1991, The British Journal of Radiology, 64, 485-488
Duplex sonography in splenomegaly By * L Jarvis, FRCR, tP. G. Cook, FRCR, *tC. M. James, MRCP, MRCPath, t M . Rose, MB, BS tA. G. Prentice, FRCP, MRCPath and P. A. Dubbins, FRCR Departments of Diagnostic Ultrasound and tClinical Haematology, Plymouth Group Hospitals, Plymouth, UK {Received August 1990 and in revised form September 1990) Keywords: Doppler ultrasound, Spleen, Splenomegaly
Abstract. The aetiology of splenomegaly is seldom clear from either clinical or imaging assessment of the spleen. In the majority of cases sonographic assessment of the spleen produces a homogeneous enlargement of variable echodensity, but with very poor correlation with pathology. A study has been undertaken to assess the Doppler characteristics of the splenic artery in splenomegaly, excluding cases of portal hypertension in an attempt to provide further diagnostic information. Duplex assessment of 18 normal subjects and 10 patients with splenomegaly due to five different causes was undertaken. Analysis of waveform, peak frequency and pulsatility index were compared and failed to demonstrate any significant change. In the normal subject there is a broad systolic spectrum related to the tortuosity of the splenic artery, with persistence of forward flow throughout diastole, a reflection of the low peripheral resistance of the spleen. In splenomegaly the broad systolic spectrum is unchanged, since vessel tortuosity persists. Pathological and physiological assessment of the spleen in splenomegaly shows that a low resistance circulation persists, explaining maintenance of the diastolic flow pattern in splenomegaly. Increased blood flow to the spleen in splenomegaly occurs either as a result of an increase in vessel diameter or an increase in flow velocity, or a variable combination of the two which does not seem to be governed by specific pathology. An increase in peak frequency in some cases reflected some increase in flow velocity but provided no useful correlation. Analysis of the pulsatility index supported the above findings without adding further information.
Real-time ultrasound is now an established technique for the investigation of the intra-abdomina) organs. The spleen is well seen in the majority of cases and the sonographic appearance of the normal spleen (Niederau et al, 1983) and the diseased spleen (Mittelstaedt & Partain, 1980; Kane & Katz, 1982; King et al, 1985) have been described. The clinical assessment of splenomegaly is non-specific, and in many cases sonographic assessment of the spleen gives no further clues to the cause of a diffusely enlarged spleen. The whole range of haemopoietic and myeloproliferative disorders producing splenomegaly may give identical appearances on ultrasound. Developments in pulsed Doppler equipment have now made it possible to obtain non-invasive assessments of blood flow in major intra-abdominal vessels (Atkinson & Wells, 1977; Taylor et al, 1978; Gill, 1979) and characteristic time-velocity spectra for these vessels have been described (Taylor et al, 1985; Taylor & Burns, 1985). The blood flow through the spleen increases up to ten-fold in splenomegaly, with a consequent increase in flow through the splenic artery and vein and hepatic portal vein. The splenic vein and hepatic portal vein Address for reprint requests to: Surgeon Commander L. J. Jarvis, RN, Department of Radiology, Royal Naval Hospital, Haslar, Gosport, Hampshire PO12 2AA, UK. *Present address: Royal Naval Hospital, Haslar, Gosport, Hampshire, UK. ^Present address: Royal Cornwall Hospital, Truro, Cornwall, UK. Vol. 64, No. 762
have been assessed by duplex ultrasound in cases of portal
hypertension
(Zoli
et al,
1986; Ohnishi et aJ,
1985), but only in cases of chronic liver disease. The purpose of this study is to assess the splenic artery and vein and the hepatic portal vein in patients with established splenomegaly, using duplex Doppler ultrasound to assess whether the time-velocity spectrum improves specificity of diagnosis. Method A prospective study was performed on 19 normal volunteers and 10 patients with known splenomegaly. The volunteers were all normal subjects, mostly members of staff" of the Department of Diagnostic Radiology, aged from 20 to 79 years. Patients with splenomegaly were referred from the Department of Clinical Haematology, having been fully investigated with the cause of their disease established. Patients with splenomegaly and portal hypertension secondary to liver disease were excluded from the study. All subjects gave informed consent to the procedure. Subjects were prepared as for a standard upper abdominal ultrasound examination. The upper abdomen was imaged using the Advanced Technology Laboratories Ultrasound Imager with the Advanced Technology Laboratories Pulsed Doppler Flow Analyser and 3.5 MHz or 5 MHz real-time sector transducers. In each case the spleen was imaged and the maximum length was measured. The splenic artery and vein and hepatic portal vein were imaged and the presence of variceal 485
L. Jarvis et al
Figure 1. (a) Longitudinal/oblique ultrasound image to the left upper quadrant, showing Doppler sampling from the splenic artery at the splenic hilum (arrow) (s = spleen), (b) Doppler spectral sonogram derived from the splenic artery at this site. The splenic bed is a low-resistance arterial system with continuous forward flow in diastole resulting in a relatively low pulsatility index. There is a wide spread of flow velocities in both systole and diastole, presumably as a result of flow disturbance in a tortuous vessel.
vessels was sought. The liver was assessed in an attempt to exclude primary hepatic pathology. For duplex assessment of the splenic artery, the vessel was located on the real-time image at a point close to its origin from the coeliac axis, and again close to the splenic hilum. A cursor corresponding to the position of the sample to be assessed was moved into the area and the sample volume adjusted to encompass the width of the vessel. The angle between the axis of the ultrasound beam and the long axis of the vessel was adjusted to optimize Doppler signal. Duplex assessment of the hepatic portal vein at the porta hepatis was performed using a similar method. For each patient the pulsatility index for the splenic artery Doppler waveform was calculated using the formula used by Gosling (Gosling & King, 1974). Results
Spleen size and echo-pattern The range of spleen size in the normal volunteers was within normal limits in all cases, i.e. an overall length of
less than 11 cm with a homogeneous weakly echogenic reflectivity of similar density to the liver. The range of spleen sizes in the patients is given in Table I; in all cases there was a homogeneous echo pattern, without focal defects. Doppler results Normal subjects (Fig. 1). The spectral analysis of the splenic artery was similar in all subjects studied. There was a broad systolic spectrum, indicating multiple flow velocities within the vessel, which is probably related to the normal tortuosity of the splenic artery. The peak systolic frequency reached a maximum of 3.5 kHz. There was persistence of forward flow throughout diastole, which is a consequence of the low peripheral resistance in the spleen. Pulsatility indices were calculated for the normal subjects with a mean of 0.799, standard deviation 0.153. The normal portal veins demonstrated continuous flow throughout the cardiac cycle, directed towards the liver, with variation in flow related to respiratory movement.
Table I. Doppler waveform peak frequency and pulsatility indices related to pathology in splenomegaly Diagnosis /3-thalassaemia Chronic myeloid chemotherapy Chronic myeloid Chronic myeloid Chronic myeloid Lymphoma—on Lymphoma Myelofibrosis Myelodysplasia
486
leukaemia—on leukaemia leukaemia leukaemia chemotherapy
Age
Spleen size (cm)
Peak frequency splenic artery
Splenic artery diameter
Pulsatility index
17 51
21.7 12.0
4.5 3.5
0.6 0.3
0.56 0.63
77 60 59 61 73 72 68
21.4 16.3 19.0 29.3 23.5 21.3 31.2
3.5 5.0 7.0 4.5 6.0 5.0 4.0
0.8 0.3 1.4 1.4 0.9 0.7 1.1
0.71 0.81 0.93 0.93 1.06 1.02 1.09
The British Journal of Radiology, June 1991
Duplex sonography in splenomegaly
Figure 2. Spectral sonogram of the splenic artery at the splenic hilum in a 72-year-old woman with splenomegaly due to myelofibrosis. The flow pattern demonstrated is similar to that in a normal patient.
Figure 3. Spectral sonogram of the splenic artery in a 59-yearold woman with chronic myeloid leukaemia. Although there is an overall increase in flow velocities, the pulsability index does not differ significantly from the normal range.
Patients (Figs 2 and 3). Studies of the splenic vein and hepatic portal vein demonstrated flow directed towards the liver in all cases, with preservation of a slight variation in frequency, related to respiration. For the splenic artery, the spectral pattern in all 10 subjects with splenomegaly was similar to that seen in the normal subjects, with the characteristic broad spectrum in systole and continued forward flow in diastole; there was an increase in peak frequency in some but not all cases (Table I). The peak frequency did not bear any direct relationship to the size of the spleen—the largest spleen measured had a peak frequency of 4 kHz. The size of the splenic artery increased in proportion to the size of the spleen. Pulsatility indices calculated for the patients with splenomegaly are shown in Table I. These values fall within 95% confidence limits for the indices calculated in normal subjects and are therefore considered to be statistically the same as the normal group.
splenic blood flow represents about 5% of total blood volume per minute. With increasing splenomegaly the minute volume of the spleen is increased, but the irrigation coefficient, i.e. the blood flow per gram of splenic tissue, is unchanged or may even be reduced (Veda & Kitani, 1970). Blood is brought to the spleen via the splenic artery and then through its branches, the trabecular arteries, into the central arteries sited in the white pulp. Circulation to the venous side is either directly through the sinuses and then via the collecting veins to the trabecular vein ("closed system"), or the blood passes into the cord spaces before joining up with the sinuses ("open system"). Because of the presence in the spleen of these two vascular systems there is both a rapid and a slow transit component in the splenic circulation. Both the vascular systems provide low resistance to the splenic arterial blood supply. The spectral patterns in the splenic arteries in this study of patients with splenomegaly show no change from the normal. The broad spectrum remains, with continued forward flow in diastole, indicative of the turbulence in the splenic artery related to tortuosity of the vessel, and this would not be expected to alter. The diastolic component reflects a low-resistance organ, and again this finding corresponds to the state of the pathological splenic circulation described above. An increase in peak frequency in some cases may be a reflection of increased flow velocity through the vessel in these cases. However, in many cases increased size of the spleen was associated with increased diameter of the splenic artery. Although the volume of blood travelling to the spleen might be expected to increase in proportion to the size of the spleen, this volume increase appears to occur either predominantly as a result of increase in vessel diameter or increase in flow velocity, or a variable combination of the two that does not appear to be governed by specific pathology.
Discussion
The poor correlation between splenic pathology and specific sonographic appearances provides persistent difficulty in clinical diagnosis. There may be some correlation with certain disease states, depending on the echodensity of the spleen and the presence or absence of focal defects (Mittelstaedt & Partain, 1980). However, in the large majority of patients with a homogeneously enlarged spleen a specific diagnosis cannot be made. In splenomegaly the amount of blood flowing through the spleen and its flow rate may increase by five- to ten-fold and at the same time a certain proportion of the blood may be pooled in the cord spaces. Increased red cell pool is especially a feature of myeloproliferative and lymphoproliferative disorders. The normal red cell content of the spleen is 20-60 ml, or less than 5% of the red cell mass (Hegde et al, 1973), and the Vol. 64, No. 762
487
L. Jarvis el al
The pulsatility index has been developed to provide an index of the pulsatility of the maximum frequency waveform, whilst remaining independent of probe-vessel angle (Woodcock et al, 1972). This is important in evaluating the splenic artery. The course of the vessel is extremely tortuous, and accurate measurements of the angle of incidence of a Doppler beam are very difficult. Accurate measurement of velocity and volume offlowis therefore not currently realistic. However, calculation of the pulsatility indices in both normal subjects and patients with splenomegaly has demonstrated no significant difference between the two groups. The spread of pulsatility index in both groups is wide, and while there is evidence from peak velocity measurements and from assessment of vessel size of increase in blood flow in splenomegaly, there are no features specific for a particular disease process. In conclusion, the addition of pulsed Doppler analysis has failed to add any useful information to sonographic assessment of the spleen. Subjective interpretation of the spectral pattern in addition to calculation of pulsatility indices has shown no significant difference between normal subjects and patients with splenomegaly, although increase in volume flow is demonstrable in most cases. Patients have not been assessed progressively during therapy, and this remains an area where alteration in flow velocity may be found to indicate a response to treatment. References ATKINSON,
P.
&
WELLS,
P. N. T.,
1977.
Pulse-Doppler
ultrasound and its clinical application. Yale Journal of Biology in Medicine, 50, 367-373. GILL, R. W., 1979. Pulsed Doppler with B-mode imaging for quantitative blood flow measurement. Ultrasound in Medicine and Biology, 5, 223-235. GOSLING, R. G. & KING, D. H., J974. ArteriaJ assessment by Doppler shift ultrasound. Proceedings of the Royal Society of Medicine, 67(b), 447-449.
HEGDE, U. M ,
WILLIAMS, E. D., LEWIS, S. M., SZUR, L.,
GLASS, H. I. & PETTIT, J. E., 1973. Measurement of splenic
red cell volume and visualization of the spleen with " T c . Journal of Nuclear Medicine, 14, 769-771. KANE,
R. A.
&
KATZ,
S. G.,
1982.
The
spectrum
of
sonographic findings in portal hypertension: a subject review and new observations. Radiology, 142, 453-458. KING, D. M., DAWSON, A. A. & BAYLISS, A. P., 1985. The
value of ultrasonic scanning of the spleen in lymphoma. Clinical Radiology, 36, 473-474. MITTELSTAEDT, C. A. & PARTAIN, C. L., 1980. Ultrasonic-
pathologic classification of splenic abnormalities: grey-scale patterns. Radiology, 134, 697-705. NlEDERAU, C, SONNENBERG, A., MULLER, J. E., ERCKENBRECHT, J. F., SCHOLTEN, T. & FRITSCH, W. P., 1983.
Sonographic measurements of the normal liver, spleen, pancreas and portal vein. Radiology, 149, 537-540. OHNISHI, K., SAITO, M., KOEN, H., NAKAYAMA, T., NOMURA, F.
& OKUDA, K., 1985. Pulsed Doppler flow as a criterion of portal venous velocity: comparison with cineangiographic measurements. Radiology, 154, 495-498. TAYLOR, K. J., ATKINSON, P., D E GRAAFF, C. S., DEMBNER,
A. G. & ROSSENFIELD, A. T., 1978. Clinical evaluation of pulse-Doppler device linked to gray scale B-scan equipment. Radiology, 129, 745-749. TAYLOR, K. J. & BURNS, P. N., 1985. Blood flow in deep abdominal and pelvic vessels: ultrasonic pulsed Doppler analysis. Radiology, 154, 487-493. TAYLOR, K. J., BURNS, P. N., WOODCOCK, J. P. & WELLS,
P. N. T., 1985. Duplex Doppler scanning in the pelvis and abdomen. Ultrasound in Medicine in Biology, 11, 643-658. VEDA, H. & KITANI, K., 1970. Splenic blood flow in idiopathic portal hypertension in Japan measured by 85Kr clearance method. Ada Hepato-splenologica, 18, 28-40. WOODCOCK, J. P., GOSLING, R. G. & FITZGERALD, D. E., 1972.
A new non-invasive technique for assessment of superficial femoral artery obstruction. British Journal of Surgery, 59, 226-231. ZOLI, M., MARCHESINI, G., CORDIANI, M. R., PISI, P., BRUNORI,
A., TRONO, A. & PISI, E., 1986. Echo-Doppler
measurement
of splanchnic blood flow in control and cirrhotic subjects. Journal of Clinical Ultrasound, 14, 429-435.
The British Journal of Radiology, June 1991
i
Duplex sonography in splenomegaly By * L Jarvis, FRCR, tP. G. Cook, FRCR, *tC. M. James, MRCP, MRCPath, t M . Rose, MB, BS tA. G. Prentice, FRCP, MRCPath and P. A. Dubbins, FRCR Departments of Diagnostic Ultrasound and tClinical Haematology, Plymouth Group Hospitals, Plymouth, UK {Received August 1990 and in revised form September 1990) Keywords: Doppler ultrasound, Spleen, Splenomegaly
Abstract. The aetiology of splenomegaly is seldom clear from either clinical or imaging assessment of the spleen. In the majority of cases sonographic assessment of the spleen produces a homogeneous enlargement of variable echodensity, but with very poor correlation with pathology. A study has been undertaken to assess the Doppler characteristics of the splenic artery in splenomegaly, excluding cases of portal hypertension in an attempt to provide further diagnostic information. Duplex assessment of 18 normal subjects and 10 patients with splenomegaly due to five different causes was undertaken. Analysis of waveform, peak frequency and pulsatility index were compared and failed to demonstrate any significant change. In the normal subject there is a broad systolic spectrum related to the tortuosity of the splenic artery, with persistence of forward flow throughout diastole, a reflection of the low peripheral resistance of the spleen. In splenomegaly the broad systolic spectrum is unchanged, since vessel tortuosity persists. Pathological and physiological assessment of the spleen in splenomegaly shows that a low resistance circulation persists, explaining maintenance of the diastolic flow pattern in splenomegaly. Increased blood flow to the spleen in splenomegaly occurs either as a result of an increase in vessel diameter or an increase in flow velocity, or a variable combination of the two which does not seem to be governed by specific pathology. An increase in peak frequency in some cases reflected some increase in flow velocity but provided no useful correlation. Analysis of the pulsatility index supported the above findings without adding further information.
Real-time ultrasound is now an established technique for the investigation of the intra-abdomina) organs. The spleen is well seen in the majority of cases and the sonographic appearance of the normal spleen (Niederau et al, 1983) and the diseased spleen (Mittelstaedt & Partain, 1980; Kane & Katz, 1982; King et al, 1985) have been described. The clinical assessment of splenomegaly is non-specific, and in many cases sonographic assessment of the spleen gives no further clues to the cause of a diffusely enlarged spleen. The whole range of haemopoietic and myeloproliferative disorders producing splenomegaly may give identical appearances on ultrasound. Developments in pulsed Doppler equipment have now made it possible to obtain non-invasive assessments of blood flow in major intra-abdominal vessels (Atkinson & Wells, 1977; Taylor et al, 1978; Gill, 1979) and characteristic time-velocity spectra for these vessels have been described (Taylor et al, 1985; Taylor & Burns, 1985). The blood flow through the spleen increases up to ten-fold in splenomegaly, with a consequent increase in flow through the splenic artery and vein and hepatic portal vein. The splenic vein and hepatic portal vein Address for reprint requests to: Surgeon Commander L. J. Jarvis, RN, Department of Radiology, Royal Naval Hospital, Haslar, Gosport, Hampshire PO12 2AA, UK. *Present address: Royal Naval Hospital, Haslar, Gosport, Hampshire, UK. ^Present address: Royal Cornwall Hospital, Truro, Cornwall, UK. Vol. 64, No. 762
have been assessed by duplex ultrasound in cases of portal
hypertension
(Zoli
et al,
1986; Ohnishi et aJ,
1985), but only in cases of chronic liver disease. The purpose of this study is to assess the splenic artery and vein and the hepatic portal vein in patients with established splenomegaly, using duplex Doppler ultrasound to assess whether the time-velocity spectrum improves specificity of diagnosis. Method A prospective study was performed on 19 normal volunteers and 10 patients with known splenomegaly. The volunteers were all normal subjects, mostly members of staff" of the Department of Diagnostic Radiology, aged from 20 to 79 years. Patients with splenomegaly were referred from the Department of Clinical Haematology, having been fully investigated with the cause of their disease established. Patients with splenomegaly and portal hypertension secondary to liver disease were excluded from the study. All subjects gave informed consent to the procedure. Subjects were prepared as for a standard upper abdominal ultrasound examination. The upper abdomen was imaged using the Advanced Technology Laboratories Ultrasound Imager with the Advanced Technology Laboratories Pulsed Doppler Flow Analyser and 3.5 MHz or 5 MHz real-time sector transducers. In each case the spleen was imaged and the maximum length was measured. The splenic artery and vein and hepatic portal vein were imaged and the presence of variceal 485
L. Jarvis et al
Figure 1. (a) Longitudinal/oblique ultrasound image to the left upper quadrant, showing Doppler sampling from the splenic artery at the splenic hilum (arrow) (s = spleen), (b) Doppler spectral sonogram derived from the splenic artery at this site. The splenic bed is a low-resistance arterial system with continuous forward flow in diastole resulting in a relatively low pulsatility index. There is a wide spread of flow velocities in both systole and diastole, presumably as a result of flow disturbance in a tortuous vessel.
vessels was sought. The liver was assessed in an attempt to exclude primary hepatic pathology. For duplex assessment of the splenic artery, the vessel was located on the real-time image at a point close to its origin from the coeliac axis, and again close to the splenic hilum. A cursor corresponding to the position of the sample to be assessed was moved into the area and the sample volume adjusted to encompass the width of the vessel. The angle between the axis of the ultrasound beam and the long axis of the vessel was adjusted to optimize Doppler signal. Duplex assessment of the hepatic portal vein at the porta hepatis was performed using a similar method. For each patient the pulsatility index for the splenic artery Doppler waveform was calculated using the formula used by Gosling (Gosling & King, 1974). Results
Spleen size and echo-pattern The range of spleen size in the normal volunteers was within normal limits in all cases, i.e. an overall length of
less than 11 cm with a homogeneous weakly echogenic reflectivity of similar density to the liver. The range of spleen sizes in the patients is given in Table I; in all cases there was a homogeneous echo pattern, without focal defects. Doppler results Normal subjects (Fig. 1). The spectral analysis of the splenic artery was similar in all subjects studied. There was a broad systolic spectrum, indicating multiple flow velocities within the vessel, which is probably related to the normal tortuosity of the splenic artery. The peak systolic frequency reached a maximum of 3.5 kHz. There was persistence of forward flow throughout diastole, which is a consequence of the low peripheral resistance in the spleen. Pulsatility indices were calculated for the normal subjects with a mean of 0.799, standard deviation 0.153. The normal portal veins demonstrated continuous flow throughout the cardiac cycle, directed towards the liver, with variation in flow related to respiratory movement.
Table I. Doppler waveform peak frequency and pulsatility indices related to pathology in splenomegaly Diagnosis /3-thalassaemia Chronic myeloid chemotherapy Chronic myeloid Chronic myeloid Chronic myeloid Lymphoma—on Lymphoma Myelofibrosis Myelodysplasia
486
leukaemia—on leukaemia leukaemia leukaemia chemotherapy
Age
Spleen size (cm)
Peak frequency splenic artery
Splenic artery diameter
Pulsatility index
17 51
21.7 12.0
4.5 3.5
0.6 0.3
0.56 0.63
77 60 59 61 73 72 68
21.4 16.3 19.0 29.3 23.5 21.3 31.2
3.5 5.0 7.0 4.5 6.0 5.0 4.0
0.8 0.3 1.4 1.4 0.9 0.7 1.1
0.71 0.81 0.93 0.93 1.06 1.02 1.09
The British Journal of Radiology, June 1991
Duplex sonography in splenomegaly
Figure 2. Spectral sonogram of the splenic artery at the splenic hilum in a 72-year-old woman with splenomegaly due to myelofibrosis. The flow pattern demonstrated is similar to that in a normal patient.
Figure 3. Spectral sonogram of the splenic artery in a 59-yearold woman with chronic myeloid leukaemia. Although there is an overall increase in flow velocities, the pulsability index does not differ significantly from the normal range.
Patients (Figs 2 and 3). Studies of the splenic vein and hepatic portal vein demonstrated flow directed towards the liver in all cases, with preservation of a slight variation in frequency, related to respiration. For the splenic artery, the spectral pattern in all 10 subjects with splenomegaly was similar to that seen in the normal subjects, with the characteristic broad spectrum in systole and continued forward flow in diastole; there was an increase in peak frequency in some but not all cases (Table I). The peak frequency did not bear any direct relationship to the size of the spleen—the largest spleen measured had a peak frequency of 4 kHz. The size of the splenic artery increased in proportion to the size of the spleen. Pulsatility indices calculated for the patients with splenomegaly are shown in Table I. These values fall within 95% confidence limits for the indices calculated in normal subjects and are therefore considered to be statistically the same as the normal group.
splenic blood flow represents about 5% of total blood volume per minute. With increasing splenomegaly the minute volume of the spleen is increased, but the irrigation coefficient, i.e. the blood flow per gram of splenic tissue, is unchanged or may even be reduced (Veda & Kitani, 1970). Blood is brought to the spleen via the splenic artery and then through its branches, the trabecular arteries, into the central arteries sited in the white pulp. Circulation to the venous side is either directly through the sinuses and then via the collecting veins to the trabecular vein ("closed system"), or the blood passes into the cord spaces before joining up with the sinuses ("open system"). Because of the presence in the spleen of these two vascular systems there is both a rapid and a slow transit component in the splenic circulation. Both the vascular systems provide low resistance to the splenic arterial blood supply. The spectral patterns in the splenic arteries in this study of patients with splenomegaly show no change from the normal. The broad spectrum remains, with continued forward flow in diastole, indicative of the turbulence in the splenic artery related to tortuosity of the vessel, and this would not be expected to alter. The diastolic component reflects a low-resistance organ, and again this finding corresponds to the state of the pathological splenic circulation described above. An increase in peak frequency in some cases may be a reflection of increased flow velocity through the vessel in these cases. However, in many cases increased size of the spleen was associated with increased diameter of the splenic artery. Although the volume of blood travelling to the spleen might be expected to increase in proportion to the size of the spleen, this volume increase appears to occur either predominantly as a result of increase in vessel diameter or increase in flow velocity, or a variable combination of the two that does not appear to be governed by specific pathology.
Discussion
The poor correlation between splenic pathology and specific sonographic appearances provides persistent difficulty in clinical diagnosis. There may be some correlation with certain disease states, depending on the echodensity of the spleen and the presence or absence of focal defects (Mittelstaedt & Partain, 1980). However, in the large majority of patients with a homogeneously enlarged spleen a specific diagnosis cannot be made. In splenomegaly the amount of blood flowing through the spleen and its flow rate may increase by five- to ten-fold and at the same time a certain proportion of the blood may be pooled in the cord spaces. Increased red cell pool is especially a feature of myeloproliferative and lymphoproliferative disorders. The normal red cell content of the spleen is 20-60 ml, or less than 5% of the red cell mass (Hegde et al, 1973), and the Vol. 64, No. 762
487
L. Jarvis el al
The pulsatility index has been developed to provide an index of the pulsatility of the maximum frequency waveform, whilst remaining independent of probe-vessel angle (Woodcock et al, 1972). This is important in evaluating the splenic artery. The course of the vessel is extremely tortuous, and accurate measurements of the angle of incidence of a Doppler beam are very difficult. Accurate measurement of velocity and volume offlowis therefore not currently realistic. However, calculation of the pulsatility indices in both normal subjects and patients with splenomegaly has demonstrated no significant difference between the two groups. The spread of pulsatility index in both groups is wide, and while there is evidence from peak velocity measurements and from assessment of vessel size of increase in blood flow in splenomegaly, there are no features specific for a particular disease process. In conclusion, the addition of pulsed Doppler analysis has failed to add any useful information to sonographic assessment of the spleen. Subjective interpretation of the spectral pattern in addition to calculation of pulsatility indices has shown no significant difference between normal subjects and patients with splenomegaly, although increase in volume flow is demonstrable in most cases. Patients have not been assessed progressively during therapy, and this remains an area where alteration in flow velocity may be found to indicate a response to treatment. References ATKINSON,
P.
&
WELLS,
P. N. T.,
1977.
Pulse-Doppler
ultrasound and its clinical application. Yale Journal of Biology in Medicine, 50, 367-373. GILL, R. W., 1979. Pulsed Doppler with B-mode imaging for quantitative blood flow measurement. Ultrasound in Medicine and Biology, 5, 223-235. GOSLING, R. G. & KING, D. H., J974. ArteriaJ assessment by Doppler shift ultrasound. Proceedings of the Royal Society of Medicine, 67(b), 447-449.
HEGDE, U. M ,
WILLIAMS, E. D., LEWIS, S. M., SZUR, L.,
GLASS, H. I. & PETTIT, J. E., 1973. Measurement of splenic
red cell volume and visualization of the spleen with " T c . Journal of Nuclear Medicine, 14, 769-771. KANE,
R. A.
&
KATZ,
S. G.,
1982.
The
spectrum
of
sonographic findings in portal hypertension: a subject review and new observations. Radiology, 142, 453-458. KING, D. M., DAWSON, A. A. & BAYLISS, A. P., 1985. The
value of ultrasonic scanning of the spleen in lymphoma. Clinical Radiology, 36, 473-474. MITTELSTAEDT, C. A. & PARTAIN, C. L., 1980. Ultrasonic-
pathologic classification of splenic abnormalities: grey-scale patterns. Radiology, 134, 697-705. NlEDERAU, C, SONNENBERG, A., MULLER, J. E., ERCKENBRECHT, J. F., SCHOLTEN, T. & FRITSCH, W. P., 1983.
Sonographic measurements of the normal liver, spleen, pancreas and portal vein. Radiology, 149, 537-540. OHNISHI, K., SAITO, M., KOEN, H., NAKAYAMA, T., NOMURA, F.
& OKUDA, K., 1985. Pulsed Doppler flow as a criterion of portal venous velocity: comparison with cineangiographic measurements. Radiology, 154, 495-498. TAYLOR, K. J., ATKINSON, P., D E GRAAFF, C. S., DEMBNER,
A. G. & ROSSENFIELD, A. T., 1978. Clinical evaluation of pulse-Doppler device linked to gray scale B-scan equipment. Radiology, 129, 745-749. TAYLOR, K. J. & BURNS, P. N., 1985. Blood flow in deep abdominal and pelvic vessels: ultrasonic pulsed Doppler analysis. Radiology, 154, 487-493. TAYLOR, K. J., BURNS, P. N., WOODCOCK, J. P. & WELLS,
P. N. T., 1985. Duplex Doppler scanning in the pelvis and abdomen. Ultrasound in Medicine in Biology, 11, 643-658. VEDA, H. & KITANI, K., 1970. Splenic blood flow in idiopathic portal hypertension in Japan measured by 85Kr clearance method. Ada Hepato-splenologica, 18, 28-40. WOODCOCK, J. P., GOSLING, R. G. & FITZGERALD, D. E., 1972.
A new non-invasive technique for assessment of superficial femoral artery obstruction. British Journal of Surgery, 59, 226-231. ZOLI, M., MARCHESINI, G., CORDIANI, M. R., PISI, P., BRUNORI,
A., TRONO, A. & PISI, E., 1986. Echo-Doppler
measurement
of splanchnic blood flow in control and cirrhotic subjects. Journal of Clinical Ultrasound, 14, 429-435.
The British Journal of Radiology, June 1991
i
![[Color-coded duplex sonography (angiodynography)].](/assets/img/hold.png)
