Diagnostic ultrasound ( PDFDrive )

610 PART II Abdominal and Pelvic Sonography
A
B
FIG. 17.13 Abscess After Liver Mass Biopsy. (A) Transverse ultrasound image shows an 18-gauge biopsy needle in a 3-cm metastasis (arrow).
(B) Longitudinal image obtained 2 weeks later demonstrates a 6-cm debris-containing luid collection, anterior to left lobe of the liver, at biopsy
site. Subsequent aspiration and drain placement conirmed abscess.
underlying surgically correctable abnormality (e.g., perforated
bowel) is better treated with surgery.
Most percutaneous abscess drainage is performed to achieve
a cure without the need for surgery. In other patients, it is a
temporizing procedure that either postpones deinitive surgery
until the patient is stable (e.g., periappendiceal abscess drainage)
or permits a single-stage rather than a multistage surgery (e.g.,
peridiverticular abscess drainage). his is particularly desirable
in high-risk, medically complicated patients who present with
sepsis.
Contraindications to image-guided percutaneous catheter
drainage are all relative and are similar to those for percutaneous
biopsy. Although uncommon, lack of a safe route for percutaneous
drainage precludes the procedure. Unlike percutaneous biopsy,
in which bowel may be traversed without complication, luid
aspiration and percutaneous abscess drainage through bowel
should be avoided. Initial advancement of the drain through
normally contaminated bowel may seed a sterile luid collection,
resulting in iatrogenic infection. In addition, drain placement
through bowel may result in not only signiicant perforation but
also enteric istula.
Bleeding diathesis should be maximally corrected before
drain placement, and appropriate sedation (local and systemic)
should be given.
Imaging Methods
Selection of ultrasound or CT for guidance of aspiration and
drainage is inluenced by several factors, including the location
of the luid collection and the strengths and weaknesses of each
imaging modality, as discussed earlier. For example, a simple
paracentesis is best performed under ultrasound guidance (Fig.
17.14). More complicated drainage procedures in the retroperitoneum
or pelvis are best performed with CT guidance. More
supericial abdominal luid collections may be aspirated or
drained easily with ultrasound guidance. Obtaining a CT scan
before the procedure oten provides a more detailed view of
potentially deeper components to the collection and an anatomic
map for planning a safe access route.
FIG. 17.14 Ultrasound-Guided Paracentesis. Longitudinal image
shows a 5-French angiocatheter with side holes in the left lower peritoneal
cavity during a paracentesis.
In certain anatomic areas, such as the gallbladder, biliary
tract, and kidneys, combined ultrasound and luoroscopic
guidance of catheter placement may be preferred. he combined
use of ultrasound for initial needle placement and luoroscopy
for catheter placement, using the guidewire exchange technique
(Seldinger), optimizes the strengths of both guidance modalities.
Fluoroscopy can then be used to opacify the area drained and
conirm inal catheter placement and adequacy of drainage.
No single method of guidance for percutaneous drainage is
appropriate for all abdominal luid collections or abscesses. he
approach to any luid collection or potential abscess must be
tailored to the patient, procedure, and speciic circumstances.
Catheter Selection
Various catheters and introducing systems are available for
percutaneous abscess drainage; choice depends mainly on operator
preference. As with most interventional procedures, the clinician
or radiologist must be familiar and comfortable with the system