Diagnostic accuracy of Continuous Doppler Registration for early detection of hepatic artery thrombosis after liver transplantation

Liver transplantation is the only life-saving treatment for patients with
end-stage liver failure. About 7% of the transplanted grafts are lost mainly
because of hepatic artery thrombosis (HAT), for which an early
retransplantation (ReTx) must be performed. ReTx is associated with extra
morbidity and mortality of the recipients and adds an extra burden to the
shortage of suitable donor organs. ReTx can be avoided if vascular
complications could be detected early and adequate measurements can be taken to
revascularise the transplanted graft. Currently screening for HAT is performed
by routine percutaneous Doppler ultrasound (US)examinations at various time
points after transplantation. In case of suspected vascular complications
(CT)angiography is performed to confirm the suspicion. Percutaneous Doppler US
is associated with high false positive and false negative results, and the
delay in diagnosis by performing Doppler US at time intervals of several days
often precludes a successful revascularisation.
In the proposed study a miniature Doppler US probe will be located in close
apposition to the artery at the end of the operation, and a continuous flow
measurement (CDFM) will be performed by connecting the probe to an external
alarming and registration system. The accuracy of this CDFM will be compared to
the standard postoperative Doppler US examinations performed according to
protocol.


Intervention: During liver transplantation the miniature Doppler probe will be
placed in close apposition to the hepatic artery. During the first 10
post-operative days flow signals are continuously registered. Audible and
visible alarm signals will be generated when the signal drops below a certain
level. If the CDFM registers a HAT, an immediate Doppler US and (if also no
signal detected) a (CT) angiography will be performed for detecting vascular
complications. If HAT is then confirmed an urgent revascularisation operation
will follow.
Main study parameters/endpoints: (1) accuracy (true positive and true negative
rate) of the CDFM versus current protocol, (2) time gain obtained by immediate
recognition of HAT by the CDFM versus the scheduled next routine Doppler US,
(3) number of grafts with HAT which can be rescued by immediate surgical
revascularisation attempts
Burden and risks associated with participation: The minature probe has the
configuration and size of routinely placed drains in the abdomen after
transplantation. The disadvantage for the patient is the alarming and extra
investigational procedures if a (false) negative result is obtained. Children
will be included in the study because of the higher risk of HAT in pediatric
liver transplantation. Withdrawal of the probe is the same as withdrawal of
abdominal drains, and takes place at the ward.

Determine feasibility and reliability of CDFM in relation to the current
strategy of intermittent Doppler US examinations for detection of hepatic
artery thrombosis.

prospective observational study with invasive measurements

The risk of implantation and positioning of the minaiture Doppler probe is
considered to be very low. The catheter containing the Doppler probe and
cabling is one of the (at least) three catheters left in the abdomen after
liver transplantation. These consist of a bile drain, a feeding tube in the
small bowel and one ore more drains for removal of abdominal fluid (ascites).
The main disadvantage for the patient is the more frequent percutaneous Doppler
US examinations performed by the radiologist. This occurs if the CDFM system
detects a disturbance of the arterial flow. This is only disadvantageous for
the patient if the alarm is false, and the artey proves to be open on Doppler
US examination. If however the alarm detects an arterial problem which proves
to be correct the patient will have benefits from it, because an urgent
reoperation is performed with the aim to reopen the thrombosed artery and save
the liver graft..