June 30, 2010

Cortical Desmoid

Lateral view of the knee radiograph shows focal cortical irregularity and thickening at the posterior aspect of the medial condyle of the femur (arrow), consistent with a cortical desmoid. The arrowhead points to a fabella.

Facts: Cortical Desmoid
  • Considered to be an avulsion of the medial supracondylar ridge of the distal femur
  • Occurs only on the posteromedial epicondyle of the femur (insertion of adductor magnus aponeurosis)
  • Common in older children
  • Patients may complain of pain, or being asymptomatic (incidentally detected on radiograph done for other reasons)
  • They may or may not show periosteal reaction; 1-3 cm in size, mixed sclerosis and lucency in the cortex
Helms CA. Fundamentals of skeletal radiology, 3rd edition, 2005.

June 27, 2010

Helical CT for Urolithiasis

A coronal-reformatted CT image (without IV contrast) shows an obstructing right ureterovesical junction (UVJ) stone (arrow), causing hydroureteronephrosis. There is enlargement of the right kidney with perinephric stranding (arrowheads) as a result.

  • Urolithiasis incidence in the U.S. and Europe approximately 0.1% - 0.4% of population
  • Male to female ratio = 3:1
  • Peak age during third to fifth decade of life
  • Recurrence rate about 75% during 20 years
Detection Rates by Various Imaging Methods
  • Conventional radiography 50-70%
  • Intravenous urography (IVU) 70-90%
  • Ultrasound 50-60%
  • Normal-dose CT: sensitivity 94-100%, specificity 97%
  • Low-dose CT: sensitivity 95%, specificity 95%
Advantages of CT over IVU
  • Shorter examination time
  • Avoid cost and complications of IV contrast
  • Greater sensitivity for stone detection
  • Higher potential for detection of abnormalities unrelated to stone disease
  • Study directly compared low-dose (<>
  • Meta-analysis of 7 studies of low-dose CT in 1061 patients showing 95% sensitivity and specificity for stone diagnosis
1. Liu W, Esler SJ, Kenny BJ, et al. Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent. Radiology 2000;215:51-54.
2. Niemann T, Kollmann T, Bongartz G. Diagnostic performance of low-dose CT for the detection of urolithiasis: a meta-analysis. AJR 2008;191:396-401.

June 24, 2010

Hook of Hamate Fracture

Figure 1: Frontal radiograph of the right wrist shows no apparent fracture. In retrospect, there may be slight indistinctness of the "eye" of the hamate hook.
Figure 2: Axial CT image at the level of the hamate shows a nondisplace fracture near the base of the hamate hook (arrow).

  • Uncommon fracture that is easily missed on radiography
  • Hook of hamate fracture is more common than fracture of the hamate body
  • Direct blow to the hook, or avulsion of transverse carpal ligament and pisohamate ligament
  • Presenting with pain on ulnar side of the palm aggravated by grasp, point tenderness over the hook at 1 cm distal and radial to the pisiform
  • Best seen on carpal tunnel view (radiography) or CT
  • If displaced and untreated, avascular necrosis and nonunion may occur.

Imaging Features
  • On frontal radiograph, there is absence or indistinctness of the "eye" of hamate (oval, dense cortical ring shadow over the hamate)
  • On CT scan, the fracture line is apparent at the hook best seen on axial images. It can involve the tip or the base of the hook

Singh AK, Kaewlai R. Extremity Trauma. In: Soto and Lucey's Emergency Radiology the Requisites, 2008.

June 21, 2010

Adrenal Cortical Carcinoma

Axial CT image shows a 5-cm heterogeneous left adrenal mass (arrows) with ill-defined border anterolaterally, and a liver mass (arrowhead).

Facts: Adrenal Cortical Carcinoma (ACC)
  • Rare tumor, 0.5 to 2 cases per million population
  • Bimodal age peak - young children, and adults in 4th to 5th decades
  • Male = female
  • Tumor arises from adrenal cortex; 50% produces hormones (cortisol, androgens)
  • Most common site of metastasis: liver and lung
Adrenal Masses: Size Matters
  • Mass less than 2 cm: incidence of malignancy 1%
  • 2-4 cm: 3% - 8%
  • 4-6 cm: 8% - 25%
  • Greater than 6 cm: 40% - 80%
Imaging Features
  • CT or MRI can suggest the diagnosis if there is malignant feature: venous invasion and/or capsular invasion, metastasis to lymph nodes or other organs.
  • Mass usually is large, 70% of ACC are larger than 6 cm on imaging
  • Usually heterogeneous after contrast administration
  • 30% are calcified (usually central)
  • Enlarged lymph nodes seen in 1/3 of cases (usually at high para-aortic or paracaval)
  • MRI may be used as an adjunct to CT for delineation of IVC invasion and extension
Our case: adrenal cortical carcinoma

1. DeVita VT, et al. DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology, 8th edition, 2008

2. Husband JE, Reznek RH. Imaging in Oncology, Volume 1, 2nd edition, 2004.

June 18, 2010

Pneumoperitoneum: Right Upper Quadrant Features

A scout CT image shows a linear gas in the right upper quadrant running in an inferolateral to superomedial orientation (arrows). There is gas in the left colonic wall (arrowheads).

Facts: Pneumoperitoneum on Upright Radiograph
  • As little as 1mm of free gas can be detected on radiography in an upright position with a horizontal x-ray beam
  • If the patient cannot stay upright, a lateral decubitus (preferably patient on the left side) can be performed. Free gas will collect between lateral liver margin and abdominal wall
  • Best chance of detection of free gas is when the radiograph is taken after the patient remains in an upright (or lateral decubitus) position for 10 minutes
Facts: Pneumoperitoneum on Supine Radiograph
  • More difficult to detect
  • Large free gas can be seen indirect as gas collect in different locations
  • Right upper quadrant features include 1) linear gas collection running in an inferolateral to superomedial orientation (representing gas in subhepatic space, as in our patient), 2) triangular gas collection right to the spine above the kidney shadow (gas in most posterior recess of the Morrison pouch)
  • Visualization of the outer wall of intestine (Rigler's sign)
  • Visualization of the falciform ligament of the liver
Our case: pneumoperitoneum due to perforated ischemic colitis.


1. Eisenberg RL. Gastrointestinal Radiology: a Pattern Approach, 4th edition, 2003.

2. Menuck L, Siemers. Pneumoperitoneum: importance of right upper quadrant features. AJR 1976;127:753-756.

June 15, 2010

Left Atrial Enlargement

A frontal chest radiograph shows double density to the right of the spine (short arrows) and convex border of the left atrial appendage (long arrows).
A lateral view of the chest shows posterior displacement of the left mainstem bronchus by an enlarged left atrium (arrowheads).

Signs of Left Atrial Enlargement (LAE) on Chest Radiography
  • Convex left atrial appendage
  • Double density on the right side of the spine (one of the earliest signs)
  • Double density on the left side as the left atrium extends into the left lower lobe
  • Posterior displacement of the left mainstem bronchus posteriorly on lateral view, and superiorly on frontal view
  • Spreading of the carina
Common Causes of LAE
  • Acquired: mitral valve disease (stenosis or regurgitation), left ventricular failure, left atrial myxoma
  • Congenital: VSD, PDA, hypoplastic left heart complex
Our case: severe mitral regurgitation

Miller SW, Boxt LM, Abbara S. Cardiac Imaging the Requisites, 2009, 3rd edition.

June 12, 2010

Intrabronchial Malposition of Nasogastric Tube

Supine chest radiograph in an ICU patient shows the tip of an NG tube in the right lower lobe bronchus (arrow). New opacities are seen in the vicinity of the tip of the NG tube, which may represent hemorrhage or aspiration.

  • Incidence in ICU patients between 0.5% - 1.5% of all NG tube placement
  • Right side more common than left, lower lobe more than intermediate bronchus or main bronchus
  • In one study of 14 malpositions, nearly half of the cases had subsequent pneumothorax requiring chest tubes, and the other half experienced pneumonias at the same site
  • Traditional criteria for determining proper positioning of an NG tube (i.e., sound heard over the stomach upon insufflation of air, aspiration of fluid, absence of coughing) may not work well in ICU patients who are usually obtunded, intubated, have impaired gag reflex, decreased laryngeal sensitivity and are on neuromuscular blocking agents.
  • Routine radiography after placement of an NG tube in ICU patients can be helpful for detection of tube malposition
  • Once detected intrabronchial NG tube malposition, one should look for evidence of pneumothorax. If not seen, a close follow up radiograph is recommended since delayed pneumothorax may occur.

Bankier AA, Wiesmayr MN, Henk C, et al. Radiographic detection of intrabronchial malpositions of nasogastric tubes and subsequent complications in intensive care unit patients. Intens Care Medicine 1997;23:406-410.

June 9, 2010

Swimmer's View Lateral Cervical Spine Radiograph

Please click on images to view a larger version
Routine swimmer's view (left images) shows slight anterolisthesis of C7 on T1, in a trauma patient who sustained neck injury but normal CT scan. A repeat swimmer's view focusing at the lower cervical spine was performed and show normal alignment.

Swimmer's View Lateral Cervical Radiograph
  • Usually required to visualize C7-T1 junction. In one study, only 20% of cases receiving five-view cervical radiography (AP, lateral, bilateral obliques and odontoid) C7-T1 can be adequately seen.
  • Downsides of this view are: high dose, high scatter, difficult positioning, usually not adequate on large patients or patients with shoulder injuries
  • To visualize C7-T1 junction, one should avoid arm pulling in patients who sustained a cervical spine injury
Current Practice
  • Now, most places replace cervical spine radiography with CT scan because of higher sensitivity for fracture, shorter scan time, and probably less costly (if combined the use of overall resources)
  • Some institutions still perform an out-of-collar lateral radiograph after a negative CT scan to ensure no significant change in alignment that may occur in patients with isolated ligamentous injury not shown on CT. This exam usually includes lateral and swimmer's radiographs.
This case show a subtle malalignment seen on routine C7-T1 junction on a routine swimmer's view. This was cleared by repeating the study with a focus at lower cervical spine. Abnormality on the first image is believed to be due to different centering of x-ray beam and superimposition of structures.

1. Daffner RH. Cervical radiography for trauma patients a time-effective technique? AJR 2000;175:1309-1311.
2. www.Wikiradiography.com

June 6, 2010

Sinonasal Polyposis

Axial CT images of the sinuses show complete opacification of the maxillary, ethmoid and sphenoid sinuses with widening of the sinus ostia (yellow stars) and opacity in the nasal passages (blue stars) in this patient with history of allergic rhinitis.

Facts: Sinonasal Polyposis
  • Common finding in patients with chronic rhinosinusitis (2% - 16% of cases)
  • Soft, yellow-white nasal polyps that consist of edematous stroma with eosinophilic infiltrates, covered by respiratory epithelium
  • Predisposing factors: asthma, fungal sinusitis, Kartagener syndrome, ASA syndrome, cystic fibrosis
  • Can be seen in healthy individual with no predisposition to polyps
  • Usually multiple, bilateral polyps. Majority of polyps arise from uncinate-turbinate-infundibulum space and bulla-hiatus seminularis-infundibulum
  • On CT, there is opacification of the sinuses with widening of the sinus ostium and sinonasal passages
1. Maroldi R, Nicolai P, Antonelli AR. Imaging in Treatment Planning for Sinonasal Diseases, 2005.
2. Yousem DM, Da Motta AC. Head and Neck Imaging Case Review Series, 2nd ed, 2006.

June 3, 2010

Sturge-Weber Syndrome

Axial CT images show "railroad track" calcifications (arrows) in the left occipital cortex with ipsilateral enlargement of the choroid plexus (arrowhead) in this patient with a port-wine stain in the left V1 distribution.

  • Also known as encephalotrigeminal angiomatosis
  • Sporadic disorder affecting skin and central nervous system
  • Defined as capillary malformation of the leptomeninges with or without choroid and facial V1 or V1-V2 involvement (port-wine stain)
  • Probably due to embryonic defect of persistent vascular plexus in the neural tube during 6th week of embryonic development
  • Port-wine stains can be unilateral or bilateral, most commonly involve V1 distribution but can also be extracranial
  • Intracranial involvement always ipsilateral to the port-wine stain of the face, occipital lobe most common
  • MRI more sensitive than CT in identifying secondary changes due to leptomeningeal capillary malformation
  • Cerebral cortical atrophy, compensatory ventricular and choroid plexus enlargement, calvarial hemihypertrophy and superficial gyriform enhancement after gadolinium injection
  • "Railroad track" calcification of the cerebral cortex caused by precipitation of calcium likely due to alternation of vascular dynamics of the leptomeningeal malformation

Gorlin RJ, Cohen MM, Hennekam RCM. Syndromes of the Head and Neck, 4th ed, 2001.
Muller-Forell WS. Imaging of Orbital and Visual Pathway Pathology, 2005.