Diagnostic ultrasound ( PDFDrive )

CHAPTER 17 Ultrasound-Guided Biopsy of Chest, Abdomen, and Pelvis 605
A
B
FIG. 17.6 Ultrasound-Guided Pancreatic Biopsy. (A) Contrast-enhanced CT scan shows a mildly dilated pancreatic duct with abrupt termination
in the head of the pancreas (arrow). No deinite mass is identiied on CT scan. (B) Ultrasound for guided biopsy shows a 19-gauge needle passing
through left lobe of the liver (L), with needle tip within a 2-cm hypoechoic mass in the head of the pancreas (arrows). The biopsy was positive for
adenocarcinoma.
of the pancreas or when EUS is unavailable. Biopsy is occasionally
required to document malignancy or diferentiate malignancy
from a benign condition, such as focal pancreatitis.
At our institution, most pancreatic biopsies are done with
CT guidance because depth of the pancreas and presence of
overlying bowel gas and hyperechoic abdominal fat can make
visualization of the needle diicult. Nevertheless, biopsy of
pancreatic masses in normal-size and slender patients can be
done accurately under ultrasound guidance (Fig. 17.6).
he gastrointestinal (GI) tract may be traversed when
biopsying the pancreas. With ultrasound, the stomach or bowel
is either displaced or compressed. Brandt et al. 4 demonstrated
the safety of traversing the GI tract (stomach, small bowel, colon)
in performing percutaneous biopsies in 66 procedures. Most of
these biopsies were performed using a 21-gauge needle, with no
complications related to the biopsy route in these patients.
A particular advantage of ultrasound over CT is the ability
to biopsy pancreatic masses in an of-axis plane, which is very
useful if overlying vessels are present on CT. Ultrasound-guided
biopsy has 93% to 95% accuracy, compared with 86% to 100%
accuracy for CT guidance. 4,62,63
In some series, the biopsy success rate for the diagnosis of
pancreatic carcinoma has been lower than the success rate for
the diagnosis of malignant lesions in other organs of the
abdomen. 4,64,65 his may be related to sampling error, because
signiicant desmoplastic reaction oten accompanies pancreatic
adenocarcinoma. By targeting the central hypoechoic portion
of the pancreatic mass, the clinician can improve the diagnostic
yield. In addition, core biopsy, either alone or in addition to
FNA, results in improved diagnostic performance compared with
FNA alone. 63
he diferentiation between benign serous and potentially
malignant mucinous pancreatic tumors can be diicult with
imaging alone. Unfortunately, cystic pancreatic malignancies are
diicult to accurately diagnose with percutaneous biopsy; a
deinitive diagnosis was achieved in only 60% of patients in one
study. 66 In biopsy of a cystic pancreatic lesion, it is critical to
obtain epithelial cells, either in the wall of the lesion or within
the cyst luid. Analysis of percutaneous luid aspirates from a
cystic lesion has also been proposed as an aid to distinguish
cystic neoplasms from pseudocysts. 66-68 A high amylase level is
consistent with a pseudocyst. he presence of tumor markers
with the cyst luid may also be helpful in suggesting a cystic
neoplasm.
he safety of percutaneous biopsy of the pancreas has been
well established, with a complication rate of 0.8% to 2%. 4,16,24,69
A historic review reported six deaths related to pancreas biopsy. 70
Five of these deaths were attributed to pancreatitis and one to
sepsis. No pancreatic cancer was found in either the biopsy
specimen or the postmortem examination of these patients,
suggesting an increased risk for developing pancreatitis ater
biopsy of normal pancreas. In this same large review of percutaneous
biopsies, 10 of 23 cases of needle track seeding occurred
ater the biopsy of pancreatic malignancies. For this reason, biopsy
may not be indicated in patients who are surgical candidates.
Kidney
Biopsy of the kidney is performed to assess intrinsic parenchymal
disease or to characterize a renal mass (Fig. 17.7). Although
there has been long-standing acceptance of renal mass biopsy
for suspected metastasis, lymphoma, abscess, or unresectable
suspected renal cell carcinoma, biopsy of potentially resectable
suspected renal cell carcinoma has historically been controversial
because of concerns regarding accuracy and safety as well as
questionable impact on patient management. 71 In recent years,
however, incidental detection of potentially benign small renal