Powerpoint template for scientific posters (Swarthmore College)

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CT-guided Transgluteal and Transperineal
Percutaneous Biopsy and Drainage of Deep Pelvic
Structures Anatomy, Indications, Technique, and
Potential Complications T M Nguyen, W D Boswell,
P A Nedumaran, H G Pimenta, F M Wu, V Duddalwar
Department of Radiology, University of Southern
California, Los Angeles, California 90033
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USC
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Introduction Deep pelvic masses and abscesses
are a challenge for percutaneous intervention due
to vital organs that may prevent safe access.
Multiple approaches have been described, such as
transabdominal, anterolateral extraperitoneal,
transosseous, transgluteal, and transperineal.
These have all been proven to be safe and
effective for tissue biopsy, aspiration, and
drainage. This exhibit will explore the
relevant anatomy, technique, possible
complications, and technique modifications of CT
guided biopsy and drainage via the transgluteal
route through the greater sciatic foramen, as
well as abscess drainage via the transperineal
approach.
Potential complications Potential complications
can be prevented with meticulous technique and
careful route planning. These include pain,
hemorrhage, nervous system injury, bowel injury,
catheter malposition, and injury to other vital
structures (gynecologic and urologic).
Modifications Technique modifications may be
necessary to successfully target a lesion. These
include CT fluoroscopy, angling of the CT gantry,
use of a curved needle through a coaxial system,
injection of saline to displace vital structures,
and use of a blunt needle. CT fluoroscopy may be
useful for the exact positioning of a needle. It
has the potential to reduce procedure time and
provide more accurate positioning, but can
increase radiation exposure to both the patient
and the operator. Angling the CT gantry is
useful in targeting a lesion cephalad to the
sacrospinous ligament. It is technically more
difficult, however, to keep the needle in the
exact same angle as the gantry. Use of a curved
needle allows an additional option for difficult
to access lesions. Techniques to displace vital
structures may be useful to access a lesion. The
degree of displacement is a function of the
mobility of the structure. Injecting sterile
saline adjacent to a structure may displace it
enough to allow adequate access. This technique
may obscure the normal anatomy and/or target
making the procedure more difficult. Therefore
it is crucial to inject slowly and check progress
often. The use of a blunt needle (Inter-V
Hawkins Blunt Needle, Medical Device
Technologies, Inc, Gainesville, FL) is another
technique that may improve access to a lesion.
This system is supplied with a coaxial hollow
needle and both sharp and blunt inner stylets.
Torquing forces can be applied to the system with
the blunt stylet in place in an attempt to
displace the structure. In addition, the system
can be advanced with the blunt stylet in place
allowing blunt dissection of soft tissue,
decreasing the risk of injury to vascular or
nervous system structures.
Technique Transgluteal CT guided biopsy and
drainage shares many of the same principles as
percutaneous intervention by any other route.
This includes the appropriate indications,
contraindications and patient preparation.
However, aspects unique to the transgluteal
approach include patient positioning, route
planning, and equipment. Proper patient
positioning and maintenance of such is vital for
a successful procedure. The optimum position is
prone if the patient is able to tolerate it.
Patients who are recent post-operative, those
with relatively new abdominal wounds, or who are
on a mechanical ventilator pose a challenge.
These patients can be placed in an oblique or
lateral decubitus position. However, they must
be able to maintain that position. Hence, pain
control is very important. Local anesthesia is
used in all patients conscious sedation or
general anesthesia should be considered in select
cases. Devices such as pillows or straps can
also be used as appropriate to secure the
patients position. Although the safest route
through the greater sciatic foramen is at the
level of the sacrospinous ligament as close to
the lateral edge of the sacrum as possible, some
lesions require more superior or lateral course.
This is safe as long as all vital structures are
identified and are avoided.
A
B
C
Figure 5 Malpostioned catheter. (A) Prone CT
images through the pelvis in a patient status
post sigmoidectomy with a contained post-surgical
anastamotic leak (arrow). Bowel (arrowhead). (B)
Drainage catheter placed via the greater sciatic
notch, malpositioned into the bowel. (C) Drainage
catheter repositioned into presacral collection.

Anatomy Knowledge of the pelvic anatomy is of
the utmost importance due to susceptibility of
injury to vasculature, nerves, bowel, and
gynecologic or urologic structures. The
greater sciatic foramen is a space in the
posterolateral pelvis bound posteriorly by the
sacrum, anteriorly by the ischium, superiorly by
the ilium, and inferiorly by the sacrospinous
ligament. Contents of the greater sciatic notch
include the piriformis muscle, vessels from the
internal iliac system, and nerves of the sacral
plexus. The piriformis muscle originates from
the anterior surface of the sacrum and exits the
greater sciatic foramen to insert on the greater
trochanter of the femur. Superior to the
piriformis muscle exits the superior gluteal
vessels and nerves inferior to the muscle exits
the inferior gluteal vessels and nerves, internal
pudendal vessels and nerve, sciatic and posterior
femoral cutaneous nerves, and the nerves to the
obturator internus and quadratus femoris.   The
sacrospinous ligament is the inferior border of
the greater sciatic foramen. The major vessels
and nerves lie superior to this level, crossing
anterior to the piriformis muscle. Ensuring that
the needle or catheter traverses the sacrospinous
ligament decreases the chance of inadvertent
injury to these vessels and nerves.
A
B
C
Figure 6 Hemorrhage. (A) Post procedure image
after drainage catheter placement via the greater
sciatic notch. The ipsilateral muscles are
enlarged due to hematoma. (B) Digital
subtraction angiogram from the ipsalateral
internal iliac artery shows pseudoaneurysm of
inferior gluteal artery. Embolic coils were
placed. (C) Post-embolism angiogram reveals a
successful embolisation.
B
C
A
Figure 2 Coaxial needle biopsy. (A) Transverse
CT image through the pelvis in a rectal carcinoma
patient status post previous low anterior
resection, found to have abnormal soft tissue
adjacent to the anastamotic site (arrow). (B, C)
Patient is positioned right anterior oblique and
a coaxial needle system advanced through the
greater sciatic foramen at the level of the
sacrospinous ligament to biopsy this tissue.
Transperineal approach
c
c
A coaxial biopsy system is preferred to prevent
unnecessary repeat punctures and repositioning.
Drainages can be performed by the Seldinger
technique, which offers more control and
precision. A trochar technique is useful for
larger collections.
A
B
A
B
c
c
Figure 7 Transperineal drainage. (A) Transverse
CT image in a patient status post proctocolectomy
shows a large presacral fluid collection (f).
The collection is inaccessible from an anterior
approach. Although accessible through the
greater sciatic notch, the lack of any vital
midline structures from patients proctocolectomy
favors a midline transperineal approach. (B)
Saggital reconstruction shows a drainage catheter
in the fluid collection from a midline perineum
puncture.
a
a
a
C
D
Figure 4 Techniques to displace structures. (A)
An enlarged retroperitoneal lymph node (arrow)
medial to the psoas muscle. Descending colon (c)
lies along the course of proposed biopsy route.
(B) A Hawkins needle is positioned with the
sharp inner stylet, tip adjacent to the segment
of colon (c) to be displaced. (C) Sterile saline
in injected through the outer needle the segment
of colon is displaced anteriorly. (D) The blunt
needle is then placed through the hollow needle
and advanced through the retroperitoneal fat.
Lateral force is then applied to the needle
system, further displacing the segment of colon
anteriorly. A biopsy needle can now be advanced
to sample the lymph node.
Figure 3 Drainage catheter placement. Presacral
abscess (a) in a patient with rectal carcinoma
status post low anterior resection. Patient is
placed in a right lateral decubitus due to recent
surgery and colostomy. A drainage catheter is
place via the left greater sciatic foramen by a
trochar technique. Notice the catheter traverses
the sacrospinous ligament just lateral to the
lateral edge of the sacrum, avoiding vessels and
nerves.
b
References Butch RJ, Mueller PR, Ferrucci JT, et
al. Drainage of Pelvic Abscesses through the
Greater Sciatic Foramen. Radiology 1986
158487-491. Gupta S, Nguyen HL, Morello FA, et
al. Various Approaches for CT-guided Percutaneous
Biopsy of Deep Pelvic Lesions Anatomic and
Technical Considerations. RadioGraphics 2004
24175-189. Harishinghani MG, Gervais DA, Hahn
PF, et al. CT-guided Transcluteal Drainage of
Deep Pelvic Abscess Indications, Technique,
Procedure-related Complications,and Clinical
Outcome. RadioGraphics 2002 221353-1367. Harishi
nghani MG, Gervais DA, Maher MM, et al.
Transgluteal Approach for Percutaneous Drainage
of Deep Pelvic Abscesses 154 Cases. Radiology
2003 228701-705.
b
b
p
Figure 1 Normal anatomy. Transverse CT images
through the pelvis with intravenous and oral
contrast. Piriformis muscle (p), gluteal vessels
(arrows), bowel (b), sacrospinous ligament
(arrowheads).