Influence of angiotensin II and telmisartan on in vivo high-resolution renal arterial impedance in rats.

Angiotensin II (ANGII) is known to play an important role in regulating renal hemodynamics. We sought to quantify this effect in an in vivo rat model with high-resolution renal arterial (RA) impedance. This study examines the effects of ANGII and its type 1 receptor blocker, telmisartan (TELM), on RA impedance. In baroreflex deactivated rats, we measured RA pressure (Pr) and blood flow (Fr) during random ventricular pacing to induce pressure fluctuation at three different mean Pr (60, 80, and 100 mmHg). We then estimated RA impedance as the transfer function from Fr to Pr. The RA impedance was found to align with a three-element Windkessel model consisting of proximal (Rp) and distal (Rd) resistance and compliance (C). Our study showed Rd reflected the composite characteristics of afferent and efferent arterioles. Rd increased with increasing Pr under the baseline condition with a slope of 1.03 ± 0.21 (× 10-1) min·mL-1. ANGII significantly increased the slope by 0.72 ± 0.29 (× 10-1) min·mL-1 (P < 0.05) without affecting the intercept. TELM significantly reduced the intercept by 34.49 ± 4.86 (× 10-1) mmHg·min·mL-1 (P < 0.001) from the baseline value of 37.93 ± 13.36 (× 10-1) mmHg·min·mL-1, whereas it did not affect the slope. In contrast, Rp was less sensitive than Rd to ANGII or TELM, suggesting Rp may represent the characteristics of elastic large arteries. Our findings provide valuable insights into the influence of ANGII on the dynamics of the renal vasculature.

Impact of positive end-expiratory pressure on renal resistive index in mechanical ventilated patients.

PURPOSE: Growing evidence shows the complex interaction between lung and kidney in critically ill patients. The renal resistive index (RRI) is a bedside measurement of the resistance of the renal blood flow and it is correlated with kidney injury. The positive end-expiratory pressure (PEEP) level could affect the resistance of renal blood flow, so we assumed that RRI could help to monitoring the changes in renal hemodynamics at different PEEP levels. Our hypothesis was that the RRI at ICU admission could predict the risk of acute kidney injury in mechanical ventilated critically ill patients. METHODS: We performed a prospective study including 92 patients requiring mechanical ventilation for ≥ 48 h. A RRI ≥ 0.70, was deemed as pathological. RRI was measured within 24 h from ICU admission while applying 5,10 and 15 cmH2O of PEEP in random order (PEEP trial). RESULTS: Overall, RRI increased from 0.62 ± 0.09 at PEEP 5 to 0.66 ± 0.09 at PEEP 15 (p < 0.001). The mean RRI value during the PEEP trial was able to predict the occurrence of AKI with AUROC = 0.834 [95%CI 0.742-0.927]. Patients exhibiting a RRI ≥ 0.70 were 17/92(18%) at PEEP 5, 28/92(30%) at PEEP 10, 38/92(41%) at PEEP 15, respectively. Thirty-eight patients (41%) exhibited RRI ≥ 0.70 at least once during the PEEP trial. In these patients, AKI occurred in 55% of the cases, versus 13% remaining patients, p < 0.001. CONCLUSIONS: RRI seems able to predict the risk of AKI in mechanical ventilated patients; further, RRI values are influenced by the PEEP level applied. TRIAL REGISTRATION: Clinical gov NCT03969914 Registered 31 May 2019.

Association of mildly elevated pulmonary vascular resistance with major cardiovascular events in pulmonary hypertension and chronic kidney disease: A retrospective cohort analysis.

Pulmonary hypertension (PH) is associated with adverse outcomes in chronic kidney disease (CKD) patients. Our study suggests mildly elevated pulmonary vascular resistance ( > 2 to ≤ 3) is independently associated with major adverse cardiovascular events at 1-year follow-up. Early diagnosis of precapillary PH in CKD patients can potentially improve clinical outcomes.

Kidney computed tomography perfusion in patients with ureteral obstruction.

INTRODUCTION: Kidney perfusion on CT is an encouraging surrogate for renal scintigraphy in assessing renal function. However, data on dynamic volumetric CT in patients with kidney obstruction is lacking. Thus, the aim of this study is to determine the feasibility of CT-based renal perfusion using a dynamic volume to assess renal hemodynamics at different degrees and durations of obstruction. MATERIALS AND METHODS: We included patients with unilateral kidney obstruction in our single-center, prospective study. The patients were divided into three groups. Patients without dilatation of the pelvicalyceal system (PCS) and normal parenchyma thickness were included into Group 1; patients with PCS dilatation and parenchyma thickness 1.8-2.4 cm-into Group 2; and patients with ureteropyelocalicoectasia and parenchyma thickness less than 1.8 cm-into Group 3. RESULTS: Total of 56 patients were enrolled. In Group 1 mean values of cortical and medullar arterial blood flow, blood volume, and extraction fraction were within the normal range. Changes in contralateral kidney were not determined. Patients from Group 2 showed significant differences in blood flow parameters in the cortical and medulla of the obstructed kidney. No changes in perfusion values in the contralateral kidney was observed. In patients from Group 3 there was a marked decrease in perfusion on the side of obstruction compared to Group 2, indicating that the degree of expansion of the PCS directly correlates with the change in blood flow. However, in the contralateral kidney, these indicators exceeded the normal values of perfusion. CONCLUSION: CT perfusion allows to objectively assess changes in blood flow in the setting of renal obstruction. The degree of obstruction directly affects the measured rate of blood flow.

Dynamic rubidium-82 PET/CT as a novel tool for quantifying hemodynamic differences in renal blood flow using a one-tissue compartment model.

PURPOSE: Assessing renal perfusion in-vivo is challenging and quantitative information regarding renal hemodynamics is hardly incorporated in medical decision-making while abnormal renal hemodynamics might play a crucial role in the onset and progression of renal disease. Combining physiological stimuli with rubidium-82 positron emission tomography/computed tomography (82Rb PET/CT) offers opportunities to test the kidney perfusion under various conditions. The aim of this study is: (1) to investigate the application of a one-tissue compartment model for measuring renal hemodynamics with dynamic 82Rb PET/CT imaging, and (2) to evaluate whether dynamic PET/CT is sensitive to detect differences in renal hemodynamics in stress conditions compared to resting state. METHODS: A one-tissue compartment model for the kidney was applied to cardiac 82Rb PET/CT scans that were obtained for ischemia detection as part of clinical care. Retrospective data, collected from 17 patients undergoing dynamic myocardial 82Rb PET/CT imaging in rest, were used to evaluate various CT-based volumes of interest (VOIs) of the kidney. Subsequently, retrospective data, collected from 10 patients (five impaired kidney functions and five controls) undergoing dynamic myocardial 82Rb PET/CT imaging, were used to evaluate image-derived input functions (IDIFs), PET-based VOIs of the kidney, extraction fractions, and whether dynamic 82Rb PET/CT can measure renal hemodynamics differences using the renal blood flow (RBF) values in rest and after exposure to adenosine pharmacological stress. RESULTS: The delivery rate (K1) values showed no significant (p = 0.14) difference between the mean standard deviation (SD) K1 values using one CT-based VOI and the use of two, three, and four CT-based VOIs, respectively 2.01(0.32), 1.90(0.40), 1.93(0.39), and 1.94(0.40) mL/min/mL. The ratio between RBF in rest and RBF in pharmacological stress for the controls were overall significantly lower compared to the impaired kidney function group for both PET-based delineation methods (region growing and iso-contouring), with the smallest median interquartile range (IQR) of 0.40(0.28-0.66) and 0.96(0.62-1.15), respectively (p < 0.05). The K1 of the impaired kidney function group were close to 1.0 mL/min/mL. CONCLUSIONS: This study demonstrated that obtaining renal K1 and RBF values using 82Rb PET/CT was feasible using a one-tissue compartment model. Applying iso-contouring as the PET-based VOI of the kidney and using AA as an IDIF is suggested for consideration in further studies. Dynamic 82Rb PET/CT imaging showed significant differences in renal hemodynamics in rest compared to when exposed to adenosine. This indicates that dynamic 82Rb PET/CT has potential to detect differences in renal hemodynamics in stress conditions compared to the resting state, and might be useful as a novel diagnostic tool for assessing renal perfusion.

The effect of Cratylia floribunda lectin on renal hemodynamics and ion transport

Lectins have been described as glycoproteins that reversibly and specifically bind to carbohydrates. Legume lectins isolated from the subtribe Diocleinae (Canavalia, Dioclea andCratylia) are structurally homologous with respect to their primary structures. The Diocleinae lectins of Canavalia brasiliensis, Dioclea guianensis andCanavalia ensiformis have been shown to distinctly alter physiological parameters in isolated rat kidneys. Thus, the aim of this study was to investigate the effect of Cratylia floribunda lectin (CFL) on renal hemodynamics and ion transport in rats. In isolated perfused kidneys, CFL (10 mg/mL, n=5) increased RPP, RVR and decreased %TK+, but did not change urinary flow, glomerular filtration rate, sodium or chloride tubular transport. In isolated perfused mesenteric bed, CFL (3 and 10 mg/mL/min; n=4) did not alter tissue basal tonus or tissue contraction by phenylephrine (1 mM/mL/min). In conclusion, the seed lectin of Cratylia floribunda increased renal hemodynamic parameters showing a kaliuretic effect. This effect could be of tubular origin, rather than a result from haemodynamic alterations.

As lectinas são descritas como (glico)proteínas que se ligam, especificamente e reversivelmente, a carboidratos. Lectinas de leguminosas isoladas da subtribo Diocleinae (Canavalia, Dioclea eCratylia) são estruturalmente homólogas em relação às suas estruturas primárias. Demonstrou-se que as lectinas de DiocleinaeCanavalia brasiliensis, Dioclea guianensis eCanavalia ensiformis alteram diferentemente parâmetros fisiológicos em rins isolados de ratos. Dessa maneira, o objetivo deste estudo foi investigar o papel da lectina de Cratylia floribunda (CFL) na hemodinâmica renal e no transporte de íons em ratos. Em rins isolados perfundidos, CFL (10 mg/mL, n=5) aumentou a pressão de perfusão renal, a resistência vascular renal e reduziu o percentual do transporte tubular de K+, mas não alterou o fluxo urinário, a taxa de filtração glomerular e o percentual de transporte tubular dos íons sódio e cloreto. No leito mesentérico isolado perfundido, CFL (3 e 10 mg/mL/min, n=4) não alterou o tônus basal ou a contração do tecido induzida por fenilefrina (1 mM/mL/min). Em conclusão, a lectina de sementes de Cratylia floribunda altera parâmetros hemodinâmicos renais, provavelmente de origem tubular, e não por alterações hemodinâmicas.

Obesidade e doença renal crônica / Obesity and chronic kidney disease

A epidemia de obesidade que atinge a maioria dos países ocidentais é acompanhada por uma elevação alarmante no número de casos novos de doença renal crônica (DRC). A obesidade cursa com alterações hemodinâmicas renais caracterizadas por aumento do fluxo plasmático renal, hiperfiltração glomerulare retenção salina. A estas alterações, freqüentemente, se superpõem co-morbidades como o diabete melito e a hipertensão arterial, consideradasduas das causas mais freqüentes de DRC. Além disso, a obesidade pode acelerar a evolução de glomerulopatias preexistentes e pode induzir lesão renalde novo em pacientes uninefrectomizados. Finalmente, a obesidade tem sido associada a um tipo específico de lesão glomerular, manifesta por proteinúria,glomerulomegalia e esclerose glomerular segmentar e focal, o que também contribui para a gênese da DRC. No presente artigo, os autores d i s c u t em aspectos da interação entre obesidade e rim, bem como seu papel na indução e na progressão de nefropatias.

The worldwide epidemic of obesity has been associated with an alarming increase in the incidence of chronic kidney disease (CKD). Obesity courses with renal hemodynamic changes characterized by increased renal plasma flow, glomerular hyperfiltration and salt retention. Furthermore, obesity is associated with type 2 diabetes and hypertension, the two leading causes of CKD. Obesity can accelerate pre-existing glomerulopathy and is also implicated in the induction of renal disease de novo in patients subjected to unilateral nephrectomy. Finally, the obesity-related glomerulopathy, a clinical entity manifestedby proteinuria, glomerulomegaly and focal and segmental sclerosis, could also contribute to increase the prevalence of CKD. In this review, the authorsdiscuss the relationship between obesity and kidney as well as the role of obesity in inducing and worsening the outcome of nephropathies.