It includes both superficial and deep lymph node tuberculosis. It is the most frequent site of extrapulmonary tuberculosis, and is statistically the most frequent in children and adolescents, with superficial lymph node tuberculosis in the neck (68%-90%). The next most common site is the axilla. Deep lymph nodes include the thoracic, abdominal and pelvic cavities. Mediastinal lymph node tuberculosis and abdominal lymph node tuberculosis have been reported more often in recent years, and the misdiagnosis rate is higher.
Pathogenesis and pathology
Due to the decreased immune function of the body, infection can develop through lymphatic or hematologic routes, and direct invasion of mediastinal and intra-abdominal lymph nodes by adjacent organ lesions is also common. The pathological changes are characteristic of different anatomical sites and are described as follows.
I. Tuberculosis of the cervical lymph nodes
(A) Pathogenesis
1. Lymph node infection mostly comes from the head and neck organs, usually from the oropharynx and throat, causing upper cervical lymph node tuberculosis; tuberculosis bacilli from the mediastinum can spread upward to involve the cervical lymph nodes, supraclavicular and deep cervical lower group lymph nodes, and patients often have intrathoracic tuberculosis lesions, mediastinal and tracheal lymph node tuberculosis at the same time.
2, hematogenous infection through hematogenous dissemination to the neck lymph node tuberculosis lesions, is a local manifestation of systemic tuberculosis, often bilateral lymph node lesions.
3, reignition of lymph node tuberculosis lesions.
(B) Pathology
The pathological changes of tuberculous lymphadenitis can be divided into four stages: (1) proliferation of lymphatic tissue, forming nodules or granulomas; (2) liquefaction of caseous necrosis in lymph nodes; (3) destruction of lymph node envelope, fusing with each other and merging with perilymph node inflammation; (4) penetration of caseous material into surrounding soft tissues to form cold abscesses or sinus tracts. Generally, there are four types of lymph node tuberculosis pathology: caseous tuberculosis, proliferative tuberculosis, mixed tuberculosis, and unresponsive tuberculosis.
Mediastinal lymph node tuberculosis
After infection by Mycobacterium tuberculosis through the respiratory tract, inflammatory lesions are formed in the lungs, which become the primary foci, and Mycobacterium tuberculosis flows into the hilar lymph nodes and mediastinal lymph nodes along the lymphatic vessels, causing inflammatory enlargement or caseous necrosis in several groups of lymph nodes. If the immunity of the body is low, or if the number of invading tubercle bacilli is high and the virulence is strong, and if the diagnosis and treatment are not timely, the condition will deteriorate rapidly, and the enlarged lymph nodes will become caseous and necrotic, liquefy, and form mediastinal proliferative lymph nodes or tuberculous abscesses, and the enlarged lymph nodes or abscesses will compress the adjacent tissues and organs, producing corresponding symptoms and signs.
III. Intra-abdominal lymph node tuberculosis
Although the disease is often a part of systemic tuberculosis, it is not uncommon to develop alone. Patients who are old and frail, or who have reduced immunity such as diabetes or AIDS, are more susceptible to infection. The routes of infection are hematogenous and intestinal, with the latter being the most common, caused by lymphatic dissemination of Mycobacterium tuberculosis through the small intestine and colon or by direct invasion of adjacent organs. Intra-abdominal lymphatic tuberculosis is mostly seen in young and middle-aged people. The pathological changes mainly include ① granulomatous lymphadenitis; ② caseous necrosis of lymph nodes; ③ lymph node abscess; ④ lymph node calcification.
Clinical manifestations
I. Cervical lymphatic tuberculosis
(a) Systemic symptoms Generally, there may be no systemic symptoms, but in more severe cases, symptoms of tuberculosis toxicity may appear, such as low fever, night sweats, weakness, poor appetite, etc.
(B) Local symptoms The lymph nodes in the neck are mostly found in the right neck and both necks, with local swelling, pain and pressure pain. According to the distribution, they are divided into upper cervical lymphatic nodules, lower cervical lymphatic nodules and scattered lymphatic nodules, which are caused by the upward spread of lymphatic nodules in the upper respiratory tract and chest cavity and hematogenous infection, respectively. According to the development of disease, there are four types: (1) nodular type: slow onset, variable number, no adhesion with surrounding tissues, scattered, hard; (2) infiltrative type: obvious lymph node peri-inflammation, often fused into clusters, adhesion with surrounding tissues and skin, highly swollen masses can be palpated, and caseous necrosis can begin to appear in the center; (3) abscess type: the center of the caseous necrotic lymph nodes soften, forming abscesses, and localized when combined with secondary infection Redness, swelling, heat and pain appear. (4) Ulcerated type or ulcerated fistula type: the abscess ruptures or the wound does not heal after incision and drainage, forming a fistula or ulcer.
Mediastinal lymph node tuberculosis
Mediastinal lymph node tuberculosis generally has a slow onset, but a few patients may have an acute onset, and the main symptoms are systemic toxicity and compression of the mediastinal lymph nodes.
(a) The chronic onset of the disease can be characterized by low fever in the afternoon, malaise, night sweats, depression and other common symptoms of tuberculosis intoxication, while the acute onset of the disease can be characterized by chills, high fever, body temperature up to 40℃ or more, accompanied by headache, body aches and other symptoms, which are often misdiagnosed as epiglottitis, influenza, sepsis, lymphoma and so on.
(B) Compression symptoms and signs Different compression symptoms can be produced according to the different groups of lymph nodes in the mediastinum and the severity of the lesions after involvement.
1, paratracheal, tracheal and bronchial lymph node enlargement can compress the trachea and main bronchus and cause respiratory distress, especially in young children the symptoms are more obvious, manifested as inspiratory dyspnea, cyanosis, trigeminal signs in severe cases, long-term pressure on the trachea and bronchus, local mucosal congestion, edema, tracheal wall ischemia, softening, necrosis or lymph node abscess directly penetrate the tracheal wall and form tracheal and bronchial lymphatic fistula; if the fistula opening is small, manifested as irritating cough, can be formed. If the fistula is small, the cough can be irritating, and caseous necrotic material can be coughed up; if the fistula is large, a large amount of caseous material collapsing into the trachea can cause asphyxia; in addition, compression of the main bronchus can cause total pulmonary atelectasis, and compression of the lobar and segmental bronchus can cause lobar atelectasis or segmental atelectasis.
2.Esophageal swallowing difficulty can be caused by compression of the esophagus by enlarged paraoesophageal lymph nodes, and esophageal stenosis by external pressure on barium swallowing examination, and esophageal perforation can occur by long-term compression, and the compression symptoms can be relieved after caseous material is discharged through the esophagus.
3. compression of the laryngeal nerve by enlarged lymph nodes or abscesses may cause ipsilateral vocal cord paralysis and hoarseness; compression of the phrenic nerve may cause recalcitrant eructation; compression of the sympathetic nerve may cause Horner’s syndrome.
4. compression of large blood vessels can lead to superior vena cava compression syndrome; compression of the aorta can lead to pseudoaneurysm.
5.Sometimes mediastinal lymph node tuberculosis can spread upward to cause cervical lymph node tuberculosis; abscess penetrating the mediastinal pleura can form abscess thorax, and penetrating the sternum or subsurface skin to form chronic sinus tracts, which will not heal for a long time.
III. Intra-abdominal lymph node tuberculosis
According to the location of intra-abdominal lymph node tuberculosis and the scope of involvement, there are mesenteric lymph node tuberculosis and lymph node tuberculosis outside the mesentery.
(I) Mesenteric lymph node tuberculosis: It is mostly seen in children and adolescents, with a slow onset, and mostly coexists with intestinal tuberculosis, tuberculous peritonitis, and pelvic tuberculosis. When only mesenteric lymph node tuberculosis with extensive or limited enlargement is present without intestinal tuberculosis, tuberculous peritonitis, or pelvic tuberculosis, the diagnosis of mesenteric lymph node tuberculosis is favored, but is uncommon. Local symptoms often begin with abdominal pain and diarrhea. The abdominal pain is mostly located around the umbilicus, left upper abdomen, right lower abdomen with limited fixed occult, dull or colicky pain, with paroxysmal or intermittent episodes. Diarrhea alternates with constipation, and constipation is also present. Due to calcification or enlarged lymph node fusion masses compressing the intestinal canal, causing a series of symptoms and signs such as intestinal obstruction or incomplete obstruction, mutual adhesions can be palpable masses, not easy to move with pressure pain, and ascites with mobile turbid sounds, such as secondary infection to form a mixed abscess, it is easy to break into the abdominal cavity with acute abdominal manifestations.
(B) Lymph node tuberculosis outside the mesentery: according to the route of infection, there are two types of lymph node involvement: hematogenous and non-hematogenous, and non-hematogenous lymph node involvement is more limited, mainly located in the mesenteric root, with mesenteric lymph node tuberculosis being the most common, but large and small omentum, hepatoportal area and around the pancreas can be involved, and posterior peritoneal lymph nodes are less involved, and mostly located in the lymph nodes above the lumbar 2-3 conus, which is related to lymphatic drainage. This is related to lymphatic drainage. The hematogenous form is part of the systemic tuberculosis infection and is often combined with pulmonary tuberculosis and intra-abdominal organ tuberculosis. Intra-abdominal lymph nodes are involved and may often involve the retroperitoneal lymph nodes below the level of the lumbar 2-3 cone. Lymph nodes above and below the larger vessels in the retroperitoneal space can also be involved by lymphatic spread of tuberculosis in the pelvic genitalia.
Clinical presentation Most patients have a long, slow progression of the disease, or may have an acute onset and may not have a history of tuberculosis. The clinical manifestations vary widely and can be mainly systemic, lacking abdominal signs, often with varying degrees of fever and night sweats, or abdominal manifestations can be prominent, with abdominal pain, abdominal pressure, some palpable masses, and gastrointestinal complications such as intestinal obstruction, intestinal fistula, gastrointestinal bleeding, and may be accompanied by tuberculous peritonitis. It is worth noting that because intra-abdominal lymph nodes tend to fuse and adhere, they are often misdiagnosed as tumors clinically due to the presence of swelling or occupying lesions detected by ultrasound or CT examination. In particular, peripancreatic, splenic portal, hepatic portal, duodenal ligament, gallbladder and other peripheral lymph node tuberculosis, caseous liquefaction fusion, perilymph node inflammation rupture or adhesion, which may lead to limited peritonitis, jaundice if the common bile duct is compressed, portal and hepatic vein thrombosis, regional portal hypertension and other complex clinical manifestations.
It is common for patients to have both superficial and deep lymph node tuberculosis, and to have lymph node enlargement in multiple locations throughout the body. If the mediastinal lymph nodes are enlarged and the intra-abdominal lymph nodes are enlarged, the possibility of tuberculosis should be considered and relevant tests should be performed to clarify the diagnosis.
Imaging examination and special examination
I. Cervical lymph node tuberculosis
(A) X-ray examination. Find lymph node calcification, lung or other parts of the tuberculosis lesions to help the diagnosis.
(b) Ultrasound examination. ultrasound shows hypoechoic nodules, often multiple, multiple round or oval lymph nodes clustered and fused into a mass, some into cysts, which may have higher echogenic areas of coagulation necrosis, case liquefaction around the peripheral edema may show unclear surrounding contours, and if a cold abscess is formed, the texture is uneven. A heterogeneous hypoechoic zone is presented.
(iii) CT examination. Enhanced CT can clearly show the number and location of lesions and different types of enhancement. The types of enhancement include homogeneous isointense enhancement, thin ring-like peripheral enhancement and inhomogeneous enhancement, and each type can exist simultaneously. The imaging characteristics are “three more”, namely, more lesions, more invaded areas, and multiple pathological changes exist simultaneously.
(D) Lymph node aspiration or biopsy and bacteriological examination. Lymph node puncture or biopsy is an important method to confirm the diagnosis of cervical lymph node tuberculosis. The specificity can be more than 70% or 90%, respectively. Antacid staining and culture of tuberculosis bacilli are the primary diagnostic tools.
Mediastinal lymph node tuberculosis
(a) X-ray examination. X-ray chest radiographs of mediastinal lymph node tuberculosis show: (1) the mass is mostly located in the middle mediastinum, often unilateral, and is more common on the right side; (2) the mass is nodular, and some of them may have foci of calcification; (3) it may be accompanied by tuberculosis lesions; (4) the enlarged lymph nodes in the upper mediastinum are often found to be widened in the mediastinal shadow in the posterior anterior chest radiograph; (5) the enlarged paratracheobronchial lymph nodes are semicircular or shuttle-shaped, and the longitudinal diameter is larger than the transverse diameter; (6) the enlarged lymph nodes under the bulge The angle of tracheal bifurcation may be increased. Since a variety of diseases can cause mediastinal lymph node enlargement, it is difficult to diagnose mediastinal lymph node tuberculosis by X-ray images alone.
(B) CT examination. The enlarged lymph nodes are mostly in the space between the posterior vena cava and the trachea, next to the aortic arch, above and below the tracheal bifurcation, and in the hilar region. The enlarged lymph nodes are single or multiple, which can be fused and irregularly shaped. The density of lymph nodes is more uniform when scanning, and the central part is seen to be less dense than the surrounding ones.
(iii) Fiberoptic bronchoscopy. When mediastinal lymph node nodules compress the tracheobronchus or form a tracheal fistula, fiberoptic bronchoscopy is of greater significance, and if there is more experience, mediastinal lymph node biopsy via fiberoptic bronchoscopy after training is of great diagnostic help.
(iv) Mediastinoscopy. Mediastinoscopy is mainly used for lymph node enlargement in the paratracheal, inferior ramus and the beginning of the two main bronchi. It is difficult to do this examination for anterior or posterior mediastinal masses. It is mainly used for biopsy to obtain a pathologic diagnosis. Mediastinoscopic incision and drainage can also be used for patients who have formed cold abscesses.
III. Intra-abdominal lymph node tuberculosis
(a) X-ray examination. Abdominal plain film shows diffuse speckled and plaque calcified foci, or limited speckled calcified foci, as well as intestinal obstruction, multiple step-like fluid levels in the jejunum. Tuberculosis of the liver, spleen, pancreas, kidney, adrenal glands and other organs, or with tuberculous peritonitis, can help in the diagnosis.
(ii) Ultrasound examination. Calcified lymphatic tuberculosis presents with speckles and plaques of strong echogenicity. Non-calcified lymphatic tuberculosis mostly shows multiple lymph nodes enlargement, with small lesions showing uniform hypoechogenicity, while large lesions or multiple lymph nodes fusion show inhomogeneous echogenicity, or anechoic areas may be found.
（CT scan can detect the extent and distribution of intra-abdominal lymph node involvement, clarify the peripheral situation and fusion of lymph nodes, and detect calcified lymph nodes. Enhanced CT is more valuable for diagnosis, showing the lesion and its involvement, distribution, lymph node periphery, fusion changes, and secondary signs of focal lesions more clearly. Circumferential enhancement or wreath-like enhancement of lymph nodes is a more typical and common manifestation of intra-abdominal lymph node tuberculosis and is the main diagnostic basis. Lymph node nodules smaller than 25 px tend to be uniformly strengthened, while lymph node nodules larger than 25 px tend to be circumferentially strengthened, and a few may be mildly uniformly or heterogeneously strengthened.
(D) Lymph node puncture or biopsy and bacteriological examination. Ultrasound or CT-guided lymph node puncture can achieve a high diagnostic success rate, and laparoscopic pathology of intra-abdominal lymph node biopsy or dissection for pathological examination should be indicated for abdominal masses that cannot be diagnosed clearly by various examination methods, and cannot be excluded from tumor, and other indications for surgery. Antacid staining of biopsy tissue and culture of tuberculosis bacilli are diagnostic tools that clinicians cannot ignore.