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Liver transplantation: significance of the periportal collar on MRI
P Lang1, P Schnarkowski, S Grampp
1Department of Radiology, University of California San Francisco 94143, USA.
Objective:
Liver transplantation is performed with increasing success and frequency all over the world. Experience with MRI of the liver allograft is, however, limited. This study was designed to correlate MRI to clinical-laboratory findings, CT, and biopsy and to evaluate the significance of the periportal collar on MRI.
Materials And Methods:
Fourteen patients who had undergone orthotopic liver transplantation were studied by CT and MRI [T1-weighted imaging: gradient-echo, repetition time/echo time (TR/TE) 306/14 ms, theta 90 degrees; proton density and T2-weighted imaging: spin-echo, TR/TE 1,600/30-120 ms]. Three patients also had follow-up MR examinations 43 days, 89 days, and 5 months after transplantation.
Results:
Magnetic resonance imaging demonstrated a perivascular collar around central portal venous branches in all 14 patients and around peripheral portal branches in 10 of the 14 patients on the initial MRI study. The perivascular collar showed low signal intensity on T1-weighted imaging and an increase in signal intensity on T2-weighted multiecho imaging. The distribution and prevalence of central and peripheral periportal collars were identical on MR and CT. Peripheral periportal collars were seen in 9 patients who had no clinical-laboratory signs of rejection. In 3 patients with biopsy-proved rejection, the periportal collar was less prominent on MR at the time of rejection when compared with MR performed when the patient had no signs of transplant rejection.
Conclusion:
A perivascular collar in a patient with liver transplantation is likely to be related to impaired lymph drainage after surgical interruption of the draining lymph vessels and lymphedema. In contrast to previous CT reports, however, a perivascular collar around peripheral portal branches does not appear to correlate to rejection, since it is frequently observed in the normal liver allograft.
Insights
A perivascular collar on MRI after liver transplantation is likely due to lymph drainage issues, not rejection. Peripheral collars are common in normal allografts, differing from prior CT findings.
Area of Science:
- Radiology
- Transplant Surgery
- Gastroenterology
Background:
- Liver transplantation success is increasing globally.
- Magnetic Resonance Imaging (MRI) experience with liver allografts is limited.
- Understanding imaging findings in liver allografts is crucial for patient management.
Purpose of the Study:
- To correlate MRI findings with clinical, laboratory, CT, and biopsy data in liver transplant recipients.
- To evaluate the significance of the periportal collar observed on MRI.
- To determine if the periportal collar is indicative of transplant rejection.
Main Methods:
- 14 patients undergoing orthotopic liver transplantation were studied using CT and MRI.
- MRI included T1-weighted gradient-echo and proton density/T2-weighted spin-echo sequences.
- Three patients had follow-up MR examinations at various intervals post-transplantation.
Main Results:
- A perivascular collar was identified around central and peripheral portal venous branches in most patients.
- The collar showed characteristic signal intensities on T1 and T2-weighted MRI.
- Peripheral periportal collars were observed in patients without rejection, and collars were less prominent during biopsy-proven rejection episodes.
Conclusions:
- The perivascular collar is likely related to impaired lymph drainage and lymphedema post-surgery.
- Unlike previous CT findings, peripheral periportal collars on MRI do not appear to correlate with rejection.
- The frequent observation of peripheral collars in normal allografts suggests they are not a reliable marker for rejection.