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 successively in the right and left prone oblique position. The kidney axis and minimal distances from the cutaneous plane at the level of the upper and lower poles were measured. Axial and tangential simulated percutaneous approaches to the upper renal calix were compared in term of risk of damage to the pulmonary, splenic, and hepatic parenchyma.

Results: The transversal anteversion angle was statistically comparable for right and left kidneys, but the sagittal anteversion angle was significantly higher for right kidneys (p = 0.05). The minimal distance from the cutaneous 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 upper renal calix or through the 10th intercostal space compared to a puncture via the l1th space (p = 0.0001).

Conclusion: A percutaneous puncture of the upper pole of the kidney above the 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 hepatic injury could be carried out in these cases.