Metabolic and urinary risk factors associated with Randall's papillary plaques

BACKGROUND AND PURPOSE: Increasing evidence suggests that Randall's plaques contribute to the pathogenesis of urinary stone formation. The purpose of our study was to evaluate the urinary risk factors of stone patients who underwent endoscopic mapping of their calices for Randall's plaques. PATIENTS AND MATERIALS: Patients (N = 143) having endoscopic procedures to remove upper tract calculi or for other purposes underwent mapping of their calices for Randall's plaques. Plaque incidence and pattern were correlated with the stone composition and urinary risk factors found on subsequent metabolic evaluation. RESULTS: Papillary plaques were found more commonly in patients having calcium oxalate stones than in patients with other stone types and patients without a history of stones. Papillary plaque incidence and pattern did not correlate with any specific urinary risk factor; however, patients with plaques tended to exhibit a higher incidence of all risk factors. Plaque severity tended to be greater in patients exhibiting hypercalciuria. CONCLUSIONS: Randall's plaques are found most frequently in patients with calcium oxalate stones and are most important in the pathogenesis of calcium oxalate nephrolithiasis. Stone patients with papillary plaques are more likely to exhibit abnormalities in their urinary milieu than are patients without papillary plaques.     

Endoscopic evidence of calculus attachment to Randall's plaque

PURPOSE: It has been proposed that calcium oxalate calculi begin as small stones attached to the renal papillae at sites of Randall's plaque. However, no study has investigated the prevalence of attached stones in calcium oxalate stone formers or the relationship between stone attachment site and Randall's plaque. In this study we used endoscopic examination of renal papillae in stone formers undergoing percutaneous nephrolithotomy to investigate both issues. MATERIALS AND METHODS: Idiopathic calcium oxalate stone formers undergoing PNL for stone removal were enrolled in this study. Multiple papillae were examined and images were recorded by digital video. The presence or absence of papillary plaque and attached stones was noted, as was the site of stone attachment. RESULTS: In 23 patients, 24 kidneys and 172 renal papillae were examined. All kidneys were found to have papillary plaque and 11 of the patients had attached stones. Most papillae (91%) contained plaque. CONCLUSIONS: The prevalence of attached stones in calcium oxalate stone formers (48%) is greater than that previously reported for the general population. Attachment appears to be on Randall's plaque. The high prevalence of attached stones and the appearance of the attachment site are consistent with a mechanism of calcium oxalate stone formation in which stones begin as plaque overgrowth.     

草酸钙结石患者肾乳头Randall斑的超微结构特点

目的 探讨草酸钙结石患者肾乳头Randall斑与草酸钙结石形成的关系. 方法经结石化学成分分析确诊为草酸钙肾结石患者12例.于经皮肾镜取石术中直视卜获取肾乳头Randall斑活检标本,分别行HE染色和锇酸固定,光镜和透射电镜下观察其组织病理和超微结构特点.结果 12例患者共检查肾乳头72处,肾乳头表面有Randall斑形成63处(87.5%),7例部分肾乳头表面有小结石附着.12例Randall斑活检标本光镜下肾乳头组织内见成团钙盐样沉积.2例电镜下肾乳头结缔组织中散在分布大小不均簇状草酸盐团聚体,典型结晶体呈针状,晶体轮廓周边电子密度高,晶体中央呈电子透亮区. 结论草酸钙结石患者肾乳头Randall斑主要是草酸盐结晶沉积,在Randall斑基础上草酸盐结晶进一步沉积可能促使草酸钙结石的形成.     

Changes in renal papillary density after hydration therapy in calcium stone formers

Background

Previous studies have shown that, compared with non-stone formers, stone formers have a higher papillary density measured with computer tomography (CT) scan. The effect of increased hydration on such papillary density in idiopathic calcium stone formers is not known.

Methods

Patients with recurrent calcium oxalate stones undergoing endourological procedures for renal stones at our Institution from June 2013 to June 2014 were considered eligible for enrolment. Enrolled patients underwent a baseline unenhanced CT scan before the urological procedure; after endoscopic removal of their stones, the patients were instructed to drink at least 2 L/day of a hypotonic, oligomineral water low in sodium and minerals (fixed residue at 180 °C?<?200 mg/L) for at least 12 months. Finally, the patients underwent a follow-up unenhanced CT scan during hydration regimen.

Results

Twenty-five patients were prospectively enrolled and underwent baseline and follow-up CT scans. At baseline, mean papillary density was 43.2?±?6.6 Hounsfield Units (HU) (43.2?±?6.7 for the left kidney and 42.8?±?7.1 HU for the right kidney). At follow-up and after at least 12 months of hydration regimen, mean papillary density was significantly reduced at 35.4?±?4.2 HU (35.8?±?5.0 for the left kidney and 35.1?±?4.2 HU for the right kidney); the mean difference between baseline and follow-up was ??7.8 HU (95% confidence interval???10.6 to ??5.1 HU, p?<?0.001).

Conclusions

Increased fluid intake in patients with recurrent calcium oxalate stones was associated with a significant reduction in renal papillary density.

Trial registration

NCT03343743, 15/11/2017 (Retrospectively registered).

     

Stone formation is proportional to papillary surface coverage by Randall's plaque

PURPOSE: Randall's plaques are common in calcium oxalate (CaOx) stone formers (SF). Plaque coverage correlates directly with urine calcium excretion and inversely with urine volume. We hypothesize that plaque coverage should increase proportionally with increasing stone number. We measured plaque areas in idiopathic CaOx stone formers and nonstone formers (NSF), and identified significant relationships with quantified stone histories. MATERIALS AND METHODS: A total of 13 SFs and 4 control NSFs underwent nephroscopic papillary mapping with representative still images and MPEG (Moving Pictures Experts Group) movies used to identify plaque and papillary borders. Stone histories were obtained through patient interviews, and from medical records and radiographs. The relationship of plaque coverage to clinical stone events was assessed by general multivariate linear modeling. Log transformation normalized the distribution of percent plaque coverage and stone number. RESULTS: Plaque surface area in SFs differed significantly from that in NSFs (p <0.0001). The duration of stone disease and the log transformed percent plaque coverage correlated significantly with the number of stones (0.677 and 0.620, p = 0.003 and 0.008, respectively). On multivariate analysis and correcting for the duration of stone disease total percent plaque coverage correlated significantly with the number of stones (R = 0.496, p = 0.05). Disease duration and plaque coverage did not correlate significantly (p = 0.257). CONCLUSIONS: Percent plaque coverage directly correlates with the number of stones formed even when corrected for the duration of stone disease. However, plaque coverage does not correlate with the duration of stone disease. These results support the hypothesis that the pathogenesis of CaOx stones begins with Randall's plaques.     

The role of Randall's plaques in the pathogenesis of calcium stones

PURPOSE: Knowledge of the inciting lesion in kidney stone formation has remained rudimentary until quite recently. Randall theorized that areas of apatite plaque on the renal papillae would be an ideal site for an overgrowth of calcium oxalate to develop into a calculus. We reviewed in vivo data that have further defined the role of Randall's plaques in stone disease. MATERIALS AND METHODS: We examined a set of literature that tested 2 hypotheses, that is 1) Randall's plaques are a specialized disease that begins as apatite in a unique region of the kidney due to local driving forces and anatomy, and 2) stones that arise from causes different from common calcium oxalate stones do not necessarily arise on plaque. RESULTS: Intraoperative papillary and cortical biopsy specimens obtained during percutaneous nephrolithotomy from the kidneys of 3 types of stone formers (idiopathic calcium stone formers, patients with stones due to bariatric procedures and brushite stone formers) showed unique histopathological findings. CONCLUSIONS: The metabolic and surgical pathological findings in 3 distinct groups of stone formers demonstrate that the histology of the renal papillae from a stone former is particular to the clinical setting.     

GERIATRIC UROLITHIASIS

Purpose

We define the differences between geriatric patients with urinary stone disease compared to a younger cohort.

Materials and Methods

A data base, including serum biochemical profiles, 24-hour urinalyses and standardized questionnaires, was retrospectively evaluated from more than 6,000 consecutive patients with urinary stone disease.

Results

Geriatric stone formers comprised 12% (721) of all stone patients. Two-thirds of these elderly patients had aberrant urinary values and 29% had isolated hypocitraturia compared to 17% in the younger group. Of geriatric stone forming patients 76% had recurrent urinary stones (mean 3.5 stone episodes), which was similar to the younger comparable group (77%, mean 3.3 stone episodes). The severity of urinary stone disease was similar between the 2 groups based on the need for urological intervention. Geriatric stone patients, in general, experienced the first stone episode later in life (after age 50 years) compared with younger patients. Elderly patients had an increased incidence of uric acid stones, but had a similar incidence of struvite calculi. Geriatric stone patients underwent parathyroid surgery more frequently (2.7 versus 0.7%). Geriatric stone forming patients rarely had renal failure.

Conclusions

The incidence, recurrence and severity of recurrent urinary stone disease were similar between geriatric and younger stone forming patients. Geriatric stone patients had an increased incidence of isolated hypocitraturia, uric acid calculi and previous parathyroidectomy. The geriatric stone population is not merely an extension of younger stone forming patients presenting at an older age. Rather, geriatric patients commonly experience the first symptomatic stone episode later in life.     

Systemic analysis of urinary stones from the Northern,Eastern, Central,Southern and Southwest China by a multi-center study

Background

To provide some basis for the prevention of urinary stones in general population, we did a systemic analysis of urinary stones from Northern, Eastern, Central, Southern and Southwest China by a multi-center study.

Methods

A total of 11,157 urinary stones from Northern, Eastern, Central, Southern and Southwest China were obtained and analyzed by Fourier transform infrared spectroscopy. Combined with scanning electron microscopy and X-ray energy spectrometer, urinary stones were classified into different types. Furthermore, the correlation between stone types and clinical characteristics, as well as their regional distribution were elucidated.

Results

Calcium oxalate stones were the most common type in each region, followed by calcium oxalate-calcium phosphate mixed stones, uric acid stones and calcium phosphate stones. The distribution of calcium oxalate stones were highest prevalence in Southwest China (67.9%, P?<?0.05), followed by Eastern and Northern China. Anhydrous uric acid stones, with a constituent ratio of 19.3% in Southern China, and 13.7% in Central China, were significantly higher than that in other regions (P?<?0.05). Elements analysis indicated varieties among stone types as well as distribution regions. Moreover, the clinical characteristics were highly correlated with stone types and anatomical locations but not their distribution regions.

Conclusions

The material and elements composition of urinary stones among different regions showed some varieties. Calcium oxalate stone has the highest constituent ratio in Southwest China, while anhydrous uric acid stone has the highest constituent ratio in Southern China. Moreover, the clinical characteristics were highly correlated with stone types and anatomical locations but not their distribution regions.

     

Comparison of renal function and metabolic abnormalities of cystine stone patients and calcium oxalate stone patients in China

Purpose

To compare renal function and metabolic abnormalities of cystine stone patients and calcium oxalate stone patients in China.

Methods

Between 2008 and 2011, thirty cystine stone patients were involved in our study, and an equal number of age- and gender pair-matched patients with calcium oxalate stones. Non-stone forming individuals were elected as controls. The evaluation included blood chemistry studies and 24-h urine collection in both groups of patients.

Results

The cystine stone patients had higher mean values of serum blood urea nitrogen, urate and creatinine levels than patients in other two groups. With respect to urine risk factors, cystine stone patients had higher urinary citrate and lower urinary oxalate and creatinine than calcium oxalate stone patients. When compared to non-stone forming individuals, cystine stone patients had higher urinary urate excretion and lower urinary creatinine excretion. Metabolic abnormalities could be demonstrated in 80 % of the cystine stone patients and in 100 % of the calcium oxalate stone patients. We also compared urine risk factors among cystine stone patients with different urine cystine excretion (<1 mmol/24 h, 1–2 mmol/24 h and >2 mmol/24 h). No significant difference was found in urine risk factors among three groups.

Conclusions

This study suggested that cystine stone patients were at greater risk for the loss of renal function than calcium oxalate stone patients, but the risk of the formation of calcium oxalate stones was lower. Our results also indicated that urinary cystine had little or no impact on the excretion of urine chemistries in cystine stone patients.     

Extracorporeal shock wave lithotripsy as first line treatment for urinary tract stones in children: outcome of 500 cases

Purpose

The continued evolution of stone treatment modalities, such as endourologic procedures, open surgery and shock wave lithotripsy, makes the assessment of continuous outcomes are essential. Pediatric urolithiasis are an important health problem allover the world, especially in Middle East region. We evaluate the safety, efficacy and factors affecting success rate and clearance of stones in children treated with shock wave lithotripsy.

Patient and methods

Between 2005 and 2010, a total of 500 children with stones in the upper urinary tract at different locations were treated by Extracorporeal shock wave lithotripsy (ESWL) in our department, Sohag University, Egypt. We have used the Siemn??s Lithostar Modularis machine, Germany. A total of 371 boys and 129 girls with the average age of 8.63?±?5?years, and a range from 9?months to 17?years were included in this study. Diagnosis of their urinary calculi was established either by the use of abdominal ultrasound, plain X-ray, intravenous urography, or CT scan. The stones were located in the kidney in 450 (90%) patients; 298 (66%) pelvic, 26 (5.7%) upper calices, 57 (12.6%) mid calices, and lower calices in 69 (15.3%) patients. The average of their stone sizes was 12.5?±?7.2?mm. The other 50 children their stone were located in the proximal ureteral stones in 35 patients (70%); middle third in 5 (10%) patients and in the distal ureter in 10 (20%) patients. The average ureteral stone size was 7.5?±?3.2?mm. All children were treated under general anesthesia with adequate lung and testes shielding using air foam. We treated the distal ureteral stones of young children in the supine position through greater sciatic foramen and lesser sciatic foramen as the path of shockwave instead of prone position, which is not a comfortable or natural position and could adversely affect cardiopulmonary function especially under general anesthesia. Localization was mainly done by ultrasound, and X-ray was only used to localize ureteral calculi. For follow-up, we have used abdominal ultrasound, plain X-ray, and CT scan if needed to confirm stone disintegration and clearance.

Results

The overall success rate for renal and ureteral calculi was 83.4 and 58.46%, respectively. The re-treatment rate was 4% in renal group and 28% for the ureteral group. No serious complications were recorded in our patients. Minor complications occurred in 15% of our patients; renal colic was reported in 10% of our treated patients, and repeated vomiting was reported in 5% that respond to antiemetics. In the renal group; children with history of pervious urologic surgical procedures had low success rate of stone clearance after ESWL. In the ureteral group stone burden, stone location, had a significant impact on stone clearance outcome.

Conclusion

This study showed that SWL in pediatric age group for both renal and ureteral stone is cost effective, safe with an acceptable re-treatment rate; however children with large stone burden or previous urologic surgery have low success rate.     

New Stone Formation: A Comparison of Extracorporeal Shock Wave Lithotripsy and Percutaneous Nephrolithotomy

Purpose

There is theoretical concern that stone recurrence rates may be higher following extracorporeal shock wave lithotripsy (ESWL*) compared to other techniques because of residual stone debris.*Dornier Medical Systems, Inc., Marietta, Georgia.

Materials and Methods

We documented all new stone formations in 298 consecutive patients who initially achieved a stone-free status following ESWL for renal calculi less than 2 cm. in largest dimension, and compared the findings to those of 62 patients treated with percutaneous nephrolithotomy without ultrasonic fragmentation. Stone-free status was assessed by a centrally reviewed plain abdominal film and renal tomograms at 3 months. A plain abdominal film was repeated at 12 and 24 months to detect recurrence.

Results

New stones formed in 22.2 percent of patients after ESWL and 4.2 percent after percutaneous nephrolithotomy at 1 year (p = 0.004), and in 34.8 percent versus 22.6 percent, respectively, at 2 years (p = 0.190). Furthermore, more new stones recurred in the lower and mid calices compared to baseline location in the ESWL group (chi-square less than 0.0001), which was not observed in the percutaneous nephrolithotomy group.

Conclusions

Our data support a trend toward higher stone recurrence rates in ESWL treated patients, which may be due to microscopic sand particles migrating to dependent calices and acting as a nidus for new stone formation.     

Epidemiology of nephrolithiasis in France

Nephrolithiasis is a frequent disease that affects about 10% of people in western countries. The prevalence of calcium oxalate stones has been constantly increasing during the past fifty years in France as well as in other industrialized countries. Stone composition varies depending to gender and age of patients and also underlines the role of other risk factors and associated pathologies such as body mass index and diabetes mellitus. The decrease in struvite frequency in female patients is the result of a significantly improved diagnostic and treatment of urinary tract infections by urea-splitting bacteria. In contrast, the increasing occurrence of weddellite calculi in stone forming women aged more than 50 years could be the consequence of post-menopausal therapy. A high prevalence of uric acid was found in overweight and obese stone formers and in diabetic ones as well. Another important finding was the increased occurrence with time of calcium oxalate stones formed from papillary Randall's plaques, especially in young patients. Nutritional risk factors for stone disease are well known: they include excessive consumption of animal proteins, sodium chloride and rapidly absorbed glucides, and insufficient dietary intake of fruits and potassium-rich vegetables, which provide an alkaline load. As a consequence, an excessive production of hydrogen ions may induce several urinary disorders including low urine pH, high urine calcium and uric acid excretion and low urine citrate excretion. Excess in calorie intake, high chocolate consumption inducing hyperoxaluria and low water intake are other factors, which favour excessive urine concentration of solutes. Restoring the dietary balance is the first advice to prevent stone recurrence. However, the striking increase of some types of calculi, such as calcium oxalate stones developed from Randall's plaque, should alert to peculiar lithogenetic risk factors and suggests that specific advices should be given to prevent stone formation.     

Updates in the Metabolic Management of Calcium Stones

Purpose of Review

Urinary risk factors, such as hypercalciuria, hypocitraturia, and hyperoxaluria, either in combination or alone, are associated with calcium stones. Dietary habits as well as underlying medical conditions can influence urinary risk factors. Evaluation of the conglomerate of patients’ stone risks provides evidence for individualized medical management, an effective and patient-supported approach to prevention.

Recent Findings

Many patients with stones desire prevention to avoid repeated surgical interventions. Yet, recent practice pattern assessments and health care utilization data show that many patients are rarely referred for metabolic evaluation or management. Innovations in metabolic management over the past decade have improved its effectiveness in reducing risk and preventing calcium stones. Although no new pharmacologic agents for calcium stone prevention have recently become available, there is relatively new thinking about some diet-based approaches.

Summary

This review will synthesize current evidence to support individualized metabolic management of calcium stones.

     

Urinary Calculi as a Late Complication of the Indiana Continent Urinary Diversion: Comparison with the Kock Pouch Procedure

Purpose

Although urinary calculi have been frequent late complications of the Kock continent urinary diversion, they have not been regarded as significant problems in patients with the Indiana pouch because of the lack of foreign material present. However, stones developed in a significant percentage of our patients with an Indiana pouch. We investigated the characteristics of stone formation in patients with the Indiana pouch and compared them to those with a Kock pouch.

Materials and Methods

Detailed clinical courses regarding stone formation were reviewed in 72 patients with a Kock pouch and 54 with an Indiana pouch who had a minimum followup of 12 months.

Results

Stones developed in 7 of 54 patients (12.9 percent) with an Indiana pouch compared to 31 of 72 (43.1 percent) with a Kock pouch. The incidence gradually increased with longer followup but it was lower in the Indiana than in the Kock pouch group (5-year stone-free rate 84 percent versus 66 percent, respectively). Although the stones consisted principally of a mixture of struvite, carbonate apatite and ammonium hydrogen urate, variable amounts of calcium oxalate were identified in 50 percent of the Indiana pouch calculi.

Conclusions

Not only urinary infections but also metabolic factors were considered to be involved in stone formation within the Indiana pouch. However, the substantially higher rate of stone formation in our Kock and Indiana pouch groups than has been reported in the United States suggested that no or infrequent pouch irrigations in our patients were important risk factors for urinary calculi.     

Urolithiasis in adult spina bifida patients: study in 260 patients and discussion of the literature

Purpose

To describe incidence and risk factors of urinary tract stones in adult spina bifida (SB) patients. Although spina bifida patients have an allegedly higher risk of urinary tract stones, only two small non-English case series are available and do not provide adequate epidemiological data and analyses on risk factors.

Methods

A total of 260 adult SB patients followed in our centre for 10 years were retrospectively analysed for stone disease. Both a univariate analysis (Fisher’s exact, two-sided Student’s t test) and a binary logistic regression analysis were performed to identify independent risk factors for stone disease.

Results

Of the 260 patients, 24 (9.2 %) were identified with a history of urolithiasis. Fourteen patients (5.4 %) had bladder stones in 26 episodes. Sixteen patients (6.2 %) had upper urinary tract stones: 14 kidney stones and two ureteral stones. Lifetime incidence of both bladder stones and upper tract stones was 2.25 per 1,000 patient-years. Recurrent urinary tract infections (OR 4.34, p = 0.013) and incorporation of bowel tissue into a continent reservoir (including enterocystoplasty) (OR 4.80, p = 0.012) were independent risk factors for bladder stone disease in a multivariate model. An indwelling catheter was an independent predictor for upper tract stones (OR 5.89, p = 0.02).

Conclusions

Urolithiasis, especially in the bladder, is a frequent finding in patients with SB. Bladder stones occur about 10 times more often in SB patients than in the population. In patients without risk factors, frequent ultrasound of the urinary tract is not necessary for the sole detection of stones.     

Dual energy can accurately differentiate uric acid-containing urinary calculi from calcium stones

Purpose

To retrospectively evaluate the accuracy of dual-energy CT (DECT) in the detection of the chemical composition of urinary calculi in correlation with infrared spectroscopic stone analysis.

Methods

We reviewed the CT scans of 255 patients who underwent DECT due to a clinical suspicion of urolithiasis. Out of this group, we included 64 patients with clinically symptomatic urolithiasis requiring stone removal. After surgical removal of the stone by ureterorenoscopy, chemical composition was analyzed with infrared spectroscopy. We correlated DECT stone characterization results with chemical stone composition based on dual-energy indices (DEI). A total of 213 renal and ureteral stones could be removed and chemically analyzed.

Results

A total of 213 calculi were evaluated. Thirty eight out of sixty four (59 %) patients had >1 stone. DECT was used to differentiate stones by using DEI. Stones harboring calcium (CA) were color-coded in blue, while stones containing uric acid (UA) were colored red. Median DEI in UA-containing stones were 0.001. Non-UA-containing stones had a DEI between 0.073 for pure CA stones and 0.077 containing CA and other substances (p = 0.001; p = 0.03, respectively). Sensitivity of DECT was 98.4 % for differentiation of UA from non-UA-containing calculi. Specificity was 98.1 %. Mean effective radiation dose of DECT was 4.18 mSv (0.44–14.27 mSv), thus comparable to conventional CT scans of the abdomen. Conventional measurement of Hounsfield units did not correlate with stone composition.

Conclusion

DECT with image post-processing reliably discriminates UA-containing calculi from all other stones, but the study offered limitations. Discrimination within the non-UA stones cannot be reliably achieved but is clinically insignificant.

     

RENAL STONE RISK ASSESSMENT DURING SPACE SHUTTLE FLIGHTS

Purpose

The metabolic and environmental factors influencing renal stone formation before, during, and after Space Shuttle flights were assessed. We established the contributing roles of dietary factors in relationship to the urinary risk factors associated with renal stone formation.

Materials and Methods

24-hr. urine samples were collected prior to, during space flight, and following landing. Urinary and dietary factors associated with renal stone formation were analyzed and the relative urinary supersaturation of calcium oxalate, calcium phosphate (brushite), sodium urate, struvite and uric acid were calculated.

Results

Urinary composition changed during flight to favor the crystallization of calcium-forming salts. Factors that contributed to increased potential for stone formation during space flight were significant reductions in urinary pH and increases in urinary calcium. Urinary output and citrate, a potent inhibitor of calcium-containing stones, were slightly reduced during space flight. Dietary intakes were significantly reduced for a number of variables, including fluid, energy, protein, potassium, phosphorus and magnesium.

Conclusions

This is the first in-flight characterization of the renal stone forming potential in astronauts. With the examination of urinary components and nutritional factors, it was possible to determine the factors that contributed to increased risk or protected from risk. In spite of the protective components, the negative contributions to renal stone risk predominated and resulted in a urinary environment that favored the supersaturation of stone-forming salts. Dietary and pharmacologic therapies need to be assessed to minimize the potential for renal stone formation in astronauts during/after space flight.     

Size of common bile duct stones on MRCP predicts likelihood of positive findings at ERCP

Objective

To ascertain if direct measurement of the size of common bile duct stones (CBD) on magnetic resonance cholangio-pancreatography (MRCP) can be used to predict the likelihood of a positive endoscopic retrograde cholangio-pancreatography (ERCP) result. Should we be carrying out ERCPs on all patients with CBD stones?

ACCURATE DETERMINATION OF CHEMICAL COMPOSITION OF URINARY CALCULI BY SPIRAL COMPUTERIZED TOMOGRAPHY

Purpose

Choice of efficacious clinical management of symptomatic renal calculi can be facilitated by ascertaining the precise chemical composition of the calculus. Spiral computerized tomography (CT) is becoming a frequently used radiographic examination to establish the diagnosis and severity of calculus disease. Our objective for this study was to determine the precision of spiral CT in identifying the chemical composition of 6 different types of urinary calculi with region of interest measurements using spiral CT.

Materials and Methods

A total of 102 chemically pure stones were separated into 6 groups. The stones along with phantoms containing butter (fat) and jello (water) were mounted vertically in the scanner gantry. Then 1 mm. thickness scanning was performed with a high speed scanner at the 2 energy levels of 80 and 120 kV. The determination of the chemical composition was performed using the absolute CT value measured at 120 kV. and the dual kilovolt CT values measured at 80 and 120 kV. Hounsfield unit at 80 kV. - Hounsfield unit at 120 kV.).

Results

The absolute CT value measured at 120 kV. was able to identify precisely the chemical composition of uric acid, struvite and calcium oxalate stones. It was imprecise in differentiating calcium oxalate from brushite stone and struvite from cystine stone. However, dual kilovolt CT value was able to differentiate these latter stones with statistical significance (p <0.03). Uric acid stones were easily differentiated from all other stones using the absolute CT value.

Conclusions

This study demonstrates that the chemical composition of urinary calculi can be accurately determined by CT scanning in an in vitro setting.