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What is happening with this liver graft?

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Objectives

To understand the importance of close follow up of liver transplantation with ultrasound, in particular using Doppler ultrasound, to evaluate for complications in the pediatric population.


Case Presentation

A 7 month old female infant was transplanted on 11 April 2018 because of a non-functioning Kasai procedure for biliary atresia with secondary biliary cirrhosis with portal hypertension (Figure 1). No complications were reported at surgery.

A close follow up was performed with ultrasound with Doppler evaluation following the transplantation.

A summary of follow up with the main ultrasound and Doppler findings are displayed on Table 1.

The ultrasound findings on the first days following transplantation report some collections surrounding the graft and perivascular hyper-echogenicity; these were interpreted as hematomas and perivascular edema associated with the surgery.

Doppler ultrasound evaluation at 24 and 48 hours post-transplant was normal (Figure 2).

On the third day post-transplantation inversion of diastole of the hepatic artery was noted (resistive index (RI) > 1). The change in RI was associated with worsening of liver function tests, interpreted as graft dysfunction associated with possible perfusion changes. These changes were transient as on subsequent imaging hepatic artery RI remained within expected normal values (Table 1) and enzyme levels improved.

On further ultrasound follow up the graft parenchyma became increasingly heterogeneous with areas of increased reflectivity and some posterior attenuation, more evident with a perivascular and subcapsular distribution (Figures 3 and 4). As these changes became progressively more prominent the suspicion of graft parenchymal calcifications was raised. 

In addition on ultrasound elastography (ARFI virtualTouchSiemens) performed at 4 months liver stiffness was heterogeneous throughout (values reported on Table 1).

A contrast enhanced computed tomography (CT) was performed, shown in Figure 5, for vascular study which detected heterogeneously distributed spontaneous high density, interpreted as diffuse calcification of the graft, with liver enzyme levels within normal range.

The presence of microscopic foci of calcifications was confirmed on biopsy, at 7 months post transplant, associated with only mild liver fibrosis (Figures 6). 


Conclusions

The major complications detected post-transplant are of vascular etiology, namely arterial and venous thrombosis and stenosis, arterial pseudoaneurysm, liver ischemia and infarction, but may also affect the biliary tree or be associated with peri-graft fluid collections. These complications can promptly be identified using ultrasound complemented with Doppler.

In children, unlike the adults, the resistive index (RI) of the hepatic artery may be higher immediately following transplantation with normal values ranging up to 0.95, especially in infants (the younger the child, the higher the expected resistive index).

A higher risk of vascular complications is identified in patients with RI inferior to 0.5 or higher than 0.95.

We present a case of an infant that had a transient ischemic episode at day 3 post transplantation, documented on Doppler ultrasound by a RI > 1. On further follow up no vascular changes were reported but the graft parenchyma became increasingly heterogeneous and hyperreflective. This heterogeneity was associated with diffuse calcification of the liver graft parenchyma with a perivascular and left subcapsular preponderance, confirmed on CT and at histology. 

 Liver transplantation is frequently associated with ischemia-reperfusion injuries and at times extensive ischemia may be associated with calcification of the graft. This case depicts the evolution of the findings and their early heterogeneous appearance on ultrasound.

Despite de normalization of the liver enzymes, the early changes and evolution in graft echogenicity and texture noted on ultrasound as well as changes in the Doppler evaluation (RI inferior to 0.5 or higher than 0.95) should be more valued and help guide the patient’s management in cases where ischemia-perfusion injuries are suspected.

 

References

1.Ahmad T, ChavhanGB, AvitzurY, MoineddinR, OudjhaneK. Doppler Parameters of the Hepatic Artery as Predictors of Graft Status in Pediatric Liver Transplantation. AJR (2017); 209:671–675
2.Jamieson LH, ArysB, Low G, Bhargava R, KumblaS, JaremkoJL. Doppler Ultrasound Velocities and Resistive Indexes Immediately After Pediatric Liver Transplantation: Normal Ranges and Predictors of Failure. AJR (2014); 203:W110–W116
3.ChavhanGB, Parra DA, Mann A, Navarro OM. Normal Doppler Spectral Waveforms of  Major Pediatric Vessels: Specific Patterns. RadioGraphics(2008); 28:691–706
4.Quiroga S,  SebastiàMC, MargaritC, Castells L, BoyéR, Alvarez-Castells A. Complications of Orthotopic Liver Transplantation: Spectrum of Findings with Helical CT. RadioGraphics(2001) 21: 1085–1102
5.JengK-S, Huang C-C, Lin C-K, Lin C-C, Chen K-H. Graft Calcification Caused by a Torsion of the Hepatic Vein after a Living-Related Donor Liver Transplantation. Annals of Hepatology (2017) 16(1): 164-168
6.TzimasGN, Afshar M, Chevet E, EmadaliA, Vali H, MetrakosPP. Graft calcifications and dysfunction following liver transplantation . BMC Surgery (2004) 4(9)
7.Kalantari F, Miao D, EmadaliA, TzimasGN, GoltzmanD, Vali H, Chevet E, Auguste P. Cellular and molecular mechanisms of abnormal calcification following ischemia–reperfusion injury in human liver transplantation. Modern Pathology (2007) 20: 357–366
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