History
A 10-year-old castrated male Maine Coon cat was presented because of a 4-day history of constipation and recent hyporexia and vomiting. Because of the cat’s temperament, the cat was sedated for physical examination. The patient had a high rectal temperature (39.9 °C; reference range, 37.8 to 39.2 °C). A gallop murmur was auscultated. The abdomen was soft, and palpation of it did not elicit signs of pain; however, the colon was thought to have been distended with a large amount of feces. No fluid wave, organomegaly, or masses were palpated. A CBC revealed a moderate, nonregenerative hyperchromatic Heinz body anemia with ghost cells (HCT, 20%; reference range, 30% to 50%). Serum biochemical analyses revealed high alkaline phosphatase activity (91 U/L; reference range, 10 to 79 U/L) and total bilirubin concentration (0.5 mg/dL; reference range, 0.1 to 0.3 mg/dL). Two-view abdominal radiographic images were obtained (Figure 1).
Ventrodorsal (A) and right lateral (B) radiographic images of the abdomen of a 10-year-old castrated Maine Coon cat that was presented because of a 4-day history of constipation, hyporexia, and vomiting.
Citation: Journal of the American Veterinary Medical Association 260, 14; 10.2460/javma.22.04.0174
Diagnostic Imaging Findings and Interpretation
On radiographic images of the abdomen, a moderate volume of heterogeneous fecal material was noted in the descending colon (Figure 2). The ascending and transverse colon were not definitively identified. Ventral to the descending colon in the mid to caudal regions of the abdomen, there was a severely distended coiled loop of intestine containing a large volume of heterogeneous, granular soft tissue and mineral opaque material. This intestinal segment measured up to 5.0 cm in diameter and had a U shape on the ventrodorsal view. There was an impression of focal wall thickening along the cranioventral margin of this segment that measured up to 1.6 cm thick. These findings were compatible with chronic partial obstruction of the small intestine, likely secondary to wall thickening. The remainder of the small intestines were gas filled and appeared radiographically normal in diameter. The liver was also mildly enlarged.
Same images as in Figure 1. In the mid to caudal regions of the abdomen is a severely distended tubular structure (black arrows), likely representing a long segment of small intestine. The tubular structure contains a large volume of heterogeneous granular and mineral opaque material. Along the cranioventral margin of this structure is the impression of focal wall thickening measuring up to 1.6 cm thick (white arrow). There is a moderate volume of heterogeneous fecal material in the descending colon (asterisk).
Citation: Journal of the American Veterinary Medical Association 260, 14; 10.2460/javma.22.04.0174
Abdominal ultrasonography was performed for further evaluation. At the level of the ileocecocolic junction (ICJ) involving the cecum, ascending colon, and distal portion of the ileum, a heterogeneous circumferential transmural wall thickening with altered wall layering was identified (Figure 3). This annular thickening resulted in marked narrowing of the lumen at the ileocolic junction. The ileum and distal jejunum were severely distended with granular, hyperechoic shadowing material consistent with retained ingesta. There was mild regional steatitis and anechoic peritoneal effusion. These changes were most consistent with neoplasia (differential diagnosis of carcinoma or less likely round cell) causing a chronic partial mechanical obstruction. Mild nonspecific hyperechoic hepatomegaly was also noted.
Abdominal ultrasonographic image of the same cat, revealing that the ileocolic junction (arrow), cecum (Ce), and ascending colon (arrowhead) have been infiltrated by a heterogeneously echogenic circumferential transmural wall-thickening mass. The mass cannot be cleanly outlined and differentiated from these affected structures and has secondarily caused a partial mechanical obstruction, resulting in retained material in the small intestine (asterisk).
Citation: Journal of the American Veterinary Medical Association 260, 14; 10.2460/javma.22.04.0174
Treatment and Outcome
Results of cytologic examination of ultrasound-guided fine-needle aspirate samples of the ICJ wall thickening were nondiagnostic. Exploratory laparotomy was performed, and the ICJ thickening and colic lymph nodes were resected. The distended distal portion of the small intestine was also resected due to concern for atony. A liver biopsy, mesenteric lymph node biopsy, and bile sample were also collected. The patient recovered from the exploratory laparotomy and was sent home for further monitoring and care.
Histology revealed an intestinal adenocarcinoma with colic lymph node metastasis. There was no evidence of metastasis in the mesenteric lymph node. Results for the liver biopsy sample were consistent with hepatic lipidosis. Results were negative for bacterial culture performed on a sample of bile. The owners declined follow-up care by the oncology service. One month postoperatively, the owners reported via telephone that the patient was eating, more playful, and doing well overall.
Comments
Findings on radiographic images of the cat of the present report indicated chronic partial obstruction of the distal small intestine with secondary retention of ingesta. Although the dilated section of the digestive tract appeared at first glance to have been the colon filled with feces, the location, length, and course of this loop indicated a small intestinal origin. In addition, the radiographically normal descending colon filled with feces was visualized as a separate structure dorsal to the distended loop. Focal wall thickening at the cranioventral margin of the distended intestine was suspected, as the lumen was outlined by the contrasting opacity of the intestinal contents; however, the judgment of intestinal wall thickness on radiographic images can be inaccurate and should be fully investigated by use of ultrasonography for definitive diagnosis.1
The most common radiographic sign of a complete mid small intestinal mechanical obstruction is dilation of bowel loops orad to the site of obstruction with normal or collapsed loops distal to the obstruction.1 With a chronic partial obstruction of the distal portion of the small intestine, the maximum distention occurs just proximal to the location of the obstruction, with the diameter of the intestine orad to it progressively decreasing.2 The duodenum and proximal portion of the jejunum in this case were within normal limits for diameter, as the obstruction was not complete. A gravel sign can be seen in chronic partial obstructions due to the retention of food particles that become trapped proximal to the obstruction.1 The hallmark of a gravel sign is visualization of accumulated particulate mineral opaque material proximal to the obstructing lesion.1 Desiccated retained ingesta can resemble feces and is a reliable sign of chronic partial obstruction of the distal portion of the small intestine.1 Although radiography did not reveal the classic gravel sign with a focal accumulation of mineral just proximal to the obstructive lesion in the cat of the present report, there was diffusely distributed mineral opaque granular material seen within the impacted intestine.
Feline intestinal neoplasia is relatively uncommon, accounting for 5% (1,302/26,043) of all feline neoplasms in 1 study.3 The most common types of intestinal neoplasia in cats are lymphoma, adenocarcinoma, and mast cell tumor.4 Lymphoma is the most common feline intestinal neoplasm (619/1,125 [54.8%]), with the majority being found in the small intestine (119/150 [79.3%]).3 Adenocarcinoma is the second most common feline intestinal neoplasm (356/1,129 [31.5%]) and most often occurs in the large intestine (98/143 [68.5%]).3 Adenocarcinoma is the most common tumor of the large intestine in cats (98/172 [57%]).3
Ultrasonographically, adenocarcinoma typically appears as concentric transmural heterogeneous to hypoechoic thickening with loss of wall layering and regional lymphadenopathy.4,5 Lymphoma can also appear as a solitary mass with transmural loss of wall layering and regional lymphadenopathy but is usually hypoechoic rather than mixed in echogenicity.5 Intestinal lymphoma can also cause diffuse wall thickening with normal wall layering or with thickening of the muscularis layer similar to inflammatory bowel disease.4 Adenocarcinoma is often solitary, as opposed to lymphoma, which can be focal, multifocal, or diffuse.4 Mechanical ileus commonly occurs with intestinal carcinoma due to stenosis of the lumen and does not occur as often with lymphoma.4 Despite these potential differences, histopathology is necessary for definitive diagnosis due to overlap in ultrasonographic features.4 For the cat of the present report, adenocarcinoma was prioritized over lymphoma on the basis of ultrasonographic findings, as the lesion was solitary, mixed in echogenicity, and partially obstructive.
Acknowledgments
No external funding was used in this case, and the authors declare that there were no conflicts of interest.
References
- 1. ↑
Riedesel EA. Small bowel. In: Thrall DE, ed. Textbook of Veterinary Diagnostic Radiology. 7th ed. Elsevier; 2018:926–954.
- 2. ↑
O’Brien TR, Biery DN, Park RD, Bartels JE. Small intestine. In: O’Brien TR, ed. Radiographic Diagnosis of Abdominal Disorders in the Dog and Cat: Radiographic Interpretation, Clinical Signs, Pathophysiology. WB Saunders Co; 1978:275–352.
- 3. ↑
Rissetto K, Villamil JA, Selting KA, Tyler J, Henry CJ. Recent trends in feline intestinal neoplasia: an epidemiologic study of 1,129 cases in the veterinary medical database from 1964 to 2004. J Am Anim Hosp Assoc. 2011;47(1):28–36. doi:10.5326/JAAHA-MS-5554
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Gaschen L. Ultrasonography of small intestinal inflammatory and neoplastic diseases in dogs and cats. Vet Clin North Am Small Anim Pract. 2011;41(2):329–344. doi:10.1016/j.cvsm.2011.01.002
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Rivers BJ, Walter PA, Feeney DA, Johnston GR. Ultrasonographic features of intestinal adenocarcinoma in five cats. Vet Radiol Ultrasound. 1997;38(4):300–306. doi:10.1111/j.1740-8261.1997.tb00859.x
