We present a case of hematogenously acquired thyroid abscess with direct extension into the superior mediastinum. Though rare, suppurative thyroiditis is associated with substantial mortality. Appropriate evaluation, including imaging of the neck and mediastinum, followed by aggressive medical and surgical intervention, is required for optimal management.
Acute suppurative thyroiditis is rarely encountered in modern medical practice but must be considered whenever inflammatory disease of the thyroid is evaluated. A combined medical–surgical approach is necessary for cure of this potentially lethal infection. A case of hematogenous Staphylococcus aureus thyroid abscess is described, and the relevant literature is reviewed.
A 61-year-old male diabetic with a history of a left leg above the knee amputation (AKA) presented to the hospital complaining of 1 week of malaise, neck pain, and fever. He reported that a draining ulcer had spontaneously developed on the distal end of his AKA stump 2–3 weeks before admission. Though he had “mild” diabetes, he had not had any medical care since his 1997 AKA and took no medications. He denied hoarseness, dysphagia, or shortness of breath. There was no history of thyroid disease, trauma, or bleeding diathesis.
A physical examination was significant for fever to 102°F (38.9°C), tachycardia, and tachypnea. An extremely tender, asymmetric 10 × 3 cm firm anterior neck mass with overlying erythema and warmth was noted. The right side of this neck mass was more prominent than the left. The oropharynx was without lesions, and there was no cervical lymphadenopathy. A 3 × 4 cm ulcer with purulent drainage was present at the distal end of the right stump. The vocal cords were normal. No murmurs were appreciated. Dullness and absent breath sounds were noted at the left lung base. There were no stigmata of thyroid gland dysfunction.
Laboratory studies were significant for a leukocytosis (white blood cell count of 26,800/mL with 92% segmented cells) and a moderate number of bands. The erythrocyte sedimentation rate was 124. A random blood glucose test was 243 mg/dL. Thyroid function tests were normal (thyroid-stimulating hormone and free thyroxine). The chest roentgenogram revealed a left pleural effusion. Multiple aspirates of the neck mass showed frank pus, no malignant cells, and gram-positive cocci in clusters. Cultures of blood, AKA ulcer, multiple neck aspirates, and left-sided pleural fluid yielded oxacillin sensitiveStaphylococcus aureus.A magnetic resonance imaging scan of the neck and chest showed a large thyroid abscess descending into the anterior mediastinum and abutting the great vessels; the right internal jugular vein was partially occluded, and the trachea was displaced. A transthoracic echocardiogram did not demonstrate any valvular vegetations.
The patient underwent extensive neck dissection and drainage, exploration of the superior mediastinum, right thyroidectomy, and left chest tube drainage of his empyema. A predominantly right-sided thyroid abscess with direct extension into the superior mediastinum was found. The resected thyroid tissue was found to have diffuse acute necrotizing inflammation. He was treated with nafcillin and rifampin for 8 weeks. His neck erythema and tenderness resolved over the first 2 weeks of antibiotics. Postoperative thyroid function tests were normal, and a follow-up computed tomographic scan showed resolution of the mediastinitis and internal jugular thrombosis.
This patient developed a thyroid abscess with descending mediastinitis as a consequence of S. aureus bacteremia from an infected right leg ulcer. This case is notable because of the hematogenous seeding of the thyroid from a peripheral site of infection and the subsequent development of descending cervical mediastinitis. Thyroid abscess is an extremely rare disease. In the preantibiotic era, 0.1% of thyroid operations were done to treat thyroid abscesses . From 1900 to 1980, only 250 cases of thyroid abscesses were reported in the English literature . Thyroid abscess is thought to be rare because of the thyroid’s high blood flow to mass ratio, its multiple separations, and its iodine content, as iodine is thought to have antibacterial properties . Microbial agents causing thyroid infections include bacteria, fungi, viruses, and parasites . The thyroid can be infected hematogenously, by lymphangitic spread, through a patent thyroglossal duct or piriform sinus fistula, or by direct inoculation . The most common bacteria involved are S. aureus, group A β-hemolytic streptococcus, and Streptococcus pneumoniae . Fungal infection with aspergillus is occasionally seen in immunocompromised individuals, and rare cases of acute suppurative thyroiditis (AST) with the parasitic dog tapeworm Echinococcus granulosus  have been reported.
AST is most commonly seen in women between 20 and 40 years of age with a history of a thyroid goiter [4–6]. AST also occurs in children who have a persistent piriform sinus fistula from remnants of the branchial pouch . These children are usually affected before the age of 10 years; the left side of the thyroid gland is more often affected than the right.
AST typically presents with fever and a tender inflamed neck mass. The patient may complain of associated dysphonia and dysphagia if the abscess is having a major mass effect [2,8]. Cervical lymphadenopathy is rare. As with most serious infections, there is a pronounced leukocytosis with immature WBC, and the patient typically has signs of a bacterial infection, including rigors and chills. Thyroid function tests and thyroid antibody levels are usually normal . Aspirates of the mass reveal numerous polymorphic neutrophils. In 90% of cases, appropriate cultures of the aspirate reveal the causative organism . Either computed tomography with intravenous contrast or magnetic resonance imaging of the neck and mediastinum is appropriate to delineate the extent of the infection . If a persistent piriform sinus fistula is a consideration, a barium swallow is the test of choice .
The differential diagnosis includes other inflammatory diseases of the thyroid, such as Hashimoto’s disease, subacute granulomatosis, thyroiditis, and Reidel’s thyroiditis [8,10]. In addition, a rapidly growing, anaplastic thyroid carcinoma, anterior neck cellulitis, or an infected cystic hygroma can mimic AST [8,11].
Definitive treatment of AST is both surgical and medical. As with all abscesses, incision and drainage are critical. Appropriate parenteral antibiotics and judicious use of nonsteroidal anti-inflammatory drugs are also vital . Mortality rate of AST ranges from 3.7%–25%, with generally lower rates reported in more recent reviews . Most deaths are attributed to mediastinitis, internal jugular phlebitis, esophageal rupture, tracheal perforation, or sepsis , and occur primarily in immunocompromised hosts . Long-term sequelae after successful treatment are rare. However, all patients should be followed up with annual thyroid function tests [9,14,15]. The management of descending cervical mediastinitis is controversial. Although most authorities recommend that both the neck and chest be explored [16,17], our patient was successfully managed with an extensive neck dissection, superior mediastinal exploration, and chest tube drainage.
This care illustrates two rarely encountered processes, suppurative thyroiditis and descending cervical mediastinitis. Thyroid abscess should be suspected when a tender, inflamed thyroid is noted. Mediastinal imaging is a key part of the initial evaluation.
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