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BOLD imaging of kidney after administration of 2 types of iodinated contrast medium: a time course study in CIN animal models
Kai Zhao1, Xueqing Sui1, Rui Wang1, Zhiyong Lin1, Xiaodong Zhang1, Jian Luo1, and Xiaoying Wang1

1Department of Radiology, Peking University First Hospital, Beijing, People's Republic of China

Synopsis

BOLD is a preeminent noninvasive method to quantify renal function, which may be helpful to understand the pathogenesis of CIN. Our time course study indicates that the iodinated contrast medium can induce some affect to the different zone of kidneys. And some differences do exist on the renal oxygen consumption after the two kinds of iodinated CM administration.

Introduction and Purpose

Usage of iodinated contrast medium (CM) during radiological procedure may cause contrast induced nephropathy (CIN), which has drawn an increasing attention in the whole world. The purpose of this study is to find out the chronological effect of 2 types of iodinated contrast medium in renal oxygen consumption by Blood Oxygenation Level Dependent (BOLD) imaging in CIN animal models

Method

Seventeen New Zealand white rabbits were divided into 3 groups: Group A (Iodixanol-270, n=6), Group B (Iohexol-350, n=6), Group C (0.9% saline, n=5). Respiratory anesthesia was used. MR studies were conducted in a 3.0T GE MR scanner with a knee coil. A sequential Multiple Gradient Echo sequence was performed to estimate the intrarenal oxygen consumption (R2*) at 24h before and 5min, 24h, 48h, 72h after contrast or saline administration. Iodinated contrast agent with a dose of 1380 mg I/kg were injected to the experimental groups (Group A and B), and 0.9% saline with a dose of 5.1 ml/kg (to keep the liquid load equal) was administrated to the control group (Group C). R2* values obtained in the cortex (CO), outer stripe of the outer medulla (OS), inner stripe of the outer medulla (IS) were grouped into 5 time-points : “baseline”, “5min”, “24h”, “48h”, “72h” respectively. Then at last the pathology was obtained. Paired sample t-test was performed to test the change of R2* after iodine administration within each group, and One-Way ANOVA was performed to test the response among the 3 groups in each time-point.

Results

In Group A, Iodixanol-270 induced significant increase of R2* in the CO, OS and IS of the kidney 5 minutes after injection. But this change continued only in the IS 24 hours after administration (Table 1, Figure 1). In Group B, Iohexol-350, induced significant increase of R2* in the CO, and IS of the kidney 5 minutes after injection. And this change disappeared 24 hours after administration (Table 2). There was no obvious changes in Group C (Table 3). As for pathology, significant differences were detected after large dose iopamidol administration in the iodine group (Figure 2, 3, 4). Iopamidol produced moderate to severe tubular epithelial cellular swelling, vacuolar degeneration, necrosis and shedding into the tubular lumens. Focal or multifocal lymphocytes and mononuclear cells infiltration in the interstitium appeared in most of the kidneys. The pathologic changes in Group B was more serious than that in Group A. For the kidneys in the saline group (Group C), light microscopic examinations showed that there was no obvious pathological change in the glomeruli.

Discussion

In this study, rabbits with CIN are animal models. Usage of iodinated contrast medium during radiological procedure may cause CIN. In human, CIN is characterized by an increase in the serum creatinine (Scr) level of at least 0.5 mg/dl or 25% compared to baseline values in the absence of an alternative etiology1. CIN is more and more significant with the increasing use of enhanced CT and interventional diagnosis and treatment.

BOLD is a preeminent noninvasive method to quantify renal function, which may be helpful to understand the pathogenesis of CIN. Our time course study indicates that the iodinated contrast medium can induce some affect to the different zone of kidneys. While some differences do exist on the oxygen consumption in the two kinds of iodinated contrast mediums by BOLD. As we know, the osmotic pressure of Iodixanol-270 (290 mOsm/kgH2O) is much lower than that of Iohexol-350 (844 mOsm/kgH2O). At the same time, the viscosity of Iodixanol-270 (11.3 mPa·s) is also lower than that of Iohexol-350 (11.6 mPa·s). Which factor is the most important? Osmotic pressure? Viscosity? Or other factors? More research is needed to figure out which kine of contrast medium is less harmful to human.

Conclusion

The time course study indicates that some differences do exist on the renal oxygen consumption after the two kinds of iodinated CM administration, which can be detected by BOLD scan and be confirmed by pathology.

Acknowledgements

No acknowledgement found.

References

1. Thomsen HS. Guidelines for contrast media from the European Society of Urogenital Radiology. AJR American journal of roentgenology. 2003;181(6):1463-1471.

Figures

Tables

Figure 1: Kidney partition and a time-course changes of R2*s in one rabbit of Group A.

Figure 2: Gross pathology. The The boundary between cortex and medulla was obscure in Group A and B (A). The boundary between cortex and medulla was distinct in Group C (B). Dark apperence and some bleeding of kidney in iodine group (C,D).

Figure 3: Light microscopic examinations. Iopamidol produced moderate to severe tubular epithelial cellular swelling, vacuolar degeneration, necrosis and shedding into the tubular lumens. Focal or multifocal lymphocytes and mononuclear cells infiltration in the interstitium appeared in most of the kidneys (A, B, C, D). For the kidneys in the saline group, light microscopic examinations showed that there was no obvious pathological change in the glomeruli (E, F).

Figure 4: Electron microscopic examinations. Segmental fusion of the podocyte was seen in both Group A and B with foot process hole shrink or disappear (A,B)

Proc. Intl. Soc. Mag. Reson. Med. 25 (2017)
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