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G M Preminger

Publications and source records attributed to G M Preminger.

At least 19 recordsLinked to original sources
PubMed1992

Microhardness measurements of renal calculi: regional differences and effects of microstructure.

Microhardnesses of five types of renal calculi: calcium apatite (82.5%)/magnesium ammonium phosphate hydrogen (10%)/calcium oxalate monohydrate (7.5%); calcium apatite (95%)/calcium oxalate monohydrate (5%); magnesium ammonium phosphate hydrogen (90%)/calcium apatite (10%); calcium oxalate monohydrate (85%)/calcium apatite (15%); and cystine (100%) were measured. Using Knoop and Vickers indenters the effects of chemical composition and microstructure on the microhardness measurement were assessed. Calcium oxalate monohydrate, magnesium ammonium phosphate hydrogen, and cystine stones, without apparent structure pattern, showed neither regional nor directional differences in their microhardness. In contrast, calcium apatite stones, with distinctly concentric laminae structure, showed regional variations which were correlated with the chemical composition of stone constituents. Scanning electron microscopy of the indenter impressions were taken to help in interpreting the directional dependence in Knoop hardness measurements with respect to the microstructure of the calculi. Vickers measurements showed the crystalline stones were isotropic within a layer. Combined results of Knoop and Vickers measurements indicate that the anisotropic Knoop hardness readings seen in the laminated regions were structural but not material-based. Implications of the results for the fragmentation of renal calculi in extracorporeal shock wave lithotripsy are discussed.

Hardness Tests↗
PubMed1992

A comparison of stone damage caused by different modes of shock wave generation.

A standard stone phantom was used to compare stone damage after extracorporeal shock wave administration from electrohydraulic, electromagnetic and piezoelectric lithotripters. For each machine, a low and high shock wave intensity setting was chosen: 18 & 24 kV for electrohydraulic; 16 & 19 kV for electromagnetic; power levels 1 and 4 for piezoelectric. The shock wave was focused either at the front (surface facing the wave source) or back surface of the stone and 50, 100, 200 or 400 shocks were delivered to different stone groups. Effects of varying physical properties in the stone phantom were also investigated. Stone damage was described in terms of volume loss and both depth and width of the resulting damage crater. At the lower intensity settings, all three machines produced stone volume loss which was linearly related to the number of shock delivered. At higher intensity settings, volume loss increased rapidly as the number of shocks increased. With the same number of shocks, stone volume loss was greatest with the electrohydraulic machine, followed by electromagnetic and piezoelectric lithotripters for both low and high intensity settings. Damage craters from the piezoelectric device were narrow and deep; those from the electromagnetic machine were of the shape of a right angle circular cone; whereas those from the electrohydraulic lithotripter were shallow and wide. At the high intensity settings, damage from the piezoelectric and electrohydraulic lithotripters appeared to depend upon the position of the focal point with a higher volume loss when the shock waves were targeted at the front surface of the stone. For the electromagnetic device, a higher volume loss was found when we positioned the focal point at the back surface of the stone phantom. Stone phantoms with lower mechanical strength and acoustic impedance were more easily damaged than those with higher values. Finally, a computer regression model was developed to express volume loss in terms of the intensity setting, focal position and number of shocks for each lithotripter.

Calculi↗
PubMed1992

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.

Adult↗
PubMed1992

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.

Calcium↗
PubMed1991

A comparison of renal damage induced by varying modes of shock wave generation.

To evaluate for the possible differences in the extent of pathologic injury occurring following treatment with various lithotripsy modalities, we subjected rabbits to treatment on either an electrohydraulic, electromechanical, or piezoelectric lithotripter. Functional evaluations by enzymuria failed to reveal any difference in the extent of damage between the lithotripters. Pathologic evaluation of the kidneys revealed that both electrohydraulic and electromechanical lithotripsy resulted in an increased instance of acute subcapsular hematoma and fibrosis when compared to piezoelectric treated kidneys (p less than 0.001). Despite the definitive differences noted in the acute animals, there was no significant variation in the area of permanent renal damage that occurred between the various lithotripters.

Acetylglucosaminidase↗
PubMed1991

Temporal effects of shock wave lithotripsy.

Previous studies have demonstrated that renal parenchymal injury following extracorporeal shock wave lithotripsy is dependent upon shock wave power as well as the total number of shock waves administered. In order to determine the deleterious effects of temporal versus cumulative doses of shock wave administration, adult female rabbits were divided into five groups receiving either: 1000 shock waves in one session; 2000 shock waves in one session; 2000 shock waves in two sessions, one week apart; unilateral nephrectomy without lithotripsy; or anesthesia only as control population. One month following lithotripsy, renal functional studies for gamma glutamyl transferase and N-acetyl-beta-glucosaminidase revealed persistent enzymuria in the animals treated with 2000 shocks in one session. Pathologic studies in these animals confirmed an increased area of periglomerular and intratubular fibrosis when compared to animals managed by either 1000 shocks or 2000 shocks in divided doses (p less than 0.01). These findings suggest the importance of avoiding single treatments with large doses of shock waves and favor the administration of multiple small-doses of shock waves to minimize renal damage during the treatment of patients with hard or large calculi.

Acetylglucosaminidase↗
PubMed1991

Shock wave physics.

Extracorporeal shock wave lithotripsy has significantly altered the management of symptomatic renal and ureteral calculi. Yet in an effort to limit the potentially harmful effects of shock waves, while still maintaining or maximizing stone fragmentation, one must understand basic shock wave physics. This report presents a brief overview of the physical properties of shock waves and describes three different areas of shock wave physics investigation: measurement of shock wave pressures, assessment of stone fragmentation, and development of a stone phantom to allow the comparison of various lithotripsy devices. It is only through additional study of the basic physics of high-energy shock waves that we will be able to further enhance the clinical benefits of extracorporeal shock wave lithotripsy. Further understanding of the individual characteristics of a shock wave pressure field such as peak positive pressure, peak negative pressure, pulse duration, and size/shape of the focal region will allow the subsequent enhancement of stone fragmentation while minimizing the potential for shock wave injury to surrounding tissues.

Humans↗
PubMed1990

Laxative abuse as a cause for ammonium urate renal calculi.

Nine women with laxative abuse and predominantly ammonium urate renal calculi underwent metabolic studies to identify common chemical abnormalities and determine pathophysiology. The 24-hour urine studies demonstrated marked decreases in volume (902 cm.3), sodium (28 mEq.), citrate (116 mg.) and potassium (21 mEq.). A significant elevation in ammonium urate supersaturation was found compared to control subjects when studied by the computer model EQUIL 2. Of the patients 7 had 1 or more urine specimens positive for phenolphthalein. Gastrointestinal loss of fluid and electrolytes allowed for chronic extracellular volume depletion. Intracellular acidosis was present as judged by low urinary citrate and potassium. The fact that the ion product for ammonium urate is increased significantly compared to controls reflects the stated pathophysiological changes. Laxative abuse should be suspected whenever a woman has an ammonium urate renal calculus in sterile urine.

Adult↗
PubMed1990

Brucella orchitis: a rare cause of testicular enlargement.

The differential diagnosis of the acutely enlarged testis includes numerous benign and malignant disease processes. Most are treated with radical orchiectomy due to difficulty in differentiating between these disorders preoperatively. Saving the involved testis, prevention of recurrent infectious disease in the opposite testis and prevention of systemic manifestations of testicular disease are but a few of the reasons for accurate diagnosis of the acute scrotum. We report a rare case of brucellosis presenting as an acute scrotal mass and stress the importance of accurately identifying the specific etiology of testicular pathology to prevent long-term morbidity.

Acute Disease↗
PubMed1990

Extracorporeal shock wave lithotripsy. An update.

Extracorporeal shock wave lithotripsy has revolutionized the treatment of urinary calculi. It should be considered the treatment of choice for renal stones smaller than 2 cm and for the majority of ureteral calculi, under which circumstances success rates approaching 80 to 90 per cent may be anticipated. Larger renal calculi or impacted ureteral stones probably should be managed by endoscopic techniques with or without adjunctive intracorporeal (ultrasonic or electrohydraulic) lithotripsy or laser fragmentation. Recent modifications in lithotripter design have been focused on the development of pain-free lithotripsy. Concomitant with a decrease in power, however, is an attendant decrease in the efficiency with which stones can be fragmented, resulting in an increase in the number of lithotripsy treatments required for adequate stone fragmentation. Additionally, sonography is assuming an increasing role in stone localization, and its use will require sonographic training on the part of the urologist. Biliary lithotripsy has been promising in preliminary European studies, with success rates approaching 90 per cent. It must be noted, however, that the U.S. experience has not been as impressive. Moreover, only 20 to 30 per cent of patients referred for biliary lithotripsy appear to be optimal candidates for this new technique. Adjunctive dissolution of gallstones with chronic oral medical therapy may be required after biliary lithotripsy, and long-term follow-up studies still need to be performed. Finally, the potential deleterious effects of extracorporeal shock wave lithotripsy must always be kept in mind. Although the majority of clinical and animal investigations have documented no significant long-term alterations in renal function, care must still be exercised when performing lithotripsy with the knowledge of the potential for long-term injurious effects on the functioning renal parenchyma.

Animals↗
PubMed1989

Ureteral stenting during extracorporeal shock wave lithotripsy: help or hindrance?

We retrospectively reviewed the outcome of extracorporeal shock wave lithotripsy in patients with renal calculi less than 3 cm. in size who were treated at a large multi-user lithotripsy center. Patients in whom indwelling ureteral stents were placed before lithotripsy treatment were subjected to higher levels of total power (shocks times voltage), yet the rate free of stones did not differ from those treated without a stent. In addition, the patients with internal ureteral stents experienced a significantly higher incidence of urinary urgency (43 versus 25 per cent) and hematuria (40 versus 23 per cent) than nonstented patients, respectively (p less than 0.05). Also, the duration of bladder discomfort was longer for stented patients (26 versus 13 per cent) as was the duration of urinary frequency (31 versus 16 per cent), compared to nonstented patients (p less than 0.05). The results suggest that use of an indwelling ureteral stent may not contribute to a higher rate free of stones for the treatment of small to medium sized renal calculi and, in fact, it may make the treatment more uncomfortable for the patient than performing lithotripsy without ureteral stenting. Of course, in selected cases (solitary kidney, large stone burden and aid in stone localization) ureteral stenting has a useful adjunctive role in extracorporeal shock wave lithotripsy.

Catheters, Indwelling↗
PubMed1989

Bladder perforation secondary to clean intermittent catheterization.

Clean intermittent catheterization has been an effective treatment for the management of patients with a neurogenic bladder during the last 15 years. Reported complication rates have been low and the majority of these problems have been minor. While significant problems are seen only rarely during clean intermittent catheterization, we recently diagnosed 2 potential life-threatening complications: bladder perforation and bladder necrosis. We present our experience with these major problems associated with routine clean intermittent catheterization.

Abdomen, Acute↗
PubMed1989

The metabolic evaluation of patients with recurrent nephrolithiasis: a review of comprehensive and simplified approaches.

The advent of percutaneous nephrostolithotomy and extracorporeal shock wave lithotripsy has definitely altered the way in which symptomatic renal calculi are approached. However, these new techniques should not affect the need for appropriate diagnostic evaluation and institution of medical treatment for the prevention of recurrent nephrolithiasis. A diagnostic evaluation should identify underlying physiological and environmental defects responsible for stone formation, as well as identify specific medical disorders that cause recurrent stone formation. With this information one then can construct an appropriate treatment program that will prevent the occurrence of additional calculi. Comprehensive metabolic protocols have evolved from tedious inpatient procedures to more convenient outpatient tests that can be performed in approximately 2 weeks. In addition, the advent of automated urinalysis packages has allowed many physicians access to reliable, sophisticated technology. Further dissemination of these simplified metabolic protocols will enable more accurate diagnosis of recurrent stone disease and, hopefully, permit the institution of appropriate medical therapy by a wider group of treating physicians.

Calcium↗
PubMed1988

Localized amyloidosis of the urethra: diagnostic implications and management.

Localized amyloidosis of the urethra is a rare pathological entity that may resemble neoplastic disease. Biopsy is required to make the appropriate diagnosis. Although localized therapy is available for obstructing, symptomatic lesions, asymptomatic lesions may be followed with conservative management and spontaneous regression has been reported. In addition, an appropriate medical evaluation should be performed to determine the presence of systemic amyloidosis.

Amyloidosis↗
PubMed1988

Alkali action on the urinary crystallization of calcium salts: contrasting responses to sodium citrate and potassium citrate.

Alkali therapy is used commonly to prevent recurrent stone formation in patients with distal renal tubular acidosis. We compared the effects of potassium citrate to those of sodium citrate in 6 well defined cases of incomplete distal renal tubular acidosis. The patients were studied during a control phase, during potassium citrate treatment (80 mEq. per day) and during sodium citrate treatment (80 mEq. per day) chosen in random order. Potassium citrate caused a decrease in urinary calcium and a significant increase in urinary citrate that resulted in a significant decrease in the urinary saturation of calcium oxalate. It did not alter the saturation of brushite and sodium urate. However, while sodium citrate also was able to increase the urinary citrate level, there was no decrease in the urinary calcium (owing to the increased sodium load). Thus, the urinary saturation of calcium oxalate did not decrease as much as with potassium citrate and the saturation of brushite increased significantly. Moreover, the urinary saturation of sodium urate increased significantly owing to the enhanced sodium excretion. The results suggest that potassium citrate therapy may retard the crystallization of calcium oxalate and may not cause calcium phosphate crystallization. In contrast, sodium citrate may have no effect or it sometimes may accentuate the crystallization of calcium salts. Thus, our study supports the potential clinical advantage of potassium citrate therapy over sodium alkali treatment in patients with incomplete distal renal tubular acidosis and recurrent calcium nephrolithiasis.

Acidosis, Renal Tubular↗