IMAGING

Evaluation of Living Renal Donors: Accuracy of Three-dimensional 16-section CT
Rastogi N, Sahani DV, Blake MA, Ko DC, Mueller PR
Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
Radiology 2006; 240: 136-44

• Purpose: To retrospectively assess the sensitivity and specificity of three-dimensional (3D) 16-section computed tomography (CT) in the evaluation of vessels, pelvicalyceal system, and ureters in living renal donors, with surgical findings as the reference standard.
• Materials and methods: This was a HIPAA-compliant study. Institutional review board approval was obtained for the review of subjects’ medical records and data analysis, with waiver of informed consent. Forty-six renal donors (18 men, 28 women; mean age, 42 years) were examined with 16-section CT. Two blinded reviewers independently studied renal vascular and urographic anatomy of each donor CT scans by fist using 3D images alone, then transverse images alone, and finally transverse and 3D data set. Image quality, degree of diagnostic confidence, and time used for review were recorded. Sensitivity and specificity were calculated.
• Results: For 3D images, transverse images, and transverse in conjunction with 3D data sets, the respective sensitivity and specificity of CT in evaluation of accessory arteries by reviewer 1 were 100% and 100%, 89% and 100%, and 100% and 100%, and those by reviewer 2 were 89% and 97%, 89% and 100%, and 89% and 100%; the respective sensitivity and specificity in evaluation of venous anomalies by reviewer 1 were 100% and 98%, 100% and 98%, and 100% and 98%, and those by reviewer 2 were 100% and 98%, 100% and 95%, and 100% and 98%. For focused comprehensive assessment of renal donors with 3D scans alone, a reviewer on average (average of reviewers 1 and 2) used 2.4 minutes per scan, demonstrated full confidence in 93%, and rated the quality as excellent in 76%.
• Conclusion: For focused assessment of renal vascular and urographic anatomy, review of 3D data set alone provides high sensitivity and specificity with regard to findings seen at surgery.
  
  
• Editorial Comment
  Recently, several studies have been shown that CT angiography (CTA) with multi-detector row technology (16-channel) has superior accuracy than conventional angiography and non-selective digital subtraction angiography for the evaluation of living renal donors. To obtain such high accuracy, the images must be obtained with 1 mm slice thickness reconstruction interval during arterial and venous phases. Using this protocol CTA will demonstrate with clarity almost all supernumerary renal arteries and veins, early branching of vessels and abnormalities of pelvicaliceal system and ureter. Thus, the overall accuracy of 16-channel- CTA for detection and classification of surgically relevant arterial and venous variants may reach 100%. However this protocol of investigation has important drawback since offers a huge number of axial images making their interpretation by the radiologist , a meticulous and time consuming process .The authors shows that in a series of 46 consecutive renal donors, who had surgical findings for comparison, review of 3D images alone obtained with 16-section CT was faster and adequate .The respective mean accuracy for evaluation of renal arterial, venous and urogram findings was 98%, 98% and 100% for 3D images alone. Three-dimensional images may also help the surgeons by offering them fewer and relevant images of donor anatomy, which can be displayed in the operating room during surgical procedure. As pointed out by the authors more studies will need to be performed to validate these results.

Dr. Adilson Prando
Chief, Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil