Changing composition of renal calculi in patients with musculoskeletal anomalies

A systematic review of postoperative outcomes of kidney stone surgery and meta-analysis of outcomes of percutaneous nephrolithotomy in individuals with spinal cord injury

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

To evaluate outcomes of surgical treatment for nephrolithiasis in individuals with spinal cord injury (SCI).

METHODS

We systematically reviewed the Ovid MEDLINE, Embase, CENTRAL, and Web of Science databases for studies examining outcomes of kidney stone procedures in individuals with SCI. Our primary outcomes were stone-free rate (SFR) and complications as categorized by Clavien-Dindo classification. A meta-analysis of comparative studies was performed to assess differences in SFR and complication rate between individuals with and without SCI following PCNL.

RESULTS

A total of 27 retrospective and observational articles were included. Interventions for kidney stones included PCNL, shockwave lithotripsy (SWL), and ureteroscopy. Pooled SFR in individuals with SCI was 54%, for SWL, 74% for PCNL, and 36% for ureteroscopy. Meta-analyses found that there was higher rate of grades I (OR 9.54; 95% CI, 3.06 to 29.79), II (OR 3.38; 95% CI, 1.85 to 6.18), and III-V (OR 2.38; 95% CI, 1.35 to 4.19) complications in individuals with SCI compared to non-SCI individuals following PCNL. The rate of infectious complications was also higher in individuals with SCI (OR 6.15; 95% CI, 1.86 to 20.39). However, there was no difference in SFR (OR 0.64; 95% CI, 0.15 to 2.64) between groups.

CONCLUSIONS

Individuals with SCI are at higher risk of minor, major, and infectious complications following PCNL compared to non-SCI individuals. There was no significant difference between groups in SFR following PCNL, suggesting that PCNL is an effective surgery for kidney stones in individuals with SCI.

Trends in renal calculus composition and 24-hour urine analyses in patients with neurologically derived musculoskeletal deficiencies

Purpose:

To better characterize metabolic stone risk in patients with neurologically derived musculoskeletal deficiencies (NDMD) by determining how patient characteristics relate to renal calculus composition and 24-hour urine parameters.

Materials and Methods:

We performed a retrospective cohort study of adult patients with neurologically derived musculoskeletal deficiencies presenting to our multidisciplinary Kidney Stone Clinic. Patients with a diagnosis of NDMD, at least one 24-hour urine collection, and one chemical stone analysis were included in the analysis. Calculi were classified as primarily metabolic or elevated pH. We assessed in clinical factors, demographics, and urine metabolites for differences between patients who formed primarily metabolic or elevated pH stones.

Results:

Over a 16-year period, 100 patients with NDMD and nephrolithiasis were identified and 41 met inclusion criteria. Thirty percent (12 / 41) of patients had purely metabolic calculi. Patients with metabolic calculi were significantly more likely to be obese (median body mass index 30.3kg / m² versus 25.9kg / m²), void spontaneously (75% vs. 6.9%), and have low urine volumes (100% vs. 69%). Patients who formed elevated pH stones were more likely to have positive preoperative urine cultures with urease splitting organisms (58.6% vs. 16.7%) and be hyperoxaluric and hypocitraturic on 24-hour urine analysis (37mg / day and 265mg / day versus 29mg / day and 523mg / day).

Conclusions:

Among patients with NDMD, metabolic factors may play a more significant role in renal calculus formation than previously believed. There is still a high incidence of carbonate apatite calculi, which could be attributed to bacteriuria. However, obesity, low urine volumes, hypocitraturia, and hyperoxaluria suggest an underrecognized metabolic contribution to stone formation in this population.

Outcomes of Ureteroscopic Stone Treatment in Patients With Spinal Cord Injury

OBJECTIVE

To evaluate the association of clinical factors on outcomes in patients with spinal cord injury (SCI) undergoing ureteroscopy. Immobility, recurrent urinary tract infection, and lower urinary tract dysfunction contribute to renal stone formation in patients with SCI. Ureteroscopy is a commonly utilized treatment modality; however, surgical complication rates and outcomes have been poorly defined. Evidence guiding safe and effective treatment of stones in this cohort remains scarce.

METHODS

Records were retrospectively reviewed for patients with SCI who underwent ureteroscopy for kidney stones from 1996 to 2014 at a single institution. Multivariate relationships were evaluated using a general estimating equation model.

RESULTS

Forty-six patients with SCI underwent a total of 95 ureteroscopic procedures. After treatment, stone-free rate was 17% and 20% with <2-mm fragments. The complication rate was 21%. On multivariate analysis, SCI in cervical (C) levels was associated with higher risk of complications (C3: odds ratio [OR] 3.83, 95% confidence interval [CI] 2.17-6.98; C6: OR 3.83, 95% CI 1.08-13.53). American Spinal Injury Association Scale A classification was associated with a lower probability of stone-free status (OR 0.16, 95% CI 0.03-0.82). Patients averaged 2.2 procedures yet more procedures were associated with lower stone-free status (OR 0.83, 95% CI 0.03-0.32). Chronic obstructive pulmonary disease and bladder management modality were not associated with stone-free status or complications.

CONCLUSION

In patients with SCI, higher injury level and complete SCI were associated with worse stone clearance and more complications. Stone-free rate was 17%. Overall, flexible ureteroscopy is a relatively safe procedure in this population. Alternative strategies should be considered after failed ureteroscopy.

Is there a relationship between solubility and resorbability of different calcium phosphate phases in vitro?

BACKGROUND

Does chemistry govern biology or it is the other way around - that is a broad connotation of the question that this study attempted to answer.

METHOD

Comparison was made between the solubility and osteoclastic resorbability of four fundamentally different monophasic calcium phosphate (CP) powders with monodisperse particle size distributions: alkaline hydroxyapatite (HAP), acidic monetite (DCP), β-calcium pyrophosphate (CPP), and amorphous CP (ACP). Results With the exception of CPP, the difference in solubility between different CP phases became neither mitigated nor reversed, but augmented in the resorptive osteoclastic milieu. Thus, DCP, a phase with the highest solubility, was also resorbed more intensely than any other CP phase, whereas HAP, a phase with the lowest solubility, was resorbed least. CPP becomes retained inside the cells for the longest period of time, indicating hindered digestion of only this particular type of CP. Osteoclastogenesis was mildly hindered in the presence of HAP, ACP and DCP, but not in the presence of CPP. The most viable CP powder with respect to the mitochondrial succinic dehydrogenase activity was the one present in natural biological bone tissues: HAP.

CONCLUSION

Chemistry in this case does have a direct effect on biology. Biology neither overrides nor reverses the chemical propensities of inorganics with which it interacts, but rather augments and takes a direct advantage of them.

SIGNIFICANCE

These findings set the fundamental basis for designing the chemical makeup of CP and other biosoluble components of tissue engineering constructs for their most optimal resorption and tissue regeneration response.

Bladder stones after bladder augmentation are not what they seem

INTRODUCTION

Bladder and renal calculi after bladder augmentation are thought to be primarily infectious, yet few studies have reported stone composition.

OBJECTIVE

The primary aim was to assess bladder stone composition after augmentation, and renal stone composition in those with subsequent nephrolithiasis. The exploratory secondary aim was to screen for possible risk factors for developing infectious stones.

STUDY DESIGN

Patients treated for bladder stones after bladder augmentation at the present institution between 1981 and 2012 were retrospectively reviewed. Data were collected on demographics, surgeries and stone composition. Patients without stone analysis were excluded. Stones containing struvite, carbonate apatite or ammonium acid ureate were classified as infectious. The following variables were analyzed for a possible association with infectious bladder stone composition: gender, history of cloacal exstrophy, ambulatory status, nephrolithiasis, recurrent urea-splitting urinary tract infections, first vs recurrent stones, timing of presentation with a calculus, history of bladder neck procedures, catheterizable channel and vesicoureteral reflux. Fisher's exact test was used for analysis.

RESULTS

Of the 107 patients with bladder stones after bladder augmentation, 85 met inclusion criteria. Median age at augmentation was 8.0 years (follow-up 10.8 years). Forty-four patients (51.8%) recurred (14 multiple recurrences, 143 bladder stones). Renal calculi developed in 19 (22.4%) patients with a bladder stone, and 10 (52.6%) recurred (30 renal stones). Overall, 30.8% of bladder stones were non-infectious (Table). Among patients recurring after an infectious bladder stone, 30.4% recurred with a non-infectious one. Among patients recurring after a non-infectious stone, 84.6% recurred with a non-infectious one (P = 0.005). Compared with bladder stones, renal stones were more likely to be non-infectious (60.0%, P = 0.003). Of patients with recurrent renal calculi after an infectious stone, 40.0% recurred with a non-infectious one. No clinical variables were significantly associated with infectious stone composition on univariate (≥0.28) or bivariate analysis (≥0.36).

DISCUSSION

This study had several limitations: it was not possible to accurately assess adherence with bladder irrigations, and routine metabolic evaluations were not performed. The findings may not apply to patients in all clinical settings. While stone analysis was available for 3/4 of the stones, similar rates of incomplete stone analyses have been reported in other series.

CONCLUSIONS

In patients with bladder augmentation, 1/3 of bladder stones and >1/2 of renal stones were non-infectious. Furthermore, an infectious stone does not imply an infectious recurrent stone and no known clinical variables appear to be associated with stone composition, suggesting that there is a possible metabolic component in stone formation after bladder augmentation.

Preoperative Bladder Urine Culture as a Predictor of Intraoperative Stone Culture Results: Clinical Implications and Relationship to Stone Composition

PURPOSE

We examine the relationship between urine and stone cultures in a large cohort of patients undergoing percutaneous stone removal and compare the findings in infectious vs metabolic calculi.

MATERIALS AND METHODS

A total of 776 patients treated with percutaneous nephrolithotomy who had preoperative urine cultures and intraoperative stone cultures were included in the study. Statistical analysis used chi-square or logistic fit analysis as appropriate.

RESULTS

Preoperative urine culture was positive in 352 patients (45.4%) and stone cultures were positive in 300 patients (38.7%). There were 75 patients (9.7%) with negative preoperative cultures who had positive stone cultures, and in patients with both cultures positive the organisms differed in 103 (13.3%). Gram-positive organisms predominated in preoperative urine and stone cultures.

CONCLUSIONS

Preoperative urine cultures in patients undergoing percutaneous nephrolithotomy are unreliable as there is a discordance with intraoperative stone cultures in almost a quarter of cases. There has been a notable shift toward gram-positive organisms in this cohort of patients.

Innovative delivery of siRNA to solid tumors by super carbonate apatite

RNA interference (RNAi) technology is currently being tested in clinical trials for a limited number of diseases. However, systemic delivery of small interfering RNA (siRNA) to solid tumors has not yet been achieved in clinics. Here, we introduce an in vivo pH-sensitive delivery system for siRNA using super carbonate apatite (sCA) nanoparticles, which is the smallest class of nanocarrier. These carriers consist simply of inorganic ions and accumulate specifically in tumors, yet they cause no serious adverse events in mice and monkeys. Intravenously administered sCA-siRNA abundantly accumulated in the cytoplasm of tumor cells at 4 h, indicating quick achievement of endosomal escape. sCA-survivin-siRNA induced apoptosis in HT29 tumors and significantly inhibited in vivo tumor growth of HCT116, to a greater extent than two other in vivo delivery reagents. With innovative in vivo delivery efficiency, sCA could be a useful nanoparticle for the therapy of solid tumors.

The change in upper tract urolithiasis composition, surgical treatments and outcomes of para and quadriplegic patients over time

Stone disease in patients with spinal cord injury is a source of morbidity and mortality. Previous studies have indicated a decrease in infection-based urolithiasis in recent decades. We aimed to identify changes in stone composition and surgical outcomes in patients with para and quadriplegia over time. A retrospective review of para and quadriplegic patients from 1986 to 2011 who underwent surgical intervention for urolithiasis was performed, identifying 95 patients. The Mantel-Haenszel Chi square test was used to compare change in stone composition over time. The mean patient age was 44.0 years (range 18-88) and treatment included percutaneous nephrolithotomy (PCNL) 40 (42.1 %), ureteroscopy 28 (29.5 %), shock wave lithotripsy (SWL) 26 (27.4 %), and nephrectomy 1 (1 %). Overall stone-free status was found in 47.4 % with 19.0 % requiring a repeat procedure. The median hospital stay for patients undergoing SWL was 2.5 days, ureteroscopy 5 days, and PCNL 6 days. Infection-based stone composition was identified in 23 patients (36.5 %). We evaluated the linear change in percent of each stone component over time and identified increasing components of calcium oxalate dihydrate (p = 0.002) and calcium carbonate (p = 0.009). However, over a period of 25 years, the incidence of infection-based stone did not change (p = 0.57). Para and quadriplegic patients with urolithiasis can be difficult to treat surgically with prolonged hospitalizations, low stone-free status, and often require additional procedures. Despite improvements in antibiotic agents and management of neurogenic bladders, infection-based calculi continue to be a significant source of morbidity to this patient population.

Are stone analysis results different with repeated sampling?

INTRODUCTION

We assessed differences in results of stone analyses on subsequent sampling.

METHODS

A retrospective review of patients with stone analyses at a tertiary stone centre between March 2006 and July 2012 was performed. All stones were analyzed at a centralized laboratory using infrared spectroscopy. Patients were grouped according to the first predominant stone type on record, as defined by the predominant stone component of at least 60%. Stone groups included calcium oxalate (CaOx), calcium phosphate (CaP), uric acid (UA), cystine, struvite, mixed CaOx-CaP and mixed CaOx-UA. All patients had a full metabolic stone workup.

RESULTS

Of the 303 patients with stone analyses, 118 (38.9%) patients had multiple stone analyses. The mean age was 53.4 ± 15.1 years, and 87 (73.7%) were males. Of the 118, the initial stone analysis showed 43 CaOx, 38 CaP, 21 UA, 4 CaOx-CaP, 2 CaOx-UA, 6 cystine, and 4 struvite. There was a different stone composition in 25 (21.2%) patients with a median time delay of 64.5 days. Different compositions were found in 7 CaOx (to 3 CaP, 2 CaOx-CaP, and 2 UA), 5 CaP (to 3 CaOx and 2 CaOx-CaP), 3 UA (to 3 CaOx), 4 CaOx-CaP (to 2CaOx, 1 UA and 1 CaP), 2 CaOx-UA (to 2 CaOx) and 4 struvite (to 3 CaP and 1 UA).

CONCLUSIONS

Stone composition was different in 21.2% of patients on subsequent analyses.

Possible way to reduce fracture rates in patients with traumatic spinal cord injury?

Lower extremity fractures in men with spinal cord injury (SCI) are a major problem. The use of thiazide diuretics, a simple and safe intervention, may be effective in reducing the risk of fracture in patients with traumatic SCI. Furthermore, thiazide diuretics have an added benefit of reducing kidney stone formation.

Development of upper tract stones in patients with congenital neurogenic bladder

OBJECTIVE

Patients with neurogenic bladder are at increased risk of developing upper tract stones. We hypothesized that patients with lower urinary tract stone disease are at greater risk of developing upper tract stones.

METHODS

We performed a 10-year retrospective case-control study of patients with neurogenic bladder to determine the association between bladder and upper tract stones. Independent risk factors for upper tract stones were assessed. Cases and controls were matched 1:1. Univariable analysis was performed by Fisher's exact test and the Mann-Whitney U test. Multivariable logistic regression was performed.

RESULTS

52 cases and controls were identified. Cases were significantly more likely to be non-ambulatory, have bowel-urinary tract interposition, thoracic level dysraphism, and history of bladder stones. On multivariable analysis, independent predictors of stone formation were male sex (OR 2.82; p = 0.02), dysraphism involving the thoracic spine (OR 3.37; p = 0.014) bowel-urinary tract interposition (OR 2.611; p = 0.038), and a history of bladder stones (OR 3.57; p = 0.015).

CONCLUSION

Patients with neurogenic bladder are at increased risk for upper tract stones. The presence of bladder stones may herald the development of upper tract stones. The predictors of stone disease identified should guide prospective studies to better understand the natural history of upper tract stone development in this population.

Therapy-resistant nephrolithiasis following renal artery coil embolization

Background

Transcatheter renal artery embolization is an effective and minimally invasive treatment option for acute renal bleeding. Early post-interventional complications include groin hematoma, incomplete embolization, coil misplacement and coil migration. Late complications are rare and mostly related to coil migration.

Case presentation

A 22-year-old woman with a history of recurrent stone disease and a lumbal meningomyelocele underwent bilateral open pyelolithotomy for bilateral staghorn calculi. Post-operatively, acute hemorrhage of the left kidney occurred and selective arterial coil embolization of a lower pole interlobular renal artery was performed twice.

Four years after this intervention the patient presented with a new 15.4 mm stone in the lower calyx of the left kidney. After two extracorporeal shock wave lithotripsy treatments disintegration of the stone was not detectable. Therefore, flexible ureterorenoscopy was performed and revealed that the stone was adherent to a partially intraluminal metal coil in the lower renal calyx. The intracalyceal part of the coil and the adherent stone were successfully removed using the holmium laser.

Conclusion

Therapy-resistant nephrolithiasis was caused by a migrated metal coil, which was placed four years earlier for the treatment of acute post-operative renal bleeding. Renal coils in close vicinity to the renal pelvis can migrate into the collecting system and trigger renal stone formation. Extracorporeal shock wave lithotripsy seems to be inefficient for these composite stones. Identification of these rare stones is possible during retrograde intrarenal surgery. It also enables immediate stone disintegration and removal of the stone fragments and the intraluminal coil material.

Renal stone disease in spinal-cord-injured patients

Renal stone disease is common among patients with spinal cord injury (SCI). They frequently have recurrent stones, staghorn calculi, and bilateral stone disease. The potential risk factors for stones in the SCI population are lesion level, bladder management strategy, specific metabolic changes, and frequent urinary tract infections. There has been a reduction in struvite stones among these patients, likely as a result of advances in their urologic care. The clinical presentation of stone disease in patients with SCI may involve frequent urinary infections or urosepsis, and at the time of presentation patients may need emergency renal drainage. The proportion of patients who have their stones treated with different modalities is largely unknown. Shockwave lithotripsy (SWL) is commonly used to manage stones in patients with SCI, and there have been reports of stone-free rates of 50% to 70%. The literature suggests that the morbidity associated with percutaneous nephrolithotomy in these patients is considerable. Ureteroscopy is a common modality used in the general population to treat patients with upper tract stone disease. Traditional limitations of this procedure in patients with SCI have likely been overcome with new flexible scopes; however, the medical literature has not specifically reported on its use among patients with SCI.