Diagnostic ultrasound ( PDFDrive )

1956 PART V Pediatric Sonography
A
2
3 1
Vein
A1
A2
A3
is used to guide the Chiba needle toward the bile ducts, which
lie in the portal tracts. he optimal diagnostic puncture site is
at the junction of the middle and peripheral thirds of the duct,
well away from the central portal veins and hepatic artery. If
the ducts are dilated, the needle can be guided directly into
the duct with the usual ultrasound techniques. Puncture should
be made at a site and at an angle that will allow conversion
of the track to a catheter drain should the diagnostic study
reveal bile duct stenosis or complete obstruction, especially in
liver transplant patients. Initial puncture of minimally dilated
bile ducts in pediatric liver transplant patients is one of the
most technically demanding ultrasound-guided procedures
(Fig. 56.15).
B
Vein
1
2
FIG. 56.12 Localizing the Needle Tip Near the Vein. (A) As the
needle is advanced toward the vein, the transducer is used in transverse
orientation and rocked back and forth (A1-A3) to sequentially track the
tip of the needle as it is advanced toward the vein. In the illustration,
the needle is depicted only as it is about to enter the vein (position 3).
(B) Trapping and puncturing the vein. The needle can easily slip to the
side of the vein if it is simply advanced, especially when attempting to
puncture a deep brachial vein. The loose soft tissue surrounding deep
veins allows the vein to slide out of the way of the needle. When the
tip of the needle is positioned correctly, adjacent to the anterior wall of
the vein (B1), gentle downward movement of the needle, without trying
to puncture the vein, will “trap” the vein with the needle tip (B2). Once
the vein is trapped, a quick thrust will puncture both walls. Careful
withdrawal usually results in venous blood return through the needle,
allowing successful peripherally inserted central catheter (PICC) line
placement.
passage of a guidewire to dislodge the obstructing debris (Video
56.2, Video 56.3).
Percutaneous Cholangiography
and Drainage
Percutaneous transhepatic cholangiography can be successfully
performed in children with or without duct dilation. Ultrasound
B1
B2
Mediastinal Mass Biopsy
Lymphoma is a common childhood malignancy oten manifesting
with a mediastinal mass. In many cases, cervical, abdominal
or axillary lymphadenopathy is seen at presentation enabling
histologic diagnosis by surgical lymph node biopsy. In some
cases, however, the patient has respiratory diiculty as a result
of tracheal compression and there are no convenient enlarged
lymph nodes available for biopsy. Many of these patients are
unable to lie lat without respiratory distress. he mediastinal
mass can enlarge very rapidly, such that a child who could lie
lat for the initial CT scan cannot lie lat a few hours later. In
these cases, ultrasound-guided mediastinal biopsy is oten the
safest option. Emergency radiotherapy and steroid administration
can also be used to shrink the mass, but these maneuvers
can result in inability to subtype the cells of the lymphoma,
which is becoming more important for treatment decisions and
prognosis.
hese patients are managed in the operating room in a semierect
position and need to be supervised and sedated by experienced
anesthesia staf. We typically use copious local anesthesia
and only minimal intravenous sedation, avoiding intubation if
at all possible.
Doppler ultrasound is used to locate and avoid the internal
mammary artery and vein. he mass is usually approached
through a paramanubrial intercostal space under direct ultrasound
guidance using a small-footprint sector probe. he great vessels
and lung must be clearly visualized before biopsy. Multiple samples
can be obtained with remarkably low risk of complication
(Fig. 56.16).
Appendiceal Abscess Drainage
Initial ultrasound-guided drainage of an appendix-associated
abscess is a well-documented procedure. Occasionally a secondary
abscess occurs ater interval endoscopic surgery for removal of
the appendix, usually caused by a retained or unrecognized
fecalith. Ultrasound guidance can also be used to drain these
recurrent abscesses. In one case, we were able to precisely target
the retained fecalith, drain the abscess, and then remove the
fecalith by a second interventional procedure using an Amplatz
biliary sheath (Cook, Bloomington, IN) and Fogarty balloon
retrieval of the fecalith through the sheath (Fig. 56.17, Video
56.4).
Text continued on p. 1961.