vii. general discussion and conclusions
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VII. GENERAL DISCUSSION AND CONCLUSIONS
Localization and distribution of recent thrombosis and thrombus remnants
The localization and distribution of recent thrombosis and of thrombus rem- nants have been presented in the results and are mainly related to autopsy find- ings and will not be discussed closely here. The results concerning thrombi in valve pockets are also based mainly on autopsy observations and have been presented in a separate paper (DIENER, ERICSSON & LUND 1969).
RELIABILITY
Thrombus or clot
One of the purposes of the present investigation has been to demonstrate the possibilities to distinguish between thrombus and clot in the deep venous system of the legs by means of postmortem phlebography. This has also been found to be possible in the vast majority of cases. As opposed to thrombi, clots usually are “drowned” in, displaced and deformed by, the contrast medium.
As mentioned under failures, a fourth of the false positive findings concerned clots. Difficulty to distinguish between thrombus and clot phlebographically caused less than a third of the total number of failures.
The question, thrombus or clot, has therefore not been shown to be the main problem in differential diagnosis.
Distal extension of thrombus
By occluding thrombosis the distal limit is difficult to determine phlebogra- phically. In some cases a contrast filling of a vessel distal to an occluding thrombus could not be obtained. This occurred in spite of the fact that the vessel distal to the occlusion was shown to contain liquified blood and to be completely free of thrombus and clots at dissection. The contrast medium had not been able to displace the blood which apparently had no possibility to flow into the muscular veins or proximally. The captured blood column had in this way
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resulted in a contrast defect which could be misinterpreted as being caused by a thrombus within the region.
Most of the cases of false positive findings of this type concerned the deep veins of the lower leg, especially the anterior tibial veins. Examples of this were the 10 lower legs presented under false positive findings which did not have any thrombus. Here the reason for the absence of filling of the deep veins of the lower leg was - phlebographically correctly diagnosed - thrombus in the popliteal vein. The extension of the thrombus distally was overestimated in these cases. This shows a certain limitation of the method. It does not limit its essential goal of use, which is to decide if there is a thrombus or not.
Very small thrombi - especially in valve pockets
Very small thrombi, especially those in valve pockets, can be difficult to detect phlebographically. In the bottom of a valve pocket a small amount of liquid blood can remain after contrast medium injection. It can then be difficult or impossible, on films, to determine if the contrast defect does in fact correspond to a thrombus in status nascendi. When the thrombus, anchored in the valve pocket, grows so that it extends out of the valve pocket, it is as a rule easy to recognise (Fig. 18 and 21).
Muscular veins of the lower leg
A special problem is presented by the muscular veins of the lower leg (calf). ARNOLDI (1961) reported that “The muscular veins (soleus veins) are not seen in the normal phlebograms”. COTTON, CLARK & MECH (1965) commented that “it is rare to see muscular veins filled in phlebograms performed in recumbency or the feet-down position”. They also found in arteriography of the lower limbs, where contrast flow-over in the veins was especially followed, “no sign of any filling of muscular veins in the calf”. According to the same authors the usual incomplete filling of the soleus veins should by injection “of radiopaque media at the ankle via the long saphenous and posterior tibial veins” in amputated limbs be caused by “the very efficient valving of muscular veins which prevents reflux”.
In the first 100 cases of the present investigation the contrast medium injection was performed as a routine with the cadavers in horizontal position. In 175 of 199 lower legs (88 per cent) filling of the muscular veins was obtained. The following 300 cases were injected in the feet-down position. Contrast filling of the muscular veins of the calf could in these cases be observed in only 212 (36 per cent) of 596 legs.
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At dissection muscular vein thrombosis was found in 35 lower legs. Muscular vein thrombi could be detected by phlebography in 16 legs and was missed in as many as 19. In 12 (75 per cent) of the lower legs with phlebographically dia- gnosed muscular vein thrombosis a thrombus in the major deep veins was si- multaneously found. Of the 19 lower legs, where muscular vein thrombosis was present but not diagnosed phlebographically, only 4 (21 per cent) had a simultaneous thrombus in the deep venous trunks of the lower leg.
By simultaneous thrombosis of the major deep veins of the lower leg, the chances to detect, phlebographically, a muscular vein thrombus are greater than when a muscular vein thrombus appears isolated. This could partly be connected with the higher pressure of injection needed in the deep venous system when extended thrombi are present in the lower leg. The contrast medium in these cases can be forced into the muscular veins in a retrograde direction. Thereby the possibility to detect thrombi in the muscular veins is increased.
Of the 19 legs in which muscular vein thrombosis was missed 7 had thrombi, correctly diagnosed, in another region of the deep veins. The remaining 12 legs with missed muscular vein thrombosis were distributed over 11 cases. Of these 3 had phlebographically correctly diagnosed thrombi in the other leg and one case had a missed thrombus, in a muscular vein, in the other leg. In 8 cases with muscular vein thrombosis the diagiosis was missed completely concerning the presence of thrombotic disease or not in the deep veins.
The number of phlebographically missed muscular vein thrombi (19) compared with the number diagnosed (12) in investigations with the cadaver in the feet- down position shows the unreliability of the method in the evaluation of presence or absence of thrombi in the muscular veins.
False positive findings have not been observed. A muscular vein thrombosis found radiologically in the lower leg should be a reliable diagnosis. A negative radiological finding, however, cannot be taken as a proof that a muscular vein thrombus is absent.
Deep femoral vein
During ascending phlebography the deep femoral vein fills inconsistently (ROGOFF 8t DEWEESE 1960, BRITTON 1964). This is also true in the postmortem intraosseous examination technique. It is, therefore, impossible to judge with this method if an absence of filling of the deep femoral vein in each case is due to an occluding thrombus or not.
BRITTON (1964) has reported that in ascending phlebography the deep femoral vein “may be filled if the superficial femoral vein is digitally occluded during injection”. In connection with the present investigation 16 legs, by intraosseous
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phlebography with injection in the calcaneus, were shown to be free of throm- bosis in the superficial femoral vein and devoid of contrast medium in the deep femoral vein. Thereafter the superficial femoral vein was ligated just distally to the junction of the common femoral vein. By further contrast medium injection, filling of the deep femoral vein was only achieved in 3 legs. The finding was controlled by follow-up dissection. None of the legs had a thrombus in the deep femoral vein. Even if the number of cases examined in this way is few, it shows that by postmortem intraosseous contrast medium injection in the calcaneus with simultaneous closure of the superficial femoral vein is not a reliable method to achieve filling of the deep femoral vein.
Completely wall adherent band-shaped thrombus remnants
It can be difficult or impossible to demonstrate an old thrombus with post- mortem phlebography. This depends on whether or not the remaining rest of the thrombus is made up of a minute band-formed thickening of the vein wall against the lumen. The band-shaped thrombus remnant can be so flat that it does not appear on the film to narrow the lumen and cannot be distinguished from the vein wall. By dissection, however, the thrombus remnant usually was found as a long brown-black band in the light yellow colored vein wall.
Pulmonary embolism
Investigations of the possibility to diagnose pulmonary infarcts postmortally by means of radiographs without contrast medium injection have been carried out by HAMDTON & CASTLEMAN (1940). The study gave certain information concern- ing the appearance and topography of pulmonary infarcts but was of limited value in the diagnosis of pulmonary embolism. SCHOENMACKERS & VIETEN (1954) used a contrast medium injection directly into the exposed pulmonary artery. Their interest was not particularly focused on pulmonary embolism. SMITH, DAMMIN & DEXTER (1964) injected a contrast medium into the pulmonary artery on removed human lungs. In this way they were also able to diagnose small pul- monary emboli.
The present method with the use of the intracalcaneous route of injection has also been tried for the purpose of diagnosing pulmonary emboli. Such an applica- tion of the method could be of value, especially when a pulmonary embolus is possible and autopsy is denied. In some cases good results have been obtained (Fig. 28). However, the usefulness of the method for assessment of pulmonary embolism is more limited as compared to the applicability in examination of the leg veins. The postmortem diagnosis of presumed pulmonary emboli with the use
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of the present technique appears to be complicated and may even be made im- possible by clots formed postmortally. If such a clot occurs in the right heart, the pulmonary artery or its branches it can be displaced distally by the pressure of the injected contrast medium. In this way the clot can possibly cause a complete luminal occlusion and interruption in the transfer of contrast medium to the corresponding vascular region.
Preliminary observations indicate that postmortem pulmonary arteriography with injection of contrast medium by direct percutaneous puncture without opening of the chest may be more practicable and informative.
APPLICABILITY
The unreliability of the conventional clinical diagnosis of thrombosis has been reported more and more (COON & COLLER 1959, HKGER 1965, BERGVALL 1970 and BROWSE 1970). Phlebography has proved to be necessary.
BORGSTROM et coll. (1965 a, b), by means of phlebography according to the technique of GREITZ (1955), verified that venous thrombi often run a silent course also among surviving patients. Similar observations have been made in other studies (PHILLIPS 1963, HJEL~TEDT & BERGVALL 1968).
In the geriatric clientele presented in this paper there was a large discrepancy between clinically demonstrated and “silent” thrombi. One obtains a completely false impression as to the frequency of thrombotic disease in the elderly if one depends on clinical diagnosis and conventional autopsy exploring only the deep leg veins down to the middle of the thigh.
“Very often restrictions do not permit examination of the extremities” in autopsies performed in the U.S.A. (HAMPTON & CASTLEMAN 1940). Th’ IS was also pointed out by COON & COLLER (1959).
BECKERING & TITUS (1967) have defined the various factors which in the U.S.A. have restricted autopsy evaluation of the vessels of the lower extremities as a possible source of emboli: “restrictions on autopsy examination by relatives; resistance of embalmers to extensive dissections; ambiguity and misunderstanding of the laws of mutilation; and the amount of time required for a venous dissec- tion”. For these reasons and to evaluate more completely the vascular system of the legs, the authors devised a special technique. They utilized, for removal of the femoral and popliteal arteries and veins without external dissection of the thigh or leg, a length of metal tubing sharpened on one end to form a cutting edge. This technique may give some information concerning thrombi in veins. Its applicability is limited, however, to the common and superficial femoral and to the popliteal veins. The findings presented in the actual investigation indicate
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that postmortem intraosseous phlebography yields much more extensive informa- tion than can be obtained with the Beckering and Titus technique.
By postmortem phlebography of the legs it is possible to obtain information concerning venous pathology without dissection. No doubt there is evident limi- tation in accurateness of the method as compared to dissection, although not decisive. On the other side, in some cases changes can be radiologically de- monstrated which are difficult to observe by dissection or might be damaged by it.
Nowadays a lot of clinical work is devoted to problems referring to venous thromboembolism and to the development and improvement of antithrombotic prophylaxis and therapy. This fact constitutes a challenge also to gather more knowledge on the incidence of postmortem venous thrombosis. Remarkably few autopsy studies of this kind have been published suggesting that there are prac- tical problems associated with complete venous dissection of the legs.
Postmortem intraosseous phlebography would seem to offer a possibility of overcoming some of these difficulties, certainly at the same time involving other problems. Time will show if the radiologic method applied as a supplement to ordinary autopsy for examination of the legs, or isolated when autopsy cannot for some reason be performed, can contribute to fill out the abovementioned gap of knowledge.
In this connection it might be added that postmortem phlebography supplies automatically a permanent record i.e. the radiographs accessible for subsequent examination and discussion. The direct method namely dissection of the leg veins requires for detailed preservation of the findings either extensive written reports, drawings or preferably color photographies.
Studies of the combined type performed in the present work thus including not only postmortem phlebography but also dissection may provide some valu- able information from quite a different angle of view i.e. for the interpretation of clinical phlebography. This is mentioned, of course, with at least two reserva- tions: 1) that clinical phlebography deals with streaming blood and postmortem phlebography with standstilling blood; 2) that the used contrast media are non- identical. The fact does remain, however, that by means of comparative post- mortem phlebographies and complete dissections of the leg veins the morpho- logical basis of many phlebographical changes can be systematically assessed and recorded photographically. This may in some respects contribute indirectly to an increased accurateness of the principles applied in evaluation of clinical phle- bography .
Preliminary observations in this study suggest that more extensive angiogra- phic investigations for postmortem diagnostic purposes are feasible since both the inferior and superior caval system as well as the right side of the heart and
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Fig. 29. Pelvis. A round pool of contrast medium is present in the lowest portion of the urinary bladder (cadaver lying on the back). Due to a severe hemorrhagic cystitis, contrast medium has passed through the damaged walls of the veins into the lumen of the bladder.
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Fig. 30. a) Abdomen. Contrast medium in the inferior caval vein as well as in the aorta! The contrast medium had passed through an open foramen ovale from the right to the left atrium and further out into the aorta.
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Fig. 30. b) Gross specimen of the heart showing inside of the right atrium with the persisting foramen ovale ( U ~ Y O W S ) .
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under certain conditions the pulmonary artery also may be observed making possible the diagnosis of pathologic conditions such as tumors, septa1 defects in the heart and in some cases pulmonary emboli (Fig. 29 and 30). However, the possibilities of such extensive phlebography are in fact much more limited than in corresponding studies of solely the lower leg veins.
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