Comparative assessment of multiple-tract vs single-tract percutaneous nephrolithotomy.

INTRODUCTION: To investigate the efficacy and safety of multi-tract percutaneous nephrolithotomy (PNL) against the benchmark of the single-tract approach. METHODS: A retrospective analysis of 391 consecutive PNL procedures was conducted in our tertiary referral center between April 2016 and March 2020. Clinical outcome parameters such as stone-free rate, operation time, postoperative complications according to Clavien-Dindo, length of hospital stay and time to ipsilateral recurrence resulting in active treatment were assessed. RESULTS: Multi-tract PNL and single-tract PNL were performed in 37 (9%) and 354 (91%) cases respectively. At baseline, compared to single-tract PNL, multi-tract PNL cases were characterized by significantly larger stone burden (2.62 vs 0.97 cm3 , P < .00), lower Hounsfield units (HU) (751 vs 1017 HU, P < .01), a more complex S.T.O.N.E. (size, tract length, obstruction, number of calyces, essence) score (P < .00) and a higher rate of high-risk stone formers (59 vs 19%, P < .00). Analysis of outcome revealed shorter operation time and length of hospital stay for single-tract PNL compared to multi-tract PNL (P < .01). However, the difference in terms of stone-free rates (92% vs 88%), complication rates (43% vs 28%) and time to active retreatment due to ipsilateral recurrence was not statistically significant (P > .05). CONCLUSION: In this retrospective single-center analysis, a multi-tract PNL has been proved to be an efficient and safe expansion of single-tract PNL for large stone burden and complex kidney stone disease. Future prospective research should focus on the procedure's potential effectiveness in reducing the number of interventions until stone-free status in patients with massive stone disease.

Does presence of a mid-ocean ridge enhance biomass and biodiversity?

In contrast to generally sparse biological communities in open-ocean settings, seamounts and ridges are perceived as areas of elevated productivity and biodiversity capable of supporting commercial fisheries. We investigated the origin of this apparent biological enhancement over a segment of the North Mid-Atlantic Ridge (MAR) using sonar, corers, trawls, traps, and a remotely operated vehicle to survey habitat, biomass, and biodiversity. Satellite remote sensing provided information on flow patterns, thermal fronts, and primary production, while sediment traps measured export flux during 2007-2010. The MAR, 3,704,404 km(2) in area, accounts for 44.7% lower bathyal habitat (800-3500 m depth) in the North Atlantic and is dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis contributing to habitat heterogeneity. The MAR fauna comprises mainly species known from continental margins with no evidence of greater biodiversity. Primary production and export flux over the MAR were not enhanced compared with a nearby reference station over the Porcupine Abyssal Plain. Biomasses of benthic macrofauna and megafauna were similar to global averages at the same depths totalling an estimated 258.9 kt C over the entire lower bathyal north MAR. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR. There is no enhancement of biological productivity over the MAR; oceanic bathypelagic species are replaced by benthic fauna otherwise unable to survive in the mid ocean. We propose that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime.