History
A 5-year-old 25-kg (55-lb) spayed female Standard Poodle was referred because of acute onset of lethargy and regenerative anemia. One week earlier, the patient had been evaluated by the referring veterinarian for a 1-week history of intermittent vomiting, diarrhea, and listlessness.
Findings on physical examination at the time of referral were unremarkable. A high mean arterial blood pressure of 198 mm Hg (reference range, 80 to 120 mm Hg) was attributed to patient anxiety. Hematologic evaluation revealed normocytic, normochromic anemia with anisocytosis and an Hct of 29% (reference range, 36% to 60%). Neutrophilic leukocytosis with a total WBC count of 61.5 × 109 cells/L (reference range, 4.00 × 109 WBCs/L to 15.5 × 109 WBCs/L) and a neutrophil count of 59.0 × 109 neutrophils/L (reference range, 2.0 × 109 neutrophils/L to 10.6 × 109 neutrophils/L) was also noted. Serum biochemical analysis revealed mild increases in total bilirubin concentration (0.5 mg/dL; reference range, 0.1 to 0.3 mg/dL) and alkaline phosphatase activity (204 U/L; reference range, 5 to 131 U/L). Findings on abdominal radiography were unremarkable. Abdominal ultrasonography with a 6.0- to 8.0-MHz transducer was performed (Figure 1).
Sagittal ultrasonographic images (A and B) of the spleen of a 5-year-old spayed female Standard Poodle that underwent abdominal ultrasonography because of a 1-week history of intermittent vomiting, diarrhea, and listlessness.
Citation: Journal of the American Veterinary Medical Association 242, 11; 10.2460/javma.242.11.1481
Diagnostic Imaging Findings and Interpretation
Subjective splenic enlargement with severely decreased parenchymal echogenicity and coarse, lacy echotexture is evident. Multiple parallel echogenic lines are present throughout the parenchyma. The splenic veins appear moderately dilated (Figure 2).
Same ultrasonographic images as in Figure 1. Multiple parallel echogenic lines (arrows) are evident in both images. A—Notice that the parenchyma of the spleen has a coarse, lacy echotexture (asterisk). The echogenicity of the splenic parenchyma is considered decreased from normal. B—Splenic veins appear dilated (arrowheads).
Citation: Journal of the American Veterinary Medical Association 242, 11; 10.2460/javma.242.11.1481
Color flow Doppler ultrasonography of the spleen was performed; a lack of blood flow was identified at the hilus, within the parenchyma, and in the surrounding vasculature (Figure 3). A well-defined echogenic, irregularly shaped structure was present within the lumen of the anechoic splenic vein (Figure 4).
A sagittal color flow Doppler ultrasonographic image of the spleen and splenic vein of the same dog as in Figure 1. Notice the lack of blood flow within the splenic vein and the splenic parenchyma. Diffuse hypoechogenicity of the spleen with coarse, lacy echotexture (asterisk) and multiple parallel echogenic lines (arrows) throughout the parenchyma are evident. There is also subjective moderate dilation of the splenic vein.
Citation: Journal of the American Veterinary Medical Association 242, 11; 10.2460/javma.242.11.1481
A sagittal ultrasonographic image of the spleen and splenic vein of the same dog as in Figure 1. The lumen of the subjectively dilated splenic vein is occupied by a structure that is isoechoic to the surrounding mesentery (arrowheads).
Citation: Journal of the American Veterinary Medical Association 242, 11; 10.2460/javma.242.11.1481
Free peritoneal fluid and gas had not been observed radiographically and was not found on ultrasonographic evaluation of the abdomen. Except for the splenic findings, the remainder of the abdominal viscera appeared ultrasonographically normal. Differential diagnoses included splenic infarction, splenic torsion, and splenic neoplasia such as lymphoma. Thrombus or embolus of the splenic vein was highly suspected.
Treatment and Outcome
Exploratory celiotomy was performed. Gross evaluation revealed a twisted splenic vascular pedicle. The spleen was dark, congested, and engorged. No other abnormalities were identified. Ligation of the splenic pedicle and splenectomy were performed. Prophylactic gastropexy was performed. No postoperative complications were observed. Recovery was uneventful, and progressive improvement was noted in the days following surgery. The dog was discharged from the hospital 3 days later.
Comments
Cases of acute splenic torsion are usually accompanied by severe systemic signs of illness, such as acute abdomen and shock. Chronic splenic torsion is associated with more nonspecific signs, such as vomiting, lethargy, anorexia, and icterus.1 For the dog of the present report, clinical history and laboratory abnormalities were indicative of the chronic form of splenic torsion. The incidence of splenic torsion in dogs is unknown. Surgical correction has a good success rate, with a survival rate of 79%.2
Radiographic features of splenic torsion include splenomegaly and atypical location with an acquired C-shape or mass effect appearance with or without emphysematous changes from gas-producing bacteria.3 The dog of the present report did not have these radiographic findings, but retrospective review of the abdominal radiographs revealed that the small intestines were slightly displaced caudally and the body of the spleen was more prominent than typical. These subtle but initially overlooked findings were consistent with enlargement of the spleen.
Ultrasonographic characteristics of splenic torsion include a markedly enlarged spleen with diffuse anechoic areas representing dilated sinusoids. Multiple parallel echogenic lines within the parenchyma represent severely dilated vessels. The splenic veins near the hilum are also enlarged from venous outflow obstruction, and free abdominal fluid may be present adjacent to the spleen.4 In addition, a perivenous hyperechoic triangle of mesenteric fat seen at the hilus has been reported in acute cases.5 In most cases, there is progressive splenic enlargement, with decreased or no blood flow. The ultrasonographic appearance of the splenic parenchyma as well as echogenicity changes with evolving congestion, hemorrhage, or infarction.6 In the dog of the present report, the echogenic thrombus within the dilated splenic vein was due to a change in blood flow within the vessel or a coagulopathy.6 Findings on abdominal radiography were inconclusive, and ultrasonographic evaluation of the abdomen was the most valuable diagnostic modality in determining the diagnosis.
This case demonstrates the clinical value of diagnostic ultrasonography and highlights the importance of use of color flow Doppler ultrasonography when evaluating organs. Color flow Doppler ultrasonography allows evaluation of blood flow and direction within tissues in real time. Standard grayscale ultrasonography operates on the pulse-echo principle. Sound is produced by the transducer, and echoes return to the transducer after interaction with tissue. Color flow Doppler ultrasonography allows for the pulse-echo principle to include Doppler-shifted echoes that denote blood flow or tissue motion shown in color.7 This information is presented superimposed on the grayscale anatomic image. If an echo returns to the transducer with a different frequency than what was emitted, a Doppler shift has occurred that was caused by object movement. In vascular ultrasonography, the moving objects are RBCs. Color is indicative of RBC motion toward or away from the transducer. Color flow Doppler ultrasonography is angle dependent and will not display color at vessel angles of 90° to the transducer because of a lack of a Doppler shift at this angle. For the dog of the present report, color flow Doppler ultrasonography was performed from multiple angles to confirm lack of blood flow to the spleen. The inability to detect blood flow within the splenic parenchyma or splenic veins of the dog was consistent with ischemia of the spleen.
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