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54 CHRONIC VOMITING IN CATS PEER REVIEWED investigation. This can be accomplished via endoscopy, laparoscopy, or laparotomy. The decision to perform endoscopy over laparotomy is multifactorial, and advantages of each approach are listed in Box 2 . Investigating Imaging Findings No Abnormalities Endoscopy is generally preferable as an initial sampling technique for patients without abnormalities on imaging because it is less invasive and might reveal focal mucosal lesions that would be missed by laparotomy. Diffuse Changes Endoscopy should be considered for cases with diffuse or accessible focal GI changes, whereas laparotomy is prioritized for patients with ultrasonographic abnormalities limited to the jejunum. Although the muscularis is inaccessible endoscopically, thickening on ultrasonography does not necessarily dictate use of more invasive sampling techniques, such as laparotomy. Diffuse ultrasonographic thickening is often associated with IBD and lymphoma ( Figure 2 ), 49,50 which are regularly diagnosed via endoscopic biopsy. Focal Thickening Focal thickening of the muscularis propria has been associated with mast cell tumor, 51 which might be amenable to endoscopic sampling depending on location. Because muscularis thickening can occur in cats without GI disease, sampling is not warranted in the absence of clinical signs. 52 Similarly, although focal mass effects on examination or diagnostic imaging are most suggestive of neoplasia, disorders such as GI eosinophilic sclerosing fibroplasia and (rarely) fungal infection should not be overlooked. Because the location of lesions can substantially complicate surgical removal and positive, long-term responses can be achieved by using a combination of diet and medical therapies, 53 it is reasonable to rule out GI eosinophilic sclerosing fibroplasia via endoscopy before proceeding to laparotomy. Identifying Lesions for Surgery Endoscopy can be useful for localizing and targeting mucosal lesions for surgical intervention, although it is very reasonable to proceed directly to laparotomy in cases with concurrent abnormalities in the liver, pancreas, or other organs. If financial limitations are present, BOX 2. Advantages of Endoscopy versus Laparoscopy or Laparotomy 48 Advantages of endoscopy • Allows direct, continuous visualization of the gastrointestinal tract (Figure A) without disruption of normal anatomy, thereby enhancing detection of: o Primary and secondary esophageal diseases (eg, esophagitis) o Gastroduodenal reflux o Erosions and ulcerations o Multifocal and highly localized lesions o Alterations in gastrointestinal motility • Uses natural orifices for access, allowing more rapid recovery and avoiding risk of dehiscence Advantages of laparoscopy or laparotomy • Ability to obtain full-thickness samples • Ability to sample neighboring structures (eg, liver, pancreas, regional lymph nodes) • Ability to access lesions aborad to approximately 50% of the duodenum or orad to the ileum • Ability to achieve cure through surgical resection of focal neoplasms or other masses FIGURE A. Endoscopic image of a prominent duodenal papilla (arrow) and generalized mild duodenal edema in a cat with chronic hyporexia and vomiting due to lymphocytic IBD.