Assessment of Hounsfield Units and Factors Associated with Fragmentation of Renal Stones by Extracorporeal Shock Wave Lithotripsy: A Computerized Tomography Study

The success rate of extracorporeal shock wave lithotripsy (ESWL) is influenced by various factors, including stone density, and is determined through computed tomography scans in terms of Hounsfield units (HU).

MATERIALS AND METHODS

This retrospective single-center study was conducted in the King Fahad Hospital. Sixty-seven adult patients with renal and ureteric stones were selected randomly and enrolled in the study. Their ages ranged from 20 to 69 years. The patients were examined with non-contrast enhancement (NCCT) to assess the HU of their stones and were consequently treated with ESWL.

RESULTS

Of the 67 patients, 37.3% had stones that were completely fragmented, while 62.7% had stones that were partially fragmented. The HU, location of the stone, multiplicity of the stone, and patient age were found to be significant factors contributing to stone fragility (p-values < 0.05). The HU data were found to have a positive significant linear correlation with serum calcium (r = 0.28, p-value = 0.036), while serum acid had a negative correlation (r = -0.55, p-value < 0.001). Thus, the probability of calcium-containing stone formation increases with increased HU. In contrast, uric acid stone formation likely develops with decreasing HU with serum uric acid. Renal stones in patients with diabetes mellitus and hypertension were not completely fragmented compared to those without clinical history.

CONCLUSIONS

Mean HU, location of the stone, laterality, stone status, and the number of ESWL sessions are the most significant factors affecting stone fragility. CT attenuation values can predict the composition of stones from serum calcium and uric acid examinations. Hypertension and diabetes mellitus are risk factors for renal stone fragmentation.

Factors influencing the vancomycin trough level in patients admitted at King Fahad Specialist Hospital, Qassim, KSA

OBJECTIVE

Although vancomycin is an effective antibiotic against methicillin-resistant Staphylococcus aureus, its usage is often associated with nephrotoxicity which necessitates optimization of the vancomycin dose to be both precise and appropriate. To achieve this, the importance of therapeutic drug monitoring arises, and serum trough vancomycin concentrations are the most accurate and practical method for monitoring vancomycin effectiveness and even risk of nephrotoxicity. This study evaluated the influences on the trough levels of vancomycin given to admitted patients at King Fahad Specialist Hospital (KFSH).

PATIENTS AND METHODS

This cross-sectional hospital-based study has been conducted at KFSH among 197 patients, of which 53.3% were male and 46.7% were female. They received intravenous vancomycin at intermittent dose of 30 mg/kg/day with no clinical or laboratory renal impairment. The serum was drawn trough concentrations within 15 to 45 minutes before the fourth vancomycin dose.

RESULTS

One-way ANOVA test showed a significantly higher trough level of vancomycin among females, patients older than 50 years, and CCU and CSICU admitted patients (p-value < 0.05). Spearman correlation test also showed significant correlation with the serum vancomycin trough levels, site of infection (Rho=0.406, p=0.009), age (Rho=0.341, p=0.044) and patients' admission (Rho=0.321, p=0.041).

CONCLUSIONS

Even at body adjusted dosing, vancomycin serum trough levels varied among patients with significant variations of age, gender, site of infection and type of admission, especially CCU and CSICU, which raises the concept of dose individualization, age and gender considerations especially among critically ill patients.