Statistical properties of two-dimensional elastic turbulence.

We numerically investigate the spatial and temporal statistical properties of a dilute polymer solution in the elastic turbulence regime, i.e., in the chaotic flow state occurring at vanishing Reynolds and high Weissenberg numbers. We aim at elucidating the relations between measurements of flow properties performed in the spatial domain with the ones taken in the temporal domain, which is a key point for the interpretation of experimental results on elastic turbulence and to discuss the validity of Taylor's hypothesis. To this end, we carry out extensive direct numerical simulations of the two-dimensional Kolmogorov flow of an Oldroyd-B viscoelastic fluid. Static pointlike numerical probes are placed at different locations in the flow, particularly at the extrema of mean flow amplitude. The results in the fully developed elastic turbulence regime reveal large velocity fluctuations, as compared to the mean flow, leading to a partial breakdown of Taylor's frozen-field hypothesis. While second-order statistics, probed by spectra and structure functions, display consistent scaling behaviors in the spatial and temporal domains, the third-order statistics highlight robust differences. In particular the temporal analysis fails to capture the skewness of streamwise longitudinal velocity increments. Finally, we assess both the degree of statistical inhomogeneity and isotropy of the flow turbulent fluctuations as a function of scale. While the system is only weakly nonhomogenous in the cross-stream direction, it is found to be highly anisotropic at all scales.

The Italian Consensus on minimally invasive simultaneous resections for synchronous liver metastasis and primary colorectal cancer: A Delphi methodology.

At the time of diagnosis synchronous colorectal cancer, liver metastases (SCRLM) account for 15-25% of patients. If primary tumour and synchronous liver metastases are resectable, good results may be achieved performing surgical treatment incorporated into the chemotherapy regimen. So far, the possibility of simultaneous minimally invasive (MI) surgery for SCRLM has not been extensively investigated. The Italian surgical community has captured the need and undertaken the effort to establish a National Consensus on this topic. Four main areas of interest have been analysed: patients' selection, procedures, techniques, and implementations. To establish consensus, an adapted Delphi method was used through as many reiterative rounds were needed. Systematic literature reviews were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses instructions. The Consensus took place between February 2019 and July 2020. Twenty-six Italian centres participated. Eighteen clinically relevant items were identified. After a total of three Delphi rounds, 30-tree recommendations reached expert consensus establishing the herein presented guidelines. The Italian Consensus on MI surgery for SCRLM indicates possible pathways to optimise the treatment for these patients as consensus papers express a trend that is likely to become shortly a standard procedure for clinical pictures still on debate. As matter of fact, no RCT or relevant case series on simultaneous treatment of SCRLM are available in the literature to suggest guidelines. It remains to be investigated whether the MI technique for the simultaneous treatment of SCRLM maintain the already documented benefit of the two separate surgeries.

The critical view of safety during laparoscopic cholecystectomy: Strasberg Yes or No? An Italian Multicentre study.

BACKGROUND: Laparoscopic cholecystectomy is considered the gold standard for the treatment of gallbladder lithiasis; nevertheless, the incidence of bile duct injuries (BDI) is still high (0.3-0.8%) compared to open cholecystectomy (0.2%). In 1995, Strasberg introduced the "Critical View of Safety" (CVS) to reduce the risk of BDI. Despite its widespread use, the scientific evidence supporting this technique to prevent BDI is controversial. METHODS: Between March 2017 and March 2019, the data of patients submitted to laparoscopic cholecystectomy in 30 Italian surgical departments were collected on a national database. A survey was submitted to all members of Italian Digestive Pathology Society to obtain data on the preoperative workup, the surgical and postoperative management of patients and to judge, at the end of the procedure, if the isolation of the elements was performed according to the CVS. In the case of a declared critical view, iconographic documentation was obtained, finally reviewed by an external auditor. RESULTS: Data from 604 patients were analysed. The study population was divided into two groups according to the evidence (Group A; n = 11) or absence (Group B; N = 593) of BDI and perioperative bleeding. The non-use of CVS was found in 54.6% of procedures in the Group A, and 25.8% in the Group B, and evaluating the operator-related variables the execution of CVS was associated with a significantly lower incidence of BDI and intraoperative bleeding. CONCLUSIONS: The CVS confirmed to be the safest technique to recognize the elements of the Calot triangle and, if correctly performed, it significantly impacted on preventing intraoperative complications. Additional educational programs on the correct application of CVS in clinical practice would be desirable to avoid extreme conditions that may require additional procedures.

Effects of large-scale advection and small-scale turbulent diffusion on vertical phytoplankton dynamics.

Turbulence has been recognized as a factor of paramount importance for the survival or extinction of sinking phytoplankton species. However, dealing with its multiscale nature in models of coupled fluid and biological dynamics is a formidable challenge. Advection by coherent structures, such as those related to winter convection and Langmuir circulation, is also recognized to play a role in the survival and localization of phytoplankton. In this work we revisit a theoretically appealing model for phytoplankton vertical dynamics, and numerically investigate how large-scale fluid motions affect the survival conditions and the spatial distribution of the biological population. For this purpose, and to work with realistic parameter values, we adopt a kinematic flow field to account for the different spatial and temporal scales of turbulent motions. The dynamics of the population density are described by an advection-reaction-diffusion model with a spatially heterogeneous growth term proportional to sunlight availability. We explore the role of fluid transport by progressively increasing the complexity of the flow in terms of spatial and temporal scales. We find that, due to the large-scale circulation, phytoplankton accumulates in downwelling regions and its growth is reduced, confirming previous indications in slightly different conditions. We then explain the observed phenomenology in terms of a plankton filament model. Moreover, by contrasting the results in our different flow cases, we show that the large-scale coherent structures have an overwhelming importance. Indeed, we find that smaller-scale motions only quite weakly affect the dynamics, without altering the general mechanism identified. Such results are relevant for parametrizations in numerical models of phytoplankton life cycles in realistic oceanic flow conditions.

Do We Have Another Option to Treat Bleeding Hemorrhoids? The Emborrhoid Technique: Experience in 16 Patients.

BACKGROUND: Hemorrhoidal disease is very common in western countries and rectal bleeding is the main symptom complained by patients. Nowadays the ultimate goal of treatment is to block the bleeding with minimally-invasive techniques to minimize post-procedural pain. OBJECTIVE: The aim of this study is to assess the preliminary results of the emborrhoid technique (embolization of the superior rectal arteries branches) as a new tool for the proctologist to treat severe bleeding hemorrhoids causing anemia. Many categories of patients might benefit from this treatment, such as patients not eligible for conventional surgery, patients not responding to conventional treatment and fit patients with severe bleeding who refused endorectal surgical therapy. METHODS: From May 2017 to November 2018 a total of 16 patients with chronic rectal bleeding due to hemorrhoids underwent super-selective embolization of the superior rectal arteries at the department of General Surgery in La Spezia, S. Andrea Hospital, Italy. Median age was 59 years. 14 patients were males (87.5%). RESULTS: No post-procedural and short-term complications were observed at maximum follow up (12 months). The reduction of rectal bleeding with improvement of the quality of life was obtained in 14 patients (87.5%). CONCLUSION: Our study, although small in number, demonstrates that embolization of superior rectal arteries with coils to treat severe bleeding due to hemorrhoids is safe and effective and does not lead to immediate complications.

Italian multi-society modified Delphi consensus on the definition and management of anastomotic leakage in colorectal surgery.

INTRODUCTION: The incidence of anastomotic leak (AL) has not decreased over the past decades and some important grey areas remain in its definition, prevention, and management. The aim of this study was to reach a national consensus on the definition of AL and to identify key points to be applied in clinical practice. METHODS: A 3-step modified Delphi method was used to establish consensus. Ten representative members of the major Italian surgical scientific societies with proven colorectal expertise were selected after a call to action. After a comprehensive literature search, each expert drew a list of evidence-based statements which were voted in round one by the scientific board. Panel members were asked to mark "totally disagree", "partially agree" or "totally agree" for each statement and provide comments. The same voting method was used for round 2. Round 3 consisted of a final face-to-face meeting. RESULTS: Thirty-three statements (clustered into 14 topics) were included in round 1. Following the third voting round, a final list of 16 items was formulated, which encompass the following 9 topics: AL definition, patient- and operative-related risk factors, prevention measures, bowel preparation, surgical technique, intraoperative assessment, early diagnosis, radiological diagnosis and management of specific patterns of AL. The overall response rate was 100% for all items in all the three rounds. CONCLUSIONS: This Delphi survey identified items that expert colorectal surgeons agreed were important to be applied in the prevention, diagnosis, and management of AL. This represents the first consensus involving all relevant national scientific societies, defining important and shared concepts in the diagnosis and management of AL.

Pre-operative Renal Artery Embolization in Laparoscopic Radical and Partial Nephrectomy: A Multidisciplinary Approach to Renal Tumors.

BACKGROUND: Despite being widely adopted, the laparoscopic approach to radical and partial nephrectomy is still burdened by high rates of hemorrhagic complications, which require blood transfusions and conversion to open surgery with increased morbidity. While pre-operative renal artery embolization (PRAE) can prevent intraoperative blood loss and vascular injuries, its prophylactic use is still a matter of debate. This study evaluated the safety and efficacy of PRAE in overcoming the main pitfalls of laparoscopy, which are related to the absence of tactile feedback. METHODS: Data from 48 patients who underwent laparoscopic nephrectomy for cancer (34 laparoscopic radical nephrectomy (LRN) and 14 "off-clamp" laparoscopic partial nephrectomy (LPN) after selective and superselective PRAE, respectively) were retrospectively evaluated. RESULTS: The overall median blood loss was 50 ml and only 2 patients (4%) required one unit of blood products. While conversion to open surgery was not required in the LPN group, one case in the LRN group was converted to open surgery due to intraoperative incoercible bleeding from an unrecognized, and thus not embolized, aberrant inferior polar artery. Post-embolization syndrome occurred in 7 patients (15%), resulting in mild flank pain and nausea. No patients in the LPN group experienced new onset of acute renal failure. CONCLUSION: Our experience supports pre-operative renal embolization as a safe, minimally invasive procedure that is effective for reducing perioperative bleeding in the laparoscopic setting.

The Italian National Registry for minimally invasive pancreatic surgery: an initiative of the Italian Group of Minimally Invasive Pancreas Surgery (IGoMIPS).

The value of minimally invasive pancreatic surgery (MIPS) is still uncertain, despite the growing number of publications, including reviews and meta-analyses, and the quick diffusion of these procedures worldwide. The Italian Group of Minimally Invasive Pancreas Surgery (IGoMIPS) was created under the auspices of three Scientific Societies: Associazione Italiana Studio Pancreas (AISP), Associazione Italiana Chirurgia Epato-Bilio-Pancreatica (AICEP, former IT-IHPBA), and Società Italiana di Chirurgia Endoscopica (SICE). The main aim of IGoMIPS is to develop and implement a national registry for MIPS. IGoMIPS was founded on February 22, 2019 in Pisa. The IGoMIPS registry became operational in September 2019, following approval by the Ethic Committees of founding Institutions, inscription into the Registry of Patient Registries (RoPR), and a wrap-up meeting held in Bologna during the Annual Congress of the Italian Surgical Society. During this meeting IGoMIPS members approved that the Italian Registry will provide data to the European Registry, while retaining the right to analyze and publish Italian data. An audience survey was also conducted to obtain information on perceived value and current implementation of MIPS in founding Institutions. MIPS is performed in 94.7% of IGoMIPS centers, including pancreaticoduodenectomy in 42.1%. Robotic assistance was employed in 52.6% of Institutions. The annual volume of MIPS was 6-10 cases in 38.9% of the centers, 11-20 cases in 16.7%, 21-30 cases in 22.2%, and > 30 cases in 22.2%. The registry was felt to be extremely important for both safety improvement and educational purposes by 94.5% of the centers.

Is Needlescopic Cholecystectomy a Safe Way to Improve Mininvasiveness and Cosmesis in Young Female Patients?

INTRODUCTION: Needlescopic cholecystectomy (NC) was introduced in the late 1990s. It uses a reduced trocar caliber in an otherwise standard four-port laparoscopic cholecystectomy (LC) and seeks to achieve "scarless" surgery without compromising patient safety. MATERIALS AND METHODS: Between May 2016 and November 2017, 29 patients underwent elective NC at the Department of General Surgery of Sant'Andrea Hospital (La Spezia, Italy). Inclusion criteria were female sex, age between 18 and 45 years, good performance status (ASA 1-2) and BMI lower than 25. Twenty-one patients underwent a standard 4-port technique: 12mm port in the supraumbilical area, 5mm port in the subxiphoid position, 3mm port in the mid-epigastric area and another 3 mm port in the right mid-clavicular position. In 8 patients, 3mm ports were replaced by 2mm angiocath. A Critical View of Safety (CVS) was achieved in all procedures. Intra-operative cholangiography (IOC) via the cystic duct before any transection of the structures was routinely performed in selected cases, such as those with an unclear biliary anatomy or risk factors for main-duct stones. In our institution, laparoscopic transcystic common bile duct (CBD) exploration is routinely performed in CBD lithiasis. RESULTS: The mean operative time was 66.79 min (range 25-120 min). IOC was performed in 12 patients (41.4%) with suspected choledocolythiasis. There was no conversion to conventional laparoscopic cholecystectomy or open cholecystectomy. The mean hospital stay was 1.48 days (1-7 days). A Clavien-Dindo IIIB complication occurred in one patient on the third postoperative day. The mean VAS pain score was 3 (0-7). Closure of the skin with primary intention was achieved in all patients. Mean return to work was 6.76 days (3-15 days) and the mean return to previous physical activity was 12.17 days (4-30 days). All of the patients completed the Scar Satisfaction Questionnaire: 26 (89.7% ) and 3 patients (10.3%) were very satisfied and satisfied, respectively. CONCLUSION: Any effort to reduce invasiveness and improve cosmesis must not jeopardize safety. Our case series demonstrates that needlescopy can be safely associated with intraoperative cholangiography to recognize CBD stones. This technique offers the advantage of minor postoperative pain, better cosmesis results, early return to routine life activities and great satisfaction for the patient. Needlescopy is a valuable and safe alternative that is suitable for elective cholecystectomy in properly selected patients, such as young female patients.

Reaction fronts in persistent random walks with demographic stochasticity.

Standard reaction-diffusion systems are characterized by infinite velocities and no persistence in the movement of individuals, two conditions that are violated when considering living organisms. Here we consider a discrete particle model in which individuals move following a persistent random walk with finite speed and grow with logistic dynamics. We show that, when the number of individuals is very large, the individual-based model is well described by the continuous reactive Cattaneo equation (RCE), but for smaller values of the carrying capacity important finite-population effects arise. The effects of fluctuations on the propagation speed are investigated both considering the RCE with a cutoff in the reaction term and by means of numerical simulations of the individual-based model. Finally, a more general Lévy walk process for the transport of individuals is examined and an expression for the front speed of the resulting traveling wave is proposed.

Side-to-Side Anastomosis In Left Hemicolectomy, Why and When: A Single-Center Experience.

BACKGROUND: Laparoscopic colectomy represents a safe, effective and well-established procedure for both benign and malignant colic disease. Transanal anastomosis (TA) with a circular stapler is the most commonly performed anastomotic technique in laparoscopic left hemicolectomy (LLH). We report our experience with side-to-side anastomosis (STSA) and side-to-end anastomosis (STEA) in selected patients with both emergency and elective LLH. METHODS: A systematic review of the PubMed database was performed on recent studies that compared different anastomotic techniques after LLH. We collected internal data from June 2014 to July 2018 and compared our experience with the literature. The primary outcome was the anastomotic complication rate. RESULTS: During the observation period, 158 patients underwent left hemicolectomy (LH). One-hundred-nineteen patients had malignant disease; 36 underwent surgery for complicated diverticular disease, one had a large strangulated incisional hernia, one had a sigmoid volvulus, and one had a sigmoid localization of endometriosis. Thirty open left hemicolectomies were performed. In 128 cases, a minimally invasive approach was used. Since conversion to open was necessary in 10 of these cases, 118 were totally LLH. STSA was performed in 64 cases; seven in an emergency setting and 57 in elective procedures. The overall anastomotic leak rate was 3.1% (2/64) and no anastomotic leak was reported in the emergency group (0/7). TA was performed in 15 cases, 93% in an elective setting (14/15), and the anastomotic leak rate was 13.3% (2/15). In 20 cases, we performed elective STEA and no anastomotic leak was recorded. In 19 cases, it was impossible to perform anastomosis and we decided to create a definitive colostomy. CONCLUSION: Consistent with the literature data, our experience shows that, in selected cases, STSA and STEA are both safe and effective, with a lower anastomotic complication rate than TA.

Intracorporeal Anastomosis in Both Elective and Emergency Right Hemicolectomy: Our Experience.

PURPOSE: The aim of this study was to examine whether intracorporeal anastomosis (IA) after laparoscopic right hemicolectomy (LRH) is a safe procedure in both emergency and elective settings. METHODS: A retrospective review of all consecutive adult patients (age > 17 years) who underwent LRH from November 2014 to May 2018 at S. Andrea Hospital, La Spezia, was performed. The primary and secondary outcomes were the anastomotic leak rate and the operative time, respectively. Both IA and extracorporeal anastomosis (EA) were performed according to standardized techniques by the same team of experienced surgeons. Our findings were compared to literature data on recent studies comparing IA and EA during LRH. RESULTS: During the observation period, 167 patients underwent RH at our institution: IA was performed in 115. The mean age was 73.5 y. Thirty-three RH were performed in an emergency setting: 15 laparotomic procedures, 3 conversions from laparoscopic to open, 6 laparoscopic-assisted with EA, and 9 complete IA. The remaining 134 patients underwent elective RH: IA was performed in 106. The overall anastomotic leak rate in LHR IA was 2.6% (3/115), and no anastomotic leak was reported in the emergency group (0/9). The mean operative time was 180 min. In our experience, the operative time is related to the surgeon's experience and confidence with the technique, and not to the anastomosis technique per se. CONCLUSION: Consistent with the literature data, IA in LRH was associated with better outcomes than EA in both elective and emergency settings.

Particle-laden two-dimensional elastic turbulence.

The aggregation properties of heavy inertial particles in the elastic turbulence regime of an Oldroyd-B fluid with periodic Kolmogorov mean flow are investigated by means of extensive numerical simulations in two dimensions. Both the small- and large-scale features of the resulting inhomogeneous particle distribution are examined, focusing on their connection with the properties of the advecting viscoelastic flow. We find that particles preferentially accumulate on thin highly elastic propagating structures and that this effect is the largest for intermediate values of particle inertia. We provide a quantitative characterization of this phenomenon that allows to relate it to the accumulation of particles in filamentary highly strained flow regions producing clusters of correlation dimension close to 1. At larger scales, particles are found to undergo turbophoretic-like segregation. Indeed, our results indicate a close relationship between the profiles of particle density and fluid velocity fluctuations. The large-scale inhomogeneity of the particle distribution is interpreted in the framework of a model derived in the limit of small, but finite, particle inertia. The qualitative characteristics of different observables are, to a good extent, independent of the flow elasticity. When increased, the latter is found, however, to slightly reduce the globally averaged degree of turbophoretic unmixing.

International Summit on Laparoscopic Pancreatic Resection (ISLPR) "Coimbatore Summit Statements".

The International Summit on Laparoscopic Pancreatic Resection (ISLPR) was held in Coimbatore, India, on 7th and 8th of October 2016 and thirty international experts who regularly perform laparoscopic pancreatic resections participated in ISPLR from four continents, i.e., South and North America, Europe and Asia. Prior to ISLPR, the first conversation among the experts was made online on August 26th, 2016 and the structures of ISPLR were developed. The aims of ISPLR were; i) to identify indications and optimal case selection criteria for minimally invasive pancreatic resection (MIPR) in the setting of both benign and malignant diseases; ii) standardization of techniques to increase the safety of MIPR; iii) identification of common problems faced during MIPR and developing associated management strategies; iv) development of clinical protocols to allow early identification of complications and develop the accompanying management plan to minimize morbidity and mortality. As a process for interactive discussion, the experts were requested to complete an online questionnaire consisting of 65 questions about the various technical aspects of laparoscopic pancreatic resections. Two further web-based meetings were conducted prior to ISPLR. Through further discussion during ISPLR, we have created productive statements regarding the topics of Disease, Implementation, Patients, Techniques, and Instrumentations (DIPTI) and hereby publish them as "Coimbatore Summit Statements".

Precoagulation-assisted parenchyma-sparing laparoscopic liver surgery: rationale and surgical technique.

BACKGROUND: For the treatment of both primary and metastatic liver tumors, laparoscopic parenchyma-sparing surgery is advocated to reduce postoperative liver failure and facilitate reoperation in the case of recurrence. However, atypical and wedge resections are associated with a higher amount of intraoperative bleeding than are anatomical resections, and such bleeding is known to affect short- and long-term outcomes. Beyond the established role of radiofrequency and microwave ablation in the setting of inoperable liver tumors, the application of thermoablative energy along the plane of the liver surface to be transected results in a zone of coagulative necrosis, possibly minimizing bleeding of the cut liver surface during parenchymal transection. METHODS: From January 2013 to March 2016, a total of 20 selected patients underwent laparoscopic ultrasound-guided liver resection with thermoablative precoagulation of the transection line. RESULTS: During a period of 38 months, 50 laparoscopic thermoablative procedures were performed. Colorectal liver metastases were the most frequent diagnosis. Seventy-two percent of the nodules were removed using parenchymal transection with radiofrequency-precoagulation, while microwave-precoagulation was performed for 20 % of the resected nodules. The remaining 8 % of the nodules were treated by thermoablation alone. The hepatic pedicle was intermittently clamped in six patients. The mean blood loss was 290 mL, and four patients required perioperative transfusions. CONCLUSIONS: Precoagulation-assisted parenchyma-sparing laparoscopic liver surgery can get minimal blood loss during parenchymal transection and lower the need for perioperative transfusions, providing a nonquantifiable margin of oncological safety on the remaining liver. Additional results from larger series are advocated to confirm these preliminary data.

Laparoscopic Finney pyloroplasty in the emergency setting: first case report in the literature and technical challenges.

Pyloroplasty is currently reserved for emergencies (perforation, bleeding), but may occasionally be performed to treat benign gastric outlet obstruction (GOO). Historically, two techniques are available: the Mikulicz pyloroplasty, by which the pylorus is incised longitudinally and sutured vertically, and the Finney pyloroplasty, by which a U-shaped inverted incision is made in the second part of duodenum (D1-D2), followed by a side-to-side gastroduodenostomy. We report our experience in this single case of laparoscopic Finney pyloroplasty (LFP) performed in the emergency setting for a woman with a perforated duodenal ulcer and severe loss of tissue in D1-D2. Due to the presence of severely inflamed perforation edges and the risk of duodenal narrowing with subsequent GOO, Finney technique was favored over direct ulcer repair. The patient achieved a full postoperative recovery free of complications, with a dynamic oral contrast study demonstrating good gastric evacuation. Review of the current literature revealed no similar cases, as LFP has only been performed in the canine model. Although LFP requires a specific surgical skill-set, we believe it can be effective and feasible in cases of duodenal perforation with significant loss of mural substance.

Laparoscopic Inferior Mesenteric Artery Peeling: An Alternative to High or Low Vascular Ligation for Sigmoid Colon Cancer Resection.

BACKGROUND: In sigmoid cancer, both inferior mesenteric artery high or low ligations are accepted for curative purposes. Since inferior mesenteric artery ligation could compromise blood flow to the anastomosis, potentially increasing anastomotic leakage onset, real oncological benefits and possible disadvantages related to vascular transection level are still on debate. We introduce totally laparoscopic inferior mesenteric artery peeling technique to release from the concept of lymph nodal harvesting linked to arterial transection level. METHODS: Over a period of 24 months, 31 patients presenting with sigmoid cancer were submitted to laparoscopic sigmoidectomy associated with inferior mesenteric artery peeling. Data on intraoperative and postoperative outcomes have been prospectively collected. RESULTS: Mean operative time was 180 min (range 110-330 min); mean intraoperative blood loss was 60 ml (range 30-150 ml), and mean postoperative hospitalization was 6.2 days (range 4-11 days). Mean number of lymph node harvested was 16.7 (range 12-28). CONCLUSIONS: Given a proper selection of patients, laparoscopic sigmoidectomy comprehensive of sub-adventitial IMA skeletonization from its aortic origin could provide good oncological outcomes and recanalization rate. Further data are advocated to confirm these preliminary results.