The use of anatomical landmarks for percutaneous nephrolithotomy

Objective: The aim of our study was to describe the external anatomical landmarks and angles as a training guide for urologists in the performance of percutaneous nephrolithotomy (PCNL) in the prone position.

Materials and Methods: Between 2006 and 2008, 50 patients (including 10 resident cases) undergoing PCNL met the study criteria. The inclusion criteria consisted of patients with renal stones scheduled for a lower calyceal puncture PCNL where the number of attempts to access the calyx ≤ 3, and clear urine was seen draining from the needle. The exclusion criteria consisted of previous ipsilateral kidney surgery, severe hydronephrosis, anomalies of the renal or skeletal systems, BMI>30 kg/m2, upper/middle calyceal puncture and age ≤18. Several anatomical landmarks and angles were measured, recorded and analyzed.

Results: The mean length of (Pi) was 10.1±1.7 cm (range 7-14), (Pe ) was 9.9±1.7 cm (range 6-13), (a) was 11.2±2.8 cm (range 5.5-17), (b) was 5.3±2.3 cm (range 1.5-11 cm), (x) was 5.1±1.9 cm (range 1-8), (x1) was 3.3±1.7 cm (range 1.5-8.2), (y) was 7.1±1.7 cm (range 3.3-11.6), (y1) was 3.8±1.6 cm (range 1-9) and (t) was 4.9±1.7 cm (range 3-9). The mean angle for (a) was 49±13º (range 30-70º), (b) was 41±13º (range 20-70º) and (g) was 61±13º (range 28-80º). In resident cases, the median number of attempts was 1 (range 1-3), the median overall time for successful access was 7.25 minutes (range 2-12) and the median fl uoroscopy time was 62.5 seconds (range 30-150).

Conclusion: A knowledge of these anatomical landmarks and angles may increase the capacity of urologists to repetitively perform the precise task of percutaneous access of the lower calyceal during PCNL.