Revolutionizing Renal Stone Treatment: The Role of Dual-Energy CT and Factors Affecting Shock Wave Lithotripsy Outcomes

We all share the concern for loved ones suffering from kidney or ureteral stones, and understanding the nuances of their treatment is crucial. Extracorporeal Shock Wave Lithotripsy (ESWL) has proven to be effective, but are we utilizing the most advanced diagnostic tools before this procedure?

Let's explore how Dual-Energy CT (DECT) is revolutionizing the evaluation of renal stones and enhancing the success of ESWL.

DECT Evaluation Prior to ESWL

Computed Tomography (CT), particularly Dual-Energy CT (DECT), stands as the gold standard for pre-ESWL evaluation of kidney stones. DECT surpasses Contrast-Enhanced CT (CECT), offering precise insights into stone burden, composition, and fragility. Understanding these facets beforehand enhances the success of ESWL treatment.

The article: Assessment of Hounsfield Units and Factors Associated with Fragmentation of Renal Stones by Extracorporeal Shock Wave Lithotripsy: A Computerized Tomography Study highlights the importance of DECT in providing a more accurate classification of renal stones, considering stone burden, composition, and fragility. Additionally, we provide insights into the specific patient positioning and scan parameters crucial for obtaining optimal DECT results.

Optimizing Dual-Energy CT (DECT): Exploring the Impact of Patient Positioning, Scan Parameters, and Post-Processing Techniques

Patient Positioning

• Prone position with feet first.
• Single volume collected from the diaphragm to just below the symphysis pubis.

Scan Parameters

• Voltage: 120 kV
• Current: 50 mAs
• Scan time: 10-12 s
• Delay with one breath hold: 4 s
• Slice thickness: 2 mm
• Gantry not tilted
• Chosen kernel: Standard for soft tissue

Post-Processing on Dedicated Workstation

• Curved multiplanar and 3D volume rendering techniques.
• Axial, coronal, sagittal, and oblique reconstruction.
• Techniques involving maximum intensity and medium volume.

Understanding Hounsfield Units (HU)

There's a profound link between calculus density measured in HU and the success of ESWL sessions. Our study found a linear relationship, emphasizing that calculus density is a stronger predictor of outcome than size alone. The ideal outcome is associated with lower HU and smaller stone sizes.

HU-Based Insights

• < 750 HU: 80% needed three or fewer ESWL sessions; 88% had complete clearance.
• 750 HU: 72% needed three or more ESWL sessions; 65% had complete clearance.
• HU of 841.95 and 978.79 for partial, fragmented stones.

Figure 3. The regression estimation curve shows a positive relationship for CT number with serum calcium (a) and a negative linear relationship with serum uric acid (b).

Types of Kidney Stones

Understanding the types of kidney stones is fundamental to effective treatment. From calcium stones to struvite, uric acid, and cystine stones, each requires a tailored approach. We delve into the characteristics of each type below, shedding light on the factors contributing to their formation.

1. Calcium Stones: The most prevalent type, calcium stones, are often linked to dietary factors and metabolic disorders, necessitating a nuanced approach to treatment.
2. Struvite Stones: Formed due to infections like urinary tract infections, these stones require swift intervention to prevent complications.
3. Uric Acid Stones: Common among individuals with specific dietary habits and genetic predispositions, uric acid stones underscore the importance of lifestyle modifications.
4. Cystine Stones: Typically occurring in those with hereditary disorders, cystine stones highlight the need for personalized treatment strategies.Note: DECT is valuable in identifying pure uric acid, cystine, and calcium oxalate stone types.

Image 1. Type of Kidney Stones

Retrospective Single-Center Study

In a study at King Fahad Hospital, 67 adult patients with renal and ureteric stones were examined using non-contrast CT (NCCT). Exclusion criteria included pregnancy, febrile UTIs, anticoagulant treatment, age below 20, and thyroid diseases.

Factors Affecting Fragmentation:

Factors such as stone laterality, status, location, and clinical history significantly predict renal stone fragmentation.

Diabetes and Hypertension:

Our study reveals a relationship between stone fragility, diabetes, and hypertension. Stones in diabetic and hypertensive patients are less easily fragmented.

Study Limitations and Future Recommendations

While this study: Assessment of Hounsfield Units and Factors Associated with Fragmentation of Renal Stones by Extracorporeal Shock Wave Lithotripsy: A Computerized Tomography Study provides valuable insights, it acknowledges limitations such as a modest sample size. Future research with larger samples and additional stone composition analysis methods is recommended for more comprehensive results.

Conclusion

In the quest for enhanced ESWL outcomes, Dual-Energy CT (DECT) proves to be a transformative tool. Mean HU, stone location, laterality, stone status, and ESWL session count are crucial factors. Additionally, understanding stone composition through CT attenuation values can further guide treatment decisions. Diabetes and hypertension emerge as risk factors for renal stone fragmentation. A call for prospective standardization in HU measurements and patient history underscores the need for collaborative efforts in shaping the future of kidney stone treatment.

References:

1. Alharbi, A. S., Gameraddin, M., Gareeballah, A., Shrwani, Z. J., Sindi, M. A., Alsaedi, H. I., Qurashi, A. A., Aloufi, K. M., Alshamrani, A. F. A., & Alzain, A. F. (2024). Assessment of Hounsfield Units and Factors Associated with Fragmentation of Renal Stones by Extracorporeal Shock Wave Lithotripsy: A Computerized Tomography Study. Tomography (Ann Arbor, Mich.), 10(1), 90–100. https://doi.org/10.3390/tomography10010008
2. Gupta, N. P., Ansari, M. S., Kesarvani, P., Kapoor, A., & Mukhopadhyay, S. (2005). Role of computed tomography with no contrast medium enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi. BJU international, 95(9), 1285–1288. https://doi.org/10.1111/j.1464-410X.2005.05520.x
3. https://www.urologysanantonio.com/kidney-stones/lithotripsy
4. https://www.drvamsikrishna.com/services/kidney-stones-treatment/
5. https://www.parashospitals.com/blogs/causes-and-types-of-kidney-stones