Degree of portal vein thrombosis


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Degree of Portal Vein Thrombosis

To the Editor:

We read with very great interest the prospective study1 from the European Network for Vascular Disorders of the Liver (EN-Vie) providing stronger evidence of anticoagulation for acute portal vein thrombosis (PVT) without cirrhosis than any previous retrospective studies with a smaller sample size.2–4 Despite the other clear and valuable results in the study, existence of a statistically significant difference between recanalization rate of portal vein and that of splenic or superior mesenteric vein is confusing (Table 1), and is marginal in appearance, which seems to be attributed as a plateau in 1-year recanalization over time for portal vein (recanalization did not occur beyond 6th month), but there was no apparent plateau for splenic and superior mesenteric vein (recanalization stopped in the 9th and 11th month, respectively). Is the discrepancy rational between different segments of the same portal vein system? If so, why?

Table 1. Patency of Portal Venous Segments in the Prospective Study
Location of ObstructionPresent* (%)Absent (%)P Value
  • *

    Thrombosis still present.

  • Thrombosis still absent.

  • Pearson chi-squared test.

Portal vein or both its two branches58 (70%)29 (30%)0.032
Superior mesenteric vein19 (47%)25 (53%) 
Splenic vein22 (46%)26 (54%) 

Perhaps one of the major reasons lies in the degree of thrombosis—complete or partial—that is missing among factors predicting recanalization, which unanimously exists in the four classical studies1–4 about anticoagulation for PVT. Naturally, the difficulty of recanalization increases with degree of thrombosis, whether acute or chronic in stage and noninvasive or invasive in management of PVT. In other words, the gap among patency of various portal venous segments would have disappeared, if the data were stratified according to complete or partial obstruction.

In contrast, degree stratification is consistently involved in the studies about outcome of invasive therapies for PVT5–9 due to its close associations with operability and prognosis. Herein, diverse classifications of PVT were listed in Table 2, except for simple classification into complete and partial thrombus. Further, some classical images in our patients are demonstrated (Fig. 1) for a clear distinction between partial and complete occlusion, which are mainly characterized by partial and complete absence of flow within portal vein on color Doppler ultrasound or angiography, or a filling defect and “train track” appearance of enhancement on computed tomography.10

Figure 1.

Complete and partial portal vein thrombosis on color Doppler ultrasound, computer tomography and angiography. Partial and complete thrombosis are represented by dotted arrow on the left (Panel A, C & E) and solid on the right (Panel B, D & F).

Table 2. A Brief Summary About Classifications of Portal Vein Thrombosis
Authors (published date)Grade IGrade IIGrade IIIGrade IV
  1. Abbreviations: LPB, left portal branch; RPB, right portal branch; MPV, main portal vein; NA, not available; PV, portal vein; PVT, portal vein thrombosis; SMV, superior mesenteric vein; SV, splenic vein; SVT, splenic vein thrombosis.

Stieber et al. (1990)Partial PVT or patent PVComplete PVT ± SVTExtensive thrombosis (including SMV)NA
Nonami et al. (1992)Thrombosis within intrahepatic portal branchesThrombosis within RPB or LPB or the bifurcationPartial thrombosis within MPVComplete thrombosis within MPV
Yerdel et al. (2000)<50% PVT ± minimal obstruction within SMV>50% PVT ± minimal obstruction within SMVComplete PV and proximal SMV thrombosisComplete PV and entire SMV thrombosis
Jamieson NV. (2000)Thrombosis confined to PV beyond the splenomesenteric confluence, which may be either partial or completeThrombosis extending into the proximal SMV system, but with a patent vessel in the mesenteryDiffuse thrombosis of the splanchnic venous system, but with large accessible collateralsExtensive thrombosis of the splanchnic venous system, but with only fine collaterals
Bauer et al. (2006)Less than 25% occluded in PV, SMV or SV26%–50% occluded in PV, SMV, or SV51%–75% occluded in PV, SMV or SV76%–100% occluded in PV, SMV, or SV

From our perspectives, it is necessary for prediction of recanalization to accurately distinguish between complete and partial thrombosis in any study on management of PVT.

Xingshun Qi*, Guohong Han*, Jianhong Wang†, Kaichun Wu‡, Daiming Fan‡, * Department of Digestive Interventional Radiology, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China, † Department of Ultrasound, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China, ‡ State Key Laboratory of Cancer Biology, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China.