Viktor Szatmári⁺, Gábor Péntek, Ferenc Manczur, Tamás Vrabély, Károly Vörös

+ Szent István Univ., Fac. Vet. Sci., Department and Clinic of Internal Medicine. István u. 2.
   H-1078 Budapest. E-mail: vszatmar@univet.hu
   Present adress: Utrecht Univ., Fac. Vet. Med., Div. Diagnostic Imaging. Yalelaan 10, 3584 CM,
   Utrecht, The Netherlands. E-mail: vszatmar@hotmail.com

Isolated splenic torsion (i.e., without involvement of the stomach) is a rare disease in dogs. Especially large breeds are affected. Ultrasonography is invaluable in the diagnosis of splenic torsion, because the structure and size of the spleen as well as its vasculature can be evaluated at the same time (3, 6). Sonographically, the parenchyma of the enlarged spleen can be normal (mostly in acute cases) or anechoic areas separated by small linear echodensities may be seen in one or more parts of the spleen or in the whole organ (4, 6) (Figure 1). The splenic veins are usually dilated and thrombi may occasionally be identified in them (5, 6). Doppler ultrasonography helps to reveal the lack of blood flow in the splenic veins (3, 5, 6).
In healthy dogs the parenchymal splenic veins can be easily found within the spleen by means of two-dimensional ultrasonography. The adjacent parenchymal arterial branches are much smaller than the veins, therefore colour Doppler technique is needed to visualise them. Both the veins and arteries course through the splenic capsule on the hilar surface of the spleen. Using colour Doppler ultrasound technique, not only the presence, but also the direction of blood flow can be determined in them. Normally, slow unidirectional flow is revealed in the splenic veins directed from the smallest intra-parenchymal branches towards the bigger ones. Eventually the veins break through the capsule and leave the spleen (Figure 2). Normal duplex (or spectral or pulsed-wave) Doppler waveform of the parenchymal splenic veins shows a low velocity flow with or without slight phasic changes (1, 9) (Figure 3).

Case report
A six-year-old male St Bernard (approximately 60 kg) was presented at our clinic with acute onset of abdominal distension and slight depression. In the distended abdomen a large, painful, firm mid-abdominal mass was palpable. The mucous membranes were pink with a capillary refill time of two seconds.
By means of abdominal radiography, gastric dilatation and volvulus syndrome was excluded, since the pylorus was not displaced and only a small amount of gas was present in the stomach, however a large abdominal mass was seen in the mesogastrium. For further investigations, abdominal ultrasonography was performed and a blood sample was taken.
Abdominal ultrasonography** revealed that the mass detected on the radiograph was a severely enlarged spleen with normal echo-texture. There was no free abdominal fluid. In the hilus of the spleen a wide loop-like vessel was seen, which was thought to be the main splenic vein. Colour Doppler ultrasound failed to reveal any flow in it.
The veins in the splenic parenchyma were also dilated. Both colour and duplex Doppler ultrasonography revealed bi-directional flow in the parenchymal splenic veins (Figures 4 a, b and 5). The direction of the flow was changing according to the respiratory cycle, i.e., during expiration the blood flowed towards the smallest splenic vein branches, while during inspiration flow towards the splenic hilus was detected in them. Similar values of peak velocities were detected both during inspiration and expiration by duplex Doppler technique. When the dog was panting, bi-directional flow was still observed, but the frequency of the direction-alterations became higher corresponding to the increased respiratory rate, meanwhile the peak velocities became smaller in both directions (Figure 6).
A haemogram indicated a mildly reduced haematocrit (0.35, normal: 0.38–0.50) and haemoglobin concentration (11.6 g/dl, normal: 12.0–18.0) with a physiological red blood cell count (5.59x1012/l, normal: 5.5–8.0x1012). The platelet count was markedly reduced (16x109/l, normal: 200–800x109).
Splenic torsion was suspected and a splenectomy was suggested. However the owner refused permission for surgery, but agreed to bring the dog back for a re-check during the next morning. The dog did not receive any type of treatment. Fourteen hours later the alert dog had a normal sized abdomen, and physical examination as well as abdominal ultrasonography did not detect any abnormality. The haematocrit (0.51) and haemoglobin concentration (17.3 g/dl) also became normal. The red blood cell count increased above the normal reference range (8.55x1012/l) and the platelet count had virtually returned to normal (123x109/l).

Discussion
Splenomegaly or a mid-abdominal mass is usually found on the radiographs made about dogs with isolated splenic torsion (2, 3, 4, 5, 6, 7), however ultrasonography is always necessary to confirm the diagnosis.
In our case the echo-texture of the spleen was sonographically normal, and dilated vessels were detected in the parenchyma. In the hilus of the spleen the main splenic vein was seen, which formed a loop curving in about 270o. In this vein there was not any detectable flow, but in the adjacent splenic artery flow still was detectable by means of colour Doppler ultrasonography. In dogs suffering from isolated splenic torsion, the lack of blood flow is expected in the dilated parenchymal splenic veins (3). In our case, we assume that the respiratory movements due to the inspiration and expiration caused the passive movement of the stagnating blood in the splenic veins, resulting in the bi-directional Doppler pattern. This theory seems to be confirmed by the fact that the increasing respiratory rate (during panting) simultaneously increased the frequency of the flow-direction-alterations.
This rare case shows that not only the absence of blood flow in the parenchymal splenic veins does not rule out the torsion of the splenic pedicle. We suggest that Doppler ultrasound examination of the splenic veins should be performed possibly in all cases of splenomegaly.
Since the congested spleen contained a large amount of blood, the haematocrit, the haemoglobin concentration and platelet count were reduced, similarly to other reports (3, 5). The torsion of the spleen must have spontaneously resolved subsequent to the initial examination, and the haematological abnormalities corrected by the time of the re-examination, as the red blood cells and platelets could re-enter the circulation from the spleen.
The aetiology of the splenic torsion as well as its resolution remained unclear. Probably, the lack of thrombus formation in the splenic veins and the low degree of the torsion of the splenic pedicle made the spontaneous recovery possible. Spontaneous resolution of a splenic torsion has been described in humans (2) but this is the first reported case in a dog according to our knowledge (8).

*    A part of this article was published in The Veterinary Record (8). However, the description of the bi-directional blood flow
      in the splenic parenchymal veins has not, as yet, been published.
** Brüel & Kjaer Panther 2002 ultrasound machine equipped with a 3.5–4.3–5.0 MHz convex transducer, Denmark.
 

Acknowledgements. We would like to thank DR. ALLISON M. MILLS for her assistance with the revision of the English text.

Figure 1.
Colour Doppler image of the spleen of a Great Dane suffering from splenic torsion (the case report is not about this dog)
The lack of blood flow in the colour box is obvious. The structure of the spleen is abnormal: anechoic areas are separated by small linear echodensities

Figure 2.
Colour Doppler image of a parenchymal splenic vein in a healthy dog
The vessel gets wider towards the hilus, where it eventually breaks through the splenic capsule and leaves the spleen. Blue colour
indicates flow away from the transducer, i.e., the blood flows from the smallest branches towards the wider ones

Figure 3.
Duplex Doppler waveform of a splenic parenchymal vein in a healthy dog
The velocities displayed under the baseline indicates flow away from the transducer (compatible with the blue colour on the colour Doppler image). The flow is of low velocity and only mild phasic changes can be observed

Figure 4.
Colour Doppler images of a parenchymal splenic vein in the St Bernard dog with isolated splenic torsion
There is 1 second interval between the a and b image. The direction of blood flow is changing according to the respiratory cycle
a – During expiration: red colour indicates that the blood flows towards the transducer, i.e., towards the smallest intra-parenchymal branches
b – During inspiration: blue colour indicates that the blood flows away from the transducer (i.e., towards the splenic hilus)

Figure 5.
Duplex Doppler spectrum of the same parenchymal splenic vein, which is in Figures 4 a and b
Duplex Doppler ultrasound technique shows that in the splenic vein the blood flows towards the transducer during expiration (i.e., towards the smallest intra-parenchymal branches). This is displayed above the baseline. The flow is away from the transducer during inspiration (i.e., towards the splenic hilus).This is displayed below the baseline.
The direction of the blood flow is changing according to the respiratory cycle. The maximum velocities are about the same into directions (approximately 10 cm/s). (Doppler angle: 5^o, pulse repetition frequency: 1250)

Figure 6.
Duplex Doppler waveform of the same parenchymal splenic vein as imaged on Figures 4 a, b and 5, when the dog is panting
The Doppler pattern is similarly bi-directional to the spectrum that is seen on Figure 5, but the peak velocities are lower (approximately 5 cm/s) and the direction-changes occur more frequently corresponding to the higher respiratory rate

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