INTRODUCTION

Empyema necessitans (EN) is a rare complication of pleural empyema in which purulent material dissects through the parietal pleura into the chest wall or adjacent soft tissues. Historically, EN was most frequently associated with Mycobacterium tuberculosis and, less commonly, with Actinomyces or fungal pathogens such as Aspergillus^[1–3]. Although its incidence has declined due to modern antibiotics, and EN is uncommon in contemporary practice, with one thoracic surgery cohort reporting 9 cases over a 4-year period^[4], it remains clinically important because of its capacity for severe local invasion, propagation along fascial planes, and systemic dissemination.

Once the infection extends beyond the thoracic cavity, spread typically occurs via contiguous extension along the fascial planes, although hematogenous dissemination is also possible. This tracking may predispose to necrotizing fasciitis (NF), a rapidly progressive soft-tissue infection with mortality exceeding 20% despite prompt management^[5]. Dissemination can also involve the genitourinary system, resulting in emphysematous cystitis (EC), defined by intramural bladder gas. EC is uncommon and typically reported in elderly, diabetic, or immunosuppressed patients, though it may arise in other settings^[6].

Streptococcus anginosus, part of the Streptococcus milleri group, is known for its potent abscess-forming capacity and ability to cause invasive thoracic, abdominal, retroperitoneal, and deep soft-tissue infections^[7]. Incompletely treated empyema may facilitate hematogenous or contiguous spread, allowing infection to track along intercostal, paravertebral, or retroperitoneal planes. However, the simultaneous occurrence of EN, NF, widespread retroperitoneal abscesses, and EC in an immunocompetent adult is exceedingly rare.

We describe such an unusual and severe presentation in a previously healthy woman, illustrating the aggressive pathogenic potential of S. anginosus in the context of inadequately treated pleural empyema and emphasizing the need for prompt recognition and multidisciplinary management.

CASE DESCRIPTION

A 36-year-old previously healthy woman initially presented to another facility with bilateral empyema and pyelonephritis, requiring intensive care unit (ICU) management with oxygen supplementation and vasopressors. Bilateral chest drains were inserted; pleural cultures grew Streptococcus species. She received intravenous meropenem and clindamycin; meropenem was selected to provide broad-spectrum coverage in the setting of severe sepsis with potential polymicrobial infection, while clindamycin was added for its toxin-suppressing effects in suspected severe streptococcal infection. The patient demonstrated clinical improvement but subsequently left against medical advice with plans to return to her home country.

Several days later, she was found at an airport in severe respiratory distress and brought to our hospital. On arrival, she was febrile, tachycardic, tachypnoeic, and in septic shock. Examination revealed significant swelling of the right lower limb with an open, foul-smelling posterior thigh wound. Laboratory results demonstrated leucocytosis and markedly elevated inflammatory markers (Table 1). Diabetes screening with HbA1c was performed and yielded a normal result (5.4%). Transthoracic echocardiography showed preserved ejection fraction and no pericardial effusion.

Urgent CT chest revealed substantial bilateral multiloculated empyema with pleural thickening, lung collapse, and chest-wall extension consistent with EN (Fig. 1). CT abdomen and pelvis showed multiple large multiloculated collections, including a right posterior pararenal abscess measuring approximately 8.5 × 6.2 cm and retroperitoneal collections extending into the quadratus lumborum muscle. Intramural bladder gas indicated EC, with adjacent thickened ileal loops (Fig. 2). CT lower limbs demonstrated subcutaneous gas and deep fascial involvement of the right thigh, confirming NF (Fig. 3).

The patient was intubated, commenced on vasopressors, and admitted to the surgical ICU. Broad-spectrum intravenous (IV) antibiotics were initiated. Emergency debridement of the right thigh demonstrated widespread necrosis of skin, subcutaneous tissue, and muscle. She remained intubated for 15 days and underwent four additional debridements with vacuum-assisted closure. After the final procedure, the wound showed healthy granulation tissue, and she was successfully extubated. She continued prolonged IV antibiotics throughout wound closure.

Persistent empyema required right-sided chest drainage. Pleural fluid cultures grew S. anginosus; acid-fast bacilli were negative. Though the drain was removed after one week, repeat CT scan demonstrated a new left-sided loculated empyema requiring contralateral drainage, which remained until radiological resolution.

Retroperitoneal abscess drainage was deemed unsafe by interventional radiology due to depth and location. Urology recommended bladder catheterization and continued antibiotics for EC. Multidisciplinary teams, including pulmonology, infectious diseases, cardiothoracic surgery, orthopaedics, and critical care, were involved. Cardiothoracic surgery deferred decortication given her improving trajectory.

Because of the unusually widespread disease, an immunological evaluation was performed. Quantitative immunoglobulins, human immunodeficiency virus testing, and tuberculosis studies were normal (Table 1).

Following 5 weeks of intensive multidisciplinary care, imaging demonstrated resolution of empyema and satisfactory healing of the thigh wounds. The patient was discharged in stable condition with a 3-week course of oral amoxicillin-clavulanate and scheduled infectious diseases, pulmonology, and orthopaedic follow-up.

DISCUSSION

This case illustrates an exceptionally rare presentation of EN due to S. anginosus, complicated by NF of the thigh and widespread retroperitoneal abscess formation. EN typically results when empyema erodes through the parietal pleura and extrudes into soft tissues^[2]. While the chest wall is the most common site, pus may dissect to the vertebral column, mediastinum, groin, flank, or retroperitoneum^[8]. In this patient, CT scan did not demonstrate a visible fistula between the thoracic empyema and retroperitoneal abscesses; magnetic resonance imaging (MRI) was not performed to further delineate fistulous tracts due to her significant clinical improvement, representing a diagnostic limitation in confirming the exact route of spread.

Although EN is classically associated with tuberculosis or fungal pathogens, S. anginosus is increasingly recognized as an emerging cause. A recent case was reported by Ayoola and Zejnullahu, where a patient with chronic obstructive pulmonary disease developed empyema necessitans from Streptococcus intermedius, which is a part of the S. anginosus group^[9]. Moreover, Noguchi et al. demonstrated the association of S. anginosus with obligatory anaerobes in empyema^[10], and this, coupled with the known virulence factors including hyaluronidases, contributes to its behavior^[11]. Reis-Melo et al. reported pediatric EN caused by S. anginosus^[12], and Sullivan et al. described a case following coronavirus disease 2019 infection in an immunocompetent adult^[13]. Other unusual presentations include EN after chest drain insertion^[14] and EN in immunocompromised patients after thoracostomy^[15]. To our knowledge, very few cases have been reported of EN due to S. anginosus presenting with NF of the thigh requiring urgent debridement, accompanied by retroperitoneal and perinephric collections.

This case broadens the known spectrum of S. anginosus infections. Despite the absence of diabetes, immunosuppression, or other classic risk factors, the organism produced severe multifocal disease. This underscores the importance of vigilance in patients with chest-wall extension of empyema or multifocal abscesses, as early recognition may expedite intervention.

Management principles are reinforced by this case: survival in fulminant infections relies on early diagnosis, repeated aggressive surgical debridement, prolonged culture-guided IV antibiotics, and multidisciplinary coordination^[5,14-15]. The patient’s favourable recovery despite widespread disease highlights the efficacy of timely, coordinated intervention.

CONCLUSION

This case highlights the ability of S. anginosus to cause multifocal invasive disease even in immunocompetent adults. Proper management of empyema, including timely drainage, adequate IV antibiotics, and surgical decortication, when necessary, is essential to prevent complications such as EN and NF. Awareness of these rare presentations facilitates early recognition, aggressive surgical management, and coordinated multidisciplinary care, all of which are critical for survival. Long-term follow-up is recommended to monitor for potential recurrence or late complications, such as chronic osteomyelitis or soft-tissue dysfunction.