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RENAL CALCULI The primary goal
to achieve maximal stone clearance with minimal morbidity to the patient
factors associated with poor stone clearance rates after SWL include
- large renal calculi

- stones within dependent or obstructed portions of the collecting system

- certain composition of the stone:
    - cystine
    - CaOx monohydrate
    - brushite

- obesity or body habitus that inhibits imaging & targeting of the stone
Factors Affecting Management of Renal Stones

stones factors
- size

- number

- composition
renal anatomic factors
 - obstruction / stasis
 - hydronephrosis
 - UPJ stenosis
 - calyceal diverticula
 - horseshoe kidney
 - ectopic kidney or fusion
 - lower pole
clinical ( patient ) factors
- infection
- obesity
- body deformation
- coagulopathy
- renal failure
- HTN
- juvenile
- elderly
Cystinuria may be revealed by
- previous stone analysis

- characteristic cystine crystals on urinalysis : HEXAGONAL
radiographic features suggestive of cystine
- LOW radiodensity

- ground - glass appearence

- smooth edges

- bilateral stones
best predictor of post-PNL urosepsis is
- stone culture or

- renal pelvic urine culture


rather than bladder urine culture
pain induced by

 nonobstructive calyceal stones is characterized by
a dull, deep ache,


different from the classic pain of renal colic
Stone factors in the treatment of  kidney calculi include
- stone burden (size and number), - stone composition, 

- stone location
single most important factor for appropriate treatment of  renal calculi
stone burden ( size & number )
cutoff points for stone size for

SWL vs other modalities
have not been definitively determined
kidney calculi divated into
- nonstaghorn

- staghorn
most rigorous definition of successful outcome of any stone removal procedure
stone free  
for patients with stones smaller than 10 mm better results
-  PNL or
-  URS


these procedures are : - more invasive, 
- associated with greater morbidity, 
- may be reserved for special circumstances (e.g., anatomic malformation causing obstruction, SWL failure).
1-st line for calculi between 10 -20 mm
SWL
can  affect the results of SWL for patients with calculi in this size range
- stone location ( lower pole )

- stone composition (cystine,CaOX mono)
less affected by stone location & composition
- PNL

- URS
nonstaghorn stones smaller than 10 mm,
SWL is usually the primary approach
stones between 10 and 20 mm
SWL can still be considered a first-line treatment unless factors of stone composition, location, or renal anatomy

suggest that a more optimal outcome may be achieved with a more invasive treatment modality (PNL or ureteroscopy).
stones larger than 20 mm should primarily be treated by
PNL


unless specific indications for ureteroscopy are present (e.g., bleeding diathesis, obesity).
most resistant to SWL
- cystine calculi
- brushite calculi

following by - CaOx monohydrate
after CaOx monohydrate

following in descending order of resistance to fragmentation
- struvite
- CaOx dihydrate
- uric acid stone
 brushite, cystine, calcium oxalate monohydrate stones should be treated by SWL only
when the stone burden is small ( less 1.5 cm )
Those patients with larger stones should preferentially be treated with
- PNL or
- URS
cystinuric pts vs CaOx stone formers
- have higher creatinine levels
- greater risk for renal loss


cystinuria - poorly compliant with medical therapy, increasing the likelihood of recurrent stone events


treatment algorithm for patients with cystine stones:
SWL monotherapy for cystine renal calculi 15 mm or smaller 


PNL for stones larger than 15 mm in diameter
Brushite calculi
have a resistance to fragmentation that is surpassed only by that of cystine calculi
when brushite calculi are suspected or confirmed
surgical treatment algorithm similar to that for cystine stones
resistance to SWL is  also characterizes
rare and very soft matrix calculi  
matrix calculi
- composed of 65% organic matter
  ( vs 2%- 3% organic matter in most noninfected calculi )


 - are radiolucent

 - often associated with urea-splitting bacteria
SWL success rates

more 1000 HU vs less 1000 HU
significantly lower for those calculi with attenuation values greater than 1000 (HU)  
anatomic factors, that can hinder stone clearance after SWL
- UPJ obstruction
- horseshoe kidney
- ectopic or fusion abnormalities
- calyceal diverticula
- hydronephrosis
UPJ obstruction

in addition to anatomic obstruction, are commonly present in pts with UPJ obstruction
underlying metabolic abnormalities
to achieve good results with less morbidity
PNL with concomitant endopyelotomy  
endopyelotomy :

retrograde vs antegrade
the antegrade approach is preferable when renal calculi are present because it simplifies the stone removal aspect of the procedure.
laparoscopic pyeloplasty with concomitant pyelolithotomy is most efficacious when
it is applied to patients with limited stone burdens  
Calyceal diverticula
congenitally derived, nonsecretory, urothelium-lined eventrations of the renal collecting system that are filled with urine
communicating with the collecting system is typically present by
narrow neck

which permits the diverticulum to fill passively with urine
Calyceal diverticula
are uncommon, having been reported as incidental findings in 0.2% to 0.6% undergoing renal imaging
calyceal diverticula and stones :
Stones have been reported to form in 9.5% to 50% of these cavities and can cause pain and hematuria or harbor bacteria
the best chance of becoming stone and symptom free
percutaneous approach for the management of subjects with diverticular stones
A direct percutaneous approach to the calyceal diverticulum is preferable d/t
it allows use of a rigid nephroscope for :

- stone
extraction,

- dilation and incision of the diverticular neck

- fulguration of the diverticular epithelium.
Retrograde ureteroscopic management is
a reasonable option for certain patients with diverticula:

  in the upper
and middle portions of the kidney

   when the stone
burden is less than 2 cm

and the diverticular neck is
short and accessible   (
Laparoscopic management optimal candidates for this approach are
with a symptomatic calyceal diverticulum

with thin overlying renal parenchyma,

those with a large stone burden,

and those with an anterior lesion inaccessible to or unsuccessfully managed by other approaches
laparoscopic approach is more invasive than PNL

 is usually limited to treatment of
diverticula in anterior calyces,

which are otherwise difficult to access with a percutaneous approach
Horseshoe kidney
is the most common congenital renal anomaly, and patients with this condition are often affected by urolithiasis
horseshoe kidney is result of
a median fusion of metanephric tissue during early gestation. Subsequent entrapment of the fused lower pole isthmus by the inferior mesenteric artery results in an incomplete cephalad migration and an associated malrotation of the kidney
In many cases,

the UPJ is anomalous because of
a high ureteral insertion into an elongated renal pelvis
up to 2/3 pts on evaluation have
- hydronephrosis
- infection
- urolithiasis
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