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Liver and Spleen
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C h a p t e r
4 3
Liver and Spleen
III LIVER Radiographing the liver to determine whether or not it is diseased “boils down” to three things: it is too large, too small, or misshapen. Occasionally density discrepancies—gas, mineral, metal—suggest disease, but such findings are rare. In short, hepatic radiology is for the most part unrewarding. Hepatic ultrasound, on the other hand, can be quite revealing, although as with any examination of something as large as the liver, it is often time consuming and technically challenging. As in the case of pet animals, the diagnostic benefits of ultrasound in foals and horses tend to be exaggerated. Although few will dispute the capability of ultrasound to identify a large hepatic mass, such as an abscess or tumor or a cirrhotic liver bathed in peritoneal fluid, it is quite another proposition to diagnose a diffuse liver disease like hepatitis, at least with any degree of certainty (Figure 43-1). This is not to say that hepatic ultrasound is a waste of time—hardly—but one’s diagnostic expectations should be realistic: localized and regional liver diseases are detectable, provided the available equipment is capable of clearly detecting them and the examiner has the ability to recognize the diseased portion of the liver once it is encountered. Second, all but the most severe of diffuse liver diseases are very difficult to recognize sonographically.
III SPLEEN Like the liver, the radiographic pursuit of splenic disease is often an exercise in futility; but the sonographic search for disease can be quite rewarding, given the close proximity of much of the spleen to the surface of the left paralumbar fossa. 544
III NONSPECIFIC SONOGRAPHIC FINDINGS IN HORSES WITH LIVER DISEASE Durham and co-workers reported multiple, nonspecific sonographic findings in horses with a variety of liver diseases, including those that caused one or more of the following pathologic abnormalities: (1) moderate fibrosis, (2) moderate or severe biliary hyperplasia, and (3) severe hemosiderosis (Box 43-1).1
Hepatic Abscess Sellon and co-workers reported liver abscesses in three horses.2 Clinically, the animals had histories of weight loss, fever, inappetence, and depression. Sonographically, there was no characteristic appearance. The observed lesions were of mixed echogenicity, with or without gas and fluid pockets. Other hepatic diseases, including (1) tumor, (2) granuloma, (3) infarction, and (4) hemorrhage, also share some of these sonographic features.
Cholelithiasis Cholelithiasis is more common in horses than in any other domestic species and is the leading cause of biliary obstruction. Traub and co-workers described cholelithiasis in four horses, two of which were examined sonographically because of abdominal pain and laboratory evidence of biliary obstruction. The other two cases were incidental necropsy findings.3 Brandon and Stanley also reported the sonographic diagnosis of bile stones (choleliths) in an icteric 9-year-old Quarter Horse.4 Reef and co-workers reported cholelithiasis in eight horses, emphasizing the sonographic aspects of the disease, particularly the biliary congestion that often accompanies cholelithiasis.5
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Assessing Bile Flow (Biliary Kinetics)
Pyrrolizidine Alkaloid Poisoning
Hornof and Baker described the scintigraphic technique and normal values for evaluating biliary kinetics in the horse6 (Table 43-1).
In the Pacific Northwest, consumption of Senecio plant species, which contain pyrrolizidine alkaloids, can cause liver failure in horses.8 Unfortunately there are no consistently reliable sonographic disease indicators.
Hepatic Tumor Lennox reported the sonographic appearance of a hepatoblastoma in a 2 1/2 -year-old Thoroughbred filly hospitalized for lethargy, anorexia, and weight loss. Sonographically, the lesion was characterized by numerous closely packed, echogenic foci, which obliterated the normal echotexture of the liver.7
III SPLEEN Nephrosplenic (Renosplenic) Entrapment The sonographic diagnosis of nephrosplenic entrapment is different from most other methods because a positive diagnosis is predicated on what is not seen rather than what is. The scan necessary to confirm or deny the presence of nephrosplenic entrapment is performed high in the left paralumbar fossa. A positive diagnosis is based on the absence of either the spleen or left kidney and, in its stead, reverberation artifact caused by gas-filled intestine (Figure 43-2). A negative examination is heralded by the presence of a normal spleen and left kidney (Figure 43-3). Although some published reports describing the sonographic features of nephrosplenic entrapment leave the impression that the diagnosis is quite straightforward, this is not always the case. For example, either the spleen or the kidney may appear in the left lumbar fossa but without its companion organ, suggesting, but failing to confirm, the diagno-
B o x
4 3 - 1
Nonspecific Sonographic Abnormalities Found in Horses With Diseased Livers
Figure 43-1 • Normal-appearing hepatic sonogram in a horse with diffuse hepatitis illustrates the limitations of ultrasound in diagnosing diffuse liver disease.
Generalized increased echogenicity Focal increase in echogenicity Generalized decreased echogenicity Focal decrease in echogenicity Decreased size (hepatic atrophy) Increased size (hepatomegaly) Increased vascular size (vascular congestion) Rounded or blunted liver margins
Table 43–1 • NORMAL BILIARY ACTIVITY LEVELS* Parameter
Fed Horses
Maximum hepatic activity
Reached within 10 min in all instances. In fed horses, reached 50% of maximum activity in 26 min ± 5 min Reached within 15 min in fed horses, ± 4 min 21 min in fed horses ± 5 min
Maximum activity within bile duct Time from injection to 50% maximum activity *As determined using
99m
Tc-labeled disofenin.
Unfed Horses In unfed horses, reached 50% of maximum activity in 36 min ± 14 min Reached within 18 min in unfed horses ± 6 min 30 min in unfed horses ± 7
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SECTION VII III The Abdomen
Figure 43-2 • Sonogram obtained from the left paralumbar fossa of a horse with nephrosplenic entrapment shows characteristic reverberation artifacts caused by an air-filled bowel segment.
Figure 43-4 • Sonogram obtained from the left paralumbar fossa of a horse with suspected nephrosplenic entrapment shows the cranial aspect of the spleen surrounded by air-filled bowel segments on three sides.
Figure 43-3 • Sonogram obtained from the left paralumbar fossa of a horse with suspected nephrosplenic entrapment shows a normal spleen and left kidney, which denies the diagnosis.
Figure 43-5 • Sonogram from a horse with hemangiosar-
sis (Figure 43-4). I encounter this sort of diagnostic ambiguity with regularity, perhaps as much as 20 to 25 percent of the time, particularly after a horse has been rolled in an effort to correct an entrapment. In instances in which there is a discrepancy between what was palpated and what was seen sonographically, I recommend that the left paralumbar fossa be rescanned while the horse is being repalpated. The palpater’s moving fingers can be seen readily in the ultrasound beam, often clarifying any question about what is being palpated.
coma shows characteristic cavitary lesion (emphasis zone) within a larger splenic mass.
Splenic Tumors Splenic hemangiosarcoma usually appears as one or more variably marginated cavitary masses, often accompanied by peritoneal hemorrhage (Figures 43-5 and 43-6). Hance and co-workers described the sonographic appearance of presumed metastatic lymphosarcoma in
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References
Figure 43-6 • Sonogram obtained from the horse shown in Figure 43-5 shows a normal portion of the animal’s cancerous spleen surrounded by blood leaked from the tumor.
the spleen of a 4-year-old Quarter Horse gelding.9 The splenic lesions appeared raised, well circumscribed, and hypoechoic. The spleen was enlarged overall, and there was a small volume of clear peritoneal fluid.
1. Durham AE, Newton JR, et al: Retrospective analysis of histological, clinical, ultrasonographic, serum biochemical, and hematological data in prognostic evaluation of equine liver disease, Equine Vet J 35:542, 2003. 2. Sellon DC, Spaulding K, et al: Hepatic abscesses in three horses, J Am Vet Med Assoc 216:882, 2000. 3. Traub JL, Rantanen N, et al: Cholelithiasis in four horses, J Am Vet Med Assoc 181:59, 1982. 4. Brandon B, Stanley C: What is your diagnosis? J Am Vet Med Assoc 222:289, 2003. 5. Reef VR, Johnston JK, et al: Ultrasonic findings in horses with cholelithiasis: eight cases (1985-1987), J Am Vet Med Assoc 196:1836, 1990. 6. Hornof WJ, Baker DG: Biliary kinetics of horses as determined by quantitative nuclear scintigraphy, Vet Radiol 27:85, 1986. 7. Lennox TJ, Wilson JH, et al: Hepatoblastoma with erythrocytosis in a young female horse, J Am Vet Med Assoc 216:718, 2000. 8. Pearson EG: Liver failure attributable to pyrrolizidine alkaloid toxicosis and associated with inspiratory dyspnea in ponies: three cases (1982-1988), J Am Vet Med Assoc 198:1651, 1991. 9. Hance SR, Shiroma JT, Bertone JJ: Ultrasonic diagnosis, Vet Radiol 33:101, 1992.
C h a p t e r
4 3
Liver and Spleen
III LIVER Radiographing the liver to determine whether or not it is diseased “boils down” to three things: it is too large, too small, or misshapen. Occasionally density discrepancies—gas, mineral, metal—suggest disease, but such findings are rare. In short, hepatic radiology is for the most part unrewarding. Hepatic ultrasound, on the other hand, can be quite revealing, although as with any examination of something as large as the liver, it is often time consuming and technically challenging. As in the case of pet animals, the diagnostic benefits of ultrasound in foals and horses tend to be exaggerated. Although few will dispute the capability of ultrasound to identify a large hepatic mass, such as an abscess or tumor or a cirrhotic liver bathed in peritoneal fluid, it is quite another proposition to diagnose a diffuse liver disease like hepatitis, at least with any degree of certainty (Figure 43-1). This is not to say that hepatic ultrasound is a waste of time—hardly—but one’s diagnostic expectations should be realistic: localized and regional liver diseases are detectable, provided the available equipment is capable of clearly detecting them and the examiner has the ability to recognize the diseased portion of the liver once it is encountered. Second, all but the most severe of diffuse liver diseases are very difficult to recognize sonographically.
III SPLEEN Like the liver, the radiographic pursuit of splenic disease is often an exercise in futility; but the sonographic search for disease can be quite rewarding, given the close proximity of much of the spleen to the surface of the left paralumbar fossa. 544
III NONSPECIFIC SONOGRAPHIC FINDINGS IN HORSES WITH LIVER DISEASE Durham and co-workers reported multiple, nonspecific sonographic findings in horses with a variety of liver diseases, including those that caused one or more of the following pathologic abnormalities: (1) moderate fibrosis, (2) moderate or severe biliary hyperplasia, and (3) severe hemosiderosis (Box 43-1).1
Hepatic Abscess Sellon and co-workers reported liver abscesses in three horses.2 Clinically, the animals had histories of weight loss, fever, inappetence, and depression. Sonographically, there was no characteristic appearance. The observed lesions were of mixed echogenicity, with or without gas and fluid pockets. Other hepatic diseases, including (1) tumor, (2) granuloma, (3) infarction, and (4) hemorrhage, also share some of these sonographic features.
Cholelithiasis Cholelithiasis is more common in horses than in any other domestic species and is the leading cause of biliary obstruction. Traub and co-workers described cholelithiasis in four horses, two of which were examined sonographically because of abdominal pain and laboratory evidence of biliary obstruction. The other two cases were incidental necropsy findings.3 Brandon and Stanley also reported the sonographic diagnosis of bile stones (choleliths) in an icteric 9-year-old Quarter Horse.4 Reef and co-workers reported cholelithiasis in eight horses, emphasizing the sonographic aspects of the disease, particularly the biliary congestion that often accompanies cholelithiasis.5
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545
Assessing Bile Flow (Biliary Kinetics)
Pyrrolizidine Alkaloid Poisoning
Hornof and Baker described the scintigraphic technique and normal values for evaluating biliary kinetics in the horse6 (Table 43-1).
In the Pacific Northwest, consumption of Senecio plant species, which contain pyrrolizidine alkaloids, can cause liver failure in horses.8 Unfortunately there are no consistently reliable sonographic disease indicators.
Hepatic Tumor Lennox reported the sonographic appearance of a hepatoblastoma in a 2 1/2 -year-old Thoroughbred filly hospitalized for lethargy, anorexia, and weight loss. Sonographically, the lesion was characterized by numerous closely packed, echogenic foci, which obliterated the normal echotexture of the liver.7
III SPLEEN Nephrosplenic (Renosplenic) Entrapment The sonographic diagnosis of nephrosplenic entrapment is different from most other methods because a positive diagnosis is predicated on what is not seen rather than what is. The scan necessary to confirm or deny the presence of nephrosplenic entrapment is performed high in the left paralumbar fossa. A positive diagnosis is based on the absence of either the spleen or left kidney and, in its stead, reverberation artifact caused by gas-filled intestine (Figure 43-2). A negative examination is heralded by the presence of a normal spleen and left kidney (Figure 43-3). Although some published reports describing the sonographic features of nephrosplenic entrapment leave the impression that the diagnosis is quite straightforward, this is not always the case. For example, either the spleen or the kidney may appear in the left lumbar fossa but without its companion organ, suggesting, but failing to confirm, the diagno-
B o x
4 3 - 1
Nonspecific Sonographic Abnormalities Found in Horses With Diseased Livers
Figure 43-1 • Normal-appearing hepatic sonogram in a horse with diffuse hepatitis illustrates the limitations of ultrasound in diagnosing diffuse liver disease.
Generalized increased echogenicity Focal increase in echogenicity Generalized decreased echogenicity Focal decrease in echogenicity Decreased size (hepatic atrophy) Increased size (hepatomegaly) Increased vascular size (vascular congestion) Rounded or blunted liver margins
Table 43–1 • NORMAL BILIARY ACTIVITY LEVELS* Parameter
Fed Horses
Maximum hepatic activity
Reached within 10 min in all instances. In fed horses, reached 50% of maximum activity in 26 min ± 5 min Reached within 15 min in fed horses, ± 4 min 21 min in fed horses ± 5 min
Maximum activity within bile duct Time from injection to 50% maximum activity *As determined using
99m
Tc-labeled disofenin.
Unfed Horses In unfed horses, reached 50% of maximum activity in 36 min ± 14 min Reached within 18 min in unfed horses ± 6 min 30 min in unfed horses ± 7
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SECTION VII III The Abdomen
Figure 43-2 • Sonogram obtained from the left paralumbar fossa of a horse with nephrosplenic entrapment shows characteristic reverberation artifacts caused by an air-filled bowel segment.
Figure 43-4 • Sonogram obtained from the left paralumbar fossa of a horse with suspected nephrosplenic entrapment shows the cranial aspect of the spleen surrounded by air-filled bowel segments on three sides.
Figure 43-3 • Sonogram obtained from the left paralumbar fossa of a horse with suspected nephrosplenic entrapment shows a normal spleen and left kidney, which denies the diagnosis.
Figure 43-5 • Sonogram from a horse with hemangiosar-
sis (Figure 43-4). I encounter this sort of diagnostic ambiguity with regularity, perhaps as much as 20 to 25 percent of the time, particularly after a horse has been rolled in an effort to correct an entrapment. In instances in which there is a discrepancy between what was palpated and what was seen sonographically, I recommend that the left paralumbar fossa be rescanned while the horse is being repalpated. The palpater’s moving fingers can be seen readily in the ultrasound beam, often clarifying any question about what is being palpated.
coma shows characteristic cavitary lesion (emphasis zone) within a larger splenic mass.
Splenic Tumors Splenic hemangiosarcoma usually appears as one or more variably marginated cavitary masses, often accompanied by peritoneal hemorrhage (Figures 43-5 and 43-6). Hance and co-workers described the sonographic appearance of presumed metastatic lymphosarcoma in
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References
Figure 43-6 • Sonogram obtained from the horse shown in Figure 43-5 shows a normal portion of the animal’s cancerous spleen surrounded by blood leaked from the tumor.
the spleen of a 4-year-old Quarter Horse gelding.9 The splenic lesions appeared raised, well circumscribed, and hypoechoic. The spleen was enlarged overall, and there was a small volume of clear peritoneal fluid.
1. Durham AE, Newton JR, et al: Retrospective analysis of histological, clinical, ultrasonographic, serum biochemical, and hematological data in prognostic evaluation of equine liver disease, Equine Vet J 35:542, 2003. 2. Sellon DC, Spaulding K, et al: Hepatic abscesses in three horses, J Am Vet Med Assoc 216:882, 2000. 3. Traub JL, Rantanen N, et al: Cholelithiasis in four horses, J Am Vet Med Assoc 181:59, 1982. 4. Brandon B, Stanley C: What is your diagnosis? J Am Vet Med Assoc 222:289, 2003. 5. Reef VR, Johnston JK, et al: Ultrasonic findings in horses with cholelithiasis: eight cases (1985-1987), J Am Vet Med Assoc 196:1836, 1990. 6. Hornof WJ, Baker DG: Biliary kinetics of horses as determined by quantitative nuclear scintigraphy, Vet Radiol 27:85, 1986. 7. Lennox TJ, Wilson JH, et al: Hepatoblastoma with erythrocytosis in a young female horse, J Am Vet Med Assoc 216:718, 2000. 8. Pearson EG: Liver failure attributable to pyrrolizidine alkaloid toxicosis and associated with inspiratory dyspnea in ponies: three cases (1982-1988), J Am Vet Med Assoc 198:1651, 1991. 9. Hance SR, Shiroma JT, Bertone JJ: Ultrasonic diagnosis, Vet Radiol 33:101, 1992.