|Year : 2016 | Volume
| Issue : 3 | Page : 67-75
Ultrasonographic evaluation of superficial space infections
Sarfaraz Padda1, Yashmeet Padda2, S Sathasivasubramanian3, S Aarvind Warrier3, Gaurav Goyal4, Bhawandeep Kaur4
1 Department of Oral Medicine and Radiology, Surendera Dental college and Research Institute, Sriganganagar, Rajasthan, India
2 Department of Oral Surgery, Sri Guru Ramdas Dental College and Hospital, Amritsar, Punjab, India
3 Department of Oral Medicine and Radiology, Sri Ramachandra Dental College and Hospital, Chennai, Tamil Nadu, India
4 Department of Oral Medicine and Radiology, Genesis Institute of Dental Sciences and Research, Ferozepur, India
|Date of Web Publication||21-Dec-2016|
Department of Oral Medicine and Radiology, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab
Source of Support: None, Conflict of Interest: None
Aims and Objectives: To evaluate the use of ultrasonography as a diagnostic tool in determining the state of infection, i.e., cellulitis or abscess, in the superficial space infection of odontogenic origin. Materials and Methods: A total of 35 patients visiting the department and having an inflammatory swelling of odontogenic origin were chosen. Thorough history and clinical examination of patients was done to reach a clinical diagnosis of cellulitis or abscess. Ultrasonography was performed with the help of transducing gel using a linear probe to determine the state of infection, i.e., cellulitis or abscess. Results: Out of 35 patients, 19 patients were clinically diagnosed as abscess whereas the remaining 16 patients were clinically diagnosed as cellulitis. For the 19 patients who were clinically diagnosed as abscess, ultrasonography revealed focal accumulation of fluid suggestive of abscess cavity in all the 19 cases, and ultrasound-guided aspiration was positive in all the cases. For the 16 patients who were clinically diagnosed as cellulitis, ultrasonography revealed focal areas of fluid accumulation suggestive of abscess formation in 5 cases, and ultrasound-guided aspiration was positive all these 5 cases. Sensitivity (100%) and negative predictive value (100%) of ultrasound is much better than that of clinical diagnosis, which is 79% and 69%, respectively, in the detection of state of infection. Conclusion: Ultrasonography was found to be a valuable adjunct to clinical diagnosis in determining the state of infection, i.e., cellulitis or abscess.
Keywords: Abscess, cellulitis, color Doppler sonography, superficial space infections, ultrasonography
|How to cite this article:|
Padda S, Padda Y, Sathasivasubramanian S, Warrier S A, Goyal G, Kaur B. Ultrasonographic evaluation of superficial space infections. J Oral Maxillofac Radiol 2016;4:67-75
|How to cite this URL:|
Padda S, Padda Y, Sathasivasubramanian S, Warrier S A, Goyal G, Kaur B. Ultrasonographic evaluation of superficial space infections. J Oral Maxillofac Radiol [serial online] 2016 [cited 2020 Nov 28];4:67-75. Available from: https://www.joomr.org/text.asp?2016/4/3/67/196351
| Introduction|| |
Odontogenic infection originates from a pulpal or periodontal pathology. The course and severity of the infection process can vary depending upon the virulence of organisms, host resistance, and anatomy of the involved area.  Once the infection extends beyond the dentoalveolar apparatus into the surrounding soft tissues, an inflammatory edema occurs and the area becomes swollen, leading to cellulitis which clinically appears as diffuse, tender, hard swelling, with no clear anatomic boundaries. Subsequently, suppuration occurs and the infection localizes to form an abscess, which clinically appears as localized, fluctuant swelling. Occasionally, abscess may arise directly, without passing through the preceding stage of cellulitis.  Infection may remain confined to the vestibule or the pyogenic material may spread deeply into the contiguous facial spaces such as the submandibular, sublingual, and pterygomandibular.  Severe complications such as mediastinitis, intracranial abscess, and parapharyngeal spread with airway obstruction can develop, if the infection is not recognized and treated promptly. Hence, early diagnosis and prompt treatment of odontogenic infections is mandatory. ,
Once the infection spreads beyond the dentoalveolar apparatus into the surrounding soft tissues, it is often difficult to clinically determine, whether there is an abscess which requires surgical intervention or cellulitis that can be managed satisfactorily with antimicrobial therapy and supportive care alone.
Radiographic evaluation with intraoral X-ray and orthopantomogram (OPG) are usually done to localize the offending tooth, which is the source of infection and to note changes in the perapical area and the adjacent bony architecture; however, they do not provide any information on the extent and stage of infection in facial spaces and soft tissue. Although advanced imaging techniques, such as computerized tomography (CT), magnetic resonance imaging (MRI), are highly precise for imaging soft tissues, they are not routinely used due to their cost and limited availability, as well as the use of ionizing radiation in CT.  An alternative diagnostic tool that is widely available, relatively inexpensive, nonionizing, and provides adequate details of soft tissues is Ultrasonography. Ultrasonography is highly precise in locating pockets of fluid collection, and hence should easily locate abscess in the superficial spaces of orofacial region. ,,
Literature reveals very few studies on ultrasonography used for inflammatory swellings in orofacial region to determine the state of infection, i.e. cellulitis or abscess. Therefore, we conducted a study to evaluate the use of ultrasonography in odontogenic superficial space infection. The aim of the study was to evaluate the use of ultrasonography as a diagnostic tool in determining the state of infection, i.e., cellulitis or abscess, in superficial orofacial space infection of odontogenic origin, and to note the ultrasonographic appearance of cellulitis and abscess.
| Materials and Methods|| |
Ethical clearance was obtained from the institutional ethical board as well as from the Institutional Research Board before starting the study. Written informed consent was taken from every patient included in the study.
Thirty-five patients who had clinically obvious swelling in the orofacial region with signs of inflammation from a symptomatic odontogenic source formed the study group. Presence of odontogenic source was confirmed with an intraoral periapical X-ray (Unicorn Denmart IOPA machine) or OPG (Vatech 400 PAX).
Diagnosis of either an abscess or cellulitis was arrived at after eliciting a thorough history and detailed clinical examination [Figure 1]. Diagnosis of cellulitis was given in case swelling was of 3-7 days duration and was associated with severe and generalized pain. Clinically, the swelling was large, diffuse, hard, exquisitely tender, and nonfluctuant with no clear anatomic boundaries. Diagnosis of abscess was given in case swelling was of more than 5 days in duration and was associated with moderate-to-severe and localized pain [Figure 2]. Clinically swelling was small, circumscribed, fluctuant, and tender. 
|Figure 2: Color Doppler sonography, with artery close to the base of abscess, suggestive of chronic abscess|
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Patients with a history of trauma, malignancy, allergy, or any systemic disorder, which may cause edema in the orofacial region, such as renal disease, long-term steroid therapy, and Cushing syndrome, were not included in the study. Patients having bleeding disorders, neurological disorders such as epilepsy, schizophrenia, etc., which might have led to some complication during aspiration were also excluded from the study. All the selected patients were subjected to routine blood examination.
After this, ultrasonography was performed with the help of transducing gel using a linear array probe of 7.5-12 Mhz was performed. Initially, normal side on the area analogous to the area of the swelling on the other side was screened and ultrasound image of normal side was saved to compare it with the affected side. Then, the area of interest (swelling) was scanned under transverse and axial sections, and the findings were compared with normal contralateral area.
Ultrasonographic diagnosis of cellulitis was given if the area of swelling showed increased thickness of subcutaneous tissue, the area appeared isoechoic-to-hyperechoic, and no focal hypoechoic area suggestive of pus accumulation could be demonstrated. Ultrasonographic diagnosis of abscess was given in in comparison to normal contralateral side a focal hypoechoic area suggestive of pus accumulation was evident. In cases, where the diagnosis of abscess was made, the dimension of abscess cavity, depth of abscess from the skin, and the total amount of pus collection were recorded.
Patients in whom ultrasound revealed an abscess cavity were further subjected to color Doppler sonography to examine the exact anatomical location of abscess, and the surrounding blood vessels and result were recorded, so that during needle insertion, no blood vessel was inadvertently injured [Figure 3]. After this procedure, ultrasound-guided aspiration was done.
Ultrasound-guided aspiration was performed after position of the needle was confirmed to be within the abscess cavity, ensuring that it did not injure any blood vessel if present in close approximation, whose location has already been confirmed using color Doppler. The result of aspiration was recorded and the pus was sent for culture and sensitivity. Complete evacuation of pus by aspiration was confirmed using sonography [Figure 4] and [Figure 5]. In patients for whom complete aspiration of pus could not be achieved, they were further subjected to incision and drainage by a trained oral and maxillofacial surgeon. All the patients were followed up for a minimum of 7 days or till the patients completely recovered.
In cases of abscess, aspiration was attempted from the most fluctuant area of the swelling. If the most fluctuant area was intraoral, aspiration was done intraorally. In case the most fluctuant area was extraoral, aspiration was attempted extraorally. In cases where fluctuation could not be elicited, however, sonography revealed an abscess cavity and site of aspiration or incision, and drainage was solely based on clinical judgment of a trained oral and maxillofacial surgeon.
Intraoperative findings and the clinical outcome of the patient after treatment were taken as gold standard for the final diagnosis. Based on this gold standard, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of clinical diagnosis and ultrasonography were calculated.
| Results|| |
Out of 35 patients, 19 (54%) were clinically diagnosed as abscess whereas the remaining 16 (46%) patients were clinically diagnosed as cellulitis [Table 1].
For the 19 patients who were clinically diagnosed as abscess, ultrasonography revealed focal accumulation of fluid suggestive of abscess cavity in all the 19 cases, and ultrasound-guided aspiration was positive in all the cases [Figure 1].
For the 16 patients who were clinically diagnosed as cellulitis, ultrasonography revealed focal hypoechoic areas of fluid accumulation suggestive of abscess formation in 5 of these cases, and ultrasound-guided aspiration was positive in all these 5 cases.
In the remaining 11 patients, clinically diagnosed as cellulitis, ultrasonography did not reveal any focal area of fluid accumulation, and a sonographic diagnosis of cellulitis was made. Aspiration was attempted at three different points; on the surface of the swelling, aspiration result was negative in all the 11 cases. Hence, based on sonographic findings, 24 patients were diagnosed as abscess, whereas 11 cases were diagnosed as cellulitis [Table 1].
In all the 24 patients sonographically diagnosed as abscess, abscess cavity appeared hypoechoic-to-anechoic and no difficulty was encountered in locating the abscess cavity during the ultrasonography. In 18 (75%) of the 24 cases, sonographically diagnosed as abscess, internal composition pattern was homogeneous, whereas in the remaining 6 (25%) cases, it was heterogeneous. Edge definition in 14 (59%) of the 24 cases, sonographically diagnosed as abscess, was well-defined, whereas it was ill-defined in the other 10 (41%) cases [Table 1].
Color Doppler sonography revealed blood vessels in 11 (46%) of the 24 cases that were sonographically diagnosed as abscess. In the remaining 13 cases (54%), color Doppler did not reveal any blood vessel in close approximation to abscess cavity. In 4 of the cases in which color Doppler sonography was positive, diffuse hyperemia was evident along the periphery of abscess cavity. In the other 7 cases, single blood vessel was evident in close approximation to abscess cavity [Figure 2].
In all the cases, sizes of abscess cavity on transverse and longitudinal side were recorded. The depth of abscess cavity from the overlying skin was recorded. The depth from skin ranged from a minimum of 2.2 mm to a maximum of 14 mm [Table 1].
Sensitivity (100%) and negative predictive value (100%) of ultrasound was much better than that of clinical diagnosis, which was 79% and 69%, respectively, in the detection of abscess cavity. Thus, ultrasonography was found to be a valuable adjunct to clinical diagnosis in determining the state of infection, i.e., cellulitis or abscess [Table 2]. However, the experience of the clinician would definitely affect the clinical specificity. In our study, clinical examination was done by two well-trained oral physicians and one oral and maxillofacial surgeon with an experience of over 9 years in this field.
| Discussion|| |
Clinical diagnosis, as is evident from this study, is often inaccurate. Both needle aspiration and incision under local anesthesia improve clinical diagnostic accuracy but are painful. ,, In this study, we found out that diagnostic accuracy can be significantly improved with the use of ultrasonography as an adjunct to clinical diagnosis. We found that clinical examination alone cannot locate small areas of suppuration within a diffuse swelling (cellulitis). We found ultrasonography to be very sensitive in detecting this occult pus.
In this study, sensitivity, specificity, positive predictive value, and negative predictive value of ultrasound in detecting abscess cavity was 100%. Literature reports have also shown ultrasound to be very specific and sensitive in detecting abscess cavity, ,,,, except one.  Elias et al. in their study found that, in 5 patients, in whom initially ultrasonography had not suggested abscess, after few hours when they were subjected to surgical procedures, there was drainage of purulent material. Gradual transition from cellulitis to an abscess a few hours after examination might be the probable reason for not detecting abscess formation.  To overcome this problem, in our study, all cases sonographically diagnosed as cellulitis were taken up immediately for sonographically-guided aspiration to check for any purulent material.
Cellulitis in ultrasound demonstrates diffuse thickening and increased echogenicity of the skin and subcutaneous tissues. The ultrasound appearance of cellulitis is nonspecific and can be indistinguishable from that of other causes of soft tissue edema. To overcome this, patients having swelling from nonodontogenic causes were not included into the study group. On comparison of ultrasound appearance of cellulitis with that of the normal contralateral area, no definite change in appearance was noted, other than an increase in the distance between bone and overlying skin.
Most of the literature reports have found abscess cavity to be hypoechoic, ,,,,,, although there are occasional reports in which it has appeared to be hyperechoic.  In this study, all the abscess cavities appeared anechoic-to-hypoechoic and no difficulty was encountered in locating them. All the ultrasound diagnosed cases of abscess, in whom complete pus could not be aspirated, were immediately drained by a trained oral and maxillofacial surgeon.
There is hardly any literature report where the authors visualized a sinus tract in ultrasonography in orofacial region. However, in this study, we were able to delineate a sinus tract and were also able to trace its path from the abscess cavity to its opening on the skin surface [Figure 6] and [Figure 7].
|Figure 7: Sinus tract tracking from abscess cavity to the overlying skin surface|
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Color Doppler sonography can delineate blood vessels close to abscess. Thus, injury to these blood vessels can be prevented during aspiration or drainage.  This advantage was clearly evident in our study as there was no bleeding complication during aspiration in all the 8 cases. Color Doppler sonography can detect hyperemia in walls adjacent to abscess evident during the acute stage. This may aid in differentiation from noninflammatory collections, for example cyst, lymphocele, etc. ,,
The exact advantage of using ultrasonography in inflammatory swelling can only be evaluated on comparing the treatment outcome in patients in whom the diagnosis is based only on clinical findings with those where ultrasonography has been used as an adjunct to clinical diagnosis.
In this study no effort was made to correlate the appearance of abscess cavity with the duration of swelling, which might have helped to note the differences between the appearance of acute and chronic abscess.
| Conclusion|| |
To conclude, ultrasonography is very accurate in determining the state of infection, i.e., cellulitis or abscess. In this study, sonographic appearance of abscess was very specific; abscess cavity appears as a focal hypoechoic area, which can be easily located. Pattern of internal composition of abscess varied from homogenous to heterogeneous, depending up on the amount of cellular debris. Edges of abscess cavity were well or ill-defined, depending upon the duration of abscess. However, sonographic appearance of cellulitis was found to be nonspecific. Ultrasound can very accurately measure the size and depth of abscess cavity from the skin. All this information will help the clinician to do proper and effective treatment of odontogenic infections. For further confirmation of the findings of this study, clinical trials with more number of cases may be undertaken.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2]