Hematoma

The delivery of shock wave energy to the kidney results in some degree of acute renal injury, including interstitial bleeding and disruption of small to medium renal arteries and veins. While transient gross hematuria is frequently seen post treatment, ESWL may also result in intrarenal bleeding (hematoma), which may extend into the perinephric tissue. Hematoma may be commonly detected on post-treatment imaging, but it is rarely clinically significant. Fig. 29.1 shows a computed tomography (CT) image of a perirenal hematoma that developed after ESWL.

A CT scan of a right perirenal hematoma (arrows) after ESWL.

The reported incidence of renal hematomas varies between 0.28% and 4.1% in large series. The most common risk factor is hypertension, especially when poorly controlled. Knapp et al. reported a 0.66% overall incidence of hematoma after ESWL: a 2.5% incidence for patients with well-controlled hypertension versus 3.8% for patients with poorly regulated hypertension. Other risk factors include older age, obesity, diabetes mellitus, clotting disorders, vascular disease, oral corticosteroid therapy, arteriosclerosis, impaired renal function, increasing stone density and urinary obstruction at the time of intervention.

Clinical signs of hematomas include intense flank or abdominal pain, tachycardia, hypotension, and anemia. Hematomas generally are self-limited, and patients respond to supportive measures such as hydration, analgesics, and transfusion. Intervention is rarely necessary and renal loss or death is exceedingly rare. Upper tract imaging (CT, magnetic resonance imaging [MRI], or ultrasonography) can be performed to establish the diagnosis when required.

Most hematomas resolve spontaneously over time. In a study of 19 patients with 21 post-ESWL hematomas followed up to 5 years (mean follow-up 19.6 months), 85.7% of the hematomas completely resolved, 9.5% became smaller, and 4.8% did not change size. No patient without preexisting hypertension became hypertensive. However, another study found that 36% of post-ESWL hematomas remained at 18 months after ESWL. Page kidney is a rare cause of hypertension due to renal parenchymal compression from a hematoma. Very rarely, incision of Gerota’s fascia to decompress a hematoma is an option for large hematomas that significantly impair renal tissue perfusion causing Page kidney. A retrospective review of this practice did not reveal a difference in outcomes with regard to long-term impairment of renal function.

Hematomas can be prevented by using shock wave energy judiciously and ensuring well-controlled blood pressure and absence of coagulation or platelet functional disturbances. Administering a small number of lower energy shock waves (voltage ramping) to the kidney before delivering therapeutic energy doses has been shown to dramatically attenuate hemorrhagic injury in an animal model. It is hypothesized that the initial lower energy shock waves induce vasoconstriction and thus limit the injury. This finding has been confirmed in a large randomized trial published in 2015 where stepwise voltage ramping reduced renal injury, including hematomas.

Another common concern is perioperative anticoagulant management of ESWL patients. Few guidelines on management of thrombotic risk while undergoing ESWL exist, and data are largely retrospective and of poor quality. For example, there is only one human study of aspirin use with ESWL. Potential bleeding risk with ESWL must be balanced with thrombotic risk specific to the patient. In a review by Bourdoumis et al. anticoagulants are stopped 5 days prior to surgery with bridging therapy as required. However, antiplatelet agents, including aspirin, are stopped at least 7 days prior. If the thrombotic risk is judged too high to stop anticoagulants, ureteroscopy is preferred due to higher ESWL complications and lower efficacy in this setting. Patients on anticoagulants warrant perioperative risk stratification and multidisciplinary consult between anesthesia, urology, and cardiology services.

Steinstrasse

Steinstrasse, the accumulation of stone fragments in the ureter after ESWL, usually occurs in patients with larger stones, typically >2 cm. Almost three-quarters of large Steinstrasse occur in the distal portion of the ureter. The reported incidence varies between 2% and 10%. An x-ray image of right proximal Steinstrasse is seen in Fig. 29.2 . Patients may have symptoms such as flank or abdominal pain, nausea, and emesis, although many are asymptomatic. Weinerth et al. reported that 5 of 19 patients with large Steinstrasse (defined as stone fragments occupying greater than one-third of total ureteral length) were asymptomatic. The occurrence of Steinstrasse can be reduced by carefully selecting patients and choosing alternative treatments for patients with stones >2 cm.

An x-ray image of right proximal Steinstrasse (arrow) after ESWL.

Patients with minimal symptoms, adequate renal function, and no signs of sepsis can be managed conservatively as 48% to 63% of Steinstrasse resolve spontaneously. However, these patients need to be followed closely to ensure that the Steinstrasse does indeed resolve; otherwise renal function can be affected.

Patients with persistent Steinstrasse, ongoing symptoms, or complications (sepsis, renal impairment) require decompression. Percutaneous nephrostomy (PCN) is an option, with 75% of Steinstrasse passed solely with percutaneous nephrostomy insertion in one study. PCN is especially useful in the setting of profound sepsis as it does not require general anesthesia with attendant hypotension risks. Ureteral stenting is another approach in an unwell patient not suitable for immediate ureteroscopy. Ureteroscopy for Steinstrasse is the definitive treatment with success rates approaching 100%, although it is not often required. Repeat ESWL is another approach reported to be 80–90% successful.

The administration of α ₁ -blockers does not eradicate Steinstrasse. However, patients receiving such agents may have better pain control. Preemptive ureteral stenting may prevent Steinstrasse in some patients with stones <3 cm, but it is ineffective for those with larger stones and is not associated with higher stone-free rates. In addition, stented patients often have significant bothersome symptoms. Finally, routine stent placement is not recommended for ureteral stones treated with ESWL. An exception are patients with anatomically or functionally solitary kidneys where stent placement must be strongly considered.

Sepsis

The overall risk of sepsis after ESWL is low at 1% except in patients with preexisting treated or untreated urinary tract infections (UTIs) and especially struvite stones. The risk of sepsis is higher in those with larger stones, especially staghorn calculi. The urine in patients with larger stones more frequently contained endotoxin, which was associated with a higher risk of sepsis. Positive preoperative urine culture, symptomatic UTI, indwelling stent, and nephrostomy tube increase the risk of fever post ESWL and warrant preoperative antibiotic therapy. Patients suspected of harboring infection stones should receive broad-spectrum antibiotic therapy because there may be discordance between stone and urine cultures. Despite sterile urine cultures before ESWL, bacteremia developed in 2.6% of those with struvite stones compared to 1.3% of patients with calcium stones. An elevation of the inflammatory mediator C-reactive protein (CRP) has also been identified as a predictor of bacteremia. Given the importance of complete clearance in infection and struvite stones, alternative treatment strategy such as PCNL or ureteroscopy should be considered in this setting.

Prophylactic antibiotic administration to patients who have sterile pre-ESWL urine is controversial. A meta-analysis by Pearle and Roehrborn demonstrated significant decrease in the development of post-ESWL UTI in patients who received prophylactic antibiotics. However, another meta-analysis by Lu et al. in 2012 argued against routine antibiotic prophylaxis in this setting. Currently, routine uncomplicated ESWL cases with sterile pretreatment urine do not receive prophylactic antibiotics.

Cardiac Arrhythmias

Cardiac arrhythmias have been reported with both gated (shock delivery synchronized to patient electrocardiogram R-wave) and, more commonly, ungated ESWL. Gating was required with the original lithotriptor, the Dornier HM3, as the water bath allowed the unfocused portion of the shock wave, which expanded spherically from the aperture of the ellipsoid, to pass through the heart resulting in a very high incidence of ventricular arrhythmias. This problem is mostly eliminated with dry head lithotriptors. Zanetti et al. reported cardiac arrhythmia incidence of 8.8% among 269 consecutive patients without a history of cardiac arrhythmia who underwent ungated ESWL. Although 59% of patients who developed arrhythmia converted back to normal sinus rhythm with temporary halting of shocks and remained so after resumption of ungated ESWL, 36% required gating to prevent arrhythmia recurrence and <1% (one patient) required atropine to manage persistent bradycardia. There was no correlation found with the side of treatment with ESWL, the number or strength of shocks, or the anesthetic agents delivered, although another study suggested right-sided renal stone ESWL is more likely to produce arrhythmia.

Greenstein et al. reported asymptomatic premature ventricular contractions in 18.4% of 125 ungated ESWL procedures. No correlations were found with age or gender of patient, presence of heart disease, size or location of stone, presence of ureteral catheter or nephrostomy, mode of anesthesia, and number of shocks delivered. Interestingly, arrhythmia was again seen more often during right-sided procedures.

The immediate postprocedure course of patients undergoing ungated ESWL was studied by Winters and colleagues. Of 82 patients, 21% developed arrhythmias. All but two arrhythmias were benign and all reversed with subsequent gating. No arrhythmias occurred with shock energies lower than 20 kV. No electrocardiogram changes were seen up to 1 hour after the procedures were completed.

Gating and ungating during the same procedure were compared by Ounnoughene and colleagues. Twenty-five patients with no cardiac history underwent ESWL with shocks delivered both gated and ungated. During the gated phase, no arrhythmias developed. During the ungated phase, 7 of the 25 patients developed arrhythmias but all were asymptomatic, and the arrhythmias regressed spontaneously after the procedure was completed.

A comparison of 3288 patients with and without a history of arrhythmia was performed by Cass. In this unique study, ungating was used in patients with known arrhythmias, and gating was used in patients without known arrhythmias. In the group with no known preexisting arrhythmias, one patient developed a malignant arrhythmia during the ungated procedure.

These findings indicate that the development of cardiac arrhythmia is mainly associated with ungated ESWL. The consequences of cardiac arrhythmia appear minimal. Most arrhythmias are benign and resolve with gating, therefore, gating is advocated in the presence of arrhythmia. Of note, gating is not required in the pediatric population as the incidence of arrhythmias is low.

Finally, cardiac pacemakers may need to be reprogrammed before ESWL treatment in consultation with cardiology service. The pacemaker should be at least 5 cm from the shock wave blast path.

Vascular Injury

Rarely, bleeding secondary to ESWL can result in hemodynamic instability. This is an indication for embolization or even surgery. Rupture of abdominal aortic aneurysms (AAAs) has been reported after ESWL. However, it is not clear whether the shock wave energy per se promoted rupture. The impact of shock wave energy on atherosclerotic vessels has been assessed in an in vitro study with minimal histologic changes in aortic aneurysmal tissue post ESWL.

There are reports of patients with smaller AAAs (<5.5-cm diameter) undergoing uneventful ESWL. Patients with calcified renal artery aneurysms <2 cm in size and vascular grafts also have undergone successful ESWL. One study suggests ensuring a minimal aneurysm to stone distance of 5 cm, with aneurysm not in parallel to the shock wave path. However, given the potentially catastrophic consequences of aneurysm rupture, careful patient consultation is warranted.

Finally, there are reports of patients developing venous thrombosis in the portal vein, renal vein, and iliac veins after ESWL. However, the exact cause of the venous thrombosis could not be determined in these cases.

Adjacent Organ Injury

Shock waves may traverse the lung parenchyma and inflict damage. There are reports of pulmonary contusion with ESWL, which typically manifests with hemoptysis or hypoxemia. ESWL has produced blast injury in rat and rabbit lung models. Children appear particularly susceptible to this type of injury, as the lung parenchyma is closer to the shock wave path, although it can occur in adults as well. Styrofoam has been applied to the chest area of children, and air vests have been worn by children to prevent such occurrences, although data supporting the use are limited.

Skeletal muscle can be traversed with shock waves during ESWL. Although studies have demonstrated increases in muscle-derived enzymes in the serum and urine of patients subjected to ESWL, we are unaware of any reports of clinically significant muscle damage or rhabdomyolysis after treatment. In fact, shock wave energy may have beneficial therapeutic effects in patients suffering from certain musculoskeletal disorders such as plantar fasciitis and calcific tendonitis.

A mild degree of hepatic injury is not uncommon after treatment of renal and proximal ureteral stones. Studies report increase in serum bilirubin, aspartate transaminase, and glutamate dehydrogenase (a marker for hepatocellular injury); however, significant injuries such as subcapsular hematoma and hepatic fracture are extremely rare. The signs of subcapsular hematoma and hepatic fracture include hypotension, tachycardia, anemia, abdominal pain, and ileus. Imaging studies (ultrasonography, CT, MRI) should be obtained if hepatic injury is suspected. Patients with subcapsular hematoma are observed closely, whereas an active intervention may be required if hepatic fracture has occurred.

A few cases of injuries to the spleen and pancreas have been reported in patients who received ESWL to treat renal stones, although these complications are rare. The manifestations vary and include abdominal pain, peritonitis, sepsis, and shock. Splenic injury is more common with treatment of the left renal unit, whereas pancreatic injury typically occurs after right-sided procedures. At least two cases of splenic rupture requiring splenectomy after treatment of an 18-mm left upper pole stone and 2-cm left renal pelvis stone have been reported. Infectious sequelae can also arise following splenic injury. Treatment of a left lower pole renal stone resulted in anemia, leukocytosis, and fever with an infected perisplenic hematoma requiring splenectomy and abscess drainage. Although select patients with spleen and pancreas injuries from ESWL can be managed with observation, a death from anemia and sepsis with this wait-and-see approach has been reported.

The pancreas also can be injured when ESWL is used to treat upper urinary tract stones. Pancreatitis has been reported after ESWL of renal calculi, as have histologic changes of pancreatic injury. As expected, the occurrence of pancreatitis is higher with ESWL of pancreatic duct stones, and more severe pancreatic injuries can occur. Late presentation of pancreatic pseudocyst requiring open surgical correction 1 year after ESWL has also been reported. Very rarely, hematomas of other organs, even thoracic spinal cord epidural hematoma, can occur.

The stomach, duodenum, small and large bowel may be injured during ESWL. In a literature review, Maker and Layke found 10 reported bowel perforations in 3423 patients (0.34%) who underwent ESWL. There were six small bowel perforations, three colonic perforations, and one dehiscence of a gastrojejunal anastomosis. All 10 patients required open surgical correction. Patients who are treated in the prone position may be at higher risk for this injury. A left ureterocolic fistula in a patient with an impacted stone was also noted in this review; the patient was treated with nephroureterectomy. An additional 12 patients had evidence of less severe injury not requiring surgery including ulcerations of the cecum, colonic hematoma, and hematochezia. The potential for upper gastrointestinal injury with ESWL was assessed by Al Karawi and colleagues who performed esophagogastroduodenoscopy in 40 patients before and after ESWL. New gastric or duodenal erosions were identified in 32 (80%) after ESWL. Although significant gastrointestinal complications are extremely rare, a high index of suspicion is warranted in any patient who develops peritonitis after ESWL. Prompt evaluation and treatment are mandatory.

There are reported cases of skin burns due to overheating of the water-filled acoustic coupling cushion. Finally, ureteral strictures following ESWL for ureteral stones are very infrequent, ranging from 0% to 2% in one meta-analysis.

Urinary Fistulas

There have been scattered reports of patients developing fistulas after ESWL, including pyelocutaneous, pyeloduodenal, ureterocolic, and ureterovaginal. The majority of these fistulas occurred in patients with staghorn stones or undiagnosed xanthogranulomatous pyelonephritis. Nephrectomy was undertaken in most of these cases. The primary renal problem was the most likely inciting factor in these cases.

Hypertension

The issue of ESWL-induced hypertension remains controversial. This association was first reported in the late 1980s, and numerous conflicting studies have been published in subsequent years. The relevant studies are profiled in Table 29.1 .

Certain patient factors and treatment approaches have been demonstrated to be associated with the development of hypertension. Janetschek and colleagues reported that age >60 years was a risk factor for the development of new-onset hypertension. They also found that older age correlated with an increase in the renal resistive index measured with Doppler ultrasonography.

In the study with the longest follow-up (19 years), Krambeck and associates reported that hypertension developed more commonly in ESWL-treated patients than in a case-controlled group of patients who had had stones but had not received ESWL. Patients subjected to bilateral ESWL were at higher risk for developing hypertension. However, risk of hypertension did not appear to relate to the number of shocks delivered or shock wave intensity. Krambeck and associates also reported that those who received ESWL were more prone to developing diabetes mellitus and that there was a positive correlation to the numbers of shocks delivered and shock wave intensity, whereas the side of the involved renal unit had no influence. A review of 70 pediatric patients by El-Nahas over an average of 5 years’ follow-up did not reveal evidence of hypertension or diabetes in this cohort, although there was evidence of reduced renal growth post ESWL in children in another study.

The literature review indicates that the association between ESWL and developing hypertension is not uniformly positive. This is at least partially due to study design and inadequate controls. In addition, hypertension is a multifactorial disease and association does not always equate with causation. Certainly, patients with renal calculi, as a group, are at a higher risk for developing hypertension. From a clinical standpoint, the risk of blood pressure effects from ESWL is rarely relevant but might be considered in a patient with poorly controlled hypertension.

Renal Insufficiency

The kidney sustains a degree of acute injury from the received shock wave energy, in part due to cavitation and shear forces exerted. The reduction in renal blood flow that occurs with delivery of shock wave energy to the kidney may produce renal ischemia, which could lead to renal injury. Animal models have demonstrated that this results in the generation of oxygen free radicals, which may further promote injury. Direct shock wave trauma also plays a role in acute renal dysfunction. Koga and colleagues examined canine kidneys after repeated ESWL treatments and positively correlated the degree of tissue hypoxia and rupture of interstitial capillaries with the number of shocks delivered.

While stone formers are at risk of developing renal insufficiency (RI), there is no current evidence to suggest that ESWL promotes it. Krambeck and associates did not find increased rates of RI after long-term follow-up in patients treated with ESWL. The majority of the patients in the aforementioned study received one or two ESWL treatments. The impact of repetitive ESWL on renal function has not been adequately addressed at this time.

There have been a few reports of patients developing renal failure after ESWL, and renal biopsies demonstrated the presence of complement fixation and antiglomerular basement membrane antibodies. Westman and colleagues questioned whether ESWL played a role in the development of renal failure because they did not find an increased number of autoantibodies associated with glomerulonephritis in 59 consecutive patients who underwent ESWL.

Although animal models have demonstrated that the smaller or underdeveloped kidney appears to be more susceptible to shock wave injury, a number of longitudinal studies performed on children who received ESWL demonstrated no reduction in renal function or growth over time. One study, by Lifshitz et al., did report attenuated renal growth in children subjected to ESWL. Given limited stone treatment options in children, ESWL is still an acceptable treatment in this group.

Shock wave lithotripsy in patients with preexisting renal insufficiency or a solitary kidney has also been studied. Chandhoke and colleagues found stable renal function after ESWL in patients with solitary kidneys or serum creatinine levels <3 mg/dL. Only patients with serum creatinine levels >4 mg/dL continued to have worsening renal function after ESWL, suggesting continued insult from the primary renal disease.

There is no question that shock wave energy induces renal trauma, with acute histologic evidence of injury at biopsy 1 week post treatment and reduced renal plasma flow immediately post treatment. The renal papilla is particularly susceptible to shock wave damage, with bleeding initiating inflammatory response and subsequent scarring. Evidence of parenchymal scarring post ESWL was noted in both animal and human studies. Yet it appears that, in the majority of patients, this renal trauma has no significant long-term impact on the renal function. Better designed longitudinal studies are needed to assess the impact of repetitive ESWL, especially in patients most susceptible to renal injury.

In the meantime, the judicious use of ESWL should help limit any reduction in renal function. This includes close monitoring for obstructive complications. Some have advocated the administration of free radical scavengers such as allopurinol, nifedipine, verapamil, and mannitol to limit acute renal injury. The experience with pharmacologic protection is too limited to advocate its use at this time. Others have shown in animal and human studies that pretreatment with lower energy shock waves may reduce renal injury through vasoconstriction.

Diabetes Risk

Theoretical risk of diabetes post ESWL is due to close anatomic position of the pancreas to the treated renal parenchyma, especially on the right side. As detailed above, pancreatic hematomas and histologic changes have been noted in pancreatic tissue post ESWL. In porcine models, single ESWL was not shown to increase risk of diabetes after ESWL, despite specifically targeting renal parenchyma close to the pancreatic tail. Similarly, human studies of 9 and 17 years’ follow-up were reassuring, with no convincing evidence of elevated diabetes risk.

Fertility Effects

Shock wave energy delivered to distal ureteral stones can theoretically injure gonadal tissue. Animal models have been used to determine the acute effects of delivering shock wave energy to the ovary. Recker and colleagues demonstrated minimal subcapsular bleeding, desquamation of superficial cells, and loss of microvilli immediately after shock wave energy was delivered to the rat ovary. However, these were transient and had resolved by 35 days. McCullough and associates demonstrated normal reproductive ability in rats that had shock wave energy delivered to the ovaries. In addition, there were no teratogenic effects noted in the progeny.

Studies of female patients have focused on the subjects’ ability to reproduce after ESWL. Two studies evaluated women who underwent ESWL for distal ureteral stones and noted no fertility problems or genetic abnormalities in their children. Despite this, the use of ESWL in girls or women of reproductive age harboring distal ureteral stones remains controversial, particularly due to the medicolegal implications of ESWL treatment in this cohort.

Male gonadal function also has been assessed in patients subjected to ESWL. Perisinakis and coworkers compared the radiation dose to gonadal tissue between ESWL of proximal and distal stones and found four times higher radiation exposure to the testes during ESWL for distal stones. They postulated that this would result in a four times higher genetic defect risk in the children of patients, although the overall risk still is thought to be exceedingly rare. Worsening of semen parameters in men who underwent ESWL for distal ureteral stones has been noted. Fortunately, the effects were self-limited, and parameters returned to baseline within 3 months. Reports of transient hematospermia in men who have been subjected to ESWL for distal ureteral stones are reflective of the potential temporary perturbation of the male reproductive tract.

Finally, pregnancy remains an absolute contraindication to ESWL treatment, although there is at least one case report of successful treatment of proximal ureteral stone at 25 weeks’ gestation. In that particular case the patient was insistent on ESWL treatment despite extensive discussion of the risks.

Potential Long-term Complications

ESWL has been shown to produce acute renal injury, primarily vascular injury with parenchymal hemorrhage and subsequent inflammation, fibrosis, and loss of functional renal tissue. As discussed above, as yet there is no evidence this trauma would translate into long-term renal dysfunction. There is, however, emerging evidence that repeated ESWL may increase subsequent stone formation risk, particularly of calcium phosphate (CaP) composition. For example, in porcine models, ESWL causes damage to medullary ascending limbs with a resultant rise in pH. This in turn can increase the risk of CaP stone formation. CaP stones, brushite in particular, are notoriously difficult to treat, making it a concerning development. Further studies in this area detailing pathogenesis and clinical implications are awaited.

Strategies to Reduce Risk of Complications

There are a number of methods to reduce complications of ESWL therapy. First, ESWL at 60 shock waves (SW)/min compared to 120 SW/min significantly reduced the size of the acute hemorrhagic lesions in a porcine study. The slower rate at 60 SW/min has also been shown to improve human stone treatment outcomes in a meta-analysis. Unfortunately, slowing the shock wave rate will increase the treatment time. Second, gradual ramping up of voltage (e.g., 100 shocks at low voltage) has also been shown to reduce the risk of hematoma formation in both porcine and human studies. This is presumably due to the protective effect of renal vasoconstriction, as confirmed by the rise in the renal resistive index. The effects of escalating the voltage on stone clearance are conflicting with improvement in one randomized trial but not in the other. Third, the protective effect of voltage ramping is amplified by the (~3 min) pause following initial low voltage shocks, and this too should be included in routine treatment protocols.

The current standard is treatment at low-to-moderate acoustic pressures with as few shock waves as possible, to minimize acute and lasting tissue injury, and at a slow shock wave rate (60 SW/min or slower), to enhance stone breakage and reduce tissue damage. Next, effective coupling of the treatment head to the patient improves transmission of acoustic energy and reduces the required number of shock waves. For example, coupling defects of only 2% coverage reduced the breakage of model stones by as much as 20–40%. An effective method is to apply the gel directly from the stock jug as a mound to the center of the treatment head, then press the cushion against the patient. The gel can be further spread out by increasing the water inflation pressure of the cushion.

Since degree of renal injury is dose-dependent for pulse amplitude and shock wave number, regular monitoring of stone fragmentation to avoid overtreatment is warranted. Strategies to reduce patient movement and respiratory excursion (e.g., adequate anesthesia) allow for improved shock delivery to the target stone. Controlling blood pressure and avoiding anticoagulant use will reduce hematoma risks. Avoiding distal ureteral obstruction is also renoprotective. Reserving ESWL for stones <2 cm in size will reduce risks of Steinstrasse and potential downstream obstruction. With regard to antibiotic prophylaxis in patients with sterile preoperative urine, a meta-analysis did not show evidence for routine antibiotic administration to reduce risk of UTIs and sepsis in patients without stents, catheters, or infected stones.

Finally, increased risk of long-term adverse effects is associated with multiple lithotripsies. Careful patient selection and consideration of alternative treatment approaches in treatment-resistant cases are recommended.