The vomiting and/or diarrhoeic cancer patient

9 The vomiting and/or diarrhoeic cancer patient

Vomiting is the active expulsion of material from within the stomach and/or upper small intestine. Vomiting should always be differentiated from regurgitation either by careful history evaluation or by direct observation. Vomiting usually causes a prodromal nausea (characterized by salivation, lip licking, appearing anxious or pacing) and then usually proceeds to retching, whilst a regurgitating patient does not usually exhibit these features. Vomiting also usually involves visible contraction of the abdominal muscles whereas regurgitation usually does not. Analysis of the vomitus itself usually reveals a pH less than 5 (regurgitated fluid should not be acidic) unless there is bile present, in which case the pH will often be alkaline. Assessment of the vomitus for the presence of bilirubin (either based on the yellow-green colour or by using a simple urine dipstick) can therefore sometimes be helpful too.

Vomiting can be caused by disease in many areas of the body and therefore from an oncological point of view, may indicate the presence of a tumour in locations other than the stomach. It is helpful to adopt a logical body-systems-based approach to the investigation of a vomiting cancer patient, by considering where and what type of tumour may be present as shown in Box 9.1.

CLINICAL CASE EXAMPLE 9.1 – GASTRIC ADENOCARCINOMA IN A DOG

Signalment

9-year-old neutered male Labrador dog.

Presenting signs

Persistent vomiting.

Clinical examination

• Quiet and disinterested in his surroundings

• Thin body condition

• Mild discomfort on palpation of cranial abdomen

• No other specific abnormalities.

Theory refresher

Gastric cancer is thought to account for less than 1% of all malignancies and is seen less often in cats compared to dogs. It is generally a disease seen in older dogs and the most common form is gastric adenocarcinoma (approximately 75% of all cases) although leiomyosarcoma, lymphoma, mast cell tumour, extramedullary plasmacytoma and fibrosarcoma have all been reported. In cats, the stomach is the least common part of the gastrointestinal tract to be affected by tumours, but, if present, lymphoma is the most likely tumour type to be identified. The clinical histories in affected patients can be quite vague, although as in the case example, most cases will present with a progressively worsening history of vomiting, and frequently, dogs with gastric tumours will present appearing generally unwell, although depending on the duration of the history, some cases will present in good condition. The presence of fresh blood or ‘coffee ground’ haematemesis is only suggestive of the presence of gastric ulceration but this raises the index of suspicion for gastric neoplasia in an older dog.

Initial diagnostic evaluation, as in the clinical case example, can frequently appear unremarkable. Positive contrast radiographic studies may reveal a lesion within the gastric lumen, or be suggestive of gastric ulceration, but ultrasound may often not reveal the presence of a lesion unless it is located within the distal third of the stomach due to the difficulties of imaging the cranial areas of the stomach, unless it is fluid-filled. However, ultrasound can be very useful to assess the gastric and mesenteric lymph nodes and if these are found to be enlarged, to enable ultrasound-guided fine needle aspiration to be performed. Many gastric tumours are diagnosed late in the clinical stage of the disease, by which time, metastasis to the local lymph nodes or other surrounding organs may have occurred, so such assessment is essential in the clinical staging of the disease. Ultrasound can also reveal the loss of layering of the gastric structure that may be seen with an infiltrative condition such as lymphoma.

Flexible endoscopy is very useful to identify intraluminal lesions but it is vital that a logical, stepwise examination technique is adopted to ensure that all the gastric mucosa has been thoroughly visualized. Although the majority of gastric tumours in the dog will be located on the lesser curvature or within the antrum, it is important to remember that a ‘J-manoeuvre’ must be performed to ensure that the cardiac area has been fully examined, as it is possible for small tumours to exist just behind and above the gastro-oesophageal junction and these are easy to miss on simple aboral evaluation if the endoscope is not retroflexed (Fig. 9.2).

Figure 9.2 The ‘J-manoeuvre’;

adapted from ‘Veterinary Endoscopy for the Small Animal Practitioner’, Timothy C McCartney, Elsevier-Saunders 2005, p. 294

If the stomach contains a significant volume of gastric juice, then this should either be suctioned out through the endoscope, or the dog turned from one lateral recumbency to the other to ensure that all areas of the mucosa have been visualized. Some authors recommend premedication of gastroscopy patients with anticholinergics, as these can help reduce the volume of gastric secretions and the degree of gastric motility, but their use is obviously one of personal preference. The authors generally do not find the use of anticholinergics necessary and prefer to undertake gastroscopy with the dog lying in left lateral recumbency, as this allows a clear view of the antrum and pylorus without the risk of fluid obstruction in this area.

Biopsying lesions with endoscopic grab biopsy forceps needs to be undertaken carefully, especially if gastric ulceration is identified. It is not advisable to attempt endoscopic biopsy of the ulcerated tissue itself, as this (a) will likely only yield necrotic tissue of little or no diagnostic use and (b) carries a greater risk of perforation of the gastric wall. Rather, it is better to biopsy the tissue adjacent to the ulcer, as this is much more likely to produce tissue of diagnostic use whilst carrying no greater risk than normal of causing accidental perforation. Obtaining multiple biopsies is essential to increase the representative nature of the samples obtained. It is also important to remember that if one lesion is found and biopsied, a complete gastric examination is still essential in case there is more than one lesion present.

Unless the histopathology confirms the diagnosis to be lymphoma, the only treatment commonly utilized for gastric tumours in cats and dogs is surgery, but this needs to be performed with full owner knowledge that in many cases, even with complete resection, the prognosis has to be considered to be guarded. Gastric adenocarcinomas are usually aggressive tumours that metastasize to the local lymph nodes, liver and finally lungs if left untreated. Many cases present late in their disease course and the possibility of microscopic metastasis existing before the macroscopic form of the disease has been identified has to be considered, so undertaking surgery with curative intent is difficult. However, if a lesion is found to be solitary, then partial gastrectomy can be considered. The problem with such surgery is that as a wide resection is usually required, reconstruction often entails a gastroduodenostomy (Billroth I) and referral to a soft-tissue or oncological surgical specialist is recommended for these patients. The other concern is that the prognosis, even with radical surgery is often poor with survival times in excess of 6 months being uncommon and some studies citing mean survival times as short as 2 months. No chemotherapy has been shown to be efficacious for gastric adenocarcinomas in dogs or cats and its use is not recommended.

Other benign or lower-grade malignant gastric tumours may be more amenable to surgical excision, thereby illustrating the importance of attempting to obtain a presurgical diagnosis if possible. Leiomyomas appear to be found more frequently in the proximal third of the stomach and can usually be removed via a midline laparotomy. Partial gastrectomy has been greatly facilitated in recent years by the use of surgical stapling equipment such as the TA-55 and TA-90 (p. 201). At the time of surgery it is important to examine and biopsy local lymph nodes and any suspicious areas on the surface of the liver or within the omentum.

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Tags: Saunders Solutions in Veterinary Practice Small Animal Oncology

Sep 10, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

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