A 53-year-old man comes to the physician due to weight loss, fatigue, and anorexia. He reports no dietary changes but has lost 6.8 kg (15 lb) in the past 2 months. Endoscopy shows an early invasive gastric cancer. The patient undergoes an uncomplicated total gastrectomy without any postoperative complications. The physician counsels the patient that he must receive lifelong administration of which of the following substances?

Question

A 53-year-old man comes to the physician due to weight loss, fatigue, and anorexia.  He reports no dietary changes but has lost 6.8 kg (15 lb) in the past 2 months.  Endoscopy shows an early invasive gastric cancer.  The patient undergoes an uncomplicated total gastrectomy without any postoperative complications.  The physician counsels the patient that he must receive lifelong administration of which of the following substances?

Quizplus · Accepted Answer

11ec160b_3adc_e881_9249_59ea3131e80a_MD0001_00 The stomach performs a number of important functions: Protein digestion - Gastric parietal cells and chief cells produce hydrochloric acid (HCl) and pepsinogen, respectively. HCl helps to denature dietary protein (improving proteolysis) and also converts pepsinogen to its active form, pepsin, which preferentially cleaves polypeptides at aromatic amino acid locations. Pancreatic and intestinal proteases further degrade dietary proteins into basic amino acids in the small intestine. Intrinsic factor (IF) secretion - Parietal cells in the body and fundus of the stomach also secrete IF, a glycoprotein that normally binds to vitamin B₁₂. The B₁₂-IF complex is then absorbed by enterocytes in the terminal ileum. However, in patients who have undergone total gastrectomy, IF can no longer be produced and vitamin B₁₂ cannot be effectively absorbed. Therefore, very high-dose oral or parenteral vitamin B₁₂ becomes necessary. Gastric reservoir - The stomach also serves as a reservoir for ingested food. This function is lost after total gastrectomy, and accelerated emptying of hyperosmolar food boluses into the small bowel results in dumping syndrome (characterized by colicky abdominal pain, nausea, and diarrhea). Avoidance of large meals and low dietary intake of simple sugars improves these symptoms. (Choices B, C, and D) Pepsin and HCl are helpful, but not required, for protein digestion; patients can still digest protein after undergoing total gastrectomy due to the presence of pancreatic and intestinal proteases. It is not necessary to administer gastric enzymes, HCl, or hydrolyzed protein in these patients. (Choice E) Medium-chain triglycerides can passively diffuse from the gastrointestinal lumen into enterocytes, but they are best absorbed after being degraded into monoglycerides and free fatty acids by lingual and pancreatic lipase. Supplementation is not necessary in total gastrectomy patients. Educational objective: Intrinsic factor (IF) is a glycoprotein that is normally secreted by parietal cells in the stomach and is necessary for the absorption of vitamin B₁₂ in the ileum. Patients who have undergone a total gastrectomy require lifelong vitamin B₁₂ supplementation due to inability to produce IF. __________ References: Oral vitamin B12 replacement: an effective treatment for vitamin B12 deficiency after total gastrectomy in gastric cancer patients. (http://www.ncbi.nlm.nih.gov/pubmed/21556950)

A 53-Year-Old Man Comes to the Physician Due to Weight