Urolithiasis :anatomical predisposition

1. Dept of Urology
Govt Royapettah Hospital and Kilpauk Medical College
Chennai

2. Moderators:
Professors:
 Prof. Dr. G. Sivasankar, M.S., M.Ch.,
 Prof. Dr. A. Senthilvel, M.S., M.Ch.,
Asst Professors:
 Dr. J. Sivabalan, M.S., M.Ch.,
 Dr. R. Bhargavi, M.S., M.Ch.,
 Dr. S. Raju, M.S., M.Ch.,
 Dr. K. Muthurathinam, M.S., M.Ch.,
 Dr. D. Tamilselvan, M.S., M.Ch.,
 Dr. K. Senthilkumar, M.S., M.Ch.
Dept of Urology, GRH and KMC, Chennai. 2

3. Possible reasons Debated
 debated whether the predisposition to
stone disease is a result of urinary stasis
and delayed transit time through the
nephron, leading to higher likelihood of
crystal formation and retention, or
 if these patients form stones as a result
of the same or unique metabolic
abnormalities associated with stone
formation.
3
Dept of Urology, GRH and KMC, Chennai.

4. ANATOMIC ANOMALIES
 Ureteropelvic Junction Obstruction
 Horseshoe Kidneys
 Caliceal DiverticulaMedullary
 Sponge Kidney
4
Dept of Urology, GRH and KMC, Chennai.

5. URETERO PELVIC JUNCTION OBSTRUCTION
 The incidence of renal calculi in patients with
ureteropelvic junction (UPJ) obstruction is
nearly 20%
 Husmann and colleagues (1995) provided
several lines of evidence to suggest that
patients with UPJ obstruction and
concurrent renal calculi carry the same
metabolic risks as other stone formers in the
general population.
 In their study of 111 patients 62% developed
recurrent stones after treatment of the UPJ
obstruction and 43% of the recurrences
occurred in the contralateral kidney.
5
Dept of Urology, GRH and KMC, Chennai.

6. UPJ OBSTRUCTION…
 Metabolic predisposition persisted despite
correction of the obstruction
 the type and distribution of metabolic
abnormalities identified in these patients
were similar to that of the general stone-
forming population
 hypercalciuria in 46% of patients,
 hyperuricosuria in 11%,
 hypocitraturia in 13%,
 Primary hyperparathyroidism in 13%, and
 RTA in 3%
6
Dept of Urology, GRH and KMC, Chennai.

7. UPJ OBSTRUCTION
 urinary calcium and the incidence of
hypercalciuria and hyperuricosuria were
significantly higher in the patients with stones
compared with the controls
 correction of the UPJ obstruction did not
prevent recurrent stones in most patients
7
Dept of Urology, GRH and KMC, Chennai.

8. Horseshoe Kidneys
 Horseshoe kidneys occur with a prevalence of
0.25% but have an associated rate of renal
calculi of 20%
 Because of the high insertion of the ureter into
the renal pelvis, there is a relative impairment of
renal drainage, predisposing to UPJ obstruction.
 As such, the risk of stone formation has been
attributed to urinary stasis rather than to
metabolic derangements.
 Later studies established that although
urinary stasis likely contributes to a
propensity toward stone formation in
patients with horseshoe kidneys, an
underlying metabolic abnormality is required
for stone formation to occur.
8
Dept of Urology, GRH and KMC, Chennai.

9. Caliceal Diverticula
 Caliceal diverticula are associated with stones
in up to 40% of patients
 it is unclear whether the stones are caused by
local anatomic obstruction and urinary stasis or
are due to underlying metabolic factors.
 calyceal diverticular calculi arise from a
combination of metabolic abnormalities and
urinary stasis.
 Stones formed in caliceal diverticula are mainly
composed of calcium oxalate monohydrate, but
they also contain struvite/ carbonate apatite due
to an infectious component.
 Concomitant urinary tract infection is found in up
to 40% of cases with Escherichia coli, Proteus,
and Pseudomonas being the most frequent
pathogens
9
Dept of Urology, GRH and KMC, Chennai.

10. Medullary Sponge Kidney
 Medullary sponge kidney (MSK) is a disorder
characterized by ectasia of the renal collecting
ducts
 Nephrocalcinosis and renal calculi are frequent
complications of MSK
 recurrent infection and urinary stasis within the
ectatic tubules pose a risk for stone formation
 Renal tubular defects including hypercalciuria,
impaired renal concentrating ability, and
defective urinary acidification after an
ammonium chloride load have been detected in
some MSK patients
10
Dept of Urology, GRH and KMC, Chennai.

11. MEDULLARY SPONGY KIDNEY
 The identification of mutations in the
hydrogen proton pump genes ATP6V1B1
and ATP6V0A4 in two patients with MSK
lends support to an association between
MSK and distal RTA
 Although renal acidification defects may
be associated with MSK, hypercalciuria
and hypocitraturia are likely contributing
factors even in the absence of RTA
11
Dept of Urology, GRH and KMC, Chennai.

12. THANK YOU
12
Dept of Urology, GRH and KMC, Chennai.