Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) uses deoxyhemoglobin as an endogenous contrast agent for the noninvasive assessment of tissue oxygen bioavailability. We hypothe...

BOLD-MRI assessment of intrarenal oxygenation and oxidative stress in patients with chronic kidney allograft dysfunction

Acute kidney injury (AKI) is common in critically ill patients and associated with important morbidity and mortality Although alterations in renal perfusion are thought to play a causative role in the pathogenesis of AKI, there is, to date, no reliable technique that allows the assessment of renal perfusion that is applicable in the ICU Contrast-enhanced ultrasound (CEUS) is an ultrasound imaging technique that makes use of microbubble-based contrast agents These microbubbles, when injected into the bloodstream, allow visualization of vascular structures and, with contrast-specific imaging modes, detection of blood flow at the capillary level Some recent CEUS-derived approaches allow quantification of blood flow in several organs, including the kidney Current generation ultrasound contrast agents have strong stability and safety profiles Along with post-marketing surveillance, numerous studies report safe administration of these agents, including in critically ill patients This review presents information on the physical principles underlying CEUS, the methods allowing blood flow quantification and the potential applications of CEUS in critical care nephrology, currently as a research tool but perhaps in the future as a way of monitoring renal perfusion

https://ahro.austin.org.au/austinjspui/bitstream/1/11264/1/21586101.pdf

Bench-to-bedside review: Contrast enhanced ultrasonography - a promising technique to assess renal perfusion in the ICU

To describe the method and significance of Doppler-based resistive index (RI) and to provide an updated description of its interest with a special focus on the critically ill. Review of selected studies on RI found in the PubMed, Ovid and Cochrane databases. Additional references were retrieved from the selected studies. An increasing body of evidence suggests that renal Doppler may help to assess perfusion of native or transplanted kidneys. In addition, recent studies suggest that it may be useful in critically ill patients. The RI is a parameter derived from Doppler examination that is calculated as follows: $$ {\text{RI}} = \left[ {\text{peak systolic shift}}\,-\,{\text{minimum diastolic shift}} \right]/{\text{peak systolic shift}} $$
 . Renal Doppler has proven to be valuable for assessing large arterial or venous abnormalities and has been suggested to assess renal perfusion and to predict acute kidney injury (AKI) in critically ill patients. However, numerous factors have been shown to influence renal Doppler and may constitute potential confounding factors. Moreover, experience with critically ill patients is scant and our understanding of factors influencing RI in this setting is limited. Doppler-based RI seems to be a promising tool in the critically ill to assess the risk of AKI, help in differentiating persistent from transient AKI, or assess changes in renal perfusion as consequences of therapeutic intervention. However, we still lack large, adequately powered studies in non-selected populations of patients before implementing this technique in clinical practice. In addition, the impact of several factors that may influence this parameter remains to be evaluated.

Renal Doppler to assess renal perfusion in the critically ill: a reappraisal

Ultrasound-based imaging methods of the kidney—recent developments

Objectives The aim of this study was a comparison of contrast-enhanced sonography (CEUS) and power Doppler ultrasound (US) findings in renal grafts within 30 days posttransplantation. Methods A total of 39 kidney recipients underwent CEUS (SonoVue bolus injection) and US examinations at 5 (T0), 15 (T1), and 30 (T2) days after grafting. The results were correlated with clinical findings and functional evolution. Fourteen patients displayed early acute kidney dysfunction: 10 had acute tubular necrosis (acute tubular necrosis [ATN] group); four acute rejection episodes (ARE group); 25 with normal evolution (as control, C group). Renal biopsies were performed to obtain a diagnosis in the four ATN cases and in all ARE patients. Creatinine and estimated glomerular filtration rate were used as kidney function parameters. CEUS analysis was performed both on cortical and medullary regions while US resistivity indexes (RI) were obtained on main, infrarenal, and arcuate arteries. From an analysis of CEUS time-intensity curves, we computed peak enhancement (PEAK), time to peak (TTP), mean transit time (MTT), regional blood flow (RBF) and volume (RBV), and cortical to medullary ratio of these indies (RATIO). Results An increased RI was present in the ATN and ARE groups as well as a reduced PEAK and RBF. RATIO-RBV and RATIO-MTT were lower than C among ATN cases, while TTP was higher compared to C in ARE. No statistical difference was evidence for RI between ATN and ARE groups. MTT (T0) was significantly related to creatinine at follow-up (T2). Conclusions US and CEUS identified grafts with early dysfunction, but only some CEUS-derived parameters distinguished ATN from ARE, adding prognostic information.

Contrast-enhanced sonography in early kidney graft dysfunction.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-6143.2005.01224.x

Real-time contrast-enhanced sonography of renal transplant recipients predicts chronic allograft nephropathy.

Der Begriff kardiale Amyloidose subsumiert eine Herzbeteiligung unterschiedlicher, meist systemischer Erkrankungsformen von Amyloidose, bei der eine abnorme Faltung von Proteinen zu einer Ablagerung in unterschiedlichen Organen fuhrt. Hieraus resultiert eine progrediente Funktionseinschrankung des jeweils betroffenen Organs bis hin zum Organversagen. Die Symptome und klinischen Befunde der einzelnen Formen bei einer kardialen Beteiligung sind unspezifisch und unterscheiden sich nicht wesentlich voneinander. Da jedoch Prognose und Therapie der einzelnen Formen stark divergieren, ist die genaue Differenzierung des spezifischen Amyloidproteins mittels immunhistochemischer Farbung von groser Bedeutung. Eine kardiale Beteiligung bei Amyloidose ist meist mit einer deutlich verschlechterten Prognose assoziiert. Diagnostisch richtungsweisend fur eine kardiale Amyloidose ist eine Herzinsuffizienzsymptomatik mit Niedervoltage im EKG und zum Teil massiver linksventrikularer Hypertrophie in der Echokardiographie. Aufgrund der schwierigen Risikostratifizierung und adaquaten Patientenauswahl fur die verschiedenen Therapieformen, die mit hohem Aufwand und betrachtlicher Komplikationsrate verknupft sind, ist eine Therapieplanung und Durchfuhrung an einem erfahrenen Zentrum zu empfehlen. Zielgerichtetes diagnostisches Vorgehen, prognostische Faktoren und Therapiemoglichkeiten der unterschiedlichen Amyloidoseformen werden im folgenden Beitrag diskutiert.

Kardiale Amyloidose

Release of cardiac enzymes has been reported in patients with stable angina who undergo elective percutaneous coronary intervention (PCI) and has been associated with adverse clinical outcomes. The aim of the present study was to investigate whether impaired microvascular integrity can be detected using myocardial contrast echocardiography in patients undergoing elective PCI, and whether it is related to the extent of postprocedural troponin T elevation. We investigated consecutive patients with stable angina (n = 19) who were scheduled for elective angioplasty with stent placement. Myocardial contrast echocardiography was performed before and 2 to 4 hours and 24 hours after coronary intervention. Contrast images were analyzed visually and quantitatively measuring the peak signal intensity (A) and the slope of the signal intensity rise (β) in 16 myocardial segments. The product of A × β was calculated in each segment to estimate the regional myocardial blood flow. Troponin T was collected serially before and 2 to 4 hours and 24 hours after PCI. Five patients (26%) had elevated troponin T 24 hours after PCI (range 0.03 to 0.46 μg/L). Eight patients (42%), including all 5 patients with elevated troponin T levels, demonstrated impaired microvascular integrity 2 to 4 hours after PCI in ≥2 myocardial segments (range 2 to 4) within the perfusion territory of the target vessel. Of the 11 patients without evidence of impaired myocardial perfusion by myocardial contrast echocardiography, none had elevated troponin T levels at follow-up. Quantitative analysis of myocardial blood flow showed that impaired perfusion after PCI was partially reversible. Thus, A × β had decreased significantly at 2 to 4 hours after PCI (3.4 ± 1.6 vs 8.8 ± 3.4 dB/s baseline, p 2 = 0.80, p

Usefulness of Real-Time Myocardial Perfusion Imaging to Evaluate Alterations of Myocardial Blood Flow in Patients With Stable Angina Pectoris Undergoing Elective Percutaneous Coronary Interventions

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Real-time contrast-enhanced sonography of renal transplant recipients predicts chronic allograft nephropathy.

Kardiale Amyloidose

Usefulness of Real-Time Myocardial Perfusion Imaging to Evaluate Alterations of Myocardial Blood Flow in Patients With Stable Angina Pectoris Undergoing Elective Percutaneous Coronary Interventions