Development & anatomic description of horseshoe kidney & techincal aspects of PCNL in such cases

1. HORSESHOE KIDNEY
&
PCNL
Gaurav Nahar
DNB Urology(Std.)
MMHRC, Madurai

2. HORSESHOE KIDNEY
• Most common congenital renal anomaly.
• Two distinct renal masses lying vertically
on either side of the midline & connected
at their respective lower poles by a
parenchymatous or fibrous isthmus
that crosses the midplane of the body.

3. • Result of a median fusion of metanephric
tissue during early gestation.
• Subsequent entrapment of fused lower
pole isthmus by IMA results in an
incomplete cephalad migration and an
associated malrotation of the kidney.

4. HK: INCIDENCE
• Occurs in 0.25% of
the population, or
about 1 in 400
persons.
• More common in
males; M:F~2:1.
• discovered in all age
groups, ranging from
fetal life to 80 years.
• In autopsy series,
more prevalent in
children.

5. HK: AUTOPSY SPECIMEN

6. HK: EMBYROLOGY
Normal Embryology
• Pronephros,
Mesonephros,
Metanephros
• Metanephros → Adult
Kidney
• Formed from condensing
blastema of Metanephric
Mesenchyme and
Ureteric Bud from
Wolffian(Mesonephric)
duct.

7. • Kidney advances
superiorly(6th
-9th
week)
as fetus grows
caudally.
• Kidney rotates 90°
• Hilum migrates
anterior to medial.
• Kidneys land at ~L1
by week 9.
• Blood supply changes
throughout migration

10. • Shh(Sonic Hedgehog gene) in notochord and
floor plate specifically inactivated.
• Depleting axial source of Shh→kidney fusion
(even in presence of notochord).
• Thus notochord is not necessary for
nephrogenesis but is required for correct
positioning of the metanephric kidney, while
axial Shh signal is critical for kidney positioning
along the mediolateral axis.

11. HK: VARIATIONS
• Lower pole fusion(95%).
Upper pole/Interpolar region fusion(rare).
• Generally, Isthmus is bulky and consists of
parenchymatous tissue with its own blood
supply. Occasionally, it is flimsy fibrous tissue
band.
• Isthmus adjacent to L3 or L4 vertebra just below
the origin of IMA from aorta, resulting in paired
kidneys lying lower than normal.

12. • Calyces- normal number, but atypical
orientation(point posteriorly due to failure
of rotation of kidneys.)
• Ureter- inserts high & laterally into the
pelvis and has a characteristic bend as it
crosses over & anterior to the
isthmus(predisposition to UPJO).

13. • Blood supply:
One renal artery to each kidney.
Duplicate or triplicate renal arteries to 1 or
both kidneys.
Isthmus may receive a branch from each
main renal artery, or
separate supply from aorta, or
branches from inferior mesenteric,
common or external iliac or sacral arteries.

15. HK: ASSOCIATED ANOMALIES
EXTRA G.U. ANOMALIES:
• Most commonly affected organ systems:
Skeletal, CVS(ventriculoseptal defects), &
CNS.
• Found in 3% of NTDs.
• ARMs.
• 20% of Trisomy 18 (Edward syndrome).
• 60% of Turner syndrome.
• Townes-Brock syndrome.

16. G.U. ANOMALIES:
• Hypospadias & UdT(4%) - males.
• Bicornuate uterus or septate vagina or
both(7%) - females.
• Ureteral duplication(10%).
• Ectopic ureterocoele.
• VUR(50%).
• UPJO(20%).
• Multicystic dysplasia, & ADPKD.

17. HK: SYMPTOMS
• Asymptomatic in 50%.
• Symptoms typically related to
hydronephrosis, infection, or calculus
formation.
• MC symptom is vague abdominal pain that
may radiate to lower lumbar region.
• GI complaints may also be present:
nausea, vomiting, abdominal pain on
hyperextension of spine.

18. • UTIs occur in 30% of patients, and
• Calculi noted in 20% to 80%.

19. HK: DIAGNOSIS & RADIOGRAPHIC
APPEARANCE
PLAIN ABDOMINAL RADIOGRAPH:
• Kidneys somewhat low lying & close to vertebral
column; have a vertical or outward axis with
lower poles being more medial than in normal
kidney.
USG:
• Prenatal USG detects most HKs.
• USG detects the isthmus joining two lower poles
of kidneys in midline.
• scanning horizontally along midline in a
craniocaudal direction.

20. HK ON RADIOGRAPH

21. HK ON USG

22. RADIONUCLIDE SCAN:
• demonstrates abnormal axis of a horseshoe
kidney.
• A continuous band across midline is observed if
isthmus contains functioning parenchyma.
CT & MRU:
• Both characterize the isthmus.
MR ANGIOGRAPHY:
• accurately delineate vascular anatomy for
preoperative planning.

23. HK ON CT

24. HK ON BONE SCINTIGRAM

25. HK ON RADIONUCLIDE SCAN

26. HK: GADOLINIUM ENHANCED MR
ANGIOGRAM

27. CALCULI IN HORSESHOE KIDNEY
• MC complication of HK is calculi formation.
• Earlier hypothesis: calculi formation due to
higher rate of infection, stasis, & obstruction
because of abnormal position of pelvis & ureter.
• Recent review suggest combined anatomic &
metabolic causes.
• Hypovolemia, hypercalciuria & hypocitraturia:
most common metabolic defects.
• MC type of calculi: Ca oxalate.

28. KUB showing stones in a horseshoe kidney with stones
extending in the isthmus.

29. CT scan showing isthmic stone in a horseshoe kidney

30. Preoperative IVU showing Calculi in Hoseshoe kidney.

31. ESWL TO TREAT CALCULI IN HK
• Favorable factors for SWL of HK: (i) a stone
burden <1.5 cm, & (ii) nonobstructed collecting
system drainage.
• Anomalous kidney orientation makes localization
of calculi more difficult, especially for stones in
anteromedial calyces.
• Prone position may facilitate localization of
stone.
• Alternatively, a “blast path” technique may be
employed.
• Also it may interfere with fragment passage after
SWL.

32. • Clearance rate for lower calyceal stones
was inferior to that of middle and upper
calyceal stones.
• A higher number of shockwaves per
treatment required and a higher re-
treatment rate observed.
• High recurrence rate in the presence of
persistent fragments after ESWL.

33. RIRS TO TREAT CALCULI IN HK
• Ureteroscopy may be an effective
treatment modality for a stone burden <
1.5 cm in HK.
• Flexible ureteroscopes, and devices such
as Ho:YAG laser, nitinol graspers, and
ureteral access sheaths used.

34. PCNL TO TREAT CALCULI IN HK
• PCNL is ToC for calculi in HK > 1.5-2.0
cm, or when SWL fails.
• Percutaneous access to a HK is more
favorable than in normal kidneys.
• Abnormal anatomic position(lower &
incomplete/non rotation of kidneys,
calyceal orientation) causes PCNL to be
easier and more safe.

35. • Preoperative CT or MRI:
to assess for the possibility of retro-renal
colon, and
to assess the vasculature and relationship
of the calyces to the anticipated puncture
site.

36. ANATOMIC IMPLICATIONS OF HK IN
PCNL
• The anteroposterior tilt of kidney is prominent,
which makes upper pole the most superficial and
posterior aspect of HK.
• Upper pole calyces are more posterior & lateral and
often subcostal.
• Convenient & relatively safe route for PCNL access.
• Lower pole calyces are anterior, lie in a coronal
plane, angled medially and inaccessible
percutaneously.

38. • In horseshoe kidney, the frontal plane
lies more or less in the sagittal plane of
the body.
• Consequently, posterior row of calyces
point dorsomedially and ventral row
dorsolaterally, and the renal pelvis is in a
ventral position.

39. • In normal kidney anatomy, upper pole
calyxes are in front of 11 & 12 ribs;
entering them needs a supracostal
approach that may cause thoracic
complications such as pneumothorax.
• However, in a HK, since kidney is placed
lower than normal position, there is usually
no need for supracostal approach.

41. • The optimal point of entry is through a
posterior calyx, which is typically more
medial than in normal kidney because of
altered renal axis & rotation associated
with midline fusion.

43. • Initial entry into a horseshoe kidney is
more medial than in normal kidneys and
can pass through the paraspinous
musculature.
• Slightly more difficult to dilate, because
they traverse through erector spinae and
quadrates lumborum muscles.

44. • (a) Retrograde
pyelogram of a
horseshoe kidney
with intrarenal calculi.
• (b) Fluoroscopically
guided percutaneous
access to a
horseshoe kidney via
upper pole access

45. • The vasculature of horseshoe kidneys is
aberrant, but vessels enter and exit the
kidney in an antero-medial location
(except for some at the isthmus), so direct
vessel injury is rare with well-planned
access as puncture of the dorsal or
dorsolateral aspect of kidney will be well
away from major renal vessels.
• However, direct access to isthmus calyxes
are not suggested because aberrant
vessels often enter the kidney in a
dorsomedial direction.

46. • Standard site for PCNL puncture: along the
posterior axillary line just caudad to 12th rib,
but angle caudad rather than cephalad.
• This provides percutaneous access to Upper
pole posterior calyx: useful in HK because
this is the easiest calyx to enter, puncture is
subcostal, and it provides excellent access to
most of the kidney and ureter owing to the
alignment of long axis of the moiety.

47. • Entering kidney via upper pole facilitates
access to upper pole calyxes, pelvis, lower
pole calyces, PUJ and proximal ureter.
• Additionally, because longitudinal axis of
nephroscope is along the longitudinal axis
of kidneys, pressure on kidney tissue by
nephroscope and subsequent bleeding
reduces (minimizing nephroscope torque
on renal tissue during manipulation).

50. • The tracts are usually longer because of low-lying
kidneys especially in obese or muscular patients;
hence length of standard nephroscope may fall
short.
• Renal pelvis may be more anteriorly located.
• In such cases flexible nephroscopes, longer rigid
nephroscopes, and multiple access attempts are
necessary to increase the possibility of achieving a
stone-free outcome.
• Flexible nephroscopy may help gain access to lower
medial calyces, where stones are often found.

51. Intraoperative fluoroscopic image showing access to the
lower pole.

52. • After dilatation of the tract, calculi localised
& fragmented using rigid nephroscope &
pneumatic/ballistic or ultrasonic lithotripsy.
• For calculi inaccessible by rigid
nephroscopy, flexible nephroscope &
Ho:YAG laser lithotripsy done.
• Complete stone clearance should be
achieved as far as possible.

53. • Hence, PCNL offers a superior stone free
rate as compared to ESWL or RIRS in the
treatment of renal calculi in HK.
• However, for stones in an isthmic location
availability of flexible nephroscope might
achieve a better clearance.

55. THANK
YOU !!!