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MRI gives best overall evaluation of living liver donors

Current state-of-the-art MRI techniques can provide a concise, noninvasive method for evaluating potential living liver donors, according to a recently published review.

“With the introduction of cross-sectional imaging techniques, CT and MRI have largely replaced the conventional invasive methods from the preoperative evaluation of donor candidates,” Kartik S. Jhaveri, MD, FRCPC, from the University of Toronto, and colleagues wrote. “However, limitations of CT evaluation should not be ignored either: it involves exposure to ionizing radiation, which is particularly important for donor candidates because most of them are healthy young individuals. MRI is devoid of ionizing radiation, and the gadolinium-based contrast agents are generally safe with rare allergic reactions.”

In the review, the researchers discuss the techniques currently used in their MRI protocol for observing hepatic vascular anatomy, the biliary tract, hepatic steatosis and liver volume.

For hepatic arterial evaluation, the researchers currently use a high-spatial resolution T1-weighted volumetric interpolated breath-hold examination sequencing with a technique known as controlled aliasing in parallel imaging results in higher acceleration, or CAIPIRINHA, and gadoxetic disodium. Gadoxetic disodium provides a higher signal-to-noise ratio of the vascular structure at magnetic resonance angiography (MRA), especially in small vessels.

While conventional T2-weighted 2-D magnetic resonance cholangiography (MRC) and T2-weighted 3-D MRC have shown accurate results in evaluating the biliary tract, they retain their limitations in visual quality. The researchers recommend gadoxetic disodium-enhanced T1-weighted MRC as an alternative to CT cholangiogram for preoperative evaluation.

Regarding hepatic steatosis, “only those donor candidates expected to have substantial hepatic steatosis [10% or higher] on the basis of MRI or [magnetic resonance spectroscopy (MRS)] should require further liver biopsy, whereas an MRI or MRS result indicating an appropriate degree of hepatic steatosis for donation may allow potential donors to avoid liver biopsy,” Jhaveri and colleagues wrote. Their recommendation for hepatic steatosis MRI is a high-speed T2-corrected multiecho H MRS technique using multiple echo times, long repetition time and spectrally corrected methods, as data can be acquired within a 21-second breath-hold and confounding factors are corrected.

Finally, for liver volume, the researchers have found sharper liver edge imagery using the CAIPIRINHA technique and gadoxetic disodium as a contrast agent.

“For hepatic vascular anatomy, gadobenate dimeglumine- or gadoxetic disodium-enhanced MRA is good enough for most patients, although [CT angiography] is still needed for a few cases where the arterial phase is suboptimal. For biliary anatomy, combination use of T2-weighted MRC and gadoxetic disodium–enhanced T1-weighted MRC has evolved as a noninvasive surrogate for [endoscopic retrograde cholangiopancreatography] and CT cholangiogram. For hepatic steatosis, MRI or MRS techniques are helpful to reduce the liver biopsy needs for donor candidates,” the researchers concluded. – by Talitha Bennett

Disclosure: The researchers report no relevant financial disclosures.