April 21, 2014

Metatarsal Stress Fracture

Oblique radiographic view of the foot shows transverse fracture lines of the proximal diaphyses of the forth and fifth metatarsals (arrows). Note sclerotic bone ends, periosteal reaction and minimal widening of the fracture gaps (degree of sclerosis is more on the forth digit)
Facts

  • Spontaneous fractures of normal bone that result from summation of stresses
  • Most common lower-extremity stress fracture
  • Originally termed "march fracture" (seen in military recruits). Now seen in ballet, football, gymnastics and basketball
  • Most common site = shaft (at diaphysis or neck)
  • Increased incidence in pes cavus and pes planus foot


Radiography

  • Often negative in early phase. May see thickening of cortex and small periosteal reaction
  • Later, a fracture line with sclerotic bone ends, periosteal reaction, widening of fracture gap will be shown. 
  • Late phase, the bone ends involved are entirely sclerotic 

References:
Schepsis AA, Busconi BD. Sports Medicine, 2006.
Baxter DE, Porter DA, Schon L. Baxter's the Foot and Ankle in Sport, 2008. 

April 11, 2014

Colonic Lymphoma

Axial (top) and coronal-reformatted (bottom) CT images show partial circumferential wall thickening (arrows) of the descending colon (C). Note smooth margin and homogeneous enhancement of bowel wall thickening, and disproportionate lack of colonic narrowing despite a large lesion. 
Facts:
  • Lymphoma accounts for 0.2% - 1.2% of all colon malignancies
  • Most common form of GI tract lymphoma is non-Hodgkin lymphoma (NHL)
  • Most common sites of GI tract lymphoma is stomach, followed by small bowel
  • For colonic lymphoma, most common site is cecum
  • Nonspecific clinical signs and symptoms
  • Due to rarity, Rx is not standardized. Often, it is surgically resected then chemotherapy is given
CT patterns of GI tract lymphoma:
  • Nodular thickening of bowel wall
  • Discrete polyp (causing intussusception)
  • Long, distensible infiltrative lesion with ill-defined, thick walls with aneurysmal dilatation of the lumen
  • Large exoenteric mass extending into adjacent soft tissues
Features differentiating lymphoma from adenocarcinoma of GI tract
  • Bulky lymphadenopathy (lymphoma more likely)
  • Marked luminal dilatation of bowel segment that is involved (lymphoma more likely)

Our case: Colonic mucosa-associated lymphoid tissue (MALT) lymphoma in a 67-year-old man.

References:
Buckley JA, Fishman EK. CT evaluation of small bowel neoplasms: spectrum of disease. Radiographics 1998;18:379.
Bairey O, et al. Non-Hodgkin lymphomas of the colon. Hematol 2006;8:832.

April 1, 2014

Sellar Mass with Calcification

Sagittal images (upper left = CT, upper right = T2W MR, lower left = T1W MR, lower right = T1W post-contrast MR) of the pituitary region of an elderly individual show a large sellar/suprasellar mass with internal calcification (hyperdense on CT, signal loss on MR). The mass is mostly solid and reveals heterogeneous enhancement. Note ballooning of the sella.
Differential diagnosis of a calcified sellar mass:

  • Craniopharyngioma (most likely)
  • Pituitary adenoma (unlikely, 0.2% - 8% have calcification)
  • Rathke's cleft cyst (rare disease)
  • Chordoma (rare disease)
Associated findings that help DDx:
  • Nodular appearance of calcification --> craniopharyngioma
  • Calcifications in a cystic mass --> craniopharyngioma
  • Curvilinear appearance of calcification --> pituitary adenoma or Rathke's cleft cyst
  • Bone destruction --> chordoma
This is a rare case of sellar/suprasellar chondrosarcoma confirmed with histology. 


Reference:
Kasliwal MK, Sharma BS. A rare case of pituitary adenoma with calcification: a case report. Turkish Neurosurg 2008;18:232-235
Glezer A, et al. Rare sellar lesions. Endocrinol Metab Clin N Am 2008;37:195-211. 

March 21, 2014

Uterine Leiomyoma on MRI

Leiomyoma in a 28-year-old woman. Sagittal MR images in T2W (A), T1W (B) and post-contrast T1W (C) show a large, rounded, circumscribed mass in the anterior wall of the uterus (U) that pushes the bladder (B) anteriorly. The mass demonstrates T2 hypointensity, T1 isointensity and heterogeneous enhancement. 

Facts
  • Most common uterine neoplasms with prevalence up to 40% of women of reproductive age
  • Benign tumors of smooth muscle with variable amount of fibrous tissue
  • Surrounded by pseudocapsule and supplied by one or two large vessels
  • Greater than 90% from uterine body
  • Classified on their position relative to uterine wall (submucosal, intramural or subserosal)

MR Imaging Findings
  • Well-circumscribed mass
  • Classic signal intensity: T1 isointensity, T2 hypointensity, variable enhancement
  • If T1 hyperintense, think hemorrhage
  • If T2 hyperintense, think cellular leiomyoma
  • If no enhancement, think partially or completely infarcted leiomyoma

References

Hricak H. MRI of the pelvis: a text atlas
Hamm B, et al. MRI and CT of the female pelvis. 

March 11, 2014

Tibial Spine Fracture in Adults

A lateral knee radiograph of a 22-year-old man sustaining motor vehicle collision demonstrates an oval bone fragment (arrow) in the intercondylar region of the knee. There is complete separation between the fragment and the donor site with superior displacement of the fragment. Note hemarthrosis (asterisk).

Facts:

  • Classically described in pediatric patients and considered the childhood equivalent of anterior cruciate ligament (ACL) ruptures in adults
  • Forceful hyperextension of the knee resulting in avulsive force/tension on ACL, which inserts into the anterior tibial spine. Possibly with valgus stress or rotation. 
  • In adults, most injuries occur in road-traffic accidents and are isolated
  • Adults more likely to have associated tear of medial collateral ligament (MCL) or intra-articular fracture
Classification (Meyers and McKeever)
  • Based on degree of displacement. Type II & III are most common
  • Type I = incomplete avulsion of tibial spine without displacement
  • Type II = incomplete avulsion with anterior elevation of the fragment
  • Type IIIA = complete separation of fragment
  • Type IIIB = rotated and comminuted fragment
  • Generally, types I and II are managed conservatively while type III fractures are managed arthroscopically or with open reduction

References:
Kendall NS, et al. Fracture of the tibial spine in adults and children. J Bone J Surg [Br] 1992;74-B:848-52.
Rosen's Emergency Medicine - Concepts and Clinical Practice

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