Deep vein thrombosis in the lower extremity occurs in the intramuscular veins approximately 40% of the time. Is your facility missing them? Modern venous ultrasound has been around for over 20 years. I use the term modern as in the early 90’s the quality of ultrasound advanced by leaps and bounds. At this time imaging of the lower extremity for deep vein thrombosis was done primarily from the groin or inguinal ligament to just below the knee. Vascular ultrasound was just starting to take its on its own dedicated specialty and thus further evaluation of the calf ensued. Nearly 20 years later there is still no consensus on the proper or best way to image the lower extremity.
The American College of Radiology does not require calf vein imaging but suggests it. In the ACR-AIUM-SRU Practice Guideline For The Performance Of Venous Ultrasound Examination the wording is as follows: Abnormal findings generally require additional images to document the complete extent of the abnormalities.
b. i Symptomatic areas such as the calf generally require additional evaluation and additional images
if the cause of the symptoms is not readily elucidated by the standard examination.
ii. The extent and location of sites where the veins fail to compress completely should be clearly
recorded and generally require additional images. Long axis views without compression may be
helpful to characterize the abnormal vein.
c. The patient presentation, clinical indication, or clinical management pathways may require protocol
adjustments such as more detailed evaluation of the superficial venous system, evaluation of the deep
calf veins, or a bilateral study [11-13].
d. Other vascular and nonvascular abnormalities, if found, should be recorded, but may require
additional imaging for diagnosis or further characterization. Anatomical variations such as
duplications should be noted.
The Intersocietal Accreditation Commission (IAC) Standards and Guidelines for Vascular Testing Accreditation on the other hand requires imaging of the posterior tibial and peroneal veins at minimum but adds that additional images of the areas of suspected thrombus and additional images per facilities protocol should be taken. It further adds this comment: Additional sites may be required by the facility protocol or when indicated – common iliac, external iliac, great saphenous, small saphenous, proximal deep femoral, gastrocnemius, soleal, anterior tibial or perforating veins or inferior vena cava.
An article in the Journal of Vascular Surgery 1999, Division of Vascular Surgery the following finding:
Patterns and distribution of isolated calf deep vein thrombosis.
a. J Vasc Surg 1999, Division of vascular surgery, Loyola University Medical Center.
b. 5250 patients (scanned all of the calf veins)
c. Peroneal veins were the most involved (41%), soleal second (39%), Posterior tibial (37%), gastrocnemius (29%).
d. Isolated thrombus was found in the soleal (20%), gastrocnemius (17%) , peroneal (15%) and posterior tibial (12%).
e. Thrombus confined to a single or paired vein (64%), involving two different named veins (27%), and thrombus in three veins (7%) or four veins (1.4%) was less prevalent. Multifocal thrombus (veins that don’t connect) was present in (22%) of the time.
The study conclusion: 40% of the patient with acute isolated calf DVT would be judged to have normal CFDS examination results if muscular veins of the calf were not imaged (soleal and gastrocnemius).
At vascularcme.com we have analyzed over 13,000 exams in the past 9 years and have found even higher percentages of calf vein involvement in our lab.
Missing 40% of anything while performing diagnostic ultrasound in my humble opinion should garner great discussion in the radiology or vascular community.
Is your facility missing 40% of the deep vein thrombus that walks in and out of the facility? If so, it may be time to change your facility protocols and provide your staff additional hands-on education.