Pancreatic Divisum

An MRCP image shows abnormal drainage of the main pancreatic duct and ventral duct into the minor papilla.

A diagram shows normal pattern of pancreatic duct drainage (label "normal") and pancreatic divisum. Several variants of pancreatic divisum exist but the "classic/typical" one is the MPD draining into the minor papilla while the VD draining into the major papilla along with the CBD. Santorinicele is a fusiform dilatation of the distal MPD before it enters the minor papilla. 

Facts: Pancreatic Divisum 

• Most common pancreatic anatomic variant, found 7% incidence at autopsy but frequencies differ at ERCP
• Controversial association with recurrent pancreatitis
• Results of non-fusion of ventral and dorsal pancreatic anlagen during embryonic time, therefore the ducts (ventral and dorsal ducts are not fused)
• Dorsal duct drains most of glandular parenchyma through minor papilla
• Ventral duct drains a portion of pancreatic head (including uncinate process) through major papilla

Imaging:

• Definitive diagnosis is made with ERCP. MRCP does have high sensitivity and specificity for diagnosis of divisum
• MDCT with thin section can be used to diagnose pancreatic divisum. Viewing images on PACS is essential for depiction of this condition and the assessment is possible only when the pancreatic duct is visualized.
• Important criterion = Dorsal duct seen from tail and body through the anterior aspect of the head, draining into minor papilla (located anterior to CBD and major papilla) while the ventral duct seen in posterior region of the pancreatic head and drains into duodenum together with CBD. Dorsal duct is larger than ventral duct and they are not communicated with each other. "Dominant dorsal duct sign"

Reference:

Soto JA, Lucey BC, Stuhlfaut JW. Pancreas divisum: depiction with multi-detector row CT. Radiology 2005; 235:503-508. 

Criteria and Consensus Method for Blunt Cervical Vascular Injury (BCVI) Screening with Imaging

According to the updated Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injuries (published on March 2013, Neurosurgery 2013;72), 

• Computed tomography is the imaging study of choice for obtunded or un-evaluable patients with potential cervical spine injuries. (Level I)
• Computed tomographic angiography is recommended to assess for vertebral artery injury in selected patients who meet the modified Denver Screening Criteria after blunt cervical trauma. (Level I)

Currently accepted standard used for BCVI screening is that of Modified Denver Criteria applying to acute trauma patients suffering blunt cervical vascular injury with details listed below. In this post, they have been rearranged from the original description.

Injury Mechanisms/Patterns

• High-energy mechanism causing 1) displaced Le Fort II or III, or 2) complex mandible fracture
• Cervical hyperextension/rotation/flexion injury with 1) midface fracture, 2) complex mandible fracture or 3) closed-head injury and diffuse axonal injury

Symptoms

• Massive epistaxis
• Central or lateralizing neurologic deficit that is unexplained or incongruent with CT
• Transient ischemic attack or stroke after blunt neck trauma

Signs

• Expanding neck hematoma
• Honor syndrome
• Cervical vascular bruit in a patient less than 50 years old with blunt neck trauma
• Seat belt abrasion, hanging bruise, or unexplained contusion or hematoma of neck, resulting in significant cervical swelling or altered mental status

Findings on C-spine NCCT

• Upper cervical vertebral fracture (C1-C3)
• Cervical vertebral fracture extending through the transverse foramen
• Cervical vertebral subluxation
• Cervical spine fracture with cervical hyperextension/rotation/flexion injury

Findings on head NCCT

• Acute or subacute cerebral infarction
• Skull base fracture involving foramen lacerum, sphenoid, mastoid, or petrous bones

References: 

1. Biffl WL, Moore EE, Offner PJ, et al. Optimizing screening for blunt cerebrovascular injuries. Am J Surg 1999;178:517–22; 
2. Cothren CC, Moore EE, Biffl WL, et al. Cervical spine fracture patterns predictive of blunt vertebral artery injury. J Trauma 2003;55:811–3.
3. Neurosurgery 2013;72 Supplement 2. Full-text access is FREE

Solitary Pulmonary Nodule: Definition, DDx, and Evaluation with CT

Axial scan of the lung nodule in mediastinal window reveals a solid component of the nodule without calcification

Axial scan of the lung nodule in lung window shows a lobulated, smooth margin of the nodule

Definition of SPN

• Radiographic opacity of equal to or less than 3 cm
• At least two thirds of margins are surrounded by lung parenchyma
• Exclusion of lymph nodes (not always possible), atelectasis and postobstructive pneumonia

Differential Diagnosis

• Infectious: TB, pneumonia, abscess, fungus, etc
• Neoplastic: benign and malignant
• Vascular: AVM, infarct, aneurysm venous varix, hematoma
• Congenital: bronchogenic cyst, sequestration, bronchial atresia
• Inflammatory: rheumatoid arthritis, Wegener, sarcoidosis, microscopic angiitis
• Lymphatic: lymph node, lymphoma
• Outside the lungs: skin nodule, nipple shadows, rib fracture, pleural lesion
• Miscellaneous: rounded atelectasis, lipoid pneumonia, amyloidosis, etc

CT Evaluation

• Thin-section (1 mm) contiguous images through nodule are suggested
• Both lung and mediastinal windows obtained (lung window for margins/edges, mediastinal window for solid component)
• Low dose (less than 80 mAs) can be used for purpose of nodule characterization

CT Characteristics

• Growth rate: malignancy likely if doubling time = 20-400 days
• Size: malignancy likely if size > 3 cm
• Margin/border/edge: malignancy likely if lobulated, speculated, ragged, halo, notches
• Calcification: attenuation > 200 HU indicates presence of calcium in the nodule. No pattern of calcification specific for malignancy
• Cavitation: malignancy likely if irregular and thick (> 15 mm) wall

Our case: Solitary pulmonary nodule from a metastatic colon cancer

Reference:

Patel VK, Naik SK, Naidich DP, et al. A practical algorithm approach to the diagnosis and management of solitary pulmonary nodules. Part 1: radiologic characteristics and imaging modalities

Focal Hepatic Hot Spot Sign

An axial CT image shows a geographic area of hypervascularity (arrow) in segment IV of the liver. Note enlarged subcutaneous collateral vessels (arrowheads)

Facts: Focal Hepatic Hot Spot

• Focal area of enhancement in segment IV of liver due to presence of SVC obstruction
• Occurs due to portosystemic shunting between SVC and portal vein
• With SVC obstruction, blood may flow through internal mammary vein --> paraumbilical vein --> portal vein 
• Other causes of focal hot spots: Budd-Chiari syndrome (caudate lobe), liver abscess, hemangioma, FNH and HCC

Three Routes of Bypass of Venous Blood in Central Thoracic Venous Obstruction

1. Superior route: from subclavian vein to anterior jugular venous system (occuring in subclavian or brachiocephalic venous obstruction)
2. Posterior route: azygos-hemiazygos and paravertebral systems
3. Anterolateral route: like in our case, this is via anterior intercostal, internal mammary and long thoracic veins to IVC

Reference:

Maldjian PD, Obolevich AT, Cho KC. Focal enhancement of the liver on CT: a sign of SVC obstruction. J Comput Assist Tomogr 1995;19:316-8

Sternal Osteomyelitis

Chest radiograph of a patient who had sternal pain, fever and discharge shows no obvious bony abnormality.

Sagittal STIR and coronal T1W MR images demonstrate bone marrow edema with soft tissue changes in the sternum and right sternoclavicular joint (arrows). 

Facts:

• Uncommon infection of the sternum and sternoclavicular joint
• Usually affecting drug addicts, individuals with history of recent subclavian catheter placement, and patients with chronic debilitating illnesses
• Inciting organisms vary widely depending on demographics
• High failure rates of medical treatment alone. Typical treatment includes surgical debridement and en bloc removal

Imaging

• Radiograph is rarely helpful
• CT may show bone destruction but this may be late because damage begins in the joint. Surrounding soft tissue abnormalities are often a useful sign.
• MRI much more sensitive to detect joint and bone changes that are similar in findings to other areas of bone/joint infection

Reference: 

Shields TW et al. General Thoracic Surgery, 7th edition, 2009.