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Ultrasonography of the spleen in 50 healthy cows
The Veterinary Journal The Veterinary Journal 171 (2006) 513–518 www.elsevier.com/locate/tvjl
Ultrasonography of the spleen in 50 healthy cowsq U. Braun *, D. Sicher Department of Farm Animals, University of Zurich, Winterthurerstrasse 260, CH-8057 Zurich, Switzerland Accepted 3 January 2005
Abstract This paper describes the ultrasonographic appearance, location and size of the spleen in 50 healthy commercial milk cows destined for slaughter. The intercostal spaces of the left thoracic wall were scanned with a 3.5 MHz linear transducer. In each intercostal space, the appearance of the splenic parenchyma, the dorsal and ventral margins and the distance between them, and the diameter of the splenic vessels were recorded. The spleen was seen in intercostal spaces 7–12. It was 2.0–5.0 cm thick, and tapered ventrally. The splenic capsule appeared as an echogenic line. The splenic parenchyma consisted of numerous small regularly spaced echoes, and vessels within the parenchyma appeared as anechoic round to oval or elongated images. The long axis was oblique, running caudodorsal to cranioventral. The distance from the dorsal margin of the spleen to the midline of the back was greatest in the 7th intercostal space (60.9 ± 6.81) and smallest in the 12th intercostal space (12.7 ± 2.85 cm). The extent of the spleen was greatest in the 8th intercostal space (24.9 ± 10.77 cm) and smallest in the 12th intercostal space (9.5 ± 5.38 cm). The mean diameter of the splenic vessels ranged from 0.66 ± 0.28 to 0.90 ± 0.65 cm, depending on the intercostal space scanned. Ultrasonography of the spleen in healthy cows provides information that can be used as a reference when examining cattle with suspected splenic disease. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Ultrasonography; Healthy cows; Spleen; Normal values
1. Introduction In cattle, the spleen lies almost vertically on the cranial end of the dorsal sac of the rumen and the cranial surface of the reticulum on the left side of the abdomen. It extends from the dorsal ends of the last two ribs to the costochondral junctions of the 7th and 8th ribs (Nickel et al., 1987). The spleen has a number of functions including extramedullary production of haematopoietic cells, recognition and removal of abnormal blood cells, bacteria and parasites, and the production of lymphoq
This report represents a portion of a thesis submitted by Dr. Sicher to the Veterinary Faculty of the University of Zurich, Switzerland, as required for the DrMedVet degree. * Corresponding author. Tel.: +41 1 6358241; fax: +41 1 6358904. E-mail address: [email protected] (U. Braun). 1090-0233/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tvjl.2005.01.001
cytes and specific antibodies in many septicaemic diseases (Radostits et al., 2000; Sto¨ber, 2002). In many infectious processes, the spleen enlarges to perform its functions better. Penetration of a foreign body from the reticulum into the spleen may cause suppurative splenitis. Haematogenous spread of disease to the spleen may occur in septicaemic or pyogenous processes. Although the spleen is often involved in bacterial or parasitic diseases such as babesiosis or anthrax, signs of splenic disease are not usually foremost in the clinical presentation. Tumours also occur in the spleen with lymphoma being the most important (Radostits et al., 2000; Sto¨ber, 2002). There are no characteristic symptoms of splenic disease and no specific methods for the examination of the spleen in cattle. In contrast to horses, the spleen cannot be examined by rectal palpation. Moreover, there
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are no laboratory tests that are specific for the spleen. In cattle, the reticulum (Braun et al., 1993a) and the lungs (Braun et al., 1997), but not the spleen, can be evaluated by radiography (Sicher, 1995). Although laparoscopy (Anderson et al., 1993) and left flank exploratory laparotomy allow visualisation of the spleen, these are invasive procedures. Ultrasonography is an ideal, non-invasive method for examining the bovine spleen. In cattle with traumatic reticuloperitonitis, ultrasonography has been used to evaluate changes in the spleen such as fibrinous adhesions and abscesses (Braun, 2003; Braun et al., 1993b, 1998). Ultrasonography has been used to detect tumours, trauma and torsion of the spleen in dogs (Nyland et al., 2002) and tumours, haematomas and abscesses of the spleen in horses (Reef, 1998) but, to our knowledge, detailed information about the ultrasonographic appearance of the normal bovine spleen and its vessels has not been reported although some information of the normal sonographic findings of the spleen is given by Braun (1997). The goal of the present study was to investigate these features.
2. Material and methods 2.1. Cows Fifty clinically healthy Swiss Braunvieh and Simmental commercial cows destined for slaughter were examined. The cows ranged in age from 2.3 to 11 years (mean, 4.8 years) and weighed 436–699 kg (mean, 539.8 kg). The cows were unsedated and standing during the examination. 2.2. Ultrasonographic examination of the spleen The ultrasonographic examinations were performed using a realtime scanner and a 5.0-MHz linear transducer (Concept 2000, Dynamic Imaging Ltd., Pameda AG). The examination procedure has been described by Sicher (1995). The left lateral thorax was clipped from the caudal border of the forelimb and scapula to the caudal aspect of the last rib and from the transverse processes of the thoracic vertebrae to the ventral midline. Remaining hair was removed with depilatory cream (Depilatorium, Veterinaria AG). After the application of transmission gel (Aquasonic, Polymed), each intercostal space was scanned, beginning dorsally and progressing ventrally with the transducer held parallel to the ribs. The left ventral thorax was scanned with the transducer held parallel to the long axis of the cow to determine the extent of the spleen in this region. The spleen was first assessed subjectively by evaluating its echogenic pattern and noting whether the paren-
Fig. 1. Schematic representation of the determination of position and extent of the spleen via ultrasonography in a cow. 1 – spleen; 2 – 6th rib; 3 – 13th rib. (a) dorsal margin of the spleen; (b) ventral margin of the spleen; (c) extent of the spleen.
chyma appeared homogeneous or heterogeneous. We also recorded whether the splenic blood vessels could be visualised and, if so, their appearance, and whether the splenic capsule appeared as an echogenic line separating the splenic parenchyma from adjacent structures. The location of the spleen was determined by measuring the extent to which it could be seen in each intercostal space. Measurements were made on cross-sectional views of the spleen and at maximum inspiration (see Fig. 1). The positions of the dorsal and ventral borders of the spleen were determined in relation to the midline of the back. The visible extent of the spleen in a given intercostal space was determined by subtracting the distance between the dorsal splenic margin and the midline of the back from the distance between the ventral splenic margin and the midline. The diameters of the splenic vessels were measured electronically on the ultrasonogram by means of the two cursors, noting if the vessels were viewed in longitudinal or cross-section. 2.3. Post mortem findings All cows were slaughtered within three days following the end of the study. Each spleen was palpated, and its exterior and cut surfaces were examined macroscopically. 2.4. Statistics Statistical calculations were performed by use of the calculation program SPSS/PC+ according to the method of Norusis (1990). 3. Results The spleen was situated between the rumen and left abdominal wall in all cows. The visceral surface of the spleen lay against the cranial aspect of the dorsal sac
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Fig. 2. Ultrasonogram (a) and schematic representation (b) of the spleen. A 5.0-MHz linear transducer was placed parallel to the ribs in the 10th intercostal space on the left side of the cow. 1 – thoracic wall; 2 – spleen; 3 – spleen vessel in longitudinal section; 4 – rumen, Ds – dorsal; Vt – ventral; Md – medial.
of the rumen and the cranial surface of the reticulum. The parietal surface was in contact with the diaphragm. The dorsal part of the spleen was superimposed by the lung and could not be imaged. The various layers of the thoracic wall appeared as bands of different echogenicity. The ultrasonographic appearance of the pleura, lung, rumen and reticulum were in agreement with previous reports (Braun and Go¨tz, 1994; Braun et al., 1996). The spleen was seen to move in synchrony with respiration. The spleen was 2–8 cm thick in depth and tapered ventrally. The parenchymal pattern of the normal spleen consisted of numerous weak echoes homoge-
neously distributed over the entire area of the organ (Fig. 2). The capsule of the spleen could be imaged as a fine echogenic line at the surface of the spleen texture. Spleen vessels could be seen within the normal texture. The vessels appeared as elongated anechoic structures on longitudinal section (Figs. 2 and 3) and round to oval anechoic structures on cross-section (Fig. 4). Splenic veins could be differentiated from splenic arteries based on the echogenic walls seen in the arteries (Fig. 2). Changes in the spleen texture, such as abscessation, could not be detected. Abnormalities were not found on the visceral and parietal surface.
Fig. 3. Ultrasonogram (a) and schematic representation (b) of the spleen. A 5.0-MHz linear transducer was placed parallel to the ribs in the 9th intercostal space on the left side of the cow. 1 – thoracic wall; 2 – spleen; 3 – splenic vessels; 4 – rumen; Ds – dorsal; Vt – ventral; Md – medial.
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Fig. 4. Ultrasonogram (a) and schematic representation (b) of the spleen. A 5.0-MHz linear transducer was placed in the left paramedian region parallel to the ventral midline. The spleen extends under the reticulum, which appears to be indented by the spleen. 1 – thoracic wall; 2 – spleen; 3 – spleen vessels in cross-section; 4 – reticulum; Cr – cranial; Cd – caudal; Ds – dorsal.
The spleen could be seen in intercostal spaces 7–11 in all cows and in the 12th intercostal space in 42 cows. It was never seen caudal to the last rib. The spleen was seen in the 7th and 8th intercostal spaces to extend to the ventral midline in 12 and eight cows, respectively. In the 7th and 8th intercostal spaces, the spleen was located predominantly between the reticulum and abdominal wall. In the 9th to 12th intercostal spaces, it was predominantly between the rumen and abdominal wall (Table 1). The dorsal and ventral margins of the spleen ran from cranioventral to caudodorsal (Fig. 5). The distance between the dorsal margin of the spleen and midline of the back was greatest in the 7th intercostal space (60.9 ± 6.81 cm; Table 2). The distance between the dorsal margin of the spleen and the midline of the back decreased caudally and in the 12th intercostal space, was only 12.7 ± 2.85 cm. Similar to the dorsal margin, the
distance between the ventral margin of the spleen and the midline of the back was greatest in the 7th intercostal space (85.4 ± 12.11 cm) and shortest in the 12th intercostal space (23.6 ± 3.73 cm). The measured extent of the spleen was largest in the 8th intercostal space (24.9 ± 10.77 cm) and smallest in the 12th intercostal space (9.5 ± 5.38 cm). The number of cows in which splenic vessels were seen varied from 41 to 50 cows, depending on the intercostal space scanned (Table 3). The vessels were seen in longitudinal and cross-section, and their diameters ranged from 0.66 ± 0.28 cm (10th intercostal space) to 0.90 ± 0.65 cm (11th intercostal space).
Table 1 Position of the spleen in relation to the reticulum and rumen as determined by ultrasonography in 50 healthy cows ICS
Spleen between reticulum and abdominal wall
Spleen between rumen and abdominal wall
7 8 9 10 11 12a
42 33 4 1 0 0
8 17 46 49 50 42
ICS, intercostal space. a The spleen was seen in the 12th intercostal space in only 42/50 cows.
Fig. 5. The dorsal and ventral margins of the spleen have been drawn from the 7th to the 12th intercostal space on a Swiss Braunvieh cow. This outline corresponds to the mean positions of the dorsal and ventral margins of the spleen in 50 cows.
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Table 2 Results of ultrasonographic examination of the spleen of 50 cows ICS
7 8 9 10 11 12c
Dorsal margina
Ventral margina b
Extent (cm) b
Mean
SD
Normal range
Mean
SD
Normal range
Mean
SD
Normal rangeb
60.9 52.4 41.8 29.4 18.7 12.7
6.81 7.11 5.96 6.95 5.27 2.85
47–75 38–67 30–54 16–43 8–29 7–18
85.4 78.6 59.1 46.9 33.4 23.6
12.11 13.52 7.28 7.91 5.10 3.73
61–110 52–106 45–74 31–63 23–44 16–31
19.9 24.9 16.6 17.4 14.4 9.5
12.27 10.77 6.03 6.03 4.46 5.38
0–44 3–46 5–29 5–29 5–23 0–20
ICS, intercostal space. a Distance to dorsal midline (cm). b Mean ± 2 SD. c The spleen was seen in the 12th intercostal space in only 42/50 cows.
Table 3 Diameter and orientation of splenic vessels as determined by ultrasonography in 50 healthy cows ICS (no. of cows)a
7 8 9 10 11 12
(41) (48) (49) (50) (50) (42)
Diameter
Orientation of vessels on ultrasonograms
Mean
SD
Normal range (mean ± 2 SD)
Longitudinal section
Cross-section
Longitudinal and cross-sections
0.81 0.87 0.77 0.66 0.90 0.74
0.32 0.36 0.06 0.28 0.65 0.23
0.2–1.5 0.2–1.6 0.7–0.9 0.1–1.2 0.1–2.2 0.3–1.2
8 19 13 15 18 2
4 5 3 5 12 10
29 24 33 30 20 30
ICS, intercostal space. a Number of cows in which splenic vessels were seen.
3.1. Post mortem findings Post mortem findings confirmed that the cows were healthy as stated. In six cows, there were mild fibrinous adhesions on the spleen that had not been detected ultrasonographically.
4. Discussion In the present study, ultrasonographic examination of the spleen proved to be a straightforward procedure in all cows and, because of its close proximity to the left thoracic wall, the spleen could be clearly visualised. The organ was examined with a 5.0-MHz linear transducer, which yielded very good images, but because the spleen is situated immediately adjacent to the abdominal wall and is only a few centimetres thick, a transducer with a higher frequency and thus, lower penetration, such as a 7.5-MHz transducer, could also be used for examination and would improve the resolution of the image. We recommend using a linear rather than a sector transducer because, when using the latter, structures close to the transducer yield relatively small images. The ultrasonographic appearance of the splenic parenchyma was similar to that reported for small animals (Nyland et al., 2002) and horses (Reef, 1998). The ultrasonographic appearance of the splenic parenchyma in cattle resembled that of hepatic parenchyma
(Braun, 1990); however, the two organs are easily differentiated because of their different anatomical locations. Moreover, the triangular-shaped caudal vena cava and star-shaped branching of the portal vein can be used to identify the liver. In eight cows, the spleen could be seen in intercostal spaces 7–11 but not in the 12th intercostal space. The spleen was seen at the ventral midline in the 8th intercostal space in eight cows and in the 7th intercostal space in 12 cows, although others have reported that the ventral border of the spleen does not extend beyond the costochondral junctions of the 7th and 8th ribs (Nickel et al., 1987). However, depending on the amount of blood the spleen contains, its free ventral margin may extend as far as to the area of the xyphoid (Sto¨ber, 1990). When this happens, the ventral aspect of the reticulum may be indented by the spleen and this should not be mistaken for a pathological finding. In a previous study (Braun and Go¨tz, 1994), the spleen could not be seen in the 7th intercostal space in 3/51 cows, reflecting the variable anatomical position of the spleen (Nickel et al., 1987). The weight of the cows used in the present study ranged widely from 436 to 699 kg. This was due mainly to body condition, which varied from thin to good, and not to the overall size of the cows. We assumed that the large standard deviations of some of the ultrasonographic measurements were due partly to the body condition of the cows and partly to variations in the amount of blood within the spleen.
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Our measurements are likely to be most useful for clinicians with little experience in ultrasonographic examination of the spleen. They can be used to assess whether the extent of the spleen is normal or not. However, in the past 10 years at our clinic, we have not seen any cows with abnormally large or small spleens, although we have examined cows with dilated splenic vessels due to severe splenitis. The primary goal of the present study was to describe the ultrasonographic appearance of the healthy spleen. Abnormal splenic findings, often due to traumatic reticuloperitonitis, are frequently encountered in veterinary practice. We conclude that ultrasonography is a useful tool for the non-invasive examination of the spleen. Its appearance and size in healthy cows can serve as reference values for the diagnosis of pathological changes in the spleen. To date, there are a few reports describing changes in the bovine spleen due to disorders such as traumatic reticuloperitonitis (Braun, 2003; Braun et al., 1993a,b, 1998) although in dogs, tumours, haematoma, atrophy and hypertrophy of the spleen as well as splenic torsion have been diagnosed via ultrasonography (Nyland et al., 2002).
References Anderson, D.E., Gaughan, E.M., St.-Jean, G., 1993. Normal laparoscopic anatomy of the bovine abdomen. American Journal of Veterinary Research 54, 1170–1176. Braun, U., 1990. Ultrasonographic examination of the liver in cows. American Journal of Veterinary Research 51, 1522– 1526. Braun, U., 1997. Haube. In: Atlas und Lehrbuch der Ultraschalldiagnostik beim Rind. Parey Buchverlag, Berlin, pp. 9–33. Braun, U., 2003. Ultrasonography in gastrointestinal disease in cattle. The Veterinary Journal 166, 112–124.
Braun, U., Flu¨ckiger, M., Na¨geli, F., 1993a. Radiography as an aid in the diagnosis of traumatic reticuloperitonitis in cattle. The Veterinary Record 132, 103–109. Braun, U., Go¨tz, M., 1994. Ultrasonography of the reticulum in cows. American Journal of Veterinary Research 55, 325–332. Braun, U., Go¨tz, M., Marmier, O., 1993b. Ultrasonographic findings in cows with traumatic reticuloperitonitis. The Veterinary Record 133, 416–422. Braun, U., Iselin, U., Lischer, C., Fluri, E., 1998. Ultrasonographic findings in five cows before and after treatment of reticular abscesses. The Veterinary Record 142, 184–189. Braun, U., Pusterla, N., Flu¨ckiger, M., 1997. Ultrasonographic findings in cattle with pleuropneumonia. The Veterinary Record 141, 12–17. Braun, U., Sicher, D., Pusterla, N., 1996. Ultrasonography of the lungs, pleura, and mediastinum in healthy cows. American Journal of Veterinary Research 57, 432–438. Nickel, R., Schummer, A., Seiferle, E., 1987. Milz, Lien, Splen. In: Lehrbuch der Anatomie der Haustiere, sixth ed.Eingeweide, vol. 2 Paul Parey, Berlin, Hamburg, pp. 213–218. Norusis, M.J., 1990. SPSS/PC+ V4.0. Base Manual for the IBM PC/ XT/AT and PS/2. SPSS Inc., Chicago. Nyland, T.G, Mattoon, J.S., Herrgesell, E.R., Wisner, E.R., 2002. Spleen. In: Nyland, T.G., Mattoon, J.S. (Eds.), Small Animal Diagnostic Ultrasound, second ed. W.B. Saunders Company, Philadelphia, pp. 128–143. Radostits, O.M., Gay, C.C., Blood, D.C., Hinchcliff, K.W., 2000. Diseases of the spleen, lymphadenopathy and thymic disease. In: Veterinary Medicine. A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses, ninth ed. W.B. Saunders Company, London, pp. 417–420. Reef, V.B., 1998. Adult abdominal ultrasonography. In: Equine Diagnostic Ultrasound. W.B. Saunders Company, Philadelphia, pp. 273–363. Sicher, D., 1995. Sonographische Untersuchungen an Lunge, Mediastinum und Milz des Rindes. DrMedVet Thesis, Faculty of Veterinary Medicine, University of Zurich. Sto¨ber, M., 1990. Lymphapparat. In: Dirksen, G., Gru¨nder, H.-D., Sto¨ber, M., Rosenberger, G. (Eds.), Die klinische Untersuchung des Rindes, third ed. Paul Parey, Berlin Hamburg, pp. 163–170. Sto¨ber, M., 2002. Krankheiten der Milz. In: Dirksen, G., Gru¨nder, H.-D., Sto¨ber, M. (Eds.), Innere Medizin und Chirurgie des Rindes, fourth ed. Parey Buchverlag, Berlin, pp. 152–157.
Ultrasonography of the spleen in 50 healthy cowsq U. Braun *, D. Sicher Department of Farm Animals, University of Zurich, Winterthurerstrasse 260, CH-8057 Zurich, Switzerland Accepted 3 January 2005
Abstract This paper describes the ultrasonographic appearance, location and size of the spleen in 50 healthy commercial milk cows destined for slaughter. The intercostal spaces of the left thoracic wall were scanned with a 3.5 MHz linear transducer. In each intercostal space, the appearance of the splenic parenchyma, the dorsal and ventral margins and the distance between them, and the diameter of the splenic vessels were recorded. The spleen was seen in intercostal spaces 7–12. It was 2.0–5.0 cm thick, and tapered ventrally. The splenic capsule appeared as an echogenic line. The splenic parenchyma consisted of numerous small regularly spaced echoes, and vessels within the parenchyma appeared as anechoic round to oval or elongated images. The long axis was oblique, running caudodorsal to cranioventral. The distance from the dorsal margin of the spleen to the midline of the back was greatest in the 7th intercostal space (60.9 ± 6.81) and smallest in the 12th intercostal space (12.7 ± 2.85 cm). The extent of the spleen was greatest in the 8th intercostal space (24.9 ± 10.77 cm) and smallest in the 12th intercostal space (9.5 ± 5.38 cm). The mean diameter of the splenic vessels ranged from 0.66 ± 0.28 to 0.90 ± 0.65 cm, depending on the intercostal space scanned. Ultrasonography of the spleen in healthy cows provides information that can be used as a reference when examining cattle with suspected splenic disease. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Ultrasonography; Healthy cows; Spleen; Normal values
1. Introduction In cattle, the spleen lies almost vertically on the cranial end of the dorsal sac of the rumen and the cranial surface of the reticulum on the left side of the abdomen. It extends from the dorsal ends of the last two ribs to the costochondral junctions of the 7th and 8th ribs (Nickel et al., 1987). The spleen has a number of functions including extramedullary production of haematopoietic cells, recognition and removal of abnormal blood cells, bacteria and parasites, and the production of lymphoq
This report represents a portion of a thesis submitted by Dr. Sicher to the Veterinary Faculty of the University of Zurich, Switzerland, as required for the DrMedVet degree. * Corresponding author. Tel.: +41 1 6358241; fax: +41 1 6358904. E-mail address: [email protected] (U. Braun). 1090-0233/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tvjl.2005.01.001
cytes and specific antibodies in many septicaemic diseases (Radostits et al., 2000; Sto¨ber, 2002). In many infectious processes, the spleen enlarges to perform its functions better. Penetration of a foreign body from the reticulum into the spleen may cause suppurative splenitis. Haematogenous spread of disease to the spleen may occur in septicaemic or pyogenous processes. Although the spleen is often involved in bacterial or parasitic diseases such as babesiosis or anthrax, signs of splenic disease are not usually foremost in the clinical presentation. Tumours also occur in the spleen with lymphoma being the most important (Radostits et al., 2000; Sto¨ber, 2002). There are no characteristic symptoms of splenic disease and no specific methods for the examination of the spleen in cattle. In contrast to horses, the spleen cannot be examined by rectal palpation. Moreover, there
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are no laboratory tests that are specific for the spleen. In cattle, the reticulum (Braun et al., 1993a) and the lungs (Braun et al., 1997), but not the spleen, can be evaluated by radiography (Sicher, 1995). Although laparoscopy (Anderson et al., 1993) and left flank exploratory laparotomy allow visualisation of the spleen, these are invasive procedures. Ultrasonography is an ideal, non-invasive method for examining the bovine spleen. In cattle with traumatic reticuloperitonitis, ultrasonography has been used to evaluate changes in the spleen such as fibrinous adhesions and abscesses (Braun, 2003; Braun et al., 1993b, 1998). Ultrasonography has been used to detect tumours, trauma and torsion of the spleen in dogs (Nyland et al., 2002) and tumours, haematomas and abscesses of the spleen in horses (Reef, 1998) but, to our knowledge, detailed information about the ultrasonographic appearance of the normal bovine spleen and its vessels has not been reported although some information of the normal sonographic findings of the spleen is given by Braun (1997). The goal of the present study was to investigate these features.
2. Material and methods 2.1. Cows Fifty clinically healthy Swiss Braunvieh and Simmental commercial cows destined for slaughter were examined. The cows ranged in age from 2.3 to 11 years (mean, 4.8 years) and weighed 436–699 kg (mean, 539.8 kg). The cows were unsedated and standing during the examination. 2.2. Ultrasonographic examination of the spleen The ultrasonographic examinations were performed using a realtime scanner and a 5.0-MHz linear transducer (Concept 2000, Dynamic Imaging Ltd., Pameda AG). The examination procedure has been described by Sicher (1995). The left lateral thorax was clipped from the caudal border of the forelimb and scapula to the caudal aspect of the last rib and from the transverse processes of the thoracic vertebrae to the ventral midline. Remaining hair was removed with depilatory cream (Depilatorium, Veterinaria AG). After the application of transmission gel (Aquasonic, Polymed), each intercostal space was scanned, beginning dorsally and progressing ventrally with the transducer held parallel to the ribs. The left ventral thorax was scanned with the transducer held parallel to the long axis of the cow to determine the extent of the spleen in this region. The spleen was first assessed subjectively by evaluating its echogenic pattern and noting whether the paren-
Fig. 1. Schematic representation of the determination of position and extent of the spleen via ultrasonography in a cow. 1 – spleen; 2 – 6th rib; 3 – 13th rib. (a) dorsal margin of the spleen; (b) ventral margin of the spleen; (c) extent of the spleen.
chyma appeared homogeneous or heterogeneous. We also recorded whether the splenic blood vessels could be visualised and, if so, their appearance, and whether the splenic capsule appeared as an echogenic line separating the splenic parenchyma from adjacent structures. The location of the spleen was determined by measuring the extent to which it could be seen in each intercostal space. Measurements were made on cross-sectional views of the spleen and at maximum inspiration (see Fig. 1). The positions of the dorsal and ventral borders of the spleen were determined in relation to the midline of the back. The visible extent of the spleen in a given intercostal space was determined by subtracting the distance between the dorsal splenic margin and the midline of the back from the distance between the ventral splenic margin and the midline. The diameters of the splenic vessels were measured electronically on the ultrasonogram by means of the two cursors, noting if the vessels were viewed in longitudinal or cross-section. 2.3. Post mortem findings All cows were slaughtered within three days following the end of the study. Each spleen was palpated, and its exterior and cut surfaces were examined macroscopically. 2.4. Statistics Statistical calculations were performed by use of the calculation program SPSS/PC+ according to the method of Norusis (1990). 3. Results The spleen was situated between the rumen and left abdominal wall in all cows. The visceral surface of the spleen lay against the cranial aspect of the dorsal sac
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Fig. 2. Ultrasonogram (a) and schematic representation (b) of the spleen. A 5.0-MHz linear transducer was placed parallel to the ribs in the 10th intercostal space on the left side of the cow. 1 – thoracic wall; 2 – spleen; 3 – spleen vessel in longitudinal section; 4 – rumen, Ds – dorsal; Vt – ventral; Md – medial.
of the rumen and the cranial surface of the reticulum. The parietal surface was in contact with the diaphragm. The dorsal part of the spleen was superimposed by the lung and could not be imaged. The various layers of the thoracic wall appeared as bands of different echogenicity. The ultrasonographic appearance of the pleura, lung, rumen and reticulum were in agreement with previous reports (Braun and Go¨tz, 1994; Braun et al., 1996). The spleen was seen to move in synchrony with respiration. The spleen was 2–8 cm thick in depth and tapered ventrally. The parenchymal pattern of the normal spleen consisted of numerous weak echoes homoge-
neously distributed over the entire area of the organ (Fig. 2). The capsule of the spleen could be imaged as a fine echogenic line at the surface of the spleen texture. Spleen vessels could be seen within the normal texture. The vessels appeared as elongated anechoic structures on longitudinal section (Figs. 2 and 3) and round to oval anechoic structures on cross-section (Fig. 4). Splenic veins could be differentiated from splenic arteries based on the echogenic walls seen in the arteries (Fig. 2). Changes in the spleen texture, such as abscessation, could not be detected. Abnormalities were not found on the visceral and parietal surface.
Fig. 3. Ultrasonogram (a) and schematic representation (b) of the spleen. A 5.0-MHz linear transducer was placed parallel to the ribs in the 9th intercostal space on the left side of the cow. 1 – thoracic wall; 2 – spleen; 3 – splenic vessels; 4 – rumen; Ds – dorsal; Vt – ventral; Md – medial.
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Fig. 4. Ultrasonogram (a) and schematic representation (b) of the spleen. A 5.0-MHz linear transducer was placed in the left paramedian region parallel to the ventral midline. The spleen extends under the reticulum, which appears to be indented by the spleen. 1 – thoracic wall; 2 – spleen; 3 – spleen vessels in cross-section; 4 – reticulum; Cr – cranial; Cd – caudal; Ds – dorsal.
The spleen could be seen in intercostal spaces 7–11 in all cows and in the 12th intercostal space in 42 cows. It was never seen caudal to the last rib. The spleen was seen in the 7th and 8th intercostal spaces to extend to the ventral midline in 12 and eight cows, respectively. In the 7th and 8th intercostal spaces, the spleen was located predominantly between the reticulum and abdominal wall. In the 9th to 12th intercostal spaces, it was predominantly between the rumen and abdominal wall (Table 1). The dorsal and ventral margins of the spleen ran from cranioventral to caudodorsal (Fig. 5). The distance between the dorsal margin of the spleen and midline of the back was greatest in the 7th intercostal space (60.9 ± 6.81 cm; Table 2). The distance between the dorsal margin of the spleen and the midline of the back decreased caudally and in the 12th intercostal space, was only 12.7 ± 2.85 cm. Similar to the dorsal margin, the
distance between the ventral margin of the spleen and the midline of the back was greatest in the 7th intercostal space (85.4 ± 12.11 cm) and shortest in the 12th intercostal space (23.6 ± 3.73 cm). The measured extent of the spleen was largest in the 8th intercostal space (24.9 ± 10.77 cm) and smallest in the 12th intercostal space (9.5 ± 5.38 cm). The number of cows in which splenic vessels were seen varied from 41 to 50 cows, depending on the intercostal space scanned (Table 3). The vessels were seen in longitudinal and cross-section, and their diameters ranged from 0.66 ± 0.28 cm (10th intercostal space) to 0.90 ± 0.65 cm (11th intercostal space).
Table 1 Position of the spleen in relation to the reticulum and rumen as determined by ultrasonography in 50 healthy cows ICS
Spleen between reticulum and abdominal wall
Spleen between rumen and abdominal wall
7 8 9 10 11 12a
42 33 4 1 0 0
8 17 46 49 50 42
ICS, intercostal space. a The spleen was seen in the 12th intercostal space in only 42/50 cows.
Fig. 5. The dorsal and ventral margins of the spleen have been drawn from the 7th to the 12th intercostal space on a Swiss Braunvieh cow. This outline corresponds to the mean positions of the dorsal and ventral margins of the spleen in 50 cows.
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Table 2 Results of ultrasonographic examination of the spleen of 50 cows ICS
7 8 9 10 11 12c
Dorsal margina
Ventral margina b
Extent (cm) b
Mean
SD
Normal range
Mean
SD
Normal range
Mean
SD
Normal rangeb
60.9 52.4 41.8 29.4 18.7 12.7
6.81 7.11 5.96 6.95 5.27 2.85
47–75 38–67 30–54 16–43 8–29 7–18
85.4 78.6 59.1 46.9 33.4 23.6
12.11 13.52 7.28 7.91 5.10 3.73
61–110 52–106 45–74 31–63 23–44 16–31
19.9 24.9 16.6 17.4 14.4 9.5
12.27 10.77 6.03 6.03 4.46 5.38
0–44 3–46 5–29 5–29 5–23 0–20
ICS, intercostal space. a Distance to dorsal midline (cm). b Mean ± 2 SD. c The spleen was seen in the 12th intercostal space in only 42/50 cows.
Table 3 Diameter and orientation of splenic vessels as determined by ultrasonography in 50 healthy cows ICS (no. of cows)a
7 8 9 10 11 12
(41) (48) (49) (50) (50) (42)
Diameter
Orientation of vessels on ultrasonograms
Mean
SD
Normal range (mean ± 2 SD)
Longitudinal section
Cross-section
Longitudinal and cross-sections
0.81 0.87 0.77 0.66 0.90 0.74
0.32 0.36 0.06 0.28 0.65 0.23
0.2–1.5 0.2–1.6 0.7–0.9 0.1–1.2 0.1–2.2 0.3–1.2
8 19 13 15 18 2
4 5 3 5 12 10
29 24 33 30 20 30
ICS, intercostal space. a Number of cows in which splenic vessels were seen.
3.1. Post mortem findings Post mortem findings confirmed that the cows were healthy as stated. In six cows, there were mild fibrinous adhesions on the spleen that had not been detected ultrasonographically.
4. Discussion In the present study, ultrasonographic examination of the spleen proved to be a straightforward procedure in all cows and, because of its close proximity to the left thoracic wall, the spleen could be clearly visualised. The organ was examined with a 5.0-MHz linear transducer, which yielded very good images, but because the spleen is situated immediately adjacent to the abdominal wall and is only a few centimetres thick, a transducer with a higher frequency and thus, lower penetration, such as a 7.5-MHz transducer, could also be used for examination and would improve the resolution of the image. We recommend using a linear rather than a sector transducer because, when using the latter, structures close to the transducer yield relatively small images. The ultrasonographic appearance of the splenic parenchyma was similar to that reported for small animals (Nyland et al., 2002) and horses (Reef, 1998). The ultrasonographic appearance of the splenic parenchyma in cattle resembled that of hepatic parenchyma
(Braun, 1990); however, the two organs are easily differentiated because of their different anatomical locations. Moreover, the triangular-shaped caudal vena cava and star-shaped branching of the portal vein can be used to identify the liver. In eight cows, the spleen could be seen in intercostal spaces 7–11 but not in the 12th intercostal space. The spleen was seen at the ventral midline in the 8th intercostal space in eight cows and in the 7th intercostal space in 12 cows, although others have reported that the ventral border of the spleen does not extend beyond the costochondral junctions of the 7th and 8th ribs (Nickel et al., 1987). However, depending on the amount of blood the spleen contains, its free ventral margin may extend as far as to the area of the xyphoid (Sto¨ber, 1990). When this happens, the ventral aspect of the reticulum may be indented by the spleen and this should not be mistaken for a pathological finding. In a previous study (Braun and Go¨tz, 1994), the spleen could not be seen in the 7th intercostal space in 3/51 cows, reflecting the variable anatomical position of the spleen (Nickel et al., 1987). The weight of the cows used in the present study ranged widely from 436 to 699 kg. This was due mainly to body condition, which varied from thin to good, and not to the overall size of the cows. We assumed that the large standard deviations of some of the ultrasonographic measurements were due partly to the body condition of the cows and partly to variations in the amount of blood within the spleen.
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Our measurements are likely to be most useful for clinicians with little experience in ultrasonographic examination of the spleen. They can be used to assess whether the extent of the spleen is normal or not. However, in the past 10 years at our clinic, we have not seen any cows with abnormally large or small spleens, although we have examined cows with dilated splenic vessels due to severe splenitis. The primary goal of the present study was to describe the ultrasonographic appearance of the healthy spleen. Abnormal splenic findings, often due to traumatic reticuloperitonitis, are frequently encountered in veterinary practice. We conclude that ultrasonography is a useful tool for the non-invasive examination of the spleen. Its appearance and size in healthy cows can serve as reference values for the diagnosis of pathological changes in the spleen. To date, there are a few reports describing changes in the bovine spleen due to disorders such as traumatic reticuloperitonitis (Braun, 2003; Braun et al., 1993a,b, 1998) although in dogs, tumours, haematoma, atrophy and hypertrophy of the spleen as well as splenic torsion have been diagnosed via ultrasonography (Nyland et al., 2002).
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