Pulmonary Tuberculosis
Pulmonary tuberculosis can present as three types; primary,
postprimary (reactivation),
and miliary [2].
It is not always clear to differentiate between primary and postprimary tuberculosis.
However,
considering the findings associated with tuberculosis is more important than differentiation between tuberculosis types.
Primary tuberculosis
Primary tuberculosis is the term used for patients not previously exposed to Mycobacterium tuberculosis.
It occurs most commonly in infants,
children under five years of age and immunocompromised patients. The radiological findings are demonstrated with lymphadenopathy,
pulmonary consolidation,
and pleural effusion.
Lymphadenopathy
- The most common presentation of primary tuberculosis,
especially in children [3].
- Typical locations are the right paratracheal and hilar regions [3].
- Typical imaging findings of active stage are a low-attenuation center that is due to central caseous necrosis with peripheral rim enhancement on CT images [2].
Nodal calcification may develop in chronic stage (Fig. 1).
Fig. 1: A 54-year-old male with calcified lymph node in the chronic stage. Axial CT scan shows right paratracheal calcified lymph node (long arrow) with sequele fibrotic changes in the both upper lung segments (short arrows).
Parenchymal disease
- Typical manifestation is segmental or lobar consolidation.
- Presents in any lobe; especially in the lower and middle lobes.
- The presence of mediastinal lymphadenopathy with parenchymal consolidation can be helpful to distinguish from bacterial pneumonia.
- Contrary to general belief; cavitation may occur in a minority of patients with primary tuberculosis [4].
However,
cavitation does not exist in upper lung zone predominance,
in contrast to postprimary disease.
- After resolution of consolidation,
the radiologic scar can be calcified,
known as Ghon focus [3].
Pleural Effusion
- It is usually seen unilateral.
Septations may present.
- The mechanism of pleural effusion is usually related to hypersensitivity to tuberculous protein,
so isolation of the bacteria from pleural fluid is uncommon [2].
Postprimary tuberculosis
Postprimary tuberculosis occurs in patients with previously exposed to the infection.
Postprimary tuberculosis may manifest with parenchymal disease,
airway involvement,
and pleural extension.
Parenchymal disease
- Parenchymal involvement manifests as consolidation,
cavitation,
and centrilobular nodules.
- The common locations are the apical and posterior segments of the upper lobes,
the superior segments of the lower lobes.
- Consolidation is an early finding seen as patchy,
poorly defined.
- Cavitation is a significant finding of postprimary tuberculosis.
The typical appearance is a thick and irregular wall within areas of consolidation (Fig. 2).
They can be multiple,
and have large dimensions [3].
In case of the presence of air-fluid levels within a cavity,
it may be associated with bacterial superinfection.
Fig. 2: A 32-year-old male with cavitary tuberculosis. Axial CT scans show a) consolidations (long arrows) and b) multipl cavitary lesions in the apical segment of the right upper lobe (short arrows).
Airway involvement
- Bronchial wall involvement is characterized by bronchial stenosis and endobronchial spread of infection.
- The typical appearances of bronchial stenosis are hyperinflation,
segmental or lobar atelectasis,
mucoid impaction,
and obstructive pneumonia [3].
At CT,
bronchial wall involvement is usually seen as long segment narrowing with irregular wall thickening,
luminal obstruction,
and extrinsic compression.
- Centrilobular nodules and tree-in-bud opacities may exist due to the endobronchial spread of infection (Fig. 3).
Centrilobular nodules may be seen in the lower lobes.
The distribution of centrilobular nodules is different from miliary tuberculosis which is manifested as diffuse random-distributed nodules.
Fig. 3: A 44-year-old female with airway involvement by tuberculosis. Axial CT scan shows multiple centrilobular nodules and tree-in-bud pattern in the apicoposterior segment of the left upper lobe (arrow) due to the endobronchial spread of infection.
Pleural extension
- Pleural effusion is less common in postprimary than in primary tuberculosis,
however,
shows similar imaging features.
- After resolution,
residual pleural thickening and coarse calcification may occur [4].
Miliary tuberculosis
Miliary tuberculosis is a hematogenous dissemination of infection in lungs. It may present as both primary and postprimary tuberculosis.
The typical imaging findings are diffuse 2–3mm nodules in a random distribution [4] (Fig. 4).
The resolution of these nodules usually occurs within 2-6 months without sequelae.
Fig. 4: A 38-year-old female with miliary tuberculosis. Chest X-ray shows diffuse tiny nodules in both of lungs with lower lobes predominance.
*****Imaging pearls of pulmonary tuberculosis*****
- Central hypoattenuated lymphadenopathy may indicate primary tuberculosis.
- Do not forget; thick-irregular walled cavities are seen not only in tuberculosis but also in neoplasms,
autoimmune diseases,
vascular diseases,
other infections,
and congenital diseases.
Tuberculosis Involving the Central Nervous System
Central Nervous System (CNS) tuberculosis has higher prevalence in immunocompromised patients [3]. It usually results from hematogenous spread.
In addition,
direct rupture or extension of a subependymal or subpial focus are other pathways for spreading.
CNS tuberculosis can manifest as tuberculous meningitis,
parenchymal tuberculosis,
and spinal involvement [5].
Tuberculous meningitis
- It is the most common manifestation of CNS tuberculosis.
- It presents as a “basal meningitis”. The term is used because of the abnormal meningeal enhancement especially in the basal cisterns.
The finding is a relatively specific manifestation of leptomeningeal tuberculosis [5].
- Abnormal meningeal enhancement is also seen within the sulci over the cerebral convexities and in the sylvian fissures [4].
- The complications of tuberculous meningitis are hydrocephalus,
ischemic infarcts which are mostly within the basal ganglia or internal capsule region (Fig. 5).
Cranial nerve involvement may also occur.
Fig. 5: A 21-year-old male with cerebral tuberculosis. Axial T2- weighted images (a-b) shows left thalamic hyperintensity (arrow) and tuberculoma which appears as a round shaped lesion with high signal intensity in the right medial temporal lobe (arrowhead). Diffusion-weighted image (c) and ADC map (d) show restriction of diffusion in the left thalamus that indicates ischemic infarction (dotted arrows).
Parenchymal tuberculosis
Fig. 6: A 38-year-old female with cerebral and cerebellar tuberculomas. a-b) On axial T2- weighted images the lesions have high signal intensity with low- signal intensity centers (short arrows), and hyperintense vasogenic edema are also seen (long arrows). c-d) Contrast-enhanced T1-weighted images show rim-enhancing lesions both supratentorial and infratentorial.
Spinal tuberculous meningitis
- Tuberculous spinal meningitis presents with a CSF loculation and obliteration of the spinal subarachnoid space,
with loss of the outline of the spinal cord in the cervicothoracic spine.
After gadolinium administration,
nodular,
thick,
and linear intradural enhancement [5].
*****Imaging pearls of CNS tuberculosis*****
- Basal meningitis indicates tuberculosis.
- Hypointense-centered lesion on T2 weighted images should suggest tuberculosis.
- Combination of meningitis and parenchymal lesions suggests tuberculosis.
- The differential diagnosis of CNS tuberculosis; other infectious meningitis (coccidiomycosis may also cause basal meningitis),
carcinomatous meningitis,
neurosarcoidosis,
and neoplasms.
Head and Neck Tuberculosis
- Tuberculosis in the head and neck region occurs as nodal or extranodal.
- Nodal tuberculosis is the most common presentation of head and neck tuberculosis [3].
- Initially,
the involved nodes are homogenous,
but later they show low central attenuation due to the central necrosis.
Calcification may develop after treatment [7].
- Extranodal tuberculosis occurs more commonly in larynx,
temporal bone,
and pharynx.
- Laryngeal tuberculosis is usually seen as inflammatory soft tissue thickening and infiltration of the preepiglottic and paraglottic spaces,
without the presence of focal mass.
The true vocal cords,
the arytenoid cartilages,
and the interarytenoid spaces are frequently involved (Fig. 7) [7].
- Temporal bone tuberculosis has a similar radiologic appearance with infectious mastoiditides.
Soft tissue in the tympanic cavity and erosion of the ossicles are seen.
Destruction of the inner ear structures,
retroauricular abscesses,
and mastoid fistula may occur.
- Pharyngeal tuberculosis have nonspecific imaging findings which are similar to those of neoplasms. Oropharynx is the most affected site [7].
Fig. 7: A 55-year-old female with tuberculosis laryngitis. a) Axial fat-suppressed T2-weighted and b) contrast-enhanced fat-suppressed T1-weighted images show lesion in the interarytenoid space and bilateral posterior 2/3 of the vocal cords that was suspected to be a malign lesion during endoscopy. c) On diffusion-weighted images the lesion is hyperintense, mostly due to T2 shine-through effect. And d) on ADC map it has very high ADC values.
*****Imaging pearls of head and neck tuberculosis*****
- Tuberculous lymphadenitis can mimic many other diseases include metastatic,
granulomatous,
infectious and inflammatory diseases.
- Diffuse laryngeal involvement without the focal mass should suggest laryngeal tuberculosis.
Musculoskeletal Tuberculosis
The musculoskeletal system involvement is approximately 1-3% in cases of tuberculosis [3].
Musculoskeletal tuberculosis occurs in various presentations including spondylitis,
arthritis,
osteomyelitis,
tenosynovitis,
and bursitis.
However,
tenosynovitis and bursitis are extremely rare.
Tuberculous spondylitis (Pott Disease)
- The spine is the most frequent site of musculoskeletal tuberculosis [3].
- The lower thoracic and upper lumbar levels are affected more commonly.
Multiple contiguous or noncontiguous vertebrae are often inolved [8].
- The end plate of the anterior vertebral body is more commonly involved initially (Fig. 8).
The infection spreads to the adjacent intervertebral discs and destruction of the endplates begins.
Endplate irregularity,
osteolysis,
and vertebral sclerosis commonly occur.
- The involvement of an isolated vertebral body with sparing of the adjacent discs may also be seen rarely [3].
- As the disease progresses,
vertebral collapse and gibbus deformity may occur.
- Paravertebral abscesses are associated with tuberculous spondylitis.
Psoas abscesses also known as a Pott abscess in lumbar region may be seen.
[6].
- Calcification within the abscess,
especially in the healing period,
is virtually diagnostic for tuberculosis.
Fig. 8: A 65-year-old male with tuberculous spondylitis. a) Sagittal T2-weighted and b) Contrast enhanced T1 weighted images show inferior end plate irregularity of the lumbar 5 vertebra (short arrow). Intervertebral disc is seen as hyperintense (long arrow), and the cystic lesion in anterior epidural space indicates an abscess with periferal rim enhancement (arrowhead). c) After six months, sagittal lomber CT shows end plate irregularity, destruction (short arrow), and osteolysis (dotted arrow) of the lumbar 5 vertebrae. Note that the sclerosis is seen both lumbar 5 and sacral 1 vertebral bodies in chronic stage.
Tuberculous arthritis
- Tuberculous arthritis is characteristically monoarticular and primarily involves the large weight-bearing joints [3].
- The triad of Phemister is seen classically with tuberculous arthropathy; periarticular osteoporosis,
peripherally located osseous erosion,
and gradual diminution of the joint space.
Soft tissue edema,
marginal erosion,
and cartilage destruction are other findings.
However,
the diagnosis is difficult because of the overlapping with the imaging features of other arthritides.
Tuberculous osteomyelitis
- Tuberculous osteomyelitis often presents with tuberculous arthritis .
- The femur,
tibia,
and small bones of the hands and feet are most commonly affected sites [3].
- The metaphyses are typically involved.
In children,
the infection across the epiphyseal plate.
This feature can help to distinguish tuberculosis from pyogenic infection.
- The imaging findings include osteopenia,
soft tissue swelling,
minimal periosteal reaction,
osteolysis,
and erosions.
Sclerosis and sequestration are less frequently seen (Fig. 9).
- There are two forms of tuberculous osteomyelitis including cystic tuberculosis and tuberculous dactylitis that affects more commonly children [6].
- Cystic tuberculosis is usually multiple,
osteolytic,and well-defined.
The lesions do not have sclerotic margins in children; however,
they may have in adults [9].
- Tuberculous dactylitis affects the short tubular bones of the hands and feet.
These lesions typically appear as fusiform soft-tissue swelling with or without periostitis.
Gradual bone destruction and bone sequestration may also present [3].
Expansion of the bone with cystic changes is known as ‘spina ventosa’ [9].
Fig. 9: A 27-year-old female with ankylosis secondary to tuberculous osteomyelitis and arthritis. a) Coronal fat-supressed proton density and b) contrast enhanced T1- weighted images of the wrist show bone marrow edema of the distal radius, ulna, and carpal bone (thick arrows) as well as the contrast enhancement of the joint space (dotted arrow). c) On coronal precontrast T1- weighted image, bone destructions are also seen (thin arrows). d) After four months, radiograph of the hand shows loss of joint space and periarticular osteoporosis.
*****Imaging pearls of musculoskeletal tuberculosis*****
- Spondylitis with large paraspinal abscesses and vertebral deformity are suggestive of tuberculosis.
- The top differential diagnosis of tuberculous spondylitis are pyogenic spondylitis,
brucella spondylitis,
fungal spondylitis and spinal metastases [8].
- To distinguish tuberculous osteomyelitis from pyogenic infection,
involvement of the epiphyseal plate is an important finding in immature skeleton as well as the lack of massive periosteal reaction.
Abdominal Tuberculosis
The abdomen is the most common site for extrapulmonary tuberculosis [3].
Abdominal tuberculosis consists of lymphadenopathy,
tuberculous peritonitis,
gastrointestinal tuberculosis,
hepatosplenic tuberculosis,
adrenal tuberculosis and genitourinary tuberculosis.
Lymphadenopathy
- Lymphadenopathy is the most common manifestation of abdominal tuberculosis [3].
- They are characterized by multiple enlarged nodes with caseous necrosis that are seen as hypoattenuated-centers and hyperattenuated-rims on contrast-enhanced CT [10].
Tuberculous peritonitis
- Tuberculous peritonitis involves peritoneal cavity,
mesentery,
and omentum.
- The typical imaging findings are nodular thickening of peritoneum,
mesenteric and omental nodules,
and ascites as well as the low attenuated lymph nodes,
mural wall thickening in the terminal ileum and caecum [10].
- It mimics the peritoneal carcinomatosis.
Gastrointestinal tuberculosis
- Ileocaceal region is the most affected site in gastrointestinal tuberculosis (Fig. 10).
- The main presenting finding is concentric mural thickening,
however,
in the medial caecal wall,
eccentric pattern may occur.
Also,
skip areas of concentric mural thickening with associated luminal narrowing in the small bowel may indicate tuberculosis [3].
- Peritoneal involvement and lymph nodes with hypoattenuated-centers should raise suspicion of gastrointestinal tuberculosis.
- Esophagus,
stomach,
and proximal small bowel are rarely involved.
Their imaging findings are nonspecific.
Gastric tuberculosis usually presents in the distal part of the stomach and tends to complicate with a sinus or fistula [3].
Fig. 10: 51-year-old male with gastrointestinal tuberculosis. Axial (a) and coronal (b) contrast-enhanced CT scan show that caseous lymph node with low attenuated-center (thin arrow) and diffuse mural thickening in the terminal ileum (thick arrows).
Hepatosplenic tuberculosis
- Hepatosplenic involvement is demonstrated with two forms: micronodular-miliary and macronodular [10].
- Micronodular-miliary form is characterized by 0.5-2 mm nodules,
which may not be demonstrated on CT.
They are seen as hyperechoic foci on ultrasound [3].
- Macronodular form appears as a hypodense center with ill-defined margins on CT.
Calcification may occur in the chronic phase [3].
Adrenal tuberculosis
- Adrenal tuberculosis typically presents with bilateral adrenal involvement and may cause adrenal insufficiency [3].
- Imaging findings in acute period include bilaterally enlarged glands with hypoattenuating necrotic areas.
Dots of calcification may also be seen [3].
Genitourinary tuberculosis
- Genitourinary tuberculosis consists of renal,
ureteric,
bladder-urethra,
and genital tuberculosis.
- Renal tuberculosis is usually seen unilaterally.
Renal calcification,
which can be amorphous,
granular,
lobar and diffuse,
is the most common CT finding [10].
At intravenous urography,
moth-eaten calyx,
which is the earliest finding,
occurs due to erosions.
The disease progression might result in extensive papillary necrosis.
Caliectasis and hydronephrosis with irregular margins and filling defects due to caseous debris may usually present [3].
In addition,
irregular pools of contrast material appear due to the renal parenchymal cavitation [11].
When the disease progresses,
the stricture of renal pelvis or infundibulum causes dilated calyces (hydrocalycosis).
In end-stage tuberculosis,
lobar distributed-calcification which is named as autonephrectomy,
often develops [10].
- Ureteric tuberculosis occurs most commonly in the distal third of the ureter.
The wall thickening and contrast enhancementnare seen.
Additionally,
calcification may present in patients with chronic or healed-tuberculosis [11].
Corkscrew or beaded ureter may appear due to the chronic fibrotic structures.
- Bladder-urethra tuberculosis almost occurs due to the descendant spreading of infection.
When the bladder involves,
wall thickening and ulceration appear.
Then it becomes distorted; and,
finally,
small,
irregular,
calcified bladder occurs [11].
- Genital tuberculosis most commonly involves the fallopian tubes in women [3].
The most important imaging features are strictures and calcification in the fallopian tubes.
The other finding is a tuboovarian abscess which extends through the peritoneum.
Endometrial involvement is resulted in endometrial adhesions [3].
In men,
seminal vesicle and prostate gland are more commonly involved sites than testis and epididymides [3].
The findings are nonspecific,
calcifications may suggest tuberculosis.
*****Imaging pearls of abdominal tuberculosis*****
- The lymph nodes with hypoattenuating center should suggest tuberculosis.
- The skip areas of concentric mural thickening in the small bowel,
especially in ileocaecal region,
are associated with not only inflammatory bowel disease but also abdominal tuberculosis.
- Calyceal involvement with irregular contour may relate with renal tuberculosis.
- Strictures and adhesions in fallopian tubes may indicate tuberculosis in a patient who presents with salpingitis.
Tuberculous aneurysm
- The most well-known aneurysm associated with tuberculosis is pulmonary artery pseudoaneurysm that is known as “Rasmussen aneurysm”.
- Rasmussen aneurysm occurs due to the erosion of the pulmonary arterial wall which is caused by inflammation of the contiguous tuberculous cavitary lesion [12].
- Contrast-enhanced CT or CT angiography show contrast material filling the aneurysm with surrounding by cavitary consolidation.
- Tuberculosis may also cause an aortic aneurysm (Fig. 11).
- Mycotic aneurysm of the aorta by tuberculosis is extremely rare.
It may occur by mostly direct extension from adjacent lesions such as infected lymph nodes,
empyema,
or paraspinal abscess and by hematogenous contamination through the vasa vasorum or lymphangitic dissemination [13].
- Enlarged lymph nodes with central hypoattenuating areas usually accompany the aortic aneurysm.
Fig. 11: A 68-year-old female with tuberculous aneurysm of the aorta. Axial (a) and coronal (b) contrast-enhanced CT scan show tuberculous aneursym. c) Chest X-ray of the same patient shows diffuse tiny opacities consistent with miliary tuberculosis.
*****Imaging pearls of tuberculous aneurysm*****
- Vascular structures adjacent to the involved lymph nodes or cavitary lesion should be evaluated very carefully.
Cardiac tuberculosis
- The pericardial involvement is the major finding of cardiac tuberculosis [3].
- Pericardial thickening of more than 3mm,
which may become focal or diffuse,
is the common presentation of pericardial involvement [3].
- The associated findings of pericardial tuberculosis are mediastinal lymphadenopathy,
bilateral pleural effusions,
and the deformity of the interventricular septum [3].
- Myocardial involvement is rarely seen.
Tuberculosis foci in myocardium can present as miliary or tuberculomas [3].
*****Imaging pearls of cardiac tuberculosis*****
- Pericardial thickening of more than 3mm should suggest tuberculosis.