Non-traumatic anterior mediastinal abscess in childhood.

Anterior mediastinal abscesses (MAs) due to a non-traumatic etiology are extremely rare in childhood and only 13 such cases have been reported in the literature. We report a 5-year-old male child with disseminated staphylococcal infection and a large non-traumatic anterior MA, who had a successful recovery after surgical drainage of the abscess.

INTRODUCTION

Mediastinal abscesses (MAs) in the pediatric population are relatively rare and usually occur as a complication of esophageal perforation, thoracic trauma, or thoracic surgery.[1] MA due to a non-traumatic etiology is extremely rare in childhood and usually results either from direct extension along contiguous anatomic pathways and fascial planes like pulmonary/pleural and buccopharyngeal areas, osteomyelitis of the ribs or vertebrae, or by hematogenous or lymphatic spread from distant sites of infection.[2] This report describes a boy who presented with abscesses in the left axilla and over the right thigh, along with right pleural empyema and pericardial effusion. During the course of the illness, the patient developed a large abscess in the anterior mediastinum which necessitated open surgical drainage.

CASE REPORT

A 5-year-old male child presented with high-grade fever of 1 week duration, associated with swellings over the right thigh and in the left axillary region. For 4 days, the child was having increasing difficulty in breathing. At admission, there was severe respiratory distress with a respiratory rate of 68/min. A tender, non-fluctuant swelling was present over the antero-lateral aspect of the right thigh and was associated with limitation of movement of the right hip. Another tender and fluctuant swelling measuring 3 cm was present in the left axillary region. The chest examination revealed findings suggestive of right-sided pleural effusion and a pericardial rub with normal heart sounds. There was no past history of contact with tuberculosis. Provisionally, the possibility of severe pneumonia with right pleural empyema, pericardial effusion, right thigh abscess and left axillary abscess was considered.

Initial laboratory investigations showed marked leukocytosis with neutrophilia and raised erythrocyte sedimentation rate (ESR). A chest radiograph showed right-sided pleural effusion with cardiomegaly [Figure 1]. An ultrasound (US) chest showed a localized hetero-echoic collection in the right pleural space with maximum thickness of 2.7 cm and pericardial effusion with a fluid thickness of 8 mm. The US of the hips was normal. An intercostal drainage tube was inserted to drain the localized empyema on the right side. On day 1, 150 ml of pus was drained which decreased to 20 ml by day 3. Incision and drainage of the left axillary and thigh abscesses was also performed and the pus sent for culture. In view of the possibility of disseminated staphylococcal sepsis, the child was started on parenteral vancomycin and ceftriaxone.

Figure 1

Chest radiograph shows mediastinal widening

Despite these measures, the child continued to have high-grade fever along with significant respiratory distress and toxicity. Repeat US chest after 72 hours showed resolution of the right-sided empyema as well as the pericardial effusion. The urine and blood cultures were sterile. Pus culture from the left axillary abscess showed methicillin-sensitive Staphylococcus aureus which was sensitive to amoxicillin–clavulanate, vancomycin and amikacin. Despite appropriate parenteral antibiotic therapy, the fever and toxicity persisted. A small localized collection of pus became apparent in the epigastric area and this was drained by needle aspiration. An US abdomen did not reveal any intra-abdominal collection. A repeat chest radiograph showed superior mediastinal widening; therefore, a contrast-enhanced computed tomogram (CT) chest was performed. This revealed multiple conglomerate anterior and superior MAs extending from the thoracic inlet to the diaphragm [Figure 2]. Pediatric surgery consultation was sought and the child underwent surgical drainage of the MA via right anterolateral thoracotomy through the 6th intercostal space. Subsequently, the condition of the child improved dramatically as fever subsided and toxicity disappeared. Intravenous antibiotics were administered for a total of 4 weeks. The subsequent recovery was uneventful.

Figure 2

CT scan showing multiloculated abscess in anterior mediastinum

DISCUSSION

MA secondary to a non-traumatic etiology is extremely uncommon in childhood, especially since the advent of widespread antibiotic treatment; in the last two decades, around 13 such cases have been reported. Non-traumatic MA is most common in the first 2 years of life with the age at presentation varying from 15 days to 11 years.[3] The most common causative organism identified in non-traumatic mediastinitis is Sta. aureus, although cases caused by Streptococcus pneumoniae] and mixed aerobic and anaerobic bacteria have also been reported.[4] In most reported cases of non-traumatic MA, the abscess was secondary to spread from a local infective focus. In two cases, MA developed following a retropharyngeal abscess.[56] In another case, tubercular chronic retropharyngeal abscess secondary to tubercular spondylitis extended to the antero-superior mediastinum.[7] Komatsu et al. reported MA in the postero-superior mediastinum, complicating purulent tonsillitis by gram-positive cocci. Two cases of Str. pneumoniae MA secondary to right-sided pneumonitis[8] and focal thymic infection have also been reported.[9]

Cases of non-traumatic MA secondary to hematogenous and/or lymphatic spread from distant infection sites have also been described. In a report of a case, Tercier et al.[3] described a 12-month-old boy in whom cellulitis of the left hemithorax with multiple abscesses in the left axilla caused by Sta. aureus was complicated by pericarditis, a left pleural effusion, and finally, a huge collection in the left antero-posterior mediastinum, necessitating drainage by a suprasternal horizontal cerviotomy. The authors believed that their case could be due to hematogenous/lymphatic spread from the axillary site, with lymphatic spread being the more likely reason since the internal mammary lymphatics communicate extensively with lymphatics in the upper mediastinum.[3] MA secondary to septic arthritis has been reported,[10] while cases of MA developing secondary to an abscess over the hip[11] or over the hand[12] have also been described. Gamiao[13] reported a 5-year-old boy who developed an abscess in the antero-superior mediastinum, secondary to a massive pericardial effusion due to Sta. aureus pericarditis. The case was also complicated by pleural effusion and the author surmised that the primary bacterial endocarditis in their case might have caused contiguous extension of infection in the mediastinal area via a direct or hematogenous route.[13]

In our case, the most likely etiology of MA was lymphatic or haematogenous spread from the abscess in the left axilla and over the right thigh. The epigastric abscess which developed during the hospital stay could have been a separate subcutaneous collection or an extension from the anterior MA through persistent anterior diaphragmatic slits.

Early diagnosis and aggressive treatment of mediastinal infections is a must to decrease mortality and morbidity. Although a chest radiograph can give information regarding a widened mediastinal shadow, the findings may not be confirmatory. The imaging modality of choice is contrast-enhanced CT scan which gives information about the extent of the MA, presence or absence of loculations, and its relationship with vital organs.[13] In infants with deep cervical infections, a close vigilance should be instituted to detect potential mediastinal extension by performing follow-up plain radiograph or CT scan.

Although it has been stated that for non-traumatic MA, conservative treatment with appropriate antibiotics alone for prolonged periods may be successful,[14] most reported cases have in addition needed a minimal invasive percutaneous drainage procedure which was performed by an extrathoracic approach. This varied from drainage by a suprasternal approach,[10] supraclavicular approach,[1] right-sided thoracocentesis,[8] catheter drainage by a subxiphoid approach,[13] multiple ultrasound-guided needle aspirations,[7] to CT-guided parasternal drainage.[6] No case reported earlier in the literature needed thoracotomy for drainage and it has been suggested that thoracotomy is unnecessary for draining MA in the pediatric population and should be avoided to prevent thoracic wall and hemithoracic spread.[26] In our patient, thoracotomy with open drainage was necessary because of the worsening condition of the child and as the abscess was large with multiple loculi and septations.

In conclusion, non-traumatic MA is a rare and dreaded complication of various etiologies, especially deep neck infections or septic foci elsewhere in body. Early recognition and appropriate management are the cornerstones for successful outcome.