Fig. 4
General overview of USPPB
A.
indications
The first indication is to confirm suspected malignancy in the pancreas.
According to NCCN guidelines for pancreatic adenocarcinoma,
histopathological confirmation is strongly recommended because all patients with unresectable pancreatic cancer should have confirmation before non-surgical treatment (1).
The second is to determine nature of indeterminate lesion in the pancreas,
and the last is to confirm mass suspected to be benign but in which benignity must be established.
B.
Contraindications
USPPB should be avoided in patients with uncorrectable coagulopathy,
poor cooperation,
and lack of safe path for biopsy.
In case of poor cooperated patient,
uncontrolled motion or irritability can occurs during USPPB,
which may increase risk of injury.
Lack of safe path for biopsy can be associated with high risk of overlying vascular injury around target lesion.
However,
biopsy path extending through liver,
spleen or bowel is possible and safe.
In case of mild coagulopathy secondary to aspirin use,
USPPB can be performed at least 5 days later after discontinuation of aspirin,
with confirmation of normal result on platelet function test.
Sometimes,
administration of appropriate blood product needs to be considered for USPPB.
C.
Preparation
NPO should be done in a patient during 6 hours before biopsy.
The operator should check patient’s condition such as coagulopathy,
medical history including taking an aspirin,
prothrombin time (PT),
activated partial thromboplastin time (aPTT) and platelet count (6).
Premedication (including sedatives & analgesics) is usually not necessary.
Informed consent should be obtained regarding the process of procedure,
risks,
alternatives and benefit,
before USPPB.
Intravenous access may be established before biopsy,
because parenteral administration of sedatives,
analgesics,
or other medications or fluid could be required during or after the biopsy procedure (5).
In addition,
in patient with increased risk of bleeding,
a larger or second intravenous access site should be considered.
D.
Training of How to breathe
Deep breathing should be avoided during USPPB,
especially when trans-hepatic or trans-splenic approach path is selected for biopsy (Fig.3).
Because migration distance of peritoneal organ along craniocaudal direction is longer during deep breathing than during shallow breathing,
the risk of laceration of vital organs could be increased during USPPB.
In fact,
as a result of deep breathing during USPPB,
vertical laceration of liver or spleen sometimes occurs along craniocaudal direction by inserted biopsy needle.
Thus,
shallow breathing during USPPB should be strongly recommended.
The operator should make patients understand the importance of shallow breathing during USPPB and warn the risk of vital organ injury during deep breathing.
How to decide approach path according to location of pancreatic tumors
Proper planning of percutaneous needle approach path
Anatomy of the pancreas
Fig. 5
Fig. 6
Position Change of Surrounding Anatomy
Peritoneal organs such as liver,
stomach,
jejunum,
and colon can be movable during respiration and change of patient position (Fig.3).
Factors affecting peritoneal organ movement are as follows; Respiration state (resting or expiration),
NPO,
compression by probe,
and patient position.
However,
retroperitoneal organ is not movable.
Fig. 7
Planning of USPPB path
Location of target
Fig. 8
Planning of Safe path
Location of target lesions within pancreas is the most important factor to decide safe path for biopsy.
The biopsy paths should be decided according to the location of target lesions within pancreas.
The planning of USPPB firstly needs to be established with cross-sectional images (CT or MRI) for seeking a safe path to target lesions and avoiding injury of important peritoneal structures such as major vessels,
colon,
small bowel,
stomach,
spleen and liver.
And then,
feasibility of biopsy path,
which was pre-determined on CT or MRI must be confirmed by US before biopsy.
Color Doppler US can be helpful to localize important vessels around pancreas that should be avoided (7,
8).
If planned biopsy path on CT or MRI is considered to be inadequate for biopsy on US,
another safe path should be sought using US.
The less important vessels are visualized through biopsy path,
the more biopsy path becomes safe.