Imaging of DVT: A Multi-modality Overview

Transcription

1 Imaging of DVT: A Multi-modality Overview Douglas S. Katz, MD Imaging of DVT: A Multi-modality Overview STR 2010 Annual Meeting Workshop Douglas S. Katz, M.D., F.A.C.R. Vice Chair for Clinical Research and Education, and Director of Body Imaging, Winthrop-University Hospital, Mineola, NY, USA Professor of Clinical Radiology, State University of New York at Stony Brook Conflict of Interest Deputy Editor/Consultant to the Editor, Radiology Accurate clinical diagnosis of deep venous thrombosis (DVT) is notoriously difficult The same is true of pulmonary embolism (PE) PE and DVT are part of the same process of venous thromboembolism Most DVT is believed to begin in the calves and about 90%+ of PE are believed to originate from the deep veins of legs/pelvis usually begins around leaflets of venous valves, especially in calves, & can propagate superiorly Alternatively can form in the abdomen, pelvis, or upper thigh (e.g., due to obstruction), and then propagate inferiorly DVT is related to stasis, hypercoagulability, & trauma to the venous wall (Virchow s triad) Risk factors include: various blood disorders, malignancy, estrogen administration, dehydration, recent surgery or trauma, prolonged immobility, heart failure, mass effect on veins, obesity, pregnancy, age > 40, and prior DVT Up to 2/3 of patients with lower extremity (LE) DVT are asymptomatic Sequelae include PE & chronic venous disease The prevalence of identifiable DVT in patients with PE is variable A multi-center report of over 5000 patients with DVT shown on ultrasound (Goldhaber SZ et al. Am J Cardiol 2004): PE in 14.5%; 90% had signs/symptoms of DVT and/or PE Unilateral lower extremity DVT in 77%, bilateral in 12%; of these, 15% were isolated to the calf Upper extremity DVT in 11% Acute DVT may embolize, may resolve completely over time, or may contract/scar with residual varying degrees of occlusion/obstruction, wall thickening, and damaged/incompetent valves For decades, conventional venography was the test of choice for suspected DVT in the legs, pelvis, and inferior vena cava (IVC) (Redman HC Radiology 1988) Conventional venography: clot is identified as a filling defect or implied by complete non-filling of a vein Problems with conventional venography include (Redman HC Radiology 1988): difficulty in obtaining access, pain, contrast reactions, and paradoxical post-procedure DVT in a minority of patients; the examination is somewhat labor intensive The patient must travel to the radiology department 5-10% are technically inadequate interobserver disagreement occurs in 10%+ of examinations With the introduction of ultrasound (US), lower extremity venography now is almost never done for diagnosis alone but has occasional use for upper extremities/thoracic imaging Ultrasound Ultrasound Technique/Findings Introduced in the late 1980s Now the initial imaging test of choice for patients with signs/symptoms suggesting lower or upper extremity DVT Advantages: very high accuracy for thigh and arm evaluation for acute DVT relatively low cost portable no ionizing radiation readily repeatable Current techniques still rely primarily on compression sonography If pressure from the transducer completely collapses the vein, DVT is absent; DVT is present if the vein does not completely collapse Obtain transverse images of common femoral vein (CFV), superficial femoral vein (SFV), & popliteal vein (PV) along their courses with a 5 or 7.5 MHz linear transducer Supplement with sagittal color & spectral Doppler images (although these are usually routinely performed anyway) Color/spectral Doppler is helpful in obese patients/when imaging deep areas, especially the superficial femoral vein in the adductor canal (Lewis BD et al. Radiology 1994) Also helpful for indirect evidence of pelvic venous occlusion a monophasic waveform in the common femoral vein is a reliable indicator of proximal venous obstruction (Lin EP et al. J Ultrasound Med 2007) Augmentation did not yield any additional diagnoses of DVT in a series of almost 2000 US examinations (Lockhart ME et al. AJR 2005) Acute DVT venous distension can be present but echogenicity/visibility of clot is variable Alternative diagnoses may be identified with US e.g. hematoma, ruptured popliteal fossa cyst (Sutter ME et al. J Emerg Med) 385

2 Ultrasound Accuracy & Pitfalls Accuracy of US for DVT in the thighs of symptomatic patients approaches 100% (Fraser JD et al. Radiology 1999) However US may be limited with obese patients, with marked leg edema, & with overlying casts There is still some controversy whether to routinely image both lower extremities or only the symptomatic leg (Rosen MP et al. Semin US CT MR 1997; Lockhart ME AJR 2005); isolated contralateral DVT was rare in the latter series Most centers routinely scan both legs unless there is a good reason not to Some authors advocate a limited examination with imaging at the groin and behind the knee only (Pezzullo JA et al. Radiology 1996) Clot isolated within the thigh to the SFV has an incidence approaching 20% (Maki DD et al. AJR 2000; Katz DS et al. RadioGraphics 2002; Ford MN et al. J Clin Ultrasound 2001) so the literature does not support this practice Duplication of the SFV is very common up to 50%; if clot is present in only one of two limbs, US may be falsely-negative if only the patent limb is seen (Screaton NJ et al. Radiology 1998; Quinlan DJ et al. Radiology 2003) Ultrasound Accuracy & Pitfalls Correctly recognizing chronic DVT (and acute on top of chronic DVT) is problematic on all non-invasive imaging modalities Up to 50% of patients on followup US for acute DVT have residual abnormalities (Murphy TP et al. Radiology 1990) Chronic DVT findings include: increased clot echogenicity irregularly thickened venous walls small caliber veins collateral veins However, these findings may not be present, the echogenicity of chronic DVT is variable, and chronic DVT may not be distinguishable from acute DVT (Murphy TP et al. Radiology 1990; Spritzer CE et al. Radiology 1998) Differentiating post-phlebitic syndrome from chronic DVT is important in symptomatic patients repeat US is very useful Obtain repeat US in patients with DVT who become asymptomatic after initial therapy, for a new future baseline, and to determine whether therapy should be continued or not (Murphy TP et al. Radiology 1990; Siragusa S et al. Blood 2008) Ultrasound Role in Patients without DVT Symptoms Ultrasound - Calves Utility of US in patients with suspected PE but without signs or symptoms of DVT is controversial (Ford MN et al. J Clin Ultrasound 2001) Previous algorithms included US after indeterminate V/Q scan or after a negative or non-diagnostic CT pulmonary angiography (CTPA) study but the incidence of DVT is very variable (Girard P et al. Chest 1999; Turkstra F et al. Ann Intern Med 1997) If US is done first in patients with r/o PE, if negative then PE is not excluded, while if positive the presence of PE is assumed but not proven and if actually present the extent of PE is not known Much poorer results on US in asymptomatic patients when compared with conventional venography (e.g., patients after joint replacements) the clots are usually smaller and nonocclusive, and the incidence of calf DVT is much higher (Wells PS et al. Ann Intern Med 1995) - no proven role for US in such patients, especially if they are on DVT prophylaxis US of the calves (and pelvis) is not routinely performed at most centers because of low accuracy and the high incidence of non-diagnostic studies (Gottlieb RH et al. J Clin Ultrasound 1999) If a patient specifically reports focal pain in the calf then do attempt to image the area of pain The incidence & significance of and therapy for isolated calf DVT remains controversial Reports of up to 32% of patients with calf vein DVT propagating on serial US and up to 30% with recurrence of isolated untreated calf DVT within 3 months (Deitcher SR et al. Med Clin North Am 2003) Calf DVT has also been associated with the postphlebitic syndrome Both symptomatic and asymptomatic calf DVT seem to propagate with equal frequency (Deitcher SR et al. Med Clin North Am 2003) Ultrasound - Calves Some authors recommend follow-up thigh US at one week, particularly if patient symptoms continue but the initial US examination is negative for the thigh portion of the examination, so as to not miss calf DVT propagating to the thighs (Gottlieb RH et al. AJR 1999; Pezzullo JA et al. Radiology 1996) Not aware as to how often this is actually done, and more recent data suggests compliance is poor (McIlrath ST et al. Am J Emerg Med 2006) Incidence of calf DVT is not trivial (isolated to calves in 57% in one relatively recent series (Subramaniam RM et al. Radiology 2005)), and some patients have concurrent PE (Katz DS et al. RadioGraphics 2002; Rose SC et al. J Ultrasound Med 1994) Upper Extremity DVT Imaging The incidence of upper extremity DVT (UEDVT) is increasing due to the widespread use of central venous catheters, pacemakers, AICDs, & other devices UEDVT also may be related to hypercoagulability, malignancy, low-flow states, and effort thrombosis in athletic young people (especially men with thoracic outlet syndrome) (Volturo CA et al. Emerg Med Clin North Am 1994) Signs/symptoms of UEDVT include pain and swelling but are, as with lower extremity DVT, not specific (Joffe HU et al. Circulation 2002; Mustafa S et al. Chest 2003; Giess CS et al. J Ultrasound Med 2002) 386

3 Upper Extremity DVT Imaging Combined CT and Pulmonary Angiography The prevalence of UEDVT in oncology patients with central venous catheters is very variable, whether symptomatic or not (range 7 48%), but is higher than in non-oncology patients (Gaitini D et al. J Ultrasound Med 2006) The exact relationship of UEDVT to clinically significant PE is unknown, although the risk is estimated at 15% (Giess CS et al. J Ultrasound Med 2002) The initial test of choice is US, which is up to 95% accurate Only the symptomatic side is usually studied in contrast to lower extremity US (Lewis BD 1998) Image axillary, brachial, and internal jugular veins with compression, supplemented with color and spectral Doppler as with lower extremity US The subclavian vein is not easily compressed due to overlying clavicle so rely on color Doppler The superior vena cava and central portions of brachiocephalic veins are not routinely seen Rely on secondary signs - absence of pulsatility/respiratory variation (Giess CS et al. J Ultrasound Med 2002) Other cross-sectional imaging tests (CT & MR) are useful for further evaluation of suspected central thoracic venous thrombosis CT pulmonary angiography is the noninvasive test of choice for suspected PE Since PE and DVT are aspects of the same disease, if the deep veins are imaged with CT immediately after the lungs, the presence/absence of DVT and the overall burden and distribution of clot can be demonstrated One-stop examination This combined protocol requires only a few extra minutes but adds images to review and radiation dose, and the dose of IV contrast needs to be higher compared with if only CTPA is performed (Katz DS et al. RadioGraphics 2002; Loud PA et al. AJR 1998) CT venography (CTV) is useful even if CTPA is positive, for identifying coexistent DVT in the thighs & pelvis; the latter reportedly increases the risk for additional emboli CTV may salvage the occasionally non-diagnostic or limited it CTPA study (Katz DS et al. RadioGraphics 2002) 7% in one MDCT series (Jones SE et al. Radiology 2005) CTVPA is still routinely performed on most of our patients undergoing CTPA unless: a) patient is pregnant; b) patient had a recent negative leg US; c) patient is young (consider latter on case-by-case basis) 3 to 3.5 minutes from the start of IV contrast for CTPA obtain consecutive 5 mm images in groups of four, with 2 to 3 cm gaps, from diaphragm to ankles Recommend contrast with at least 300 mg I/mL and use ml Clot: filling defect within a deep vein; acute DVT often expands the vein, and has associated perivenous edema/enhancement of the venous wall (Loud PA et al. AJR 1998; Loud PA et al. Radiology 2001) Prefer the survey technique and not continuous images, to reduce overall radiation burden and number of images to review Goal is to identify potentially important clot burden, but not every small DVT PIOPED II supports use of discontinuous images little difference between them and continuous images in the same 150 examinations 89% agreement, & equivalent accuracy to lower extremity sonography (Goodman LR et al. AJR 2007) Various controversies regarding CTV whether to do it, when, how, is it cost-effective, how much evidence is there to support its use (Dodd JD et al. Radiology 2007; Goodman LR et al. Radiology 2009) The more recent literature has been more mixed but is still somewhat positive towards the utility of CTV, which reflects the decreased yield of CTV (& increased radiation exposure c/w CTPA alone) Corresponds to the decreasing overall yield of CTPA, due to widespread use/over-utilization (Hunsaker AR et al. AJR 2008; Nazaroglu H et al. AJR 2009; Jones C et al. Am Surg 2008; Stein PD et al. Clin Appl Thromb Hemost 2009; Revel MP J Thromb Hemost 2008) CTVPA: Accuracy High accuracy has been reported for CT venography, for thigh DVT identification or exclusion (Loud PA et al. Radiology 2001; Ghaye B et al. Eur Radiol 2002; Cham MD et al. Radiology 2000 & Radiology 2005) In 308 patients 97% sensitivity & 100% specificity c/w US (Loud PA et al. Radiology 2001) Addition of CTV to CTPA has increased the overall diagnostic yield of venous thromboembolism by 20%- 27%+ in earlier series (Cham MD et al. Radiology 2005; Richman PB et al. J Thromb Haemost 2003; Ghaye B et al. Radiology 2006) CTV increased the sensitivity of CTPA alone from 83% to 90% in PIOPED II (Stein PD et al. NEJM 2006) 387

4 CTVPA: Calves and Complex Anatomy Recommend routine imaging of the calves on CT venography, although this is controversial Although as noted the clinical importance of calf DVT remains controversial, although in contrast to ultrasound, DVT is usually readily and rapidly identified or excluded on CTV CTV clearly reveals complex anatomy and pathology - e.g. superficial venous clot; clot in the profunda femoral vein in a substantial minority of patients with DVT (an area not usually imaged with US); and pelvic DVT, which may be difficult to image with US CT : Evaluation of Underlying Anatomic IVC/Iliac Vein Anomalies Contiguous multi-detector CT venography acquisition provides information on underlying anatomic abnormalities in iliofemoral DVT perform in very selected circumstances for dedicated venous imaging 45 of 56 patients with iliofemoral DVT (44 left-sided) had anatomic abnormalities evident, especially compression of the left common iliac vein by the right common iliac artery (exaggerated by a bony spur in nine) (Chang JW et al. JVIR 2004) Also use a contiguous acquisition for occasional problem solving (e.g., a dedicated CT venogram of the pelvis and/or legs after non-diagnostic US we have done this in a small number of patients in the past few years) CTVPA: Pelvic & Chronic DVT CTVPA: Accuracy and Pitfalls Report of 1745 patients DVT on 167 CTV exams (9.6%), and 23% of these had iliac vein and/or inferior vena cava involvement (Cham MD et al. RSNA 2003; published in modified form, Radiology 2005) Accurate detection of chronic DVT is also problematic as on other cross-sectional imaging studies and not well studied yet - findings parallel those on US (small veins, partial filling defects, no perivenous edema or venous wall enhancement, and calcification) A relatively small percentage of CTV studies are nondiagnostic especially in patients with poor cardiac function and/or substantial lower extremity atherosclerosis (Katz DS et al. RadioGraphics 2002; Ghaye B et al. Eur Radiol 2002; Arakawa H et al. AJR 2007) If CTPA is negative in such patients or additional information is needed regarding the lower extremities, then US should be performed US and CTV are complementary in a subset of patients MR Imaging for DVT MR for DVT imaging was first introduced in the early 1990s High accuracy of MR (i.e., MR venography, or MRV) compared with conventional venography for the pelvis and the thighs, but MR is less accurate for the calves (Cantwell CP et al. JVIR 2006) Can use spin-echo, gradient-recalled echo, and gadolinium-enhanced sequences (Evans AJ et al. AJR 1993; Polak JF et al. Semin US CT MR 1999) MR is also advantageous for imaging suspected central thoracic venous clot readily see veins compared with US, and the causes of clot, e.g. a central mass Can also find central thoracic DVT/thrombosis on CTPA MR Imaging for DVT DVT findings on MR: absent venous flow, filling defects, and (in a minority of patients) perivenous inflammation analogous to the findings on CTV MR may be superior to US and CTV for the determination of chronicity of DVT although this has not been well studied (Spritzer CE et al. Radiology 1998) MR is used as a problem-solving tool in most practices, especially for pelvic vein imaging The true frequency of pelvic DVT is underestimated with US and in pregnant patients, recent pelvic surgery, or pelvic malignancy, DVT may start in the pelvis and propagate inferiorly into the thighs (Spritzer CE et al. Radiology 2001) 388

5 MR Imaging for DVT Study of 212 patients with DVT extending proximal to the inguinal ligament on US; the patients then underwent MR (Borst-Krafek B et al. J Vasc Surg 2003) Extension to iliac veins/ivc shown in 89% Iliac veins were involved in 142 patients and the IVC in 46 patients Iliac DVT was 2X more frequent on the left compared with the right Extent of DVT had no correlation with the frequency of symptomatic PE In patients with a contraindication to iodinated contrast who can receive gadolinium can do MR pulmonary angiography and venography: obtain axial GRE images after MR pulmonary angiogram gadolinium augments MR signal in patent veins Combined MR pulmonary angiography & venography protocol increased yield by 16% c/w MRPA alone in one study (Kluge A et al. AJR 2006) Diagnostic venography is now limited to specific scenarios: prior to placement of IVC filters evaluation of central DVT in the proximal arms/chest as a prelude for intervention: thrombolysis, thrombectomy, and stent placement with indeterminate US in obese patients or a markedly swollen leg, and when other modalities do not or cannot solve the problem in suspected calf DVT in patients with negative or indeterminate US, where the findings would change management (although the latter two scenarios may be evaluated with CTV or MRV) Non-visualization of portions of the subclavian and innominate veins and of the superior vena cava as noted is a common situation with US Can easily evaluate these veins with a contrast injection into the antecubital vein or via basilic/brachial vein access with catheterization of the subclavian vein, under fluoroscopic control Diagnostic venography is performed routinely immediately prior to IVC filter placement: to evaluate for clot and venous anomalies, and also to measure the IVC to determine the type of filter to place At our institution, we routinely hand inject into the ipsilateral iliac vein when planning to place an IVC filter via the femoral approach, to evaluate for iliac DVT We then perform an IVC gram via a left iliac venous injection, to look for congenital anomalies We then perform a selective left renal venogram to check for a circumaortic renal vein, which can serve as a collateral pathway for emboli around the IVC (Beckman CF et al. AJR 1979; Phillips E 1969) Summary Ultrasound is the imaging test of choice for suspected lower or upper extremity DVT US has high accuracy in symptomatic patients for the deep thigh veins and in the arms US is less accurate for the calves and the pelvis, and in asymptomatic patients Combined CT pulmonary angiography and CT venography permits comprehensive assessment for PE and DVT, & serves as a roadmap for therapy, although the yield of CTV has decreased substantially in recent years as CTPA has been increasing used/over-utilized, and CTV is not routinely performed at many institutions/practices, although there is still evidence to support its use, especially in high risk patients MR is a helpful problemsolving test, & can also be combined with MR pulmonary angiography Conventional venography is mostly of historical interest when used solely as a diagnostic study for the lower extremities via an inguinal approach is still performed at some centers, including ours, as a road-mapping technique immediately prior to IVC filter placement of the lower and upper extremities is routinely performed as part of a variety of therapeutic procedures for DVT including thrombolysis, percutaneous thrombectomy, angioplasty, and stent placement 389