Blunt Traumatic Colon Perforation

Axial non contrast CT image of the abdomen shows a localized collection of air and high-density fluid (C) medial to the ascending colon (AC) and the site of colonic wall discontinuity (between arrows). Note skin and subcutaneous swelling/contusion of the right flank. 

Sagittal-reformatted CT image shows similar findings as  on the axial imaging. The entire length of the ascending colon (AC) is better appreciated and the collection (C) is located posteromedial to the colon within the retroperitoneal space. Colonic perforation was confirmed at surgery. 

Facts:

• Uncommon injury in blunt trauma
• Severe direct force is usually required to produce this injury, mostly from motor vehicle collision
• Often associated with other injuries, both intra- (liver, spleen, small bowel mesentery) and extra-abdominal (skeletal, facial, neurologic)
• CT may not be 100% sensitive. Findings could be overlooked in multiply-injured patients, large patients or if metallic monitoring/support devices are obscuring the area.
• "Normal" CT could be misleading when other factors such as physical examination is not taken into account. Re-review of images to look for subtle free fluid/air is essential in these cases.

CT Findings:

• Discontinuity of bowel wall
• Extraluminal contrast leakage
• Extraluminal air either intra- or retroperitoneal (nonspecific, can be seen after DPL, mechanical ventilation, barotrauma, etc)
• Intramural air
• Bowel wall thickening
• Bowel wall enhancement
• Mesenteric fat stranding
• Intraperitoneal and retroperitoneal fluid

References:

1. Barden BE et al. Perforation of the colon after blunt trauma. South Med J 2000;93(1)
2. Brody JM, et al. CT of blunt trauma bowel and mesenteric injury: typical findings and pitfalls in diagnosis. RadioGraphics 2000;20: 1525

Silicone Granulomas

MLO mammographic view of the left breast shows diffuse, markedly increased breast density throughout from prior direct silicone injection for breast augmentation. 

Transverse view of ultrasound of the left breast shows a cystic lesion (arrow) and multiple several lesions that has ill-defined borders and posterior acoustic shadowing (short arrows), representing silicone granulomas.

Axial non contrast CT shows multiple isodense soft tissue nodules in both breasts, some with thin rim of calcifications. 

Breast Augmentation with Direct Silicone Injection

• Was done in the USA in 1950s to 1960s but later prohibited in 1970s by the US FDA
• Liquid form of silicone was directly injected into breast parenchyma
• Adverse effects include lymphadenopathy, infection, formation of granulomatous masses (siliconoma) and fibrosis
• They make cancer difficult to find on physical examination and mammography 

Imaging Appearance of Free Silicone

• Ultrasound: variable appearance including 1) classic = highly echogenic pattern of scattered and reverberating echoes or "snowstorm" appearance, 2) lesion with acoustic shadowing, 3) hypoechoic masses almost indistinguishable from cysts surrounded by echogenic noise
• Mammography: distortion of breast parenchyma with increase density of the breast
• CT: soft tissue nodules with rim calcification
• MRI: low signal intensity on T1W with fat suppression, high signal intensity on T2W with water-suppression

Reference:

Caskey CI et al. Imaging spectrum of extracapsular silicone: correlation of US, MR imaging, mammographic and histopathologic findings. RadioGraphics 1999;19:S39-S51

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.