Can an Ultrasound Tech Know if You Have Blood Clots
Venous ultrasound is the standard imaging examination for patients suspected of having lower extremity deep venous thrombosis (DVT). Notwithstanding, there is disagreement among administrative groups regarding the necessary components of the venous ultrasound. Protocols issued by the American College of Chest Physicians,1 American Institute of Ultrasound in Medicine/American College of Radiology/Society of Radiologists in Ultrasound,2 Society for Vascular Ultrasound,three and Intersocietal Accreditation Committee Vascular Engineeringfour vary. The lack of a single protocol has led to misunderstandings between ordering clinicians and facilities providing the service. This may outcome in underdiagnosis, unnecessary testing, and insufficient imaging. The variability is exacerbated by disruptive terminology in reports. There is an all-encompassing body of published data addressing the components of the venous ultrasound examination. The Society of Radiologists in Ultrasound assembled an interdisciplinary panel of experts in venous diagnosis to review the gimmicky literature and develop consensus recommendations to create a standardized approach to the ultrasound diagnosis of lower extremity venous thrombosis.
Methods and Conference Training
The Social club of Radiologists in Ultrasound sponsored a multidisciplinary consensus briefing (Oct xviii–19, 2016). The console was charged with critically evaluating venous ultrasound protocols for the evaluation of suspected DVT, evaluating the terminology used to communicate results to clinicians, and developing consensus recommendations for the protocol and its terminology.
Experts in venous imaging and the treatment of DVT were invited to join the panel. Participants included experts in emergency medicine, hematology, radiology, ultrasonography, vascular medicine, and vascular surgery. Interested organizations were also notified of the consensus conference, and a subset sent representatives to the meeting to add commentary and perspectives as nonvoting participants. Before the meeting, organizers and participants assembled a bibliography of relevant primary source scientific publications, scholarly literature reviews, and published guidelines from professional societies.one–sixteen These were reviewed before the meeting.
Each of the recommendations was reached by open give-and-take and represents the unanimous agreement of the participants. These recommendations are endorsed by the Society of Radiologists in Ultrasound.
Consensus Conference Recommendations
The recommendations of the consensus conference can be summarized into 5 key areas: (ane) patient option, (two) ultrasound protocols, (3) serial and follow-up considerations, (4) terminology for ultrasound reports, and (v) diagnostic criteria.
Patient Selection
Consequence
Multiple guidelines recommend clinical prediction rules to estimate pretest probability of DVT earlier ultrasound ordering.17–20 There are several tools, but the most commonly used clinical determination rule for chance stratification is the Wells score (Table ane).19
| Clinical Characteristic | Score |
|---|---|
| Active cancer (patient receiving treatment for cancer within the previous 6 months or currently receiving palliative treatment) | 1 |
| Paralysis, paresis, or contempo plaster immobilization of the lower extremities | 1 |
| Recently bedridden for ≥three days, or major surgery inside the previous 12 weeks requiring general or regional anesthesia | 1 |
| Localized tenderness along the distribution of the deep venous system | 1 |
| Entire leg swollen | 1 |
| Calf swelling at least three cm larger than the asymptomatic side (measured x cm below the tibial tuberosity) | 1 |
| Pitting edema confined to the symptomatic leg | ane |
| Collateral superficial veins (nonvaricose) | 1 |
| Previously documented deep venous thrombosis | 1 |
| Alternative diagnosis at least as likely equally deep venous thrombosis | –2 |
After an unlikely pretest probability of DVT based on a clinical determination dominion assessment, a negative D-dimer test is adequate to safely exclude DVT. Venous ultrasound is non appropriate for those individuals. Ultrasound is appropriate for patients with a probable pretest probability of DVT, an unlikely pretest probability of DVT with a positive D-dimer, and those in whom pretest probability was not assessed.17,xviii
Recommendation
All patients should be evaluated for pretest probability of DVT. For those with depression (unlikely) pretest probability, obtaining a loftier-sensitivity D-dimer is appropriate.
Ultrasound Protocols
Standardization
Result
The protocols in apply for venous ultrasound vary by promulgating organization and facilities in the aforementioned community. This variability leads to confusion and errors including inappropriate patient selection and improper follow-up.
We propose that a single consummate study is the safest strategy. A limited examination to the knee requires a second examination to safely exclude undiagnosed calf DVT that may propagate proximally between the studies (Figure one).
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Figure ane. Normal femoral vein at baseline and acute DVT at 1-week follow-up. A and B, Ultrasound images of a normal femoral vein without (A) and with (B) compression. The artery (Art) is inductive to the vein. Subsequently compression, the vein is completely collapsed, indicating normal compressibility. C and D, Ultrasound images of astute femoral vein thrombus without (C) and with (D) pinch later on 1 week of follow-up. The patient was followed for acute calf DVT that was not treated (not shown). The acute DVT (* in C) is heterogeneous. Information technology expands the vein. Afterwards compression (D), the vein does not collapse but has an oval shape indicating an astute DVT based on the noncompressible but deformable vein. DVT indicates deep venous thrombosis.
Recommendation
Complete duplex ultrasound (CDUS) is the preferred venous ultrasound examination for the diagnosis of astute DVT. CDUS is compression of the deep veins from the inguinal ligament to the ankle (including posterior tibial and peroneal veins in the calf), right and left mutual femoral vein spectral Doppler waveforms (to evaluate symmetry), popliteal spectral Doppler, and color Doppler images (Figure 2). Compression is performed at 2-cm intervals.iii,21
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Effigy ii. Lower extremity venous organization and extent of ultrasound tests. Black rectangles represent the extent of the compression ultrasound. Greyness rectangles are sites of duplex Doppler. 2-CUS (2-region compression ultrasound) indicates compression ultrasound including the femoral veins 1 to two cm above and beneath the saphenofemoral junction and the popliteal veins upwards to the dogie veins confluence; ECUS (extended pinch ultrasound), the compression ultrasound from common femoral vein through the popliteal vein up to the calf veins confluence; CCUS (complete compression ultrasound), compression ultrasound from common femoral vein to the ankle; and CDUS (complete duplex ultrasound), compression ultrasound from the common femoral vein to the talocrural joint (evaluating the posterior tibial and peroneal veins in the dogie), color and spectral Doppler of the common femoral (or iliac veins) on both sides, color and spectral Doppler of the popliteal vein on the symptomatic side. Ultrasound of symptomatic areas may be required if the symptoms are not explained past the standard thigh-to-talocrural joint test.
Symptomatic areas should exist evaluated to determine if there is superficial venous thrombosis or other pathology, in particular if the assessment of the deep veins is normal.
Limited protocols (not including calf veins) and selective evaluation of the calf are not recommended because limited protocols require a second study in 5 to 7 days to safely exclude DVT (Tabular array 2).
| Clinical Characteristic | Recommendation |
|---|---|
| Negative consummate duplex ultrasound | |
| Persistent or worsening symptoms | Repeat scan in 5 days to one week, earlier if concern is loftier. |
| High risk | Consider repeat browse if etiology for symptoms not otherwise elucidated. |
| Technically compromised study | Recommend repeat browse in five days to 1 week if more than than minor limitation. D-dimer may be helpful if information technology is negative. |
| Concern for iliocaval DVT | Pelvic venous imaging, especially CT or MR venography, or iliocaval duplex ultrasound. |
| Negative extended compression or 2-region ultrasound | |
| Risk of DVT persists or etiology of symptoms not elucidated | Repeat scan, preferably complete duplex ultrasound, in five days to one week. |
Patients with calf DVT who the clinician decides to manage expectantly should have a repeat scan at one week or sooner if risk factors or symptoms warrant. Repeat scans are ended later 2 weeks or if handling is begun (Tabular array 3).
| Clinical Feature | Recommendation |
|---|---|
| Positive complete duplex ultrasound | |
| Astute dogie DVT, non treated | Repeat scan in one calendar week, earlier if symptoms progress. If progression to femoropopliteal DVT, treat. If normal, stop. If persistent calf thrombus which is not treated, echo scan at 2 weeks. Scanning afterward two weeks is generally non warranted. |
| Acute DVT, on treatment | Echo not warranted unless a change in the browse will change patient management.Follow-up at the stop of treatment to establish new baseline. |
| Indeterminate results | D-dimer may be helpful if negative. Recommend echo scan in v days to 1 week to evaluate for change. |
| Concern for recurrent DVT, equivocal findings for scar versus recurrence at site of scar | D-dimer may exist helpful if negative. Recommend repeat scan in 1–3 days and 7–x days. |
| Concern for iliocaval DVT, peculiarly if abnormal spectral Doppler findings | Pelvic venous imaging, especially CT or MR venography, or iliocaval duplex ultrasound. |
| Positive extended compression or 2-region ultrasound | |
| Astute DVT | Repeat browse, preferably complete duplex ultrasound in v days to i week to document entire extent of lower extremity veins. |
Availability of Duplex Ultrasound and Point-of-Care Ultrasound
Result
Duplex ultrasound equipment and staff are non available in all sites at all times.
Recommendation
A point-of-care ultrasound consisting of a limited evaluation with compression from thigh to knee (extended pinch ultrasound [ECUS]) (Figure 2) is appropriate when CDUS is not available in a timely manner. ECUS is favored over 2-region compression because isolated femoral vein DVTs may be missed. Afterward a negative ECUS, CDUS in 5 to vii days is required to safely exclude DVT.
If ultrasound is not available, anticoagulation earlier a confirmatory ultrasound is a condom strategy.22,23
Iliocaval DVT
Issue
Iliocaval DVT may be undetected because the thrombus is cephalad to the standard examination. Whole-leg swelling with a normal compression ultrasound or the finding of continuous or asymmetrical mutual femoral Doppler spectra suggests a more primal obstructive procedure.
Recommendation
If iliocaval disease is suspected because of signs and symptoms or abnormal spectral Doppler waveforms, the threshold for pelvic ultrasound, computed tomography, or magnetic resonance venography should exist depression.
Serial and Follow-Upward Considerations
Patients at High Gamble, Those With Persistent Symptoms or Express Studies
Issue
Occasional patients will accept DVT despite a normal CDUS test because of technical limitations, equivocal findings, or the lower sensitivity of the calf exam in comparing with examination of the femoropopliteal veins (Tables ii and 3).
Recommendation
Echo ultrasound may exist required for patients who have a negative CDUS with persistent or worsening signs and symptoms, a technically inadequate CDUS, or an equivocal finding. Follow-up is usually 5 to 7 days but can be shorter if concern is loftier or clinical symptoms warrant.
Patients with normal examinations to the articulatio genus or 2-region ultrasound require a serial ultrasound in 5 to 7 days.
Recurrent DVT
Effect
The diagnosis of recurrent DVT is difficult in the absence of an unequivocally new site of acute DVT (Figure three). Persistent scarring may reduce the power to distinguish chronic scarring from a new DVT.
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Effigy 3. Acute DVT, chronic postthrombotic change, and recurrent DVT. Long-axis sonograms of the left popliteal vein. A, Acute DVT. The vein contains heterogeneous acute DVT (*). B, Chronic postthrombotic change. The patient returned the following twelvemonth for swelling. The intraluminal material is smaller and flat (between arrows). The lumen is partially reconstituted because of retraction (*). C, Recurrent DVT. The patient returned the following year with swelling. A long-axis color Doppler image shows an intraluminal filling defect with no flow in the vein (*). The new astute DVT distends the vein (betwixt arrows). The changes in size and absenteeism of period are new findings typical of acute DVT that has recurred at the site of prior scarring. DVT indicates deep venous thrombosis.
Recommendation
Equivocal ultrasound findings may require serial imaging after 1 to 3 and vii to x days to make up one's mind if there are any astute changes that would betoken recurrent DVT. D-dimer may likewise exist helpful to establish if recurrent DVT is nowadays.
Follow-Up of Patients on Anticoagulation
Issues
Repeat studies while the patient is on anticoagulation are non standardized. There is no standard for ordering an ultrasound at the end of anticoagulation.
Recommendation
Imaging while on acceptable anticoagulation is unwarranted unless it will change the patient's handling.
Echo ultrasound at or near the end of anticoagulation is recommended to establish a new baseline and to make up one's mind if scarring is present.
Terminology for Ultrasound Reports
Scarring
Issue
Normal veins and astute DVT are well understood, but other descriptive terms for ultrasound observations after diagnosis are subject to misinterpretation.
After DVT, the vein may heal completely or scar. Thrombus becomes infiltrated with fibroblasts, organizes, and reendothelializes over several weeks to months. Fibrosis producing scarring, wall thickening, and synechiae causing partial obstruction may persist for years.24,25 The residual material is no longer thrombus.26
The terms chronic thrombus or residuum thrombus for the residual cloth may be misinterpreted past providers and atomic number 82 to inappropriate anticoagulation for presumed persistent or acute thrombus.
Recommendation
Chronic postthrombotic change is the preferred term for the cloth that persists on ultrasound later acute DVT (Figure 3).
Subacute Thrombus
Effect
The ultrasound appearance of thrombus may evolve or resolve later on its formation over the first 6 months24,27 (Figure iv). Subacute thrombus is a disruptive term; information technology erroneously implies at that place are well-defined ultrasound findings that are unique to the appearance of thrombus weeks to <6 months old.
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Figure 4. Acute DVT evolving to subacute thrombus. Long-centrality images of the femoral vein v weeks autonomously. A, Acute occlusive DVT. Color Doppler scan shows material distending the vein (*) beneath the avenue (Art). There is no menses at the thrombus. B, In the 5-calendar week interval, the material has changed configuration. The cephalad textile (*) still expands the vein, whereas the caudal fabric has retracted (pointer), indicating an appearance different from acute DVT and not typical of scarring. The historic period of the cloth would be difficult to evaluate without the baseline epitome such that the cephalad portion might be interpreted every bit recurrent DVT. DVT indicates deep venous thrombosis.
Recommendation
The term subacute thrombus does non have a unique ultrasound appearance and should rarely exist used. It should exist reported for a follow-up study only if (1) there is a previous ultrasound demonstrating astute thrombus weeks earlier and (two) the new report shows a change in the appearance of the thrombosis that is non typical of chronic postthrombotic change. It is wrong to use subacute thrombus to indicate recurrent DVT, chronic postthrombotic change, or equivocal findings.
Diagnostic Criteria
Gray-Scale Findings
Issue
Noncompressibility is common with both astute DVT and scarring. The criteria to distinguish the two vary in quality.
Recommendation
Abnormalities should be classified into acute venous thrombosis, chronic postthrombotic alter, or indeterminate (equivocal).
Astute venous thrombosis causes vein noncompressibility, merely the thrombus is soft and deformable with probe pressure. In general, the surface of the thrombus is smooth and the vein is larger than normal. A loosely adherent or free-floating edge may be seen but is less common.
Veins with chronic postthrombotic change are also noncompressible, merely the intraluminal fabric is rigid and nondeformable with probe pressure. The surface may be irregular, and calcifications may rarely be noted. The material may retract and produce thin webs (synechiae) or thicker flat bands. Incorporation into the vein wall or recanalization may produce regular or irregular wall thickening. In the setting of scarring, the vein size may be normal or decreased. Thrombus echogenicity is not a reliable sign of its historic period.28
The most astute-appearing material should be preferred in the classification of the thrombus. The panel recommends classifying findings as indeterminate when criteria conflict and cannot be reconciled, eg, where findings are nowadays but neither completely astute nor chronic.29
Recurrent DVT may be (1) acute thrombus in a previously normal vein in a patient with prior DVT or (2) acute thrombus on areas of scarring.
Discussion
In that location are several strategies to place patients with suspected venous thrombosis for whom anticoagulation therapy may exist safely withheld if the study or serial studies are negative. These include a unmarried complete compression ultrasound, 2 limited compression ultrasounds 5 to seven days apart, and combinations of pretest probability, D-dimer, and either limited or consummate compression ultrasound.6,17,30,31
Consummate Ultrasound Protocols
A unmarried complete compression ultrasound is a safe strategy. A meta-assay reported the three-month risk of venous thromboembolic disease after negative complete compression ultrasound to exist 0.57% (95% confidence interval, 0.25%–0.89%).eleven
There are advantages to a single well-defined complete duplex ultrasound test to the calf for patients suspected of their outset example of DVT. Patients will go the same examination whether it is performed in a vascular laboratory, radiology section, or other convalescent setting. The console agreed that establishing a diagnosis of dogie DVT is warranted even if anticoagulation is not instituted. Decisions regarding handling of isolated calf DVT and hazard stratification should be informed by equally complete a diagnostic assessment as possible.
The presence of calf DVT may give information relevant to the patient'south ultimate upshot such as risks for recurrent DVT, mortality, subsequent diagnosis of cancer, and chronic venous insufficiency.15,32 Even in the absence of calf symptoms at the time of the ultrasound, the status of calf veins may become relevant if the patient returns with new symptoms. Dogie evaluation may notice culling diagnoses such as musculoskeletal abnormalities.33
The primary statement confronting implementation of CDUS relates to the direction of isolated calf DVT and concerns of overtreatment.33 Simulated-positive diagnosis of calf DVT by ultrasound is rare; the specificity of compression ultrasound for calf DVT is 97.8% (97.0%–98.4%).34 We agree that scanning the calf veins does require that the referring healthcare provider understands the significance of this information or has access to specialty consultation for both the treatment and follow-upwardly of distal DVT. We recognize that management protocols may non be firmly established.one,35–38
If isolated calf DVT is diagnosed and managed expectantly, in that location are well-defined protocols for follow-upward.17 Patients with calf DVT that was observed without anticoagulation should have a repeat scan, at 1 week and once again at ii weeks if the calf DVT persists just does not extend.17 If there is proximal propagation or significant extension of the thrombosis, the patient should receive anticoagulation. No further imaging is warranted if the distal DVT resolves at one calendar week or does non extend significantly at two weeks. Serial ultrasound is non indicated if the patient receives anticoagulation unless a change in the clinical condition warrants consideration of a change in treatment.39
Because the determination to withhold anticoagulation in a patient with diagnosed isolated calf DVT mandates boosted scans, limited ultrasound protocols too crave repeat imaging to be a safe strategy. The addition of a D-dimer test afterwards a negative limited ultrasound does non modify the number of follow-up ultrasounds unless it is negative. Positive D-dimer tests are as common as isolated calf DVT and practise not provide discriminating information.vi
A negative CDUS does non completely exclude all DVT, in detail calf DVT. The sensitivity of compression ultrasound for dogie DVT is 56.8% (95% conviction interval, 49%–66.four%), less than that of duplex ultrasound for proximal DVT 96.5% (95% confidence interval, 95.1%–97.6%).34 Propagation of dogie DVT normally causes persistent or worsening symptoms. Appropriate patient follow-up and serial scans tin can address this complexity.
Muscular (gastrocnemius or soleus) vein DVT may present as pain. Scans of symptomatic regions are part of CDUS protocol and tin can diagnose these DVTs.
Scanning the dogie veins increases the complexity and the time required for the test. Facilities that follow the Intersocietal Accreditation Commission Vascular Testing guidelines, Society for Vascular Ultrasound guidelines, or American College of Radiology/American Institute of Ultrasound in Medicine/Society of Radiologists in Ultrasound guidelines currently evaluate dogie veins in some or all of their patients. Including calf veins will result in a learning curve for some laboratories, but the consummate ultrasound protocol is a mandatory component of the current sonographer curriculum and detailed in standard textbooks. Sonographic criteria in the calf are identical to those in proximal veins; therefore, acquiring a dogie vein ultrasound skill set requires learning only new anatomy and patient positioning.
Modern ultrasound equipment has sufficient resolution to evaluate both proximal and calf veins. All laboratories have linear transducers, and most take curved array transducers (in particular, if they perform abdominal imaging). Curved array transducers and harmonic imaging are helpful for technically challenging cases.
Some analyses take concluded that compression ultrasound is equivalent to duplex scanning for proximal DVT,forty but the panel favors duplex Doppler, including color and spectral Doppler in at least two sites in the leg. Color Doppler ultrasound can detect consummate versus incomplete obstacle. Color Doppler may assist identify smaller and pelvic veins, in particular if augmentation is used. It can be used to clarify otherwise technically difficult findings.
Spectral Doppler abnormalities tin can be used to identify obstruction in the vein segments primal to the sample site. Spectral Doppler cess of both common femoral or external iliac veins for phasicity and symmetry may yield important data (Effigy five). An abnormal spectrum, particularly a flat (continuous) waveform, has good specificity for iliocaval venous obstruction that may be the result of central thrombosis, scarring, or extrinsic compression from pelvic pathology.41,42
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Figure 5. Normal and aberrant common femoral vein waveforms. Long-axis spectral Doppler images of mutual femoral vein waveforms. A, The normal waveform which varies with respiration and during the cardiac cycle flowing toward the center (away from the transducer, beneath the baseline). There is a small-scale normal component of opposite flow (above the baseline). B, An aberrant waveform with flat uniform signal toward the heart. The color component shows the vein itself to be patent. This indicates obstruction to a higher place the level of the browse.
Limited Protocols and Limited or Consummate Ultrasound Protocols
Express ultrasound protocols will not detect DVT in the uninvestigated segments. Unevaluated segments include the calf and, depending on the protocol, portions of the femoral vein organization. Five percent of patients have thrombus limited to the dogie,17 although some studies suggest this may exist higher.13,43 A unmarried express compression ultrasound will not detect these. Ix pct9 to 21.4%17 of isolated dogie DVT volition propagate proximally and crave pharmacological treatment. Limited protocols address this deficiency past recommending a second ultrasound at a later time. Patient compliance with scheduled repeat ultrasound imaging is inconsistent,44 and omission of the follow-up ultrasound report may have astringent consequences. Proximal DVT is diagnosed at the second ultrasound in as many every bit 5.seven% (i.9%–12.8%) of patients.6,33
Limited scans that skip the dogie may also not provide the data required past the referring healthcare providers or patients, in particular in the setting of calf symptoms.33,45
Algorithms that include a choice of a complete or limited ultrasound are excessively complicated1,2,17 and tin can lead to medical error.45 The current American Higher of Radiology/American Institute of Ultrasound in Medicine/Society of Radiologists in Ultrasound guidelines include selective calf imaging for the subset of patients with calf symptoms not explained by the proximal scan. Determining the presenting symptoms then moves from the responsible clinician to the sonographer or imaging facility. This increases the chances of an omitted indicated calf evaluation or overutilization when not indicated. The American College of Chest Physicians protocol has different tests based on pretest probability, likelihood to return for follow-up, symptoms, and chance factors. This complex approach can lead to errors selecting the proper diagnostic algorithm or improper application of the pathway components (eg, ordering a D-dimer for a patient at high risk or non obtaining the necessary follow-upwards).44 In addition, for those patients in whom pretest probability was not assessed (not recommended, merely non an uncommon state of affairs), the American College of Breast Physicians guidelines recommend different protocols for whole leg, proximal leg ultrasound, or D-dimer, each with different workflows.17
Point-of-Care Ultrasound Protocols
Complete protocols require a duplex Doppler ultrasound machine and are generally performed by a sonographer or vascular technologist. There are circumstances (eg, emergency departments, rural areas, off hours) when a consummate study cannot be performed in a clinically relevant time frame. In this state of affairs, if point-of-intendance ultrasound can be performed by a competent practitioner, it should be performed.46,47
Extended compression ultrasound is a point-of-care protocol that has compression ultrasound from the inguinal ligament through the popliteal vein to the calf veins confluence.48
Two-region ultrasound is a express protocol that has compression of the femoral and popliteal regions.46,49 It is sometimes described as ii-point ultrasound, only this term is misleading because the proper protocol is 2 areas rather than two compressions.
The almost appropriate point-of-care examination for diagnosis of DVT is ECUS. ECUS is favored over the 2-region compression ultrasound, because ECUS volition find isolated femoral vein thrombosis that is present in 5% to 7% of those with DVT.five,8
A negative ECUS or 2-region exam requires a follow-up CDUS in 5 days to 1 week because the dogie is non evaluated.46,50 A CDUS should be performed after a positive limited ultrasound so that the unabridged venous system is mapped, including Doppler and calf evaluation.
Adequate training and experience with normal and aberrant studies are necessary to minimize the errors of signal-of-care ultrasound.16,46,51,52 Further research is needed to decide the blazon and duration of acceptable grooming and competency assessment.
Follow-Upwards Ultrasound
Most patients practise not need additional ultrasound after a negative CDUS study in qualified laboratories. In that location are exceptions. If symptoms of DVT persist or worsen, a follow-up ultrasound at 5 days to 1 week or before is recommended.53
A technically compromised report may too need a follow-upwards at 5 days to 1 week. Limitations in consummate ultrasound are less common in the femoropopliteal segments than in the calf.54 Color Doppler filling and symmetrical spectral Doppler flow patterns in the popliteal veins improve the confidence that the study is negative. Short areas of noncompressible calf veins are also unlikely to be significant.54 Other testing, including D-dimer or additional imaging, may exist appropriate in this setting.
Isolated iliac vein thrombosis occurs in one.half-dozen% of those with DVT.12 Imaging of the iliac and pelvic veins is warranted in patients whose signs and symptoms suggest iliocaval disease (eg, patients with whole-leg swelling with normal compression ultrasound). This may exist accomplished by pelvic venous ultrasound, computed tomography, or magnetic resonance. Considering the accuracy of duplex ultrasound for iliocaval DVT is not established, the threshold for computed tomography or magnetic resonance venography should exist depression.55
The report of a negative CDUS should land there are no femoropopliteal and no dogie DVT in the visualized calf veins. If clinical symptoms are inconsistent or if there are persistent or worsening symptoms, further imaging (possibly involving the iliac veins) may be warranted.
Recurrent DVT
New DVT after prior DVT is common.56 The presence of scarring past ultrasound is a take chances cistron for recurrence.57 Astute recurrent thrombus may exist difficult to distinguish from scar. The best ultrasound sign for recurrent DVT is an abnormality in a previously normal vein segment in the same or contralateral leg.14 Contralateral DVT is non uncommon.58 New acute thrombosis in an expanse of scarring is also diagnostic but can be difficult to identify and interpret.14,29,59 Serial increment of the size of the compressed vein >four mm is likewise proposed, just the accuracy of this finding is controversial.threescore
Serial scanning or D-dimer may be helpful in cases where the ultrasound does not notice clear new abnormalities or the findings are difficult to interpret.fourteen,61,62 The absenteeism of modify on follow-upwardly ultrasound at i to three days and at 7 to ten days has been proposed to effectively exclude recurrent DVT.14,17 Magnetic resonance is also existence investigated as a reasonable investigation.62
Follow-Up on Treatment
Patients on adequate treatment practice not do good from serial ultrasound during the course of handling unless the findings of a repeat examination would affect management.39 Modest progression in the extent of thrombus can occur despite adequate anticoagulation. These changes, per se, exercise non bespeak the demand for an junior vena cava filter or a change in anticoagulant.24,63,64
Ultrasound at the stop of handling is recommended to constitute a baseline for hereafter assessments.14,57,59,61,65 The reliability of CDUS to diagnose or exclude recurrent DVT is improved by having a posttreatment baseline ultrasound to determine which veins are normal and which are scarred.61,65
Show supporting using residual ultrasound abnormalities to guide duration of anticoagulation is weak. Farther research is warranted to determine if there are any sonographic criteria that may be useful in this setting.7
Unaddressed Problems
The conference did non address several areas that are relevant to lower extremity venous ultrasound. The value of ultrasound as a screening written report for asymptomatic patients is not established.66 The prevalence of isolated calf vein thrombosis is variable, and more than research is needed to make up one's mind its frequency and the adventure and take chances factors for propagation of untreated calf thrombus.67
Conclusions
Most current guidelines for venous ultrasound have multiple workflows that may pb to wrong application of algorithms and, potentially, medical errors. For patients who demand a venous ultrasound examination, adoption of a single, standardized consummate duplex ultrasound exam volition simplify the workup and follow-up of most patients. At the time of this examination, more than patients volition be diagnosed, specially with calf DVT. A diagnosis of calf DVT has advantages irrespective of the decision for or against treatment. For those patients for whom timely ultrasound is not available and there are qualified individuals to perform point-of-care ultrasound, ECUS is recommended. For patients with express examinations, persistent or worsening symptoms, or indeterminate results, serial ultrasound or pelvic imaging may be required.
Acknowledgments
The authors thank Heather Gale, Md, for Figure 2.
Footnotes
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Source: https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.117.030687
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