tract.
Duplex systems can be associated with Fanconi anemia.
6.4.4 Investigations
Intravenous urography (IVU) (Figs. 6.14 and 6.15):
Figs. 6.14 and 6.15
Intravenous urography showing partial (incomplete) ureteral duplication on the right side
This can demonstrate both collecting systems, but a poorly functioning system may not excrete contrast and will not be visualized.
In such a situation, the functioning lower pole moiety will be inferiorly displaced, taking on the so-called “drooping lily appearance”.
This may be confused with an upper pole mass or cyst.
A patient’s duplex kidney is usually longer than his/her nonduplex kidney.
The parenchymal thickness of one of the poles of the duplex kidney is less than that of the other pole.
The calyces are asymmetric
An ectopic, upper pole ureteric insertion can produce a nonopacified segment. This mass effect results in the “drooping lily” sign with the depression of the lower pole pelvicaliceal system.
If the lower pole of the duplex kidney is functioning poorly or not at all, the lower pole collecting system may not opacify, and no discernible parenchyma will surround it (nubbin sign). The kidney’s appearance may consequently resemble that of a nonduplex kidney with a lower polar mass or renal infarct.
A reduction in the number of calyces, the depiction of a portion of the collecting system, and the presence of a straight inferior border help to differentiate a duplex collecting system from a renal mass.
Anomalies of the ureter, such as partial or complete ureteral duplication, may be demonstrated.
Abdominal and pelvic ultrasound:
Ultrasound is useful when the duplex system is associated with obstruction/hydronephrosis.
Ultrasound is also useful in detecting associated ureterocele.
With the use of ultrasound it may be difficult to differentiate between partial and complete duplication.
The duplex kidney appears as two central echo complexes with intervening renal parenchyma.
Hydronephrosis at one pole is suggestive of a duplex kidney.
Although hydronephrosis can occur at either pole, it is more common in the upper pole.
Occasionally, two distinct collecting systems and ureters can be observed on ultrasonographic images.
Differentiating an atrophied lower pole moiety of a duplex kidney (nubbin) from other renal masses is difficult.
The nubbin of tissue from the atrophied lower pole of a duplex kidney cannot be confidently differentiated from other masses.
CT urography:
CT urography is able to delineate essentially all duplex abnormalities especially if reconstruction images are made.
The intervening renal parenchyma in a duplex kidney lacks a collecting system and major vessels, and because of this it is described as having a “faceless kidney” appearance.
A duplicated renal collecting system can be suspected if a faceless kidney is identified.
CT scan can help to determine if an obstruction exists and can aid in assessing the renal parenchyma thickness.
CT scan can also help to determine if the insertion of the duplex ureter is intravesical or extravesical.
CT scan can demonstrate the collecting system in the nubbin or the mass effect of tissue at the pole.
CT scan is superior to ultrasonography and excretory urography in diagnosing the lower pole nubbin.
Nuclear scan:
Renal scintigraphy is useful to evaluate renal function, particularly when planning corrective surgery.
Renal scintigraphy is less useful to identify non-obstructed duplex systems.
Duplex kidneys appear as two separate collecting systems on the same side of the body.
Scintigraphy may demonstrate reflux up the ureter in a nonfunctioning duplex kidney with ureteral duplication.
The presence of a duplex kidney and ureteral duplication, suggested by excretory urographic or ultrasonographic images, can be confirmed with scintigraphy.
The use of dimethyl succinic acid (DMSA) scanning to assess parenchymal function in a duplex kidney is of great value in the management of duplex kidney.
MR urography (Figs. 6.16, 6.17, 6.18, and 6.19):
Figs. 6.16, 6.17, 6.18, and 6.19
MRU showing bilateral duplex kidneys. Note the associated hydronephrosis and hydroureters
This may be used as a primary diagnostic method in assessing a duplex ectopic ureter and complications associated with duplex kidneys.
An ectopic ureter extending from a poorly functioning moiety of a duplex kidney, invisible on other imaging, may be observed with MR urography
Micturating cystourethrography:
The intravesical ectopic ureter of a nonvisualized moiety is better demonstrated using voiding cystourethrogram.
In patients with hydronephrosis, antegrade pyelography is useful for demonstrating the presence of a second ureter and for determining the level of termination.
6.4.5 Treatment and Prognosis
An asymptomatic duplex kidney usually does not require any treatment.
Surgical treatment is indicated in the presence of complications.
These complications include:
Vesicoureteral reflux into lower pole moiety
Marked hydronephrosis of the upper pole moiety may have mass effect or become infected
Antibiotic prophylaxis is given to newborns with hydronephrosis or in patients who present with urinary tract infection (UTI) until the diagnosis is made and reflux is ruled out.
Antibiotic prophylaxis is often continued in patients with obstructed systems and in infants with dilated nonobstructed systems.
Duplicated collecting systems with reflux are managed conservatively with antibiotic prophylaxis until the reflux spontaneously resolves or until the child is older (6–12 months), at which time surgery may be more easily accomplished.
In infants with duplicated systems and a well-functioning but obstructed upper-pole moiety or an obstructed ectopic single-system ureter, urinary diversion (A cutaneous ureterostomy) may be the treatment of choice until the bladder is bigger and a ureteral reimplantation with or without ureteral tailoring is more feasible.
In infants with a duplicated system and no reflux is present in the lower-pole system, a ureteroureterostomy is an option.
In those with upper-pole system that serves a duplicated ureterocele: typically makes up less than 30 % of the unilateral renal function, and preservation of this function is usually not critical.
If this poorly functioning moiety is not associated with reflux in other moieties, the best approach is excision.
If this poorly functioning moiety serves a decompressed ureterocele with no reflux, there is no indication for removal.
Each ureter drains a separate renal moiety.
If only one moiety is involved and is poorly functioning, a single-stage nephrectomy or heminephrectomy is usually curative.
The likelihood that this upper-tract approach will be curative diminishes as the number of other moieties involved with either reflux or obstruction increases.
In this case, a lower-tract approach in which all problematic ureters can be simultaneously treated is a better option.
6.5 Ectopic Ureter
6.5.1 Introduction
Normally the ureters drain via the internal ureteral orifice at the trigone of the urinary bladder.
Ectopic ureter occurs when the ureter drains to an abnormally located (ectopic) orifice.
Bilateral single-system ureteral ectopia is rare and usually coexist with other urinary tract anomalies including VUR, renal dysplasia, and rudimentary bladder development.
Ectopic ureter (or ureteral ectopia) is a congenital malformation where the ureter, rather than terminating at the urinary bladder trigone, terminates at a different abnormal location. This abnormal location is as follows:
In males, the ectopic ureter drains into:
The lower urinary bladder
The posterior urethra
The seminal vesicle
The vas deferens
The ejaculatory duct
The rectum rarely
In females, the ectopic ureter drains into:
The lower urinary bladder
The urethra
The vestibule
The vagina.
The uterus or Wolffian duct remnants rarely
An ectopic ureter is a congenital renal anomaly that occurs as a result of abnormal caudal migration of the ureteral bud during its insertion to the urinary bladder.
Failure of separation of ureteral bud from Wolffian duct results in caudal ectopia.
Ectopic ureter is commonly a result of a duplicated renal collecting system, a duplex kidney with two ureters.
One ureter drains properly to the bladder
The duplicated ureter presenting as ectopic
The Weigert-Meyer rule:
In the case with complete duplication, the ureter draining the upper moiety inserts more medial and more inferior to the lower moiety ureter and liable for obstruction while the ureter draining the lower moiety is liable for reflux.
Ectopic ureter can be associated with:
Ectopic ureter may be solitary
Approximately 80 % of ectopic ureters are associated with duplex kidneysRelated posts:
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