ORIGINAL CONTRIBUTION deep venous thrombophlebitis; magnetic resonance imaging
Magnetic Resonance Imaging for Calf Deep Venous Thrombophlebitis Study objective: To compare magnetic resonance imaging (MRI) of the calf with venography for patients with suspected calf deep venous thrombophlebitis (DVT). Design: Ten consecutive adult patients with suspected calf D V T received venography and, within 48 hours, MRI scans. The tests were reviewed blindly by two radiologists, and results of the tests were compared. Setting: The emergency department of a large teaching hospital with an annual census of 60,000 patients. Main results: All patients with negative venograms had no suggestion of DVT on MRI scan. Two of these patients had other significant demonstrable abnormalities. Four of the five patients with positive venograms had positive calf MRI scans. One patient with a venogram that was difficult to interpret had no D V T on MRI. A thigh D V T was seen on his venogram and was suggested by MRI findings. Conclusion: MRI m a y replace ascending venography as the standard .for diagnosis of calf DVT. [Vukov LF, Berquist TH, King BF: Magnetic resonance imaging for calf deep venous thrombophlebitis. Ann Emerg Med May 199i;20:497-499.]
INTRODUCTION The accurate diagnosis of calf deep venous thrombophlebitis (DVT) poses a major dilemma for emergency physicians as well as for physicians in ambulatory care centers and office practice. Clinical signs and symptoms, such as calf swelling and tenderness, pedal edema, warmth, prominent superficial venous pattern of the affected extremity, and a positive Homan's sign, are poor indicators of DVT at best.l,2 Bedside Doppler ultrasonography,3,4 thermography,5, 6 impedence plethysmography,7, 8 and color flow Doppler studies 941 are usually not helpful for diagnosing DVT below the level of the popliteal vein. Iodine-125-1abeled fibrinogen scanning has been found to detect calf venous thrombosis accurately, but it has many practical limitations.I2, ~3 Although serial impedance plethysmograms have been used to document absence of clot propagation,14,15 a definitive diagnosis is not achieved with this approach to calf pain. Ascending venography is currently accepted as the standard for diagnosing calf DVT.12,13 Its high cost, dependence on operator skill, potential contrast media reactions, and subsequent venous thrombosis have stimulated interest in other diagnostic modalities. 16 For this reason, a pilot study was undertaken to assess the usefulness of magnetic resonance imaging (MRI) in the evaluation of patients with symptoms and signs suggestive of calf DVT.
Larry F Vukov, MD* Thomas H Berquist, MDt Bernard F King, MDt Rochester, Minnesota From the Division of Emergency Medical Services and Internal Medicine* and the Department of Diagnostic Radiology, t Mayo Clinic and Mayo Foundation, Rochester, Minnesota. Received for publication June 11, 1990. Revision received November 19, 1990. Accepted for publication December 8, 1990. Presented at the Third International Conference on Emergency Medicine in Toronto, Canada, June 1990. Address for reprints: Larry F Vukov, MD, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905.
MATERIALS A N D M E T H O D S At the. Saint Marys Hospital emergency department, Rochester, Minnesota, many patients with unilateral calf pain and symptoms and signs suggesting calf DVT are evaluated annually. The practice at our institution is to hospitalize and anticoagulate nearly all patients who have calf vein DVT. This necessitates accurate diagnosis. Ten consecutive patients seen in the ED by one of the authors between March and October 1989 had a clinical illness suggestive of calf DVT and were referred for ascending venography of the affected lower extremity.
26/497
Annals of Emergency Medicine
20:5 May 1991
]-HROMBOPHLEBITIS ~/ukov, Berquist & King
F I G U R E 2. A: Venogram, lateral
view, of left calf region shows no evidence of deep venous thrombosis. B: Transverse T2-weighted (spin echo TR:2000 ms and TE:60 ms) image of left leg in the same patient, demonstrating no evidence of deep venous thrombosis. There is an area of wellcircumscribed increased signal (arrow) in the medial head of the gastrocnemius muscle, consistent with a hematoma. basis: I. The interpretation of signs and symptoms. An giology I969;20:219-223.
pain and swelling suggestive of DVT has required the use of ascending venography, with its associated discomfort and risks, to e s t a b l i s h a diagnosis. Recently, for calf DVT, there has been a trend to use impedance plethysmography initially and to follow the patient with serial impedance p l e t h y s m o g r a m s to assess for clot propagation. However, performing serial diagnostic studies over ten to 14 days involves considerable cost and time. In most cases, no definitive diagnosis is made by using this technique. When a deep venous clot is p r o p a g a t e d and s u b s e q u e n t l y detected on impedance plethysmography, there is a potential for increased long-term morbidity when more extensive thrombosis is allowed to occur. There is no current consensus as to w h e t h e r patients with only calf vein DVT should be anticoagulated. O t h e r m o d a l i t i e s such as color flow Doppler are sensitive and specific for the diagnosis of thigh and pelvic DVT but have not been consistently helpful below the knee. MRI has been reported to be promising for thigh and deep pelvic vein thromboses, 19 but data on its usefulness for calf DVT are scanty. For patients with calf pain and possible DVT, MRI may offer certain ad28/499
vantages over ascending venography as a p r i m a r y d i a g n o s t i c m o d a l i t y . Even small calf vein thromboses are easily visualized on MRI. MRI scann i n g d e t e c t e d a l l f o u r calf v e i n thromboses in our group. In one patient whose venogram was read as " l i k e l y p o s i t i v e " for calf DVT but difficult to interpret because of slow flow, MRI showed no clot. An added benefit of MRI was a specific diagnosis of calf m u s c l e h e m a t o m a in two of the five patients with a negative venogram. Venography in these two patients provided no suggestion of the presence of intramuscular hematoma. Cost is important to consider. Both modalities require skilled operators and special equipment and are not readily available as standard emergency procedures. A unilateral lowere x t r e m i t y venogram at our institution costs approximately $650, and an MRI scan distal to the knee costs
$500.
2. Vine HS, Hillman B, Hessel SJ: Deep venous thrombosis: Predictive value of signs and symptoms. Am ] Radial 1981;136:I67-171. 3. Turnbull TJ, D y m o w s k i JJ: Emergency department use of hand-held Doppler ultrasonography. A m J Emerg Me d 1989;7:209-215. 4. Comerota AJ, Knight LC, Maurer AH: The diagnosis of acute deep venous tbrombosis: Noninvasive and ra dio~smopic techniques. Ann Vase Surg 1988;2:406-424. 5. Kjocr L, Winter Christensen S, Vestergaard AA, et ah Contact thermography as a screening test for deep venous thrombosis following major hip surgery. Acta Radial 1988;29:649-652. 6. Wallin L, Albrechtsson U, Fagher B, et ah Thermo graphy in the diagnosis of deep venous thrombosis: A comparison with 9~)Tcm-plasmin test, clinical diagnosis andl phlebography. Acta Med Stand 1983;214:15-20. 7. Hull RD, Raskob GE, LeClere JR, et al: The diagnosis of clinically suspected venous thrombosis. Cli, Chest Med 1984;5:439-456. 8. Patterson RB, Fowl RJ, Keller JD, et ah The limitations of impedance ptethysmography in the diagnosis of acute deep venous thrombosis. J Vasc Surg 1989;9: 725-730. 9. O'Leary DH, Kane RA, Chase BM: A prospective study of the efficacy of B-scan sonography in the detection of deep venous thrombosis in the lower extremities. J Clin Ultrasound 1988;16:l-8. 10. Comerota AJ, Katz ML, Greenwald LL, et al: Venous duplex imaging: Should it replace hemodynamic tests for deep venous thrombosis? J Vase Surg 1990;I1:53-61. 11. Killewich LA, Bedford GR, Beach KW, et al: Diagnosis of deep venous thrombosis: A prospective study comparing duplex scanning to contract venography. Circulation 1989;79:810-814.
CONCLUSION In a p i l o t s t u d y of ten p a t i e n t s with suspected calf DVT, MRI demonstrated a deep venous clot in those with positive venograms and delineated a d e f i n i t i v e etiology for calf pain and swelling in two of five patients without DVT. MRI scanning is not only comparable in cost to ascending venography but also associated with less patient discomfort and potential morbidity. Although more data c o m p a r i n g ascending venography and MRI in the diagnosis of calf DVT are necessary, our preliminary experience suggests that MRI may replace ascending v e n o g r a p h y as the standard test for patients suspected to have calf DVT.
15. Huisman MV, Biiller HR, ten Cate JW, et al: Serial impedance plethysmography for suspected deep venous thrombosis in outpatients: The Amsterdam General Practitioner Study. N Eng] J Med 1986;314:823-828.
REFERENCES
19. Spritzer CE, Sussman SK, Blinder RA, et al: Deep venous thrombosis evaluation with limited flip-angle, gradient-refocused MR imaging: Preliminary experience. Radiology 1988;166:371-375.
1. Haeger K: Problems of acute deep venous throm-
Annals of Emergency Medicine
12. Painter TD: Thrombophlebitis: Diagnostic techniques. Angio]ogy 1980;31:386-397. 13. Bettmann MA: Noninvasive and venographic diagnosis of deep vein thrombosis. Cardiovosc Intervent Radio] 1988;1 l(suppl):S15-S20. [4. Hirsh J, Hull RD, Raskob GE: Clinical features and diagnosis of venous thrombosis. J A m Co]I Cardio] 1986;8{suppl B}:II4B-127B.
16. Bettmann MA, Paulin S: Leg phlebography: The incidence, nature, and modification of undesirable side effects. Radiology 1977;122:101-104. 17. Erdman WA, Jayson HT, Redman HC, et al: Deep venous thrombosis of extremities: Role of MR imaging in the diagnosis. Radiology 1990;174:425 431. 18. Francis CW, Foster TH, Totterman S, et al: Monitoring of therapy for deep vein thrombosis using magnetic resonance imaging. Acta Radio] 1989;30:445-447.
20:5 May 1991
THROMBOPHLEBITIS Vukov, Berquist & King
FIGURE 1. A: Transverse proton-density-weighted (spin echo TR:2000 ms and TE:30 ms) MRI scan of the legs. Increased signal is apparent in the soleus muscle of the left leg (arrowheads), consistent with edema. Increase in size and decrease in signal are seen in the left peroneal vein, consistent with intraluminaI thrombus. B: Transverse M R I scan (GRASS, TR:40 ms and TE:20 ms; flip angle, 60 °) of left leg of same patient, showing enlarged left peroneal vein with decreased signal (double arrows), consistent with intralumina] thrombus. Note the normal size and increased signal in the normal veins (open arrows). C: Left lower-extremity (calf region) venogram, demonstrating intraluminal thrombus in multiple deep veins (small arrows) including the peroneal vein. Consent for s u b s e q u e n t MRI scanning was o b t a i n e d before the venographic procedure~ MRI scans of both lower extremities distal to the popliteal veins were obtained w i t h i n 48 hours a f t e r a s c e n d i n g v e n o g r a p h y had been p e r f o r m e d , r e g a r d l e s s of whether the venographic results were positive or negative. Venography was p e r f o r m e d w i t h cannulation of the dorsal pedal vein for contrast m e d i a injection. For MRI scans, both axial spin echo TR:2000 and TE:30,60, and axial gradient recalled a c q u i s i t i o n in a s t e a d y s t a t e (GRASS) images were obtained. The patients were in the prone position. Spin echo i m a g i n g was p e r f o r m e d with 5 - r a m - t h i c k s l i c e s a n d a 2.5m m i n t e r s l i c e gap. G R A S S i m a g e s were o b t a i n e d by u s i n g t h e s a m e slice selection but w i t h a 128 × 256 matrix, two acquisitions, and a flip angle of 60 °. The v e n o g r a m s a n d M R I s c a n s were reviewed blindly by two boardcertified radiologists proficient in interpreting both diagnostic procedures. 20:5 May 1991
Because of the small n u m b e r of patients in this pilot study, statistical analysis of the s e n s i t i v i t y and specificity of MRI was not feasible. However, p o t e n t i a l l y meaningful observations were m a d e c o n c e r n i n g visuali z a t i o n of a c u t e v e n o u s t h r o m b o s i s , presence of a n o n D V T diagnosis, and costs of the two tests. N o other tests for e v a l u a t i n g DVT were p e r f o r m e d on t h e s e p a t i e n t s , and no t h r o m b o lyric agents were given to p a t i e n t s w i t h p o s i t i v e venograms. F o l l o w - u p care was p r o v i d e d by t h e p a t i e n t ' s hospital or personal physician.
RESULTS In t h e t e n c o n s e c u t i v e p a t i e n t s w i t h signs and s y m p t o m s suggestive of calf DVT, venograms were positive in five and negative in five. In four of those with positive venograms, a small or extensive calf clot was seen (Figure 1); in t h e fifth p a t i e n t , t h e venogram demonstrated extensive D V T in t h e t h i g h (despite l a c k of clinical signs and s y m p t o m s ) and diff i c u l t - t o - v i s u a l i z e calf v e i n s secondary to slow flow of contrast material. In the five p a t i e n t s w i t h p o s i t i v e venograms, MRI d e m o n s t r a t e d a definite clot in the calf veins of four patients b u t n o t the fifth patient, w h o was a young paraplegic. In this last p a t i e n t , t h e r e was d i s t e n t i o n of the deep veins and calf edema. Both radio l o g i s t s s u g g e s t e d t h a t t h e s e MRI findings m i g h t indicate the presence Annals of Emergency Medicine
of D V T in m o r e p r o x i m a l v e i n s , w h i c h was clearly d e m o n s t r a t e d on the ascending venogram. Even a small clot in the soleal calf vein in one p a t i e n t was accurately visualized by MRI. N o n e of these patients w i t h calf D V T had had prior episodes of DVT, so no c o m p a r i s o n s c o u l d be made b e t w e e n n e w and old clots, as h a d b e e n a c c o m p l i s h e d in s e v e r a l e a r l i e r s t u d i e s of t h i g h and p e l v i c vein thromboses, t 7, t s MRI d e m o n s t r a t e d patency of the deep v e n o u s s y s t e m in all five pat i e n t s w i t h n e g a t i v e venograms. In two of t h e s e patients, MRI d e m o n strated calf m u s c l e h e m a t o m a (Figure 2) as the cause of the warm, swollen, tender calf. One of these patients had been k i c k e d in the calf while playing soccer several days before presentation. The other patient had not had any obvious t r a u m a r e s p o n s i b l e for the h e m a t o m a . T h e three o t h e r patients w i t h negative venograms had either generalized calf m u s c l e e d e m a (two) or subcutaneous e d e m a indicat i v e of c e l l u l i t i s as t h e a b n o r m a l finding on MRI. There were no complications related to the venography, and the MRI was well tolerated by all patients.
DISCUSSION For m a n y years, evaluation of calf 498/27
Magnetic Resonance Imaging for Calf Deep Venous Thrombophlebitis Study objective: To compare magnetic resonance imaging (MRI) of the calf with venography for patients with suspected calf deep venous thrombophlebitis (DVT). Design: Ten consecutive adult patients with suspected calf D V T received venography and, within 48 hours, MRI scans. The tests were reviewed blindly by two radiologists, and results of the tests were compared. Setting: The emergency department of a large teaching hospital with an annual census of 60,000 patients. Main results: All patients with negative venograms had no suggestion of DVT on MRI scan. Two of these patients had other significant demonstrable abnormalities. Four of the five patients with positive venograms had positive calf MRI scans. One patient with a venogram that was difficult to interpret had no D V T on MRI. A thigh D V T was seen on his venogram and was suggested by MRI findings. Conclusion: MRI m a y replace ascending venography as the standard .for diagnosis of calf DVT. [Vukov LF, Berquist TH, King BF: Magnetic resonance imaging for calf deep venous thrombophlebitis. Ann Emerg Med May 199i;20:497-499.]
INTRODUCTION The accurate diagnosis of calf deep venous thrombophlebitis (DVT) poses a major dilemma for emergency physicians as well as for physicians in ambulatory care centers and office practice. Clinical signs and symptoms, such as calf swelling and tenderness, pedal edema, warmth, prominent superficial venous pattern of the affected extremity, and a positive Homan's sign, are poor indicators of DVT at best.l,2 Bedside Doppler ultrasonography,3,4 thermography,5, 6 impedence plethysmography,7, 8 and color flow Doppler studies 941 are usually not helpful for diagnosing DVT below the level of the popliteal vein. Iodine-125-1abeled fibrinogen scanning has been found to detect calf venous thrombosis accurately, but it has many practical limitations.I2, ~3 Although serial impedance plethysmograms have been used to document absence of clot propagation,14,15 a definitive diagnosis is not achieved with this approach to calf pain. Ascending venography is currently accepted as the standard for diagnosing calf DVT.12,13 Its high cost, dependence on operator skill, potential contrast media reactions, and subsequent venous thrombosis have stimulated interest in other diagnostic modalities. 16 For this reason, a pilot study was undertaken to assess the usefulness of magnetic resonance imaging (MRI) in the evaluation of patients with symptoms and signs suggestive of calf DVT.
Larry F Vukov, MD* Thomas H Berquist, MDt Bernard F King, MDt Rochester, Minnesota From the Division of Emergency Medical Services and Internal Medicine* and the Department of Diagnostic Radiology, t Mayo Clinic and Mayo Foundation, Rochester, Minnesota. Received for publication June 11, 1990. Revision received November 19, 1990. Accepted for publication December 8, 1990. Presented at the Third International Conference on Emergency Medicine in Toronto, Canada, June 1990. Address for reprints: Larry F Vukov, MD, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905.
MATERIALS A N D M E T H O D S At the. Saint Marys Hospital emergency department, Rochester, Minnesota, many patients with unilateral calf pain and symptoms and signs suggesting calf DVT are evaluated annually. The practice at our institution is to hospitalize and anticoagulate nearly all patients who have calf vein DVT. This necessitates accurate diagnosis. Ten consecutive patients seen in the ED by one of the authors between March and October 1989 had a clinical illness suggestive of calf DVT and were referred for ascending venography of the affected lower extremity.
26/497
Annals of Emergency Medicine
20:5 May 1991
]-HROMBOPHLEBITIS ~/ukov, Berquist & King
F I G U R E 2. A: Venogram, lateral
view, of left calf region shows no evidence of deep venous thrombosis. B: Transverse T2-weighted (spin echo TR:2000 ms and TE:60 ms) image of left leg in the same patient, demonstrating no evidence of deep venous thrombosis. There is an area of wellcircumscribed increased signal (arrow) in the medial head of the gastrocnemius muscle, consistent with a hematoma. basis: I. The interpretation of signs and symptoms. An giology I969;20:219-223.
pain and swelling suggestive of DVT has required the use of ascending venography, with its associated discomfort and risks, to e s t a b l i s h a diagnosis. Recently, for calf DVT, there has been a trend to use impedance plethysmography initially and to follow the patient with serial impedance p l e t h y s m o g r a m s to assess for clot propagation. However, performing serial diagnostic studies over ten to 14 days involves considerable cost and time. In most cases, no definitive diagnosis is made by using this technique. When a deep venous clot is p r o p a g a t e d and s u b s e q u e n t l y detected on impedance plethysmography, there is a potential for increased long-term morbidity when more extensive thrombosis is allowed to occur. There is no current consensus as to w h e t h e r patients with only calf vein DVT should be anticoagulated. O t h e r m o d a l i t i e s such as color flow Doppler are sensitive and specific for the diagnosis of thigh and pelvic DVT but have not been consistently helpful below the knee. MRI has been reported to be promising for thigh and deep pelvic vein thromboses, 19 but data on its usefulness for calf DVT are scanty. For patients with calf pain and possible DVT, MRI may offer certain ad28/499
vantages over ascending venography as a p r i m a r y d i a g n o s t i c m o d a l i t y . Even small calf vein thromboses are easily visualized on MRI. MRI scann i n g d e t e c t e d a l l f o u r calf v e i n thromboses in our group. In one patient whose venogram was read as " l i k e l y p o s i t i v e " for calf DVT but difficult to interpret because of slow flow, MRI showed no clot. An added benefit of MRI was a specific diagnosis of calf m u s c l e h e m a t o m a in two of the five patients with a negative venogram. Venography in these two patients provided no suggestion of the presence of intramuscular hematoma. Cost is important to consider. Both modalities require skilled operators and special equipment and are not readily available as standard emergency procedures. A unilateral lowere x t r e m i t y venogram at our institution costs approximately $650, and an MRI scan distal to the knee costs
$500.
2. Vine HS, Hillman B, Hessel SJ: Deep venous thrombosis: Predictive value of signs and symptoms. Am ] Radial 1981;136:I67-171. 3. Turnbull TJ, D y m o w s k i JJ: Emergency department use of hand-held Doppler ultrasonography. A m J Emerg Me d 1989;7:209-215. 4. Comerota AJ, Knight LC, Maurer AH: The diagnosis of acute deep venous tbrombosis: Noninvasive and ra dio~smopic techniques. Ann Vase Surg 1988;2:406-424. 5. Kjocr L, Winter Christensen S, Vestergaard AA, et ah Contact thermography as a screening test for deep venous thrombosis following major hip surgery. Acta Radial 1988;29:649-652. 6. Wallin L, Albrechtsson U, Fagher B, et ah Thermo graphy in the diagnosis of deep venous thrombosis: A comparison with 9~)Tcm-plasmin test, clinical diagnosis andl phlebography. Acta Med Stand 1983;214:15-20. 7. Hull RD, Raskob GE, LeClere JR, et al: The diagnosis of clinically suspected venous thrombosis. Cli, Chest Med 1984;5:439-456. 8. Patterson RB, Fowl RJ, Keller JD, et ah The limitations of impedance ptethysmography in the diagnosis of acute deep venous thrombosis. J Vasc Surg 1989;9: 725-730. 9. O'Leary DH, Kane RA, Chase BM: A prospective study of the efficacy of B-scan sonography in the detection of deep venous thrombosis in the lower extremities. J Clin Ultrasound 1988;16:l-8. 10. Comerota AJ, Katz ML, Greenwald LL, et al: Venous duplex imaging: Should it replace hemodynamic tests for deep venous thrombosis? J Vase Surg 1990;I1:53-61. 11. Killewich LA, Bedford GR, Beach KW, et al: Diagnosis of deep venous thrombosis: A prospective study comparing duplex scanning to contract venography. Circulation 1989;79:810-814.
CONCLUSION In a p i l o t s t u d y of ten p a t i e n t s with suspected calf DVT, MRI demonstrated a deep venous clot in those with positive venograms and delineated a d e f i n i t i v e etiology for calf pain and swelling in two of five patients without DVT. MRI scanning is not only comparable in cost to ascending venography but also associated with less patient discomfort and potential morbidity. Although more data c o m p a r i n g ascending venography and MRI in the diagnosis of calf DVT are necessary, our preliminary experience suggests that MRI may replace ascending v e n o g r a p h y as the standard test for patients suspected to have calf DVT.
15. Huisman MV, Biiller HR, ten Cate JW, et al: Serial impedance plethysmography for suspected deep venous thrombosis in outpatients: The Amsterdam General Practitioner Study. N Eng] J Med 1986;314:823-828.
REFERENCES
19. Spritzer CE, Sussman SK, Blinder RA, et al: Deep venous thrombosis evaluation with limited flip-angle, gradient-refocused MR imaging: Preliminary experience. Radiology 1988;166:371-375.
1. Haeger K: Problems of acute deep venous throm-
Annals of Emergency Medicine
12. Painter TD: Thrombophlebitis: Diagnostic techniques. Angio]ogy 1980;31:386-397. 13. Bettmann MA: Noninvasive and venographic diagnosis of deep vein thrombosis. Cardiovosc Intervent Radio] 1988;1 l(suppl):S15-S20. [4. Hirsh J, Hull RD, Raskob GE: Clinical features and diagnosis of venous thrombosis. J A m Co]I Cardio] 1986;8{suppl B}:II4B-127B.
16. Bettmann MA, Paulin S: Leg phlebography: The incidence, nature, and modification of undesirable side effects. Radiology 1977;122:101-104. 17. Erdman WA, Jayson HT, Redman HC, et al: Deep venous thrombosis of extremities: Role of MR imaging in the diagnosis. Radiology 1990;174:425 431. 18. Francis CW, Foster TH, Totterman S, et al: Monitoring of therapy for deep vein thrombosis using magnetic resonance imaging. Acta Radio] 1989;30:445-447.
20:5 May 1991
THROMBOPHLEBITIS Vukov, Berquist & King
FIGURE 1. A: Transverse proton-density-weighted (spin echo TR:2000 ms and TE:30 ms) MRI scan of the legs. Increased signal is apparent in the soleus muscle of the left leg (arrowheads), consistent with edema. Increase in size and decrease in signal are seen in the left peroneal vein, consistent with intraluminaI thrombus. B: Transverse M R I scan (GRASS, TR:40 ms and TE:20 ms; flip angle, 60 °) of left leg of same patient, showing enlarged left peroneal vein with decreased signal (double arrows), consistent with intralumina] thrombus. Note the normal size and increased signal in the normal veins (open arrows). C: Left lower-extremity (calf region) venogram, demonstrating intraluminal thrombus in multiple deep veins (small arrows) including the peroneal vein. Consent for s u b s e q u e n t MRI scanning was o b t a i n e d before the venographic procedure~ MRI scans of both lower extremities distal to the popliteal veins were obtained w i t h i n 48 hours a f t e r a s c e n d i n g v e n o g r a p h y had been p e r f o r m e d , r e g a r d l e s s of whether the venographic results were positive or negative. Venography was p e r f o r m e d w i t h cannulation of the dorsal pedal vein for contrast m e d i a injection. For MRI scans, both axial spin echo TR:2000 and TE:30,60, and axial gradient recalled a c q u i s i t i o n in a s t e a d y s t a t e (GRASS) images were obtained. The patients were in the prone position. Spin echo i m a g i n g was p e r f o r m e d with 5 - r a m - t h i c k s l i c e s a n d a 2.5m m i n t e r s l i c e gap. G R A S S i m a g e s were o b t a i n e d by u s i n g t h e s a m e slice selection but w i t h a 128 × 256 matrix, two acquisitions, and a flip angle of 60 °. The v e n o g r a m s a n d M R I s c a n s were reviewed blindly by two boardcertified radiologists proficient in interpreting both diagnostic procedures. 20:5 May 1991
Because of the small n u m b e r of patients in this pilot study, statistical analysis of the s e n s i t i v i t y and specificity of MRI was not feasible. However, p o t e n t i a l l y meaningful observations were m a d e c o n c e r n i n g visuali z a t i o n of a c u t e v e n o u s t h r o m b o s i s , presence of a n o n D V T diagnosis, and costs of the two tests. N o other tests for e v a l u a t i n g DVT were p e r f o r m e d on t h e s e p a t i e n t s , and no t h r o m b o lyric agents were given to p a t i e n t s w i t h p o s i t i v e venograms. F o l l o w - u p care was p r o v i d e d by t h e p a t i e n t ' s hospital or personal physician.
RESULTS In t h e t e n c o n s e c u t i v e p a t i e n t s w i t h signs and s y m p t o m s suggestive of calf DVT, venograms were positive in five and negative in five. In four of those with positive venograms, a small or extensive calf clot was seen (Figure 1); in t h e fifth p a t i e n t , t h e venogram demonstrated extensive D V T in t h e t h i g h (despite l a c k of clinical signs and s y m p t o m s ) and diff i c u l t - t o - v i s u a l i z e calf v e i n s secondary to slow flow of contrast material. In the five p a t i e n t s w i t h p o s i t i v e venograms, MRI d e m o n s t r a t e d a definite clot in the calf veins of four patients b u t n o t the fifth patient, w h o was a young paraplegic. In this last p a t i e n t , t h e r e was d i s t e n t i o n of the deep veins and calf edema. Both radio l o g i s t s s u g g e s t e d t h a t t h e s e MRI findings m i g h t indicate the presence Annals of Emergency Medicine
of D V T in m o r e p r o x i m a l v e i n s , w h i c h was clearly d e m o n s t r a t e d on the ascending venogram. Even a small clot in the soleal calf vein in one p a t i e n t was accurately visualized by MRI. N o n e of these patients w i t h calf D V T had had prior episodes of DVT, so no c o m p a r i s o n s c o u l d be made b e t w e e n n e w and old clots, as h a d b e e n a c c o m p l i s h e d in s e v e r a l e a r l i e r s t u d i e s of t h i g h and p e l v i c vein thromboses, t 7, t s MRI d e m o n s t r a t e d patency of the deep v e n o u s s y s t e m in all five pat i e n t s w i t h n e g a t i v e venograms. In two of t h e s e patients, MRI d e m o n strated calf m u s c l e h e m a t o m a (Figure 2) as the cause of the warm, swollen, tender calf. One of these patients had been k i c k e d in the calf while playing soccer several days before presentation. The other patient had not had any obvious t r a u m a r e s p o n s i b l e for the h e m a t o m a . T h e three o t h e r patients w i t h negative venograms had either generalized calf m u s c l e e d e m a (two) or subcutaneous e d e m a indicat i v e of c e l l u l i t i s as t h e a b n o r m a l finding on MRI. There were no complications related to the venography, and the MRI was well tolerated by all patients.
DISCUSSION For m a n y years, evaluation of calf 498/27
