Monday, June 22, 2015

Lymphangiogram

A lymphangiogram is an uncommon procedure that can be performed by interventional radiologists, typically to identify and potentially treat the source of a chylous leak.

Pre Procedure

  • Indications: Thoracic duct injury, usually from surgery, causing chylous effusion / chylothorax, or recurrent chylous ascites
  • Surgical management (direct fix of the leak intraoperatively if visualized) and medical management should be optimized first. 
  • Specifically, the patient should be on a low fat / medium chain triglyceride diet. Long chain triglycerides are absorbed by the lymphatics, which leads to extra lymph production. Medium chain triglycerides however are absorbed by the portal veins, reducing the production of lymph.  

Procedure

  • Transpedal approach: prep the feet
  • Inject 50/50 mix of isosulfan blue and lidocaine into the webbing between toes and wait 10-15 minutes for dye to be picked up by lymphatics
  • Make incision parallel to lymphatic
  • Strip away fat/tissue parallel to lymphatic
  • Insert backing (cardboard/plastic) underneath lymphatic
  • Insert 30 gauge needle into lymphatic and inject 100% lidocaine
    • Bubble test: watch to see if air goes into lymphatics, or if it fizzes
  • Take serial x-rays of lower extremities and abdomen to see lymphatics and eventually cysterna chyli fill
  • Once filled, can insert 21 gauge needle directly into cisterna chyli and perform embolization, usually with coils and/or N-butyl cyanoacrylate glue

Post Procedure

  • Evaluate for recurrent leak

Monday, June 15, 2015

A Simplified Approach To Spinal Masses

Spinal cord masses can be confusing at times, especially if not encountered routinely. While it may be difficult to arrive at a specific diagnosis, a narrowed differential can often be very helpful to the referring clinician. Clinical history is also quite useful at narrowing the differential.

The first question to ask is where exactly is the tumor located within the spinal canal. The broad categories are: intramedullary, intradural-extramedullary, and extradural. An intramedullary mass will be centered within the substance of the spinal cord itself, which has been described as the claw sign. An intradural-extramedullary mass will form a meniscus with the cord and push it away. An extradural mass will be outside the thecal sac. Vertebral body or clear epidural involvement suggests an extradural location. In cases where the distinction is difficult, assess the cord above and below the mass.

Once that determination has been made, the chart below can help generate a differential by focusing on both the imaging characteristics and clinical context:


The chart is not comprehensive, but it does list the most common primary masses to be found within those locations within the spine. As always, metastases are a consideration in any of these locations. Making the distinction can be challenging at times, especially when the mass is large and distorts normal structures.


References:

Monday, June 8, 2015

Leptomeningeal FLAIR Hyperintensity Differential Diagnosis

Hyper intensity in the subarachnoid space can have a wide range of causes. The finding may be subtle to detect at times. However, identifying it can be crucial in altering a patient's management. The mnemonic FLAIR can be used to recall the common causes of this finding:

DiseaseNotes
FFiO2 highNo contrast enhancement
LLeptomeningeal spread of tumorGEMCLOG: glioblastoma, ependymoma, medulloblastoma, choroid plexus tumor, lymphoma, oligodendroglioma, germinoma
AAneurysmal bleedNo contrast enhancement
IInfection (meningitis)
RpRopofolNo contrast enhancement, may also be due to increased oxygen



Monday, June 1, 2015

Dilated Small Bowel Differential Diagnosis

A common finding in patients with abdominal pain is dilated loops of small bowel. Dilated loops may be noted on plain X-ray, fluoroscopic studies, or CT. The first step to forming a focused differential diagnosis is determining whether the folds are thin, thick (> 3 mm), or thick and nodular.

If the folds are thin, the mnemonic MISS can be used to recall the common diagnoses:

DiseaseNotes
MMechanical obstructionDue to intraluminal impaction (high fiber foods), adhesions post-operatively, or a mass
IIleusPost-operatively, medications
SScleroderma
Systemic sclerosis due to deposition of collagen
Sacculations of anti-mesenteric border
Hidebound bowel (unchanging on dynamic studies)
SSprueVillous atrophy and crypt hypertrophy → chronic fluid overload → ‘congestive gut overload’ → featureless mucosal pattern proximally in small bowel = reversal of jejunal / ileal fold pattern

Moulage sign: moulage means casted or molded structure; the jejunum appears a cast of itself due to featureless appearance because of lack of mucosal folds

Small Bowel Obstruction
Source: Radiology Assistant

If there is segmental thickening of the folds, think of the three Is: ischemia, infection, or idiopathic. Diffuse fold thickening is usually due to systemic processes such as venous congestion or cirrhosis.

Nodular fold thickening is usually due to infiltrative processes of the bowel wall. Common etiologies include Crohn disease, infection, lymphoma, metastases, and Whipple disease.

If the dilatation is thick walled, check out the differential diagnosis for small bowel aneurysmal dilatation.

If you want to learn more about GI imaging, specifically fluoroscopy, the Mayo Clinic Gastrointestinal Imaging book is a wonderful reference with over 500 images:



Monday, May 25, 2015

Will Watson Compete For Radiology Jobs?

IBM recently release an ad from the Ogilvy Group agency currently airing on national TV that directly addresses how Watson, IBM's ongoing supercomputing research project popularized by its star turn on the TV show 'Jeopardy!, may one day play a role in diagnostic imaging:


Is this realistic, or just some far off pipe dream? Technological aspirations often tend to outstrip technical reality. For example, computer-aided diagnosis (CAD) in mammography has not become a panacea for screening mammograms, and ultimately does not appear to have had a significant impact on the labor demand for mammographers. Anecdotally, mammographers I have spoken with regard CAD as too sensitive, and a potential liability. Sure, the software will pick up the subtle lesion occasionally, but it will pick up many more that are merely normal tissue, but nonetheless force the radiologist to make an active decision to dismiss. What happens if the mammographer decides a positive finding on CAD is negative, but cancer develops later anyway? Unless the software can improve both sensitivity *and* specificity, it may create as many problems as it solves.

For argument's sake though, let's say the new technology can improve both sensitivity and specificity.  Several open questions come to mind: will the software aid radiologists? Does it seek to replace radiologists? If it does, who takes on liability if the software 'misses' a lesion, as it inevitably will? And who pays for it all? It is hard to see these questions being answered in the affirmative in the current healthcare system, but after seeing ACA pass, it is clear that the environment is not static. If costs start to rise again, and IBM and similar software vendors market themselves well, one could see hospitals giving such systems a try. The tl;dr - money talks and BS walks: if these systems can do the job better than radiologists, they will be used.

How can radiologists operate under such potential uncertainty? Instead of ducking the issue, radiologists should work towards simultaneously figuring out how best to employ these systems while also demonstrating the value-add of a physician diagnostic imager both to referring clinicians and to patients. If the face of the radiologist is merely the report they generate, very soon that face may take a very Big Blue complexion.