CT, US and MRI of xanthine urinary stones: in-vitro and in-vivo analyses

BACKGROUND

Xanthine urinary stones are a rare entity that may occur in patients with Lesch-Nyhan syndrome receiving allopurinol. There is little literature describing imaging characteristics of these stones, and the most appropriate approach to imaging these stones is therefore unclear. We performed in-vitro and in-vivo analyses of xanthine stones using computed tomography (CT) at different energy levels, ultrasound (US), and magnetic resonance imaging (MRI).

METHODS

Five pure xanthine stones from a child with Lesch-Nyhan were imaged in-vitro and in-vivo. CT of the stones was performed at 80 kVp, 100 kVp, 120 kVp and 140 kVp and CT numbers of the stones were recorded in Hounsfield units (HU). US of the stones was performed and echogenicity, acoustic shadowing and twinkle artifact were assessed. MRI of the stones was performed and included T2-weighted, ultrashort echo-time-weighted and T2/T1-weighted 3D bFFE sequences and signal was assessed.

RESULTS

In-vitro analysis on CT demonstrated that xanthine stones were radiodense and the average attenuation coefficient did not differ with varying kVp, measuring 331.0 ± 51.7 HU at 80 kVp, 321.4 ± 63.4 HU at 100 kVp, 329.7 ± 54.2 HU at 120 kVp and 328.4 ± 61.1 HU at 140 kVp. In-vivo analysis on CT resulted in an average attenuation of 354 ± 35 HU. On US, xanthine stones where echogenic with acoustic shadowing and twinkle artifact. On MRI, stones lacked signal on all tested sequences.

CONCLUSION

Xanthine stone analyses, both in-vitro and in-vivo, demonstrate imaging characteristics typical of most urinary stones: dense on CT, echogenic on US, and lacking signal on MRI. Therefore, the approach to imaging xanthine stones should be comparable to that of other urinary stones.

Exploring the Association of Asthma with Urinary Stone Disease: Results from the National Health and Nutrition Examination Survey 2007-2014

BACKGROUND

The prevalence of urinary stone disease (USD) and asthma is rising and has recently been associated in a pediatric population.

OBJECTIVE

To investigate the association between asthma and USD in a nationally representative adult population.

DESIGN, SETTING, AND PARTICIPANTS

We analyzed the National Health and Nutrition Examination Survey 2007-2014, a US population-based cross-sectional study. A history of asthma and USD was obtained by self-report to questionnaires. USD severity was represented by graded stratification into non-stone formers, single stone formers, and recurrent stone formers (>2 stones).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Odds ratios (ORs) for asthma were calculated for respondents with USD and separately for the graded USD groups. Survey-weighted logistic regression models included adjustments for demographics (model A), medical information (model B), and for relevant medications (model C).

RESULTS AND LIMITATIONS

A total of 20 906 participants aged ≥20 yr were included in the analysis. Of these, 9.2% reported of having a history of kidney stones. Logistic regression analysis adjusted for demographics, medical conditions, and medications showed that stone formers had significantly increased odds of asthma (odds ratio=1.23; 95% confidence interval: 1.03-1.47; p=0.023). Separate logistic regression analysis demonstrated a graded association between single and recurrent stone formers and the odds of having asthma (p=0.01), which remained significant in the 20-50-yr-old population and the diabetic population, especially for recurrent stone formers. Causal relationships were limited by cross-sectional nature of the study.

CONCLUSIONS

Increasing severity of USD is associated with an increase in odds for asthma among American adults, providing impetus for future studies into the mechanisms explaining this phenomenon.

PATIENT SUMMARY

In this report, we looked at self-reported histories of asthma and urinary stone disease (USD) using information from a large US population. We found that asthma was associated with USD; however, further studies are needed to elucidate this relationship.

Does total testicular volume predict testicular volume difference in adolescent males with varicocele?

Introduction:

We evaluated the relationship between total testicular volume (TTV) and testicular volume differential (TVD) in adolescent males with varicocele. Both low TTV and high TVD have been independently associated with higher incidences of infertility later in life, but a predictive relationship between TTV and TVD directly has yet to be described.

Materials and Methods:

We retrospectively analyzed a database of Tanner 5 boys ages 16-21 who presented with varicocele at a single institution between 2009 and 2017. All patients had a scrotal sonogram prior to surgical intervention. TTV and TVD were calculated for each individual and four non-exclusive groupings of patients were created for statistical analysis. We chose 30 cc as a cut off value for low TTV based on prior studies.

Results:

209 patients met our inclusion criteria. Mean age was 18.3 years (16–21, SD 1.7) with a mean total testicular volume of 36 cc (13.5-78.2, SD 11.1). Cut off points of TVD of 20% and TTV of 30 cc were used to separate patients. There were 65 boys (31%) with TTV < 30 cc and 58 boys (28%) with TVD ≥ 20%. Among males with TTV < 30 cc, 23 (35%) had a TVD ≥ 20%. Among males with TTV ≥ 30 cc, 35 (24%) had a TVD ≥ 20%. The relationship between TVD and TTV was found to be non-significant (p > 0.05).

Discussion:

Adolescent varicoceles continue to pose a challenge to pediatric urologists. The dilemma of over-aggressive treatment has proven difficult to balance with the risk of infertility. We hoped that elucidating the relationship between TTV and TVD could be useful in identifying patients who are at greater risk for infertility while decreasing the need for more intrusive testing, such as semen analysis, in an adolescent population. We looked at the direct relationship between low TTV and high TVD. In our population, there was a non-significant relationship between TTV < 30 cc and TVD ≥ 20% (p > 0.05) indicating that in adolescents with varicocele, TTV and TVD are independent variables. Our study limitations include the inherent user dependent bias of ultrasound measurements and data collection at a single institution with high ethnic diversity, possibly not comparable to all patient populations.

Conclusions:

Low TTV (< 30 cc) itself is not predictive of high TVD (≥ 20%) in adolescent boys with varicocele, despite their reported independent associations with impaired fertility in other studies.

Modulation of the hypoxic response following partial bladder outlet obstruction

PURPOSE

Tissue level hypoxia has been noted in animal models of partial bladder outlet obstruction. The key mechanisms linking hypoxia and obstruction induced bladder dysfunction remain unknown. 2-Methoxyestradiol is a natural derivative of 17β-estradiol and is currently used as an oncologic agent for its ability to regulate the hypoxia pathway. We investigated the ability of 2-methoxyestradiol to modulate the hypoxia response in a mouse model of bladder obstruction.

MATERIALS AND METHODS

A group of 5 to 6-week-old female C57BL/6 mice underwent oophorectomy and partial bladder outlet obstruction. Obstructed animals received a subcutaneous pellet of cholesterol placebo (7) or 2-methoxyestradiol plus cholesterol (7). Age matched controls underwent oophorectomy only (8). After 4 weeks the bladders of mice with partial bladder outlet obstruction and of unobstructed animals were harvested. Bladder sections (5 μm) were immunostained for Hypoxyprobe™-1, glucose transporter 1 and hypoxia inducible factor-1α. Real-time polymerase chain reaction was performed for hypoxia inducible factor-1α and lysyl oxidase. Statistical analysis was performed using 1-way ANOVA and the Wilcoxon rank sum test.

RESULTS

Immunostaining for glucose transporter 1 and Hypoxyprobe-1 revealed the presence of tissue hypoxia after partial bladder outlet obstruction. Immunostaining and real-time polymerase chain reaction demonstrated the up-regulation of hypoxia inducible factor-1α in mice after partial bladder outlet obstruction compared to controls (p = 0.0394). Although not statistically significant, a trend toward lower gene expression of hypoxia inducible factor-1α was seen in mice receiving 2-methoxyestradiol compared to placebo (p = 0.0625). Compared to placebo, 2-methoxyestradiol treatment increased lysyl oxidase expression (p = 0.007).

CONCLUSIONS

Murine partial bladder outlet obstruction resulted in hypoxia and up-regulation of the hypoxia inducible factor-1 pathway. Subcutaneous 2-methoxyestradiol administration attenuated this response and may be a viable tool to study the role of hypoxia after partial bladder outlet obstruction.

Observation of patients with vesicoureteral reflux off antibiotic prophylaxis: physician bias on patient selection and risk factors for recurrent febrile urinary tract infection

PURPOSE

Observation off continuous antibiotic prophylaxis is an option for vesicoureteral reflux. We evaluated the characteristics of patients observed off continuous antibiotic prophylaxis and risk factors for febrile urinary tract infection.

MATERIALS AND METHODS

We identified children 1 to 18 years old with primary vesicoureteral reflux between January 1, 2010 and December 31, 2010. We excluded patients with prior surgical correction from analysis. We recorded age, gender, race/ethnicity, primary language, insurance carrier, age at vesicoureteral reflux diagnosis, initial presentation and vesicoureteral reflux severity. We quantified bladder and bowel dysfunction with a validated questionnaire if toilet trained. We compared patients off vs on continuous antibiotic prophylaxis with the chi-square test for categorical variables and the Mann-Whitney U test for continuous variables. We used a univariate Cox proportional hazards model to assess predictors of febrile urinary tract infection during observation off continuous antibiotic prophylaxis.

RESULTS

Of 529 eligible patients 224 were observed off continuous antibiotic prophylaxis. Patients off continuous antibiotic prophylaxis tended to be older (p <0.001), to be older at diagnosis (p <0.001), to have an initial presentation other than febrile urinary tract infection (p = 0.05), to have nondilating vesicoureteral reflux on most recent cystogram (p <0.001) and to have lower bladder/bowel dysfunction scores if toilet trained (p <0.001). Of the patients off continuous antibiotic prophylaxis a febrile urinary tract infection developed in 19 (8.5%). Risk factors associated with febrile urinary tract infection included initial presentation of multiple febrile urinary tract infections (p = 0.03), older age at diagnosis (p = 0.03) and older age starting observation off continuous antibiotic prophylaxis (p = 0.0003).

CONCLUSIONS

Criteria to select patients with vesicoureteral reflux for observation off continuous antibiotic prophylaxis remain poorly defined in the literature. Observation will fail in a subset of patients with vesicoureteral reflux. Physician biases regarding patient selection for observation off continuous antibiotic prophylaxis should be considered when interpreting studies that evaluate treatment strategies.

Urodynamic testing in children: indications, technique, interpretation and significance

PURPOSE

Urodynamic studies in children have been performed with increasing frequency as the techniques, reproducibility and reliability of the testing have been refined in the last quarter century. Children of all ages and with a variety of comorbidities are now often referred for urodynamic testing to evaluate and understand the causes of incontinence and/or persistence of lower urinary tract symptoms, as well as to appropriately define and evaluate treatment regimens.

MATERIALS AND METHODS

We performed a MEDLINE® search for relevant articles on urinary tract dysfunction, neurogenic bladder and urodynamic studies in the pediatric population. We also included 3 major textbooks that addressed the subject matter.

RESULTS

We review the current indications for urodynamic studies in children with nonneurogenic and neurogenic bladder dysfunction. We summarize the components and techniques of the current practice of urodynamic studies in the pediatric population, and explain how to identify abnormal results.

CONCLUSIONS

The use of urodynamic studies in pediatrics has become almost mandatory for the effective management of severe or therapy resistant urinary tract abnormalities. This review may be used as a guideline for the appropriate application of urodynamics in this patient population.

Bone marrow-derived mesenchymal stem cells: current and future applications in the urinary bladder

Mesenchymal stem cells can be isolated from almost any adult tissue. In this paper we focus on bone marrow-derived mesenchymal stem cells which have captured the interest of researchers since their introduction because of the promising potential of tissue regeneration and repair. They are known for their ability to self-renew and differentiate into diverse lineages while maintaining low immunogenicity. The exact mechanisms behind how these cells work still remain unclear, and there is a continuing shift in the paradigms that support them. There has been extensive research in multiple organ systems; however, the genitorurinary system has been vastly underrepresented. This article discusses the background behind bone marrow-derived mesenchymal stem cells and they are currently being applied to the urinary bladder in the realm of tissue engineering. We also postulate on their future applications based on the current literature in other organ systems.