Calculus fragmentation in laser lithotripsy.

The intracorporeal treatment of urinary calculi with lasers is presented, which describes laser-calculus interactions associated with lithotripsy. Reliable fragmentation of calculi with diverse compositions and minimal collateral tissue damage are primarily contingent upon laser parameters (wavelength, pulse duration, and pulse energy) and physical properties of calculi (optical, mechanical, and chemical). The pulse duration governs the dominant mechanism in calculi fragmentation, which is either photothermal or photoacoustical/photomechanical. Lasers with long pulse durations (i.e. > tens of micros) induce a temperature rise in the laser-affected zone with minimal acoustic waves; material is removed by means of vaporization, melting, mechanical stress, and/or chemical decomposition. Short-pulsed laser ablation (i.e. < 10 micros), on the other hand, produces shock waves, and the resultant mechanical energy fragments calculi. Work continues throughout the world to evaluate the feasibility of advanced lasers in lithotripsy and to optimize laser parameters and light delivery systems pertinent to efficient fragmentation of calculi.

How do patients with interstitial cystitis present?

PURPOSE: We determined how interstitial cystitis progresses from initial symptoms to diagnosis. MATERIALS AND METHODS: We retrospectively analyzed the records of 45 patients to determine the dates of symptom onset and diagnosis, and sequence of urgency/frequency, nocturia and pain. We also documented alternate and previous diagnoses, and previous surgical treatments. RESULTS: Of the patients 89% presented with only 1 symptom. Median time from the initial symptom to all symptoms was 2 years (mean 5.5). The most common previous diagnoses were urinary infection in 19 cases, a gynecologic diagnosis in 14 and urethral diagnoses in 6. A previous urinary infection was documented in only 1 of 19 patients, while 11 had undergone hysterectomy and 5 diagnosed with endometriosis had no pathological documentation available. CONCLUSIONS: Early interstitial cystitis presents variably and usually with only a single symptom of urgency/frequency, nocturia or pain. Clinicians may fail to appreciate the symptoms of early interstitial cystitis, which leads to delayed diagnosis until the patient is more symptomatic. With time multiple symptoms manifest. Bacterial cystitis, prostatitis, endometriosis and chronic pelvic pain are common initial misdiagnoses. Interstitial cystitis should be considered when laboratory documentation of alternate diagnoses is lacking or when patients fail to respond to therapy for alternate diagnoses.

Holmium: YAG laser lithotripsy for gallstones. A preliminary report.

BACKGROUND: Most retained gallstones can be extracted at the time of operative exploration or endoscopic retrograde cholangiopancreatography (ERCP). Infrequently, impaction or associated anatomic abnormalities may prevent their clearance. We assessed the efficacy of the holmium:YAG laser in managing retained biliary calculi that had proven refractory to the usual methods of extraction. METHODS: Two patients with calculi impacted in the intrapancreatic common bile duct and one patient with residual stones in a nonfunctional gallbladder were treated with holmium:YAG laser lithotripsy. Two of these patients were treated under conscious sedation, and one received a general endotracheal anesthetic. Laser energy was delivered by a 272-mm optical fiber inserted through a 7-Fr fiberoptic endoscope. The ablative effects were monitored continuously via videoscopic. RESULTS: All of the stones were cleared successfully in a single therapeutic setting. In one patient, fragments of the impacted intraductal stone were extracted with an endoscopic wire basket. In the other two patients, stone debris was completely cleared with saline irrigation. No complications developed, and all patients remained free of recurrence during a 6-month follow-up period. CONCLUSIONS: The holmium:YAG laser is a multidisciplinary instrument that is safe and effective in the fragmentation of both urinary and biliary calculi. Because it can be delivered through a small-caliber fiberoptic endoscope, it should be particularly useful to laparoscopic surgeons who manage complicated biliary tract disease.

How do urology residents manage personal finances?

OBJECTIVES: To examine personal financial management among residents to answer three research questions: do residents make reasonable financial choices; why do some residents not save; and what steps can be taken to improve residents' personal financial decisions. METHODS: Portions of the Federal Reserve Board's Survey of Consumer Finances were modified and piloted to elicit demographic, expense, saving, and income data. The final questionnaire was completed by 151 urology residents at 20 programs. RESULTS: Comparing residents with the general population in the same age and income categories, the median debt/household income ratio was 2.38 versus 0.64. Residents had greater educational debt, greater noneducational debt, and lower savings. Resident participation in retirement accounts was 100% at institutions with employer-matching 401k or 403b plans, 63% at institutions with nonmatching 401k or 403b plans, and 48% at institutions without retirement plans for residents (P = 0.002). Fifty-nine percent of residents budgeted expenses, 27% had cash balances below $1000, 51% had paid interest charges on credit cards within the previous year, and 12% maintained unpaid credit card balances greater than $10,000. The median resident income was $38,400. CONCLUSIONS: A significant minority of residents appear not to make reasonable financial choices. Some residents save little because of a failure to budget, indebtedness, high projected income growth, or insufficient attention to personal financial management. Residents save more when they are eligible for tax-deferred retirement plans, particularly when their institution matches their contributions. Many residents would benefit from instruction concerning prudent financial management.

A perspective on laser lithotripsy: the fragmentation processes.

This paper describes in simple terms the physics of laser-calculus interactions and introduces a method with which physicians can understand or evaluate the application of any new laser technique for use in lithotripsy or other medical fields. Tissue optical properties and laser parameters govern the mechanism(s) of fragmentation of urinary or biliary calculi. Laser pulse energies for clinical lithotripsy range from Q0 = 20 mJ to 2 J for short-pulsed lasers to long-pulsed lasers, respectively. Lasers with short pulse durations (i.e., less than a few microseconds) fragment calculi by means of shockwaves following optical breakdown and plasma expansion of ionized water or calculus compositions or by cavitation collapse, thus manifesting a photoacoustical effect. Laser-tissue interactions involving dominant photomechanical or photoacoustical effects are usually stress confined. Long-pulsed lasers (i.e., >100 microsec), on the other hand, generate minimal acoustic waves, and calculi are fragmented by temperatures beyond the thresholds for vaporization of calculus constituents, melting, or chemical decomposition.

Third year medical student attitudes toward learning urology.

PURPOSE: We studied certain research questions, including the learning environments in which third year medical students perceive that they acquire urological knowledge and skills, and whether medical students interested in urology as a career have different perceived learning needs than those interested in other specialties. MATERIALS AND METHODS: A survey instrument was pilot tested and revised. The instrument elicited student perceptions of how they best learned urological diagnosis and skills. Student attitudes toward the third year urology rotation and career motivation toward urology were assessed. Consecutive students were surveyed after completing the third year urology rotation. RESULTS: Most students perceived that they learned to manage most urological problems by seeing patients in outpatient clinics and they learned to perform physical examination and urinalysis interpretation by seeing patients. The overall usefulness of various learning environments was highest for seeing patients in clinic, followed by resident teaching, following inpatients, independent reading, watching open surgery, formal conferences, watching endoscopic surgery and routine menial work. Students interested in urology as a career choice were equally motivated by seeing patients in clinic, the subject matter and seeing surgery. CONCLUSIONS: Third year medical students perceive that the most important urological learning environment is outpatient evaluation of patients. The urological learning needs of third year medical students are not different in those interested and not interested in urology as a career.

Erbium: YAG versus holmium:YAG lithotripsy.

PURPOSE: We test the hypothesis that erbium:YAG (Er:YAG) lithotripsy is more efficient than holmium:YAG (Ho:YAG) lithotripsy. MATERIALS AND METHODS: Human calculi composed of greater than 97% calcium oxalate monohydrate and cystine were studied. Calculi were irradiated in water using Er:YAG or Ho:YAG lasers. Er:YAG lithotripsy was done with a 425 microm sapphire optical fiber at a pulse energy of 50 mJ at 10 Hz. Ho:YAG lithotripsy was performed with a 365 microm low hydroxy optical fiber at a pulse energy of 500 mJ at 10 Hz or a 425 microm sapphire optical fiber at a pulse energy of 50 mJ at 10 Hz. Fragmentation was defined as the initial stone mass minus the final dominant fragment mass and normalized for incident laser fluence (energy per unit area of fiber tip). RESULTS: Mean fragmentation plus or minus standard deviation for calcium oxalate monohydrate was 38 +/- 27 mg for Er:YAG and 22 +/- 6 for Ho:YAG (low hydroxy silica fiber) versus 5 +/- 1 for Ho:YAG (sapphire fiber, p = 0.001). When fragmentation was normalized for incident laser fluence given different optical fiber sizes, mean fragmentation efficiency was 53.6 +/- 38.7 g-microm2/J for Er:YAG lithotripsy compared with 22.6 +/- 6.4 for Ho:YAG (low hydroxy silica fiber) lithotripsy (p = 0.04). Mean cystine fragmentation was 15 +/- 3 mg for Er:YAG versus 9 +/- 1 for Ho:YAG (sapphire fiber, p = 0.0005). CONCLUSIONS: Er:YAG lithotripsy is more efficient than Ho:YAG lithotripsy.

Use of the holmium:YAG laser for the impacted stone basket.

PURPOSE: During ureteroscopic basketing of ureteral calculi a stone may become engaged in the basket and the basket impacted in the ureter. We describe an endoscopic technique of managing the impacted basket and stone. MATERIALS AND METHODS: The ureteroscope is back loaded off of the basket, and passed into the ureter beside the basket and stone. The holmium:YAG laser is used to irradiate a basket wire, fracturing the wire and releasing the stone. The basket is removed and the stone managed by holmium:YAG lithotripsy. RESULTS: We successfully treated 3 consecutive patients with this technique. No injuries were observed. CONCLUSIONS: The holmium:YAG laser may be used to free an impacted stone basket containing a ureteral calculus.

In vitro comparison of shock wave lithotripsy machines.

PURPOSE: We tested the hypothesis that shock wave lithotripsy machines vary in the ability to fragment stones to small size. MATERIALS AND METHODS: Calcium oxalate monohydrate, calcium hydrogen phosphate dihydrate, cystine and magnesium ammonium phosphate hexahydrate calculi were fragmented in vitro with the 22 kV. Dornier HM3, section sign 20 kV. Storz Modulith SLX, parallel, 15.6 kV. Siemens Lithostar C, paragraph sign 24 kV. Medstone STS-T,** 26 kV. HealthTronics LithoTron 160,daggerdagger 20 kV. Dornier Doli section sign and 22.5 kV. Medispec Econolithdouble daggerdouble dagger lithotriptors. Stones were given 500 or 2,000 shocks, or the Food and Drug Administration limit. Post-lithotripsy fragment size was characterized using sequential sieves and compared. RESULTS: Stone mass was statistically similar in the cohorts (p >0.94). Fragment size decreased as the number of shocks increased when the machine and stone composition were constant. Magnesium ammonium phosphate hexahydrate calculi were completely fragmented by all devices. At Food and Drug Administration treatment limits the mean incidence per device of calcium hydrogen phosphate dihydrate, calcium oxalate monohydrate, cystine and magnesium ammonium phosphate hexahydrate stones rendered into fragments greater than 2 mm. was 0% for the HM3, Modulith SLX and Lithostar C, 10% for the STS-T, 3% for the LithoTron 160, 29% for the Doli and 18% for the Econolith (p = 0. 04); 0% for the HM3, Modulith SLX, Lithostar C, STS-T and LithoTron 160, 4% for the Doli and 9% for the Econolith (p = 0.15); 1% for the HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the LithoTron 160, 3% for the Doli and 9% for the Econolith (p = 0.44); and 1% for the HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the LithoTron 160, 3% for the Doli and 9% for the Econolith (p = 0.44), respectively. CONCLUSIONS: Shock wave lithotriptors vary in fragmentation ability. The HM3, Modulith SLX and Lithostar C machines yield smaller fragments than other machines.

The urology residency matching program in practice.

PURPOSE: We evaluate behaviors and attitudes among resident applicants and program directors related to the American Urological Association (AUA) residency matching program and recommend changes to improve the match. MATERIALS AND METHODS: Written questionnaires were mailed to 519 resident applicants and 112 program directors after the 1999 American Urological Association match. Subjects were asked about their observations, behaviors and opinions towards the match. RESULTS: Questionnaires were returned by 230 resident applicants and 94 program directors (44% and 83% response rates, respectively.) Of the resident applicants 75% spent $1,001 to $5,000 for interviewing. Of the program directors 47% recalled that applicants asked how programs would rank the applicant and 61% of applicants recalled that program directors asked applicants how they would rank programs. Dishonesty was acknowledged by 31% of program directors and 44% of resident applicants. Of program directors 82% thought applicants "lied", while 67% of applicants thought that programs "lied" (quotations indicate questionnaire language). Participants characterized their own dishonesty as "just playing the game" or they "did not feel badly." Of program directors 81% and of applicants 61% were "skeptical" or "did not believe" when informed they were a "high" or "number 1" selection. Being asked about marital status was recalled by 91% of male and 100% of female (p = 0. 02), if they had children by 53% of male and 67% of female, (p = 0. 03), and intent to have children by 25% of male and 62% of female (p <0.001), applicants, respectively. Free-form comments were written by 132 resident applicants and 28 program directors. The most frequent comments suggested the need to improve ethical behavior, modify the process so applications could be transmitted electronically and modify interviews to reduce applicant financial burden. Nine female applicants commented on their perceptions of sexual discrimination during the interviews. CONCLUSIONS: Resident applicants and program directors violate match code rules frequently. Program directors and resident applicants are skeptical of each other. Patterns of faculty behavior differ based on applicant gender. Interviews are costly for applicants. We recommend that 1) programs adopt policies to enhance fairness, 2) applications be filed electronically, 3) programs assist resident applicants with interview accommodation to reduce financial burden and 4) a post-interview code of limited or noncommunication be adopted.

Laser lithotripsy and cyanide.

BACKGROUND AND PURPOSE: Holmium:YAG lithotripsy of uric acid calculi produces cyanide. The laser and stone parameters required to produce cyanide are poorly defined. In this study, we tested the hypotheses that cyanide production: (1) varies with holmium:YAG power settings; (2) varies among holmium:YAG, pulsed-dye, and alexandrite lasers; and (3) occurs during holmium:YAG lithotripsy of all purine calculi. MATERIALS AND METHODS: Holmium:YAG lithotripsy of uric acid calculi was done using various optical fiber diameters (272-940 microm) and pulse energies (0.5-1.5 J) for constant irradiation (0.25 kJ). Fragmentation and cyanide were quantified. Cyanide values were divided by fragmentation values, and fragment sizes were characterized. To test the second hypothesis, uric acid calculi were irradiated with Ho:YAG, pulsed-dye, and alexandrite lasers. Fragmentation and cyanide were measured, and cyanide per fragmentation was calculated. Fragment sizes were characterized. Finally, Ho:YAG lithotripsy (0.25 kJ) of purine and nonpurine calculi was done, and cyanide production was measured. RESULTS: Fragmentation increased as pulse energy increased for the 550- and 940-microm optical fibers (P < 0.05). Cyanide increased as pulse energy increased for all optical fibers (P < 0.002). Cyanide per fragmentation increased as pulse energy increased for the 272-microm optical fiber (P = 0.03). Fragment size increased as pulse energy increased for the 272-microm, 550-microm, and 940-microm optical fibers (P < 0.001). The mean cyanide production from 0.25 kJ of optical energy was Ho:YAG laser 106 microg, pulsed-dye 55 microm, and alexandrite 1 microg (P < 0.001). The mean cyanide normalized for fragmentation (microg/mg) was 1.18, 0.85, and 0.02, respectively (P < 0.001). The mean fragment size was 0.6, 1.1, and 1.9 mm, respectively (P < 0.001). After 0.25 kJ, the mean amount of cyanide produced was monosodium urate stones 85 microg, uric acid 78 microg, xanthine 17 microg, ammonium acid urate 16 microg, calcium phosphate 8 microg, cystine 7 microg, and struvite 4 microg (P < 0.001). CONCLUSIONS: Cyanide production varies with Ho:YAG pulse energy. To minimize cyanide and fragment size, Ho:YAG lasertripsy is best done at a pulse energy < or = 1.0 J. Cyanide production from laser lithotripsy of uric acid calculi varies among Ho:YAG, pulsed-dye, and alexandrite lasers and is related to pulse duration. Cyanide is produced by Ho:YAG lasertripsy of all purine calculi.

Free electron laser lithotripsy: threshold radiant exposures.

PURPOSE: To determine the threshold radiant exposures (J/cm2) needed for ablation or fragmentation as a function of infrared wavelengths on various urinary calculi and to determine if there is a relation between these thresholds and lithotripsy efficiencies with respect to optical absorption coefficients. MATERIALS AND METHODS: Human calculi composed of uric acid, calcium oxalate monohydrate (COM), cystine, or magnesium ammonium phosphate hexahydrate (MAPH) were used. The calculi were irradiated in air with the free electron laser (FEL) at six wavelengths: 2.12, 2.5, 2.94, 3.13, 5, and 6.45 microm. RESULTS: Threshold radiant exposures increased as optical absorption decreased. At the near-infrared wave-lengths with low optical absorption, the thresholds were >1.5 J/cm2. The thresholds decreased below 0.5 J/cm2 for regions of high absorption for all the calculus types. Thresholds within the high-absorption regions were statistically different from those in the low-absorption regions, with P values much less than 0.05. CONCLUSIONS: Optical absorption coefficients or threshold radiant exposures can be used to predict lithotripsy efficiencies. For low ablation thresholds, smaller radiant exposures were required to achieve breakdown temperatures or to exceed the dynamic tensile strength of the material. Therefore, more energy is available for fragmentation, resulting in higher lithotripsy efficiencies.

Personal finances of urology residents in Canada.

PURPOSE: We examined how Urology residents in Canada manage their personal finances. MATERIALS AND METHODS: A survey instrument was designed to elicit information on demographics, expenses, savings and incomes. The questionnaire was completed by 40 Urology residents attending the 2000 Queen's Urology Exam Skills Training (QUEST) program. RESULTS: Twenty-eight residents (70%) had educational debt (median debt $50 000). Seventeen residents (45%) paid credit card interest charges within the last year. Four residents (10%) maintained an unpaid credit card balance > $7500 at 17% annual interest rate. Twenty-six residents (67%) contributed to Registered Retirement Savings Program (RRSP) accounts. Seventeen residents (44%) contributed to non-RRSP retirement accounts. Nineteen residents (50%) budgeted expenses. Median resident income was $45 000. Thirteen residents (34%) had cash reserves < $250. CONCLUSION: Many residents save little, and incur substantial debt over and above educational loans. Many residents would benefit from instruction concerning prudent financial management. Residents should be informed of the consequences of low saving and high debt.

Holmium: YAG lithotripsy: optimal power settings.

PURPOSE: We tested the hypothesis that holmium:YAG laser lithotripsy speed is best maximized by using low pulse energy at high pulse frequency. MATERIALS AND METHODS: To demonstrate that optical fiber damage increases with pulse energy and irradiation, the 365-microm optical fiber irradiated calcium hydrogen phosphate dihydrate (CHPD), calcium oxalate monohydrate (COM), cystine, magnesium ammonium phosphate hexahydrate (MAPH), and uric acid calculi at pulse energies of 0.5 to 2.0 J. Optical energy output was measured with an energy detector after 10 J to 200 J of total energy. To demonstrate that lithotripsy efficiency varies with power, fragmentation was measured at constant power settings at total energies of 200 J and 1 kJ with the 365-microm optical fiber. Fragmentation was measured for the 272-microm optical fiber at pulse energies of 0.5 J to 1.5 J at 10 Hz. To demonstrate that low pulse energy produces smaller fragments than high pulse energy, fragment size was characterized for COM and uric acid calculi after 0.25 kJ of irradiation using the 272-microm to 940-microm optical fibers at 0.5 J to 1.5 J. RESULTS: Damage to the 365-microm optical fiber was greatest for irradiation of CHPD, followed by MAPH, and COM (P<0.001). There was no significant optical fiber damage after cystine and uric acid lithotripsy. For the 365-microm optical fiber and CHPD, fragmentation after 200 J was greatest for pulse energies < or =1.0 J (P< 0.001). For other compositions, fragmentation was not statistically different among the power settings for constant irradiation. No significant difference was noted in fragmentation for any composition at different pulse energies (1.0 v. 2.0 J) for 1-kJ irradiation. However, for all compositions, the calculated lithotripsy speed was greatest at high power settings (P<0.001). For the 272-microm optical fiber, CHPD fragmentation was greatest for the 1.0-J pulse energy. The mean fragment size and relative quantity of fragments > or =2 mm both increased as pulse energy increased. CONCLUSIONS: Optical fiber degradation varies with stone composition, irradiation, and pulse energy. Holmium:YAG lithotripsy speed is maximized with higher power (either increased pulse energy or higher pulse frequency). Because low pulse energy may be safer and yields smaller fragments than high pulse energy, holmium:YAG lithotripsy speed is best increased by using pulse energies < or =1.0 J at a high repetition rate.

Holmium:YAG lithotripsy for large renal and bladder calculi: strategies for efficient lithotripsy.

Holmium:YAG lithotripsy is effective for all stone compositions, and high success rates may be expected. Large renal and bladder calculi may be treated effectively with Ho:YAG lasertripsy. Using angled optical fibers and increasing power settings may be particularly useful to increase lithotripsy speed.

Proteus mirabilis viability after lithotripsy of struvite calculi.

PURPOSE: We tested the hypotheses that Proteus mirabilis viability of struvite calculi differs after exposure to different lithotripsy modalities and that the photothermal mechanism of holmium:YAG lithotripsy is antibacterial. MATERIALS AND METHODS: Human calculi of known struvite composition (greater than 90% magnesium ammonium phosphate hexohydrate) were incubated with P. mirabilis. Calculi were randomly distributed and fragmented with no lithotripsy (controls), or shock wave, intracorporeal ultrasonic, electrohydraulic, pneumatic, holmium:YAG or pulsed dye laser lithotripsy. After lithotripsy fragments were sonicated and specimens were serially plated for 48 hours at 38C. Bacterial counts and the rate of bacterial sterilization were compared. RESULTS: Median bacterial counts (colony-forming units per ml.) were 8 x 10(6) in controls and 3 x 10(6) in shock wave, 3 x 10(7) in ultrasonic, 4 x 10(5) in electrohydraulic, 8 x 10(6) in pneumatic, 5 x 10(4) in holmium:YAG and 1 x 10(6) in pulsed dye laser lithotripsy cases (p <0.001). The rate of bacterial sterilization was 50% for holmium:YAG lithotripsy treated stones versus 0% for each of the other cohorts (p <0.01). CONCLUSIONS: P. mirabilis viability varies among lithotrites. The photothermal mechanism of holmium:YAG lithotripsy is antibacterial.

Holmium:YAG lithotripsy in children.

PURPOSE: We determined the safety and efficacy of holmium:YAG lithotripsy in children. MATERIALS AND METHODS: We retrospectively reviewed the records of all holmium:YAG lithotripsy done in patients 17 years old or younger. Demographic, preoperative, intraoperative and postoperative data were collected. RESULTS: A total of 9 boys and 10 girls (26 stones) with a mean age of 11 years (range 1 to 17) were treated with holmium:YAG lithotripsy, which was chosen as initial therapy in 10 (53%). Retrograde ureteroscopy was performed in 15 patients to treat 13 ureteral and 6 renal calculi, and percutaneous nephrolithotripsy was done in 4 to treat 3 ureteral and 4 renal calculi. A complete stone-free outcome after 1 procedure was achieved in 16 children (84%) and 3 patients were rendered stone-free after 2 procedures. No patient had an intraoperative injury. Followup ranged from 0.5 to 12 months (mean 3). Followup imaging has shown no evidence of stricture or hydronephrosis. CONCLUSIONS: Holmium:YAG lithotripsy is safe and effective in children. It is a reasonable option for failed shock wave lithotripsy, or in children with a known durile stone composition or contraindications to shock wave lithotripsy.