Management and prevention of renal ablative therapy complications. World J Urol. 2010;28:559-564. [PMID: 20383639 DOI: 10.1007/s00345-010-0550-6]

Histotripsy of the Proximal Ureter and Renal Pelvis: Evaluation of Urothelial Injury in a Porcine Survival Model

PURPOSE

To evaluate the response of the ureter and renal pelvis to direct targeting by histotripsy guided by cone-beam computed tomography (CT) in a human-scale porcine chronic-survival model.

MATERIALS AND METHODS

Bilateral ureteral histotripsy treatments were completed on 6 female swine (n = 12). Animals were divided into 2 groups: (a) acute (n = 2 animals, 4 treatments, sacrificed at Day 0) and (b) chronic (n = 4 animals, 8 treatments, sacrificed at Day 7 [n = 2] and Day 28 [n = 2]). For each treatment, a 2.5-cm sphere (ureter/renal pelvis and renal parenchyma) was targeted using cone-beam CT guidance. CT urography imaging was performed immediately after treatment for all animals, and on Days 7 and 28 for chronic animals, followed by sacrifice, necropsy, and histopathology. Serum chemistries were drawn before treatment and at Days 7 and 28.

RESULTS

All 12 treatments were successful in targeting the renal pelvis/ureter and renal parenchyma. CT urography findings at Day 0 included ureteral thickening (9/12), delayed parenchymal enhancement (3/12), and mild hydronephrosis (5/12), all resolving by Day 7. Histologic findings of low-grade damage resolved by Day 7. No urine leaks or ureteral strictures were observed. Renal function (creatinine and estimated glomerular filtration rate) remained within the normal range throughout the study.

CONCLUSIONS

Histotripsy treatment of the ureter and renal pelvis results in transient injuries, suggesting that treatment of central renal tumors adjacent to the ureter and renal pelvis is safe. The results of this study could help expand the range of renal tumors that can be treated with histotripsy.

Clinical translation of abdominal histotripsy: a review of preclinical studies in large animal models

Histotripsy is an emerging noninvasive, non-thermal, and non-ionizing focused ultrasound (US) therapy that can be used to destroy targeted tissue. Histotripsy has evolved from early laboratory prototypes to clinical systems which have been comprehensively evaluated in the preclinical environment to ensure safe translation to human use. This review summarizes the observations and results from preclinical histotripsy studies in the liver, kidney, and pancreas. Key findings from these studies include the ability to make a clinically relevant treatment zone in each organ with maintained collagenous architecture, potentially allowing treatments in areas not currently amenable to thermal ablation. Treatments across organ capsules have proven safe, including in anticoagulated models which may expand patients eligible for treatment or eliminate the risk associated with taking patients off anti-coagulation. Treatment zones are well-defined with imaging and rapidly resorb, which may allow improved evaluation of treatment zones for residual or recurrent tumor. Understanding the effects of histotripsy in animal models will help inform physicians adopting histotripsy for human clinical use.

Comparison of Radiofrequency Ablation Versus Cryoablation For T1 Renal Tumors: An Evidence-Based Analysis of Comparative Outcomes

Objective

To discuss the differences in the effectiveness and security for T1 renal tumors by radiofrequency ablation (RFA) and cryoablation (CA).

Methods

We systematically searched the Cochrane Library, PubMed, Embase, CNKI databases, and Science databases, and the date was from the above database establishment to August 2021. Controlled trials on RFA and CA for T1 renal tumors were included. The meta-analysis was conducted with the Review Manager 5.4 software.

Results

A total of ten studies with 2,367 patients were included in the analysis. There were no significant differences in complications (odds ratio [OR], 1.23; 95% CI, 0.80 to 1.90; p=0.35), primary technique efficacy rate (OR, 1.01; 95% CI, 0.33 to 3.14; p=0.98), changes in serum creatinine (weighted mean difference [WMD], 0.53; 95% CI, -0.50 to 1.57; p=0.31), or 5-year survival rate (hazard ratio [HR], 1.11; 95% CI, 0.41 to 3.00; p=0.84) among patients undergoing RFA and CA. However, compared with patients who underwent RFA, patients who underwent CA had a lower Local recurrence (OR: 2.25; 95% CI: 1.38 to 3.67; p = 0.001).

Conclusion

The analysis demonstrated that in the treatment of T1 renal tumors, CA may be associated with lower local recurrence rates. However, no differences were observed in terms of primary technique efficacy rate, 5-year survival rate, changes in serum creatinine, and complication rate between groups.

Systematic Review Registration

[https://www.crd.york.ac.uk/PROSPERO/], identifier PROSPERO (CRD42021295160).

Irreversible Electroporation for Renal Ablation Does Not Cause Significant Injury to Adjacent Ureter or Bowel in a Porcine Model

Objective: To evaluate the safety of irreversible electroporation (IRE) for renal ablation adjacent to the ureter or bowel. Materials and Methods: Six adult pigs each underwent bilateral IRE of the kidney. To simulate adjacence, the left proximal ureter and duodenum were secured onto the left and right kidney capsule, respectively. Two IRE probes were placed into the renal parenchyma and configured to bridge the ureter and bowel. Therapeutic IRE was delivered at 2000 V/cm for 70 pulses in both forward and reverse polarity. The animal was survived and euthanized at 1, 3, or 14 days. Histopathology was obtained for all potentially injured bowel and ureteral segments. Retrograde pyelogram (RPG) was performed on each left-sided ureter. Results: Histologic analysis of the ureter identified reactive changes at the level of the periureteral adipose tissue, which progressed from acute inflammation on day 1 to focal fibrosis by day 14. Urothelial mucosa and surrounding smooth muscle layers were unaffected at all time points. RPGs did not show any abnormalities in all specimens. Histologic analysis of the bowel demonstrated acute inflammation in the serosa and subserosal tissue on day 1. Three days after IRE, inflammation and crypt abscesses were focally present in the deep aspects of the bowel mucosa. Inflammation in the mucosal layer resolved 14 days after IRE. Conclusions: In a porcine model of renal IRE, no significant injury was apparent after intentional ablation adjacent to the ureter and bowel. IRE may be a safe alternative to thermal ablation for tumors near the ureter or bowel.

Safety and Efficacy of Retrograde Pyeloperfusion for Ureteral Protection during Renal Tumor Cryoablation

PURPOSE

To determine safety and efficacy of retrograde pyeloperfusion for ureteral protection during cryoablation of adjacent renal tumors.

MATERIALS AND METHODS

Retrospective review of 155 patients treated with renal cryoablation, including adjunctive retrograde pyeloperfusion, from 2005 to 2019 was performed. Ice contacted the ureter in 67 of the 155 patients who represented the study cohort. Median patient age was 68 years old (interquartile range [61, 74]), 52 patients (78%) were male, and 37 tumors (55%) were clear cell histology. Mean tumor size was 3.4 ± 1.3 cm, and 42 tumors (63%) were located at the lower pole. Treatment-related complication and oncologic outcomes were recorded based on a review of post-procedural images and chart review.

RESULTS

Technical success of cryoablation was attained in 67 cases (100%), and technical success of pyeloperfusion was attained in 66 cases (99%). A total of 13 patients (19.4%) experienced SIR major C or D complications related to the procedure, including hemorrhage (n = 4), urine leak (n = 3), transient urinary obstruction (n = 2), pulmonary embolism (n = 1), hypertensive urgency (n = 1), acute respiratory failure (n = 1), and ureteropelvic junction (UPJ) stricture (n = 1). No complications were attributable to pyeloperfusion. Three of 45 patients with biopsy-proven renal cell carcinoma experienced local recurrence resulting in local recurrence-free survival of 92% (95% confidence interval, 81.5%-100%) 3 years after ablation.

CONCLUSIONS

Retrograde pyeloperfusion of the renal collecting system is a relatively safe and efficacious option for ureteral protection during renal tumor cryoablation. This adjunctive procedure should be considered for patients in whom cryoablation of a renal mass could potentially involve the ureter.

Pilot in vivo studies on transcutaneous boiling histotripsy in porcine liver and kidney

Boiling histotripsy (BH) is a High Intensity Focused Ultrasound (HIFU) method for precise mechanical disintegration of target tissue using millisecond-long pulses containing shocks. BH treatments with real-time ultrasound (US) guidance allowed by BH-generated bubbles were previously demonstrated ex vivo and in vivo in exposed porcine liver and small animals. Here, the feasibility of US-guided transabdominal and partially transcostal BH ablation of kidney and liver in an acute in vivo swine model was evaluated for 6 animals. BH parameters were: 1.5 MHz frequency, 5–30 pulses of 1–10 ms duration per focus, 1% duty cycle, peak acoustic powers 0.9–3.8 kW, sonication foci spaced 1–1.5 mm apart in a rectangular grid with 5–15 mm linear dimensions. In kidneys, well-demarcated volumetric BH lesions were generated without respiratory gating and renal medulla and collecting system were more resistant to BH than cortex. The treatment was accelerated 10-fold by using shorter BH pulses of larger peak power without affecting the quality of tissue fractionation. In liver, respiratory motion and aberrations from subcutaneous fat affected the treatment but increasing the peak power provided successful lesion generation. These data indicate BH is a promising technology for transabdominal and transcostal mechanical ablation of tumors in kidney and liver.

Kidney function outcomes following thermal ablation of small renal masses

The diagnosis of small renal masses (SRMs) continues to increase likely attributable to widespread use of axial cross-sectional imaging. Many of these SRMs present in elderly patients with abnormal baseline renal function. Such patients are at risk for further decline following therapeutic intervention. Renal thermal ablation presents one approach for management of SRMs whereby tumors are treated in situ without need for global renal ischemia. These treatment characteristics contribute to favorable renal function outcomes following kidney tumor ablation particularly in patients with an anatomic or functional solitary renal unit.

Planning irreversible electroporation in the porcine kidney: are numerical simulations reliable for predicting empiric ablation outcomes?

PURPOSE

Numerical simulations are used for treatment planning in clinical applications of irreversible electroporation (IRE) to determine ablation size and shape. To assess the reliability of simulations for treatment planning, we compared simulation results with empiric outcomes of renal IRE using computed tomography (CT) and histology in an animal model.

METHODS

The ablation size and shape for six different IRE parameter sets (70-90 pulses, 2,000-2,700 V, 70-100 µs) for monopolar and bipolar electrodes was simulated using a numerical model. Employing these treatment parameters, 35 CT-guided IRE ablations were created in both kidneys of six pigs and followed up with CT immediately and after 24 h. Histopathology was analyzed from postablation day 1.

RESULTS

Ablation zones on CT measured 81 ± 18 % (day 0, p ≤ 0.05) and 115 ± 18 % (day 1, p ≤ 0.09) of the simulated size for monopolar electrodes, and 190 ± 33 % (day 0, p ≤ 0.001) and 234 ± 12 % (day 1, p ≤ 0.0001) for bipolar electrodes. Histopathology indicated smaller ablation zones than simulated (71 ± 41 %, p ≤ 0.047) and measured on CT (47 ± 16 %, p ≤ 0.005) with complete ablation of kidney parenchyma within the central zone and incomplete ablation in the periphery.

CONCLUSION

Both numerical simulations for planning renal IRE and CT measurements may overestimate the size of ablation compared to histology, and ablation effects may be incomplete in the periphery.

Percutaneous renal cryoablation complicated by hemorrhage

The authors describe a case in which a patient underwent percutaneous cryoablation of a suspected right renal cell carcinoma complicated by bleeding. Urgent angiography revealed a lower renal pole arteriovenous (AV) fistula, correlating with the recent treatment site. This AV fistula was successfully treated with coil and Gelfoam embolization. Three days later, the patient's hemoglobin dropped following dialysis. Computed tomography (CT) imaging revealed an increase in the size of the pararenal hematoma. There were multiple pseudoaneurysms as well as a small AV fistula on repeat angiography. The right main renal artery was coil embolized.

Hydrodissection using an iodinated contrast medium during percutaneous renal cryoablation

We describe our experience using an iodinated contrast solution to hydrodissect adjacent structures before percutaneous renal cryoablation. Hydrodissection was performed before cryoablation with placement of a 20-gauge, 15-cm introducer needle into the retroperitoneum under CT or ultrasonographic guidance followed by infusion of 5% dextrose in water and 2% iodinated contrast between the kidney and the adjacent organ. Ten patients underwent hydrodissection with an iodinated contrast solution at our institution. The mean tumor size was 3.1 ± 1.2 cm. The organs displaced included colon (n=7), small bowel (n=1), pancreas (n=1), and in one case, both the colon and ureter were displaced. The average displacement of all organs from the kidney was 2.8 cm (range 2.2-3.5 cm). There were no complications and no injuries to any adjacent structures. The injection of iodinated contrast allows for safe mobilization and differentiation of adjacent structures from the renal tumor and parenchyma leading to potentially safer cryoablation.

Percutaneous radiofrequency ablation of a small renal mass complicated by appendiceal perforation

Percutaneous radiofrequency ablation (RFA) has gained wide acceptance as nephron-sparing therapy for small renal masses in select patients. Generally, it is a safe procedure with minor morbidity and acceptable short-term oncologic outcome. However, as a result of the close proximity of vital structures, such as the bowel, ureter, and large vessels, to the ablative field, complications regarding these structures may occur. This is the first article describing appendiceal perforation as a complication of computed tomography-guided RFA despite hydrodissection. When performing this innovative and promising procedure one should be aware of the possibility of particular minor and even major complications.

Urinary tract effects after multifocal nonthermal irreversible electroporation of the kidney: acute and chronic monitoring by magnetic resonance imaging, intravenous urography and urinary cytology

PURPOSE

The nonthermal irreversible electroporation (NTIRE) is a novel potential ablation modality for renal masses. The aim of this study was the first evaluation of NTIRE's effects on the renal urine-collecting system using intravenous urography (IVU) and urinary cytology in addition to histology and magnetic resonance imaging (MRI).

METHODS

Eight percutaneous NTIRE ablations of the renal parenchyma, including the calyxes or pelvis, were performed in three male swine. MRI, IVU, histology, and urinary cytology follow-ups were performed within the first 28 days after treatment.

RESULTS

MRI and histological analysis demonstrated a localized necrosis 7 days and a localized scarification of the renal parenchyma with complete destruction 28 days after NTIRE. The urine-collecting system was preserved and showed urothelial regeneration. IVU and MRI showed an unaltered normal morphology of the renal calyxes, pelvis, and ureter. A new urinary cytology phenomenon featured a temporary degeneration by individual vacuolization of detached transitional epithelium cells within the first 3 days after NTIRE.

CONCLUSIONS

This first urographical, urine-cytological, and MRI evaluation after porcine kidney NTIRE shows multifocal parenchyma destruction while protecting the involved urine-collecting system with regenerated urothelial tissue. NTIRE could be used as a targeted ablation method of centrally located renal masses.