Abscess in the thyroid gland is a rare but severe infectious disease. The condition can have anatomic or iatrogenic underlying causes. If untreated it could be fatal. Pathogens vary considerably. Treatment is intravenous antibiotics, drainage, and sometimes surgery.
The electronic medical records of all adult patients with acute thyroiditis 2003–2017 treated at the Karolinska University Hospital (catchment area 2 million) in Sweden were systematically reviewed.
Five patients were found in the catchment area. One patient from another region but known to us was also included. Thus, six patients (aged 28–73 years) were included in the study. Median length of hospital stay was 7.5 days (4–79 days). All were treated with antibiotics (intravenous n = 5, oral n = 1). Total antibiotic treatment duration was 13.5 days (10–41 days). Blood cultures were positive in three (streptococcus pneumonia, streptococci sanguineous, pepto streptococci), deep tissue culture in three (Escherichia coli, Candida, Hemophilic influenza) and no positive culture at all in two. Drainage was used in three patients. All patients recovered without recurrences. Surgery was performed twice in the acute phase in one. There was no recurrence during 7 years (3–12) of follow-up, but one patient died after three years (severe heart failure and pneumonia).
Thyroid abscess in adults is extremely rare nowadays in the developed world. With prompt antibiotic therapy, drainage and in some cases thyroidectomy the prognosis seems favourable.
The aim of this investigation was to explore the incidence of thyroid abscess in a region with well-developed health care in adult patients without anatomical defects or who were immunosuppressed, and to describe the clinical presentation, treatment and outcomes.
This was a retrospective investigation of all adult cases with a thyroid abscess between 1 January 2003 and 31 December 2017 conducted at the Karolinska University Hospital in Stockholm, Sweden. The Karolinska University Hospital has a catchment area for highly specialized care and thyroid surgery of more than 2 million inhabitants. We knew of three cases with thyroid abscess since previously. Moreover, all patients with an International Classification of Diseases version 10 (ICD-10) code of E06.0 (acute thyroiditis), E07.1 (dyshormogenic goiter), E07.8 (Other specific disorders of thyroid), and E07.9 (Disorder of thyroid, unspecific) were reviewed, to explore if additional cases could be found, and subsequently two more cases were found. All the relevant electronic medical files of the patients were reviewed manually and all clinical and biochemical data of patients with AST were recorded in detail. The National Population Register was also consulted to find out if the included patients were still alive and the date of death was retrieved if applicable [27]. All hospital admissions and specialist out-patient visits in Sweden are coded with ICD-10 codes by the attending doctor and are thereafter stored in both local and national databases [28]. One of the authors (GW) had reviewed all surgical thyroid patients at the Örebro University Hospital (catchment area 280,000 inhabitants) from 2008 until today, and only one patient with AST from that region was found and was subsequently included. Patients with necrosis and infection post-surgery for thyroid malignancies were excluded, children (patients less than 18 years of age) as well as patients with AST secondary to immunosuppression. Results are presented as median and range.
The study was approved by the Regional Ethical Review Board in Stockholm, Sweden. All patients or their next of kin were contacted and written informed consent was obtained.
In total six patients with thyroid abscess was included (five females). The abscesses were equally commonly located in each thyroid lobe. Median age at presentation was 51 years (28–73 years). None had third or fourth left branchial cleft anomalies nor was immunosuppressed. All patients were successfully treated with antibiotics for 13.5 days (10–41 days), drainage in three, and surgery was performed twice in the acute phase in one and at a later state in one. The length of hospital stay was 7.5 days (4–79 days). Median follow-up time was 7 years (3–12 years). A detailed description is given in the case presentations below and the clinical data are summarized in Table 1.
Table 1 Laboratory measures, clinical signs and cultures in patients with thyroid abscessA previously healthy 28-year-old woman had three months after delivery developed left-sided swollenness in the neck, pain, fever and tachycardia in the last 10 days. At another hospital this was suspected as a subacute thyroiditis as TSH was 0.1 mIU/L (0.4–3.5) and free T4 21 pmol/L (10–22). Thyroglobulin was normal. Treatment was commenced with oral prednisolone 25 mg daily and she was discharged after two days. One day later she returned with progression of the lump in the neck and breathing difficulties. She was admitted to the intensive care unit at the tertiary hospital with the combined diagnosis of epiglottitis and acute thyroiditis. At this time there was a non-tender 50 × 50 mm large lump to the side of the throat with no erythema. Heart frequency was 132 beats per minute and temperature 39.3 °C. Increasing edema of the glottis was noted and she could not swallow but had no stridor. Iv cefuroxime 1.5 g tds was initiated. Repeated fiberscope examinations showed progressive edema and she was subsequently intubated. A CT showed a 70 mm large multicystic process in the left thyroid lobe expanding cranially and dorsally dislocating the larynx to the right, as a thyroid abscess, which was drained with three drains. There was an anaerobe smell from the extracted pus, and iv 1000 mg metronidazole od added for four days. Clinically she improved and could leave the intensive care unit after five days, and the hospital after additional three days. Cultures from nasopharynx revealed Hemophilic influenza, and from blood Pepto streptococci. In the abscess there was also Hemophilic influenza. Iv antibiotic treatment was altered to oral metronidazole 400 mg tds for five days and amoxicillin/clavulanic acid 875/125 mg bid for ten days. Thyroid function tests were normalized after one months. There has been no recurrence at the review eight years later.
AST is a very rare infectious disease affecting the thyroid. We describe a relatively large series of six cases in otherwise healthy adult patients without anatomic anomalies with AST. In two iatrogenic causes could be established, in four no clear pathologic route could be established, and no causative organisms could be cultured in two. All of them were treated with antibiotics, intravenous treatment initially in five and oral in one, three were treated with drainage, and all of them recovered the acute episode.
AST is most often described in children with anatomic aberrations or in patients with immunosuppression such as transplant recipients or after chemotherapy. However, the clinical picture may differ between children and adults. With prompt diagnosis and treatment, and in patients without underlying disease, the outcome is very good, although mortality is still reported [29]. In AST, the clinical spectrum is broad, as even asymptomatic cases have been reported [30]. Typically, symptoms in AST are similar to those in patients with subacute or chronic thyroiditis. Other differential diagnosis are hemorrhage in the thyroid, amiodarone induced thyrotoxicosis, infarction of a thyroid nodule [31], and rapidly growing thyroid cancers. Prompt treatment is necessary as the infection may cause destruction of the thyroid and the parathyroid glands, spread to other organs, or cause abscess rupture, vocal cord palsy and fistulae to the trachea or oesophagus [32, 33]. None of these were seen in our six patients.
Among patients > 20 years old in the study by Yu et al. 32/66 were immunocompromised. Their mortality rate was 3.7%, and all these had HIV, cancer or other underlying disease [26]. In contrast, none of our patients were immunocompromised and the only death was not related to AST.
One major route to AST is a pyriform sinus fistula, and if the left lobe is involved the likelihood of an underlying pyriform fistula is increased [34]. Indeed, Miyauchi described this mechanism in 135 of 139 cases in a review [35]. If these patients mainly were children was not clear, although a pyriform fistula can be detected also in adults [7]. In the review by Yu et al. investigating 191 patients with AST 70% had some anatomical structural defect [26]. In contrast, in one study describing 10 adult patients with AST, only one had a pyriform fistula [36]. Also, our six cases had an even distribution of their AST in both thyroid lobes and no such anatomic defect was found.
Ultrasound, or preferably CT, should be deployed to verify a pyriform fistula but could in an early phase be erroneous. CT have the advantage to give information on extra thyroidal involvement. A barium swallow investigation or endoscopic hypopharyngoscopy performed after the acute phase can prove such a lesion [37, 38]. Branchial arch anomalies are other causes, which is not only seen in children [39]. FNA and cultures confirms the diagnosis, the causative organism(s) and which antibiotic to choose, although responsible agents are not always found, as demonstrated by our Case nr 3 and 4.
The age of patients with AST is not always reported. Our patients had a median age of 51 years at presentation, and in this age group treatment and prognosis could be more favourable when no concurrent disease or anatomical factors are present. If AST has a more dismal effect in less developed countries is not known, as reports from these countries are sparse. There may also be underreporting, and a restraint from publishing negative clinical outcomes, as discussed by Paes et al. [1].
If antibiotic treatment fails, surgery as incision with drainage can be necessary. Drainage has in multiple reports been successful, and can be repeated if the abscess persists, or if there is a deterioration [1, 40]. Drainage is urgent in unstable patients with comprised airways. Open surgery, with total, near total or hemithyroidectomy can in severe cases be deployed to relieve pressure symptoms, and later in patients that do not respond to adequate antibiotic treatment and drainage [11, 41, 42]. Complications to surgery are damage to tissues in the area as the parathyroid glands and the recurrence nerve. As identification of anatomic structures in excessive infection often is difficult [12], these tissues may be impossible to find. Therefore, open surgery should be performed with caution and in selected patients. If there is an anatomic defect, surgery could wait until the abscess has been treated with antibiotic therapy, and often also drainage.
The concomitant hypercalcemia and AST in Case 5 is intriguing. No previous calcium levels were known to us. Cultures implied an infection from the upper airways spreading to the thyroid, and the parathyroid lower left gland. If the patient also had primary hyperparathyroidism and if the infection could activate synthesis of PTH remains unclear, but the latter is purely speculative. The ongoing elevation of PTH post-operatively, without any parathyroid enlargement, could to at least to some extent be a result of vitamin D deficiency. However, no such test was performed.
This study has some limitations like all retrospective studies. The systematic review of all AST cases in our centre may have been incomplete due to not being identified by us because of inadequate ICD-coding, Moreover, no diagnostic investigations such as a barium investigation or hypopharyngoscopy was performed, instead imaging was performed with ultrasound, CT and MRI. Thus, presence of anatomic aberrations cannot entirely be excluded, but as none of our patients had any recurrences during seven years of follow-up anatomic aberration are unlikely.
Acute suppurative thyroiditis is an extremely rare disease in the adult thyroid. The mainstay of therapy is antibiotic therapy, drainage and in selected cases surgery. With this approach the prognosis is favourable in patients who are immunocompetent, and who does not have branchial arch anomalies or a pyriform fistula.
All data generated or analyzed during this study are included in this published article.