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Ultrasonography of the small intestine in small animals- Part 2

Amalia Agut, DVM, PhD, Dipl. ECVDI - 15/10/2017

Ultrasonography of the small intestine in small animals - Part 2


 

Intestinal tumorsFigure 11

Lymphomas, adenocarcinomas, and mast cell tumors are the most common intestinal tumors in cats, whereas adenocarcinomas and leiomyomas are more common in dogs. Intestinal fibrosarcomas, hemangiosarcomas, carcinoids, and plasma cell tumors are rare. Clinical signs usually include weight loss and anorexia. Diarrhea, melena, vomiting, abdominal discomfort, abdominal effusion and anemia may also occur. Intussusception and intestinal perforation may occur as a consequence of intestinal tumors (20).

 

The most common ultrasonographic features of intestinal neoplasia are thickening of the bowel wall, loss of its normal layered appearance, and alterations in the contour of the mucosal and/or serosal surfaces (17). Changes associated with intestinal neoplasia are most often focal as a mass-like lesion but can also be diffuse, especially in the case of canine gastrointestinal lymphoma. The mass may be quite variable in appearance. Focal, concentric thickening of the bowel may be present, or the thickening may be eccentric in location. Larger lesions are usually complex, with mixed echogenicity. While it is not difficult to identify large mass lesions, it may be more of a challenge to associate the mass with the bowel. Metastasis to regional lymph nodes and occasionally to the liver or other organs can occur (17).



Lymphoma

Alimentary lymphoma (involving the gastrointestinal tract and/or the mesenteric lymph nodes) is one of the most common sites of occurrence for feline lymphoma (20).

 

In dogs and cats, the most common ultrasonographic findings are a transmural thickening associated with the diffuse loss of normal wall layering, reduced wall echogenicity, decreased localized motility and regional lymph node enlargement (Figures 11A-11C) (21). In cats, alimentary lymphoma can affect the intestinal tract without fully disrupting the wall layering (2).



Adenocarcinomas

Adenocarcinomas are considered the most common gastrointestinal tumor in dogs. The most common ultrasonographic findings are transmural thickening with complete loss of layering, and often with associated lymphadenopathy (Figures 12A-12C). In the majority of these cases, there was evidence of fluid accumulation proximal to the intestinal thickening associated with localized ileus (22).

 

Intestinal carcinoma has similar ultrasonographic appearance to intestinal lymphoma, (20) but the length of the lesion tends to be shorter in carcinoma than lymphoma, and mechanical ileus is more common in carcinoma than in lymphoma. So, these lesions must be biopsied with ultrasonic guidance to provide a definitive diagnosis (2).



Figure 12Smooth muscle tumors

Smooth muscle tumors include leiomyomas, which are the most common benign tumors of the canine gastrointestinal tract, and leiomyosarcomas, which are the most common sarcoma of the gastrointestinal tract (2).

 


Leiomyomas

Leiomyoma are typically found within the stomach of older dogs, although they can occasionally be found in the bowel (20). This tumor is small and has a uniform echogenicity (Figure 13).

Figure 13


Leiomyosarcomas

Leiomyosarcomas are usually seen as large, complex masses. These tumors are originated intramurally and grow out of the serosa as large eccentric, extraluminal masses, or less commonly grow into the bowel lumen. Due to their distribution and large size, it is difficult to assess the anatomic origin of the mass (23). Internally, these masses may have anechoic and hypoechoic foci which may correlate with the areas of necrosis and hemorrhage, accounting for their complex ultrasound appearance (23). Anemia is the most frequent hematological abnormality.

 

Percutaneous ultrasound-guided aspiration or tissue-core biopsy can be performed to confirm the mesenchymal nature of these lesions. However, careful choice of the biopsy path should be made to avoid anechoic cavities and subsequent leakage or hemorrhage (20).

 


Others tumors

Fibrosarcomas, mast cell tumors, hemangiosarcoma, adenomatous polyps and non-functional carcinoid tumors tend to be focally invasive as poorly echogenic masses or as focal thickening with loss of layering. No specific ultrasonographic appearance helps to differentiate the tumors (2), so the ultimate diagnosis of the tumor type must be confirmed by histopathology using an endoscopic, surgical or aspiration/biopsy obtained with ultrasound guidance (20).



Ultrasound-guided biopsy

Fine-needle aspiration or tissue-core biopsies of bowel masses under ultrasound guidance are safe alternative procedures to use instead of endoscopic or surgical biopsy. The main rule is to carefully locate and avoid the lumen, since intestinal content leakage can be a serious complication (2).

You may also be interested in the series of "How To" Ultrasound videos in the "How To - Small" section, CLICK HERE to go there now.

 

This article was kindly provided by Royal Canin, makers of a range of veterinary diets for dogs and cats. For the full range please visit www.RoyalCanin.co.uk or speak to your Veterinary Business Manager:

 

 

REFERENCES

1. Mattoon JS. Gastrointestinal Ultrasonography. In Proceedings, Western Veterinary Conference, Las Vegas 2003.

2. Penninck D.Gastrointestinal tract. In: Penninck D and d´Anjou MA Atlas of Small Animal Ultrasonography. Blackwell Publishing, Iowa. 2008, pp.281-318.

3. Penninck DG, Nyland TG, Kerr LY, et al. Ultrasonographic evaluation of gastrointestinal diseases in small animals. Vet Radiol 1990; 31:134-141.

4. Goggin JM, Biller DS, Debey BM, et al. Ultrasonographic measurement of gastrointestinal wall thickness and the ultrasonographic appearance of the ileocolic region in healthy cats. J Am Anim Hosp Assoc 2000; 36:224-228.

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12. Hoffman KL. Sonographic signs of gastroduodenal linear foreign body in 3 dogs. Vet Radiol 2003; 44: 466-469.

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14. Evans SE, Bonczynski JJ, Broussard JD, et al. Comparison of endoscopic and full-thickness biopsy specimens for diagnosis of inflammatory bowel disease and alimentary tract lymphoma in cats. J Am Vet Med Ass 2006; 229: 1447-1450.

15. Rudorf H, Van Schaik G, O´Brien RT, et al. Ultrasonographic evaluation of the thickness of the small intestinal wall in dogs with inflammatory bowel disease. J Small Anim Pract 2005; 46: 322-326.

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17. Penninck DG, Smyers B, Webster CRL, et al. Diagnostic value of ultrasonography in differentiating enteritis from intestinal neoplasia in dogs. Vet Radiol 2003; 44: 570-575.

18. Sutherland-Smith J, Penninck DG, Keating JH, et al. Ultrasonographic intestinal hyperechoic mucosal striations in dogs are associated with lacteal dilation. Vet Radiol 2007; 48: 51-57.

19. Moon ML, Biller DS, Armbrust LJ. Ultrasonographic appearance and etiology of corrugated small intestine. Vet Radiol 2003; 44: 199-203.

20. Penninck DG. Characterization of gastrointestinal tumors. Vet Clin North Am Small Anim Pract 1998; 28: 777-797.

21. Penninck DG, Moore AS, Tidwell AS, et al. Ultrasonography of alimentary lymphosarcoma in the cat. Vet Radiol Ultrasound 1994; 35: 299-304.

22. Paoloni MC, Penninck DG, Moore AS. Ultrasonographic and clinicopathologic findings in 21 dogs with intestinal adenocarcinoma. Vet Radiol Ultrasound 2002; 43: 562-567.

23. Myers NC, Penninck DG. Ultrasonographic diagnosis of gastrointestinal smooth muscle tumors in the dog. Vet Radiol 1994; 35: 391-397.


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