Surgical
treatment of urinary calculi
Conservative
management
Calculi which are smaller than 0.5
cm are likely to pass spontaneously unless they are impacted. Any surgical
intervention carries the risk of complication and needless intervention should
be avoided. Small renal calculi may cause symptoms by obstructing a calyx or
acting as a focus for secondary infection. However, most can be safely observed
until they pass.
Preoperative
treatment
If urinary infection is present, appropriate
antibiotic treatment is started and continued during and after surgery as
necessary.
Operation for
stone
In developed countries, open surgery for renal
calculus disease is uncommon. Most stones are treated by specialist urologists
using minimal access and minimally invasive techniques. Open operations are
still needed when the appropriate expertise is not available or newer
techniques have failed to clear the calculus. The following account should be
read with this in mind.
Modern methods
of stone removal
Kidney stones
Percutaneous nephrolithotomy (Fig. 64.25).
This involves the placement of a hollow needle into the renal collecting
system through the soft tissue of the loin and the renal parenchyma. A wire
inserted through the needle is used to guide the passage of a series of dilators
which expand the track into the kidney until it is large enough to take the
nephroscope used to look for the stone. Small stones may be grasped under vision
and extracted whole. Larger stones must be fragmented by an ultrasound or
electrohydraulic probe and removed piecemeal.
The
aim of the procedure is to remove all fragments if possible and this may take
quite a long time if the calculus is large. When the operation is finished a
nephrostomy tube is left to drain the system. This decompresses the kidney and allows repeated access to the system if stone
particles remain. Percutaneous nephrolithotripsy is sometimes combined with
extracorporeal shock-wave lithotripsy (ESWL) in the treatment of complex
(stag-horn) calculi. The surgeon removes the central part of the stone
percutaneously and the more peripheral fragments are treated by ESWL.
Complications
of percutaneous nephrolithotripsy include (1) haemorrhage from the punctured
renal parenchyma — this may be profuse and difficult to control; (2)
perforation of the collecting system with extravasation of irrigant (which
should be saline); (3) perforation of the colon or pleural cavity during
placement of the percutaneous track.
Extracorporeal
shock-wave lithotripsy. The management of kidney stones has been revolutionised
by the development of lithotriptors. The first of these was made in Germany by
the Dornier Company. Many machines of different design ate now available.
A
urinary calculus is a crystalline structure. If it is bombarded with shock
waves of sufficient energy it will disintegrate into fragments. The principle
is seen at its simplest in the original Dornier machine where shock waves were
generated by an electrical discharge placed at one focus of an ellipsoid
mirror. The patient was positioned, under radiographic control, so that the calculus was
subjected to the full force of the shock waves where they were concentrated at
the second focus of the mirror. As shock waves are poorly transmitted through
air, both the patient and the shock-wave generators were immersed in a bath of
water.
Modern
ESWL machines do not have a water bath; the fluid is confined to the path that
the shock waves must follow to reach the kidney. The shocks may be generated by
the discharge of an array of piezoelectric cells and they may be aimed by
ultrasound rather than X-ray imaging (Fig. 64.26). The devices also differ in
the strength of the disruptive force which they can develop. Less powerful
machines are less effective in breaking stones and several treatments may be
necessary to achieve clearance of a calculus. Weaker shocks hurt less, however,
and treatment can be given without general anaesthesia.
When
ESWL is successful, the stone fragments have to be passed down the ureter.
Ureteric colic is common after ESWL and the patient must be given appropriate
analgesia, usually in the form of a nonsteroidal anti inflammatory drug such as
diclofenac. If the stone is large the bulky fragments may become impacted in the
ureter, causing obstruction. To avoid this, a self-retaining stent should be
placed in the ureter so that the kidney can drain while the pieces of
stone pass. Occasionally impacted fragments have to be removed ureteroscopically
(see below).
1n addition to pain and fragment impaction,
the principal complication of ESWL is infection. Many calculi contain bacteria
which are released when the stone is broken. It is wise to give prophylactic
antibiotics before ESWL and an obstructed system should be decompressed by the
insertion of a ureteric stent or percutaneous nephrostomy before treatment.
calyceal stones, the patients should be warned
that the clearance of fragments may take months.
There
is currently great interest in the long-term outcome of patients treated by ESWL.
Certainly some stones recur, especially if small fragments remain after
treatment. Long-term renal damage now seems unlikely.
Open
Surgery for renal calculi (Fig. 64.27)
Operations for kidney stone are usually
performed via a loin or lumbar approach. All of the procedures are difficult
unless the kidney is fully mobilised and its vascular pedicle controlled. A
sling should be placed around the upper ureter to stop stones migrating
downwards.
Pyelolithotomy
is indicated for stones in the renal pelvis. When the wall of renal pelvis has
been dissected free from its surrounding fat, an incision is made in its long
axis directly on to the stone. The stone is removed with gallstone forceps, care
being taken not to break it because fragments may be difficult to retrieve.
Stone fragments in peripheral calyces may be detected by direct palpation or by
intraoperative radiography or nephroscopy. If there is no infection, the pelvic
incision is closed with interrupted absorbable sutures. If there is gross
sepsis, it is wise to place a nephrostomy to drain the system.
Extended
pyelolithotomy. The plane between the renal sinus and the wall of the collecting
system is developed on the posterior surface of the kidney. This avoids major vessels and allows incisions to be made into the calyces so that even large
stag-horn stones can be removed intact.
Nephrolithotomy.
If there is a complex calculus branching into the most peripheral calyces, it
may be necessary to make incisions into the renal parenchyma to clear the
kidney. Nephrolithotomy may also be necessary when the adhesions resulting from
previous surgery make access to the renal pelvis difficult. The renal pedicle
must be temporarily cross-clamped to reduce bleeding from the highly vascular
renal tissue. Incisions are made just posterior and parallel to the most
prominent part of the convex renal border where the territories of the anterior
and posterior branches of the renal artery meet (Brödel’s line). Cooling the
kidney with ice packs or cooling coils extends the time that the kidney can
remain ischaemic without permanent damage. All the incisions must be carefully
closed with haemostatic sutures and the patient observed after the operation for
signs of reactionary haemorrhage.
Partial nephrectomy is sometimes preferable when the stone is present in the lowermost calyx and there is associated infective damage to the adjacent parenchyma.
Nephrectomy
is indicated when the kidney has been destroyed by obstruction and infection
associated with stone disease. This is particularly the case when there is
xanthogranulomatous pyelonephritis. This stone-related inflammatory mass must be
removed with particular care because it is liable to be attached to adjacent
structures such as the colon.
Treatment
of bilateral renal stones. Usually the kidney with better function is treated
first, the operation on the contralateral side being deferred for 2—3
months. Exceptions are if either one kidney is more painful, suggesting an
obstruction, or there is pyonephrosis in one kidney — this must be drained
by percutaneous nephrostomy.
In
cases of silent bilateral stag-horn calculi in the elderly and infirm, it may be
best not to operate. The patient should be encouraged to maintain a high fluid
intake.
Prevention of
recurrence
Frčre
Jacques, that famous lithotomist of the Middle Ages, used to say, ‘I have
removed the stone, but God will cure the patient’. When a renal stone has been
removed, steps must be taken to prevent recurrence.
Ideally
all stone formers should be investigated to exclude metabolic factors. In
practice the pick-up rate in patients with a single small stone is very small.
The urine of all patients with stones should be screened for infection. The
following investigations are appropriate in bilateral and recurrent stone
formers:
•
serum calcium, measured fasting on three occasions to exclude
hyperparathyroidism;
•
urinary urate, calcium and phosphate in a 24-hour collection. The urine
should also be screened for cystine;
•
analysis of any stone passed.
Patients
with hyperuricaemia should avoid red meats, offal and fish, which are rich in
purines and should have treatment with allopurinol. Eggs, meat and fish are high
in sulphur-containing proteins and should be restricted in those with cystinuria.
The
most effective dietary advice is that originally offered to stone sufferers by
Hippocrates. They should drink plenty to
keep their urine dilute. Fluid intake should be increased appropriately to take
account of increased losses.
Drug
treatment has not been shown to be effective other than in those few patients
who are shown to have idiopathic hypercalciuria. Bendrofluazide 5
mg and a calcium restricted diet reduces urinary calcium.