We review the radiologic manifestations of extrapulmonary tuberculosis.
1. Musculoskeletal Tuberculosis
Skeletal involvement occurs in approximately 1%–3% of patients with tuberculosis.
- Tuberculous Spondylitis (fig1)
The spine is the most common site of osseous involvement by tuberculosis.
Spinal tuberculosis accounts for approximately 50% of cases of skeletal tuberculosis.
The most common location is L1.
Multiple vertebral bodies are typically affected; however,
single-level involvement sparing the adjacent disk spaces does occur
The disease process most often begins in the anterior part of the vertebral body adjacent to the end plate.
The disk space may then become involved via a number of routes.
Extension may occur along the anterior or posterior longitudinal ligament or directly through the end plate.
Less often,
posterior elements of the spine may become involved.
Collapse of a vertebral body,
particularly the anterior segment,
may result in tuberculous kyphosis.
Paraspinal infection may involve the psoas muscle,
resulting in psoas abscess which can extend into the groin and thigh.
Calcification within the abscess is virtually pathognomonic of tuberculosis.
CT and MR imaging are of great value in demonstrating a small focus of bone infection and the extent of the disease .
Differential diagnosis: metastatic disease and low-grade pyogenic infections such as brucellosis,
fungal infections,
and sarcoidosis have imaging findings similar to those of spinal tuberculosis.
However,
the diagnosis of tuberculosis is favored if a large,
calcified paravertebral mass and absence of sclerosis or new bone formation are noted.
Conversely,
intervertebral disk destruction is more characteristic of a pyogenic infection.
Characteristic features of brucellar spondylitis include gas within the disk,
a minimal associated paraspinal mass,
absence of kyphosis,
and a predilection for the lower lumbar spine.
- Tuberculous Arthritis (fig2)
Tuberculosis of the joints is characteristically a monoarticular disease.
The knee and hip are the most frequently affected.
Imaging appearance:
The Phemister triad: juxtaarticular osteoporosis,
peripherally located osseous erosions,
and gradual narrowing of the interosseous space is characteristic of tuberculous arthritis.
Differential diagnosis:
Fungal and rheumatoid arthritis.
Relative preservation of the joint space is highly suggestive of tuberculous arthritis; early loss of articular space is more typical of rheumatoid arthritis.
Tuberculous arthritis leads usually to fibrous ankylosis of the joint.
Bony ankylosis is occasionally seen,
but this sequela is more frequent in pyogenic arthritis.
Periostitis and osseous proliferation are generally more frequent and extensive in pyogenic arthritis than in tuberculous arthritis.
- Tuberculous Osteomyelitis
The femur,
the tibia,
and the small bones of the hands and feet are most commonly involved.
Typically,
the metaphyses are affected.
Radiographic findings: osteopenia,
osteolytic foci with poorly defined edges,
and varying amounts of sclerosis.
CT and MR imaging: the extent of the active infection and its complications.
2. Central Nervous System Tuberculosis
Arises from earlier hematogenous dissemination and may be located in the meninges,
brain,
or spinal cord.
Central nervous system tuberculosis may take a variety of forms,
including meningitis,
tuberculoma,
abscess,
cerebritis,
and miliary tuberculosis.
- Cranial Tuberculous Meningitis (fig3)
Abnormal meningeal enhancement typically most pronounced in the basal cisterns,
well seen at both CT and MR imaging corresponding to the gelatinous exudate.
Complications:
- Communicating hydrocephalus more likely than obstructive hydrocephalus,
- Ischemic infarcts commonly seen in the basal ganglia and internal capsule and result from vascular compression and occlusion of small perforating vessels.
- Spinal Tuberculous Meningitis
The MR imaging features of spinal tuberculous meningitis include cerebrospinal fluid loculi and obliteration of the spinal subarachnoid space with loss of outline of the spinal cord in the cervicothoracic spine and matting of the nerve roots in the lumbar region.
Contrast-enhanced MR images reveal nodular,
thick,
linear intradural enhancement.
Syringomyelia can occur as a complication of arachnoiditis and is seen as cord cavitation that typically demonstrates cerebrospinal fluid signal intensity on both T1- and T2-weighted images and does not enhance.
Parenchymal disease can occur with or without meningitis and usually manifests as tuberculomas.
Tuberculomas (fig 4,
5) may be solitary but are more commonly multiple.
The frontal and parietal lobes are the most commonly affected regions.
CT: rounded or lobulated masses with low or high attenuation.
They demonstrate homogeneous or ring enhancement and have irregular walls of varying thickness.
MRI: imaging features depend on whether it is noncaseating or caseating.
Noncaseating 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.
Parenchymal abscess and cerebritis: (fig 6) Rare forms of parenchymal tuberculosis.
Miliary central nervous system tuberculosis:(fig 4) usually associated with cranial tuberculous meningitis.
CT or MR appearance: numerous round,
homogeneously enhancing lesions less than 2 mm in diameter .
Differential diagnosis of cranial and spinal tuberculosis : other infectious or noninfectious diseases (eg,
sarcoidosis,
toxoplasmosis,
lymphoma,
pyogenic and fungal infections),
multicentric primary neoplasms (eg,
hemangioblastoma,
gliomas),
and metastases.
3. Abdominal Tuberculosis
- Gastrointestinal Tuberculosis
Ileocecal involvement is seen in 80%–90% of patients with abdominal tuberculosis.
Characteristic sign of tuberculosis: the Fleischner sign: Thickening of the valve lips or wide gaping of the valve with narrowing of the terminal ileum.
At double-contrast barium examination,
Shallow ulcers that are typically linear or stellate with characteristic elevated margins are seen.
The ulcers tend to be larger than those in Crohn disease and tend to be oval rather than round.
Moreover,
tuberculosis produces greater thickening of the bowel wall.
Fistulas and sinus tracts are rare.
In advanced disease,
characteristic deformities include symmetric annular “napkin ring” stenoses and obstruction,
shortening,
retraction,
and pouch formation.
The cecum classically becomes amputated.
CT: one-half of patients with gastrointestinal tuberculosis show circumferential thickening of the cecum and terminal ileum,
enlargement of the ileocecal valve,
and mesenteric lymphadenopathy.
However,
other findings such as asymmetry of the ileocecal valve,
thickening of the medial cecal wall,
exophytic extension and engulfment of the terminal ileum,
and massive adenopathy are more suggestive of tuberculosis
Differential diagnosis: amebiasis,
cecal carcinoma,
Crohn disease.
Peritoneal involvement is frequently seen in association with other forms of gastrointestinal tuberculosis.
Three types of tuberculosis peritonitis have been described:
- The wet type: large amount of free or loculated viscous fluid,
is the most frequent.
- The fibrotic-fixed type
- The dry or plastic type
Differential diagnosis:
carcinomatosis,
mesothelioma,
or nontuberculous peritonitis
- Hepatosplenic Tuberculosis (fig 7)
Hepatosplenic tuberculosis generally manifests in a micronodular (miliary) or macronodular (tuberculoma) form.
- The micronodular form usually occurs in association with miliary pulmonary tuberculosis.
On CT scans,
innumerable tiny,
lowattenuation foci may be seen.
- The macronodular form is rare.
On CT scans,
hypoattenuating lesions 1–3 cm in diameter or a single mass is seen in a diffusely enlarged liver or spleen.
MR imaging shows hypointense and minimally enhancing honeycomblike lesions on T1-weighted images.
On T2-weighted images,
the lesions are hyperintense with a less intense rim relative to the surrounding liver.
The differential diagnosis of the miliary form includes metastases,
fungal infection,
sarcoidosis,
and lymphoma.
The macronodular form can be mistaken for metastases,
primary malignant tumor,
or pyogenic abscess.
- Tuberculous Lymphadenitis (fig 8)
Lymphadenopathy is the most common manifestation of abdominal tuberculosis.
The nodes are usually multiple and large (2–3 cm of diameter).
The mesenteric and peripancreatic groups are the most commonly affected.
- Adrenal Tuberculosis (fig 9)
Bilateral and asymmetric involvement is common.
Soft-tissue masses with a nonspecific appearance are seen in the acute and subacute stages.
The appearance overlaps that of malignant processes.
Atrophy and calcification in the end stage of disease.
4. Genitourinary Tuberculosis
Genitourinary tuberculosis is the most common manifestation of extrapulmonary tuberculosis.
- Renal Tuberculosis.
(fig 10)
The earliest urographic abnormality is a “moth-eaten” calix due to erosion,
followed by papillary necrosis.
Poor renal function,
dilatation of the pelvicaliceal system due to a stricture of the ureteropelvic junction,
or destructive dilatation or localized hydrocalycosis related to an infundibular stricture may be seen.
Cavitation within the renal parenchyma may be detected as irregular pools of contrast material.
Cicatricial contracture of fibrotic parenchyma may lead to caliceal or renal pelvic traction.
Calculi may be present within the renal collecting system.
At end stage: Characteristic calcifications in a lobar distribution,
fibrosis and subsequent obstructive uropathy leading to autonephrectomy.
The differential diagnosis: acute focal bacterial nephritis,
xanthogranulomatous pyelonephritis,
small benign or malignant tumors.
First signs: Dilatation and a ragged irregular appearance of the urothelium.
Dilatation is primarily due to obstruction at the ureterovesical junction secondary to tuberculous cystitis and ureteritis.
In advanced disease: ureteral strictures,
ureteral shortening,
ureteral filling defects,
or ureteral wall calcifications may be seen.
The most common finding in tuberculous cystitis is reduced bladder capacity.
In advanced disease,
the bladder is small,
irregular,
and calcified.
The differential diagnosis: schistosomiasis,
cystitis due to cyclophosphamide,
radiation-induced changes,
and calcified bladder carcinoma.
- Female Genital Tuberculosis.
Salpingitis (often bilateral),
tubo-ovarian abscess
- Male Genital Tuberculosis.
- Tuberculous prostatitis:
hypoechoic areas with an irregular pattern in the peripheral zone of the prostate.
Contrast-enhanced CT shows hypoattenuating prostatic lesions,
which likely represent foci of caseous necrosis and inflammation.
Nontuberculous pyogenic prostatic abscesses have a similar CT appearance.
At MR imaging,
a prostatic abscess demonstrates peripheral enhancement.
This finding helps differentiate an abscess from prostatic malignancy.
In addition,
MR imaging shows diffuse,
radiating,
streaky areas of low signal intensity in the prostate (“watermelon skin” sign) on T2-weighted images.
- Tuberculous epididymitis or epididymo-orchitis has nonspecific imaging findings.
5. Lymph Node Tuberculosis
Lymphatic tuberculosis is more common among children.
Cervical or supraclavicular nodes are most commonly involved.
At CT,
nodes demonstrate peripheral enhancement with lowattenuation centers.
This appearance is highly suggestive but not pathognomonic of tuberculosis.
It must be differentiated from metastatic node,
lymphoma,
and inflammatory conditions.
6. Tuberculosis of larynx (fig 11)
In the present era,
in countries where TB is highly endemic,
almost all patients with laryngeal tuberculosis have been found to have radiological evidence of pulmonary TB and many of them may be sputum smear-positive.
Clinical features: Patients often present with hoarseness of voice.
Pain is also an important feature which may radiate to one or both ears and may lead to odynophagia.
The radiological findings of laryngeal tuberculosis depend on the stage and lesion extension,
and these correlate directly with the histological findings.
In the infiltrative stage,
there is focal thickening.
In the ulcerative stage,
the ulceration is not deep and rarely reaches the paraglottic spaces and the cartilage.
Perichondritis is sometimes noted (epiglottis,
arytenoids),
but calcifications are not common and the para-laryngeal fat spaces are usually spared.
The last stage is characterized by sclerosis.
Various radiological findings that have been described include edema alone,
an ulcero-infiltrative mass,
infiltrative and pseudo-tumoral appearance (66%); sub-glottic laryngitis (isolated swelling of the ary-epiglottic fold or even massive cartilaginous ulceration and,
sometimes,
chondritis or perichondritis); diffuse form; and tuberculoma (enormous ventricular vegetation with a large base that elevates the ventricular strip).
Laryngeal carcinoma is the main differential diagnosis. the two conditions may co-exist.
Their clinical features may overlap and the lesions may look similar.It is usually not possible to distinguish between them even on imaging.
7. Ocular tuberculosis (fig 12,
13)
Ocular involvement has described in 2 to 30 per cent of patients with tuberculosis and usually develops as a result of haematogenous dissemination.
While tuberculosis can affect all the part of the eye,
choroid is the most commonly affected structure.
Primary ocular tuberculosis though has been described is extremely rate.
Tuberculosis affects the eyelids infrequently.
Lupus vulgaris may spread to the face and involve the eyelid.
Conjunctival tuberculosis and lupus vulgaris are the common manifestations of primary tuberculosis while tuberculids and phlyctenulosis occur in postprimary tuberculosis.
Phlyctenulosis can involve conjunctiva,
cornea or lid margin.
Dacryoadenitis is a rare manifestation of tuberculosis.
It was
first described by Abadie in 1881.
CT scan or MRI shows an enlargement of the lacrimal apparatus and sometimes associated with sino-nasal wall thickening which contain areas of necrosis and necrotic cervical lymphadenopathies.