Optimization of Extended Pelvic Lymph Node Dissection Side for Prostate Cancer.

BACKGROUND: This study aimed to show the association between tumor location and laterality of positive lymph nodes by evaluating biopsy and magnetic resonance imaging (MRI) findings, and to optimize the extended pelvic lymph node dissection (ePLND) side for prostate cancer. METHODS: The study enrolled patients who underwent robot-assisted radical prostatectomy with ePLND. Tumor locations were determined according to International Society of Urological Pathology grade group 4/5 in biopsies and Prostate Imaging-Reporting and Data System category 4/5 in MRI results. The concordance of tumor location lobe and positive lymph node side with the performance of tumor location-guided ePLND for positive lymph node detection was evaluated. RESULTS: For 301 patients who underwent ePLND at Kyushu University Hospital, tumor locations determined by biopsy and MRI findings showed no lesion in 8 (2.7%) patients, unilateral lobe in 223 (74.1%) patients, and bilateral lobe in 70 (23.3%) patients. The accuracies for detection of any and all positive lymph nodes by tumor location-guided unilateral ePLND were 99.6% and 97.3%, respectively. Among the patients at St. Luke's International Hospital, the accuracies for detection of any and all positive lymph nodes by tumor location-guided unilateral ePLND were estimated to be 99.0% and 97.3%, respectively. CONCLUSIONS: This study proposed tumor location-guided ePLND according to biopsy and MRI findings. This novel strategy is expected to reduce the burden of bilateral ePLND at the cost of acceptable risk of failing to detect positive lymph nodes.

Optimal interval for delayed retrieval surgery with reciprocating morcellators after enucleation of giant prostatic hyperplasia in holmium laser enucleation of the prostate.

Objective: The aim of this research was to evaluate the efficiency of reciprocating morcellation for removing giant benign prostatic hyperplasia during holmium laser enucleation of the prostate, investigate whether performing morcellation as a two-stage procedure improves tissue retrieval efficiency, and seek to determine the optimal interval between the two surgeries. Methods: This study included nine cases of holmium laser enucleation of the prostate with an enucleated prostate weight exceeding 200 g, indicative of substantial prostate enlargement. Morcellation was performed on Day 0 (n=4), Day 4 (n=1), Day 6 (n=1), and Day 7 (n=3). The intervals were compared regarding the morcellation efficiency, beach ball presence, and pathology. Results: The mean estimated prostate volume was 383 (range 330-528) mL; the median enucleation weight was 252 (interquartile range [IQR] 222, 342) g; and the median enucleation time was 83 (IQR 62, 100) min. The mean morcellation efficiency was 1.44 (SD 0.55) g/min on Day 0 and 13.69 (SD 2.46) g/min on day 7. The morcellation efficiency was 4.15 g/min and 10.50 g/min on Day 4 and Day 6, respectively, with significantly higher in the two-stage group compared to one-stage group (11.0 g/min vs. 1.5 g/min; p=0.014). Efficiency was strongly correlated with intervals (p<0.001); the incidences of beach balls were 100% (4/4) and 60% (3/5) in the immediate and two-stage surgery groups, respectively. Conclusion: The efficiency of two-stage morcellation with reciprocating morcellators was highly related to the postoperative interval, with the maximum efficiency reached on Day 7.

Holmium laser enucleation of the prostate as a secondary surgery following prostatic urethral lift.

Introduction: Prostatic urethral lift is a treatment option for benign prostatic hyperplasia, yet information on surgeries following this procedure is scarce. Case presentation: A 71-year-old man with persistent urinary retention following prostatic urethral lift underwent a secondary holmium laser enucleation of the prostate. The morcellation procedure, complicated by the presence of implants from the previous surgery, broke the morcellator blade. The fragmented blade was successfully retrieved without any organ damage. Postoperatively, the patient encountered no complications and showed improvement in his urinary symptoms. Conclusion: This case highlights the potential risk of device breakage when a secondary surgery, specifically the morcellation process, is performed following prostatic urethral lift. Care must be taken to prevent interaction between the implants and the morcellator. Our case demonstrates the efficacy of holmium laser enucleation of the prostate as a salvage surgical intervention for patients in whom prostatic urethral lift has failed.

Leiomyoma of the Prostate Treated via Holmium Laser Enucleation: A Case Report and Literature Review.

Leiomyoma is a rare tumor that arises from mesenchymal cells, with few reported cases of treatment using holmium laser enucleation of the prostate. A 74-year-old man with dysuria had a mass near the bladder neck in magnetic resonance imaging; this entity was suspected to be a leiomyoma. The patient underwent holmium laser enucleation of the prostate and one lobe was removed. However, the mass was firm and morcellation was difficult to break into small pieces. Therefore, it was fragmented via trans-urethral resection and removed with a curette. The postoperative course was favorable, with a positive clinical outcome. This case highlights the efficacy of holmium laser enucleation of the prostate in the management of prostatic leiomyoma and emphasizes its importance as a viable treatment option.

Simplified approach to the medial internal iliac region using a uretero-hypogastric nerve fascia development procedure for extended pelvic lymph node dissection during robot-assisted radical prostatectomy for high-risk prostate cancer.

INTRODUCTION: Although several clinical guidelines for prostate cancer (PC) recommend extended pelvic lymph node dissection (ePLND) during radical prostatectomy for high-risk cases, there are several issues to consider, including certain technical aspects. A simplified approach to the medial internal iliac region and paravesical arteries has not been established. The uretero-hypogastric nerve fascia (UHF) envelopes the ureter, hypogastric nerve, and pelvic autonomic nerves. To preserve the UHF, it is possible to approach the medial side of the internal iliac vessels without injuring any important tissue. We analyzed technical feasibility and lymph node (LN) yields. PATIENTS AND METHODS: After obtaining institutional review board approval, 265 high-risk PC patients with ePLND were identified. A da Vinci S or Xi robotic surgical system (Intuitive Surgical, Sunnyvale, CA, USA) was used. We divided the patients into conventional (non-UHF) method and modified (UHF) groups. The numbers of LNs removed, procedure-related complications, and surgical outcomes were analyzed. RESULTS: The median number of LNs removed was 19.0 in the non-UHF group and 22.0 in the UHF group (p = 0.004). Significantly more LNs were removed from the internal iliac region in the UHF group (p = 0.042). There was no difference in overall operative, console, or LN dissection time, or the severe complication rate (Clavien-Dindo grade ≥ III), between the non-UHF and UHF groups. CONCLUSIONS: Our simplified approach using the UHF development technique is technically feasible, has no major complications, and allows for the removal of significantly more LNs compared with the conventional method.

Peritoneal invasion of prostate cancer directly confirmed during robot-assisted radical prostatectomy.

Introduction: Several studies have been published on direct rectal invasion in patients with advanced metastatic prostate cancer, but few have directly confirmed intraoperative invasion of prostate cancer into the peritoneum. Case presentation: We report the case of a 73-year-old man with prostate cancer who exhibited peritoneal invasion during robot-assisted radical prostatectomy. His prostate-specific antigen level fell to 0.38 ng/mL after surgery; he was therefore prescribed radiation and androgen-deprivation therapies that controlled the cancer for more than 1 year. Conclusions: We encountered a case showing direct peritoneal invasion of prostate cancer during robot-assisted radical prostatectomy. If invasion of the seminal vesicle is suspected, the vesicorectal fossa should be examined during robot-assisted radical prostatectomy. Preoperative confirmation by diffusion magnetic resonance imaging of the peritoneum is also useful.

Long-term results after robot-assisted radical prostatectomy of a simplified inguinal hernia prevention technique without artificial substance use.

INTRODUCTION: Durable techniques that prevent postoperative inguinal hernia (IH) after robot-assisted radical prostatectomy (RARP) have not been established. This study evaluated the long-term efficacy of a postoperative IH prevention technique that uses no artificial agents to assess the characteristics of IH occurrence after introducing this technique. PATIENTS AND METHODS: We retrospectively analyzed 201 consecutive patients who underwent RARP at our institution between September 2011 and February 2014. In total, 189 cases were eligible for the study. The non-IH prevention and IH prevention groups comprised 72 and 117 cases, respectively. We compared the incidence of IH between the two groups using Kaplan-Meier curves. Risk factors for IH in the prevention group were determined via multivariable logistic regression analysis. RESULTS: The rate of IH occurrence was 20.8% (15 cases) in the nonprevention group and 8.5% (10 cases) in the prevention group, with median follow-up periods of 99.5 and 89.9 months, respectively. The Kaplan-Meier curves indicated a significant difference between the two groups (p = 0.011). Only cutting of the vas deferens significantly contributed to reduced occurrence of IH in multivariable analysis (p = 0.047). After reviewing the intraoperative videos, insufficient separation of the vas deferens was considered the main cause of IH in the prevention group. CONCLUSION: Our simple prevention technique with no artificial agents had a durable effect on IH prevention after RARP over a median follow-up period of more than 7 years. Cutting the vas deferens effectively prevented IH after RARP.

Focal xanthogranulomatous inflammation of the kidney cyst without pyelitis: a rare presentation mimicking kidney cancer.

Xanthogranulomatous pyelonephritis (XGP) is one of the most common granulomatous diseases of the kidney. XGP is subdivided into diffuse, segmental, and focal subtypes. Preoperative diagnosis of focal XGP on radiological imaging can be challenging, especially without involvement of the renal pelvis. Here, we report the case of a 61 year-old male with focal xanthogranulomatous inflammation of the kidney without pyelitis. The lesion presented as a mural nodule on the left renal cortical cyst, and kidney cancer was suspected on the preoperative image. The patient underwent a successful partial nephrectomy. Pathological examination revealed that the mural nodule displayed xanthogranulomatous inflammation and was clearly distinct from the renal pelvis. Thus, it should be considered that a mural nodule in a renal cortical cyst could be xanthogranulomatous inflammation.

Robot-assisted partial nephrectomy with minimum follow-up of 5 years: A multi-center prospective study in Japan.

OBJECTIVES: Robot-assisted partial nephrectomy is widely performed for small renal masses, achieving excellent perioperative and intermediate oncological outcomes. However, long-term oncological, functional, and quality of life outcomes after robot-assisted partial nephrectomy remain unclear. In this study, we aimed to evaluate quality of life at 1 year and oncological and functional outcomes of robot-assisted partial nephrectomy after a minimum follow-up of 5 years. METHODS: Personal, perioperative, postoperative, functional, oncological, and quality of life data were evaluated. The EQ-5D-5L tool, which incorporates health profiles and a EuroQol Visual Analog Scale, was used to assess quality of life preoperatively and 365 days postoperatively. Regarding oncological and functional outcomes, overall survival, recurrence-free survival, and changes in estimated glomerular filtration rate were calculated. RESULTS: There were few changes in levels between the two time points for all EQ-5D dimensions. The mean change in EQ-5D-5L was 0.020 (95% confidence interval 0.006-0.033, P = 0.006), and in EuroQol Visual Analog Scale score 4.60 (95% confidence interval 2.17-7.02, P = 0.0003). Overall and recurrence-free survival 5 years after robot-assisted partial nephrectomy were 97.9% and 92.8%, respectively. After an early postoperative decrease, the estimated glomerular filtration rate remained stable over time. CONCLUSIONS: Robot-assisted partial nephrectomy in patients with a T1 renal tumor is safe, feasible, and effective from the perspective of quality of life and survival, even after 5 years. When making treatment decisions, perioperative and quality of life outcomes should be considered together with long-term oncological outcomes.

Testicular metastasis from urothelial carcinoma of the bladder.

INTRODUCTION: Reports of urothelial carcinoma with testicular metastasis are limited and the etiology and prognosis remain unclear. We report a rare case of testicular metastasis derived from bladder urothelial carcinoma. CASE PRESENTATION: A 68-year-old man presented with gross hematuria and urinary frequency. Cystoscopy demonstrated an 8-cm-sized tumor in the bladder; transurethral resection and magnetic resonance imaging confirmed invasive urothelial carcinoma. Cystoprostatourethrectomy was performed, and the pathological diagnosis was high-grade muscle-invasive urothelial carcinoma. Three years later, the patient noticed a left scrotal mass. Left high orchiectomy was performed, and histopathologic examination of the surgical specimen revealed urothelial carcinoma, confirming testicular metastasis derived from bladder cancer. The patient received chemotherapy with gemcitabine and cisplatin and has survived for 7 years since the initial diagnosis without progression. CONCLUSION: Although rare, secondary lesions should be considered for the differential diagnosis of testicular tumors in patients with a history of urothelial carcinoma.

Late-onset Hem-o-Lok® migration into the bladder after robot-assisted radical prostatectomy.

INTRODUCTION: Hem-o-Lok® clips are widely used in robot-assisted radical prostatectomy because of their ease of application and secure clamping. Although there have been some reports of their migration into the urinary tract, this usually occurs a few months after robot-assisted radical prostatectomy. Late-onset cases of Hem-o-Lok® clip migration, that is, after more than 1 year, are rare. CASE PRESENTATIONS: We report three cases of delayed endourethral Hem-o-Lok® clip migration more than 2 years after robot-assisted radical prostatectomy. The Hem-o-Lok® clips were almost completely endoluminal, and were attached at one end to the vesicourethral anastomosis. We successfully removed them via transurethral surgery using a holmium laser. CONCLUSION: This case series describes late-onset Hem-o-Lok® clip migration into the bladder more than 1 year after robot-assisted radical prostatectomy. Transurethral holmium laser surgery was very effective for Hem-o-Lok® clip removal. To avoid involvement of Hem-o-Lok® clips in the vesicourethral anastomosis, appropriate resection at the time of bladder neck transection is important.

[A Case of Multiple Renal Carcinomas with Three Different Subtypes].

We report a case of dialysis kidney with multiple renal carcinomas in three locations. A 74-year-old man who had a 20-year history of dialysis, was admitted to our hospital complaining of sudden right lateral area pain. Computed tomography (CT) scan revealed hemorrhage from the right dialyzed renal subcapsule. He underwent immediate transcatheter arterial embolization (TAE), but after 6 days the CT scan showed new active bleeding. A second TAE was performed, but, the CT scan several days later showed hemorrhage from the same site. So we decided to perform a right radical nephrectomy. Pathological results revealed three different renal carcinomas at sites different from the bleeding site. The presence of triple carcinomas in the same organ of the kidney is quite rare. Because of the high incidence of renal carcinoma associated with polycystic kidney disease in long-term hemodialysis patients and the possibility of multiple carcinomas as in this case, radical nephrectomy is recommended even in the case of spontaneous rupture.

Prostate cancer featuring a unique progression pattern: A case of prominent direct perineal invasion without definite metastasis.

Locally advanced prostate cancer can extend into the pelvis, and can also invade the bladder and rectum. We encountered a patient with prostate cancer that exhibited severe local invasion, protruding into the perineum. Distant metastasis was absent, despite the large tumor size. The tumor bled and caused difficulty sitting and standing, compromising the patient's quality of life. Total pelvic exenteration and chemotherapy were considered, but the patient's general condition rendered these therapies inappropriate. However, of the limited treatment options available given the patient's condition, palliative irradiation of the protruding region proved effective.

A large adrenocortical adenoma surrounded with a renal arteriovenous malformation.

INTRODUCTION: Large adrenal adenomas are clinically rare. We report a case of a large adrenal adenoma with a renal arteriovenous malformation, mimicking a malignant adrenal tumor in preoperative imaging. CASE PRESENTATION: A 66-year-old woman presented to a local hospital with abdominal pain. A right adrenal tumor was detected, 66 mm in diameter and surrounded by thick and tortuous vessels. Based on the imaging findings, pheochromocytoma was suspected. However, clinical symptoms and endocrine abnormalities were absent, and radionuclide accumulation in scintigraphy was negative. Laparoscopic right adrenalectomy was performed. Intraoperatively, a notable growth of vessels forming a nidus surrounding the tumor was observed. Pathologically, this was diagnosed as an adrenocortical adenoma in conjunction with a renal arteriovenous malformation. CONCLUSION: We report a case of a large adrenal tumor surrounded with an arteriovenous malformation. To the best of our knowledge, this is the first reported case of this combination.

Positive urine culture under indwelling urethral catheterization is a risk factor for febrile complications after holmium laser enucleation of the prostate (HoLEP).

OBJECTIVES: To investigate the incidence of and risk factors for febrile complications (FCs) in patients undergoing holmium laser enucleation of the prostate (HoLEP). METHODS: This retrospective study enrolled 847 consecutive patients who underwent HoLEP in our hospital from June 2006 to December 2018. FCs were defined as a body temperature ≥38.0°C within 30 days after surgery. The incidence of FCs was determined and possible risk factors assessed using multivariate logistic regression analysis. RESULTS: Overall, 87 (10.3%) patients presented with FCs, and 6 (0.7%) had urosepsis, with no fatal complications. Multivariate logistic regression analysis revealed that patients with preoperative positive urine culture and urethral catheterization had an increased risk of FCs compared with those with a negative culture who did not need catheterization (odds ratio [OR] 2.587, 95% confidence interval [CI] 1.307-5.121). A negative urine culture with catheterization and a positive culture without catheterization were not associated with the development of FCs (OR 0.320, 95% CI 0.040-2.553 and OR 1.370, 95% CI 0.662-2.365, respectively). Other significant risk factors included preoperative serum albumin levels (OR 0.382, 95% CI 0.173-0.846) and immediate postoperative body temperature (OR 2.559, 95% CI 1.549-4.230). CONCLUSIONS: FCs are relatively common among patients after HoLEP despite preoperative prophylactic antibiotic administration. Surgeons may need to consider performing screening of urine cultures prior to HoLEP, especially in patients with urethral catheterization, even if asymptomatic. If the culture is positive, prophylactic antibiotics should be tailored according to bacterial susceptibility.

Optimizing first trocar access for robot-assisted radical prostatectomy: Optical trocar access through the upper abdominal quadrant using the Kii Fios First Entry trocar.

OBJECTIVES: A pre-equipped metal trocar is required to use as a camera trocar due to a specification change in the da Vinci X/Xi system (Intuitive Surgical). We observed slight slippage of a trocar placed by the open method. With optical trocar access (OTA), the initial trocar is viewed directly with a laparoscope during placement. Reports regarding OTA for robotic surgery are limited, particularly for robot-assisted radical prostatectomy (RARP). We modified the OTA procedure such that it was appropriate for RARP. PATIENTS AND METHODS: A total of 158 patients were enrolled in this study. The first trocar placement time (FTPT) was compared between the open and OTA groups. In the OTA group, the trocar was mainly placed through the upper abdominal quadrant. We also analyzed the differences between the conventional and modified OTA procedures using the Kii Fios First Entry trocar (Applied Medical). We examined the factors affecting the FTPT using linear regression models. A P value <.05 was considered significant. RESULTS: The FTPT was significantly shorter in the OTA group than the open group (P < .0001). The modified method was associated with a shorter FTPT (P = .0001). None of the patient characteristics affected the FTPT in either group. No major complications were observed. CONCLUSIONS: OTA was applied successfully during RARP. Use of the Kii Fios First Entry trocar with upper abdominal quadrant placement was suitable for RARP.

Association between prostate cancer characteristics and BRCA1/2-associated family cancer history in a Japanese cohort.

In addition to breast, ovarian, and pancreatic cancers, BRCA1/2 genes have been associated with prostate cancer (PC). However, the role of BRCA1/2-associated family cancer history (FCH) has remained unexplored in treating these four cancer types as a homogenous pathophysiological group. We aimed to clarify the relationship between BRCA1/2-associated FCH and PC, and to assess its relationship with cancer aggressiveness. Patient characteristics, positive family history of BRCA1/2-associated cancer, and cancer characteristics (Gleason score, prostate specific antigen level at diagnosis, and clinical tumor stage) were analyzed. Among the 1,985 eligible candidates, 473 (23.83%) patients had adequately detailed FCH, obtained via questionnaire, and were thus included in the study. BRCA1/2-associated FCH was observed in 135 (28.54%) patients with PC (68, 14.38%), breast (44, 9.30%), pancreatic (31, 6.55%), or ovarian (8, 1.69%) cancers. BRCA1/2-associated FCH was not significantly associated with high Gleason score (≥ 8). Patients with BRCA-associated FCH were less likely to present with high clinical tumor stage, and no difference was observed in prostate-specific antigen level, presence of metastatic lesions at diagnosis, or likelihood of high-risk classification between patients with and without BRCA-associated FCH. This is the first report of BRCA1/2-associated FCH in Japanese men, indicating that family history did not affect the severity or aggressiveness of PC.

One-surgeon basketing technique for stone extraction during flexible ureteroscopy for urolithiasis: A comparison between novice and expert surgeons.

OBJECTIVE: To determine the safety and efficacy of the one-surgeon basketing technique for stone extraction during flexible ureteroscopy when carried out by novice surgeons under instructor guidance. METHODS: We retrospectively compared perioperative results, complications and the "stone-free" rate (defined as ≤2 mm fragments on kidney-ureter-bladder imaging 1 month after flexible ureteroscopy) between experienced (group A, n = 50) and novice (group B, n = 50) surgeons using the one-surgeon basketing technique. RESULTS: Baseline patients' characteristics were similar between the two groups. There were no significant differences between groups A and B in operative time (mean 76 min vs 85 min, P = 0.46), stone-free rate (98% vs 92%, P = 0.36), postoperative fever events (4% vs 4%, P = 1.00) and postoperative hospital stay (24 h vs 24 h, P = 1.00). Clavien-Dindo grade IIIa complications (ureter injury) were only observed in two cases (4%) in group B. CONCLUSIONS: The one-surgeon basketing technique for the extraction of stone fragments during flexible ureteroscopy might be safely and effectively carried out by surgeons with no prior experience under proper guidance.

Impact of indocyanine green-guided extended pelvic lymph node dissection during robot-assisted radical prostatectomy.

OBJECTIVES: To evaluate the effectiveness of indocyanine green-guided extended pelvic lymph node dissection during robot-assisted radical prostatectomy for intermediate- to high-risk prostate cancer. MATERIALS AND METHODS: After institutional review board approval, between July 2017 and December 2018, we carried out 100 indocyanine green-guided extended pelvic lymph node dissections in patients with localized intermediate- and high-risk prostate cancer, using the Firefly (Novadaq Technologies, Mississauga, ON, Canada) and da Vinci Xi surgical system (Intuitive Surgical, Sunnyvale, CA, USA). Indocyanine green was injected transrectally using ultrasound sonography before each surgery. Then, lymphatic drainage patterns and pathological findings were recorded. RESULTS: Lymphatic drainage routes were successfully determined in 91 right-sided and 90 left-sided cases. Five main lymphatic pathways and sites were identified: (i) an internal route (57%); (ii) a lateral route (50%); (iii) a presacral route (20%); (iv) a paravesical artery site (20%); and (v) a pre-prostatic site (5%). Lymph node metastasis was positive in 15 patients, with 44 pathologically confirmed metastatic lymph nodes. Metastatic fluorescent lymph nodes were found in 15 out of 44 lymph nodes (34.1%). For sentinel lymph node identification, the 34% sensitivity and 64.8% specificity rates were detected in regard to identification of lymph node metastasis. CONCLUSIONS: Lymphatic drainage patterns from the prostate can be identified and classified using indocyanine green-guided extended pelvic lymph node dissections. Although the direct role of fluorescent lymph nodes in sentinel lymph node identification appears to be limited, the identification of lymphatic pathways could contribute to high-quality extended pelvic lymph node dissection during robot-assisted radical prostatectomy.

The Use of Cumulative Sum Analysis to Derive Institutional and Surgeon-Specific Learning Curves for Robot-Assisted Radical Prostatectomy.

Purpose: The cumulative sum (CUSUM) approach has been adopted to evaluate surgical competence in various contexts. The CUSUM method comprises sequential monitoring of cumulative differences from a target level in performance quality over time, allowing the detection of deviations from the target. We use the CUSUM method in this study to derive both institutional and surgeon-specific learning curves for robot-assisted radical prostatectomy (RARP). Patients and Methods: We reviewed 540 patients diagnosed with localized prostate cancer (pathologic stage T2) who underwent RARP at our institution between September 2011 and December 2017. The CUSUM method was used to construct both institutional and individual-surgeon learning curves; the outcome was assessed based on whether a positive surgical margin (PSM) was present. The target PSM rate was 20%. Of seven surgeons performing robot-assisted resections for this period, four who performed ≥60 resections were assessed separately. Results: Of 540 patients, 74 (14%) had PSMs. The institutional CUSUM chart exhibited a downward trend for the first 54 cases and an upward trend thereafter. The CUSUM chart for the earliest adopter was similar to that for the institution; that is, learning was complete at 45 cases. Two adopters did not undergo a learning curve as they consistently performed well. The last adopter required 10 cases for initial learning. However, his CUSUM chart trend became negative at 46 cases and remained so afterward. Conclusions: CUSUM charts are useful for monitoring surgical quality. Long-term monitoring of the PSM rate of a surgeon who has become independent allows an attending surgeon to intervene if necessary; thus, long-term quality control is assured.