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Chapter 26 / Anesthetic Considerations 505
nic sympathetic outflow (approx T6) are also at risk for autonomic hyperreflexia (AH)
(73). AH occurs when noxious stimuli below the neurologic lesion result in reflex sym-
pathetic discharges without appropriate supraspinal control. The most common etiolo-
gies are bladder and bowel distention, but any noxious stimuli may induce the reflex.
Signs and symptoms of AH include headache, diaphoresis, flushing, hypertension, and
bradycardia or tachycardia. In a series of 20 patients with SCI undergoing SWL, one
patient experienced AH, with a mean increase of systolic blood pressure by 44 mmHg,
diastolic blood pressure by 24 mmHg, and bradycardia with a mean heart rate of 22 bpm
(74).
Several case reports have been published documenting the efficacy and safety of SWL
and PCNL in patients with SCI (74–80). Although the total number of patients is small,
there appears to be a moderate success rate (53–100%) with low risk of AH
(0–29%). Patients with SCI undergoing lithotripsy require general anesthesia or neuro-
axial blockade (spinal/epidural) to attenuate/prevent AH. Preoperative consideration
may include a bowel prep to maximize stone imaging and decrease bowel distention
(74). In a study of 69 patients with SCI undergoing urological surgery, laboratory evalu-
ations revealed associated morbidities, including restrictive pulmonary dysfunction
(69%), anemia (41%), hypoproteinemia (38%), and renal insufficiency (23%) (81).
Intraoperatively, management of AH includes removing the offending stimulus, treating
the sympathetic response with antihypertensives and bradycardia with atropine or
glycopyrolate (82,83). Tachycardia may be treated with a short-acting beta blocker such
as esmolol. Padding all pressure points will also decrease the risk of AH. Postopera-
tively, these patients continue to be at risk for AH and meticulous attention to pain con-
trol and avoidance of bowel/bladder distention are essential. The use of epidural anes-
thesia with local anesthetic to control AH in the postoperative period has been reported
(84).
In summary, patients with chronic spinal cord injury are at an increased risk for
urolithiasis and require anesthesia for SWL, PCNL and laser lithotripsy to attenuate or
prevent AH.
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Chapter 27 / Complications of Urinary Stone Surgery 511
511
From: Current Clinical Urology, Urinary Stone Disease:
A Practical Guide to Medical and Surgical Management
Edited by: M. L. Stoller and M. V. Meng © Humana Press Inc., Totowa, NJ
27
Complications of Urinary Stone Surgery
Ruben Urena, MD, Freddy Mendez-Torres, MD,
and Raju Thomas,
MD
CONTENTS
INTRODUCTION
COMPLICATIONS OF EXTRACORPOREAL SHOCKWAVE LITHOTRIPSY
COMPLICATIONS OF PERCUTANEOUS NEPHROSTOLITHOTOMY
COMPLICATIONS OF URETEROSCOPY
COMPLICATIONS RELATED TO OPEN SURGERY
REFERENCES
Key Words: Infection; hemorrhage; complication; fistula.
INTRODUCTION
The surgical treatment of urinary tract calculi has changed enormously during the past
two decades. With advances in fiberoptics, development of flexible instrumentation, and
the widespread use of extracorporeal shockwave lithotripsy (SWL), open stone surgery
(OSS) has mostly been replaced by minimally invasive procedures for managing both
renal and ureteral calculi.
The trend of urologists involved in the management of patients with urinary tract
stones is to choose the less invasive and more effective treatment modality, based on
patient and stone characteristics. Among these minimally invasive techniques available
are SWL, percutaneous nephrostolithotripsy (PCNL), retrograde ureteroscopic intrarenal
surgery (RIRS), and laparoscopic stone surgery. Not infrequently, some of these tech-
niques are used in combination in the treatment of complex stone disease, wherein SWL
is combined with either PCNL (sandwich technique) or with RIRS.
As new and less invasive modalities and techniques have emerged, so has the aware-
ness of identifying and treating associated complications.
512 Urena, Mendez-Torres, and Thomas
COMPLICATIONS OF EXTRACORPOREAL
SHOCKWAVE LITHOTRIPSY
The first clinical application of extracorporeal shockwave lithotripsy was reported by
Chaussy et al. (1) in 1980. It received FDA approval in the United States in 1984 (2).
Since then, SWL indications have increased and gained widespread acceptance for the
management of renal and ureteral lithiasis.
All lithotriptors rely on the coordination of their four basic components: (a) shockwave
source, (b) shockwave focusing, (c) shockwave coupling, and (d) stone imaging. Know-
ing the basic functioning principles of a given lithotriptor is crucial for urologists to help
select the one which will provide the best results while minimizing complications.
Shockwave generators are categorized according to their energy source. The three
commercially available energy sources for lithotriptors are: (a) electrohydraulic, (b)
piezoelectric, and (c) electromagnetic. Electrohydraulic energy is produced by applying
electrical current between two electrodes; the spark-gap between the electrodes then
produces a shockwave within a fluid medium that diverges from the point of origin to
an ellipsoid or parabolic reflector, where it is reflected and redirected toward the second
focal point where the stone is located. Varying the voltage applied to the electrode
controls the intensity of shockwave energy. In piezoelectric generators, electrical cur-
rent is applied to a dish containing an array of piezoelectric crystals. The vibration of the
hemispherically arranged piezoelectric crystals generates a shockwave that converges
at the target site. In electromagnetic generators, electric current is applied to a magnetic
coil within a metallic membrane. The rapid movement of the metallic membrane gen-
erates a shockwave that is focused with an acoustic lens or parabolic reflector to the focal
point where the lithiasis is located.
Clinical Expectations
With appropriate patient selection, 80 to 85% of simple renal calculi can be satisfac-
torily treated with SWL (3–5). To get maximum stone fragmentation and to assure its
elimination, patients’ anatomic and stone characteristics should be considered. The
stone-related factors include size, number, location, and composition; the patients’ char-
acteristics include the presence of a dependent or obstructed collecting system, body
habitus, and weight (6). Alternative treatment modalities, such as PCNL, have been
recommended under such circumstances.
Although numerous reports have proven SWL to be safe, easy to use, and noninvasive
(7), it is often recognized as a form of trauma similar to renal contusions and occasionally
resulting in adverse clinical sequelae (8). Complications can present either from stone
fragmentation or from the effects of the shockwaves as they penetrate tissue.
Stone Localization Technique
Either ultrasound (US) or fluoroscopy can be used for stone localization. Fluoroscopy
allows for accurate “live” imaging of both renal and ureteral stones. The use of ultra-
sound avoids radiation exposure and allows for radiolucent stone localization. The use
of lithotriptors which combines both fluoroscopic and US imaging modalities may
improve stone localization while reducing or avoiding the risks of radiation exposure.
Shockwaves are directed and concentrated toward a defined focal point (F2), where
the stone is located. The focal volume of the lithotriptors impacts the amount of tissue
Chapter 27 / Complications of Urinary Stone Surgery 513
exposed to the shockwaves. Electrohydraulic lithotriptors are associated with a larger
focal volume, thus delivering more shockwave energy and better stone fragmentation,
but exposing surrounding body tissue to unnecessary shockwaves and producing more
pain at the skin entry site. Piezoelectric lithotriptors have smaller focal volumes, and
because of a low energy density at the skin entry site, are less painful.
First generation lithotriptors achieved shockwave coupling through a water bath.
Thereafter, generations replaced the water bath for water cushions coated with acoustic
gel, which allows for easier patient positioning.
Factors Affecting Fragmentation
The degree of stone fragmentation after lithotripsy depends on various factors. These
include stone composition and fragility, stone burden (size and number), stone location,
and the type of lithotriptor used. When adjusted for stone size, cystine and calcium
oxalate monohydrate stones are the most resistant to SWL (9–11). Next, in descending
order, are hydroxyapatite, struvite, calcium oxalate dihydrate, and uric acid stones
(12,13). Stone composition can also affect the type of fragments produced. Struvite, uric
acid, and calcium phosphate dihydrate fracture into smaller fragments that can be easily
passed. On the other hand, cystine, brushite, and calcium oxalate monohydrate are
difficult to fragment and are likely to produce relatively large fragments and, thus, are
less likely to be eliminated (12,14). Generally, brushite and calcium oxalate monohy-
drate stones less than 1.5 cm should be treated with SWL. For larger stones, PCNL or
RIRS, if feasible, should be considered.
Complications Related To Stone Fragments
Much of the morbidity associated with SWL treatment results from the fate of the
fragmented calculus. SWL can result in incomplete stone fragmentation, residual cal-
culi, steinstrasse, and/or ureteral obstruction. Patients with lithiasis and an associated
obstruction, such as ureteropelvic junction obstruction (UPJO), calyceal diverticulum,
or distal ureteral obstructive calculus, have poor outcomes after SWL therapy unless
their obstructive process is addressed first.
Stone Burden
Stone burden is perhaps the single most important factor in determining the appropri-
ate treatment modality for the management of renal calculi (15) (Fig. 1). Initial studies
reported stone-free rates of 91% for renal stones 2 cm (16). More recently, the mean
stone-free rates following SWL therapy for nonstaghorn renal calculi stratified by size
have been reported as 79.9% for stones 1 cm (63–90% range), 64.1% for 1–2 cm stones
(50–82.7% range), and 53.7% for stones >2 cm (33.3–81.4% range), and 27% at three
mo for those >3 cm, with 77% of these patients requiring re-treatment (17–22). For
staghorn calculi, the overall stone-free rate with SWL monotherapy was found to be
51.2%, with 30.5% of patients requiring auxiliary procedures (8). There exists an inverse
relationship between SWL results and stone burden; the higher the stone burden, the
lower the stone-free rates with a higher need for ancillary procedures and re-treatments.
SWL should thus be considered as a first-line management for renal stones 2 cm,
although stone composition and location have to be taken into consideration in the 1–2
cm group. For stones >2 cm, endoscopic treatment (i.e., PCNL, RIRS) should be con-
sidered as initial treatment, rather than SWL.
514 Urena, Mendez-Torres, and Thomas
Stone Location
Stone location has an impact on SWL outcome, with different stone-free results
achieved depending on the location of the stones within the calyceal system. For upper
and middle calyces, stone-free rates of 70–90% have been reported (23). On the contrary,
lower pole stones (LPS) have had limited success following SWL because of increased
difficulty in passing fragments. In 1994, Lingeman et al. (19) reported an overall stone-
free rate of 59% in a meta-analysis of patients with LPS treated with SWL. When
stratified by stone size, the meta-analysis revealed stone-free rates of 74%, 56%, and
33% for stones 1 cm, 1.1–2 cm, and >2 cm, respectively. More recently, in 2001, the
Lower Pole Study Group reported an overall stone-free rate of 37% for LPS after SWL,
with only 21% of patients being rendered stone-free when the calculus was >1 cm. They
concluded that PCNL should be considered the primary approach for LPS larger than 1
cm (24).
Poor stone localization can lead to incomplete or poor stone fragmentation, which can
result from stone migration, radiolucency, inadequate imaging equipment or technique,
and the patient’s body habitus. Constant fluoroscopic or ultrasonic imaging allows for
realignment of the stone in case of stone movement or migration. In case of radiolucent
stones, either intravenous urography or retrograde contrast injection through a ureteral
catheter must be administered to identify the stone as a filling defect (25). Sundaram
et al. (26) described a technique in which a 4-Fr whistle tip ureteral catheter is passed
alongside a previously inserted 6-Fr double-J stent and its tip positioned in the lower or
mid third of the ureter for contrast material injection during lithotripsy. They found it to
be successful in localizing radiolucent and poorly calcified renal stones during litho-
tripsy despite the presence of a double-J stent. Patient’s body habitus, such as morbid
obesity, skeletal anomalies (i.e., spinal deformity, limb contraction), and ectopic kid-
neys can make stone localization challenging. The increased distance from the skin
Fig. 1. (A) Right renal pelvic stone. (B) Adequate fragmentation and passage of <2-cm stone in
the right renal pelvis.
Chapter 27 / Complications of Urinary Stone Surgery 515
surface to the stone in obese patients may not position the stone adequately within the
lithotriptor’s focal zone. US can be used to measure such distance pretreatment, so that
a lithotriptor machine with a greater focal length and higher peak pressures (27,28) can
be used to prevent ineffective SWL in these patients. The Medstone lithotriptor has been
found to be advantageous to locate and treat lower third ureteral stones. This lithotriptor
pinpoints the stone at the F2 point with remarkable ease as opposed to lithotriptors using
fluoroscopy (29).
Although many patients have successful stone fragmentation after SWL, not all have
complete passage of these stone fragments. Stone fragment passage varies over time
according to several reported series. Drach et al. (30)described that up to 85% of patients
have radiologic evidence of residual fragments in the kidney a few days after SWL.
Others have reported spontaneous passage of most fragments during the first 3 mo after
SWL (2,31,32), whereas others have reported continued fragment clearance up to 24 mo
after treatment (33).
Residual Stone Fragments
The concept of clinically insignificant residual fragments (CIRF) after SWL was first
introduced to describe stone fragments smaller than 5 mm, not composed of struvite, in
asymptomatic patients with sterile urine (34). It is reported to be present in 12–30% of
patients after SWL (33). However, concerns remain whether CIRF are really clinically
insignificant. Streem et al. (33) and Zanetti et al. (35) at follow-up evaluations reported
residual stones less than 4 mm in size after SWL to subsequently become symptomatic
and/or required intervention in 43% and 22% of patients, respectively. Candau et al. (36)
emphasized the importance of the size of the residual fragment, 2 mm vs 2–4 mm, as
a risk factor for becoming symptomatic.
Besides the probability of small residual fragments becoming symptomatic or requir-
ing intervention, they might act as a nidus for stone growth or increase the rate of regrowth.
Stone recurrence rates have been much higher when stone fragments are present than
when patients have been rendered completely stone free (17–80% vs 6–15%, respec-
tively) (31,34,35,37–40). Similarly, Streem at al. (33) reported in a prospective study
that residual fragments <4 mm after SWL were found to increase in size in 18%, decrease
in 16%, and remain stable in 42%.
Residual stones from infectious stones can lead to postoperative bacteriuria, recurrent
or antibiotic-resistant urinary tract infections, be a focus for septicemia, and lead to an
increase in stone size (nidus). In case of metabolic stone disease, a stone-free status is
encouraged, not just to prevent recurrences but to prolong the treatment intervals (17).
Given the negative impact and long-term morbidity associated with residual fragments, the
need of achieving a complete stone-free status in all patients cannot be overemphasized.
Steinstrasse and Management
Steinstrasse, or “stone street,” is described as a long column of stone fragments within
the ureter after SWL (41)(Fig. 2). It is a well-known complication after SWL treatment
of larger renal and ureteral calculi. Different series have reported an incidence of 1–6%,
with results varying using different types of lithotriptors (42–45). Its occurrence is
related to the size and composition of the calculus being treated, the presence of a
concomitant distal ureteral obstruction (i.e., calculus or stricture), and to the effective-
ness of the lithotriptor in adequately fragmenting the stone.