Renal pelvic pressure generally remains lower than the backflow level (30 mm Hg) during MPCNL via a 14- to 18-French percutaneous tract. Any factors that brought about poor drainage would result in temporarily elevated RPP greater than 30 mm Hg, and many such occurrences of high pressure would have an accumulating effect, which means enough backflow to cause bacteremia and postoperative fever.

There has been continuing controversy regarding multiple tracts in a percutaneous nephrolithotomy (PCNL) session that may bring more complications, especially severe bleeding need for transfusion, even nephrectomy. Little tracts may bring less trauma to renal parenchyma than standard PCNL tracts. We carried minimally invasive PCNL (MPCNL) in treating staghorn calculi with multiple 16Fr percutaneous tracts in a single session, in an attempt to get high stone free with little trauma, and compared the morbidity of standard PCNL procedures in a prospective trial. A total of 54 consecutive patients with staghorn calculi were prospectively randomized for MPCNL (29) and PCNL (25). The size and location of stone, operative parameters, number of tracts, stone-free rate, operating time, hospital stay and complications were analyzed. In MPCNL group, a total of 67 percutaneous tracts were established in 29 renal units, while 28 tracts in 25 renal units in PCNL group. Compared to PCNL, MPCNL was associated with higher clearance rate (89.7 vs. 68%, p = 0.049), less chance need for adjunctive procedure of SWL or second-look PCNL (24.1 vs. 60%, p = 0.007), while a similar complication rate (37.9 vs. 52%, p = 0.300). In conclusion, with the development of instruments and increased experience, judiciously made multiple percutaneous tracts in a single session of MPCNL for treating staghorn calculi were safe, feasible and efficient with an acceptable morbidity.

Our experience with the Chinese MPCNL shows that it is safe and effective for managing all kinds of upper-tract calculi.

The Chinese minimally invasive percutaneous nephrolithotomy (MPCNL) was a modified version of standard PCNL which utilizes smaller tract and sheaths. The aim of this study was to present our experience on its efficacy and safety, and to grade its complications according to the modified Clavien classification. Between 1992 and 2011, 12,482 patients who underwent 13,984 MPCNL procedures entered this study. Data on stone size, access number, operative time, hospital length of stay, stone-free rate (SFR), and complications according to the modified clavien system were evaluated prospectively. Their mean age of patients was 47.6 years (range 0.6-93). The mean stone size was 3.2 ± 0.8 (1.4-7.4) cm. The mean operative time was 83 ± 38 min. Mean hemoglobin drop was 13.5 ± 11.3 g/L. Mean hospital stay was 10.3 ± 6.4 days (2-22 days). The initial SFR after first procedure was 78.6 %. In 14.7 % of cases with a second look, the SFR increase to 89.9 %. At 3 months after auxiliary procedures (re-PCNL, ureterorenoscopy, and shock wave lithotripsy), the overall SFR was achieved to 94.8 %. A total of 3,624 complications (25.92 %) were observed in 2,591 (18.53 %) procedures. There were 2,355 grade I (16.84 %), 706 grade II (5.05 %), 553 grade III (3.95 %), 7 grade IV (0.05 %), and three death of grade V (0.02 %) complications. This large-scale, contemporary analysis confirms MPCNL is still a safe and efficacious treatment option of kidney stones with a high stone-free rate and uncommon rate of high grade complications.

Renal pelvic pressure generally remains lower than the level required for a backflow (30 mm Hg), during MPCNL via 14 to 18-Fr percutaneous tract. Any factor, which causes bad drainage, will result in a temporarily elevated renal pelvic pressure greater than 30 mm Hg; and multiple temporary high-pressure episodes can have a cumulative effect, which means that there will be enough backflow to cause a bacteremia.