Year : 2001 | Volume
: 11 | Issue : 3 | Page : 131--134
CT findings of descending necrotizing mediastinitis
MK Dwivedi, RK Pal, R Gupta, SJ Rizvi, RP Singh, PB Borkar
Department of Radiodiagnosis JLN Hospital & R.C. Bhilai, India
M K Dwivedi
Department of Radiodiagnosis JLN Hospital & R.C. Bhilai
Objective: To assess the role of CT in the diagnosis of descending necrotizing mediastinitis (DNM).
Materials and Methods: Fifteen patients were examined with CT of the neck and chest to evaluate the extension of infection in the mediastinum and to help in planning a surgical approach.
Results: In every patient, the CT scan confirmed the diagnosis of DNM displaying cervical abscess or cellulitis with emphysema associated with diffuse mediastinitis or mediastinal collections such as empyema thoracis, pneumomediastinum or pericardial effusion.
Conclusion: Early CT diagnosis of DNM helps us in deciding the appropriate early surgical approach, whereby the mortality rate could be considerably lowered
|How to cite this article:|
Dwivedi M K, Pal R K, Gupta R, Rizvi S J, Singh R P, Borkar P B. CT findings of descending necrotizing mediastinitis.Indian J Radiol Imaging 2001;11:131-134
|How to cite this URL:|
Dwivedi M K, Pal R K, Gupta R, Rizvi S J, Singh R P, Borkar P B. CT findings of descending necrotizing mediastinitis. Indian J Radiol Imaging [serial online] 2001 [cited 2020 Feb 22 ];11:131-134
Available from: http://www.ijri.org/text.asp?2001/11/3/131/28391
Descending necrotizing mediastinitis (DNM) represents a virulent form of mediastinal infection requiring prompt diagnosis and treatment to reduce the high mortality associated with this disease . Acute mediastinitis results from oropharyngeal abscess with severe cervical infection spreading along the fascial planes into the mediastinum. Infections in the neck cause diffuse thickening of the cutis and subcutis and reticular enhancement of subcutaneous fat of the face and neck; thickening and /or enhancement of cervical fasciae; asymmetric thickening on enhancement of cervical muscles; and fluid collections in several neck spaces. Inconsistent diagnostic features include gas collections in the neck . Infections in the neck may travel inferiorly because of the effects of gravity and negative intrathoracic pressure. The visceral mediastinum is involved more commonly by way of the prevertebral space . Acute mediastinitis is rare. Causes of acute mediastinitis are esophageal perforation, necrotic neoplasm of the esophagus or tracking of infection from the neck or retroperitoneum into the mediastinum . The term necrotizing mediastinitis is used to describe a severe, acute and potentially life-threatening inflammatory condition caused by streptococcal or mixed bacterial infection and propagating in continuity within the soft tissue .
The delay in diagnosis is the main cause for the high mortality in this life-threatening condition. We report our experience in 15 patients with DNM and stress the importance of early diagnosis for reducing the mortality rate that ranges from 30 % to 40% ,. Consequently CT scan helps in arriving at an early diagnosis of DNM reducing the mortality rate.
Materials and Methods.
Over a two-year period, we diagnosed DNM in fifteen patients using a SOMATOM HiQ CT Scanner (Siemens, Erlangen) at our institution. In all patients, the criteria of Estrera were fulfilled. These criteria included
Clinical manifestation of severe oropharyngeal infection.Demonstration of characteristic radiographic features of mediastinitis. Documentation of necrotizing mediastinal infection on surgery.Establishment of relationship between the oropharyngeal infection and the development of the necrotizing mediastinal process.
In each of these patients, these relationships were clearly established. Our patients comprised thirteen men and two women, with age ranging from twenty three to fifty eight years. The primary oropharyngeal infection was a peritonsillar abscess in nine patients and odontogenic abscess in five patients. One patient had a history of neck trauma with esophageal perforation.Ten patients had diabetes. All patients had received previous antibiotic therapy. The delay between the onset of primary infection and hospitalization varied from three to ten days.
All patients underwent contrast-enhanced cervicothoracic CT Scan within one to twelve hours of admission. CT was performed with a dynamic bolus administration of 150-160 ml contrast. The injection protocol for all adult patients consisted of an initial 80 ml bolus administered at 1.5 ml/sec, followed by 70-80 ml administered at 0.3 to 0.5ml/sec. CT scanning was started after 60 seconds to allow sufficient time for post-contrast enhancement of soft tissues. Contiguous sections of 5 mm from the skull base to the dome of the diaphragm were taken. Signs of mediastinal infection demonstrated by CT included
(1) Mediastinal soft tissue infiltration with gas bubbles [Figure 1].
(2) Mediastinal uncapsulated fluid collections in the anterior or posterior mediastinum [Figure 2] and
(3) Mediastinal abscess, pleural and pericardial effusion [Figure 3].
In each patient, the CT scan confirmed the diagnosis of DNM displaying cervical abscess or cervical cellulitis with emphysema associated with diffuse mediastinitis or mediastinal collections and complicated by empyema thoracis, pneumomediastinum or pericardial effusion. Diffuse mediastinitis was defined as soft tissue infiltration more than 26 HU or gas bubbles obliterating normal fat planes. Mediastinal abscess was seen as a well-defined fluid collection less than 20 HU with or without air fluid level. [Table 1].
The most dreaded and probably the most lethal form of mediastinitis is the diffuse necrotizing variety that occurs as a complication of infection of oropharynx, best termed descending necrotizing mediastinitis. DNM is an uncommon clinical entity of the suppurative mediastinitis group. Brunelli et al  recorded 58 cases and Corsten and associates  recorded 69 cases of DNM from 1960 to 1995. This rare variety of mediastinitis is a highly lethal disease according the review of Estrera and associates, who reported a 40% mortality rate in the antibiotic era , while Marty-Ane and associates  have reported a 17% mortality rate. DNM diagnosis implies that the relationship between mediastinitis and oropharyngeal infection is clearly established. The most common primary oropharyngeal infection is odontogenic according to the review of Wheatly and associates (25 out of 43 patients)and peritonsillar abscess in seven out of 12 patients .
In our series odontogenic origin was seen in five patients and peritonsillar abscess in nine. Delay in the diagnosis is one of the primary reasons for the high mortality in DNM. The diagnosis of cervical infection is clinically obvious but early diagnosis of mediastinitis is difficult because of the vague early symptoms that indicate mediastinal involvement . Early in the disease, a chest radiograph is negative but as the disease progresses, the frontal radiograph of the chest shows widening of the mediastinal shadow while the lateral view might reveal an increased opacity of the retrosternal space. Three patients in our series showed mediastinal emphysema on chest radiographs. In all our patients, a CT scan immediately confirmed the diagnosis with high accuracy, showing soft tissue infiltration with loss of the normal fat planes or collections of fluid density with or without the presence of gas bubbles 
Routine use of the CT scan is highly recommended in patients with deep cervical infections for an early detection of mediastinitis at a time when the chest radiograph reveals no abnormal findings. In addition CT scanning provides accurate information on the relationship to the D4 level, of involvement of the various mediastinal compartments involved in the necrotizing process and determines the optimal thoracic approach for efficient surgical drainage. Early diagnosis by CT Scan helps in the early management of descending necrotizing mediastinitis and considerably reduces mortality rates.
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