AJR 2005; 184:50-54
© American Roentgen Ray Society
Tuberculosis of the Pancreas: MRI Features
A. I. De Backer1,
K. J. Mortelé2,
P. Bomans3,
B. L. De Keulenaer4,
I. J. Vanschoubroeck3 and
M. M. Kockx5
1 Department of Radiology, Stuivenberg, Ziekenhuisnetwerk Antwerpen, Lange
Beeldekensstraat 267, Antwerp B-2060, Belgium.
2 Department of Radiology, Division of Abdominal Imaging and Intervention,
Brigham and Women's Hospital, Harvard Medical School, 75 Francis St., Boston,
MA 02115.
3 Department of Internal Medicine, Stuivenberg, Ziekenhuisnetwerk Antwerpen,
Antwerp B-2060, Belgium.
4 Intensive Care Unit, Royal Darwin Hospital, Rocklands 0810, TIWI, Northern
Territory, Australia.
5 Department of Pathology, Stuivenberg, Ziekenhuisnetwerk Antwerpen, Antwerp
B-2060, Belgium.
Received January 9, 2004;
accepted after revision April 28, 2004.
Address correspondence to A. I. DeBacker
(adelard.debacker{at}skynet.be).
Abstract
OBJECTIVE. The purpose of this study was to describe the MRI
features of tuberculosis of the pancreas.
CONCLUSION. Pancreatic tuberculosis can be focal or diffuse. If
focal, it presents as a sharply delineated mass located in the pancreatic
head, showing heterogeneous enhancement. Lesions are hypointense on
fat-suppressed T1-weighted images and a mixture of hypo- and hyperintense on
T2-weighted images. The appearances of common bile duct and main pancreatic
duct are normal. Diffuse involvement is characterized by pancreatic
enlargement with narrowing of the main pancreatic duct and heterogeneous
enhancement. Signal intensity abnormalities indicating diffuse involvement
include hypointensity on fat-suppressed T1-weighted images and hyperintensity
on T2-weighted images.
Introduction
The incidence of tuberculosis in the developed countries is increasing,
mainly among immigrants and immunocompromised patients. The predominant
manifestation of tuberculosis is pulmonary disease. The abdomen, however, is a
common site of extrapulmonary involvement. The most common sites of
involvement in the abdomen are the mesentery, small bowel, peritoneum, liver,
and spleen [1]. Tuberculosis of
the pancreas is considered to be uncommon, but its true incidence is unknown.
Tuberculosis of the pancreas usually occurs as a complication of miliary
tuberculosis and immunodeficiency, with isolated involvement of the pancreas
being exceedingly rare [2,
3]. The diagnosis usually is
not suspected before laparotomy unless there is evidence of tuberculosis
elsewhere or a relevant clinical history
[3].
We describe three patients with tuberculosis of the pancreas and discuss
the disease features seen on MRI.
Materials and Methods
Patients
We reviewed the medical records of three patients (mean age, 33 years;
range, 23–47 years) with pancreatic tuberculosis who were seen at our
institution over a 3-year period. All patients, one man and two women, were
immigrants. The findings at physical and histopathologic examinations, results
of laboratory tests, and MRI studies were available for all three
patients.
MRI Technique
MRI was performed with a 1.5-T magnet (Signa EchoSpeed Plus, GE Healthcare)
using a phased-array torso coil. Thin-section and thick-slab T2-weighted
single-shot fast spin-echo and T1-weighted fat-suppressed
gradient-recalled-echo images were obtained. Parameters used in T2-weighted
single-shot fast spin-echo imaging were TR/TE, infinite/60 and 4-mm section
thickness for the thin-slice technique and infinite/> 600 and 40-mm
thickness for single thick slab techniques. Parameters used in
gradient-recalled-echo imaging were 105/1.6; 256 x 512 matrix;
rectangular field of view to reduce the number of phase-encoding views; 5-mm
section thickness with a section gap of 2 mm or less; and flip angle of
60°. Contrast-enhanced gradient-recalled-echo images were obtained 25 sec,
60 sec, and 3 min after IV administration of 0.1 mmol of gadobenate
dimeglumine (Multihance, Bracco-Altana) per kilogram of body weight.
Results
Clinical Findings
Presenting symptoms in all three patients consisted of general weakness,
malaise, loss of body weight, and chronic lower back pain. Cervical
lymphadenopathy, fever, night sweats, hemoptysis, and productive cough were
present in two patients. Intermittent pain of moderate intensity localized to
the upper abdomen, dry cough, a fistula with purulent discharge in the ventral
wall of the abdomen, enlarged lymph nodes in the groin, and epileptic insult
associated with meningeal signs were present in one patient each.
Laboratory Analysis and Histopathology
In two patients, the biochemical analysis showed an elevated erythrocyte
sedimentation rate (67 and 23 mm/h; normal values, 0–20 mm/h) and
C-reactive protein level (10 and 1.69 mg/dL; normal values, < 1 mg/dL). In
one patient, elevated WBC (11.8 x 109/L; normal values,
3.7–10.1 x 109/L), platelets (456 x
109/L; normal values, 155–366 x 109/L), and
levels of alkaline phosphatase (174 U/L; normal value, 38–126 U/L), and
y-glutamyl transpeptidase (143 U/L; normal values, 12–43 U/L)
were noted. In all three patients, hemoglobin, total bilirubin, serum amylase,
and lipase levels were normal, and results of tests for the HIV antibody using
ELISA (enzyme-linked immunosorbent assay) methods were negative. The diagnosis
of tuberculosis was based on results of a highly specific polymerase chain
reaction–based assay for mycobacterial DNA on bronchioalveolar lavage
fluid (n = 1), lumbar puncture of cerebrospinal fluid (n =
1), and a surgical lymph node biopsy (n = 1) and was proven by the
growth of Mycobacterium tuberculosis on culture (n = 3). In
all patients, tuberculous involvement of the pancreas was confirmed by
improvement of abnormalities on abdominal CT and MRI after administration of
antituberculous chemotherapy.
MRI Fin`dings
A sharply delineated heterogeneous mass, located in the head of the
pancreas, was present in two patients (Figs.
1A,
1B,
2A,
2B, and
2C). The largest diameter of
the lesion was 4.0 and 2.5 cm, respectively. In these patients, unenhanced
T1-weighted fat-suppressed images showed the lesion as hypointense compared
with normal pancreatic tissue. On T2-weighted images, heterogeneous signal
intensities were noted, with areas of increased and decreased signal
intensities. On gadolinium-enhanced T1-weighted fat-suppressed
gradient-recalled-echo images, rim enhancement with focal areas of enhancement
within the lesions resulted in a multiloculated appearance. The biliary and
pancreatic ducts were unremarkable on MR cholangiopancreatography (MRCP)
images in both patients.
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Fig. 1A. —30-year-old man with tuberculous involvement of head of
pancreas and spleen and tuberculous spondylitis. T2-weighted single-shot fast
spin-echo image shows heterogeneous mass with increased and decreased signal
intensities. No dilatation of main pancreatic duct is seen.
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Fig. 1B. —30-year-old man with tuberculous involvement of head of
pancreas and spleen and tuberculous spondylitis. Gadolinium-enhanced
T1-weighted gradient-recalled-echo image obtained with fat suppression shows
sharply delineated heterogeneous mass with multiloculated appearance.
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Fig. 2A. —23-year-old woman with tuberculous involvement of head of
pancreas and "wet" peritoneal tuberculosis. T2-weighted
single-shot fast spin-echo image shows heterogeneous mass in head of pancreas
with central and peripheral hyperintensities. Obstruction and dilatation of
main pancreatic duct is not present.
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Fig. 2B. —23-year-old woman with tuberculous involvement of head of
pancreas and "wet" peritoneal tuberculosis. On unenhanced
T1-weighted gradient-recalled-echo image obtained with fat suppression, lesion
is hypointense compared with normal pancreatic tissue.
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Fig. 2C. —23-year-old woman with tuberculous involvement of head of
pancreas and "wet" peritoneal tuberculosis. Gadolinium-enhanced
T1-weighted gradient-recalled-echo image obtained with fat suppression shows
sharply delineated mass with peripheral and central areas of enhancement.
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In the third patient (Figs.
3A,
3B,
3C, and
3D), diffuse enlargement of the
pancreatic gland was associated with increased signal intensity on T2-weighted
images, with heterogeneous decreased signal intensity on T1-weighted
fat-suppressed gradient-recalled-echo images and with heterogeneous
enhancement after IV administration of gadolinium. MRCP showed diffuse
narrowing of the main pancreatic duct.
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Fig. 3A. —47-year-old woman with diffuse enlargement of pancreas and
abdominal lymphadenopathy caused by Mycobacterium tuberculosis.
T2-weighted single-shot fast spin-echo image shows diffusely enlarged,
hyperintense pancreas.
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Fig. 3B. —47-year-old woman with diffuse enlargement of pancreas and
abdominal lymphadenopathy caused by Mycobacterium tuberculosis. On MR
cholangiopancreatography image, diffuse narrowing of main pancreatic duct is
noted.
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Fig. 3C. —47-year-old woman with diffuse enlargement of pancreas and
abdominal lymphadenopathy caused by Mycobacterium tuberculosis.
T1-weighted gradient-recalled-echo image obtained with fat suppression shows
heterogeneously decreased signal intensity of pancreas.
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Fig. 3D. —47-year-old woman with diffuse enlargement of pancreas and
abdominal lymphadenopathy caused by Mycobacterium tuberculosis.
Slightly heterogeneous enhancement is seen on gadolinium-enhanced T1-weighted
gradient-recalled-echo image obtained with fat suppression.
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In all three patients, peripancreatic and paraaortic enlarged lymph nodes
were detected with signal intensity changes comparable to those of the
enlarged pancreas.
Discussion
Although its true incidence is unknown, pancreatic involvement is
considered extremely rare in patients with miliary tuberculosis. Auerbach
[2] reported 1,656 autopsies
performed during an 8-year period in patients who had tuberculosis.
Generalized miliary tuberculosis was noted in 297 cases, but pancreatic
involvement was noted in only in 14 of these cases. Paraf et al.
[4] also reviewed autopsy
studies of 526 cases of miliary tuberculosis. Pancreatic or peripancreatic
involvement was found in only 11 cases. Isolated tuberculous involvement of
the pancreas, in which the pancreas is the only site of reactivation of
tuberculosis, is even more uncommon
[3].
The rare occurrence of pancreatic tuberculosis has been proposed to be the
result of antibacterial pancreatic factors. Intraparenchymal injection of
M. tuberculosis causes destructive lesions only if an enormous amount
of inoculum is used. Furthermore, an antimycobacterial effect from pancreatic
extracts and purified lipases and deoxyribonucleases has been reported
[5].
The exact mode of transmission of M. tuberculosis to the pancreas
is not well understood, and several hypotheses have been proposed. Lymphatic
and hematogenous dissemination after pulmonary exposure has been theorized to
result in infection of the pancreas. Other possible mechanisms are abdominal
contamination by M. tuberculosis as a result of ingestion of infected
material from an active pulmonary focus with subsequent lymphatic spread;
reactivation of a previously latent pancreatic tuberculosis induced by
alcoholism, pancreatitis, treatment with steroids, or surgical manipulation;
and direct extension through the pancreas from adjacent organs such as
contiguous lymph nodes. Finally, a toxic-allergic reaction of the pancreas as
a result of generalized tuberculosis, probably reflecting a nonspecific
inflammatory host response to mycobacterial antigens rather than an infection
per se, has also been suggested
[5,
6]. In our patients,
concomitant pancreatitis or toxic-allergic reaction to systemic tuberculosis
seemed unlikely because laboratory evaluation showed normal levels of serum
amylase and lipase, and the signal intensities of the peripancreatic and
paraaortic lymph nodes were comparable to those of the affected portions of
the gland.
Pancreatic tuberculosis may have different clinical presentations. These
may include obstructive jaundice, gastrointestinal bleeding, acute or chronic
pancreatitis, portal vein obstruction, and pancreatic mass mimicking abscess,
carcinoma, and peripancreatic abscess
[5–7].
In addition, constitutional symptoms such as low-grade fever, night sweats,
weight loss, anorexia, nausea, acute or chronic abdominal pain, and malaise
may be present.
Focal tuberculous involvement of the pancreas has been reported to occur
most frequently in the pancreatic head, followed by the pancreatic body and
tail [8]. Diffuse pancreatic
involvement is exceedingly rare
[8]. In our series, a sharply
delineated heterogeneous mass, located in the head of the pancreas, was
present in two patients. Sonography and CT may show a focal hypoechoic or
hypodense lesion, often displaying internal echoes or densities
[9]. On contrast-enhanced CT,
this well-defined mass may show irregular margins with peripheral enhancement.
Areas of central enhancement may result in a multiloculated appearance. These
features, however, are nonspecific and may resemble those of inflammatory or
neoplastic cystic lesions of the pancreas. Rarely, diffuse enlargement of the
pancreas along with hypodense areas may be seen
[10]. The latter morphologic
abnormalities are also nonspecific and may be seen with pancreatitis and
lymphoma. Diffuse enlargement of the gland with pancreatic duct narrowing may
also be seen in patients with autoimmune pancreatitis.
To the best of our knowledge, no prior reports have focused on the MRI
findings of tuberculous involvement of the pancreas. In two of our patients,
T1-weighted fat-suppressed images showed the lesion as hypointense compared
with normal pancreatic tissue. On T2-weighted images, heterogeneous signal
intensities were noted, with areas of increased and decreased signal
intensities. On gadolinium-enhanced T1-weighted fat-suppressed
gradient-recalled-echo images, peripheral enhancement with areas of central
enhancement was noted, resulting in a multiloculated appearance. In our third
patient, diffuse enlargement of the pancreatic gland was associated with
increased signal intensity on T2-weighted images, heterogeneous decreased
signal intensity on T1-weighted fat-suppressed gradient-recalled-echo images,
and heterogeneous enhancement after IV administration of gadolinium.
Obstruction and dilatation of the common bile duct with dilatation of the
intrahepatic ducts and distention of the gallbladder have been reported to be
rare in patients with pancreatic tuberculosis
[7]. Furthermore, a normal
pancreatogram on ERCP, even if the tuberculous mass is centrally positioned in
the pancreatic head, has been reported to be typical in tuberculous pancreatic
involvement [11]. However,
displacement and stenosis of an otherwise normal main pancreatic duct without
prestenotic dilatation have been reported sporadically
[12].
In conclusion, we described the MRI features of involvement of the pancreas
by M. tuberculosis in three patients. The presence of a mass in the
pancreatic head or a diffuse enlargement of the gland in patients with miliary
tuberculosis or other types of abdominal tuberculosis should raise the
possibility of tuberculous involvement of the pancreas.
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Abstract
Introduction
