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A 10-day-old infant presented with hematuria. Multiple CT images show a large heterogeneous mass originating from the lower pole of the right kidney (cortical beak sign noted, pink arrow). The mass extends into the right renal pelvis and causes mild hydronephrosis.
Facts

• Synonyms: mesoblastic nephroma, leiomyomatous hamartoma, mesenchymal hamartoma, renal fibroma, Bolande tumor.
• It is the most common solid renal tumor in the newborn.
• This tumor is believed to arise from metanephric blastema or secondary mesenchyme.
• Patients usually presents with a palpable flank mass.
• Prognosis is excellent with nephrectomy and wide resection

Imaging Findings

• Large solid intrarenal mass, which typically involves or extends to the renal sinus.
• Hemorrhage, necrosis or cystic portions are uncommon.

Table: Age Presentation of Renal Tumors in Children


References

1. Donnelly LF. Diagnostic imaging pediatrics. Amirsys. Manitoba. 2005.2. Lowe LH, Isuani BH, Heller RM, Stein SM, Johnson JE, Navarro OM, Hernanz-Schulman M. Pediatric renal masses: Wilms tumor and beyond. Pediatric renal masses: Wilms tumor and beyond. Radiographics. 2000; 20:1585-603.

Axial CT image shows subpleural reticulation at the periphery of the lung bases bilaterally. Also note thin linear subpleural lines paralleling the pleural surface (arrowheads). There are several calcified pleural plaques in the diaphragmatic pleura (star).
Facts:

• Only asbestos fibers of 20-150 um in length can reach lower respiratory tract and cause diseases
• Asbestos bodies are formed by macrophages phagocytose the fibers
• Pulmonary fibrosis develops initially in peribronchiolar region and then spreads along peribronchovascular and septal connective tissues, predominantly in the lower lung zones. Cicatricial emphysema and traction bronchiectasis finally ensues.
• Patients usually present late after initial exposure (up to 20 years)

Imaging Findings

• Difficult to discern on radiograph because pleural involvement often is more conspicuous and may obscure early lung findings
• Dot-like opacities in subpleural lung may be an earliest CT finding of asbestosis
• Curvilinear subpleural lines (as in our case) are lines running parallel to and a few millimeters beneath the pleural surfaces
• Thickening of interlobular septa and intralobular lines
• Traction bronchiectasis and honeycomb lungs (late)

Reference:

Lange S, Walsh G. Radiology of chest diseases, 3rd ed, 2007.

An ultrasound image shows an echogenic thrombus and absence of color flow in the right axillary veins (arrows).
Facts: Upper Extremity Deep Vein Thrombosis

• Secondary form (more common) is believed to be due to intimal injury, venous stasis and hypercoagulability. Primary form (Paget-von Schrotter syndrome) occurs in young adults due to underlying chronic venous compressive abnormality caused by musculoskeletal structures in the costoclavicular space
• Axillosubclavian vein most common location because it is relatively fixed in the thoracic outlet, therefore it is exposed to repeated trauma with arm movement
• Etiology: central venous catheter (CVC), permanent cardiac pacer, mediastinal tumors, radiation, surgery, hypercoagulable states
• Increasingly common. 8% of all DVTs
• Complications: pulmonary embolism, SVC syndrome, postthrombotic venous insufficiency, loss of vascular access
• The most powerful independent predictor of UEDVT = presence of CVC (increases the risk by 7 folds)
• Other risk factors in patients without CVC: young age, lean body weight and inpatient status

Imaging

• US is the imaging modality of choice
• US shows lack of compressibility, absence of color flow signal and augmentation, visualization of thrombus
• Radiography may show cervical rib, fractured rib or clavicle

References:

1. Joffe HV, Kucher N, Tapson VF, et al. Upper-extremity deep vein thrombosis: a prospective registry of 592 patients. Circulation 2004;110:1605-1611.

2. Greben C and Charles HW. Deep vein thrombosis, upper extremity. In eMedicine, updated Jul 28, 2009.

Lateral radiograph of the wrist shows a volar dislocation of the lunate (arrow) relative to the position of the radius (R) and capitate (C).
Facts: Lunate Dislocation

• "Spilled teacup" sign (as seen on this lateral radiograph)
• Final stage of perilunate injuries
• Most severe form of perilunate injuries, highest degree of instability
• On lateral view of the wrist, the line drawn along the axis of distal radius, lunate and capitate should be almost straight. In this case, the line is disrupted because lunate is dislocated volarly.

Reference:Kaewlai R, Avery LL, Asrani AV, et al. Multidetector CT of carpal injuries: anatomy, fractures, and fracture-dislocations. Radiographics 2008;28:1771-1784.

Coronal CT images show dilated gallbladder (GB), thickened wall, mucosal hyperenhancement with an obstructing cystic duct stone (arrow) in a 57-year-old man who presents with acute abdominal pain.
Facts: Acute Cholecystitis

• It is a difficult clinical diagnosis. Potential clinical signs that can be helpful to rule in the diagnosis are 1) Murphy sign (positive likelihood ratio = 2.8), 2) RUQ tenderness
• Diagnosis requires a combination of clinical, lab and imaging tests.
• No single clinical finding or lab test has sufficient weight to establish or exclude cholecystitis without further testing (eg, imaging)
• Evaluation of patients with abdominal pain suggestive of cholecystitis continues to rely heavily on the clinical gestalt and diagnostic imaging

Facts: Acute Cholecystitis CT Findings

• Gallbladder distention*
• Wall thickening*
• Mucosal hyperenhancement
• Pericholecystic fat stranding or fluid
• Gallstones (with sufficient attenuation difference from bile to be visualized)
• CT rim sign (increased enhancement of hepatic parenchyma in the gallbladder fossa)
• CT is less accurate than ultrasound in establishing or excluding cholecystitis. However, CT is better to show complications of cholecystitis such as emphysema, gangrene, perforation, abscess or hemorrhage.

* In one study (ref #3), distended gallbladder was considered when size greater than 5 x 8 cm, and thickened wall when greater than 4 mm in noncollapsed gallbladder (short axis greater than 2 cm).
References:1. Trowbridge RL, Rutkowski NK, Shojania KG. Does this patient have acute cholecystitis? JAMA 2003;289:80-86.2. Shakespear JS, Shaaban AM, Rezvani M. CT findings of acute cholecystitis and its complications. AJR 2010;194:1523-1529.3. Fidler J, Paulson EK, Layfield L. CT evaluation of acute cholecystitis: findings and usefulness in diagnosis. AJR 1996;166:1085-1088.

Ultrasound images show enlarged ovaries with multiple cysts in a woman who had received assisted reproduction procedure. Ascites is also present but not shown on these images.
Facts: Ovarian Hyperstimulation Syndrome (OHSS)

• Complication related to exogenous administration of human chorionic gonadotropin (HCG) for assisted reproduction
• Believed to be due to increased capillary permeability, resulting in fluid shift from intravascular to extravascular compartments
• Broad clinical spectrum, ranging from mild, moderate to severe, but can be life threatening
• Common in mid- to late-luteal phase
• Early signs: abdominal heaviness, tension and pain (due to bilateral ovarian enlargement with multiple cysts)
• Risk factors: young patient (less than 30 years old), underlying polycystic ovaries, high number of follicles and estradiol levels at the time of HCG injection, protocols that utilize GnRH
• Golan classification describes 5 grades of OHSS based on ovarian size, symptoms (abdominal distention, nausea, vomiting, dyspnea), signs (ascites, pleural effusion, hemoconcentration, hypovolemia, oliguria).

Imaging

• Ultrasound most appropriate imaging to confirm clinical suspicion
• Enlarged ovaries with several cysts
• Ascites, pleural effusion
• Necklace sign (string of ovarian follicles close to the surface of the ovary) may indicate an increased risk of developing this syndrome

Reference:1. Gianaroli L, Ferraretti AP, Fiorentino A. The ovarian hyperstimulation syndrome. Reproductive Med Rev 1996;5:169-184.2. Golan A, Ron-El R, Herman A, et al. Ovarian hyperstimulation syndrome: an update review. Obstet Gyncol Surv 1989;44:430-440.

Chest radiograph reveals dilatation of the main pulmonary artery with relatively normal-sized right and left pulmonary arteries. The aorta is left sided.
Facts: Pulmonary Valvular Stenosis

• Common congenital heart defects, approximately 10% of all cases
• Classified as subvalvular, valvular and supravalvular stenosis (based on level of obstruction) and as mild, moderate and severe (based on pressure gradient across stenosis). It can occur in branch pulmonary arteries as well
• May occur in isolation (as in our case) or be associated with other complex congenital heart defects
• In severe cases, physical and ECG findings of right axis deviation, right ventricular hypertrophy would be apparent

Imaging Findings

• Cardiac ultrasound: obstruction at right ventricular outflow tract (RVOT), pulmonary valve (PV), main pulmonary artery, right and left pulmonary arteries, abnormal pulmonary valve annulus, abnormal pressure gradients across RVOT, PV and pulmonary arteries
• Radiography: enlargement of the main pulmonary artery, right ventricular hypertrophy. Radiographic differential diagnoses are pulmonary hypertension, idiopathic dilatation of the pulmonary trunk

Our case - pulmonary valvular stenosis in a young woman who had the diagnosis since birth and had undergone valvulotomy.
References1. Heiden K. Congenital heart defects, simplified. 20092. Castaner E, Gallardo X, Rimola F, et al. Congenital and acquired pulmonary artery anomalies in the adult: radiologic overview. Radiographics 2006;26:349-371.

Chest radiograph shows a large lucent area in the right upper lobe with compression of the remaining lung parenchyma. In a patient with acute symptoms and no previous radiograph for comparison, this may raise a diagnostic dilemma whether it represents localized pneumothorax or just a giant bulla.
Coronal-reformatted CT image confirms the absence of pneumothorax in this case. Several bullae are clearly visualized.

Facts: Bulla, Giant Bulla

• Air-filled space in the lung parenchyma due to destruction of alveolar tissue, distal to terminal bronchiole
• Larger than 2 cm in distended state
• Bullae + emphysema = bullous emphysema (can be congenital or complication of COPD)
• Giant bulla = bulla larger than one third of the hemithorax size and compression of adjacent lung parenchyma

Distinguish Giant Bulla from Pneumothorax

• Important for treatment plan (bulla - no tube thoracostomy; pneumothorax - may need tube thoracostomy if large or symptomatic)
• Differentiation can be difficult on conventional radiography; they can coexist
• Helpful signs for pneumothorax: visible visceral pleural line
• Expiratory chest radiograph may help delineating a visceral pleural line of pneumothorax
• CT scan is the most accurate mean to differentiate the two diagnoses
• "Double wall" sign described in cases with ruptured bulla causing pneumothorax (air outlining both sides of the bulla wall parallel to the chest wall)

Lesson: Don't be shy to ask for a CT scan in this scenario. It is better to "do right" than "be right". The treatment is very different, and remember that the two diagnoses can coexist.

Reference:Waseem M, Jones J, Brutus S, et al. Giant bulla mimicking pneumothorax. J Emerg Med 2005;29:155-158.

Sagittal-reformatted CT image of the lower thoracic spine shows a central disc calcification. Several levels of endplate changes are noted as well.
Commonly Found in Elderly

• Found in 80% of elderly cadavers in a large study
• Mostly located in the periphery of the disc (annulus fibrosus), followed by central and diffuse
• Mostly in lower thoracic spine, followed by midthoracic and lumbar spine
• Increase in prevalence with increasing age

Differential Diagnosis

• Degenerative disc
• Postoperative, post-traumatic
• Arthritis: ankylosing spondylitis, CPPD, gout
• Metabolic disease: ochronosis, hemochromatosis, hypervitaminosis D

Reference:

Chanchairujira K, Chung CB, Kim JY, et al. Intervertebral disk calcification of the spine in an elderly population: radiographic prevalence, location, and distribution and correlation with spinal degeneration. Radiology 2004;230:499-503.

Sagittal CT image of the neck shows a cystic mass (arrow) in the midline anterior to the hyoid bone (arrowhead) in a young male patient.
Facts:

• Cystic lesion in the midline of the anterior neck near the hyoid bone
• Common, accounted for 70% of all congenital neck mass
• Usually is mobile, midline or slightly off midline
• Can be anywhere along the route from foramen cecum to the lower neck (a path the thyroid gland descends to reach the anterior trachea). But most are below the level of hyoid bone
• Treatment involves removal of the entire duct, part of the hyoid bone and tissue at the base of tongue

Differential Diagnosis

• Dermoid cyst
• Liquefied submental or anterior cervical lymph node

Reference:Seibert J, James C. Pediatric Radiology Casebase, 1997.

Axial CT image shows a small well-defined hyperdense lesion (arrow) in the gray-white matter junction of the left posterior parietal lobe without evidence of mass effect or surrounding edema.Axial T2W MR image shows the lesion predominantly high signal intensity with a complete ring of dark T2 signal, suggesting the presence of hemosiderin.
Facts: Cavernoma

• Low-flow vascular anomaly of the brain
• Endothelium-lined blood cavities without muscular or adventitial layers. No brain tissues present between these blood cavities
• May be sporadic, related to prior radiation, or hereditary
• Patients commonly present with seizures due to internal bleeding
• Annual bleeding rate between 0.25 to 0.7% per year
• On follow up, most cavernomas increase in size due to osmotic changes
• 80% are supratentorium, and size between 1-2 cm

Imaging

• Appearance depends on amount of internal thrombosis, hemorrhage and calcification
• MRI is the modality of choice because it can show various stages of bleeding in the lesion, which is characteristic for cavernoma
• If presents with acute hemorrhage, CT appearance will be similar to intracerebral hemorrhage of other causes. MRI in acute phase may provide a clue to the diagnosis of cavernoma if it shows various stages of bleeding in particular the presence of hemosiderin
• If presents incidentally, cavernoma appears as a hyperdense mass without causing mass effect on CT. If calcified, it will be only partially calcified. On MRI, it shows a complete ring of dark T2 signal due to the presence of hemosiderin (this effect is best seen on GRE T2* sequence)

Reference:

Kuker W and Forsting M. Cavernomas and Capillary Telangiectasias. In: Baert AL, Knauth M, Sartor K. Intracranial Vascular Malformations and Aneurysms, 2nd revised edition, 2008

Tc-99m MAG3 renal scan of a renal transplant recipient, day 1 after transplant with oliguria, shows delayed excretion of tracer from the transplant kidney. Images in vascular phase (not shown) are normal (normal perfusion and uptake).
Facts

• May occur immediately or after an initial short period of allograft function
• Related to both donor and recipient factors
• More common in cadaveric kidneys of older donors who sustained warm ischemia time or prolonged hypotensive periods
• Presented with oliguria or anuria early after transplant
• Diagnosis made by exclusion of other factors. Traditional signs (tubular casts, low urine osmolality) not reliable if patients with native partially functioning kidneys
• Treatment: supportive, return to dialysis if anuric (expected recovery of renal function usually within 3 weeks)

Renal Scan

• Normal perfusion, variable uptake but no (or delayed) excretion
• Serial scans helpful in determining viability of oliguric kidneys, predicting recovery or deterioration

Reference:

Resnick MI, Older RA. Diagnosis of Genitourinary Disease, 2nd edition, 1997

Axial CT image shows a large partially thrombosed aneurysm of the right renal artery, which is extraparenchymal. On other images, the aneurysm is saccular, and appears to arise from the segmental artery.
Facts:

• True aneurysms involve all layers of the artery and usually inherited. They can be fusiform or saccular, and are more commonly extraparenchymal in location. Example: fibromuscular dysplasia, Ehlers-Danlos
• False aneurysms involve only some layers of the artery, usually are acquired and saccular. Examples: trauma, iatrogenic, dissection, mycotic
• Intrarenal aneurysms are intraparenchymal, can be either true or false aneurysm. Examples: polyarteritis nodosa, tuberculosis, neurofibromatosis

Indications for Intervention

• Symptomatic: rupture, pain, ischemia, infarction, hypertension
• Diameter more than 2 cm, enlarging or dissection
• Female patient who is pregnant, or contemplating pregnancy

Our case: False aneurysm probably due to dissection, surgical removal was performed in this symptomatic patient
Reference:Lew WK, Weaver FA, Otero CA, et al. Renal artery aneurysm. E-medicine, updated September 17, 2008

Case Contributor: Gopalaratnam Balachandra, M.D.Editor: Rathachai Kaewlai, M.D.

Coronal T1W and T2W MR images of the brachial plexus show a fusiform-shaped mass (large arrows) along the course of the right cervical nerve root (small arrow). The mass demonstrates heterogeneous low T1 and high T2 signal intensity. It has smooth, well circumscribed borders.
Axial T1W post contrast MR image shows heterogeneous enhancement of the mass (arrows) with a central area of non-enhancement.
Facts: Primary Brachial Plexus Tumor

• Rare tumor, most commonly benign with good prognosis after surgical resection
• Clinical presentations: pain, paresthesia, palpable mass
• Common pathology: schwannoma, neurofibroma. Other possibilities: malignant peripheral nerve sheath tumor (MPNST), desmoid, ganglion, epidermoid

Imaging

• MRI is the study of choice to delineate the margins of tumor from surrounding tissues
• Characteristic feature on any imaging techniques is close relationship with the parent nerve, which helps to exclude other possibilities such as lymphadenopathy, vascular anomalies, etc.
• Low signal on T1, high signal on T2 and heterogeneous enhancement
• MRI cannot differentiate schwannoma from neurofibroma

This case - Schwannoma of the brachial plexus in a 32-year-old woman who presented with pain in the right arm and right neck mass.
References:

1. Binder DK, Smith JS, Barbaro NM. Primary brachial plexus tumors: imaging, surgical, and pathological findings in 25 patients. Neurosurg Focus 2004;16.

2. Rettenbacher T, Sogner P, Springer P, et al. Schwannoma of the brachial plexus: cross-sectional imaging diagnosis using CT, sonography, and MR imaging. Eur Radiol 2003;13:1872-1875.

About Case Contributor: Dr. Balachandra is the head of the Department of Radiology at Government General Hospital in Pondicherry, S. India.

Supine radiographic study of a 41-year-old woman shows a focally dilated loop of large bowel (star) in the right side of the abdomen. There is little gas in the more distal colon.Axial CT image shows a dilated right colon (star) with a transition point with a 'whirl-like' appearance (shown on contiguous images) in the mid abdomen (arrow). The rest of the colon is not dilated. Findings are most concerning for closed loop obstruction.
Facts: Closed Loop Obstruction of the Colon

• Colonic obstruction is rarely caused by postoperative adhesion (less than 1%). It is most commonly due to tumor
• CT should be the next imaging work-up to look for a mass. Contrast enema should be omitted due to the risk of perforation
• Closed loop obstruction of the colon usually is due to volvulus, which can be sigmoid (80%), cecal (15%) or involving the transverse colon (5%). Long mesocolon can predispose to malrotated cecum and result in a bascule or volvulus
• Signs of closed loop obstruction on imaging include focally dilated bowel loop with little gas distally and proximally, transition point with a whirl-like appearance at the mesenteric root, mesenteric haziness and free fluid

Our case: transverse colonic closed loop obstruction due to extralong colonic mesentery
Reference:Halpert RD. Gastrointestinal imaging case review series, 2nd ed, 2008.

Ultrasound image of the right ovary shows a well-circumscribed complex mass (arrows) with cystic and solid components (arrowheads) in a 66-year-old woman with abnormality seen on CT scan.
Facts: Complex Ovarian Mass

• Long list of potential causes, encompassing tumor (primary and neoplastic), inflammation and infection in a postmenopausal woman
• Potential tumors: serous and mucinous cystadenoma/cystadenocarcinoma, teratoma, clear cell carcinoma, endometrioid carcinoma, necrotic primary or metastatic tumors
• Most of these (if we think it is neoplasm) would need to be diagnosed histologically because imaging findings are nonspecific and malignancy cannot be excluded

Facts: Brenner Tumor

• Uncommon ovarian neoplasm, usually incidentally found
• Women in 5th to 7th decade of life
• Predominantly solid, but can be complex with cystic components when associated with serous and mucinous cystadenomas (seen in up to 30% of cases)
• Can be benign, borderline or malignant

Our case: Brenner tumor with struma ovarii on histology.
Reference:

Green GE, Mortele KJ, Glickman JN, Benson CB. Brenner tumors of the ovary sonographic and computed tomographic imaging features. J Ultrasound Med 2006;25:1245-1251.

PA and lateral chest radiographs demonstrate anatomic position of three heart valves, A = aortic, M = mitral and T = tricuspid, in a patient with rheumatic valve disease. Note that the tricuspid prosthesis is an annuloplasty.
Facts

• The three heart valves (aortic, mitral and tricuspid) commonly overlap each other on frontal radiograph. Correct radiographic identification can be difficult.
• To differentiate the mitral from aortic valve on lateral view, one draws a line from the junction of the sternum and diaphragm to the carina. This line normally intersects aortic valve*. The valve below the line is mitral valve. The tricuspid valve is the one to the mitral valve.
• Without a lateral view, the best criterion for use in differentiating between aortic and mitral prostheses is the direction of flow (discernable in Starr-Edwards and most Bjork-Shiley prostheses). Orifice (en face or in profile) and orientation (vertical or horizontal) of prosthesis are less reliable.

* This may not always be true in patients who have deformed anterior chest wall or markedly enlarged right ventricle.
Our patient's mitral and aortic prostheses are disc type, so their direction of flow was not discernable.
Reference:1. Gross BH, Shirazi KK, Slater AD. Differentiation of aortic and mitral valve prostheses based on postoperative frontal chest radiographs. Radiology 1983;149:389-391.2. Miller SW, Boxt LM, Abbara S. Cardiac Imaging the Requisites, 3rd edition, 2009.

Author: Santip Srisuwan, M.D.
Fig. 1: Chest radiograph of an asymptomatic young woman shows small right lung volume with cardiomediastinal shift toward the right side, small right hilum and a characteristic scimitar-shaped structure in the right lower lobe (arrow).

Figs 2&3: Contrast-enhanced CT images (maximal intensity projection, and 3D volumetric images) show an anomalous right lower lobe pulmonary vein (arrows) descending vertically, draining the right lower lobe and entering the IVC.
Facts: Scimitar Syndrome

• Also known as venolobar syndrome, hypogenetic lung syndrome
• Associations: congenital heart disease 25% (usually atrial septal defect)
• Symptoms: usually asymptomatic. Patients may have dyspnea if there is a large left to right shunt

Imaging Findings

• Small right lung
• Diminutive right hilum
• Dextroposition of the heart
• Characteristic scimitar vein draining below the diaphragm

Reference:Hansell DM, et al. Imaging of diseases of the chest. Elsevier Mosby, 4th edition, 2005.
About Guest Author: Dr. Santip Srisuwan is a radiologist at Samitivej Hospital, Bangkok, Thailand.

Frontal radiograph of the lumbar spine shows fusion of the sacroiliac joints (arrowheads) and thin syndesmophytes along the lateral borders of the lumbar spine.
Facts: AS

• Prototype of seronegative spondyloarthropathies (SNSA), which is a group of disorders of chronic inflammation of sacroiliac joints and spine
• Frequency: about 0.1% - 6% across different population (most likely toward the lower end)
• Genetic risk factor = human leukocyte antigen (HLA)-B27
• Principal bone/joint abnormalities = sacroilitis, synovitis and enthesitis

Imaging Findings

• Imaging findings are incorporated into the modified New York criteria for ankylosing spondylitis, as one of the four criteria.
• Sacroilitis: pseudowidening, sclerosis, erosions and later ankylosis
• Grading of sacroilitis on radiographs can be viewed here (link to Google Document provided by Schering-Plough Ply)

Modified New York Criteria for ASDefinite AS if 4a or 4b AND any clinical criteria (1-3)1. Low back pain for at least 3 months' duration improved by exercise and not relieved by rest2. Limitation of lumbar spine motion in sagittal and frontal planes3. Chest expansion decreased relative to normal values for age and sex4a. Unilateral sacroilitis grade 3-44b. Bilateral sacroilitis grade 2-4
ReferenceKippel JH. Primer on the rheumatic diseases, 13rd ed, 2008.

Axial CT image shows a multilocular low density collection (arrow) beneath the enlarged right tonsil (arrowhead), which is displaced medially.
Facts: Peritonsillar Infection

• Peritonsillar space is a space between anterior and posterior tonsillar pillar, deep to the tonsillar capsule and below the superior pharyngeal constrictor muscle
• Infection of this space usually arises from tonsillitis or pharyngitis, which can lead to peritonsillar cellulitis or abscess

Differentiation between Cellulitis and Abscess

• Differentiation of cellulitis from abscess has a clinical value, since cellulitis is treated medically but abscess usually requires surgical drainage
• Clinical distinction of the two can be difficult; imaging such as contrast-enhanced CT or ultrasound have been utilized for this purpose
• On CT, abscess appears as a cystic/multilocular low density collection with enhancing rim, with or without presence of gas at the center. Cellulitis appears as homogeneous soft tissue swelling with obliteration of fat planes.

References1. Domino FJ. the 5-minute clinical consult 2007, 2007.2. Sakaguchi M, Sato S, Asawa S, Taguchi K. Computed tomographic findings in peritonsillar abscess and cellulitis. J Laryngol Otol 1995;109:449-451.