Which is access suitable for a solitary upper pole renal stone? A possible novel criterion

The aim of the present study was to discover a new criterion for choosing subcostal or supracostal upper pole renal access before performing PCNL in upper pole renal stone cases.

Between April 2006 and July 2009 we performed 35 subcostal upper poles PCNL in solitary upper pole stone cases. The inclusion criteria were stone size >1.5 cm or stone size <1.5 cm and resistant to extracorporeal shockwave lithotripsy. The exclusion criteria were renal anomalies, uretero-pelvic junction obstruction, multiple stone (associated pelvic or a lower pole stone) and any contraindication for surgery. We determined access length as the new criterion (the distance between the point of needle entrance and lower border of stone on the skin) and access success, in all patients. Then we analyzed the relationship between these two main variables and used roc curve to find a reliable cut point of access length.

The mean of access length was 9.72 cm (range: 6-14) and access was successful in 29 (82.8%) patients. Between measured variables, access length was the only variable that related to access success (P=0.04); furthermore, two reliable cut points (8 cm and 12 cm) for predicting access success. If access length was <8 cm or 8-12 cm or >12 cm, the access success was 100%, 83% and 50%, respectively.

Access length can be used as a criterion for choosing subcostal upper pole renal PCNL and predicting its success, in the case of solitary upper pole renal stones 12 cm can serve as a critical valve for a decision.