Block 1 Flashcards
Which of the following drugs increases the rate of gastric emptying in the vagotomised stomach?
Ondansetron
Metoclopramide
Cyclizine
Erythromycin
Chloramphenicol
Erythromycin
Vagotomy seriously compromises gastric emptying which is why either a pyloroplasty or gastro-enterostomy is routinely performed at the same time.
Chloramphenicol has no effect on gastric emptying. Ondansetron slows gastric emptying slightly. Metoclopramide increases the rate of gastric emptying but its effects are mediated via the vagus nerve. Erythromycin enhances gastric emptying by acting via the motilin receptor in the gut.
What factors delay gastric emptying?
Hormonal:
Gastric inhibitory peptide
Cholecystokinin
Enteroglucagon
What factors increase gastric emptying?
Gastrin
Parasympathetic stimulation by the vagus nerve
What do patients undergoing truncal vagotomy require and why?
Routinely require either a pyloroplasty or gastro-enterostomy or they would otherwise have delayed gastric emptying
What may the consequences of diseases affecting gastric emptying be?
Bacterial overgrowth
Retained food-> bezoars that may occlude the pylorus
Fermentation of food may cause dyspepsia, reflux and foul smelling belches of gas
Iatrogenic factors impacting gastric emptying
Any procedure that disrupts the vaugs nerve-> depayed emptying. vagotomy not routinely performed but oesophagectomy may also disrupt vagal nervous supply of the stomach.
When a distal gastrectomy is performed, the type of anastomosis performed impacts on emptying. e.g. when a gastro-enterostomy is constructed, posterior retrocolic gastroenterostomy will empty better than an anterior one
How does the type of gastro-enterostomy performed affect gastric emptying?
When a distal gastrectomy is performed, the type of anastomosis performed will impact on emptying. When a gastro-enterostomy is constructed, a posterior, retrocolic gastroenterostomy will empty better than an anterior one.
Diabetic
Episodes of repeated and protracted vomiting
?Diabetic gastroparesis
Pathophysiology of diabetic gastroparesis
Predominantly due to neuropathy affecting the vagus nerve
Diagnosis of diabetic gastroparesis
Upper GI endoscopy
Contrast studies
Radio-nucleotide scan may be used rarely to demonstrate abnormality
Treatment of diabetic gastroparesis
Drugs such as metoclopramide don’t work as effectively as they exert their effect via the vagus nerve.
Erythromycin is one of the few prokinetic drugs that does as it works via the motilitin receptor
Malignancies causing delayed gastric emptying
Distal gastric cancer
Malignancies of the pancreas may cause extrinsic compression of duodenum
Treatment of gastric outflow obstruction by malignancy
Gastric decompression with wide bore NG tube (Ryles tube)
Insertion of stent
Or surgical bypass via gastroenterostomy
Where is the anatsomosis placed in gastroenterostomy due to malignancy
In the anterior wall despite less good emptying
What type of bypass may also be used in obstructing gastric malignancy
Roux en Y bypass
Typically a disease of infancy. Most babies will present around 6 weeks of age with projectile non bile stained vomiting. It has an incidence of 2.4 per 1000 live births and is more common in males.
Pyloric stenosis
Diagnostic test in in py sten
USS- hypertrophied pylorus
Metabolic abnormality in pyloric stenosis
Hypochloraemic hypokalaemic metabolic alkalosis
What is the earliest complication that can occur following construction of an ileostomy?
Prolapse
Retraction
Necrosis
Parastomal hernia
Dermatitis
Necrosis
Construction of a stoma may be complicated by several factors. Necrosis may occur because of technical errors in mesenteric division, excessive tension or failure to construct a fascial defect of adequate size to permit safe passage of the mesentery and the bowel.
Where are ileostomies generally fashioned?
RIF in the triangle between ASIS, symphysis pubis and umbilicus
Should lie one-third of the distance between the umbilicus and ASIS.
Process of ileostomy formation
They should lie one-third of the distance between the umbilicus and anterior superior iliac spine. A 2cm skin incision is made and dissection continued through the rectus muscle. A cruciate incision should be made, and generally dilated to admit two fingers. The ileum is brought through the incisions and should generally be spouted to a final length of 2.5cm. Ileostomies that are too short may cause problems with appliance fixation and those which are too long may cause problems with tension and subsequent ulceration or prolapse.
What is the most common complication post-ileostomy
Dermatitis
What is the usual ileostomy output?
5-10ml/kg/24h
When might ileostomy output require additional IVF
20ml/kg/24h












































