In vivo determination of urinary stone composition using dual energy computerized tomography with advanced post-acquisition processing.

PURPOSE: We assessed whether dual energy computerized tomography with advanced post-image processing can accurately differentiate urinary calculi composition in vivo. MATERIALS AND METHODS: A total of 25 patients scheduled to undergo ureteroscopic/percutaneous nephrolithotomy were prospectively identified. Dual energy computerized tomography was performed using 64-slice multidetector computerized tomography. Novel post-processing (DECTSlope) used pixel by pixel analyses to generate data sets grayscale encoding ratios of relative differences in attenuation of low (DECT80 kVp) and high energy (DECT140 kVp) series. Surgical extraction and Fourier spectroscopy resulted in 82 calculi. Of these stones 51 showed minor admixtures (uric acid, ammonium urate, struvite, calcium oxalate monohydrate and brushite) and 31 were polycrystalline (mixtures of calcium oxalate monohydrate/dihydrate and calcium phosphate). Analyses identified stone clusters of equal composition and distinct attenuation descriptors on DECT140 kVp, DECT80 kVp and DECTSlope. Iterative cross-validation of the 3 dual energy computerized tomography data sets was used to identify characteristic attenuation limits for each stone type. RESULTS: Attenuatio profiles showed substantial overlap among various stones on DECT140 kVp (uric acid 427.3±168.1 HU, ammonium urate 429.9±99.7 HU, struvite 480.2±123.5 HU, calcium oxalate monohydrate 852.4±301.4 HU, brushite 863.7±180.1 HU and polycrystalline 858.1±210.5 HU) and on DECT80 kVp (uric acid 493.6±182.8 HU, ammonium urate 591.5±157.9 HU, struvite 712.4±173.9 HU, calcium oxalate monohydrate 1,240.5±494.7 HU, brushite 1,532.1±273.1 HU and polycrystalline 1,358.7±316.8 HU). Statistically spectral separation was not sufficient to characterize stones unambiguously based on DECT140 kVp/DECT80 kVp attenuation. Analysis of attenuation showed sufficient spectral separation on DECTSlope (uric acid 14.9±10.9 U, ammonium urate 56.1±1.8 U, struvite 42.7±1.4 U, calcium oxalate monohydrate 62.8±1.8 U and brushite 113.2±5.3 U). Polycrystalline stones (51.8±3.7 U) overlapped with struvite and ammonium urate stones. This overlap was resolved as all struvite/ammonium urate stones measured 900 HU or less and all polycrystalline stones measured more than 900 HU on DECT80 kVp. CONCLUSIONS: Dual energy computerized tomography with novel post-processing allows accurate discrimination among main subtypes of urinary calculi in vivo and, thus, may have implications in determining the optimum clinical treatment of urinary calculi from a noninvasive, preoperative radiological assessment.

Tubeless percutaneous nephrolithotomy--the new standard of care?

PURPOSE: Traditionally the placement of a nephrostomy tube at the conclusion of percutaneous nephrolithotomy is considered the standard of care. However, the need for nephrostomy tube placement has been questioned by numerous authors. We evaluated the literature regarding tubeless percutaneous nephrolithotomy, and determined potential candidates for tubeless percutaneous nephrolithotomy and whether this procedure can be considered the new standard of care for complex stone removal. MATERIALS AND METHODS: A MEDLINE search was conducted between May 1997 and January 2010 to detect studies reporting tubeless percutaneous nephrolithotomy. "Nephrolithiasis," "percutaneous nephrolithotomy," "tubeless" and "lithotripsy" were used as medical subject headings (MeSH) key words. Additional citations were identified by reviewing the reference lists of the included articles. All relevant articles were reviewed for indications, outcomes and complications. RESULTS: The data obtained from 50 reports document comparable complication rates between tubeless and standard percutaneous nephrolithotomy. Tubeless percutaneous nephrolithotomy demonstrated advantages such as less pain, less debilitation, less costs and a shorter hospital stay. Mean stone-free rates for tubeless percutaneous nephrolithotomy were as high as 89%. CONCLUSIONS: Tubeless percutaneous nephrolithotomy appears to be safe and efficacious in uneventful procedures, in children, in obese patients, in simultaneous bilateral procedures, in supracostal access and in renal units with coexisting anatomical anomalies. Nephrostomy tube placement should still be considered in certain cases such as those with more than 2 nephrostomy access tracts, those necessitating a second look and those with intraoperative complications such as significant bleeding or collecting system perforation.

Minimizing radiation exposure during percutaneous nephrolithotomy.

Given the recent trends in growing per capita radiation dose from medical sources, there have been increasing concerns over patient radiation exposure. Patients with kidney stones undergoing percutaneous nephrolithotomy (PNL) are at particular risk for high radiation exposure. There exist several risk factors for increased radiation exposure during PNL which include high Body Mass Index, multiple access tracts, and increased stone burden. We herein review recent trends in radiation exposure, radiation exposure during PNL to both patients and urologists, and various approaches to reduce radiation exposure. We discuss incorporating the principles of As Low As reasonably Achievable (ALARA) into clinical practice and review imaging techniques such as ultrasound and air contrast to guide PNL access. Alternative surgical techniques and approaches to reducing radiation exposure, including retrograde intra-renal surgery, retrograde nephrostomy, endoscopic-guided PNL, and minimally invasive PNL, are also highlighted. It is important for urologists to be aware of these concepts and techniques when treating stone patients with PNL. The discussions outlined will assist urologists in providing patient counseling and high quality of care.

Use of ketoconazole to probe the pathogenetic importance of 1,25-dihydroxyvitamin D in absorptive hypercalciuria.

Ketoconazole was used to probe the pathogenetic importance of the serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] concentration in 19 patients with well characterized absorptive hypercalciuria (AH). Patients were studied while receiving a constant metabolic diet before and after 2 weeks of ketoconazole administration (600 mg daily). Twelve of the patients were classified as ketoconazole responders, because in conjunction with a reduction of serum 1,25-(OH)2D from 113 +/- 36 to 70 +/- 26 pmol/L, intestinal 47Ca absorption decreased from 76.3 +/- 8.1% to 61.9 +/- 7.7%, and 24-h urinary Ca excretion declined from 7.6 +/- 1.4 to 5.7 +/- 1.1 mmol (P < 0.001 each). In these patients, intestinal 47Ca absorption was directly correlated with serum 1,25-(OH)2D levels and 24-h Ca excretion. In another group of 7 patients, termed ketoconazole nonresponders, despite reduction of 1,25-(OH)2D from 122 +/- 36 to 84 +/- 17 pmol/L (P = 0.015), there was no significant change in intestinal Ca absorption (76.0 +/- 8.2% to 72.1 +/- 10.6%) or 24-h urinary Ca excretion (7.3 +/- 1.3 to 7.2 +/- 1.0 mmol). In these patients, neither intestinal Ca absorption nor urinary Ca excretion was correlated with serum 1,25-(OH)2D levels. It, thus, appears that AH is a heterogeneous disorder comprised of both vitamin D-dependent and vitamin D-independent subsets. Although useful to probe the pathogenesis of AH, chronic treatment with ketoconazole is not recommended because of its generalized effects in inhibiting steroid synthesis.

Renal calculi: pathogenesis, diagnosis, and medical therapy.

Selective medical therapy of nephrolithiasis is highly effective in preventing new stone formation. A remission rate of greater than 80% and an overall reduction in individual stone formation rate of greater than 90% can be obtained in patients with nephrolithiasis. In patients with mild to moderate severity of stone disease, virtually total control of stone disease can be achieved with a remission rate of greater than 95%. The need for stone removal may be dramatically reduced by an effective prophylactic program (Fig 6). Selective pharmacological therapy of nephrolithiasis also encompasses the advantages of overcoming nonrenal complications as well as averting certain side effects that may be caused by nonselective medical therapy. Despite these advantages, it is clear that selective medical therapy cannot provide total control of stone disease. A satisfactory response requires continued, dedicated compliance by patients to the recommended program and a commitment by the physician to provide long-term follow-up and care.

Struvite calculi.

Although calcium oxalate stones are the most common type of calculi found in the United States, struvite or infection stones are quite common and generally pose a difficult treatment dilemma. The presence of urinary infection with a urease-producing organism is necessary for these stones to form. Proteus species account for the majority of infections that cause struvite stones in all age ranges. However, other organisms also produce urease and may be detected in conjunction with struvite calculi. Factors that may predispose one to urinary tract infections increase the likelihood of struvite stone formation. Several options are available for the treatment of existing struvite calculi. Smaller stones may be treated with primary shock-wave lithotripsy, whereas larger stones are more appropriately managed with percutaneous or combination procedures. Medical therapy to prevent recurrent stone formation is also an essential part of the treatment of these patients, as the risk of stone recurrence is extremely high. Antibiotic therapy and urease inhibitors perhaps offer the best form of preventative treatment available today.

Hypercalciuria and altered intestinal calcium absorption occurring independently of vitamin D in incomplete distal renal tubular acidosis.

Negative calcium balance and calcium nephrolithiasis are two sequelae of chronic metabolic acidosis. To establish the effects of acidosis on calcium and vitamin D metabolism, we have examined a group of nine patients with incomplete distal renal tubular acidosis. Patients were studied during a control phase and after eight months of potassium citrate treatment, 60 to 80 meq daily. Potassium citrate caused a significant decrease in urinary calcium. The fractional intestinal calcium absorption increased significantly, yet no change was observed in serum vitamin D levels. The estimated calcium balance increased significantly from -70.2 +/- 63.8 to +66.7 +/- 48.7 mg/d (P less than 0.01). Thus, potassium citrate treatment improved the estimated calcium balance by lowering urinary calcium while increasing the fractional intestinal calcium absorption. The original hypercalciuric state, its correction to normocalciuria, and the augmentation of intestinal calcium absorption seen in these patients are probably independent of vitamin D control since there was no change noted in serum 1,25-dihydroxyvitamin D levels.

Male urethral diverticulum: the double density sign.

An anatomic defect of the urethra is occasionally the cause of voiding dysfunction in the young male patient. A urethral diverticulum can often be overlooked if retrograde urethrography is not performed properly. Two cases are presented along with a discussion of the technique for dynamic retrograde urethrography. The description of a new radiologic sign indicative of a posterior bulbar urethral diverticulum, is presented.

Long-term follow-up of Acucise incision of ureteropelvic junction obstruction and ureteral strictures.

OBJECTIVES: There are few data on the long-term effectiveness of various endoureterotomy procedures. One such technique for the treatment of ureteral strictures and ureteropelvic junction (UPJ) obstruction utilizes a recently developed ureteral cutting balloon catheter, Acucise. This device may be used under fluoroscopic guidance alone, which significantly reduces operating time. The purpose of this study is to determine the long-term efficacy of the Acucise balloon in treatment of ureteral strictures and UPJ obstruction. METHODS: Fifteen patients have been treated with the Acucise balloon, with an average follow-up of 21.6 months. Five of the patients have been followed for more than 2 years, and 11 of the patients had greater than 1 year follow-up. RESULTS: The overall success rate, defined as resolution of obstruction radiographically or disappearance of symptoms, or both, was 73%, with only 4 overt failures. All but one of the procedures were completed in 45 minutes or less, and 13 of the 15 patients were treated as outpatients. There were two significant complications. Seventy-five percent (3 of 4) of the treatment failures occurred within the first 4 months following original procedure. Of the 4 total failures. 2 patients had ureteral strictures greater than 2 cm in length, which were likely ischemic in nature secondary to previous surgeries. One patient, with a primary UPJ obstruction, was found to have a crossing vessel at subsequent open pyeloplasty. CONCLUSIONS: The Acucise cutting balloon offers the urologist a rapid and effective alternative for the management of ureteral strictures and UPJ obstruction. In our experience, early results (3 to 4 months) are usually indicative of long-term success. Proper patient selection may further improve long-term results of this simple, innovative technique.

Ethnic and geographic diversity of stone disease.

OBJECTIVES: To ascertain diversity or similarity in stone prevention and problems among different countries around the world. METHODS: Urolithiasis research groups from 10 countries completed a questionnaire. RESULTS: Cost of extracorporeal shock wave lithotripsy (ESWL) was considerably greater than that of drugs in four countries, and equivalent in remaining countries. Stone composition was similar among different countries. Certain urinary risk factors were associated with particular countries, probably from dietary indiscretions. ESWL was used in the majority of patients and open surgery in a minority of patients, except in one country. Medical diagnostic evaluation was used in the majority of patients except in one country. Drug treatment was nonselective, and provided to a minority of recurrent stone-formers. CONCLUSIONS: There is considerable similarity in stone presentations and problems throughout the world. The diversity is likely to be due to nutritional-environmental and socio-political-economic factors.

Use of a digital camera in the urologic setting.

Urologists are faced with increasing demands for clear documentation of their work. We report the use of a digital camera in our practice to capture images throughout the urologic setting. The digital camera was a quick and convenient means of obtaining good quality reproductions of radiographic and pathologic findings. Use of the camera greatly enhanced the efficiency of our practice by allowing incorporation of images into patient records and an image library.

Use of ureteroscopy and holmium:YAG laser in patients with bleeding diatheses.

OBJECTIVES: To assess the safety and efficacy of ureteroscopy and holmium laser in patients with known bleeding diatheses and upper tract calculi or transitional cell carcinoma (TCC). METHODS: Eight patients with stone disease and 1 patient with upper tract TCC were treated ureteroscopically with the holmium laser. The mean age was 58.3 years (range 42 to 74). Six patients were receiving Coumadin, with a mean international normalized ratio (INR) of 2.1 (normal INR less than 1.1). Two patients were thrombocytopenic, and 1 had von Willebrand's disease. None of the bleeding diatheses were corrected before surgery. Semirigid or flexible ureteroscopes were used to access the ureter or intrarenal collecting system. The holmium laser was used to fragment calculi or ablate tumor. RESULTS: Only 1 patient had a postoperative bleeding complication related to the procedure, involving an episode of oliguria secondary to a small ureteral clot. This cleared without surgical intervention. Another patient developed an episode of epistaxis after administration of ketorolac for pain. Six of 7 patients who underwent laser fragmentation for calculi were stone free on follow-up intravenous urogram at 1 month, and no tumor recurrence was noted in the patient with TCC (follow-up of 4 months). CONCLUSIONS: Ureteroscopy allowed excellent access to all regions of the upper tracts, and holmium laser fragmentation of calculi or ablation of tumor was effective in managing each particular problem. Use of the holmium laser with ureteroscopic access provides a safe and acceptable combination for treating upper tract pathology in patients with uncorrected bleeding diatheses. As a result, these patients can avoid added costs of extended hospital stay and risks associated with transfusions.

Comparison of open and endourologic approaches to the obstructed ureteropelvic junction.

OBJECTIVES: To compare open pyeloplasty with three minimally invasive modalities: antegrade endopyelotomy, Acucise endopyelotomy (Applied Medical, Laguna Hills, Calif), and laparoscopic pyeloplasty. METHODS: Forty-five adult patients with ureteropelvic junction obstruction were managed by one of the above four techniques. Success rates, analgesic use, length of hospital stay, recovery time, and complications were compared between each of the four groups. RESULTS: Successful relief of obstruction was achieved in 100% of patients undergoing open and laparoscopic dismembered pyeloplasty, 78% undergoing Acucise endopyelotomy, and 77% undergoing antegrade percutaneous endopyelotomy. Acucise endopyelotomy results in shorter convalescence (1 week) than antegrade endopyelotomy (4.7 weeks), laparoscopic pyeloplasty (2.3 weeks) or open pyeloplasty (10.3 weeks). Complication rates appear to be similar among all groups. CONCLUSIONS: Our limited data imply that Acucise endopyelotomy offers low morbidity with success rates comparable to antegrade pyeloplasty, whereas laparoscopic pyeloplasty is as effective as open pyeloplasty with diminished morbidity.

Safety and efficacy of the Alexandrite laser for the treatment of renal and ureteral calculi.

OBJECTIVES: To assess the safety and efficacy of the Alexandrite laser for intracorporeal lithotripsy of renal and ureteral stones in conjunction with ureterorenoscopy or percutaneous nephrostolithotomy. METHODS: We retrospectively analyzed the records of 137 patients with 169 calculi in 143 renoureteral units who were treated with the Alexandrite laser via a retrograde (91.5%) or antegrade (8.5%) endoscopic approach. RESULTS: Adequate intraoperative fragmentation of the stone was observed in 88.8% of the cases. No intraoperative complications were attributable to the laser. At a mean follow-up of 34 days, the overall stone-free rate was 74.4%. The stone-free rate for ureteral stones (n = 115) was 80%, whereas the stone-free rate for renal stones (n = 22) was only 44%. In the best subgroup of ureteral stones (10 mm or less in the distal ureter), the stone-free rate was 97.4%. CONCLUSIONS: The Alexandrite laser is a safe modality for intracorporeal lithotripsy and is highly effective for ureteral stones less than 10 mm in size.

Retroperitoneal and pelvic extraperitoneal laparoscopy: an international perspective.

OBJECTIVES: To assess technical preferences and current practice trends of retroperitoneal and pelvic extraperitoneal laparoscopy. METHODS: A questionnaire survey of 36 selected urologic laparoscopic centers worldwide was performed. RESULTS: Twenty-four centers (67%) responded. Overall, 3988 laparoscopic procedures were reported: transperitoneal approach (n = 2945) and retroperitoneal/extraperitoneal approach (n = 1043). Retroperitoneoscopic/extraperitoneoscopic procedures included adrenalectomy (n = 74), nephrectomy (n = 299), ureteral procedures (n = 166), pelvic lymph node dissection (n = 197), bladder neck suspension (n = 210), varix ligation (n = 91), and lumbar sympathectomy (n = 6). Mean number of total laparoscopic procedures performed in 1995 per center was 41 (range 5 to 86). Major complications occurred in 49 (4.7%) patients and included visceral complications in 26 (2.5%) patients and vascular complications in 23 (2.2%). Open conversion was performed in 69 (6.6%) patients, electively in 41 and emergently in 28 (visceral injuries, n = 16; vascular injuries, n = 1 2). Retroperitoneoscopy/extraperitoneoscopy is gaining in acceptance worldwide: in 1993, the mean estimated ratio of transperitoneal laparoscopic cases versus retroperitoneoscopic/ extraperitoneoscopic cases per center was 74:26; however, in 1996 the ratio was 49:51. CONCLUSIONS: Retroperitoneoscopy and pelvic extraperitoneoscopy are important adjuncts to the laparoscopic armamentarium in urologic surgery. The overall major complication rate associated with retroperitoneoscopy/extraperitoneoscopy was 4.7%.

Pharmacologic treatment of calcium calculi.

Selective pharmacologic therapy of calcium nephrolithiasis is highly effective in preventing new stone formation. A remission rate of greater than 80 per cent and overall reduction in individual stone formation rate of greater than 90 per cent can be obtained in patients with calcium nephrolithiasis. In patients with mild-to-moderate severity of stone disease, virtually total control of stone disease can be achieved as evidenced by remission rates of greater than 95 per cent. The need for stone removal may be dramatically reduced by an effective prophylactic program. Selective pharmacologic therapy of calcium nephrolithiasis also encompasses the advantages of overcoming the nonrenal manifestations of conditions that cause stone formation as well as averting certain side effects that may be caused by nonselective medical therapy. Despite these advantages, selective medical therapy clearly cannot provide total control of stone disease. A satisfactory response requires continued, dedicated compliance by patients to the recommended program and a commitment of the physician to provide long-term follow-up and care.

Pharmacologic treatment of uric acid calculi.

Uric acid stone disease is dependent on three pathogenetic factors: acid urine pH, low urine volume, and hyperuricosuria. The management of nonobstructing uric acid calculi should include maintenance of an alkaline urine, an increase in urine volume, and reduction in urinary uric acid excretion. It appears that potassium alkali may avoid the complication of calcium stone formation in patients with uric acid stones. In patients with obstructing uric acid calculi, more rapid dissolution may be accomplished with intravenous alkalinization or direct irrigation of the stone with an alkaline solution.

Renal surgery in the new millennium.

In the not too distant future, the minimally invasive renal surgeon will be able to practice an operation on a difficult case on a three-dimensional virtual reality simulator, providing all attributes of the real procedure. The patient's imaging studies will be imported into the simulator to better mimic particular anatomy. When confident enough of his or her skills, the surgeon will start operating on the patient using the same virtual reality simulator/telepresence surgery console system, which will permit the live surgery to be conducted by robots hundreds of miles away. The robots will manipulate miniature endoscopes or control minimally or noninvasive ablative technologies. Endoscopic/laparoscopic footage of the surgical procedure will be stored digitally in optical disks to be used later in telementoring of a surgery resident. All this and more will be possible in the not so distant third millennium.

Flexible cystoscopy.

Flexible fiberoptic technology was first applied to cystoscopy in 1973, with greatly increased usage since 1982. Most procedures formerly performed with rigid cystoscopes can be done using flexible cystoscopes with minimal or no anesthesia. Patient positioning and precystocopy preparation and draping are simplified with the flexible fiberoptic instruments. Complete examination of the urethra and bladder can be performed with a single-lens system and with the patient in a variety of positions. Fiberoptic cystoscopy is limited in patients who are bleeding or have blood clots in their bladders. Withdrawal of irrigant or bladder drainage is cumbersome, and the fiberoptic image is currently not of the same caliber as that of the rigid-lens systems. Fiberoptic cystoscopy has become the procedure of choice for many urologists for ureteral stenting prior to extracorporeal shock-wave lithotripsy. With the advent of lithotripters that require no anesthesia, this application is likely to broaden. Future applications of flexible cystoscopy may include a flexible videocystoscope for use in diagnostic and therapeutic procedures.

Management of residual stones.

Stone-free status is highly dependent on selection of the appropriate surgical technique, which should be tailored according to the individual stone and patient parameters. Although a stone-free state is the desired outcome of surgical intervention of urolithiasis, the authors believe that the presence of noninfection, nonobstructive, asymptomatic postprocedural residual fragments can be managed metabolically in order to prevent stone growth adequately. Further surgical intervention in the case of residual fragments is warranted if the clinical indications that prompted the original surgery persist.