A Rare Cause of Flank Mass: Psoas Abscess due
to Extensive Primary Thoracolumbar Tuberculous
thoracolumbar vertebrae disease. The psoas abscess may be difficult clinically to diagnose because of
its rarity, insidious onset of the disease, and nonspecific clinical presentation. We report multidetector
CT and MR imaging findings of a psoas abscess secondary to primary tuberculous spondylodiskitis of
the spine from the T3 to L2 vertebrae, which presented as a flank mass.
Psoas abscess secondary to tuberculous spondylodiskitis is usually a complication of
challenge.1,3We report imaging findings of a case with exten-
scess, which presented as a soft-tissue flank mass beneath the
pinal tuberculosis (Pott’s disease) is common in endemic
regions.1-3Vague symptoms and signs make the clinical
A 21-year-old man was admitted to the hospital with a 1-month his-
and he was not febrile. Initial investigations showed nothing remark-
able with his blood count but an elevated erythrocyte sedimentation
mass with subcutaneous extension to the right flank (Fig. 1). To pre-
cisely define the borders of this lesion, we performed abdominal MR
ing the whole of the right psoas muscle, which was well-defined, lob-
ulated, and hypointense on T1-weighted and hyperintense on T2-
weighted images, with rim enhancement after paramagnetic contrast
taneous area in the right lumbar region over the iliac bone.
Because of a high index of suspected tuberculosis, radiologic ex-
nal MR imaging. On chest CT, there was no lung lesion suggesting
tuberculous infection except a pre- and paravertebral soft-tissue at-
tenuation (Fig 3). Between the levels of the third thoracic and second
Fig 1. Transverse abdominal sonogram, obtained inferior to the right kidney, shows a cystic
mass with fine internal echoes involving the right psoas muscle (arrows).
Received September 20, 2005; accepted after revision September 28.
From the Departments of Radiology (H.T.S., M.K., N.B.) and Orthopedic Surgery and
Traumatology (A.S.), Gulhane Military Medical School, 06018, Etlik, Ankara, Turkey.
Please address correspondence to: Murat Kocaoglu, MD, Gulhane Military Medical School,
Department of Radiology, 06018, Etlik, Ankara, Turkey; e-mail: firstname.lastname@example.org
Fig 2. Abdominal MR imaging.
A, Fat-saturated T2-weighted (TR/TE, 2100/90) axial MR image obtained through the iliac
fossa shows a multilobulated cystic lesion (star) involving almost the whole of the right
psoas muscle, extending to the right flank over the sacroiliac notch (arrowhead).
B, Noncontrast T1-weighted (TR/TE, 614/16) and (C) contrast-enhanced T1-weighted axial
images. The cystic lesion is low in signal intensity and shows rim enhancement after
contrast media injection.
AJNR Am J Neuroradiol 27:1735–37 ? Sep 2006 ? www.ajnr.org
lumbar vertebrae, a paravertebral abscess formation, hypointense on
T1-weighted and hyperintense on T2-weighted sequences with rim
enhancement after contrast media injection, was seen. There was no
MR imaging evidence of extension of the infection into the spinal
canal. Signal intensity changes within the thoracic and upper lumbar
vertebral body, such as low T1-weighted and high T2-weighted
patchy areas with intravenous contrast enhancement, were compati-
ble with osteomyelitis. The T6–7 disk space was narrowed, and bone
destruction was also noted at adjacent endplates (Fig 4A-C). On the
right side, the paravertebral abscess formation was in continuity with
the first MR imaging. The abscess was drained at surgery; then, anti-
tuberculous therapy was started. The patient was discharged and
asked to come for follow-up 1 month later.
The skeletal system, which is involved in 1%–10% of patients
with tuberculosis, is the most common extrapulmonary site
for tuberculous infection. Approximately half of those cases
manifest as spinal disease, and 75% are accompanied by
infrequently caused by digestive, urologic, or genital tubercu-
abscess forms secondary to destruction of the cortical bone
and elevation of the periosteum. In case of periosteum pene-
and may extend inferiorly as far as the groin and thigh under
along with nonspecific symptoms and signs makes the diag-
department of rheumatology for back pain.4Limping, a posi-
tive psoas sign, flexion deformity of the hip joint, fatigue, fe-
ver, night sweating, and weight loss also may be seen.6
lous infection; however, in our patient, there was no accom-
of a 4-month-old girl who presented with a multiloculated
cle and diagnosed as primary psoas abscess; however, Staphy-
Fig 3. Coronal reconstructed noncontrast multidetector CT image of the chest demonstrates
an extensive paravertebral soft-tissue mass and bone destruction at the adjacent endplates
of the thoracic sixth and seventh vertebrae.
Fig 4. Spinal MR imaging.
A, Coronal T2-weighted (TR/TE, 2500/120) thoracolumbar image shows widespread para-
vertebral soft tissue (arrowheads) and enlarged right psoas muscle (star) displacing the
right kidney. The abscess has almost completely replaced the psoas muscle, though a small
portion of it can still be noticed between the abscess and vertebral colon. High-signal-
intensity patchy areas on vertebral bodies are consistent with osteomyelitis.
B, T2-weighted and (C) contrast-enhanced T1-weighted (TR/TE, 580/14) sagittal scans.
Enhancing prevertebral soft-tissue lesions (arrowheads) and osteomyelitis with high signal
intensity on the T2-weighted scan, with patchy contrast enhancement on the T1-weighted
scan, are seen. Subcutaneous flank mass reveals high T2 and low T1 signal intensity with
rim enhancement (curved arrow). Midthoracic disk space narrowing suggesting diskitis and
adjacent endplate bony destruction are also evident.
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Abscess formations occur more frequently in cases of tu-
berculosis infections than in cases of pyogenic infections. The
mass presentation of abscesses, which may be huge as in the
present patient. On the other hand, early clinical presentation
of pyogenic abscesses allows timely diagnosis and treatment,
which decrease the incidence of mass formation secondary to
In conclusion, in endemic regions, diagnosis of psoas ab-
scess should not be simply put aside in patients with flank
mass, but its possible associations with the thoracic cavity, as
in our patient, must be investigated. Multiplanar imaging, es-
pecially MR imaging, is a useful diagnostic procedure in de-
aureus was confirmed asthecausative
fining subtle diskovertebral lesions and in detecting unsus-
pected paravertebral soft-tissue extension.
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AJNR Am J Neuroradiol 27:1735–37 ? Sep 2006 ? www.ajnr.org