Renal Flow Research Articles

Perioperative Doppler measurements of renal perfusion are associated with acute kidney injury in patients undergoing cardiac surgery

Acute kidney injury (AKI) is a frequent and severe complication in cardiac surgery. Normal renal function is dependent on adequate renal perfusion, which may be altered in the perioperative period. Renal perfusion can be assessed with Doppler measurement. We aimed to determine the association between Doppler measurements of renal perfusion and the development of AKI. This was a prospective, observational study of 100 patients with ≥ one risk factor for postoperative AKI undergoing open-heart surgery. Doppler ultrasound examinations were performed before surgery and on the first and fourth postoperative day. AKI was defined according to the KDIGO criteria and subdivided into mild (KDIGO stage 1) and severe AKI (KDIGO stage 2 + 3). Thirty-three patients developed AKI, 25 developed mild and eight developed severe AKI. Abnormal renal venous flow pattern on the first postoperative day was significantly associated with the development of severe AKI (OR 8.54 (95% CI 1.01; 72.2), P = 0.046), as were portal pulsatility fraction (OR 1.07 (95% CI 1.02; 1.13), P = 0.005). Point-of-care Doppler ultrasound measurements of renal perfusion are associated with the development of AKI after cardiac surgery. Renal and portal Doppler ultrasonography can be used to identify patients at high risk or very low risk of AKI after cardiac surgery.

Hydroxyl Ethyl Starch (HES) Preserves Intrarenal Microcirculatory Perfusion Shown by Contrast-Enhanced Ultrasound (Ceus), and Renal Function in a Severe Hemodilution Model in Pigs.

Acute normovolemic hemodilution (ANH) is associated with low oxygen carrying capacity of blood and purposed to cause renal injury in perioperative setting. It is best accomplished in a perioperative setting by a colloid such as hydroxyl ethyl starch (HES) due its capacity to fill the vascular compartment and maintain colloidal pressure. However, alterations of intra renal microvascular perfusion, flow and its effects on renal function and damage during ANH has not been sufficiently clarified. Based on the extensive use of HES in the perioperative setting we tested the hypothesis that the use of HES during ANH is able to perfuse the kidney microcirculation adequately without causing renal dysfunction and injury in pigs. Hemodilution (n = 8) was performed by stepwise replacing blood with HES to hematocrit (Hct) levels of 20% (T1), 15% (T2), and 10% (T3). Seven control animals were investigated. Systemic and renal hemodynamics were monitored. Renal microcirculatory perfusion was visualized and quantified using contrast-enhanced ultrasound (CEUS) and laser speckle imaging (LSI). In addition, sublingual microcirculation was measured by handheld vital microscopy (HVM). Intrarenal mean transit time of ultrasound contrast agent (IRMTT-CEUS) was reduced in the renal cortex at Hct 10% in comparison to control at T3 (1.4 ± 0.6 vs. 2.2 ± 0.7 seconds, respectively, P < 0.05). Although renal function was preserved, the serum neutrophil gelatinase-associated lipocalin (NGAL) levels was higher at Hct 10% (0.033 ± 0.004 pg/μg protein) in comparison to control at T3 (0.021 ± 0.002 pg/μg protein. A mild correlation between CO and IRMTT (renal RBC velocity) (r -0.53; P = 0.001) and CO and NGAL levels (r 0.66; P = 0.001) was also found. Our results show that HES induced ANH is associated with a preserved intra renal blood volume, perfusion, and function in the clinical range of Hct (<15%). However, at severely low Hct (10%) ANH was associated with renal injury as indicated by increased NGAL levels. Changes in renal microcirculatory flow (CEUS and LSI) followed those seen in the sublingual microcirculation measured with HVM.

Renal agenesis

Renal agenesis

Renal hemodynamics across the adult lifespan: Relevance of flow pulsatility to chronic kidney disease.

Elevated renal flow pulsatility may contribute to the pathogenesis of chronic kidney disease (CKD). The purpose of this study was to investigate the associations among age, renal flow pulsatility, and CKD biomarkers in non-CKD adults and CKD patients. Non-CKD adults (n=415) and CKD patients (n=136) aged between 22 and 83years underwent the renal blood flow measurement using duplex ultrasonography. Pulsatility index (PI) and resistive index (RI) were calculated to assess renal flow pulsatility. The CKD biomarkers such as urinary liver-type fatty acid-binding protein (L-FABP) and serum fibroblast growth factor 23 (FGF23) were measured from each participant. Aortic hemodynamic parameters were measured by applanation tonometry. In non-CKD adults, advancing age was associated with elevations of renal PI and RI which slowly increased during middle-aged (PI: β=0.14, RI: β=0.17) and accelerated in older adults (PI: β=0.34, RI: β=0.33). In CKD patients, age-related increases in renal PI and RI were observed only in the middle age group (PI: β=0.23, RI: β=0.26). Multivariate analysis demonstrated that renal PI and RI were independently associated with CKD biomarkers, including urinary L-FABP and serum FGF23, and aortic pulse pressure. Advancing age is associated with a progressive elevation of renal flow pulsatility which manifests during middle age and accelerates in later life. Moreover, elevated renal flow pulsatility is associated with the presence of CKD in each age group and also with biomarker levels that reflect CKD progression.

Magnetic resonance imaging assessment of renal flow distribution patterns during exvivo normothermic machine perfusion in porcine and human kidneys.

SummaryAcceptance criteria of deceased donor organs have gradually been extended toward suboptimal quality, posing an urgent need for more objective pre‐transplant organ assessment. Ex vivo normothermic machine perfusion (NMP) combined with magnetic resonance imaging (MRI) could assist clinicians in deciding whether a donor kidney is suitable for transplantation. Aim of this study was to characterize the regional distribution of perfusate flow during NMP, to better understand how ex vivo kidney assessment protocols should eventually be designed. Nine porcine and 4 human discarded kidneys underwent 3 h of NMP in an MRI‐compatible perfusion setup. Arterial spin labeling scans were performed every 15 min, resulting in perfusion‐weighted images that visualize intrarenal flow distribution. At the start of NMP, all kidneys were mainly centrally perfused and it took time for the outer cortex to reach its physiological dominant perfusion state. Calculated corticomedullary ratios based on the perfusion maps reached a physiological range comparable to in vivo observations, but only after 1 to 2 h after the start of NMP. Before that, the functionally important renal cortex appeared severely underperfused. Our findings suggest that early functional NMP quality assessment markers may not reflect actual physiology and should therefore be interpreted with caution.

Independent relationships between renal mechanisms and systemic flow, but not resistance to flow in primary hypertension in Africa.

Whether renal mechanisms of hypertension primarily translate into increases in systemic vascular resistance (SVR) in all populations is uncertain. We determined whether renal mechanisms associate with either increases in SVR (and impedance to flow) or systemic flow in a community of African ancestry. In a South African community sampled across the full adult age range (n = 546), we assessed stroke volume (SV), peak aortic flow (Q), SVR, characteristic impedance (Zc) and total arterial compliance (TAC) from velocity and diameter measurements in the outflow tract (echocardiography) and central arterial pressures. Renal changes were determined from creatinine clearance (glomerular filtration rate, GFR) and fractional Na+ excretion (FeNa+) (derived from 24-h urine collections). Independent of confounders (including MAP and pressures generated by the product of Q and Zc), SV (and hence cardiac output) (P < 0.0001) and Q (P < 0.01), but not SVR, Zc or TAC (P = 0.09-0.20) were independently associated with decreases in both GFR (index of nephron number) and FeNa+. Through an interactive effect (P < 0.0001), the impact of GFR on SV or Q was strongly determined by FeNa+ and vice versa. The relationship between the GFR-FeNa+ interaction and either SV or Q was noted in those above or below 50 years of age, although neither GFR, FeNa+ nor the interaction were independently associated with SVR, Zc or TAC at any age. Across the full adult lifespan, in groups of African ancestry, renal mechanisms of hypertension translate into increases in systemic flow rather than into resistance or impedance to flow.

Angiotensin 1-7 receptor blockade attenuates renal clearance and urine flow in hypertensive rats

Angiotensin 1-7 receptor blockade attenuates renal clearance and urine flow in hypertensive rats

Acute effects of dapagliflozin on renal oxygenation and perfusion in type 1 diabetes with albuminuria: A randomised, double-blind, placebo-controlled crossover trial.

BackgroundInhibitors of the sodium-glucose cotransporter 2 (SGLT2) slow the progression of diabetic kidney disease, possibly by reducing the proximal tubule transport workload with subsequent improvement of renal oxygenation. We aimed to test this hypothesis in individuals with type 1 diabetes and albuminuria.MethodsA randomised, double-blind, placebo-controlled, crossover trial with a single 50 mg dose of the SGLT2 inhibitor dapagliflozin and placebo in random order, separated by a two-week washout period. Magnetic resonance imaging (MRI) was used to assess renal R2* (a low value corresponds to a high tissue oxygenation), renal perfusion (arterial spin labelling) and renal artery flow (phase contrast imaging) at baseline, three- and six hours from tablet ingestion. Exploratory outcomes, including baroreflex sensitivity, peripheral blood oxygen saturation, peripheral blood mononuclear cell mitochondrial oxygen consumption rate, and biomarkers of inflammation were evaluated at baseline and 12 h from medication. The study is registered in the EU Clinical Trials Register (EudraCT 2019–004,557–92), on ClinicalTrials.gov (NCT04193566), and is completed.FindingsBetween February 3, 2020 and October 23, 2020, 31 individuals were screened, and 19 eligible individuals were randomised. Three dropped out before receiving any of the interventions and one dropped out after receiving only placebo. We included 15 individuals (33% female) in the per-protocol analysis with a mean age of 58 (SD 14) years, median urinary albumin creatinine ratio of 46 [IQR 21–58] mg/g and an eGFR of 73 (32) ml/min/1·73m2. The mean changes in renal cortical R2* from baseline to six hours were for dapagliflozin -1·1 (SD 0·7) s−1 and for placebo +1·3 (0·7) s−1, resulting in a difference between interventions of -2·3 s−1 [95% CI -4·0 to -0·6]; p = 0·012. No between-intervention differences were found in any other MRI outcomes, physiological parameters or exploratory outcomes. There were no adverse events.InterpretationA single dose of 50 mg dapagliflozin acutely improved renal cortical R2* without changing renal perfusion or blood flow. This suggests improved renal cortical oxygenation due to a reduced tubular transport workload in the proximal tubules. Such improved oxygenation may in part explain the long-term beneficial renal effects seen with SGLT2 inhibitors, but it remains to be determined whether the observed effects can be achieved with lower doses, with chronic treatment and if they occur in type 2 diabetes as well.

318-OR: Dapagliflozin Acutely Improves Renal Cortical Oxygenation in Individuals with Type 1 Diabetes and Albuminuria

Objective: Inhibitors of the sodium-glucose cotransporter 2 slow the progression of diabetic kidney disease, possibly by reducing the proximal tubule transport workload with subsequent improvement of renal oxygenation. We aimed to test this hypothesis in individuals with type 1 diabetes and albuminuria. Research Design and Methods: A randomized, double-blinded, crossover study with a single dose of 50 mg dapagliflozin and placebo separated by a two-week washout period. Magnetic resonance imaging (MRI) was used to assess renal tissue oxygenation (R2*), renal perfusion (arterial spin labelling) and renal artery flow (phase contrast imaging) at baseline and three and six hours from intervention. Exploratory outcomes, including baroreflex sensitivity, peripheral blood oxygen saturation and peripheral blood mononuclear mitochondrial oxygen consumption rate, were evaluated at baseline and 12 hours from intervention. Results: We included 15 individuals (33% females) with a mean (±SD) age 58±14 years, median [Q1;Q3] urinary albumin creatinine ratio of 46 [21;58] mg/g and eGFR of 73±32 ml/min/1.73m2. The mean changes (±SE) in renal cortical R2* from baseline to six hours were for dapagliflozin -1.3±0.7 s-1 and for placebo +1.4±0.7 s-1 respectively, resulting in a difference between interventions of -2.6 s-1 (95% CI, -4.5 to -0.7, p=0.001). No between-intervention differences were found in other MRI outcomes, physiological parameters or exploratory outcomes. Conclusions: Dapagliflozin improved renal cortical R2* without changing renal perfusion and blood flow. This suggests an improved renal cortical oxygenation due to reduced tubular transport work in the proximal tubules. Disclosure J. Laursen: None. P. Groop: Advisory Panel; Self; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Merck Sharp &amp; Dohme Corp., Speaker’s Bureau; Self; Boehringer Ingelheim International GmbH, Mundipharma International. M. Frimodt-moeller: None. U. B. Andersen: Other Relationship; Self; Bayer AG. P. Rossing: Advisory Panel; Self; Astellas Pharma Inc., AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Gilead Sciences, Inc., Merck KGaA, Merck Sharp &amp; Dohme Corp., Novo Nordisk A/S, Sanofi, Vifor Pharma Management Ltd. N. S. Heinrich: Stock/Shareholder; Self; Akebia Therapeutics, Inc., Novo Nordisk A/S. J. Melo: None. B. Haddock: None. I. B. Rasmussen: None. F. Safavimanesh: None. C. S. Hansen: None. J. Størling: None. H. B. W. Larsson: None.

Patient-specific computational fluid dynamic simulation for assessing hemodynamic changes following branched endovascular aneurysm repair: A pilot study

Abstract Objective This pilot study assessed the hypothesis that patient-specific computational fluid dynamic (CFD) modelling can detect aortic branch hemodynamic changes following branched endovascular aneurysm repair (bEVAR). Methods Patients who underwent bEVAR with the Jotec E-xtra Design for thoracoabdominal aortic aneurysms were retrospectively selected. Using open-source SimVascular software, pre- and post-operative aortic finite element volume meshes were constructed from CT imaging. Pulsatile in-flow conditions were derived and adjusted for patient-specific clinical variables. Outlet boundary conditions consisted of Windkessel models approximated from physiologic flow splits. Rigid wall flow simulations were then performed on pre- and post-operative models with equivalent boundary conditions. Computations were performed with an incompressible Navier-Stokes flow solver on a 72-core cluster. Results Pre- and post-operative flow simulations were performed on 10 patients undergoing bEVAR with a total of 40 target vessels (10 celiac, 20 superior mesenteric, 20 renal stents). Compared to pre-operative values, bEVAR was associated with a decrease in peak renal artery pressure (116.8 ± 11.5 vs 112.8 ± 11.6 mmHg, p&amp;lt;.001) and flow rate (13.7 ± 2.3 vs 12.9 ± 2.4 ml/s, p&amp;lt;.001). No post-operative differences were observed in pressure or flow rates in the celiac or mesenteric arteries (p=.10-.55). Representative perfusion waveforms from a single patient are shown in Figure 1. bEVAR resulted in a significant increase in aortic (1.4 ± 0.5 vs 4.3 ± 2.9 dynes/cm2, p=.009) and renal artery (24.3 ± 7.1 vs 35.4 ± 12.4 dynes/cm2, p=.23) wall shear stress; however, these values remained within the physiologic range. In certain graft configurations, 3D visualization of blood flow streamlines revealed areas of turbulent flow at the origin of external branches which were associated with decreased target artery perfusion (Figure 2). Conclusion Changes in para-visceral aortic geometry after bEVAR is associated with a decrease in computationally estimated renal perfusion, without significant changes to celiac or mesenteric hemodynamics. Further CFD simulation-based studies are needed to assess whether changes in branch configuration or hemodynamics after bEVAR can predict loss of branch patency.

Contrast-enhanced ultrasound assessed renal microvascular perfusion may predict postoperative renal complications following colorectal surgery.

Colorectal surgery is associated with an above-average mortality rate of approximately 15%. During surgery, maintenance of vital organ perfusion is essential in order to reduce postoperative mortality and morbidity, with renal perfusion of particular importance. Oesophageal Doppler monitors (ODM) are commonly used to try and provide accurate measures of fluid depletion during surgery; however, it is unclear to what extent they reflect organ perfusion. In addition, it is not known whether macro- and/ or microvascular perfusion indices are associated with renal complications following colorectal surgery. Thirty-two participants scheduled for colorectal surgery had three measures of macro- and microvascular renal blood flow via contrast enhanced ultrasound (CEUS), and simultaneous measures of cardiac output indices via ODM: (i) pre-operatively; (ii) intra-operatively at the mid-point of operation, and (iii) after the conclusion of surgery. The Postoperative Morbidity Survey (POMS) was used to assess postoperative complications. Intra-operatively, there was a significant correlation between renal microvascular flow (RT) and renal macrovascular flow (TTI) (ρ=0.52; p=0.003). Intra-operative TTI, but not RT, was associated with cardiac index (ρ=-0.50; p=0.0003). Intra-operative RT predicted increases in renal complications (OR 1.46; 95% CI 1.03-2.09) with good discrimination (C-statistic, 0.85). Complications were not predicted by TTI or ODM-derived indices. There was no relationship between RT and TTI before or after surgery. ODM measures of haemodynamic status do not correlate with renal microvascular blood flow, and as such are likely not suitable to determine vital organ perfusion. Only CEUS-derived measures of microvascular perfusion were predictive of postoperative renal complications.

High Salt Diet Increases Renal Oxygen Consumption in Sprague‐Dawley Rats

The physiological relationships between kidney O2 delivery and consumption and metabolism have been studied only under conditions of anesthesia and stressful surgical procedures. We report here techniques developed in our laboratory enabling determination of kidney O2 utilization over many days in instrumented unanesthetized rats in which the effects of a high salt diet were determined in normal Sprague Dawley (SD) rats. Male SD rats (10 weeks of age) fed a 0.4% NaCl diet were instrumented with a left renal artery flow probe (Transonic) for continuous (24 hr/day) measurement of renal blood flow (RBF). An indwelling intra-renal vein catheter (MRE 025) was inserted through the femoral vein and tip fixed close to the renal pelvis. An aortic catheter inserted though the femoral artery was implanted to sample blood and continuously (24 hr/day) measure arterial blood pressure (BP). Catheters and flow probe cables which exited from the neck were attached to a custom designed swivel and a servo-controlled circular cage system (BASi cage) enabling the rat to move freely throughout the study. Following 7 days of recovery from surgery, continuous monitoring of RBF and BP began and continued throughout the study. Following a 3 day control period with rats fed a 0.4% NaCl diet, renal venous and arterial blood were samples (250 ul) and blood gas was measured immediately by a radiometer (ABL800 FLEX). The diet was switch to 4% NaCl and blood sampling was performed at days 7, 14 and 21 of the high salt diet. O2 content, O2 consumption, and O2 extraction were determined as: O2 content (mL/dL): 0.31 × Hemoglobin (Hb) (g/dL) × HbO­2 (%) + 0.003 × PaO2 (mmHg). O2 consumption (ml/min): RBF (ml/min) × (arterial-renal venous O2 content difference). O2 extraction (% of arterial supply): 1-(renal venous O2 content/arterial O2 content) × 100. Daily average mean arterial pressure (MAP) increased moderately soon after switching to the 4% NaCl diet from 113 ± 2 to 120 ± 2 mmHg by day 3 (p=0.03, n=9) and remain elevated at this level throughout the study (120 ± 3 mmHg at day 13). Renal blood flow also rose soon after switching to the 4% salt diet from 9.4 ± 0.8 to 10.3 ± 0.8 ml/min during day 2 (p=0.03, n=9) . Thereafter, it also remained elevated throughout the study (10.7 ± 0.8 ml/min at day 13). Changes in O2 consumption occurred more gradually increasing from 0.21 ± 0.04 and rising to 0.27 ± 0.03 (ml/min) at day 14 of 4% salt diet (p=0.02, n=5). The calculated O2 extraction ratio remained unchanged ranging from 12.1 ± 0.1 (%) to 12.8 ± 0.1 (%) (p=0.48, n=5) throughout the study. It appears that in normal SD rats, the increased tubular metabolic work associated with a high salt diet is initially accommodated by increased perfusion (RBF) and a gradual increase of O2 consumption while extraction remains unchanged for a two-week period.

Acute Kidney Injury in a Patient with Trisomy 21.

1. Hannah S. Kim, MD* 2. Francesca Costigliolo, MD† 3. Serena Bagnasco, MD† 4. Jeffrey Fadrowski, MD, MHS* 5. Rebecca L. Ruebner, MD, MSCE* 1. *Division of Pediatric Nephrology and 2. †Division of Pathology, Johns Hopkins University, Baltimore, MD A 5-year-old former 34-week girl with trisomy 21, hypothyroidism, and obstructive sleep apnea presents to the emergency department with a chief complaint of fever. She initially presented to her pediatrician 3 weeks earlier with sore throat and was diagnosed as having group A streptococcal pharyngitis. She completed 10 days of amoxicillin with resolution of sore throat. Now for the past 3 days she has had fever, chest pain, decreased enteral intake, and emesis. Review of systems is negative for diarrhea, gross hematuria, dysuria, polyuria, polydipsia, edema, weight loss, rash, arthralgia, arthritis, oral ulcers, epistaxis, and hemoptysis. She has had normal growth. She takes levothyroxine and took several doses of ibuprofen for fever over the past several weeks. There is no family history of kidney disease. She had no recent travel or sick contacts. On physical examination her weight is 45.2 lb (20.5 kg) (65th percentile); height, 46.1 in (117 cm) (62% percentile); temperature, 100.8°F (38.2°C); heart rate, 110 beats/min; respiratory rate, 24 breaths/min; oxygen saturation, 100% on room air; and blood pressure, 92/42 mm Hg (systolic 31st and diastolic 9th percentiles for age and sex). There is no pharyngeal injection or exudate. She appears well-hydrated, including moist mucous membranes. Lungs are clear to auscultation. Her abdomen is soft, nontender, and nondistended. There is no edema, and she has brisk capillary refill. She has no rash or joint swelling, erythema, or warmth. Laboratory evaluation includes a white blood cell count of 15,310/µL (15.31×109/L) with 83.6% neutrophils and 0.8% bands; hemoglobin …

Renal interventions in the management of hypertension.

In the present comprehensive review, we describe the pathophysiology, indications, and evidence for both renal artery stenting and renal artery denervation. We also discuss the procedural techniques, risks, benefits, and future directions of renal intervention in the management of hypertension (HTN). Hemodynamic confirmation of lesion severity in severe renal artery stenosis is a resting or hyperemic translesional systolic gradient >20, resting or hyperemic mean translesional gradient >10 and/or renal fractional flow reserve <0.8 are considered severe. Knowing that correct stent size was used is the best predictor of restenosis, intravascular ultrasound is effective and well tolerated for stent sizing. The main categories of renal denervation: radiofrequency ablation, ultrasound, chemical ablation, and brachytherapy have shown impressive outcomes in treating resistant HTN. Over the past decade, several studies have shown the safety and benefit of catheter-based renal interventions in managing HTN. Renal artery stenting and renal artery denervation are the leading alternative invasive treatment employed in managing HTN.

Three-dimensional Virtual Models’ Assistance During Minimally Invasive Partial Nephrectomy Minimizes the Impairment of Kidney Function

Three-dimensional virtual models (3DVMs) are nowadays under scrutiny to improve partial nephrectomy (PN) outcomes. This report aims to analyze their impact on renal function preservation after minimally invasive PN. A total of 100 patients treated with minimally invasive PN with contrast-enhanced computed tomography from which a 3DVM was obtained, and having undergone baseline and 3rd month postoperative renal scans were prospectively enrolled and compared with a control group of 251 patients without 3DVMs. Weighted differential of pre- and postoperative renal scan-based effective renal plasmatic flow (b-WD ERPF) was calculated, according to the availability of 3DVMs and PADUA risk category. Multivariable logistic regression (MLR) models predicting a significant loss of renal function (LORF; ERPF drop >20%) were performed, overall and according to PADUA risk categories. The b-WD ERPF of the 3DVM group showed significantly lower LORF (–10%) than that of the control group (–19.6%, p = 0.02). In MLR, the availability of a 3DVM was found to be the only protective factor against a significant LORF (odds ratio [OR] = 0.3, p = 0.002). Moreover, after stratification as per tumor surgical complexity, this protective role was observed in both PADUA 8–9 and ≥10 category risk patients (OR = 0.3, p = 0.03 and OR = 0.1, p = 0.01). Patient summaryThe drop in operated kidney function was significantly lower in surgeries assisted by three-dimensional virtual models (3VDMs), indicating that the availability of a 3VDM is the only protective factor against a significant functional damage.

Pressure gradient measurement to verify hemodynamic results of the chimney endovascular aortic repair (chEVAR) technique.

PurposeThe use of the pressure gradient measurements to assess the renal artery flow hemodynamics after chimney endovascular aortic repair (chEVAR).MethodsThe study was a prospective analysis of 37 chEVAR procedures performend in 24 patients with perirenal aortic aneurysm. In all patients the measurement of: distal renal artery pressure (Pd), aortic pressure (Pa), Pd/Pa ratio (Pd/Pa) and mean gradient (MG) between the aorta and the distal renal artery were performed. Measurements were taken with 0.014 inch pressure wire catheter before and after the chEVAR procedure. MG greater than 9 mmHg and Pd/Pa ratio below 0.90 were considered as the measures of a significant decrease in distal pressure that limited flow in renal arteries. The 6 month follow-up computed tomographic angiography (CTA) was performed in all patients to diagnose potential endoleak presence and to verify the patency of the chimney stent-grafts.ResultsAll procedures were successful, and no periprocedural complications were observed in any of the patients. The mean gradient values before and after the chimney implantation did not change significantly (6,2±2,0 mmHg and 6,8±2,2 mmHg, respectively). Similarly, no significant change in Pd/Pa values was noted with the value of 0.9 observed both before and after the procedure. All chimney stents were patent on the control CTA. Type Ia endoleak was found in 4 (10.8%) patients.ConclusionsThe application of the described technique seems to be a safe method which allows a direct measurement of renal artery flow hemodynamics before and after chimney implantation during the chEVAR technique. The use of covered balloon expandable stents, ensures the proper blood flow in the renal arteries during the chEVAR technique.

Posterior nutcracker syndrome: a case\xa0report

BackgroundPosterior nutcracker syndrome is defined by the compression of the left renal vein between the abdominal aorta and a lumbar vertebral body. It can be clinically manifest with intermittent hematuria, gonadal or spermatic reflux resulting in varicocele. Ultrasound is the first-line imaging which require more accurate study with contrast-enhanced computed tomography. Management can be conservative in younger patients with mild hematuria due to the high spontaneous remission rate and invasive with open surgical and endovascular interventions. We describe a very rare case with compression of the left renal vein due to an osteophyte of the spine.Case presentationA 62-year-old Caucasic male came to our radiology department for chronic hepatitis B virus (HBV)-related liver disease follow-up and mild scrotal pain. The ultrasound examination revealed a compression of the left retro-aortic renal vein in the aorto-vertebral space caused by an osteophyte. Duplex Doppler ultrasound revealed flow congestion in the left renal vein and renal failure; power Doppler ultrasound showed left varicocele.ConclusionsDoppler ultrasound is the first-line imaging and allows the detection of all the typical signs of posterior nutcracker: left renal vein stenosis, flow congestion and renal failure. Nutcracker syndrome should be suspected in older patients with left varicocele associated with hematuria. Failure to diagnose and treat these patients could have serious consequences for their health.

Preimplantation Histological Score Associates with 6-Month GFR in Recipients of Perfused, Older Kidney Grafts: Results from a Pilot Study

Background: Biopsy-guided selection of older kidneys safely expands the organ pool, and pretransplant perfusion improves the preservation of these fragile organs. Herein, we studied morphofunctional variables associated with graft outcomes in perfused, histologically evaluated older kidneys. Methods: This single-center prospective cohort pilot study evaluated the relationships between preimplantation histologic scores and renal perfusion parameters during hypothermic, pulsatile, machine perfusion (MP) and assessed whether these morphofunctional parameters associated with GFR (iohexol plasma clearance) at 6 months after transplantation in 20 consecutive consenting recipients of a biopsy-guided single or dual kidney transplant from >60-year-old deceased donors. Results: The donor and recipient age was 70.4 ± 6.5 and 63.6 ± 7.9 years (p = 0.005), respectively. The kidney donor profile index (KDPI) was 93.3 ± 8.4% (>80% in 19 cases), histologic score 4.4 ± 1.4, and median (IQR) cold ischemia time 19.8 (17.8–22.8 h; >24 h in 5 cases). The 6-month GFR was 41.2 (34.9–55.7) mL/min. Vascular resistances positively correlated with global histologic score (p = 0.018) at MP start and then decreased from 0.88 ± 0.43 to 0.36 ± 0.13 mm Hg/mL/min (p < 0.001) in parallel with a three-fold renal flow increase from 24.0 ± 14.7 to 74.7 ± 31.8 mL/min (p < 0.001). Consistently, vascular resistance reductions positively correlated with global histologic score (p = 0.009, r = −0.429). Unlike KDPI or vascular resistances, histologic score was independently associated with 6-month GFR (beta standardized coefficient: −0.894, p = 0.005). Conclusions: MP safely improves graft perfusion, particularly in kidneys with severe histologic changes that would not be considered for transplantation because of high KDPI. The preimplantation histologic score associates with the functional recovery of older kidneys even in the context of a standardized program of pulsatile perfusion.

Focus on renal blood flow in mechanically ventilated patients with SARS-CoV-2: a prospective pilot study.

Mechanically ventilated patients with ARDS due to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) seem particularly susceptible to AKI. Our hypothesis was that the renal blood flow could be more compromised in SARS-CoV-2 patients than in patients with “classical” ARDS. We compared the renal resistivity index (RRI) and the renal venous flow (RVF) in ARDS patients with SARS-CoV-2 and in ARDS patients due to other etiologies. Prospective, observational pilot study performed on 30 mechanically ventilated patients (15 with SARS-COV-2 ARDS and 15 with ARDS). Mechanical ventilation settings included constant-flow controlled ventilation, a tidal volume of 6 ml/kg of ideal body weight and the PEEP level titrated to the lowest driving pressure. Ultrasound Doppler measurements of RRI and RVF pattern were performed in each patient. Patients with SARS-COV-2 ARDS had higher RRI than patients with ARDS (0.71[0.67–0.78] vs 0.64[0.60–0.74], p = 0.04). RVF was not-continuous in 9/15 patients (71%) in the SARS-COV-2 ARDS group and in and 5/15 (33%) in the ARDS group (p = 0.27). A linear correlation was found between PEEP and RRI in patients with SARS-COV-2 ARDS (r2 = 0.31; p = 0.03) but not in patients with ARDS. Occurrence of AKI was 53% in patients with SARS-COV-2 ARDS and 33% in patients with ARDS (p = 0.46). We found a more pronounced impairment in renal blood flow in mechanically ventilated patients with SARS-COV-2 ARDS, compared with patients with “classical” ARDS.Supplementary InformationThe online version of this article (10.1007/s10877-020-00633-5) contains supplementary material, which is available to authorized users.

Patient-specific computational flow modelling for assessing hemodynamic changes following fenestrated endovascular aneurysm repair

ObjectiveThis study aimed to develop an accessible patient-specific computational flow modelling pipeline for evaluating the hemodynamic performance of fenestrated endovascular aneurysm repair (fEVAR), with the hypothesis that computational flow modelling can detect aortic branch hemodynamic changes associated with fEVAR graft implantation. MethodsPatients who underwent fEVAR for juxtarenal aortic aneurysms with the Cook ZFEN were retrospectively selected. Using open-source SimVascular software, preoperative and postoperative visceral aortic anatomy was manually segmented from computed tomography angiograms. Three-dimensional geometric models were then discretized into tetrahedral finite element meshes. Patient-specific pulsatile in-flow conditions were derived from known supraceliac aortic flow waveforms and adjusted for patient body surface area, average resting heart rate, and blood pressure. Outlet boundary conditions consisted of three-element Windkessel models approximated from physiologic flow splits. Rigid wall flow simulations were then performed on preoperative and postoperative models with the same inflow and outflow conditions. We used SimVascular's incompressible Navier-Stokes solver to perform blood flow simulations on a cluster using 72 cores. ResultsPreoperative and postoperative flow simulations were performed for 10 patients undergoing fEVAR with a total of 30 target vessels (20 renal stents, 10 mesenteric scallops). Postoperative models required a higher mean number of mesh elements to reach mesh convergence (3.2 ± 1.8 × 106 vs 2.6 ± 1.1 × 106; P = .005) with a longer mean computational time (10.3 ± 6.3 hours vs 7.8 ± 3.5 hours; P = .04) compared with preoperative models. fEVAR was associated with small but statistically significant increases in mean peak proximal aortic arterial pressure (140.3 ± 11.0 mm Hg vs 136.9 ± 8.7 mm Hg; P = .02) and peak renal artery pressure (131.6 ± 14.8 mm Hg vs 128.9 ± 11.8 mm Hg; P = .04) compared with preoperative simulations. No differences were observed in peak pressure in the celiac, superior mesenteric, or distal aortic arteries (P = .17-.96). When measuring blood flow, the only observed difference was an increase in peak renal flow rate after fEVAR (17.5 ± 3.8 mL/s vs 16.9 ± 3.5 mL/s; P = .04). fEVAR was not associated with changes in the mean pressure or the mean flow rate in the celiac, superior mesenteric, or renal arteries (P = .06-.98). Stenting of the renal arteries did not induce significant changes time-averaged wall shear stress in the proximal renal artery (23.4 ± 8.1 dynes/cm2 vs 23.2 ± 8.4 dynes/cm2; P = .98) or distal renal artery (32.7 ± 13.9 dynes/cm2 vs 29.6 ± 11.8 dynes/cm2; P = .23). In addition, computational visualization of cross-sectional velocity profiles revealed low flow disturbances associated with protrusion of renal graft fabric into the aortic lumen. ConclusionsIn a pilot study involving a selective cohort of patients who underwent uncomplicated fEVAR, patient-specific flow modelling was a feasible method for assessing the hemodynamic performance of various two-vessel fenestrated device configurations and revealed subtle differences in computationally derived peak branch pressure and blood flow rates. Structural changes in aortic flow geometry after fEVAR do not seem to affect computationally estimated renovisceral branch perfusion or wall shear stress adversely. Additional studies with invasive angiography or phase contrast magnetic resonance imaging are required to clinically validate these findings. (JVS–Vascular Science 2021;2:53-69.) Clinical RelevanceUsing a computational flow modelling for assessing the hemodynamic performance of fenestrated endovascular aneurysm repair (fEVAR), this real-world, patient-specific study included 10 participants and found that structural changes in aortic flow geometry after fEVAR did not seem to adversely impact estimated renal or visceral branch perfusion metrics (eg, peak and mean arterial pressure and flow rates) or wall shear stress. These findings overall support the ongoing clinical use of commercially available fEVAR devices for repair of juxtarenal aortic aneurysms, and provides a computational framework for future evaluation of fEVAR configurations in a preoperative or postoperative settings.