September 21, 2011

Intussusception: Ultrasound

A longitudinal US image shows a "pseudokidney" sign of intussusception (arrows). Arrowheads point to enlarged mesenteric lymph nodes within the intussusceptum.

A transverse US image shows a "target" sign with a hypoechoic ring of the intussuscepiens surrouning the central echogenic area of intussusceptum. Arrowheads point to enlarged nodes.

  • A segment of bowel (intussusceptum) prolapses into a more distal bowel segment (intussuscepiens)
  • Most frequently seen in the first two years of life but can be seen up to 4 years. If older child has intussusception, looks for a lead point such as polyp, Meckel diverticulum, lymphoma, duplication cyst.
  • Classic triad: colicky pain, vomiting and bloody (red currant jelly) stools (seen in less than 25% of cases)
  • X-ray is positive in only 50% of cases, and is not reliable in diagnosing this condition

Ultrasound Findings
  • Modality of choice to diagnose intussusception
  • "Target" sign = hypoechoic ring with an echogenic center on transverse US image
  • "Pseudokidney" sign = hypoechoic bowell wall extending along a hyperechoic mucosa
  • Helpful in searching for a lead point. US can provide a specific diagnosis in one-third of these cases.

1. Daldrup-Link HE, Gooding CA. Essentials of Pediatric Radiology: A Multimodality Approach, 2010.
2. Hodler J, Von Schulthess GK, Zollikofer CL. Diseases of the Abdomen and Pelvis 2010-2013: Diagnostic Imaging and Interventional Techniques, 2010.

September 11, 2011

Tension Pneumothorax

Chest radiograph shows a very large left pneumothorax (stars) causing mass effect to the mediastinum (shifting, arrows), deep costophrenic sulcus and collapsed left lung.

  • One-way valve effect causing continuous air collection within pleural space resulting in collapse of the lung on the affected side and compression of opposite lung
  • Poor lung compliance and increased airway pressure leads to ineffective gas exchange
  • Mass effect on mediastinal structures cause decreased venous return and decreased cardiac output
  • Symptoms and signs: chest pain, dyspnea, respiratory distress, tachypnea, dyspnea, cyanosis, elevated jugular venous pressure, absent breath sounds, tracheal deviation and hemodynamic compromise
  • This is a clinical diagnosis and confirmation with radiography is not recommended. Needle decompression should be immediately performed
  • Again, this is a clinical diagnosis. Yet imaging may be performed and shows large pneumothorax, mediastinal shifting, flat hemidiaphragm
Greenberg MI. Greenberg's Text-atlas of Emergency Medicine, 2005.

September 1, 2011

Fracture of the Lateral Process of Talus

AP view of the foot shows a small avulsion fracture (arrow) of the lateral process of the talus.

Facts: Lateral Process of Talus
  • Lateral process is a broad-based, wedge-shaped prominence of the lateral talar body that articulates with the fibula and posterior facet of talus
  • Anchor point for lateral talocalcaneal, anterior and posterior talofibular ligaments
Facts: Fracture of the Lateral Process of Talus
  • Axial loading with elements of dorsiflexion and eversion or external rotation
  • High incidence among snowboarders, sometimes called "snowboarder fracture"
  • Can be difficult to diagnose clinically, easily confused with ankle sprain
  • Pain localized anteroinferior to the distal end of fibula
  • Important to look specifically at this area in patients presenting with lateral ankle pain following trauma
  • Small, nondisplaced fracture can be overlooked. CT may be warranted if suspicion persists in a normal-looking x-ray series
  • Hawkins classified this fracture into 3 types: 1) large single fragment, 2) large comminuted fragment, 3) small, extra-articular fragment
Browner BD, Levine AM, Jupiter JB, et al. Skeletal Trauma: Basic Science, Management, and Reconstruction, 2009.