The stone cone: a new generation of basketry.

PURPOSE: We designed a device to minimize ureteral stone migration during intracorporeal lithotripsy, decrease the likelihood of stone and/or basket entrapment, and extract whole stones and fragments. MATERIALS AND METHODS: Nitinol and stainless steel wires were configured into expandable tapered cones, which were placed cephalad to in vitro and in vivo concretions, and used to trap and extract stones as well as other test material. Safety features were evaluated by measuring the release of ball bearings and the tension needed to unwind the coils of the cone, which were greater than 4 mm. in diameter. We treated 4 patients with ureteral calculi using the Stone Conedagger to prevent migration and extract fragments. RESULTS: The cone-shaped devices expanded to occlude the test devices and human ureters, and prevented stone migration. They extracted whole concretions and fragments greater than 1.5 mm. The cone-shaped basket released a 5.5 mm. ball bearing at an average 0.127 pounds of tension when pulled through a 5 mm. plastic orifice. Coils greater than 4 mm. in diameter were straightened at a tension of 0.10 to 0.14 pounds. Stone migration during intracorporeal lithotripsy was prevented in the 4 patients with ureteral calculi, in whom large and small fragments were safely extracted. CONCLUSIONS: The Stone Cone may be placed via a ureteral catheter and opened cephalad to a ureteral stone to prevent stone migration during intracorporeal lithotripsy. It may extract whole stones and fragments greater than 1.5 mm. It is designed, so that its coils greater than 4 mm. in diameter release concretions too wide for the ureter or ureteral orifice after approximately 0.127 pounds of tension are applied. Because of these features, the Stone Cone represents a new generation of basketry appropriate to the era of ureteroscopy and intracorporeal lithotripsy. It is worthy of further clinical study.

CT and stone fragility.

Informed selection of treatment requires knowledge of the size and composition of a calculus. Spiral CT has a growing role in the detection of calculi, with an overall accuracy in excess of 95%. Moreover, the margin of error in determining stone size does not exceed 3.6%, and stone volume is underestimated by <5%. Pixelograms, the compilation of multiple points of attenuation, may provide clues to stone composition and durility.

Ureteroscopy for proximal ureteral calculi: prevention of stone migration.

BACKGROUND: The cephalad migration of proximal ureteral calculi accounts for a high percentage of ureteroscopic failures. PATIENTS AND METHODS: A balloon on a wire is a single-channel 0.038-inch hollow guidewire with a low-profile balloon, which is inflatable to 12F. Forty-two consecutive patients with proximal ureteral calculi underwent ureteroscopy with the aid of this device. RESULTS: Twenty-nine patients had successful placement of the balloon on a wire above the stone. Of those 29 patients, 26 became stone free with a single procedure. CONCLUSION: The balloon on a wire is a useful tool to aid in the prevention of proximal ureteral stone migration during ureteroscopy and to minimize the number of secondary procedures. In addition, it appears to be cost-effective.

Helical CT and ureteral colic.

The advantages of nonenhanced helical CT for the diagnosis of ureteral calculi include rapid scan time and patient throughput, safety (no contrast, less radiation), cost-effectiveness, high accuracy, minimal invasiveness, and ability to suggest of alternative diagnoses for flank pain--urologic and otherwise. Size measurement and location in the ureter, the two most important determinants of therapy, are precise with CT. It is particularly good for imaging small or radiolucent calculi, and calculi located at the ureterovesical. Secondary signs of obstruction and the soft-tissue rim sign are additional aids to the routine diagnosis of ureteral calculi. CT numbers indicate the fragility and therefore the likelihood of successful treatment of a calculus. Postprocessing options may help guide management decisions and may help plan interventions. The authors' experience after 30 months of using helical CT exclusively in the work-up of ureteral colic has been extremely favorable. Without hesitation, the authors believe that nonenhanced helical CT is the study of choice for the work-up of ureteral calculi.

Retrograde renoscopic fragmentation of moderate-size (1.5-3.0-cm) renal cystine stones.

PURPOSE: We present a series of cystinuric patients with renal cystine calculi between 1.5 and 3.0 cm treated with retrograde renoscopy and intracorporeal lithotripsy and report our results, complications, and inpatient utilization with this approach. PATIENTS AND METHODS: The hospital and office charts of five consecutive patients with six treated renal units who underwent retrograde renoscopy and electrohydraulic lithotripsy for renal cystine stones between 1.5 and 3.0 cm were reviewed. Data on stone size and location, procedures performed, results, complications, and inpatient hospital days were compiled. RESULTS: Five of the six renal units were either rendered stone free or had fragments totalling 3 mm or less. Three renal units required only a single procedure, one required repeat ureteroscopy for Steinstrasse, and one required SWL and repeat ureteroscopy for Steinstrasse. One renal unit was left with a 6-mm fragment for which the patient refused further treatment. There were no major complications. The mean hospital stay was 1 day, and the mean number of procedures per patient was 1.3. CONCLUSION: Retrograde renoscopy and intracorporeal lithotripsy for renal cystine stones 1.5 to 3.0 cm is safe and effective and should be considered as an alternative to percutaneous nephrolithotomy in these patients.

The effect of calprotectin on the nucleation and growth of struvite crystals as assayed by light microscopy in real-time.

PURPOSE: To use light microscopy to observe the urease-induced growth of struvite crystals in real-time, and to compare the effects of various proteins on that growth. MATERIALS AND METHODS: Artificial urine, with and without citrate, and a minimal urine solution containing only urea and the components of struvite and apatite were incubated with urease and test proteins in the depressions of culture slides. The number and size of rectangular and X-shaped struvite crystals were recorded using a low-power phase contrast microscope. RESULTS: The formation of crystalline struvite appears to occur after the formation of an amorphous calcium- and magnesium-containing phase. The extent of this amorphous phase is dependent on the presence of calcium and citrate, both of which strongly promote its formation over the crystalline phase. alpha-globulin, gamma-globulin and chymotrypsin inhibitor all result in the same amount of crystalline struvite as bovine serum albumin which is used as a control. Calprotectin, on the other hand, causes consistent and significant reductions in the number and size of struvite crystals under a wide range of conditions. No changes in the morphology of the struvite crystals were observed. CONCLUSIONS: Calprotectin, the dominant protein of infection stone matrix, has distinctive properties which affect the formation and growth of struvite crystals. The presence of citrate in synthetic urine dramatically reduces the number of struvite crystals observed. The present method for observing the effects of putative infection stone inhibitors appears to have merit.

The physiologic approach to the medical management of stone disease.

The cause of urinary stone disease can now be detected in approximately 80% of patients. Effective treatment can substantially reduce the recurrence of urinary calculi. Proper therapy depends on a thorough understanding of the physiology of calcium, oxalate, uric acid, cystine, and struvite formation and the medication developed for prevention. This article reviews the physiologic basis of urinary stone management in a straightforward, understandable fashion.

Ureteral Stones Clinical Guidelines Panel summary report on the management of ureteral calculi. The American Urological Association.

PURPOSE: The American Urological Association convened the Ureteral Stones Clinical Guidelines Panel to analyze the literature regarding available methods for treating ureteral calculi and to make practice policy recommendations based on the treatment outcomes data. MATERIALS AND METHODS: The panel searched the MEDLINE data base for all articles related to ureteral calculi published from 1966 to January 1996. Outcomes data were extracted from articles accepted after panel review. The data were then meta-analyzed to produce outcome estimates for alternative treatments of ureteral calculi. RESULTS: The data indicate that up to 98% of stones less than 0.5 cm. in diameter, especially in the distal ureter, will pass spontaneously. Shock wave lithotripsy is recommended as first line treatment for most patients with stones 1 cm. or less in the proximal ureter. Shock wave lithotripsy and ureteroscopy are acceptable treatment choices for stones 1 cm. or less in the distal ureter. CONCLUSIONS: Most ureteral stones will pass spontaneously. Those that do not can be removed by either shock wave lithotripsy or ureteroscopy. Traditional blind basket extraction, without fluoroscopic control and guide wires, is not recommended. Open surgery is appropriate as a salvage procedure or in certain unusual circumstances.

Ureterorenoscopic approach to the symptomatic caliceal diverticulum.

PURPOSE: We evaluated ureterorenoscopy as a treatment approach to symptomatic caliceal diverticula. MATERIALS AND METHODS: Since 1989, 20 women and 6 men suffering from pain, recurrent urinary tract infections or urosepsis were treated using flexible ureterorenoscopy, balloon dilation or incision of the diverticular neck and subsequent intrarenal stone fragmentation when needed. RESULTS: Of 19 upper and middle caliceal diverticula 16 (84%) and 2 of 7 lower caliceal diverticula were successfully identified. The orifice to the diverticular cavity was dilated and the stone was fragmented. Of the patients 13 were treated as outpatients and 10 required a 1-night hospital stay. Of those patients in whom the diverticulum could be entered and the stone fragmented 100% were symptom-free at a mean followup of 39 months. One patient required repeat treatment to remove residual stone. CONCLUSIONS: Ureterorenoscopy produces minimal morbidity and is an effective treatment of upper and middle caliceal diverticula.

Intracorporeal lithotripsy. Instrumentation and development.

This article describes the history of intracorporeal lithotripsy and the impact of previous techniques on modern devices. Technical and clinical specifics for several historical and current intracorporeal lithotripsy methods are described.

Calcium oxalate stone morphology: fine tuning our therapeutic distinctions.

PURPOSE: We determined specific radiographic morphological patterns of crystallographically analyzed pure and mixed calcium oxalate dihydrate and calcium oxalate monohydrate urinary calculi. MATERIALS AND METHODS: A total of 86 greater than 1 cm. calculi crystallographically analyzed as pure calcium oxalate monohydrate, calcium oxalate dihydrate or admixtures of the 2 types was studied to determine whether various forms of calcium oxalate differed in radiographic morphology. RESULTS: Four distinct radiographic patterns could be identified by plain film roentgenography: group 1--14 patients with smooth edged, homogeneously dense calculi, some with dentate shapes (12 had pure calcium oxalate monohydrate stones), group 2--33 with multinodular calculi with irregular edges and variegated areas of more and less radiodensity (32 had greater than 60% calcium oxalate monohydrate), group 3--33 with a uniform, stippled pattern, often with identifiable radial striations, and with a larger amount of calcium oxalate dihydrate than groups 1 or 2, and group 4--6 with poorly radiodense, loosely aggregated crystals with a lacy structure. CONCLUSIONS: At least 4 patterns of calcium oxalate stones are recognizable by plain film roentgenography. Because the fragility of calcium oxalate calculi is determined by the relative calcium oxalate monohydrate and dihydrate content, pretreatment recognition of these radiographic patterns may affect the selection of a therapeutic modality.

Nephrolithiasis Clinical Guidelines Panel summary report on the management of staghorn calculi. The American Urological Association Nephrolithiasis Clinical Guidelines Panel.

The American Urological Association Nephrolithiasis Clinical Guidelines Panel recommendations for managing struvite staghorn calculi are based on a comprehensive review of the treatment literature and meta-analysis of outcome data from the 110 pertinent articles containing viable, unduplicated data. The panel concluded that the 3 most significant outcome probabilities are those of being stone-free, undergoing secondary unplanned procedures and having associated complications. Panel guideline recommendations for most standard patients are that neither shock wave lithotripsy monotherapy nor open surgery should be a first-line treatment choice but that a combination of percutaneous stone removal and shock wave lithotripsy should be used.

Identification of the calcium-binding protein calgranulin in the matrix of struvite stones.

The identification of calcium-binding proteins in urine and kidney stones has led to a closer look at the role of matrix proteins in urolithiasis. We analyzed five struvite stones for protein content and identified two bands (8 and 14 KDa) that were confirmed by gel electrophoresis and amino acid sequencing to be calgranulin. This protein, which is known by several other names, has bacteriostatic antifungal activity. Its role in the formation of struvite stones warrants further investigation.

Ureteroscopic fragmentation followed by extracorporeal shock wave lithotripsy: a treatment alternative for selected large or staghorn calculi.

Ureterorenoscopic fragmentation followed by extracorporeal shock wave lithotripsy (ESWL) is proposed as an addition to the alternatives of percutaneous nephrostolithotomy alone or with ESWL, or ESWL monotherapy for treatment of large (greater than 500 mm.2) or staghorn calculi. Six patients who failed percutaneous tube placement and 2 additional patients, all of whom had fragile-appearing, large volume (greater than 500 mm.2) renal calculi, were treated by primary ureteroscopy with semirigid or flexible instruments, fragmentation of the stone with the pulsed dye laser, ureteral stenting and subsequent ESWL. There were 2 instances of acute pyelonephritis and 2 of steinstrasse. A total of 2.76 procedures was performed per patient and the average anesthesia time was 160 minutes (excluding ESWL). Median hospitalization was 3.5 days (average 7.5). Of the 8 patients 7 became stone-free. One patient has sterile urine and a residual fragment smaller than 5 mm. All patients have been followed for 1 year and there have been no recurrences. The properly selected patient for ureterorenoscopic fragmentation followed by ESWL is one with a fragile calculus of moderate volume without strictured infundibula or significantly dilated calices.

Special article: calculus breakability--fragility and durility.

Prior to the use of lithotripsy techniques, there was no requirement for a vocabulary to describe the relative breakability of a urinary calculus. With the introduction of lithotripsy, we became aware that calculi of different radiologic appearances or chemical compositions varied in their susceptibility to fragmentation. Because all truly new distinctions require new expressions to characterize them, we had to create a term to express this new distinction, and the term we chose was "stone fragility." Currently, if we see a 1-cm calcium oxalate dihydrate stone, we say it appears fragile ("easily broken," from the Latin frangere, "to break", but if we see a dense brushite or a cystine stone, we can describe it only in terms of fragile; i.e., "not fragile" or, incorrectly, "hard": an antonym for "fragile" does not exist. In the interest of common understanding and more accurate quantitation of stone breakability, a neologism is suggested that has an appropriate Latin root, is easily spoken, sounds authentic, and is useful. It is proposed that, in the interest of accuracy and as a reflection of our greater sophistication regarding stone breakability, we use the Latin root dur (hard, difficult) and a suffix ile (of, like, pertaining to) to create the terms "durile" (adj; pertaining to or capable of being difficult to break) and "durility" (noun; a quality of being difficult to break or fragment).

Stone granuloma: a cause of ureteral stricture.

Ureteral stricture is a recognized complication of ureteroscopy and ureteral stone fragmentation. Although most strictures are either asymptomatic or easily dilated, there are some strictures that result in progressive ureteral obstruction, do not respond to ureteral dilation and require operative intervention. A review of 125 percutaneous nephrostolithotomies for staghorn stone disease and 652 ureteroscopic stone fragmentations revealed 5 cases in which refractory ureteral strictures developed, requiring operative intervention. In 4 patients a "stone granuloma," embedded particles of calcium oxalate associated with macrophages and foreign body giant cells, was found with surrounding fibrosis and ureteral obstruction. In the remaining patient a suture granuloma from a recent ureterolithotomy was the source of the stricture. In each instance of stone granuloma the particles of calcium oxalate had become embedded in the wall as a consequence of ureteroscopic stone fragmentation and partial ureteral wall disruption. During ureteroscopy and intracorporeal lithotripsy every effort should be made to prevent calcium oxalate particles from becoming embedded in the ureteral wall. They are not inert and may cause irreversible stricture formation. To our knowledge, stone granuloma is a previously undescribed phenomenon and should be suspected when ureteral strictures that occur following ureteroscopy do not respond to endourological methods of management.

The electromechanical impactor: the results of design modifications.

The first generation clinical electromechanical impactor was a 5F device that used a 3.0F electrohydraulic probe within a coiled spring with a blunt solder end cap. Clinical trials showed that this device fragmented 70% of the calculi but failed to fragment the harder stones. Applying the principle that impact kinetic energy is most dependent on velocity (KE = 1/2 MV2), 3 major design modifications were made to improve fragmentation efficiency: 1) the spring was changed from an extension to a compression type that captured and used more of each electrical spark, 2) the tip was changed from solder to lightweight titanium and 3) the tip shape was changed from blunt to conical. The result was a 41% increase in impact kinetic energy, a 40% increase in probe longevity and successful in vitro fragmentation of the harder calculi without compromise in tissue safety as determined by membrane perforation studies.