Diagnosis of extrapulmonary tuberculosis is often difficult.
However,
recognition and understanding of the radiologic findings of extrapulmonary tuberculosis can help in diagnosis.
A high level of suspicion is required,
especially in high-risk populations.
A positive culture or histologic analysis of biopsy specimens is still required in many cases for definitive diagnosis.
We review the radiologic manifestations of extrapulmonary tuberculosis: findings in the central nervous system, musculoskeletal,
abdominal,
lymph nodes and breast tuberculosis are discussed.
Epidemiology
Increased international travel and immigration have seen PTB rates increase even in traditionally low burden.
For these reasons,
today PTB is considered a public health emergency.
1.
Musculoskeletal Tuberculosis
- Skeletal involvement occurs in 1-3% of TB cases.
- 10-20% of all extra-pulmonary cases.
- Hematogenous spread from a primary source
- The most common are:
1.
Spondylitis
2.
Arthritis
3.
Osteomyelitis
Tuberculous spondylitis (Pott disease) Fig. 1 Fig. 2 Fig. 3 Fig. 4
-The most common site of skeletal TB is the spine (50%),
with lower thoracic and upper lumbar involvement,
especially on L1.
-It usually affects more than one vertebral body.
-It begins in the anterior part of the vertebral body adjacent to the end plate.
With the development of the disease,
it may involve the adjacent intervertebral disc,
subligamentous region and soft tissues.
-Subligamentous extension beneath posterior or anterior longitudinal ligaments may affect multiple vertebral levels continuously or skipped.
-Paraspinal infection may involve the psoas muscle,
resulting in psoas abscess,
may extend into groin and thigh.
-Calcification within the abscess is pathognomonic.
-Tuberculosis is characteristically associated with little or no periosteal reaction.
-Collapse and anterior wedging of a vertebral body may result in tuberculous kyphosis.
-Spinal tuberculosis spondylitis commonly causes bone destruction,
which can cause vertebra plana.
Tuberculous arthritis:
-It is a monoarticular disease
-The knee and hip are mainly affected.
-Metaphyseal spread to the joint,
characteristic of TB.
-Radiographic findings:
- Joint effusion
- Periarticular osteopenia
- Synovitis and other soft-tissues swellings
- Marginal erosions
- Varying degrees of cartilage destruction
-Phemister triad is characteristic:
- Juxtaarticular osteoporosis
- Peripherally located osseous erosions
- Gradual narrowing of the interosseous space
-Relative preservation of the joint space is highly suggestive.
-Fibrous ankylosis of the joint as a final result.
Tuberculous osteomyelitis
-Isolated osteomyelitis with no tuberculous arthritis association is rare.
-The femur,
the tibia and the small bones of feet and hands are commonly involved.
-The metaphyses are affected,
and the growth plate can be involved (This feature differentiates TB from pyogenic infection).
-Radiographic findings:
- Osteopenia
- Foci of osteolysis with poorly defined edges
- Varying degrees of sclerosis
-Cystic tuberculosis:
- It is an unusual subtype,
frequent in children
- Metaphyseal of long bones,
lytic lesions,
well-defined round and oval with a variable degree of sclerosis
-Tuberculous dactylitis
- Short,
tubular bones of the hands and feet
- Affects especially children
- It begins with fusiform soft tissue swelling and periostitis,
followed by bone destruction and formation of cyst cavities that seem to ballooned out the bone,
known as Spina Ventosa “wind-filled sail”.
2.
Central Nervous System Tuberculosis
-CNS tuberculosis usually results from hematogenous spread.
However,
it may result from direct rupture or extension of a subependymal or subpial focus (Rich focus) and may be located in the meninges,
brain,
or spinal cord.
-CNS tuberculosis takes various forms,
including meningitis,
tuberculoma,
abscess,
cerebritis,
and miliary tuberculosis.
Cranial Tuberculous Meningitis Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10
-Tuberculous meningitis is the most common manifestation of CNS tuberculosis.
-Early diagnosis is important to reduce morbidity and mortality.
-Tuberculous meningitis is usually due to hematogenous spread but can also be secondary to rupture of a rich focus or direct extension from CSF-infection.
Typical radiographic finding:
-Abnormal meningeal enhancement,
usually most pronounced in the basal cisterns.
-The most common complication of cranial tuberculous meningitis are:
- Communicating hydrocephalus.
- Ischemic infarcts in the basal ganglia and internal capsule and result from vascular compression and occlusion of small perforating vessels,
due to the vasculitis which complicates TBM
- Infarcts also occur adjacent to areas of severe meningeal and cisternal inflammation due to direct extension of disease into the parenchyma and are known as ‘border-zone’ infarction
Parenchymal Tuberculosis
-Usually manifests as tuberculomas.
-Tuberculomas may be solitary but are more commonly multiple.
-The frontal and parietal lobes are the most commonly affected regions.
-At CT,
tuberculomas appear as round or lobulated masses with low or high attenuation.
They demonstrate homogeneous or ring enhancement and have irregular walls of varying thickness.
- Target sign: central calcification or punctate enhancement with surrounding hypoattenuation and ring enhancement.
This finding is suggestive of,
but not pathognomonic for,
tuberculosis.
-At MR:
- Non-caseating tuberculomas are often hyperintense on T2-weighted images with homogeneous (nodular) enhancement.
- Caseating tuberculomas are isointense to markedly hypointense on T2-weighted images and exhibit rim enhancement.
Rare forms of parenchymal tuberculosis are abscess and cerebritis.
3.
Abdominal Tuberculosis
Abdominal Lymphadenopathy: Fig. 11 Fig. 12
-The most common extrapulmonary TB form is abdominal lymphadenopathy
-Main infection route: direct extension by contiguity
-Characteristics:
- Large-sized lymph node masses with inner calcifications and stranding of the adjacent fat.
Calcified adenopathies in the absence of malignancy should suggest TB aetiology
- They have a necrotic centre and different enhancing patterns (the most common: peripheral rim enhancement)
-The most common locations for the TB adenopathies are paraaortic,
periportal,
mesenterium and omentum.
-Differential diagnosis: Whipple’s disease
Gastrointestinal Tract Tuberculosis:
Main infection route:
- Hematogeneous
- By contiguity from adjacent affected organs
- Ingestion of infected sputum
- Lymphatic spread from infected lymph nodes
A.
Ileocecum and Colon: Most frequently bowel affected area,
due to a greater concentration of lymphoid tissue.
-There are different clinical presentations
- Ulcerative
- Hypertrophic
- Mixture between both
Imaging findings:
-Barium:
-Spasm and hypermotility with oedema +/- thickening of the ileocecal
valve.
-Linear ulcers that follow the lymphatic tissue.
- Advanced stages: ileocecal valve becomes incompetent and retracted due to mesocolon fibrosis
-CT
- Asymmetric wall thickening of the cecum and distal ileum,
adhesions and strictures + extensive lymphadenopathy
- Granulomas underneath the ulcers
Differential diagnosis: Crohn disease (smaller ulcers),
infectious (amebiasis).
B.
Esophagus and gastroduodenal:very unfrequent
Peritoneum
-Main infection route
- Hematogeneous
- By contiguity from adjacent affected organs.
-When present it usually indicates extensive disease,
with bowel and nodal involvement.
-3 Subtypes:
- Wet: most common (90%).
Associated with viscous ascitis (rich in cells and proteins)
- Dry: less common.
Peritoneal caseous nodules,
fibrosis and adhesions.
- Fibrotic: large masses envolving and thickening mesentery and omentum
Adrenal Glands
-Main infection route: hematogeneous
-Imaging findings:
- CT: enlarged (recurrent or active TB) or atrophic (cured TB) adrenal glands,
adrenal masses with necrotic centrum
-Differential diagnosis: haemorrhage
Liver and Spleen
-Main infection route: hematogeneous
-Imaging findings:
CT
- Micronodular: multiple small hypodense foci
- Macronodular: hepatosplenomegaly + hypodense foci or single hypodense mass with central/ thin peripheral enhancement on early stages.
More prone to abscess formation
- Presence of calcifications/granulomas indicate a more progressive lesion
MRI
- T1 hypointense and T2 hypo to hyperintense lesions with same contrast enhancement patterns as in CT
- Differential diagnosis:
-Micronodular: Infectious (fungi)
-Macronodular: infectious (abscess)
Genitourinary tuberculosis Fig. 13 Fig. 14
-Genitourinary TB accounts for less than 3% of pediatric TB cases.
-It is caused by hematogenous dissemination of the bacillus from distant active TB site.
-The genitourinary TB can present with dysuria,
flank pain and hematuria.
Both-symptoms and imaging can simulate other pathologies.
-It can affect the renal parenchyma,
the collecting system,
the bladder and/or the urethra.
When the bacillus achieves the kidney,
it can get inactive and can be converted to granuloma.
If the infection is reactivated,
granulomas can rupture to the calyces,
causing caseous necrosis,
cavitation and ulceration,
as well as disseminate through the collecting system,
leading inflammation followed by fibrosis,
scarring and calcification.
-Due to the inflammatory response,
we can see an enlarged kidney,
with heterogeneous echogenicity on ultrasound (US) and areas of hypoperfusion on CT and MRI.
-Tuberculous granulomas are visualized as nodules with poor enhancement on CT and MRI.
The collecting system can be dilated,
filled with debris or caseation and urothelial thickening.
- Chronic changes lead to calcifications,
scars,
areas of atrophy and fibrosis,
causing a decrease of contrast excretion.
Areas of stenosis (more recurrent in the distal third and the pyeloureteral junction),
secondary to fibrosis,
may be seen on CT or MRI.
4.
Breast Tuberculosis
-The breast tuberculosis is extremely rare.
-Young,
multiparous,
lactating women are commonly affected.
-The most frequently encountered clinical finding is a mass with or without ulceration.
5.
Eye Tuberculosis
-Ocular tuberculosis results from a hematogenous spread and can involve any part of the eye.
-Chorioretinitis and uveitis are the most common manifestations.