Stone fragility: its therapeutic implications in shock wave lithotripsy of upper urinary tract stones

In Vivo Analysis of Urinary Stones With Dual-Energy Computed Tomography

OBJECTIVE

Formation mechanisms and treatment of the urinary stones are different, depending on their chemical structure. Therefore, determining the stone type plays a key role in planning treatment and preventive measures. Computed tomography (CT), with the use of dual-energy technology in recent years, has made it possible to do in vivo analysis of urinary stones. In this study, we aimed to evaluate the diagnostic efficacy of dual-energy CT (DECT) and compare its results with in vitro analysis, which is accepted as a gold standard for analysis of urinary stones.

MATERIALS AND METHODS

The DECT examinations were performed on 373 patients using 128-slice dual-source CT scanner. Analysis of attenuation ratios in the high and low kilovoltage peak values of the stone was performed at workstation, and stones were classified as hydroxyapatite, calcium oxalate, cystine, and uric acid. On follow-up, the stone was obtained in 35 patients as a result of surgery or passed spontaneously. The DECT analysis and in vitro analysis results were compared and statistically evaluated.

RESULTS

In all patients, 136 hydroxyapatite, 160 calcium oxalate, 57 uric acid, and 20 cystine stones were detected with DECT. In vitro analyses of the stones were performed in 35 patients, and 8 hydroxyapatite, 18 calcium oxalate, 6 uric acid, and 3 cystine stones were revealed. When DECT analysis results were compared with in vitro analysis results, stone types were detected correctly in 32 (91.4%) patients and incorrectly in 3 (8.6%) patients. Especially all uric acid and cystine stones were correctly detected with DECT.

CONCLUSIONS

With advanced postprocess analysis methods, DECT is able to analyze urinary stones. The DECT is found superior especially in detecting uric acid and cystine stones. Its success in detecting hydroxyapatite and calcium oxalate stones is also high. When in vivo analyses of the stones are performed with DECT, it will be possible to make a contribution to the personalization and optimization of the treatment.

Dual-energy computed tomography of canine uroliths

OBJECTIVE To determine whether dual-energy CT (DECT) could accurately differentiate the composition of common canine uroliths in a phantom model. SAMPLE 30 canine uroliths with pure compositions. PROCEDURES Each urolith was composed of ≥ 70% struvite (n = 10), urate (8), cystine (5), calcium oxalate (4), or brushite (3) as determined by standard laboratory methods performed at the Canadian Veterinary Urolith Centre. Uroliths were suspended in an agar phantom, and DECT was performed at low (80 kV) and high (140 kV) energies. The ability of low- and high-energy CT numbers, DECT number, and DECT ratio to distinguish uroliths on the basis of composition was assessed with multivariate ANOVA. RESULTS No single DECT measure differentiated all urolith types. The DECT ratio differentiated urate uroliths from all other types of uroliths. The DECT and low-energy CT numbers were able to differentiate between 8 and 7 pairs of urolith types, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that DECT was unable to differentiate common types of canine uroliths in an in vitro model; therefore, it is unlikely to be clinically useful for determining urolith composition in vivo. Given that the primary reasons for determining urolith composition in vivo are to predict response to shock wave lithotripsy and develop a treatment plan, future research should focus on the correlation between DECT measurements and urolith fragility rather than urolith composition.

In vivo characterization of urinary calculi on dual-energy CT: going a step ahead with sub-differentiation of calcium stones

BACKGROUND

The role of dual-energy computed tomography (DECT) in characterization of urinary calculi is evolving and literature regarding differentiation of calcium calculi is sparse and confounding.

PURPOSE

To evaluate the capability of DECT in assessing the urinary calculi composition in vivo, especially in differentiating various types of calcium calculi.

MATERIAL AND METHODS

One hundred and twenty patients underwent DECT for characterization of urinary calculi. Seventy patients with 114 calculi, including 93 calcium stones, were retrospectively analyzed. DE ratios and attenuation differences were compared using ANOVA and receiver-operating-characteristic (ROC) analysis was done to predict cut-off values, in particular for detecting calcium-oxalate-monohydrate (COM) stones.

RESULTS

DE ratio ≤1.14 accurately detected uric acid calculi, ≥1.29 was definitive for calcium and intermediate values were characteristic of cystine stones. DE ratios were significantly different between group 1 (COM [n = 32]; mean 1.376 ± 0.041), group 2 ([calcium oxalate dihydrate (COD) + COM] [n = 51]; 1.416 ± 0.048), and group 3 ([carbonate apatite (CaP) + COD + COM] [n = 10]; 1.468 ± 0.038) (group 1 vs. 2, P = 0.001; 1 vs. 3, P = 0.000; 2 vs. 3, P = 0.004). More importantly, pure COM calculi (group 1) had significantly lower DE ratio compared with mixed calcium calculi (groups 2 and 3) (P = 0.000). Attenuation differences (between low and high kV images) could not distinguish between COM and mixed calculi. ROC analysis for detection of COM calculi yielded AUC of 0.770 with cut-off DE ratio 1.385 (sensitivity 65.6%, specificity 82%) and value <1.335 was seen only with COM calculi (100% specificity).

CONCLUSION

DECT can be employed for in vivo differentiation of various types of calculi and for detection of relatively lithotripsy-resistant COM calculi.

Current role of microperc in the management of small renal calculi

'Microperc' is a recently described technique in which percutaneous renal access and lithotripsy are performed in a single step using a 16 G micropuncture needle. 'Mini-microperc' is a further technical modification in which an 8 Fr sheath is used to allow insertion of ultrasonic or pneumatic lithoclast probe with suction. The available evidence indicates that microperc is safe and efficient in the management of small renal calculi in adult and pediatric population. It can also be used for renal calculi in ectopic kidneys and bladder calculi. The high stone clearance rate and lower complication rate associated with microperc make it a viable alternative to retrograde intrarenal surgery.

Imaging-based assessment of the mineral composition of urinary stones: an in vitro study of the combination of hounsfield unit measurement in noncontrast helical computerized tomography and the twinkling artifact in color Doppler ultrasound

We evaluated the value of combining noncontrast helical computerized tomography (NCHCT) and color Doppler ultrasound in the assessment of the composition of urinary stones. In vitro, we studied 120 stones of known composition, that separate into the five main types: 18 calcium oxalate monohydrate (COM) stones, 41 calcium oxalate dihydrate (COD) stones, 24 uric acid stones, 25 calcium phosphate stones and 12 cystine calculi. Stones were characterized in terms of their Hounsfield density (HU) in NCHCT and the presence of a twinkling artifact (TA) in color Doppler ultrasound. There were statistically significant HU differences between calcium and non-calcium stones (p < 0.001), calcium oxalate stones and calcium phosphate stones (p < 0.001) and uric acid stones and cystine calculi (p < 0.001) but not between COM and COD stones (p = 0.786). Hence, the HU was a predictive factor of the composition of all types of stones, other than for COM and COD stones within the calcium oxalate class (p > 0.05). We found that the TA does not enable differentiation between calcium and non-calcium stones (p > 0.999), calcium oxalate stones and calcium phosphate stones (p = 0.15), or uric acid stones and cystine calculi (p = 0.079). However, it did reveal a significant difference between COM and COD stones (p = 0.002). The absence of a TA is a predictive factor for the presence of COM stones (p = 0.008). Hence, the association of NCHCT and Doppler enables the accurate classification of the five types of stones in vitro.

Assessment of stone composition in the management of urinary stones

Several explanations have been suggested to account for the failure of extracorporeal shockwave lithotripsy (ESWL) treatment in patients with urinary stones, including large stone volume, unfavorable stone location or composition and the type of lithotriptor used. Unfavorable stone composition is considered a major cause of failure of ESWL treatment, and consequently knowledge of the stone composition before treatment is initiated is desirable. Plain abdominal radiographs cannot accurately determine either stone composition or fragility, and although the CT attenuation value in Hounsfield units (HU) (that is, normalized to the attenuation characteristics of water) is useful, this parameter has limited value as a predictor of stone composition or the response to ESWL treatment. By contrast, stone morphology as visualized by CT correlates well with both fragility and susceptibility to fragmentation by ESWL. For patients prone to recurrent calculi, analyses of stone composition are especially important, as they may reveal an underlying metabolic abnormality. The development of advanced imaging technologies that can predict stone fragility is essential, as they could provide extra information for physicians, enabling them to select the most appropriate treatment option for patients with urinary stones.

[The influence of lithotripsy methods on the incidence of auxilary procedures after ureteric stone desintegration]

INTRODUCTION/AIM

Localization of ureteric stones and the difference in disintegration success are the most important but not the only factors in choosing the first treatment approach to ureteric stones. The aim of the study was to investigate the incidence of auxiliary procedures after different ureteric stones lithotripsy modalities.

METHODS

In a prospective bicentric study 260 patients with ureteric stones were analyzed. The patients weve divided into two groups: group I--120 patients subjected to extracorporeal shock ware lithotripsy (ESWL) treatment and group II--140 patients treated endoscopicly with ballistic lithotripsy using "Swiss" Lithoclast.

RESULTS

Endoscopic treatment of all distal ureteric stones was significantly more successful than ESWL, but not significantly more successful than ESWL regarding proximal ureteric stones except for stones larger than 100 mm2 that were significantly better treated with endoscopic method. There was no general significant difference in auxiliary procedures rate after lithotripsy between the two groups. In the group I auxiliary procedures were significantly more performed than in the group II after the lithotripsy of stones larger than 100 mm2, calcium-oxalat-monohydrate stones and highly significantly more performed after the treatment of stones located in the iliac ureteric portion and impacted stones. After the lithotripsy of lumbar ureteric stones and multiple stones situated in different ureteric portions additional procedures were highly significantly more necessary in the goup II than in the group I.

CONCLUSION

Being significantly more successful comparing to ESWL, ureteric stone treatment with "Swiss" Lithoclast should be considered the first therapeutic option for all, especially impacted stones located in iliac and pelvic ureter. In spite of a statistically significant difference in success rate, ESWL should be performed as the first treatment option in all cases of lumbar stones as well as multiple stones located in different ureteric portion because of lower auxiliary procedures rate except for stones larger than 100 mm2 that should be primarily treated endoscopicly.

Prospective randomized comparison of a combined ultrasonic and pneumatic lithotrite with a standard ultrasonic lithotrite for percutaneous nephrolithotomy

PURPOSE

To compare the efficiency and cost effectiveness of a combined pneumatic and ultrasonic lithotrite (Lithoclast Ultra) and a standard ultrasonic lithotrite, (LUS-1) during percutaneous nephrolithotomy.

MATERIALS AND METHODS

In a prospective randomized trial, 30 patients undergoing percutaneous nephrolithotomy (PCNL) were randomized to PCNL with either the combined pneumatic and ultrasonic lithotrite (PUL) or a standard ultrasonic lithotrite (SUL). Patient demographics, stone composition, location, pre- and post-operative stone burden, fragmentation rates, and device failures were compared.

RESULTS

There were 13 patients in the PUL group and 17 patients in the SUL group. Stone burden and location were equal. Overall, 64% of the PUL group had hard stones (defined as stones that were either pure or a mixture of cystine [3], calcium oxalate monohydrate [CaOxMono; 2], and calcium phosphate [CaPO4; 2]), and four had soft stones (3 struvite and 1 uric acid [UA]). In the SUL group, there were eight hard stones (5 CaOxMono and 3 CaPO4), and six soft stones (4 calcium oxalate dihydrate [CaOxDi] and 2 UA) (P = 0.51). Stone composition data were unavailable for five patients. Fragmentation time for the PAL was 37 minutes versus 31.5 minutes for the SUL (P = 0.22). Stone retrieval and mean operative times were similar for both groups. There were a total of three (23.1%) device-related problems in the PUL group, and eight (47%) in the SUL group. There was one (7.7%) device malfunction in the PUL group due to probe fracture. There were two (11.7%) device failures in the SUL group; one failure required the device to be reset every 30 minutes, and the second was an electrical failure. Suction tubing obstruction occurred twice (15.3%) in the PUL group and 35.3% in the SU group (P = 0.35). The stone-free rates for the PUL and SUL were 46% and 66.7%, respectively (P = 0.26).

CONCLUSION

Although the PUL was more costly, stone ablation and clearance rates were similar for both the combined pneumatic and ultrasonic device and the standard ultrasonic device. When stratified with respect to stone composition, the PUL was more efficient for harder stones, and the SUL was more efficient for softer stones.

Stone composition: where do we stand?

Kidney stones are a common disorder of the urinary tract. Nephrolithiasis is a morbid and expensive disease. The prevalence and incidence are estimated at 5-10% and 100-300/100,000/year, respectively. Relapses occur in 50-70% of all cases. For these reasons, prevention of stone formation is of great importance. Knowing the composition of the calculus is thus fundamental for a more complete evaluation of the metabolic study. The nature of the calculus in fact helps the physician to find a convenient metaphylaxis consisting of both sanitary and therapeutic measures. Study of the composition of urinary stones remains one of the most interesting aspects of the lithiasic pathology today. Presently crystallographic examination constitutes one of the most precise and less expensive methodologies to identify the nature of the concretion. This method also allows the urologist to catalogue the typology of the lithiasis during endoscopy.

Stepwise shock wave lithotripsy: Results of initial study for the treatment of urinary stones in childhood

OBJECTIVE

To assess the effectiveness of stepwise extracorporeal shock wave lithotripsy in the treatment of upper urinary stones in childhood.

PATIENTS AND METHODS

Between August 1998 and August 2003, 31 patients were treated for renal or ureteric stones. All treatments were performed with Dornier Compact Delta lithotripter. The number of shock wave was limited to maximum 3000 shock waves/session. The voltage was started at 10 kV and increased stepwise to 12.75 kV. Stone clearance was assessed at 3 months. The stone free state was defined as the absence of stone fragments.

RESULTS

Total 31 stones (24 renal and 7 ureteral stones) were treated. The age of the patients was median 8 (min-max: 0.8-12) years. The length of the stones was median 1 (min-max: 0.5-1.5) cm for renal stones and median 0.5 (min-max: 0.5-1) cm for ureteral stones. As an auxiliary procedure, open pyelolithotomy was required for 1 patient. The overall stone free rates for renal and ureter stones were 79% and 100%, respectively. Post-treatment insignificant hematuria was observed in all cases.

CONCLUSION

Stepwise shock wave lithotripsy was an effective procedure for the treatment of urinary calculi in childhood.

[Extra corporeal shock wave lithotripsy (ESWL) procedure in urology]

Since 1980, extra corporeal shock wave lithotripsy (ESWL) has become the first line treatment for most stones in adults and children. The indications are based on criteria depending on localization, chemical composition and size of the renal and ureteral calculi. Since the DORNIER HM 3 which remains the gold standard of first generation lithotripters, many devices of second and third generation have been built (electro hydrolic, piezo electric and electromagnetic) with fluoroscopic and ultrasound localization systems. SWL may now be performed on an out-patient basis without anaesthesia or under neuroleptic analgesia. Indications and evaluation criteria on 3 months plain abdominal X-ray are better defined since 1996. Nevertheless, comparison of reported results remains difficult due to the multiplicity of lithotripter types and the lack of consensus on efficacy criteria. Today, the third generation of mobile electromagnetic lithotripters give an average of 80% stone free rate of patients with kidney and ureteral calculi whatever the localization and size.

Spectrum of stone composition: structural analysis of 1050 upper urinary tract calculi from northern India

BACKGROUND

The purpose of the present paper was to study the spectrum of stone composition of upper urinary tract calculi by X-ray diffraction crystallography technique, in patients managed at All India Institute of Medical Sciences.

METHODS

Between 30 April 1998 and 31 March 2003, a total of 1050 urinary calculi (900 renal, 150 ureteric) were analyzed. The stone fragments were collected after extracorporeal shock-wave lithotripsy, or retrieval by endoscopic (percutaneous nephrolithotomy, ureterorenoscopy), laparoscopic and various open surgical procedures. The structural analysis of the stones was done using X-ray diffraction crystallography.

RESULTS

Four types of primary and three secondary X-ray diffraction patterns were obtained. The primary patterns were as follows. Pattern A, well organized crystalline structure; pattern B, moderately organized crystalline structure; pattern C, poorly organized crystalline structure; pattern D, very poorly organized crystalline structure. The three secondary patterns mainly highlighted the mixed variety of stones. These patterns were further analyzed and compared with standard X-ray diffraction (powder) photographs. Of the 1050 stones analyzed, 977 (93.04%) were calcium oxalate stones, out of which 80% were calcium oxalate monohydrate (COM) and 20% were calcium oxalate dihydrate (COD). Fifteen were struvite (1.42%) and 19 were apatite (1.80%). Ten were uric acid stones (0.95%) and the remaining 29 (2.76%) were mixed stones (COM + COD and calcium oxalate + uric acid, calcium oxalate + calcium phosphate, and calcium phosphate + magnesium ammonium phosphate). A total of 89.98% of staghorn stones were made of oxalates (COM/+COD) and only 4.02% were struvite.

CONCLUSION

Urinary stone disease in the Indian population is different from that in Western countries, with a larger percentage of patients having calcium oxalate stones, predominantly COM. Also, the majority of staghorn stones (89.98%) were made of oxalates.