Review for 10.1186/s12876-022-02447-y (2022)

Title: Portal flow diversion based on portography is superior than puncture site in the prediction
of overt hepatic encephalopathy after TIPS creation
Version: 2 Date: 05 Jul 2022
Reviewer:  Oliviero Riggio
Reviewer's report:
The paper is a retrospective analysis based on 252 cirrhotic patients submitted to TIPS and
followed up until death or OLT.
The assumption was to show a relationship between the portal flow and in particular the
entry of blood from the splenic vein (SV) or the mesenteric vein (SMV) as well as the flow
distribution to the left or the right branch of the portal vein and the incidence of post TIPS hepatic
encephalopathy (HE).
The topic is relevant as the incidence of post TIPS HE is still very high and represent probably
the main limitation of the TIPS procedure.
The study is also justified by previous papers which tried to find a relationship between the post
TIPS HE and the portal flow and tried to obtain a reduction in HE by constructing the shunt
using one of the two portal branches (left branch reported to be better than the right).
The conclusion of the authors is that would be possible to identify by means of the preliminary
portography a particular pattern of portal flow associated to a higher incidence of post TIPS HE.
In particular, the patient with a flow coming from the SMV (6.4% of the total) had the highest
HE incidence and a higher elevation of ammonia compared to the patients with a mixed flow
(73% of the total) or with a flow from SV (20%).
The study also analyzed if the shunt constructed from the right or left branch of the portal vein
may induce a difference in HE incidence but no difference was found.
The authors discussed the results adequately as well as the limitation of the study.
The relevance of their observation would be to adopt in the group at higher risk of HE
(flow prevalent from SMV) strategies such as the use of smaller stents or more aggressive
pharmacological preventive treatments. As the patients with these characteristics are few (6,4%),
this strategy probably would not limit the general impact of post TIPS HE but it could be relevant
for this sub group of patients.
Problems:
1. The main question is how much the preliminary portography is reliable in the identification
of the 3 groups. In Fig. 1 the design B representing the type B (unilateral type with the right
branch receives blood from SMV) is probably a mistake as the blood is received from SV and
not from SVM. This should be corrected.
I did not understand if the portography was obtained by injecting the contrast medium from the
SV or from the SMV and if this can influence the results and thus the identification of the groups.
Other factors could be the size of the two veins as well as the size of the two portal branches.
Possibly the retrospective nature of the study is an important limitation in this sense.
2. The incidence of HE in the whole group is not reported (or I did not find it). The incidence
in the group (mixed or SV pattern) seems to be unusually low: less then 25%. There is any
explanation (stent diameters, pharmacological prevention). Please specify.
Moreover, the follow up to detect the episode of HE is not specifically reported. Please specify.
Were only the patients hospitalized for HE censored? Please specify. Again, the retrospective
nature of the study is relevant on this points especially because the incidence of post TIPS HE
is the main and point.
3. The diameters of the stent varied from 6 to 8 cm. No stent with 10 cm was used apparently.
Are these the nominal diameters of the stent used or the size of the dilatation obtained at the
end of the procedure?
In any case this parameter (the stent diameter or shunt size) could potentially have influenced
the results, but it was not taken into consideration in the multivariate analysis.
In conclusion, the papers, in my opinion, suggests an interesting hypothesis which should be
supported by a prospective study taken into considerations carefully the above points.