Subjective: A three-year-old spayed female Malamute presented with a two-day history of vomiting, anorexia and lethargy.
Objective: Physical examination revealed pale mucous membranes and mild cranial abdominal distension. A complete blood count revealed a regenerative anemia, and a blood chemistry profile was normal. Abdominal radiographs showed a midabdominal mass effect. An abdominal ultrasound was performed. The spleen was huge, and filled the entire midabdomen. Representative images of the spleen are shown below.
Figures 1 and 2 and video 1: Sagittal view of the cranial aspect of the spleen. The spleen is enlarged, with an irregular border. The parenchyma has a “lacy” pattern, characterized by an anechoic background, and interspersed hyperechoic, linear densities. The mesentery adjacent and ventral to the spleen is hyperechoic and hyperattenuating. A small amount of free abdominal fluid is seen just cranial to the spleen.
Figure 3: Sagittal view of the splenic hilus. The splenic parenchyma in the perihilar region is hyperechoic and mildly heterogeneous, and the rest of the splenic parenchyma has a hypoechoic, “lacy” pattern. A hyperechoic, triangular region is seen at the hilus and it blends into the hyperechoic, hyperattenuating mesentery seen ventrally. No blood flow was demonstrated with color flow Doppler (not shown) over this region.
Assessment: Differential diagnoses for these splenic changes included a primary splenic torsion or splenic infarction due to thrombosis. Based on the lack of evidence of other severe systemic disease that could contribute to thrombosis and splenic infarction, primary splenic torsion was considered to be most likely in this dog.
Plan: An exploratory laparotomy revealed that he spleen was torsed multiple times around the mesenteric root. The pancreas was wrapped up in the torsed mesentery. The splenic vessels were ligated without untwisting them, and a splenectomy was performed. No splenic masses were appreciated, and the rest of the abdomen appeared normal. The dog recovered uneventfully. Histopathology of the spleen was not done.
Splenic torsion is an uncommon but recognized occurrence in dogs. The tail of the spleen can rotate around its pedicle, resulting in compromised blood flow. It is most common in large, deep-chested breed dogs. The underlying pathogenesis has not been determined. Splenic torsion may occur along with gastric dilatation and volvulus, or it may occur independently. The torsion can be acute or chronic.[1-6]
The ultrasound appearance of splenic torsion has been described and classically includes splenomegaly with a hypoechoic, characteristic “lacy” appearance of the splenic parenchyma. The splenic veins may be dilated, and there is usually a complete lack of flow in them when evaluated with spectral or color flow Doppler.[1-3,5,6] A perihilar, hyperechoic triangle that blends into the surrounding hyperechoic, hyperattenuating adjacent mesentery has been described. All of these changes may not be seen in every case of splenic torsion, and some cases of splenic torsion have been reported to have a normal parenchymal appearance.
A perihilar, hyperechoic triangular density should be differentiated from the more commonly observed benign, splenic myelolipomas. Splenic myelolipomas also occur at the hilus, but do not blend into surrounding hyperechoic mesentery.
The ultrasound changes described above are not pathognomonic for primary splenic torsion, and splenic infarction secondary to a hypercoagulable state and/or severe systemic disease should also be considered when they are seen. The differentiation of the two conditions is important from both a diagnostic and therapeutic standpoint.
Diseases reported to be present in splenic infarction cases include infectious disease, immune disease, endocrine disease, renal disease, cardiac disease, neoplastic disease and prior abdominal surgery. In one retrospective study, the relationship between the above diseases, the coagulation abnormalities and the splenic changes were not recognized until after surgery or death. The abnormal spleen was often assessed as the source of the disease rather than a consequence.
An exploratory laparotomy and splenectomy will likely cure a dog with a splenic torsion, thus surgery is the treatment of choice. However, splenic infarction cases often do poorly during surgery and may even die postoperatively. The clinical approach of defining the underlying disease(s) and addressing the hypercoagulable state would be more appropriate in these dogs.
In the dog in this case report, there was no indication of underlying disease, thus an exploratory laparotomy and splenectomy were performed. Optimally, histopathology of the spleen would have been performed to rule out underlying infiltrative disease.
- Hecht S. Spleen. In Atlas of Small Animal Ultrasonography, Penninck D and d’Anjou MA eds, Blackwell Publishing, Ames, Iowa, 2008, pp 263-280.
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- Mai W. The hilar perivenous hyperechoic triangle as a sig of acute splenic torsion in dogs. Vet Radiol Ultrasound 2006;47:487-491.
- Saunders HM, Neath PJ, Brockman DJ. B-mode and Doppler ultrasound imaging of the spleen with canine splenic torsion: A retrospective evaluation. Vet Radiol Ultrasound 1998;39:349-353.
- Weber NA. Chronic primary splenic torsion with peritoneal adhesions in a dog: Case report and literature review. J Am Anim Hosp Assoc 2000;36:390-4.
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- Hardie EM, Vaden SL, Spaulding K, Malarkey DE. Splenic infarction in 16 dogs: A retrospective study. J Vet Intern Med 1995;9:141-148.