MODERN
MANAGEMENT OF URINARY STONES
By: Dr
Clarence Lei Chang Moh,
KEY
WORDS: ESWL, extra-corporeal
shockwave lithotripsy; PCNL, percutaneous
nephrolithotripsy; URS, ureterorenoscopy;
UTI, urinary tract infection.
Introduction:
Urinary stones occur in up to 15% of men in a “stone-belt”
region like Malaysia; the incidence in women is 1/3 of men (1, 2). Paediatric
urolithiasis is also common in Malaysia (3). Urinary calculi accounts for 1/3
of admissions to local urological units. A ureteric colic is reputed to be the
most severe pain a man can ever experience.
However, pain is only manifested during the acute pathophysiological
response. Chronic obstruction and
infection can be “silent”, giving patients a false belief that their
traditional therapy has removed the stones.
The natural history of progressive stone disease followed up for years
is urosepsis associated with mortality (4). Unfortunately, stones causing
obstructive uropathy is still an important cause (2%) of renal failure in
Malaysia (5). It is therefore important
that urinary stones be treated, especially when there are many modern
modalities available. Urinary stone
disease is therefore an important topic in the curriculum of the family
physician. Patients already can access
numerous websites (e.g. by MUA, Malaysian Urological Association, UCLA,
University of California LA) with detailed information on stones as well as the
choice of urological techniques.
Site and
type of stones:
Stones can be found in any part of the urinary tract
(Fig. 1). 90% of stones are radio-opaque; ultrasound or spiral 5 mm. CT can
detect the rest. In the presence of
normal blood urea, precise location and renal function is usually confirmed by
IVU, intravenous urogram. The presentation, treatment and outcome depend partly
on the site and size of the stone.
Ureteric and urethral stones cause more pain and renal damage because of
obstruction. Treatment and prophylaxis
also depend on stone types (Table 1)(6).
Kidney
stones:
Kidney stones can be located in the renal pelvis or
calyces. Such stones can cause pain by obstruction and haematuria e.g. on
exercise. These two types of stones are
suitable for ESWL. Stones > 2.5 c. in size requires the endoscopic insertion
of a pre ESWL ureteric stent to prevent ureteric obstruction by fragments. Delay in treatment allows most kidney stones
in Malaysia to grow and converge to become “staghorn” type in
configuration. The bulk of such a
staghorn calculus and stones > 3.5 cm. will need to be removed by a more
invasive technique like PCNL (8, 9). Up to 60% (7) of PCNL patients need ESWL
for residual fragments not accessible through the percutaneous tract (Table 2).
In bilateral renal calculi, the better kidney should be operated first (10).
Hard stones more than 5 cm. in size, especially with an extra-renal pelvis may
be more efficiently removed by open pyelo-nephrolithotomy. Nephrectomy is
occasionally necessary when the kidney is non-functioning and becomes a source
of recurrent septicaemia.
Ureteric
stones:
Ureteric stones are most likely to be symptomatic in the
acute phase because of obstruction. The
typical “renal” colic of loin to groin pain associated with haematuria is
actually due to an ureteric stone. In
chronic obstruction, there is little pain.
In experimental complete ligation of the ureter in piglets, there is
almost complete and irreversible loss of renal function after 2 weeks.
In stone disease, the obstruction may be partial but associated
infection also causes renal damage. In a
febrile patient, the stone should be urgently bypassed with an external
percutaneous nephrostomy (under LA) or with an internal temporary (< 6
months) ureteric double J-stent under anaesthesia. Proximal ureteric stones can
be treated with ESWL (success about 70%) but distal ureteric stones can be more
reliably (almost 100% success nowadays) (11) fragmented by ureteroscopic (URS)
lithotripsy (12, 13). Ureteric stones
are classified as proximal if proximal to iliac vessels (around L5/S1) [Table
3]. Blind basket extraction, without
fluroscopic control and guide wires, is not recommended. Previously, about 30%
of ureteric stones are removed by open surgery (14). Large ( >2.5 cm.)
ureteric stones can occasionally be removed intact by open surgery which also
cost less than ESWL or URS.
Bladder
stones:
Bladder stones may be primary or secondary to outlet
obstruction or catheters. Bladder stones accounts for up to 30% of stones in
developing countries like Malaysia (15).
Primary bladder stones occur in the young (< 40 years of age)
including children. The classical
presentation is that of intermittent dysuria, haematuria and bladder outlet
obstruction. The obstruction to urine
flow can be relieved by a change of posture, as the stone is shifted away from
the bladder outlet. ESWL of bladder
stones is feasible (16) but not preferred because of cost and other easier
methods. Most bladder stones can be
removed endoscopically after fragmentation by forceps or lithotripsy. Large ( > 5 cm) or multiple bladder stones
are more reliably removed intact by open surgery.
Stones in
children:
With miniaturization of modern instruments, stones in
children can almost be treated as in adults (17). Moreover, the ureter in children can distend
to accommodate the range of adult sized fragments. However, large (e.g. >1 inch) bladder
stones in small children in developing countries are more efficiently removed
by open surgery. This can also bypass the inevitable urethral trauma and
possible long term urethral stricture.
Stones in
pregnancy:
Ureteric stones can complicate the existing predisposition
to hydronephrosis and pyelonephritis of pregnancy. As radio-contrast studies and ESWL are
contraindicated during pregnancy, treatment is usually done with the help of
ultrasound localisation and endoscopic lithotripsy (18, 19). Occasionally open surgery, diverting
nephrostomy tubes or ureteric stents had to be used, especially if a febrile
UTI persists.
ESWL & lithotripsy:
Patients often ask for “laser” therapy for their
stones. In fact, “laser” is not suitable
for extra-corporeal treatment as it destroys tissue i.e. it cuts or burns! Extra-corporeal therapy uses shockwave
lithotripsy (ESWL) in which thousands of shockwaves are produced from a source
outside the body and focused on the stone (Figure 2). ESWL was first introduced by Dornier in 1980
and rapidly became easily suitable worldwide in compact versions (20). The stone target is localised by ultrasound
or x-rays and ESWL is applied over a period of about an hour. Laser can be used directly on the stone e.g.
via an endoscope (Figure 3). However,
there are much cheaper and more reliable energy sources e.g. mechanical energy
(viz. by “Lithoclast” probes). The success of ESWL depends mainly on the size
and partly on the location of the stone.
Lower calyceal stone fragments are dependent and do not clear well. Mid-ureteric stones are obscured by the
nearby bone and difficult to localise.
The success of ESWL range from 90% (renal pelvis stone < 1 cm.) as in
Table 4 (21). More than one treatment is often necessary for stones >1 cm.
(35.6% retreatment rate in lower calix).
Parenteral analgesia is often needed for ESWL.
Complications:
Complications of stone treatment include bleeding,
infection and obstruction of the ureter by stone fragments (so called
“steinstrasse” or stone street in German).
A coagulation profile and urine culture has to be done pre-ESWL. Light haematuria for a few hours is seen in
almost all patients. Bleeding can
occasionally manifest as peri-renal haematoma. If there is fever, parenteral
antibiotics had to be given and ESWL suspended.
It is an unrealistic expectation that stones treated by lithotripsy will “vanish” with 1 session. The fragments have to pass out by urine flow
(i.e. the kidney has to be functioning) and this causes pain and
haematuria. If the stones get stuck in
the ureter for >2 weeks, or if there is fever, urgent treatment is necessary
as for ureteric stones. ESWL can rarely
cause death by splenic rupture (22) or rupture of nearby calcified vessels e.g.
splenic or aorta (23). Other rare
complications include peri-renal haematoma, ileus, pancreatitis, pneumonitis
and cardiac arrhythmia (21).
The list of contraindications for ESWL are as in Table 3.
Complications of endoscopic lithotripsy are similar plus
the risk of instrumental perforation of the urinary tract and haemolysis
through absorption of the irrigating fluid.
PCNL involves puncture of the kidney and the risk of bleeding is a
little higher (3.6% needs blood transfusion) (24).
Metabolic
work-up:
Chronic dehydration is the most important cause of
stones. For paediatric stones, recurrent stone
formers, large or multiple stones and familial stones, it is important to rule
out other underlying causes. Serum PTH
(parathyroid hormone) should be assayed if there is hypercalcaemia. Surgical removal of the hyperactive
parathyroid nodule will cure the hypercalcaemia. UTI is an important cause of
stones, especially in females. Infective
stones usually consist of magnesium, ammonium, phosphate and are of the
staghorn type. Uric acid stones are
radiolucent and patients may have gout as well.
Cystine stones are faintly radio-opaque and are familial. The basic
metabolic work-up includes serum for calcium, uric acid and urine culture. The stone can be sent for analysis. For a more detailed work-up, a 24-hour urine
collection can be sent for quantitative analysis of calcium, uric acid, oxalate
and qualitative analysis for cystine. Calcium deposits in the dilated
collecting tubules at renal papilla give rise to MSK, medullary sponge
kidney. Recurrent calcium stones,
metabolic acidosis with paradoxical alkaline urine should alert one to the
diagnosis of RTA, renal tubular acidosis. Cystinuria and hyperoxaluria are
inherited in a autosomal recessive manner. Underlying structural abnormalities
(e.g. diverticulum) and voiding dysfunction would be detected by IVU.
Spontaneous
passage of stones:
Stones < 5 mm. in size has a 98% chance of
spontaneous passage (13). Nevertheless,
some do not pass and all patients have to be followed up with KUB and renal
ultrasound to rule out silent increase in hydronephrosis. Female can pass out bigger stones as the
ureters are dilated by hormonal changes of pregnancies and especially if there
is a history of previous stone passage.
Spontaneous stone passage may be hastened by liberal intake of
fluids. Excessive fluid has been known
to cause heart failure in the elderly and hyponatraemia requiring admission to
ICU! 2 litres of urine output per day is sufficient to prevent stone
formation. The intake of fluid therefore
depends on the patient’s environment and usually should not exceed 3 litres per
day. Diuretics (e.g. Frusemide and many
Chinese preparations) were often prescribed but their use can cause
hyponatraemia.
Medical therapy:
Parenteral NSAID (nonsteroidal anti-inflammatory drug e.g.
Diclofenac 75 mg ) is the standard treatment for severe colic. This can be followed by the oral or rectal
suppository forms. Continuous usage
should be limited to 3 days because of its nephrotoxic and ulcerogenic
potential. Narcotic analgesics are used
as second line because of its side effects of sedation and nausea. Narcotics
can also be abused. Anti-spasmodics
(e.g. “Buscopan”) are not effective for pain relief and causes gut paralysis
with abdominal distension.
Medical therapy is possible in some cases and important
for stone prevention. Staghorn calculus
of uric acid (mostly radiolucent) can be dissolved by urinary alkalinisation
(keep urine pH 7-8 with potassium citrate (e.g. Mist Pot. Cit. or tablet
“Urocit-K”) or sodium bicarbonate (e.g. “Ural” powder). Mist Pot. Cit. may
contain too much glucose for diabetics. Hyperuricaemia can be reduced by oral
Allopurinol 300 mg daily. In patients
with renal impairment, the serum potassium and
sodium has to be monitored.
Alkalinisation also helps in cystine stones. In recurrent cystine stones, Penicillamine
may be used for dissolution therapy.
Infection must be cleared by therapeutic courses of antibiotics. In recurrent UTI, a nightly dose of mild
antibiotic (e.g. Trimethoprim) for 3-6 monthly is useful for prophylaxis.
Prevention
and Follow-Up:
Urinary stones recur in > 50% of patients unless
preventive measures are taken. These
include:
(a) liberal fluids to produce 2
litres urine per day
(b) normal serum uric acid level
by dieting and Allopurinol, if necessary
(c) normal serum calcium level;
exclude hyper-parathyroidism
(d) sterile urine. Add nightly dose of antibiotic (e.g.
Trimethoprim) for prophylaxis, if necessary
(e) diet without excessive
calcium (dairy products), oxalate (nuts) and urates (e.g. red meat)
(f) in recurrent uric acid or
calcium stone-formers, urinary alkalinisation with addition of citrate stone
inhibitor (25) is helpful.
Minimally invasive therapy often produce residual
fragments that require follow-up.
Follow-up KUB and/or ultrasound are done a few days after
treatment. Treatment (e.g. ESWL) is
repeated till fragments are < 5 mm. Thereafter, imaging may be done at 2-4
weeks’ interval till all fragments have cleared. Twenty percent of local
patients failed to return for the necessary follow-up upon review at 3 months
(5). Regular follow-up is therefore
essential to prevent silent obstructive uropathy and to apply ESWL before it
becomes >2 cm. Most stone-formers can
be followed up by clinic urinanalysis and ultrasound.
Summary:
Urinary stone disease can be diagnosed in the acute phase (pain and
haematuria) or in the chronic phase on health screening (urine, ultrasound,
x-ray). Stone removal is usually by
minimally invasive techniques like ESWL, PCNL, URS with open surgery reserved
for large, multiple or hard stones.
Metabolic measures and regular follow-up can reduce morbidity and renal
loss.
Table 1 : Kidney
Stone Types (2, 6)
Stone
Composition
|
Percentage
of total
|
Calcium
oxalate
|
60
|
Calcium
phosphate
|
6
|
Magnesium
Ammonium Phosphate
Struvite
(infection stones)
|
17
|
Uric
acid
|
15
|
Cystine
|
2
|
Table 2 :
Kidney Stone Treatment
Size (mm.)
|
Treatment
|
5 - 25
|
ESWL
|
25-35
|
ESWL
+ J stent
|
> 35
|
PCNL
± ESWL
|
Table 3 :
Ureteric Stone Treatment
Site
|
Treatment
|
Proximal
|
ESWL
|
Distal
|
URS
|
TABLE 4 : Re-treatment and stone-free rates after ESWL, stratified by
stone size
Location
|
Re-treatment Rate*
|
Stone-Free Rate+
|
||
œ 1 cm.
|
>
1 cm.
|
œ 1 cm.
|
>
1 cm.
|
|
Pelvis
|
17/493
(3.4)
|
40/507
(7.9)
|
316/351
(90)
|
273/331
(82.5)
|
Upper
calix
|
3/95 (3.2)
|
7/63 (11.1)
|
53/69 (77)
|
29/40 (72.5)
|
Mid
calix
|
5/126 (3.9)
|
4/36 (11.1)
|
61/76 (80)
|
13/19 (68.4)
|
Lower
calix
|
4/428
(0.93)
|
52/146
(35.6)
|
253/317
(80)
|
66/122 (54.1)
|
Values are given as number of patients/total (per
cent).
* 1,894
patients treated.
+ 1,325 patients with 3-month follow-up.
Ref. (20)
TABLE 5 : Contraindications of ESWL
1.
|
Pregnancy
|
2.
|
Coagulation
defects uncorrected.
|
3.
|
Febrile
UTI
|
4.
|
Unrelieved
obstructed kidney or calyx
|
5.
|
Non-functioning
kidney
|
6.
|
Nearby
vascular calcifications or aneurysm
|
7.
|
Stone
cannot be focused (e.g. patient too small or too big or deformed)
|
8.
|
Stone
too big (e.g. Staghorn) or too hard (e.g. calcium-oxalate monohydrate,
cystine).
|
9.
|
Not
a stone e.g. calcification of kidney or tumour.
|
10.
|
Uncontrolled
medical conditions e.g. hypertension.
|
11.
|
Supporting
endo-urological expertise not available.
|
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About the Author
Dr Clarence
Lei Chang Moh,
MBBS(Mal.), FRCS (Glasgow), FRCS Urol (UK), FEBU, FAMM
Consultant Urologist,
Kidney & Urology Centre, Normah
Hospital, 93050 Kuching
Annual Magazine, Academy of Family Physicians, Sarawak Branch, 2002:
28-35
Updated 2 Oct 2013
