August 30, 2013

Medial Epicondyle Fracture of the Humerus

AP views of both elbows of an 18-year-old boy who sustained an injury to the right elbow.  There is an avulsion fracture (arrow) of the medial epicondyle of the right humerus. Radiograph of the left side demonstrates different areas of distal humeral structures from medial to lateral: medial epicondyle, trochlea, capitellum and lateral epicondyle. 


  • Common pediatric elbow fracture (3rd common, after supracondylar and lateral condylar fractures)
  • Valgus strain at elbow joint
  • Two main types: simple avulsion (1/2) and fracture-dislocation (occurring with lateral elbow dislocation; 1/2)
  • Indications for surgery include 1) displaced fragment trapped in joint preventing reduction, 2) ulnar neuropathy, 3) valgus instability, 4) open fracture
  • Look for displaced fragment trapped in the joint and degree of displacement because they might indicate surgery
  • In patients less than 8 years, trochlea may be non-ossified and this may be confused with fracture of medial condyle, which is rarer and could be more complicated
  • Another imaging Ddx is osteochondrosis
Wilson JN. The treatment of fractures of the medial epicondyle of the humerus. J Bone J Surg 1960;42:778.
Gottschalk HP, Eisner E, Hosalkar HS. Medial epicondyle fracture sin the pediatric population. J Am Acad Orthop Surgeons 2012; 20:223.
Wheeless' Textbook of Orthopedics link

August 20, 2013

Mosaic Pattern of Lung Attenuation

Axial CT images of the chest in lung windows (inspiratory images) shows multilobular areas of variable lung attenuation (mosaic pattern) with dark areas showing diminished size/numbers of pulmonary vessels indicating that these dark areas are abnormal. 


  • Lobular or multilobular distribution of variable lung attenuation
  • Three possible groups of etiologies: small-airway, vascular and infiltrative disease 
  • Additional findings are helpful to distinguish the three causes
Making Decisions
  1. Dark or white areas are abnormal? Looking at size and number of vessels in both regions. If they are similar, the "white" is abnormal (meaning it is ground glass abnormality). If the size/number of vessels in dark areas are decreased, this is either small-airway or vascular pathology
  2. If the "white" is abnormal, look for differentials of ground glass opacity (GGO)
  3. If the "dark" is abnormal, look at expiratory phase scanning. If air trapping is present, this is small-airway disease. If there is no air trapping, this is likely vascular cause
  4. If expiratory scanning was not available, look at clinical features.  Dyspnea, cough, wheezing and response to bronchodilators are common in patients with small-airway disease and infrequent in vascular lung disease
Our case: We did not perform expiratory scan in this patient but given clinical scenario, the dark areas likely represent mosaic pattern from known chronic pulmonary embolism with pulmonary hypertension. 

Stern EJ, et al. CT mosaic pattern of lung attenuation: distinguishing different causes. AJR 1995;165:813.

August 10, 2013

Pseudothickening of Colonic Wall

Axial and coronal-reformatted CT images of a 58-year-old woman show apparent circumferential wall thickening of the sigmoid colon (arrows) with a smooth transition into the more proximal colon. No pericolonic fat stranding is seen. Colonoscopy was performed but showed no colonic pathology.  Subsequent follow-up CT was also normal.  


  • When distended, normal colonic wall should be less than 3 mm or even imperceptible
  • Fecal contents, fluid or colonic redundancy make true wall measurement difficult or impossible
Pseudothickening of Colonic Wall
  • Could be mistaken for true pathology such as annular neoplasm or inflammatory stenosis
  • Pseudothickening should be mild. Its margin should gradually return to full distention
  • Normal pericolonic fat

Mang T et al. Pitfalls in multi-detector row CT colonography: a systematic approach.. Radiographics 2007;27:431.
Macari M, Balthazar EJ. CT of bowel wall thickening significance and pitfalls of interpretation. AJR 2001;176:1105.