Direct percutaneous approach to the upper pole of the kidney: MRI anatomy with assessment of the visceral risk

Purpose: In an attempt to determine the visceral risk secondary to a direct percutaneous puncture of the upper renal calix, the anatomic relations of the upper pole of the kidney were studied by magnetic resonance imaging. Methods: Examination was performed on 25 normal volunteers placed successiv ely in the right and left prone oblique position, The kidney axis and minim al distances from the cutaneous plane at the level of the upper and lower p oles were measured. Axial and tangential simulated percutaneous approaches to the upper renal calix were compared in term of risk of damage to the pul monary, splenic, and hepatic parenchyma. Results: The transversal anteversion angle was statistically comparable for right and left kidneys, but the sagittal anteversion angle was-significant ly higher for right kidneys (p = 0.05), The minimal distance from the cutan eous plane was statistically comparable for the upper and lower poles, The lower pole was significantly deeper for left than right kidneys (p = 0.01). The visceral risk was statistically comparable for left and right kidneys and was significantly higher in case of an approach in the axis of the uppe r renal calix or through the 10th intercostal space compared to a puncture via the 11th space (p = 0.0001). Conclusion: A percutaneous puncture of the upper pole of the kidney above t he 11th rib increases the risk of visceral damage. Preoperative evaluation, with the aid of CT scan or MRI, of the risk of pulmonary, splenic, or hepa tic injury could be carried out in these cases.