Liver Transplantation for Porto-sinusoidal Vascular Liver Disorder: Unmet Questions

We read with great interest a recent international multicenter study by Marta Magaz et al,¹ analyzing postdeceased donor liver transplantation outcomes in 50 of 587 porto-sinusoidal vascular disorder (PSVD) patients registered at 28 participating centers from 1990 to 2020. Additionally, 4 of the 28 centers, performing 4322 LTs, reclassified 29 patients as PSVD after reviewing explant histology registries. We have specific essential points to note.

First, the risk of progression of PSVD to advanced liver disease is highly variable, but the specific risk factors and the pathogenic mechanisms leading to these complications should have been researched. Given that the diagnosis of PSVD primarily relied on the recognition of “specific” histologic features on good-quality liver biopsies before liver transplantation (LT),² the histological changes in the 50 explant livers should have been studied and compared with pre-LT liver biopsies to grade the severity of lesions. Theoretically, it makes sense that the degree of histological changes corresponds to the degree of portal hypertension (PHT) and decompensation. Currently, the individual histologic lesions of PSVD are evaluated using a 2-tiered system for the lesion’s absence (score 0) or presence (score 1). In the presence of similar histological lesions, it is imperative to know why some patients with PSVD developed portal hypertension and decompensation, and others did not. Vice versa, does the grading of histological lesions differ for PSVD patients who develop severe PHT and decompensation compared with those who do not? Maybe the authors can study the 50 explants with this perspective and pick up the other subtle differences between decompensated PSVD versus cirrhosis patients.

Second, with PSVD being a presinusoidal disorder, probably a higher portal pressure may be required to produce a similar level of ascites than in patients with cirrhosis. Also, PSVD patients commonly have sinusoidal dilation as a finding in liver samples. Hence, it is important to know if the hepatic venous pressure gradient measurement has been done in these 50 decompensated PSVD patients to identify the presence of sinusoidal PHT.^3,4

Third, LT was indicated for 2 of 79 PSVD patients with hepatocellular carcinoma. One had a history of previous hepatitis B with negative HBsAg and undetectable DNA before LT. The other patient had type 2 diabetes and showed obliterative portal venopathy and incomplete septal fibrosis. In patients with hepatocellular carcinoma (HCC), it is imperative to consider the possibility of a coexisting second potential trigger of HCC as PSVD is infrequently associated with HCC,⁵ and the exact etiopathogenesis of HCC in the setting of PSVD is unclear. Also, incomplete septal cirrhosis may represent regressed cirrhosis and may be unrelated to the risk factors of PSVD.⁶ In this case, let us assume an overlap of PSVD and parenchymal liver disease, but how to determine the respective contribution of each in the development of HCC is unclear. Hence, these 2 HCC patients may not have been included in the study.

Fourth, 21 PSVD patients with severe associated conditions had suboptimal 1-y (85.2 versus 74.3%) and 5-y survival (74.8 versus 45.3%). In the deceased donor liver transplantation setting, the principle of nonfutility is also as important as the principle of utility.⁷ Hence, organ allocation to these patients should be critically appraised.