Clinical Radiology(1992) 46, 84 87
Calf Vein Anatomy and Flow: Implications for Colour Doppler Imaging G. M. B A X T E R and P. D U F F Y
Department of Radiology, Southern General Hospital, Glasgow Early experience has suggested that colour flow Doppler ultrasound may have a diagnostic role in calf vein thrombosis. Before its accuracy within the calf can be adequately assessed, normal calf vein flow and anatomy needs to be understood. We, therefore, studied 40 normal volunteers, age range 24-75 years (mean 45.4), M: F 22:18, and assessed both flow and venous diameter in each of the three sets of calf veins in the supine and erect positions and once again in both these positions following the application of an above knee band. Paired sets of veins were present in all posterior tibial and common peroneal sets, but in only 85% of the anterior tibial group. Significant flow variations were present between different sets of veins, there being relatively less appreciable flow within the common peroneal (p < 0.05). Both band application and erect posture produced significant increases in venous diameter (p < 0.01, p < 0.001) in the posterior tibial and common peroneal veins, aiding visualization but at the cost of reducing flow following band application (p < 0.05, p < 0.01). The erect posture had no deleterious effect on calf vein flow. We, therefore, recommend that when the patency of calf veins is being assessed scanning should be performed in both a supine and erect position as this will help vein visualization without a reduction in flow, and thus avoid misinterpretation. Baxter, (3. M. & Duffy, P. (1992). Clinical Radiology 46, 84-87. Calf Vein Anatomy and Flow: Implications for Colour Doppler Imaging
Accepted for Publication 9 March 1992
Venography has for many years been accepted as the 'gold standard' imaging modality in the diagnosis of lower limb venous thrombosis. Although it is undoubtedly an accurate investigative method it does have potential problems which include failure of cannulation, contrast reaction and even the induction of thrombosis, admittedly the latter complications being less frequent following the introduction of the low osmolar, non-ionic contrast agents [1]. As a consequence of these potential disadvantages, there has been a search for a suitable noninvasive alternative which has included impedance plethysmography, thermography and radioisotope imaging. All of these techniques have shown a lack of sensitivity and/or specificity with wide interstudy variation questioning the reproducibility of these techniques [2 6]. Real time ultrasound in isolation, or with the addition of duplex Doppler, has been shown to be accurate in the diagnosis of lower limb venous occlusive disease in the femoral and popliteal segments with a sensitivity approaching 90% [7-9]. With the introduction of colour Doppler technology more information, i.e. differentiation between occlusive or non-occlusive thrombus and detection of collateral circulation, is available noninvasively without prolonging examination time. Early work in this field has also indicated it may have a role in the diagnosis of calf vein thrombosis [10,11]. In view of this, and based on early encouraging work, we decided to study calf vein thrombosis in more depth. Prior to any clinical trial we felt it was necessary to scan the calf veins of 40 'normal' subjects in order to determine the number of paired veins routinely visualized by colour Doppler ultrasound, identify the best position for doing so, and thus define an optimal technique for routine scanning of these vessels. Correspondence to: Dr G. M. Baxter, Senior Registrar, Department of Radiology, Western Infirmary, Glasgow G11 5NT.
METHOD Forty normal healthy volunteers M : F 22 : 18, age range 24 75 years (mean age 45.4) had a cotour Doppler ultrasound scan of their calf veins. A wide age range was used to reflect accurately the age distribution of patients who may present with deep venous thrombosis. Exclusion criteria included a previous history of lower limb trauma, prolonged bed rest or hospitalization or a prior history or treatment for deep venous thrombosis. O f the 40 patients, the right leg was scanned in 21 cases and the left in 19. Beginning in the supine position patients were scanned using either a 5 or 7.5 M H z linear array probe (Acuson 128). In order to ensure that comparisons between calf veins were made at the same reference point, a defined point exactly mid-way between the medial and lateral malleoli and the tibial tuberosity was marked with a pen, the main field of view being restricted to a distance of 3cm above or below this midpoint, also marked on the leg. Following distal compression the number of veins accompanying each of the three major calf arteries were noted, this information being recorded on video tape. This technique was then repeated with the leg hanging over the side of the bed in an erect posture with the foot resting on a stool. Further assessment was then made in both the supine and erect position with the addition of a tightly applied above knee band, in a manner analogous to venography. The number of veins accompanying each artery were noted. An assessment of venous flow was made by two separate radiologists experienced in colour Doppler ultrasound, at completion of the trial, directly from video tape. This was done using a visual analogue scale to try and determine the best position for visualizing flow within each set of veins. The visual analogue scale is an arbitrary scale from 0 to 100: zero represented complete absence of
85
CALF VEIN ANATOMY AND FLOW Table 1 - The effect o f posture and above knee bands on flow rate within the c a l f veins*
Flow (Visual analogue scale)
Calf veins
Posterior tibial veins (PT) Common peroneal veins (CP) Anterior tibial veins (AT)
Supine
Erect
Supine/bands
Erect~bands
91±8 85± 18 91±9
93 + 10 85±22 92+ 12
87± 16 77+23 85± 16
83 ± 19 75±22 81±18
Supine to supine/bands: Supine to erect/bands: Erect to supine/bands: Erect to erect/bands: Supine to erect/bands: Erect to erect/bands:
PT, CP, AT PT, CP PT, CP, AT CP AT PT, AT
~p CP
•p < 0.05 in all 4 positions
* Mean values ± 1 standard deviation• Table 2 - The effect o f posture and above knee bands on c a l f vein diameter*
Calf veins
Venous diameter (mm)
Posterior tibial veins (PT) Common peroneal veins (CP) Anterior tibial veins (AT)
Supine
Erect
Supine~bands
Erect~bands
3.4±1.3 3.6±1.1 3.4±1.2
4.6±1.2 4.5±1.2 3.7±1.3
4.3±1.2 4.5±1.3 3.6±1.1
4.7±1.3 4.8±1.2 3.8±1.7
Supine to erect: CP Supine to supine/bands: PT
pAT} p
Calf Vein Anatomy and Flow: Implications for Colour Doppler Imaging G. M. B A X T E R and P. D U F F Y
Department of Radiology, Southern General Hospital, Glasgow Early experience has suggested that colour flow Doppler ultrasound may have a diagnostic role in calf vein thrombosis. Before its accuracy within the calf can be adequately assessed, normal calf vein flow and anatomy needs to be understood. We, therefore, studied 40 normal volunteers, age range 24-75 years (mean 45.4), M: F 22:18, and assessed both flow and venous diameter in each of the three sets of calf veins in the supine and erect positions and once again in both these positions following the application of an above knee band. Paired sets of veins were present in all posterior tibial and common peroneal sets, but in only 85% of the anterior tibial group. Significant flow variations were present between different sets of veins, there being relatively less appreciable flow within the common peroneal (p < 0.05). Both band application and erect posture produced significant increases in venous diameter (p < 0.01, p < 0.001) in the posterior tibial and common peroneal veins, aiding visualization but at the cost of reducing flow following band application (p < 0.05, p < 0.01). The erect posture had no deleterious effect on calf vein flow. We, therefore, recommend that when the patency of calf veins is being assessed scanning should be performed in both a supine and erect position as this will help vein visualization without a reduction in flow, and thus avoid misinterpretation. Baxter, (3. M. & Duffy, P. (1992). Clinical Radiology 46, 84-87. Calf Vein Anatomy and Flow: Implications for Colour Doppler Imaging
Accepted for Publication 9 March 1992
Venography has for many years been accepted as the 'gold standard' imaging modality in the diagnosis of lower limb venous thrombosis. Although it is undoubtedly an accurate investigative method it does have potential problems which include failure of cannulation, contrast reaction and even the induction of thrombosis, admittedly the latter complications being less frequent following the introduction of the low osmolar, non-ionic contrast agents [1]. As a consequence of these potential disadvantages, there has been a search for a suitable noninvasive alternative which has included impedance plethysmography, thermography and radioisotope imaging. All of these techniques have shown a lack of sensitivity and/or specificity with wide interstudy variation questioning the reproducibility of these techniques [2 6]. Real time ultrasound in isolation, or with the addition of duplex Doppler, has been shown to be accurate in the diagnosis of lower limb venous occlusive disease in the femoral and popliteal segments with a sensitivity approaching 90% [7-9]. With the introduction of colour Doppler technology more information, i.e. differentiation between occlusive or non-occlusive thrombus and detection of collateral circulation, is available noninvasively without prolonging examination time. Early work in this field has also indicated it may have a role in the diagnosis of calf vein thrombosis [10,11]. In view of this, and based on early encouraging work, we decided to study calf vein thrombosis in more depth. Prior to any clinical trial we felt it was necessary to scan the calf veins of 40 'normal' subjects in order to determine the number of paired veins routinely visualized by colour Doppler ultrasound, identify the best position for doing so, and thus define an optimal technique for routine scanning of these vessels. Correspondence to: Dr G. M. Baxter, Senior Registrar, Department of Radiology, Western Infirmary, Glasgow G11 5NT.
METHOD Forty normal healthy volunteers M : F 22 : 18, age range 24 75 years (mean age 45.4) had a cotour Doppler ultrasound scan of their calf veins. A wide age range was used to reflect accurately the age distribution of patients who may present with deep venous thrombosis. Exclusion criteria included a previous history of lower limb trauma, prolonged bed rest or hospitalization or a prior history or treatment for deep venous thrombosis. O f the 40 patients, the right leg was scanned in 21 cases and the left in 19. Beginning in the supine position patients were scanned using either a 5 or 7.5 M H z linear array probe (Acuson 128). In order to ensure that comparisons between calf veins were made at the same reference point, a defined point exactly mid-way between the medial and lateral malleoli and the tibial tuberosity was marked with a pen, the main field of view being restricted to a distance of 3cm above or below this midpoint, also marked on the leg. Following distal compression the number of veins accompanying each of the three major calf arteries were noted, this information being recorded on video tape. This technique was then repeated with the leg hanging over the side of the bed in an erect posture with the foot resting on a stool. Further assessment was then made in both the supine and erect position with the addition of a tightly applied above knee band, in a manner analogous to venography. The number of veins accompanying each artery were noted. An assessment of venous flow was made by two separate radiologists experienced in colour Doppler ultrasound, at completion of the trial, directly from video tape. This was done using a visual analogue scale to try and determine the best position for visualizing flow within each set of veins. The visual analogue scale is an arbitrary scale from 0 to 100: zero represented complete absence of
85
CALF VEIN ANATOMY AND FLOW Table 1 - The effect o f posture and above knee bands on flow rate within the c a l f veins*
Flow (Visual analogue scale)
Calf veins
Posterior tibial veins (PT) Common peroneal veins (CP) Anterior tibial veins (AT)
Supine
Erect
Supine/bands
Erect~bands
91±8 85± 18 91±9
93 + 10 85±22 92+ 12
87± 16 77+23 85± 16
83 ± 19 75±22 81±18
Supine to supine/bands: Supine to erect/bands: Erect to supine/bands: Erect to erect/bands: Supine to erect/bands: Erect to erect/bands:
PT, CP, AT PT, CP PT, CP, AT CP AT PT, AT
~p CP
•p < 0.05 in all 4 positions
* Mean values ± 1 standard deviation• Table 2 - The effect o f posture and above knee bands on c a l f vein diameter*
Calf veins
Venous diameter (mm)
Posterior tibial veins (PT) Common peroneal veins (CP) Anterior tibial veins (AT)
Supine
Erect
Supine~bands
Erect~bands
3.4±1.3 3.6±1.1 3.4±1.2
4.6±1.2 4.5±1.2 3.7±1.3
4.3±1.2 4.5±1.3 3.6±1.1
4.7±1.3 4.8±1.2 3.8±1.7
Supine to erect: CP Supine to supine/bands: PT
pAT} p
