Noninvasive Evaluation of Intrarenal Oxygenation With BOLD MRI

Prasad, Pottumarthi V.; Edelman, Robert R.; Epstein, Franklin H.

doi:10.1161/01.cir.94.12.3271

Cited by 375 publications

(367 citation statements)

References 21 publications

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“…Prasad et al demonstrated in conscious volunteers that 20 mg of furosemide increased medullary oxygenation, using the blood oxygen level-dependent magnetic resonance imaging technique (BOLD MRI) [16]. In contrast, acetaz olamide, which inhibits tubular reabsorption of the proximal tubules in the cortex and which does not aff ect medullary PO 2 in experimental studies, did not aff ect medullary oxygenation.…”

Section: Eff Ects Of Diureti Cs On Renal Oxygenation In the Postoperamentioning

confidence: 99%

Renal Oxygenation in Clinical Acute Kidney Injury

Ricksten¹,

Bragadottir²,

Redfors³

2013

Annual Update in Intensive Care and Emergency Medicine 2013

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Renal oxygenation is defi ned as the relationship between renal oxygen delivery (DO 2 ) and renal oxygen consumption (VO 2 ) and it can easily be shown that the inverse of this relationship is equivalent to renal extraction of O 2 (O 2 Ex). An increase in renal O 2 Ex means that renal DO 2 has decreased in relation to renal VO 2 , i. e., renal oxygenation is impaired, and vice versa. When compared to other major organs, renal VO 2 is relatively high, second only to the heart. In sedated, mechanically ventilated patients, renal VO 2 is two-thirds (10 ml/min) that of myocardial oxygen consumption (15 ml/min) (Table 1) [1,2]. Renal blo od fl ow, w hich accounts for approximately 20 % of cardiac output, is three times higher than myocardial blood fl ow in this group of patients. Renal O 2 Ex in the non-failing kidney is therefore low, 10 %, compared with, e.g., the heart, in which O 2 E X is 55 % (Table 1). Determin a nts of renal oxygenationIt is well known from experimental studies that tubular sodium reabsorption is the major determinant of renal VO 2 [3] and tha t under normal physiological conditions, approximately 80 % is used to drive active tubular transport of particularly sodium, but also glucose, amino acids and other solutes. Tubular transport processes are highly load-dependent and it has been shown in experimental studies [4] and in p atients [2,[5][6][7] that the re i s a close linear correlation between glomerular fi ltration rate (GFR), renal sodium reabsorption and renal VO 2 (Fig. 1). Th e fi l tered load of sodium is, thus, an important determi nant of renal VO 2 and maneuvers that decrease GFR and the tubular sodium load act to decrease tubular sodium reabsorption and renal VO 2 , and vice versa [8]. It has b een shown that renal O 2 Ex remains stable over a wide range of renal blood fl ows, which means that changes in renal DO 2 , caused by changes in renal blood fl ow, are directly off set by changes in renal VO 2 [9], i. e., r enal VO 2 is fl ow-dependent. Th us, unlike other organs where increases in blood fl ow will improve oxygenation, increased renal blood fl ow augments GFR and the fi ltered load of sodium, which will increase renal VO 2 . Due to this fl ow-dependency of renal VO 2 , renal oxygenation will re main constant, as long as renal blood fl ow and GFR change in parallel. Regional intrarenal oxygenation and medullary hypoxiaTh e relatively high renal blood fl ow is directed preferentially to the cortex to optimize the fi ltration process and solute reabsorption. In contrast, blood fl ow in the outer medulla is less than 50 % of the cortical blood fl ow to preserve osmotic gradients and to enhance urinary concentration [10]. Th e combi nation of low me dullary perfusion, high oxygen consumption of the medullary thick ascending limbs (mTAL) and the countercurrent exchange of oxygen within the vasa recta, results in a poorly oxygenated outer medulla [11]. Oxygen av ailability is, therefore, low in the outer medulla, which has an oxygen tissue partial pressure (PO 2 ) of 10-20 mm Hg ...

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Section: Eff Ects Of Diureti Cs On Renal Oxygenation In the Postoperamentioning

confidence: 99%

Renal Oxygenation in Clinical Acute Kidney Injury

Ricksten¹,

Bragadottir²,

Redfors³

2013

Annual Update in Intensive Care and Emergency Medicine 2013

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“…Blood oxygen level dependant (BOLD) MRI has the ability to detect changes in hemoglobin oxygenation due to the dephasing effects of deoxyhemoglobin (26,27). This allows for a noninvasive measure of renal tissue oxygenation (28), and has been advocated for use in differentiating ATN and rejection in the transplant kidney (29).…”

Section: Other Functional Mri Techniquesmentioning

confidence: 99%

“…6) may be an indicator of acute rejection. Further support for this consideration comes from the finding that functional T2-mapping (BOLD) MRI has been shown to differentiate ATN and acute rejection (27,57).…”

Section: Acute Rejectionmentioning

confidence: 99%

Kidney transplantation: Structural and functional evaluation using MR Nephro‐Urography

Kalb

Martín

Salman

et al. 2008

Magnetic Resonance Imaging

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End-stage-renal disease (ESRD) is a major health issue in the United States, and the Medicare costs of ESRD totaled nearly $21 billion in 2005. Renal transplantation has emerged as the treatment of choice in this patient population, providing improved quality of life and lower healthcare costs compared with other treatment options. Imaging evaluation of a graft kidney plays a critical role in the postoperative care of the renal transplant patient. In the past, diagnostic evaluation of the transplant kidney has depended upon a combination of ultrasonography, computed tomography, MRI, and biopsy, used in conjunction with the patient's clinical presentation. However, new and developing advances in MR technology has lead to the development of MR Nephro-Urography (MRNU), which provides both anatomic and functional evaluation of the kidney in a single examination. It is expected that the increasing use of MRNU will have a significant impact on the management of renal transplant patients. This review describes MRNU methodology, examines known posttransplant complications, and highlights the utility of MRNU as a comprehensive imaging examination to diagnose both surgical and medical complications of the transplant kidney.

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“…Differences in concentrations of deoxyhemoglobin modulate microscopic field gradients in the vicinity of blood cells and vessels. 79 These intravoxel alterations in the magnetic field cause loss of phase coherence, which leads to signal loss on gradient echo T2-weighted images, the so-called BOLD contrast.…”

Section: Bold Imagingmentioning

confidence: 99%

Magnetic resonance imaging as a biomarker in renal cell carcinoma

Pedrosa

Alsop

Rofsky

2009

Cancer

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The ability to noninvasively discriminate the most common types of renal cell carcinoma (RCC) based on their magnetic resonance imaging (MRI) appearances or their magnetic resonance phenotypes is achievable. Intracellular lipids, a histologic characteristic of the clear cell RCC, can be identified on chemical shift MRI. Intratumoral hemosiderin deposition, as observed histologically with papillary RCC, correlates to the low signal intensity on T2-weighted images. In addition to morphologic imaging features, the different subtypes of RCC have distinct patterns of enhancement on dynamic contrast-enhanced MRI. Clear cell tumors demonstrate much greater enhancement than papillary and chromophobe RCCs during the corticomedullary and nephrographic phases. The MRI technique arterial spin labeling (ASL) uses magnetic fields to label the water protons in arterial blood and measures blood flow into tissue; quantitative images of blood flow can be generated without exogenous contrast media. Multiple measurements of tumor perfusion may be repeated before and after a physiologic or drug challenge (ie, antiangiogenic therapy). In RCC xenografts and in patients with metastatic RCC, ASL MRI assessments can be used to monitor blood flow changes in response to antiangiogenic therapies. High blood flow on ASL MRI in RCC xenografts correlates with viable tumor at histopathologic analysis, whereas zones of absent or diminished signal correspond to necrosis. ASL MRI has the potential to serve as a biomarker for patients with metastatic RCC by offering a noninvasive measure of tumor blood flow changes accompanying antiangiogenic therapy. Cancer 2009;115(10 suppl):2334-45.

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Noninvasive Evaluation of Intrarenal Oxygenation With BOLD MRI

Abstract: BOLD MRI can be used to monitor changes in intrarenal oxygenation in humans in a noninvasive fashion.

Cited by 375 publications

References 21 publications

Renal Oxygenation in Clinical Acute Kidney Injury

Renal Oxygenation in Clinical Acute Kidney Injury

Kidney transplantation: Structural and functional evaluation using MR Nephro‐Urography

Magnetic resonance imaging as a biomarker in renal cell carcinoma

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