Percutaneous renal access: tips and tricks

Percutaneous nephrolithotomy vs retrograde intrarenal surgery for renal stones: a Cochrane Review

OBJECTIVES

To assess the effects of percutaneous nephrolithotomy (PCNL) vs retrograde intrarenal surgery (RIRS) for the treatment of renal stones in adults.

METHODS

We performed a comprehensive search of the Cochrane Library, MEDLINE, Embase, three other databases, trials registries, other sources of the grey literature, and conference proceedings up to 23 March 2023. We applied no restrictions on publication language or status. Screening, data extraction, risk-of-bias assessment, and certainty of evidence (CoE) rating using the Grading of Recommendations Assessment, Development and Evaluations (GRADE) approach were done in duplicate by two independent reviewers. This co-publication focuses on the primary outcomes of this review only.

RESULTS

We included 42 trials that met the inclusion criteria. Stone-free rate (SFR): PCNL may improve SFRs (risk ratio [RR] 1.13, 95% confidence interval [CI] 1.08-1.18; I2 = 71%; 39 studies, 4088 participants; low CoE). Major complications: PCNL probably has little to no effect on major complications (RR 0.86, 95% CI 0.59-1.25; I2 = 15%; 34 studies, 3649; participants; moderate CoE) compared to RIRS. Need for secondary interventions: PCNL may reduce the need for secondary interventions (RR 0.31, 95% CI 0.17-0.55; I2 = 61%; 21 studies, 2005 participants; low CoE) compared to RIRS.

CONCLUSION

Despite shortcomings in most studies that lowered our certainty in the estimates of effect to mostly very low or low, we found that PCNL may improve SFRs and reduce the need for secondary interventions while not impacting major complications. Ureteric stricture rates may be similar compared to RIRS. We expect the findings of this review to be helpful for shared decision-making about management choices for individuals with renal stones.

Percutaneous nephrolithotomy versus retrograde intrarenal surgery for treatment of renal stones in adults

BACKGROUND

Kidney stones (also called renal stones) can be a source of pain, obstruction, and infection. Depending on size, location, composition, and other patient factors, the treatment of kidney stones can involve observation, shock wave lithotripsy, retrograde intrarenal surgery (RIRS; i.e. ureteroscopic approaches), percutaneous nephrolithotomy (PCNL), or a combination of these approaches.

OBJECTIVES

To assess the effects of percutaneous nephrolithotomy (PCNL) versus retrograde intrarenal surgery (RIRS) for the treatment of renal stones in adults.

SEARCH METHODS

We performed a comprehensive search of the Cochrane Library, MEDLINE, Embase, Scopus, and two trials registries up to 23 March 2023. We applied no restrictions on publication language or status.

SELECTION CRITERIA

We included randomized controlled trials that evaluated PCNL (grouped by access size in French gauge [Fr] into three groups: ≥ 24 Fr [standard PCNL], 15-23 Fr [mini-PCNL and minimally invasive PCNL], and < 15 Fr [ultra-mini-, mini-micro-, super-mini-, and micro-PCNL]) versus RIRS.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and extracted data from the included studies. Our primary outcomes were stone-free rate, major complications, and need for secondary interventions. Our main secondary outcomes were unplanned medical visits to emergency/urgent care or outpatient clinic, length of hospital stay, ureteral stricture or injury, and quality of life. We performed statistical analyses using a random-effects model. We rated the certainty of evidence using GRADE criteria. We adopted a minimally contextualized approach with predefined thresholds for minimal clinically important differences (MCIDs).

MAIN RESULTS

We included 42 trials assessing the effects of PCNL versus RIRS in 4571 randomized participants. Twenty-two studies were published as full-text articles, and 20 were published as abstract proceedings. The average size of stones ranged from 10.1 mm to 39.1 mm. Most studies did not report sources of funding or conflicts of interest. The main results for the most important outcomes are summarized below. Stone-free rate PCNL compared with RIRS may improve stone-free rates (risk ratio [RR] 1.13, 95% confidence interval [CI] 1.08 to 1.18; I2 = 71%; 39 studies, 4088 participants; low-certainty evidence). Based on 770 participants per 1000 being stone-free with RIRS, this corresponds to 100 more (62 more to 139 more) stone-free participants per 1000 with PCNL (an absolute difference of 10%, where the predefined MCID was 5%). Major complications PCNL compared with RIRS probably has little or no effect on major complications (RR 0.86, 95% CI 0.59 to 1.25; I2 = 15%; 34 studies, 3649 participants; moderate-certainty evidence). Based on 31 complications in the RIRS group, this corresponds to six fewer (13 fewer to six more) major complications per 1000 with PCNL (an absolute difference of 0.6%, where the predefined MCID was 2%). Need for secondary interventions PCNL compared with RIRS may reduce the need for secondary interventions (RR 0.31, 95% CI 0.17 to 0.55; I2 = 61%; 21 studies, 2005 participants; low-certainty evidence). Based on 222 secondary interventions in the RIRS group, this corresponds to 153 fewer (185 fewer to 100 fewer) secondary interventions per 1000 with PCNL (an absolute difference of 15.3%, where the predefined MCID was 5%). Unplanned medical visits No studies reported unplanned medical visits. Length of hospital stay PCNL compared with RIRS may extend length of hospital stay (mean difference 1.04 days more, 95% CI 0.27 more to 1.81 more; I2 = 100%; 26 studies, 2804 participants; low-certainty evidence). This effect size is greater than the predefined MCID of one day. Ureteral stricture or injury PCNL compared with RIRS may have little or no effect on the occurrence of ureteral strictures (RR 0.93, 95% CI 0.39 to 2.21; I2 = 0%; 13 studies, 1574 participants; low-certainty evidence). Based on 14 ureteral strictures in the RIRS group, this corresponds to one fewer (nine fewer to 17 more) ureteral strictures per 1000 with PCNL (an absolute difference of 0.1%, where the predefined MCID was 2%). Quality of life No studies reported quality of life.

AUTHORS' CONCLUSIONS

Based on a large body of evidence from 42 trials, we found that PCNL compared with RIRS may improve stone-free rates and may reduce the need for secondary interventions, but probably has little or no effect on major complications. PCNL compared with RIRS may have little or no effect on ureteral stricture rates and may increase length of hospital stay. We found no evidence on unplanned medical visits or participant quality of life. Because of the considerable shortcomings of the included trials, the evidence for most outcomes was of low certainty. Access size for PCNL was less than 24 Fr in most studies that provided this information. We expect the findings of this review to be helpful for shared decision-making about management choices for individuals with renal stones.

Tranexamic acid for percutaneous nephrolithotomy

BACKGROUND

Percutaneous nephrolithotomy (PCNL) is the gold standard for the treatment of large kidney stones but comes with an increased risk of bleeding compared to other treatments, such as ureteroscopy and shock wave lithotripsy. Tranexamic acid (TXA) is an antifibrinolytic agent that has been used to reduce bleeding complications in other settings.

OBJECTIVES

To assess the effects of TXA in individuals with kidney stones undergoing PCNL.

SEARCH METHODS

We performed a comprehensive literature search of the Cochrane Library, PubMed (including MEDLINE), Embase, Scopus, Global Index Medicus, trials registries, other sources of the grey literature, and conference proceedings. We applied no restrictions on the language of publication nor publication status. The latest search date was 11 May 2023.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared treatment with PCNL with administration of TXA to placebo (or no TXA) for patients ≥ 18 years old.

DATA COLLECTION AND ANALYSIS

Two review authors independently classified studies and abstracted data. Primary outcomes were: blood transfusion, stone-free rate (SFR), and thromboembolic events (TEEs). Secondary outcomes were: adverse events (AEs), secondary interventions, major surgical complications, minor surgical complications, unplanned hospitalizations or readmissions, and hospital length of stay (LOS). We performed statistical analyzes using a random-effects model. We rated the certainty of evidence (CoE) according to the GRADE approach using a minimally contextualized approach with predefined thresholds for minimally clinically important differences (MCIDs).

MAIN RESULTS

We analyzed 10 RCTs assessing the effect of systemic TXA in PCNL versus placebo (or no TXA) with 1883 randomized participants. Eight studies were published as full text. One was published in abstract proceedings, but it was separated into two separate studies for the purpose of our analyzes. Average stone surface area ranged 3.45 to 6.62 cm2. We also found a single RCT published in full text assessing the effects of topical TXA in PCNL versus placebo (or no TXA) with 400 randomized participants, the results of which are further described in the review. Here we focus only on the results of TXA used systemically. Blood transfusion - Based on a representative baseline risk of 5.7% for blood transfusions taken from a large presentative observational studies, systemic TXA may reduce blood transfusions (risk ratio (RR) 0.45, 95% confidence interval (CI) 0.27 to 0.76; I2 = 28%; 9 studies, 1353 participants; low CoE). We assumed an MCID of ≥ 2%. Based on 57 participants per 1000 with placebo (or no TXA) being transfused, this corresponds to 31 fewer (from 42 fewer to 14 fewer) participants being transfused per 1000. Stone-free rate - Based on a representative baseline risk of 75.7% for SFR, systemic TXA may increase SFRs (RR 1.11, 95% CI 0.98 to 1.27; I2 = 62%; 4 studies, 603 participants; low CoE). We assumed an MCID of ≥ 5%. Based on 757 participants per 1000 being stone free with placebo (or no TXA), this corresponds to 83 more (from 15 fewer to 204 more) stone-free participants per 1000. Thromboembolic events - There is probably no difference in TEEs (risk difference (RD) 0.00, 95% CI -0.01 to 0.01; I2 = 0%; 6 studies, 841 participants; moderate CoE). We assumed an MCID of ≥ 2%. Since there were no thromboembolic events in intervention and/or control groups in 5 out of6 studies, we opted to assess a risk difference with systemic TXA for this outcome. Adverse events - Systemic TXA may increase AEs (RR 5.22, 95% CI 0.52 to 52.72; I2 = 75%; 4 studies, 602 participants; low CoE). We assumed an MCID of ≥ 5%. Based on 23 participants per 1000 with placebo (or no TXA) having an adverse event, this corresponds to 98 more (from 11 fewer to 1000 more) participants with adverse events per 1000. Secondary interventions - Systemic TXA may have little to no effect on secondary interventions (RR 1.15, 95% CI 0.84 to 1.57; I2 = 0%; 2 studies, 319 participants; low CoE). We assumed an MCID of ≥ 5%. Based on 278 participants per 1000 with placebo (or no TXA) having a secondary intervention, this corresponds to 42 more (from 44 fewer to 158 more) participants with secondary interventions per 1000. Major surgical complications - Based on a representative baseline risk for major surgical complications of 4.1%, systemic TXA may reduce major surgical complications (RR 0.36, 95% CI 0.21 to 0.62; I2 = 0%; 5 studies, 733 participants; moderate CoE). We assumed an MCID of ≥ 2%. Based on 41 participants per 1000 with placebo (or no TXA) having a major surgical complication, this corresponds to 26 fewer (from 32 fewer to 16 fewer) participants with major surgical complications per 1000. Minor surgical complications - Systemic TXA may reduce minor surgical complications (RR 0.71, 95% CI 0.45 to 1.10; I2 = 76%; 5 studies, 733 participants; low CoE). We assumed an MCID of ≥ 5%. Based on 396 participants per 1000 with placebo (or no TXA) having a minor surgical complication, this corresponds to 115 fewer (from 218 fewer to 40 more) participants with minor surgical complications per 1000. Unplanned hospitalizations or readmissions - We are very uncertain how unplanned hospitalizations or readmissions are affected (RR 1.55, 95% CI 0.45 to 5.31; I2 = not applicable; 1 study, 189 participants; very low CoE). We assumed an MCID of ≥ 2%. Hospital length of stay - Systemic TXA may reduce hospital LOS (mean difference 0.52 days lower, 95% CI 0.93 lower to 0.11 lower; I2 = 98%; 7 studies, 1151 participants; low CoE). We assumed an MCID of ≥ 0.5 days.

AUTHORS' CONCLUSIONS

Based on 10 RCTs with substantial methodological limitations that lowered all CoE of effect, we found that systemic TXA in PCNL may reduce blood transfusions, major and minor surgical complications, and hospital LOS, as well as improve SFRs; however, it may increase AEs. We are uncertain about the effects of systemic TXA on other outcomes. Findings of this review should assist urologists and their patients in making informed decisions about the use of TXA in the setting of PCNL.

Supra-costal tubeless percutaneous nephrolithotomy is not associated with increased complication rate: a prospective study of safety and efficacy of supra-costal versus sub-costal access

Background

To assess the morbidities of tubeless percutaneous nephrolithotomy (PCNL) using supra-costal access and re-evaluate traditional concept of increased complications with supra-costal access.

Methods

From January 2010 to December 2014, a single surgeon performed 118 consecutive one-stage fluoroscopic guided PCNL’s for complex renal and upper ureteral stone. Our definition for complex renal stone is defined as partial or complete staghorn stone, multiple renal stones in more than 2 calyxes, obstructive uretero-pelvic stone > 2 cm, and a renal stone in single functional kidney. Inclusion criteria include: staghorn stones, renal calculi > 2 cm in diameter, upper ureteral stone > 1.5 cm in diameter. Exclusion criteria for tubeless PCNL include: significant bleeding or perforation of the collecting system, large residue stone, multiple PCNL tract and obstructive renal anatomy. Morbidity, operation time, analgesia requirement, length of hospital stay, stone- free rate, were analyzed.

Results

Of the 118 consecutive PCNL, eighty-six patients underwent tubeless PCNL (56 supra-costal and 30 sub-costal) and included in our prospective follow-up period. The mean age, operation side, stone locations were similar. The male to female ratio is higher in supra-costal than sub-costal. Large renal stones and staghorn stones makes up for most patients (supra-costal: 75%, sub-costal: 80%). The stone–free rate of supra-costal group was 59% (33/56) and in sub-costal group was 50% (15/30). The operative times, length of stay, post-op analgesic use, hematocrit change was similar in both groups. The overall complication rate is 6% [supra-costal (1/56), sub-costal (4/30)] with the majority being infectious complications.

Conclusions

Supra-costal access above 12th rib during tubeless PCNL is safe and effective procedure and is not associated with higher incidence of post-op complications in experience hands.

Validity of a sponge trainer as a simple training model for percutaneous renal access

Objective

To evaluate the efficacy of our simply designed trainer for junior urologists to acquire the initial skills for percutaneous renal access (PRA).

Subjects and methods

Three sponge sheets (60 × 50 × 10 cm) were arranged horizontally over each other. A rectangular groove was made in the middle sheet to accommodate an inflated balloon of a Foley catheter, radio-opaque metal balls, metal rings, or a plastic tube that were sequentially placed for the four training tasks. In each session, 18 trainees were asked to pass a fluoroscopically guided puncture needle from a surface point to the placed object in middle sheet. Clinical impact of training was evaluated by an experience survey on a 5-piont Likert scale (for model usefulness, tactile and fluoroscopic-guidance feedback) and success rate in further mentored practice.

Results

There was a gradual increase in tasks’ and sessions’ scores over the training sessions. According to the experience survey after first clinical practice, the mean (SD) score for overall model usefulness by trainees was 3.8 (0.9) with high fluoroscopic guidance reality [3.6 (1.1)] but poor tactile realism [2.3 (0.9)]. On mentored PRA, the success rate for trainees was 78.3%.

Conclusion

Our early evaluation showed our novel, cost-effective and reproducible sponge trainer could be an effective training model for PRA with a beneficial impact on subsequent clinical practice.

Transgluteal CT-Guided Percutaneous Renal Access for Percutaneous Nephrolithotomy in a Pelvic Horseshoe Kidney

CT-guided percutaneous renal access has been described as a safe and effective access technique in patients with complex anatomy, including ectopic kidney, retrorenal colon, spinal dysraphism, hepatomegaly, and splenomegaly. In comparison to conventional intraoperative fluoroscopic-guided access, CT imaging allows for delineation of surrounding structures that are at risk for injury during percutaneous access. However, previous reports indicate that pelvic kidneys might be inaccessible percutaneously without laparoscopic assistance. Herein, we present a novel transgluteal route to renal access for percutaneous nephrolithotomy (PCNL) in a patient with a pelvic horseshoe kidney and severe spinal deformity.

Initial experience of micro-percutaneous nephrolithotomy in the treatment of renal calculi in 140 renal units

The aim of this study was to investigate the effectiveness and reliability of the micro-percutaneous nephrolithotomy (PNL) method for the management of kidney stones. We performed a retrospective analysis of 136 patients (140 renal units) who underwent micro-PNL for renal stones between September 2011 and February 2013 in four referral hospitals in Turkey. The selection of treatment modality was primarily based on factors such as stone size and location. In this study, we analyzed patient- and procedure-related factors. The mean age of patients in this study was 28.7 ± 20.6 (1-69) years, and the mean stone size was 15.1 ± 5.15 (6-32) mm. Conversion to mini-PNL was required in 12 patients. All interventions were performed with the patient in the prone position, except for the 3-year-old patient with the pelvic kidney who was placed in the supine position. The mean hospital stay was 1.76 ± 0.65 (1-4) days, and the mean drop in the hemoglobin level was 0.87 ± 0.84 (0-4.1) mg/dL. One of our patients required transfusion. Ureteral J stent was implanted in nine (6.43 %) patients because of residual stones. Seven (6.43 %) patients complained of postoperative renal colic which was managed conservatively. Abdominal distension related to extravasation of the irrigation fluid was observed in three patients (2.19 %). There were no other postoperative complications. An overall success rate of 82.14 % was achieved. Micro-PNL can be effectively and safely used for small and moderate kidney stones resistant to shock wave lithotripsy or as an alternative to other minimally invasive treatment methods.

The 3-finger technique in establishing percutaneous renal access: a new and simple method for junior trainees

INTRODUCTION AND OBJECTIVES

Urology trainees may lack experience in gaining renal access during percutaneous nephrolithomy (PCNL). Establishing the correct depth of initial percutaneous needle insertion is one of the major obstacles. As such, we have identified an easy technique, which can be performed, to establish correct depth adjustment allowing easier access.

MATERIALS AND METHODS

An initial attempt is made to insert the percutaneous needle into the desired posterior calyx in the antero-posterior (AP) plane. If the needle does not traverse into the desired calyx immediately, it is concluded that the needle track must be too shallow or too deep. The C-arm is then rotated 20 to 30 degrees from the vertical, in the axial plane, towards the operating surgeon and, using the image intensifier, very careful note is made of the end of the needle in this plane, compared with the end of the needle initially in the AP plane, to see if it has moved "medially" or "laterally." The 3-finger technique is then performed by the surgeon, to establish if the needle path is too deep or too shallow. This technique is currently being performed by trainees under direct consultant supervision with 13 successful cases so far.

RESULTS

The 3-finger technique has been successfully used to demonstrate and teach PCNL access to urology trainees. In all 13 cases, percutaneous renal access was achieved successfully by trainees without immediate or late complications. Also, positive and encouraging feedbacks were received from those trainees, and all expressed willingness to continue using the same new technique in the future.

CONCLUSIONS

Our new technique is cheap, safe, easy to learn and use, and of particular benefit to junior trainees who are beginning to perform PCNL access.

Outpatient tubeless percutaneous nephrolithotomy: the initial case series

INTRODUCTION

Percutaneous nephrolithotomy (PCNL) has traditionally been performed on an inpatient basis. To the best of our knowledge, this is the first report of tubeless PCNL on a completely outpatient basis. The purposes of this study were to assess the safety and efficacy of outpatient PCNL.

METHODS

We reviewed the initial consecutive outpatient tubeless PCNLs performed at our institution by a single surgeon. Patients were discharged home the day of surgery only after meeting strict discharge criteria. Preoperative, intraoperative and postoperative data were collected prospectively.

RESULTS

Outpatient tubeless PCNL was performed in 3 patients. The mean maximum stone diameter was 14 mm. The average hospital stay was 175 minutes. All 3 patients were discharged home in stable condition after meeting all of the inclusion criteria. There were no emergency room visits or hospital readmissions postoperatively. The mean follow-up period was 47 days. All stones were calcium oxalate and the stone free rate was 100%. There were no minor or major complications.

CONCLUSION

In properly selected patients, outpatient tubeless PCNL is safe and effective. Our initial experience with outpatient PCNL has been favourable and warrants further investigation in a larger patient population.

Single-step percutaneous nephrolithotomy (microperc): the initial clinical report

PURPOSE

To our knowledge we report the first technical feasibility and safety study of 1-step percutaneous nephrolithotomy using the previously described 4.85Fr all-seeing needle (PolyDiagnost, Pfaffenhofen, Germany). We defined microperc as modified percutaneous nephrolithotomy in which renal access and percutaneous nephrolithotomy are done in 1 step using the all-seeing needle.

MATERIALS AND METHODS

Microperc was performed in 10 cases using the 4.85Fr all-seeing needle to achieve collecting system access under direct vision. Percutaneous nephrolithotomy was done through the same 16 gauge needle sheath with a 3-way connector allowing irrigation, and passage of a flexible telescope and a 200 μm holmium:YAG laser fiber. We prospectively analyzed preoperative, intraoperative and postoperative parameters.

RESULTS

Mean calculous size was 14.3 mm. Two of the 10 patients were of pediatric age, and 1 each had an ectopic pelvic kidney, chronic kidney disease and obesity. Microperc was feasible in all cases with mean ± SD surgeon visual analog score for access of 3.1 ± 1.2, a mean 1.4 ± 1.0 gm/dl hemoglobin decrease and a mean hospital stay of 2.3 ± 1.2 days. The stone-free rate at 1 month was 88.9%. In 1 patient intraoperative bleeding obscured vision, requiring conversion to mini percutaneous nephrolithotomy. There were no postoperative complications and no auxiliary procedures were required.

CONCLUSIONS

Microperc is technically feasible, safe and efficacious for small volume renal calculous disease. Further clinical studies and direct comparison with available modalities are required to define the place of microperc in the treatment of nonbulky renal urolithiasis.

Percutaneous nephrolithotomy in patients with spinal deformities

BACKGROUND AND PURPOSE

To assess the feasibility and efficacy of percutaneous nephrolithotomy (PCNL) in patients with spinal deformities.

PATIENTS AND METHODS

Between 1999 and 2008, eight patients (nine renal units) with spinal deformities underwent 10 PCNLs. Mean stone burden was 372 mm(2) (160-840 mm(2)). Preoperative investigation of the respiratory function, evaluation of anatomy by intravenous pyelography or CT spiral scan, and preoperative planning of the percutaneous access by ultrasonography (US) were performed in all patients. Patients were either in a prone (n = 5) or supine (n = 5) position during PCNL. US-guided fluoroscopic adjusted percutaneous puncture of the desired calix was performed in all the patients.

RESULTS

There was a 40% complication rate related to the number of procedures, with 20% of patients needing blood transfusion and 10% experiencing major complications. Complete stone clearance per kidney after one PCNL was 55.5% (5/9 PCNLs), increasing to 66.6% (6/9 PCNLs) after a second PCNL. Four of nine (44.4%) renal units needed additional procedures after one PCNL (shockwave lithotripsy [SWL], retrograde intrarenal surgery [RIRS], combined simultaneous PCNL and RIRS). At the 3-month follow-up, the overall stone-free rate was 88.8% (eight renal units).

CONCLUSION

PCNL in patients with spinal deformities is challenging. Accurate preoperative evaluation of the anatomy and respiratory function and a precise preoperative planning are mandatory. US-guided puncture of the collecting system permits avoiding visceral injury. Supine PCNL offers advantages in terms of patient comfort, protection of cardiorespiratory function, and the ability to perform a simultaneous combined ureteroscopic approach, although the prone position, if feasible with the patient's body habitus, may offer a wider space for percutaneous access. Combination therapy with either SWL or RIRS after PCNL improves stone-free rates.

Percutaneous management of caliceal diverticuli

BACKGROUND AND PURPOSE

Caliceal diverticula are rare congenital abnormalities that can become symptomatic if associated with a calculus or infection. We review percutaneous management of caliceal diverticula.

METHODS

Pathogenesis, clinical evaluation, management options, and recommended follow-up for symptomatic caliceal diverticula are reviewed. We present our single-stage and prepercutaneous nephrolithotomy opacification techniques for the management of caliceal diverticula. This involves complete extraction of all stone particles and ablation of the diverticular cavity without infundibular identification or dilation. Comparison of outcomes between our current ablative technique and our previous dilation technique is evaluated.

RESULTS

Percutaneous management of caliceal diverticula offers the highest symptomatic relief and stone-free rate of available management options. We identified 106 patients with caliceal diverticula who were treated with a percutaneous approach. Review of 85 of these patients demonstrated that most procedures can be performed with a small nephrostomy tube in place for 24 hours and an overnight hospital stay. Minimal complication and stone recurrence rates were observed. Patients treated with caliceal diverticular ablation experienced a shorter hospital stay, fewer complications, and a higher stone-free status than those patients who were treated with dilation of the diverticular infundibulum.

CONCLUSIONS

Percutaneous management of caliceal diverticula using cavity ablation is a minimally invasive technique that offers long-term symptomatic relief with minimal complications.

Percutaneous renal intervention: comparison of 2-D and time-resolved 3-D (4-D) ultrasound for minimal calyceal dilation using an ultrasound phantom and fluoroscopic control

The rapid advances made by ultrasound in recent years have increasingly taken 3-D ultrasound (3DUS) and 4-D ultrasound (4DUS) from the research setting to the patient's bedside. There are still unexplored areas like renal percutaneous intervention, where 4DUS has yet to be proven an effective tool. Ultrasound-only guidance in renal percutaneous access is used in selected well-dilated pelvi-calyceal systems (PCS), and fluoroscopy is often utilized as an adjunct. Our aim was to compare 2-D and 4-D guidance for punctures, with fluoroscopy as control, using an in vitro ultrasound phantom. Agar and latex were the tissue-mimicking materials used for the construction of the phantom. The latex targets were designed to simulate multidirection-facing minimally dilated renal calyces. Two interventional fellows punctured the "calyces" using first 2DUS and then 4DUS guidance, making use of a different set of targets each time. The time to puncture, time to introduction of wire, quality of puncture (judged on fluoroscopy) and global rating of both modalities were documented. There was no significant difference between the times to puncture using 2DUS (1.8 min) and 4DUS (2 min). Nor was there a significant difference in the quality of puncture. 4DUS had a higher median difficulty rating. The multiplanar reformatted (MPR) longitudinal and transverse images were found to be the most useful for needle guidance. Cross hairs in all MPR images were not just useful in aligning the images on target but also as surrogate targets. The phantom was found to be robust, with only one instance of air introduction after 30 punctures. We have found that 4DUS is at least as good as 2DUS in terms of quality of punctures in vitro. The technology still has some way to go as frame rates, transducer size and resolution improve.

Percutaneous nephrolithotomy made easier: a practical guide, tips and tricks

Percutaneous nephrolithotomy (PCNL) plays an integral role in managing large renal stones. Establishing percutaneous renal access is the most crucial step in the procedure and requires a thorough understanding of renal, retroperitoneal and thoracic anatomy to minimize the risk of complications. Moreover, access to fluoroscopy and the proper equipment are critical to ensuring complete stone removal. In this review we describe the technique of PCNL used in a high-volume endourology centre, where the urologist is involved in all aspects of the procedure.

Simple trigonometry on computed tomography helps in planning renal access

OBJECTIVES

To retrospectively assess the usefulness of the measurements on preoperative computed tomography (CT) of patients with urinary stone disease for planning the access site using vertical angulation of the C-arm.

METHODS

Of the patients who underwent percutaneous nephrolithotomy from November 2001 to October 2006, 41 patients with superior calix access had undergone preoperative CT. The depth of the target stone (y) and the vertical distance from that point to the first rib free slice (x) were measured on CT. The limit of the ratio of x over y was accepted as 0.58, with ratios below that indicating that infracostal access could be achieved by vertical angulation of the C-arm.

RESULTS

We achieved an approach to the superior calix through an infracostal access in 28 patients. The preoperative trigonometric study on CT predicted 24 of them. The stone-free rate was 92.6%, and no chest-related complications developed.

CONCLUSIONS

Simple trigonometry on CT of the patients with complex stones could help endourologists in planning renal access.

Pre-percutaneous nephrolithotomy opacification for caliceal diverticular calculi

Caliceal diverticula harbor calculi in as many as 50% of cases. Such stones rarely pass spontaneously. Various stone-removal techniques have been used, with percutaneous techniques generally having the best results. In patients with nonradiopaque stones or in whom the diverticulum does not opacify when contrast is instilled retrograde or by intravenous urogram, contrast can be instilled directly into the cavity with CT or ultrasound guidance. Three such cases are described, with good results.