Duplex kidney

1. STRUCTURAL ABNORMALITIES
OF THE KIDNEY- DUPLEX KIDNEY
DR. AJAO O.E

2. OUTLINE
• Introduction
• Embryology of the Kidney
• Case report
• Duplicating collecting system
• Complications
• Radiographic features
• Treatment
• Conclusion
• References

3. INTRODUCTION
• The urinary tract, composed of the kidneys, ureters, bladder and
urethra, represents the main excretory system of mammals.
• The development of this system is made up of more than 40 different
cell types which need to proceed in a highly organized manner.
• However, mutations in the developmental genes of these cell types
can lead to a wide variety of abnormalities grouped together as
congenital abnormalities of the kidneys and urinary tract (CAKUT).

5. • Although individual malformations are considered as rare diseases,
CAKUT, taken together, has an incidence of about 3 to 6 in 1000 live
births
• They are an important cause of morbidity, and contribute significantly
to end-stage renal disease (ESRD).
• These abnormalities can result in recurrent urinary tract infections or
a buildup of urine in the urinary tract, which may damage the kidneys
or other structures.

6. DEVELOPMENT OF THE KIDNEY
INTERMEDIATE
MESODERM
The 3 embryonic
germ layers

7. • After the folding of the
embryonic disc, the
intermediate mesoderm forms a
bulging on the posterior
abdominal wall, called the
Nephrogenic Cord/ Urogenital
Ridge
• It extends from the cervical
region to the sacral region of the
embryo.
UROGENITAL
RIDGE

8. • The human kidney develops in 3
stages from rostral to caudal
• Pronephros
• Mesonephros
• Metanephros
• They are aligned adjacent to the
Wolffian /Mesonephric Duct

9. • The pronephros develop from
the cranial most part of
urogenital ridge. Regresses
completely by end of 4 weeks of
gestation.
• The mesonephros develops
caudal to the pronephros. It
consists of tubules that drain
into the mesonephric duct.

10. • The metanephros is the final
stage of kidney development
• It results from reciprocal
inductive signals between the
metanephric mesenchyme(MM)
and the ureteric bud (UB) at the
caudal end of the urogenital
bridge.

11. Formation of nephron
• The MM becomes distinct from
the surrounding loose
mesenchymal cells and come to
lie adjacent to the UB
• Upon invasion of UB, signals
from MM cause UB to branch
into a T - tubule

12. • A subset of the MM aggregates
inferior and adjacent to the
tips of the branching ureteric bud,
forming the peritubular
aggregates
• This transform to form the renal
vesicle that forms the
glomerulus, PCT, Loop of Henle
and DCT Renal

13. • Renal vesicles in contact with
the epithelium of the ureteric
bud forms a ‘COMMA SHAPE’
• Glomerulus develops from the
most proximal end of the Renal
Vesicle, farthest from UB tip.

14. • The cells develop into
Podocytes.
• Vascular cleft develops between
podocyte layers and the more
proximal cells – ‘S SHAPE’
• Endothelial cells migrate into the
vascular cleft
• Mesangial cell ingrowth follows
the endothelial cells into the
vascular cleft.

16. Formation of collecting
system
• The collecting ducts are all
derived from the Ureteric Bud.
• The ureteric bud initially
penetrates the metanephric
mesoderm, and then undergoes
repeated branching to form the
ureters, renal pelvis, major
calyces, minor calyces, and
collecting ducts.

17. Development of Vasculature
• Vasculogenesis
• Angiogenesis
• Endothelial progenitors within
the MM give rise to renal
capillaries that form a rich
network around the developing
nephritic tubules.

18. RENAL ASCENT
• From 6th to 9th weeks the kidneys
ascend to a lumbar site just below
adrenals
• As they migrate, they are
vascularized by a succession of
transient aortic sprouts that final
form in the upper lumbar region
and become the definitive renal
arteries

19. Anomalies in number
• Renal agenesis When ureteric
bud fails to contact MM
• Duplications When ureteric
bud splits early before reaching
MM
• Ectopic ureters When two
ureteric buds arise from
mesonephric duct

20. Anomalous Ascent
• When the kidney fails to ascend
properly, its location becomes
ectopic.
• The inferior poles of the kidneys
may also fuse, forming a horseshoe
kidney and ascent is stopped by
inferior mesenteric artery
• Kidney may fuse to the
contralateral one and ascends to
the opposite side, resulting in a
cross-fused ectopy.

21. Anomalous position
• Malrotated Kidneys - Calyces face anteriorly or antrolaterally.
• Have some element of obstruction causing inadequate drainage
which leads to infection & stone formation
• Other abnormal positions include-
• Ventral Position
• Ventromedial Position
• Dorsal Position
• Lateral Position

22. Polycystic kidneys
• Hereditary – autosomal
dominant
• Kidneys enlarged, studded with
cysts
• Unyeilding capsule compresses
renal parenchyma causing
atrophy
• Liver, lungs and pancreas may be
affected

23. • Loin pain- weight dragging upon pedicle or capsule stretch,
hemorrhage in cyst, stone formation
• Abdominal mass- confused with cystic tumor
• Hematuria- cyst rupture in pelvis, moderate, episodic.
• Hypertension, infection, CRF.
• Nonspecific symptoms: anorexia, headache, vague abdominal
discomfort, vomiting, drowsiness, anemia.
• ESRD: suddenly in middle age, RRT

24. Case report
• A 30 year old man who initially presented three years previously to
the emergency department with right loin pain and a three month
history of haematuria.
• He reported no other urinary symptoms and was otherwise fit and
well with no significant past medical history.
• Flexible cystoscopy was unremarkable and evaluation with ultrasound
and a CT scan demonstrated a large right sided renal cyst which was
subsequently treated with laparoscopic marsupialization draining 2.2
litres of fluid

25. • The patient was referred two years following this with recurrence of
his right loin pain and a general feeling of discomfort.
• Investigation by a repeat CT scan revealed the presumed renal cyst
was in fact a dilated non-functioning upper moiety and dilated ureter
that traced downwards into the pelvis.
• The patient underwent excision of the non-functioning right upper
pole moiety and megaureter using an open approach.

26. • Prior to incision the patient underwent cystoscopy and stenting of the
lower pole normal ureter.
• The cystic segment was opened and drained 2 L of cloudy urine. The
dilated upper pole segment was then excised.
• As the dilated upper ureter ran close to the lower pole ureter, the
distal end of the dilated ureter was divided to excise the ureter,
leaving a ureteral stump.

27. • The postoperative period was uneventful and the patient was
discharged home within five days.
• The stent in the lower pole ureter was removed endoscopically at
routine follow-up and the patient has remained well.

28. DUPLEX KIDNEY
• Duplex kidney also known as duplicated ureters or duplicated
collecting system is a congenital anomaly in which the ureteric bud
either splits or arises twice, resulting in a single kidney with two
pelvicalyceal system
• It is a common renal abnormality occurring in approximately 0.2-2%
of the general population and females are affected twice as
frequently as males
• Most are asymptomatic and are discovered incidentally and are seen
as a normal functioning kidney with complete or partial duplication

29. • It occurs due to an incomplete fusion of the upper and lower pole
moeity of the kidney which creates two separate drainage systems
from the kidney
• Duplex systems can have a variety of phenotypes, and multiple
classification systems have been proposed to categorise this
pathology

30. • Duplex kidney can take on one of two forms:
• Incomplete duplication: Two separate ureters are attached to the
same kidney but join together at some distance away from the kidney
to form a single ureter that enters the bladder.
• Complete duplication: Two separate ureters lead away from the same
kidney and enter the bladder separately

31. • Incomplete duplex collecting
system can either be
• bifid ureter: duplicating
pelvicalyceal systems unite at the
pelviureteric junction (PUJ)
• Inverted Y : two ureters that split
before emptying into the bladder

32. • The aetiology of most duplex kidneys can be traced back to the very
first induction steps of the ureter.
• In the majority of cases, an additional UB emerges in a rostral position
to the normal outgrowth.
• The upper (abnormal) kidney pole drains into the bladder at a site
distal to the orifice of the lower kidney pole

33. • An initially anteriorly positioned ureter thus ends up with a more
distal insertion site in the bladder
• Correct positioning of the ureter into the bladder is important to
allow formation of a normal trigone and prevent ureter reflux caused
by a malfunctioning valve or a too-short ureter tunnel.
• Because the vast majority of duplex kidneys arise from an ectopic
bud in a rostral position, it is usually the upper pole of the kidney that
is affected by VUR and hydronephrosis.

34. • About 40% of patients with duplex kidneys have been reported to
exhibit pathological manifestations with the actual percentage of
patients with symptoms likely to be lower.
• Symptoms associated with duplex kidneys can include pain,
hematuria, dysuria and abnormal frequency of micturition
• Duplex kidneys are linked to a number of renal disorders, including
pelvicalyceal dilatation, cortical scarring, VUR, hydronephrosis,
ureterocoeles and calculi formation

35. INCOMPLETE DUPLICATION
• This anomaly develops when a single ureteral bud branches before it
reaches the metanephric blastema.
• The duplicated ureters unite at a variable distance from the kidney,
and only one ureteral orifice is present on the affected side.
• Ureteroureteral reflux, also known as yo-yo, saddle, or seesaw reflux,
is a common phenomenon
• Ureteroureteral reflux prevents the upper urinary tract from ever
being completely drained resulting in stasis responsible for the
urinary tract infections frequently associated with this anomaly.

36. COMPLETE DUPLICATION
• Ureters arising from a normal position on the woliffian duct have
normally positioned ureteral orifices and normal upper tracts
• However ureters that arise from a position either lower or higher
than the normal position are associated with ectopic insertions, renal
dysplasia, and related complications
• Common complications of complete duplication are vesicoureteral
reflux, ectopic ureterocele, ectopic ureteral insertion ureteropelvic
junction obstruction of the lower pole

38. Vesicoureteral reflux
• Vesicoureteral reflux, the most commonly detected complication of
complete duplication is seen more frequently in girls than in boys.
• Virtually all such reflux is into the lower pole because the superior
and lateral position of its ureter results in a short intramural tunnel
that predisposes the ureter to reflux
• When pre- or postnatal ultrasound demonstrates hydronephrosis of
the lower pole, vesicoureteral reflux should be suspected

39. • VUR is graded with the International Reflux Study system .
• The prognostic significance of each grade is maintained for duplicated
collecting systems; low grades of reflux may be outgrown, as in
children with non duplicated systems .
• Ureteral re-implantation is done for children with ureters with high-
grade reflux.

41. Ectopic ureterocoele
• It is usually associated with dilatation of the ureter and calices above
• This complication occurs almost eight times more frequently in girls
than in boys.
• The ureterocoele produces a filling defect in the contrast-material-
filled bladder
• A large ureterocoele may prolapse into or through the urethra,
produce bladder obstruction, or even appear as an intralabial mass

42. • The obstructed dysplastic upper pole has poor function and may not
be visualized during excretory urography, even if delayed imaging is
performed.
• Duplication may be suspected during excretory urography if the
abnormally oriented kidney (lower pole) has fewer calices than the
contralateral kidney and has a laterally displaced and tortuous ureter

43. • Initial treatment, consists of incising the ureterocele to enhance
upper tract drainage
• Definitive treatment may be determined by the degree of function of
the upper pole. If there is sufficient function or parenchyma, the
upper pole is retained and an ipsilateral upper to lower
ureteroureterostomy or ureteropyelostomy is performed.
• When there is extremely poor function or thin, dysplastic
parenchyma, a partial nephrectomy and ureterectomy are performed.

45. Ectopic Ureteral Insertion
• Occurs more often in girls than in boys.
• Because the upper pole stays with the Wolffian duct longer, it may
ultimately insert in a Wolffian duct remnant rather than in the
bladder.
• The site of ectopic insertion determines the presentation and tends
to be gender specific.
• In boys, Wolffian duct-derived structures include the seminal vesicle,
vas deferens, ejaculatory duct, and prostatic urethra.
• In girls, Wolffian duct remnants are found in the vagina, urethra and
uretherovaginal septum.

46. • In boys, all extravesical insertions are supra sphincteric and produce
signs of infection, inflammation, or mass.
• Epididymitis and orchitis are common signs at presentation. Enuresis
would not be an expected symptom in boys.
• Conversely, in girls most ectopic insertions are beyond the sphincter,
so that girls often present with urinary dribbling or primary
incontinence

47. • Day and night wetness is a classic symptom.
• The girl may be wet only during the day and at night, when she is
lying down, the ureter or the vagina into which the ectopic ureter
may drain can act as a reservoir for urine.
• When the child is upright, gravity causes drainage from these
structures.

49. Lower Pole Ureteropelvic Junction
Obstruction
• Ureteropelvic junction obstruction of the lower pole is more common
in boys than in girls.
• It causes lower pole hydronephrosis. The upper pole may be normal
or abnormal.
• At excretory urography, lower pole ureteropelvic junction obstruction
could show distortion or displacement of the upper pole and its
ureter and delayed function of the lower pole

51. Radiographic features in Duplex Kidneys
• As the abnormality is an anatomic alteration, all modalities able to
image the renal tract may be able to visualize the typical features.
• General features include:
Duplicated ureters extending a variable distance down to the bladder
Obstruction of the upper pole moiety down to the bladder, often
with a ureterocele
Vesicoureteric reflux into the lower pole moiety, often due to
distortion in its insertion by the aforementioned ureterocele
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.

52. • Excretory urography (IVP)
• A poorly functioning system
may not excrete contrast.
• In such a situation, the
functioning lower pole moiety
will be inferiorly displaced,
taking on the so-called drooping
lily appearance.
• The differential for such an
appearance is that of an upper
pole mass or cyst.

53. • Ultrasound
• Ultrasound, when no
obstruction/hydronephrosis is
present can be suboptimal in the
detection of a duplicated system
and will especially struggle to
distinguish between partial and
complete duplication.
• It is able able to
detect ureterocoeles if present.

54. • Computed Tomography
Urography scan
• CT can delineate all
abnormalities essentially,
especially when performed
during the excretory (IVP) phase
• A duplicated renal collecting
system can be suspected by
identifying a faceless kidney

55. • Nuclear medicine
• Renal scintigraphy is significantly impaired in its ability to identify
non-obstructed systems, as the spatial resolution is poor.
• However, it is able to evaluate renal function and is particularly useful
in planning corrective surgery.

56. CONCLUSION
• Duplex kidneys are usually clinically silent, however, when significant
would present in children and in some instances in adulthood.
• The similar appearance it has with a renal cyst/mass can confound
the diagnosis therefore it is important that clinicians should consider
this diagnosis when presented with a patient with cysts.
• The imaging modality of choice is CT urography and treatment of
complications is mostly surgical

57. • Nordmark B. Double formations of the pelvis of the kidneys and the
ureters: embryology, occurrence and clinical significance. Acta Radiol 2010;
30:276-278.
• M. M. Rodriguez, “Congenital anomalies of the kidney and the urinary
tract (CAKUT),” Fetal and Pediatric Pathology, vol. 33, no. 5-6, pp. 293–320,
2014
• Harambat J, van Stralen KJ, Kim JJ, Tizard EJ. Epidemiology of chronic
kidney disease in children. Pediatr Nephrol. 2012;27:363-73.
• Jain S, Chen F: Developmental pathology of congenital kidney and urinary
tract anomalies. Clin Kidney J. 2018;
• JRSM Short Rep. 2013 Feb; 4(2): 13