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Gastroparesis and Pseudo-obstruction

There are marked differences in the gastric emptying rates for solids and liquids. The liquids are emptied much faster from the stomach, not only in healthy, but also in a large majority of patient’s with gastroparesis, and this forms the rationale for a recommendation to suggest liquid nutrition in patient’s with gastroparesis and pseudo-obstruction.

The distinction between eating disorders and gut dysmotilities is difficult, particularly if patients do not admit to altered body perception such as an indifference towards weight loss. Moreover, gastric emptying as well as colonic transit may be delayed.

There are several variables that influence the scintigraphic measurement of gastric emptying and small bowel transit. It is important to bear these variables in mind. A detailed discussion is provided in the syllabus. Remember that in order to provoke an adequate fed response, the calorie content of the meal should be at least 300 calories, there should be adequate binding of the isotope to the meal, otherwise they both separate from each other and do their own thing, and in order to detect delayed gastric emptying, scans should be taken up to four hours after ingestion of the isotope.

Over the past few years, work by Dr. Wendalin and her colleagues at Neuroimmunology at Mayo has highlighted that the antineurolin nuclear antibodies, type 1, are a fairly robust marker of paraneoplastic syndromes in patients with a gut dysmotility of uncertain etiology. In her series of patients with positive antibodies almost all were smokers and 90% of patients ended up having a small cell lung cancer. These patients, as would be anticipated, were elderly, and had symptoms for six months at least, but even more remarkably the lung cancer was unknown before the serology was performed in half the patients. Subsequent testing confirmed the diagnosis, as for instance with thoracoscopy or MRI.

With regard to medications, because the absorption of tablets may be delayed or unpredictable, remember to use suspensions or suppositories for erythromycin, metaclopromide, Compazine, cisapride, whenever available. Whereas the dopaminergic antagonists Reglan and Compazine improve symptoms of nausea and enhance antral contractility, they should be used with caution because of the long term potential for extrapyramidal effects. Cisapride may improve symptoms in gastric emptying. There have been some recent concerns regarding potential cardiac side effects including prolonged QT intervals and torsades. These are concerns that are addressed in the syllabus. Suffice to say that if the potential benefits of cisapride outweigh the risks, then the use is justifiable. We often use combined anti-emetic and prokinetic therapy reserving erythromycin in a dose of 3 mg/kg every eight hours given intravenously for short-term use only. We have not had much success with using erythromycin on a long-term basis, given by mouth. There are some reports alluding to the potential benefits of Octreotide in patients with scleroderma and intestinal pseudo-obstruction. In our experience, we have not had gratifying results. The rule for surgery is restricted to a very few selected patients with gastroparesis or intestinal pseudo-obstruction. Some indications might include a gastrectomy with the Roux-en-Y procedure for patients with severe, postsurgical gastric atony, venting gastrostomy, or a jejunostomy, as I alluded to earlier, or resection of bypass for patients with localized pseudo-obstruction.

We begin with a history and physical examination and some screening laboratory tests. We exclude mechanical obstruction and mucosal disease using a combination of x-rays and endoscopy and then perform a screening assessment of gastric and small bowel transit. If gastric and/or small bowel transit is delayed in the setting of disease which can be attributed to gastroparesis and pseudo-obstruction such as scleroderma or diabetes, we proceed to treat patients accordingly. At the other extreme we believe that if scintigraphic assessments of transit are normal, the patients are likely to have a bona fide motility disorder. If the transit is abnormal, we generally proceed to an antral duodenal manometry which facilitates the distinction of a neuropathic from a myopathic process. If the antral duodenal manometry demonstrates a neuropathic disorder, we will assess an autonomic reflex screen to differentiate an intrinsic from an extrinsic process and often test for paraneoplastic syndrome. Patients with a myopathic process are screened for disorders which can cause a myopathy such as amyloid, scleroderma, or a familiar visceral myopathy.

I would like to end my emphasizing the importance of listening to the history and selecting appropriate tests in approaching patients with gastroparesis and pseudo-obstruction. Remember to exclude mechanical obstruction and consider the possibility of rumination. In interpreting these tests, remember that there are numerous technical variables which influence the tests results.