Reliable kidney size determination by magnetic resonance imaging in pathophysiological settings

Abstract

Aim Kidney diseases constitute a major health challenge, which requires noninvasive imaging to complement conventional approaches to diagnosis and monitoring. Several renal pathologies are associated with changes in kidney size, offering an opportunity for magnetic resonance imaging (MRI) biomarkers of disease. This work uses dynamic MRI and an automated bean‐shaped model (ABSM) for longitudinal quantification of pathophysiologically relevant changes in kidney size. Methods A geometry‐based ABSM was developed for kidney size measurements in rats using parametric MRI (T2, T2* mapping). The ABSM approach was applied to longitudinal renal size quantification using occlusion of the (a) suprarenal aorta or (b) the renal vein, (c) increase in renal pelvis and intratubular pressure and (d) injection of an X‐ray contrast medium into the thoracic aorta to induce pathophysiologically relevant changes in kidney size. Results The ABSM yielded renal size measurements with accuracy and precision equivalent to the manual segmentation, with >70‐fold time savings. The automated method could detect a ~7% reduction (aortic occlusion) and a ~5%, a ~2% and a ~6% increase in kidney size (venous occlusion, pelvis and intratubular pressure increase and injection of X‐ray contrast medium, respectively). These measurements were not affected by reduced image quality following administration of ferumoxytol. Conclusion Dynamic MRI in conjunction with renal segmentation using an ABSM supports longitudinal quantification of changes in kidney size in pathophysiologically relevant experimental setups mimicking realistic clinical scenarios. This can potentially be instrumental for developing MRI‐based diagnostic tools for various kidney disorders and for gaining new insight into mechanisms of renal pathophysiology.

Monitoring kidney size to interpret MRI‐based assessment of renal oxygenation in acute pathophysiological scenarios

“…Recognizing the potential of MR-based probing of renal oxygenation as a meaningful tool for research into renal physiology and disorders, this study provides systematic tests for acute changes in T 2 * and T 2 as markers of oxygenation, and in KS determined from the T 2 *, T 2 maps. 37 Serial in vivo parametric MRI mapping of T 2 *, T 2 was performed in rats during interventions that alter renal tissue oxygenation reversibly (a brief occlusion of the suprarenal aorta, the left renal vein or both; hypoxemia), and with longer-lasting effects (injection of CM or furosemide). We hypothesize that monitoring KS will allow physiological interpretation of acute changes in renal oxygenation measured by T 2 *, T 2 .…”

“…Events leading to acute renal hypoxia are often associated with KS changes. Studies emulating clinical procedures such as clamping of the suprarenal aorta or renal artery during surgery, or the low arterial target pressure during cardiopulmonary bypass, revealed KS reductions 27,37 . Conversely, anecdotal evidence indicates opposite effects for obstructing the renal vein, such as in partial nephrectomy or thrombus formation in renal cell carcinoma 37,38 .…”

“…Studies emulating clinical procedures such as clamping of the suprarenal aorta or renal artery during surgery, or the low arterial target pressure during cardiopulmonary bypass, revealed KS reductions 27,37 . Conversely, anecdotal evidence indicates opposite effects for obstructing the renal vein, such as in partial nephrectomy or thrombus formation in renal cell carcinoma 37,38 . Studies emulating administration of X‐ray contrast media (CM) for cardiac procedures showed renal hypoxia and increased intratubular pressure 31,39–41 .…”

Prolyl hydroxylase inhibitors, polydrug use, and the phosphoproteome

“…Thus, noninvasive methods are under development to gain insight into the pathophysiology of various kidney disorders. 8 For example, blood oxygenation level-dependent (BOLD) MRI to assess kidney hypoxia is of great interest. 6,9 Is there a link between kidney disease and hypoxia?…”

“…Hence, we seldom get a look inside the kidney's sophisticated clockwork. Thus, noninvasive methods are under development to gain insight into the pathophysiology of various kidney disorders 8 . For example, blood oxygenation level‐dependent (BOLD) MRI to assess kidney hypoxia is of great interest 6,9 …”