Staghorn calculi

GUIDE: DR. NITIN JOSHI
PRESENTED BY: DR. PARTH NATHWANI
MGM MEDICAL COLLEGE , MUMBAI

 Staghorn calculi are large , branched stones
that fill all or part of the renal pelvis & extend
into majority of the calices.
 Staghorn describes configuration rather than
composition
 Most staghorn consists of pure magnesium
ammonium phosphate (struvite) or a mixture
of calcium carbonate apatite.

 Also referred as infection stones because of
their strong association with UTI caused by
urea splitting organisms.
 If left untreated they may lead to renal failure,
end stage renal disease & life threatening uro-
sepsis.

 Infection stones are composed primarily of
magnesium ammonium phosphate hexahydrate
(MgNH4PO4 • 6H2O) but may in addition contain
calcium phosphate in the form of carbonate apatite
(Ca10[PO4]6 • CO3).
 A Swedish geologist discovered magnesium
ammonium phosphate in guano and named it
“struvite” after his mentor, naturalist H. C. G. von
Struve

 The process of urealysis provides an alkaline urinary
environment and sufficient concentrations of carbonate
and ammonia to induce the formation of infection
stones.
 Because urease is not present in sterile human urine,
infection with urease-producing bacteria is a
prerequisite for the formation of infection stones.
 A cascade of chemical reactions generates the
conditions conducive to the formation of infection
stones.
 Urinary urea, a constituent of normal urine, is first
hydrolyzed to ammonia and carbon dioxide in the
presence of bacterial urease:
 (NH2)2CO + H2O ➙ 2NH3 + CO2

 The alkaline urine that results from this reaction (pH
7.2 to 8.0) favors the formation of ammonium:
 NH3 + H2O ➙ NH4
+ + OH-
 Under physiologic conditions, the alkaline urine
would prevent further generation of further
ammonium.
 However, in the presence of urease, ammonia
continues to be produced despite alkaline urine,
further increasing urinary pH.

 The alkaline environment also promotes the
hydration of carbon dioxide to carbonic acid,
which then dissociates into HCO-
3 and H+.
 Further dissociation of HCO3
- yields
carbonate and two hydrogen ions:
 CO2 + H2O ➙ H2CO3
 H2CO3 ➙ H+ + HCO3
-
 HCO3
- ➙ H+ + CO3
2-

 The dissociation of hydrogen phosphate
under alkaline conditions provides phosphate,
thereby completing the generating of
constituent ions for infection stone formation:
 H2PO4
- ➙ H+ + HPO4
2-
 HPO4
2- ➙ H+ + PO4
3-

 This chemical cascade, along with physiologic
concentrations of magnesium, provides the constituents
necessary for precipitation of struvite.
 In addition, the concentrations of calcium, phosphate,
and carbonate allow precipitation of carbonate apatite
and hydroxyapatite, thereby comprising the components
of infection stones.
 Although infection stones are a direct result of persistent
or recurrent infection with urease-producing bacteria,
they may also be associated with or exacerbated by
urinary obstruction or stasis.
 As such, growth of infection stones can progress at a
very rapid rate.

 Although the family Enterobacteriaceae comprise the
majority of urease-producing pathogens, a variety of
gram-positive and gram-negative bacteria and some
yeasts and Mycoplasma species have the capacity to
synthesize urease .
 The most common urease-producing pathogens are
Proteus, Klebsiella, Pseudomonas, and Staphylococcus
species, with Proteus mirabilis the most common
organism associated with infection stones.
 Although Escherichia coli is a common cause of urinary
tract infections, rare species of E. coli produce urease.

 Bacteria may be involved in stone formation by
damaging the mucosal layer of the urinary tract,
resulting in both increased bacterial colonization
and crystal adherence .
 It has been proposed that ammonium, generated as a
result of urealysis, may alter the glycosaminoglycan
layer present on the surface of the transitional cell
layer and significantly increase bacterial adherence
to normal bladder mucosa, further exacerbating
infection risk.

 Another potential mechanism for increased stone
formation in the presence of bacteria is the finding
that particular bacteria, such as E. coli and Proteus,
may alter the activity of urokinase and sialidase,
whereas organisms not typically associated with
infection stones do not .
 This altered enzymatic activity may explain the
frequent association of E. coli with stone formation
despite lacking urease activity.

 Infection stones comprise 5 to 15% of all stones .
 However, struvite/carbonate apatite was the most common
stone composition among a population of African American
stone formers in Ohio, accounting for a third of stones in
males and nearly half the females in this population.
 Because infection stones occur most commonly in those
prone to frequent urinary tract infections, struvite stones
occur more often in women than men by a ratio of 2:1.
 Other populations at risk of recurrent infection include the
elderly , premature infants or infants born with congenital
urinary tract malformation, diabetics, and those with urinary
stasis as a result of urinary tract obstruction, urinary
diversion, or neurologic disorders.

 Spinal cord—injured patients are at particular risk
for both infection and metabolic stones owing to
neurogenic urinary tract dysfunction and
hypercalciuria related to immobility.
 Patients with a functionally complete cord
transection are at highest risk of developing a
staghorn calculus.

 Asymptomatic
 Recurrent UTI
 Haematuria
 Vague abdominal pain or flank pain
 Dysuria
 Fever & urosepsis
 Pyonephrosis
 Renal failure
 Xanthogranulomatous pyelonephritis

 CBC – chronic anaemia
 Urine analysis – alkaline ph >7 & frequently
magnesium ammonium phosphate crystals.
 Urine culture – specific organism
 Serum electrolytes & RFT – Renal failure
 Additional aspects of the metabolic evaluation of
urinary stones should be pursued because up to
50% of patients with infection-related stones have
concomitant metabolic abnormalities.
 Thus, a 24-hour urinary collection (for calcium,
oxalate, uric acid, citrate, phosphate, uric acid,
magnesium, sodium, total volume, and pH) can be
done.

 Recurrent stone formers
 Strong family history of stones
 Intestinal disease (particularly chronic diarrhea)
 Pathologic skeletal fractures
 Osteoporosis
 History of urinary tract infection with calculi
 Personal history of gout
 Infirm health (unable to tolerate repeated stone episodes)
 Solitary kidney
 Anatomic abnormalities
 Renal insufficiency
 Stones composed of cystine, uric acid, or struvite

 X ray kub - The vast majority of staghorn calculi
are radiopaque and appear as branching calcific
densities overlying the renal outline and may
mimic an excretory phase IVP. Lamination within
the stone is common
 Ultrasound kub - The collecting system is filled
with a densely calcified mass, producing marked
posterior acoustic shadowing.
 Size of stone , involvement of calycies ,
hydronephrosis, parenchymal thickness & c-m
differentiation , chronic pyelonephritis,
pyonephrosis

 IVP – pelvicalyceal anatomy , stone location &
size and excretion of the dye.
 Ct scan – imaging study of choice.
 noncontrast CT scanning followed by
intravenous contrast CT scanning is obtained
most often in the evaluation of urinary stones.
 CT scans also display the adjacent structures
and may aid in selecting the safest
percutaneous tract to access the renal collecting
system

 Delineates better renal & p-c system anatomy ,
renal excretion of dye , surrounding structure,
parenchymal thickness , hydronephrosis , HU
value
 Narrow, scarred infundibula indicate the need
for percutaneous nephrolithotomy (PCN),
while wide, large renal infundibula suggest
that extracorporeal shockwave
lithotripsy (SWL) might be adequate.
 If the passageway between the calyces and
renal pelvis is open and unrestricted, stone
fragments produced during SWL are much
more likely to pass.

 Traditionally, staghorn calculi were defined as
partial if the renal pelvic stone extended into at
least 2 calyceal groups or complete if at least
80% of the collecting system was filled.
 CT scanning with 3-dimensional reconstruction
offers accurate stone volumes, but the added
radiographic analysis is costly, time
consuming, and is nor readily available.

 Renal scintgraphy – to assess differential renal
function
 To be done in patients with chronic
pyelonephritis & obstruction .
 Chemical analysis of stone & stone culture.

 Primarily managed surgically by complete
stone clearance as the goal of treatment.
 Patients who are poor surgical candidates
dissolution therapy may be useful
 Several treatment options exist for this patients
like PCNL , ESWL , ureteroscopy , open
surgery and combination therapy.
 PCNL is usually the first line treatment for
most patients with staghorn calculi

 Chemolysis or dissolution therapy has been
around for 70 years
 Suby & albright developed suby’s solution G
which consists of citric acid , magnesium oxide
& sodium carbonate.
 Magnesium decreased mucosal irritablity &
enhanced stone dissolution by undergoing ion
exchange with calcium.
 Using a nephrostomy tube or ureteric cathater
this solution is instilled to dissolve struvite
stone

 Hemiacidrin a chemolytic agent is similar in
composition to suby’s solution G but it also
contains D-gluconic acid.
 Acids provide hydrogen ions & citrate to form
soluble complexes with calcium & phosphate
components of stone.
 But there is risk of sepsis , electrolyte
abnormality and even death with these therapy
so FDA withdrew approval for the use of these
agent

 Initially it was also combined with ESWL with
success rate of upto 60% for stone clearance but
with increased cost, hospital stay & risk of
complications it has a very limited role
 It is ineffective as a monotherapy to treat
staghorn calculus but can be useful in treating
residual stones.

 Most commonly used
 Not used usually as monotherapy as stone free
rate is is low (18-67 %)
 Eswl for staghorn calculi can cause potential
morbidity including steinstrasse, renal colic ,
sepsis & perinephric hematoma.
 Usually used in combination with PCNL or as
“sandwich” therapy.

 ESWL monotherapy for staghorn calculus is
more suited for paediatric population which
may be due to relatively small stone burden ,
better shock wave transmission & more
compliant ureter for transmission of stone
 Complications of ESWL include fever , renal
obstruction caused by steinstrasse , multiple
procedure & painfull haematuria.

 Flexible ureteroscopy has not traditionally been
used in treatment of staghorn stone
 However with development in technology and
introduction of holmium:YAG lasers & nitinol
baskets , this approach has gained popularity
in selected patients as primary or adjuvant
treatment.
 Multiple tracts may be required sometimes in
PCNL for complete stone clearance which
increases the operative morbidity & post
operative pain & discomfort.

 However flexible ureteroscope can be used to
prevent multiple puncture during PCNL
 To date there are no published data for flexible
ureteroscopy as a monotherapy for staghorn
calculus
 But it is a good modality if used as a
combination therapy with PCNL.

 Indications for AN have continuously
narrowed over past decade with emergence of
PCNL & ESWL
 AN is done for complete or near complete
staghorn calculus & where PCNL & ESWL are
difficult & complex
 Stone free rate was of 89 to 100 %
 Avearge hospital stay is of 6-7 days but less
costly than minimal invasive procedures

 Classically, the boundary of segmental renal
blood supply was identified by clamping the
posterior arterial branch & injecting methylene
blue.
 The kidney is than incised along the
demarcated avascular plane between anterior
and posterior blood supply
 Following stone removal , infundibular
reconstruction & formal closure of the entire
collecting system is performed.

 Smith & boyce modified this technique in
which parenchymal incision was made 1 to 2
cm posterior to the lateral kidney surface
without segmental vascular dissection , the
collecting system was not reconstructed , &
closure was accomplished only with a posterior
renal capsular flap.

 Open surgery (AN) is an appropriate treatment
alternative in unusual situations when a
struvite staghorn calculus is not expected to be
removed by a reasonable number of PCNL or
ESWL procedure.
 Treatment with PCNL with or without ESWL is
shown to be less successful when stone surface
area is >2500mm2 , anatomical abnormalities ,
infundibular stenosis & morbid obesity.

 Based on its superior efficacy & low morbidity ,
PCNL have now emerged as the treatment of
choice
 PCNL is less expensive , decreased need for
blood transfusion , requires shorter hospital
stay & allows a more rapid return to work.
 Stone free rates are 70 to 93 % when used as a
monotherapy
 This variation is because of different stone
burden and different technique.

 To further improve outcomes of PCNL several
technical refinements have been advocated like
multiple percutaneous access & use of flexible
nephroscopy.
 Flexible nephroscope facilitate stone clearance
because the sharp angles of p-c system are difficult
to maneuver with rigid nephroscopy
 Multiple tracts are also made to achieve complete
stone free clearance rates but it is associated with
complications like blood transfusion , fever , septic
shock , pseudoaneurysm , hydrothorax, post
operative discomfort, increased morbidity &
hospital stay.

 Residual stones following PCNL are cleared by
second look or two stage PCNL as their
clearance is necessary to prevent recurrent UTI.
 In summary , PCNL is safe , effective &
minimal invasive approach for management of
staghorn calculi.
 Procedure of choice due to higher stone free
rates and less complication rates.

 It refers to the use of multiple endo-urological
techniques for treatment of staghorn calculi
 The most commonly used therapy is
“sandwich therapy “.
 Classically described by streem & colleagues it
consists of PCNL- ESWL – PCNL
 It is less commonly used now a days because of
inferior results as compared to PCNL used as a
monotherapy.

 Following surgical therapy medical
management may be useful in preventing stone
recurrence
 Strategies include dietary modifications & oral
therapies that acidify urine , inhibit ammonia
production & sterilize the urine .

 In 1945 , shorr proposed a regimen of low
phosphorous , low calcium diet in conjunction
to oral estrogen & aluminium hydroxide gel.
 Oral estrogen acts to decrease calcium
excretion by their effect on bone mineralization
 Aluminium hydroxide gel binds phosphate in
the gut and is excreted entirely in the stool as
aluminium phospahte
 The net result of these manipulation is less
substrate excretion in urine to bind
surrounding lithogenic molecule

 Aluminium hydroxide can cause constipation ,
anorexia , lethargy , bone pain &
hypercalciuria.
 These regimens are usually not recommended
due to these side effects
 Avoidance of foods and vitamins supplements
high in phosphorus & magnesium is
recommended
 Our goal is reduction in urinary phosphate ,
magnesium & ammonia.

 Solubility is highly dependent on urinary pH &
crystallization which occurs only between 7.2 &
8.4
 In vitro studies have shown that acidification
of struvite stones to pH less than 6.5 increases
the solubility of stones and can be used to
dissolve stone
 Ascorbic acid promotes urinary alkalinization
through increase citrate production.
 A single dose of L-methionine 1500mg caused a
reduction in urinary pH values to 6.0 to 6.2
 Oral dose of L-methionine is metabolized to
sulphate and H+ ions via L-cysteine

 These are oral agents that inhibit stone growth
by blocking the cascade of events that lead to
supersaturation of struvite precursors
 Acetohydroxamic acid is the only inhibitor that
is FDA approved
 It works synergistically with several antibiotics
and thereby helps in sterilization of urine
 It has got high renal clearance & ability to
penetrate bacterial cell wall
 It decreased urine alkalinity & ammonia levels
 Contraindicated in patients with creatinine >
2.5

 Presence of persistent infection has been
demonstrated to increase the risk of stone
recurrence
 Thus eradication of infection & elimination of the
source of infection is a critical step in stone
prevention
 Post surgery chances of recurrence rate is 31% and
56% chance of resistant UTI so culture specific
antibiotics should be given
 Antibiotics may suppress bacteriuria, but in
presence of stone fragments their effectiveness in
eliminating infection is compromised.

 1. As a standard, a newly diagnosed struvite
staghorn calculus represents an indication for
active treatment intervention.
 Although this recommendation was not formally
subjected to data abstracting and statistical
methods, the panel strongly believes based on
expert opinion that a policy of watchful waiting
and observation is not in the best interest of the
standard patient with struvite staghorn calculi.
 2. As a standard, a patient with a newly diagnosed
struvite staghorn calculus must be informed about
the four accepted active treatment modalities,
including the relative benefits and risks associated
with each of these treatments.

 1. As a guideline, percutaneous stone removal,
followed by shock-wave lithotripsy and/or repeat
percutaneous procedures as warranted, should be
utilized for most standard patients with struvite
staghorn calculi, with percutaneous lithotripsy
being the first part of the combination therapy.
 2. As a guideline, shock-wave lithotripsy
monotherapy should not be used for most
standard patients as a first-line treatment choice.
 3. As a guideline, open surgery (nephrolithotomy
by any method) should not be used for most
standard patients as a first-line treatment choice.

 1. As options, shock-wave lithotripsy monotherapy
and percutaneous lithotripsy monotherapy are
equally effective treatment choices for small-
volume struvite staghorn calculi in collecting
systems which are of normal or near normal
anatomy.
 2. As an option, open surgery is an appropriate
treatment alternative in unusual situations where a
staghorn calculus is not expected to be removable
by a reasonable number of percutaneous
lithotripsy and/or shock-wave lithotripsy
procedures
 3. As an option for a patient with a poorly
functioning, stone-bearing kidney, nephrectomy is
a reasonable treatment alternative.

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