Pectus Excavatum

An axial CT image shows a measurement of Haller index (A = transverse diameter, B = anteroposterior diameter of the inner chest wall), which is approximately 3.4 indicating severe pectus excavatum.

Facts: Pectus Excavatum

• Congenital chest wall deformity "caved-in" or concave appearance in the anterior chest wall
• Most common type of congenital chest wall deformity (90% of all), followed by pectus carinatum (approximately 5%)
• Most cases are diagnosed within the first year of life
• Worsening during rapid bone growth (early teenage)

Diagnosis

• Easy to make on a clinical ground
• Radiography and chest CT performed to determine the need of surgery, and for surgical planning
• Haller index is used to grade the severity (Haller index = transverse chest diameter divided by anteroposterior diameter)
• Haller index > 3.2 correlates with severe deformity that requires surgery
• Two morphologic classifications of pectus excavatum: 1) symmetric (center of the sternum is the same as the center of depression 2) asymmetric (center of the depression is off to one side i.e. not at the same location as the center of the sternum). Chest CT is best used to show the morphology and for surgical planning

References:

1. Park HJ, Lee SY, Lee CS, et al. The Nuss procedure for pectus excavatum: evolution of techniques and early results on 322 patients. Ann Thorac Surg 2004;77:289-295.

2. Hebra A. Pectus excavatum. In: E-medicine, updated Sep 21, 2009.

Retroperitoneal Lymphadenopathy

Axial and coronal reformatted CT images show bulky retroperitoneal lymph nodes (arrows) and mesenteric lymph nodes (arrowheads). The lymph nodes are homogeneously enhanced and appear to surround the vessels.

Facts: Retroperitoneal Lymphadenopathy

• Diagnosed on CT or MRI by nodal enlargement that may be accompanied by displacement of adjacent structures
• Upper limit of normal at this location = 10 mm
• 8-10 "multiple" lymph nodes should be viewed with suspicion
• Large differential possibilities, including infection/inflammation and neoplasm.
• Generally, benign conditions do not exhibit massive conglomeration of lymph nodes

Differential Diagnosis:

• Infection: TB, MAI
• Inflammation: sarcoidosis, Castleman disease, bulky form of retroperitoneal fibrosis
• Neoplasm: lymphoma, metastasis
• Imaging features can significantly overlapped and it can be difficult to tell one way of the other. Biopsy is usually required for definitive diagnosis.

Potential Clues:

• Immunocompromised patients -- think of mycobacterial infection, lymphoma, Kaposi's sarcoma (esp. if there is cutaneous tumor), progressive generalized lymphadenopathy syndrome (lymphadenopathy in other locations)
• Multiple lymph node stations, homogeneous nodes, hepatosplenomegaly -- think of lymphoma
• Hyperenhancing -- think of hypervascular metastasis or Castleman disease

Our case: Retroperitoneal lymphadenopathy due to squamous cell carcinoma metastasis from head and neck cancer.

References:

1. Warshauer DM, Lee JKT, Patel H. Retroperitoneum. In: Lee JKT et al (eds), computed body tomography with MRI correlation, 4th edition, 2006.

2. Chapman S, Nakielny R. Aids to radiological differential diagnosis, 4th ed, 2003.

Posterior Reversible Encephalopathy Syndrome (PRES)

Fig. 1: Axial non-contrast CT image in a 57-year-old hypertensive man shows ill-defined areas of low attenuation in the posterior occipital lobe (arrows).
Fig. 2: Axial FLAIR MR image confirms the abnormality in cortical and subcortical white matter of the posterior aspect of the occipital lobes (arrows), relative sparing of the paramedian occipital regions. There is no contrast enhancement or restricted diffusion.

Facts: Posterior Reversible Encephalopathy Syndrome (PRES)

• Usually reversible neurologic syndrome presenting with reversible headache, altered consciousness or vision loss accompanied by reversible imaging abnormalities
• Related to hypertension, eclampsia and preeclampsia and immunosuppressive medication (and several other causes have been described)
• Believed to be due to hyperperfusion state with blood brain barrier breakthrough

Typical Imaging Appearances

• CT is often abnormal at the time of presentation. MRI shows more lesions and extent.
• Cortical or subcortical edema
• Preferential involvement of posterior aspect of the lobes, particularly parieto-occipital lobes (gradient effect present)
• Sparing of calcarine and paramedian occipital lobe structures
• Usually bilateral

Our case: PRES (typical imaging appearance)

References:

1. Hinghey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. New Eng J Med 1996;334:494-500.

2. McKinney AM, Short J, Truwit CL, et al. Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings. AJR 2007;189:904-912.

RiTradiology Celebrating 22,222 visitors

"Shadow of Dharma" by Thanwa Sudsang, MD

We are celebrating our 22,222 visitors on September 28, 2009. Thanks for visiting the site and please feel free to comment, request, submit a case for posting or a photo for the illumination.

Achilles Tendon Rupture

Lateral view of the ankle shows an avulsed bone fragment (arrow) from the donor site (arrowhead) at the attachment of the Achilles tendon.

Facts

• Achilles tendon is the thickest and strongest tendon in the human body
• It is also the most commonly ruptured tendon
• Most frequent mechanism is a sudden, forceful contraction of gastrocnemius
• Most common at zone of avascularity 2-6 cm above the calcaneal insertion

Clinical

• 30-50 years old, recreational athletes (usually playing basketball, racket sports, soccer or softball)
• Sudden pain after a pushing-off movement, audible pop, immediate weakness, palpable defect. Positive Thompson test
• Clinical confounders: tear of other tendons (plantaris, flexor, peroneal), soft tissue edema limiting physical exam by palpation
• In young, active patients, full-thickness tear is frequently treated by surgery. Nonsurgical options are considered in partial-thickness tear, sedentary, and high surgicalrisk patients

Role of Imaging

• To assess if there is an avulsed bone fragment (radiography)
• To differentiate between partial and full thickness tear (ultrasound, MRI)
• Findings of full-thickness tear (both US and MRI): non visualization of tendon, tendon retraction, fat herniation into the tendon gap.
• Additional findings seen on US of full-thickness tear: posterior acoustic shadowing due to refraction of sound beam at the frayed tendon, visualization of plantaris tendon

Our case: ruptured Achilles tendon associated with calcific tendinopathy

References:

1. Hartgerink P, et al. Full- versus partial-thickness Achilles tendon tears: sonographic accuracy and characterization in 26 cases with surgical correlation. Radiology 2001; 200:406-412.

2. Skinner HB. Current diagnosis and treatment in orthopedics. McGraw-Hill Professional, 4th edition, 2006.