NEOPLASIA AND OTHER FORMS OF INTESTINAL OBSTRUCTION

• 1.
  List the possible clinical signs of intestinal neoplasia and/or obstruction (partial or complete) in cats.

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    Vomiting
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    Anorexia/inappetence
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    Gagging/dysphagia (linear foreign body anchored in the mouth)
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    Weight loss/cachexia
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    Diarrhea
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    Tenesmus (with lesion in colon or ileum)
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    Hematochezia (colon or rectum); melena (small intestine)
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    Lack of stool/constipation
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    Dehydration
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    Lethargy/malaise
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    Ascites and/or carcinomatosis
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    Central nervous system (CNS) signs and icterus
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    Palpable abdominal mass (approximately 50% of cases)
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    Rectal prolapse of ileocecal lymphoma mass
• 2. Which clinical findings are most common?

  In most reports, vomiting, anorexia, and weight loss are by far the most common signs, although the order of their prevalence varies. Clinical signs do not necessarily correlate with the location of the tumor in the gastrointestinal (GI) tract with the exception of tenesmus and hematochezia, which occur with colonic or rectal disease. Palpating an abdominal mass is a consistent finding but depends on the practitioner's level of palpation skill. The rest of the clinical findings are less common. Duration of clinical signs before diagnosis can range from days to months. Many cases are treated for clinical signs conservatively before relapse and definitive diagnosis. CNS signs, icterus, and other polysystemic signs may occur in cats with feline infectious peritonitis (see Chapter 38).

• 3. What are the most common differential diagnoses for intestinal obstruction?

  Intestinal neoplasia, foreign body, and intussusception are common causes of intestinal obstruction in cats. Lymphoma is the most common neoplasm. Despite repeated references in current texts to mast cell tumor as the second most common feline GI neoplasm, no current studies focus on this disease. Adenocarcinoma is the most common nonlymphatic/nonhematopoietic neoplasm. Intestinal obstruction due to adenocarcinoma results from an annular ring of tissue created by the solitary tumor. Lymphoma and mast cell tumors may be discrete or diffuse.

  Uncommonly diagnosed GI tract tumors include lipoma, leiomyosarcoma, leiomyoma, globule leukocyte tumor, granulated round cell tumor, fibrosarcoma, carcinoid, osteosarcoma, ganglioneuroma, gastric extramedullary plasmacytoma, and granulated round cell tumor.

  Intussusception most commonly occurs in the ileocecocolic region. Predisposing causes include parasites, foreign body, previous abdominal surgery, viral enteritis, and mural lesions. Many cases, however, are idiopathic.

  Trichobezoar, volvulus, intestinal torsion, incarceration of bowel in a hernia, adhesions, stricture, intramural abscess, granuloma or hematoma, congenital malformations, and feline infectious peritonitis (FIP) are less common causes of GI obstruction. Trichobezoars may form in part because of a lack of interdigestive migrating myoelectric complexes in cats.

• 4. How does FIP cause obstructive disease?

  Noneffusive FIP can create solitary mural intestinal inflammatory lesions. In one study, this presentation predominated in approximately 20% of cats with histopathologically documented FIP. Histologically, the intestine is markedly thickened; multifocal pyogranulomas extend through the wall with areas of necrosis and fibrosis. Presence of coronavirus was confirmed by immunohistochemical staining of the tissues (New York State Veterinary Diagnostic Laboratory, Ithaca, NY). In the 26 cats reported in the study, 76% of obstructions occurred in the colon or at the ileocecocolic junction. Ragdolls and Himalayans may have been overrepresented, but reported numbers are small. Half of the cats were < 1 year of age, 11 of 26 were 1–6 years old, and only 2 of 26 were 11 years old. Most cats died of the disease within 9 months. A few cats had effusions at surgery, but the fluid was not typical for effusive FIP (see Chapter 38).

• 5. What hematologic abnormalities may be seen in cats with intestinal obstruction?

  Hematologic abnormalities are common but generally not specific for any one disease:

  Complete blood cell count. Leukocytosis with or without left shift, monocytosis, and lymphopenia have been detected in some cats. Eosinophilia, basophilia, and thrombocytosis were detected in a cat with lymphoma. Anemia may result from chronic disease, GI blood loss (anemia may be microcytic because of iron deficiency in chronic cases), or bone marrow involvement (feline leukemia virus [FeLV]).

  Serum biochemical panel. Panhypoproteinemia may result from GI blood loss. In some cats, hyperglobulinemia results from chronic inflammatory disease, FIP, or neoplasia. Hyperglycemia, increased activities of liver enzymes, and hypercholesterolemia may occur. Hypochloremic metabolic alkalosis may be seen with pyloric outflow tract obstruction.

  Serology tests. FeLV serum antigen tests are usually negative with adenocarcinoma and occasionally positive with lymphoma. Positive coronavirus titers indicate only exposure to a coronavirus, not FIP (see Chapter 38).

  Serum electrophoresis. Monoclonal gammopathy is most consistent with plasmacytoid neoplasia but is occasionally detected in cats with FIP.

• 6. What imaging studies may be helpful in evaluating intestinal obstruction?

  Plain radiographs may reveal a mass effect, fluid-filled stomach, or intestinal obstructive pattern characterized by gas-filled loops of bowel. Thoracic radiographs rarely reveal metastasis, but findings consistent with aspiration pneumonia may be present.

  Positive contrast radiographs are used to confirm partial or complete obstruction.

  

  Barium series in a cat with adenocarcinoma of the small intestine.

  Ultrasound may be used to document masses localized to the GI tract, thickened bowel loops, enlarged mesenteric lymph nodes, abnormal peristalsis, and intussusceptions. In addition, tissue aspirates for cytology also can be guided by ultrasound.

  Endoscopy/colonoscopy can be used to visualize mass lesions and to obtain biopsies, depending on the location of the abnormality. Biopsies should be done in all patients because diffuse, microscopic disease may be detected on histopathology. Adenocarcinoma may look like stricture or fibrous tissue rather than a mass lesion.

• 7.
  What other diagnostic techniques may be helpful?

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    Exploratory laparotomy is used to confirm and relieve obstructive disease and to obtain tissue for definitive diagnosis.
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    Cytology obtained before surgery or intraoperatively can help to make a definite diagnosis, especially of lymphoma. Aspiration cytology is unreliable for adenocarcinoma.
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    Histology and immunohistochemistry are used to confirm the diagnosis of neoplasia and FIP.
• 8. How are intestinal obstructions treated?

  For most intestinal obstructions, surgery is the mainstay of treatment. Some foreign bodies in the pyloric outflow tract can be removed via endoscopy, but disease in other regions requires surgery. If an intussusception is documented, it should be reduced if the intestine is viable and the primary disease treatable (e.g., foreign body). If the primary disease is neoplasia or the intestine is not viable, resection and anastomosis are indicated. Enteroplication should be considered because the recurrence rate for intussusceptions is as high as 27%. When adenocarcinoma is detected, surgery is the primary treatment (see question 14). When lymphosarcoma is detected, chemotherapy should be used as the primary treatment if possible (see question 18). Most trichobezoars are found in the proximal jejunum to distal ileum.

• 9.
  What preventive methods are used after surgical removal?

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    Administration of emollient laxatives (use petroleum-based products, not mineral oil, to avoid lipid aspiration pneumonia)
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    Attempts to prevent overgrooming (brush frequently, control fleas, and address behavioral problems)
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    Shaving long hair
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    Administration of prokinetic drugs (e.g., metoclopramide)
• 10. What are adenocarcinomas? How common are they?

  Adenocarcinomas are malignant tumors of glandular epithelium that originate from the crypts of Lieberkuhn. They are the most common nonlymphoid neoplasia, accounting for 25–30% of all GI neoplasms. Osseous or chondroid metaplasia occurs in some cases. In one study, luminal stricture occurred in 12 of 44 cats.

• 11. Describe the typical signalment of cats with adenocarcinoma.

  Adenocarcinomas occur most commonly in middle-aged cats (mean age = 8–11 years, range = 2–17 years). Siamese are overrepresented, accounting for 71% of cases (8 times the incidence in other breeds). The disease is more common in females than males.

• 12. Where are most adenocarcinomas located?

  Adenocarcinomas may occur in either the small or large intestine. Up to 70% occur in the small intestine, especially the jejunum. The tumor is uncommon in the duodenum.

• 13. How does metastasis occur? What are the most common sites?

  Adenocarcinomas spread via the lymphatic system. If metastasis occurs, the mesenteric nodes are the most common site (50%), followed by carcinomatosis (29%), lung, and liver.

• 14. What treatment is recommended for adenocarcinoma?

  Surgical resection and anastomosis are the treatment of choice. In one study, administration of adriamycin (1 mg/kg intravenously every 3 weeks for 5–6 treatments) improved median survival time for colonic adenocarcinoma.

• 15. Describe the prognosis for cats with adenocarcinoma.
  Prognosis varies among studies. A major limitation is the small number of reported cases. Notable findings of several studies include:

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    In the study by Birchard, survival after surgery was 7 days (range = 1–13 day) vs. 3 days without surgery.
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    In the study by Kosovsky, cats that lived for > 2 weeks after surgery had a mean survival time of 15 months.
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    In the study by Cribb, the mean survival time after resection and anastamosis was 2.5 months with a range of 0–24 months.
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    In the study by Turk, the mean survival time after surgery was 5 weeks; the median survival time was 20 weeks with a range of 2 days to 2 years.
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    Kosovsky reported survival times of 4.5 and 28 months in two cats that survived surgery but with carcinomatosis.
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    The presence of metastasis is prognostic. According to Cribb, the postoperative mean survival times for cats with and without metastasis were 5 months and 10 months, respectively.
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    Histologic type may be prognostic as in humans. According to Cribb, the mean survival times for tubular, undifferentiated, and mucinous types were 11, 4, and 4 months, respectively.
• 16. What causes intestinal lymphosarcoma?

  Most intestinal lymphosarcomas are of T-cell origin. Feline coronavirus-associated cell membrane antigen (FOCMA) may be causative after exposure to FeLV.

• 17.
  Describe the presentation of intestinal lymphosarcoma.

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    The median age is 12 years (range = 3–18 years).
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    Discrete and diffuse lymphosarcomas occur with equal frequency in the small intestine.
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    Fewer cases occur in the large intestine.
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    Affected cats can be either FeLV-positive or FeLV-negative.
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    Approximately 13% of feline lymphosarcomas are exclusively in the GI tract.
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    Approximately 40% of feline lymphosarcomas metastasize to extra-GI sites.
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    Lymphoblastic lymphosarcoma (59%) is more likely than lymphocytic lymphosarcoma (24%) to present with an abdominal mass.
• 18. How are intestinal lymphosarcomas treated?

  Recommended treatment is discussed in Chapter 68. Recently, the combination of prednisolone with chlorambucil was reported.

• 19.
  Discuss the prognosis for cats with lymphosarcoma.

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    The most consistent prognostic factor is response to therapy. Duration of first remission also correlates directly with survival.
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    A positive FeLV serologic test is a negative prognostic indicator in some studies.
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    Anatomic location does not predict response rate or survival time.
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    Survival ranges from 2–2000+ days. The mean survival time ranges from 50 days to 23 months. Survival time is probably prolonged in a subset of cats.
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    Histologic grade may be prognostic. In one study, the complete remission rates and median survival times for lymphoblastic lymphosarcoma were 18% and 2.7 months, respectively; the corresponding values for lymphocytic lymphosarcoma were 69% and 22.8 months.
• 20. How does colonic neoplasia differ from neoplasia in other areas of the GI tract?

  Colonic neoplasia accounts for 10–15% of GI neoplasms and <1% of all feline neoplasms. The mean age for diagnosis of colonic cancer is 12.5 years, and the median age is 13 years, which is comparable to neoplasia in other areas of the GI tract. Adenocarcinoma is most common, followed by lymphosarcoma and then by mast cell tumors. A few cases of neuroendocrine carcinoma have been reported. Treatment combines surgery and chemotherapy, as discussed for adenocarcinoma and lymphoma of the small intestine.

• 21. Summarize the prognosis for cats with colonic neoplasia.

  PROGNOSTIC FACTOR	ADENOCARCINOMA	LYMPHOSARCOMA	MAST CELL TUMOR
  Received chemotherapy	Doxorubicin with, MST = 280 days without, MST = 56 days	Not prognostic	All 4 cats in study
  			treated with prednisone
  Type of surgery
  Subtotal colectomy	MST = 138 days	Surgery not prognostic, but I cat lived 1355 days	All had surgery, but numbers too small for assessment
  Mass resection	MST= 68 days
  Biopsy	MST= 10 days
  Metastasis	With: MST = 49 days	Not evaluated	Not evaluated
  	Without: MST = 259 days		MST = 199 days for 4 cats

  MST =median survival time.