Gastrointestinal Flashcards
A 57-year-old man comes to the physician because of progressively worsening epigastric pain and 6.8-kg (15-lb) weight loss for the past 2 months. Two weeks ago, he noticed painful, red blotches on the medial aspect of his right calf. He has smoked one pack of cigarettes daily for the last 35 years. He appears thin. Physical examination shows tender, erythematous nodules on the right ankle and left antecubital fossa. Endoscopy shows a large mass in the antrum of the stomach. A biopsy specimen of the gastric mass shows disorganized, mucin-secreting cells with surrounding fibrosis. These cells most likely originated from which of the following structures?
The glandular mucin-secreting cells are typical of pancreatic adenocarcinoma, which is derived from exocrine cells of the pancreas. The pancreatic head is the most common site for adenocarcinoma, but cancers that originate there often manifest with pruritus and painless jaundice secondary to obstruction of the common bile duct. Since this patient lacks these symptoms, his cancer more likely originates in the body or tail of the pancreas. No matter where the cancer starts, pancreatic adenocarcinoma does not typically manifest until after it has metastasized, as seen in this patient.
The tender, erythematous nodules on this patient’s right ankle and left antecubital fossa are suggestive of Trousseau syndrome.
A 53-year-old man comes to the physician because of a 2-week history of fatigue, generalized itching, and yellowing of the eyes and skin. He underwent a liver transplantation because of acute liver failure following α-amanitin poisoning 1 year ago. Physical examination shows scleral icterus and abdominal distention with shifting dullness. A liver biopsy specimen shows decreased hepatic duct density. Further histological examination of the liver biopsy specimen is most likely to show which of the following findings?
Signs and symptoms of liver failure one year after liver transplantation suggests chronic graft rejection, which occurs due to reactions at both the cellular and humoral level in response to donor peptides. The ensuing inflammation leads to interstitial fibrosis, atrophy of the parenchyma, vascular smooth muscle proliferation, and ductopenia (as seen on this patient’s biopsy).
A 62-year-old man with gastroesophageal reflux disease and osteoarthritis is brought to the emergency department because of a 1-hour history of severe, stabbing epigastric pain. For the last 6 months, he has had progressively worsening right knee pain, for which he takes ibuprofen several times a day. He has smoked half a pack of cigarettes daily for 25 years. The lungs are clear to auscultation. An ECG shows sinus tachycardia without ST-segment elevations or depressions. This patient is most likely to have referred pain in which of the following locations?
This patient’s history of smoking and chronic NSAID use put him at increased risk of developing peptic ulcers. Perforated gastric ulcers can manifest with the sudden onset of severe abdominal pain, as seen in this patient, and referred pain to the left shoulder due to irritation of the left hemidiaphragm. Both the phrenic nerve (C3-5), which innervates the diaphragm, and the supraclavicular nerves (C3-4), which innervate the shoulder, share sensory fibers from the C3-4 nerve roots.
This patient has signs of liver failure (jaundice, petechiae, hepatomegaly) and a history of excessive drinking, which suggests alcoholic cirrhosis. Neurological features like confusion and flapping tremors in this setting indicate hepatic encephalopathy.
A drug with which of the following mechanism of action would be most appropriate for this patient’s condition?
Hepatic encephalopathy is caused by the accumulation of toxic metabolites (predominantly ammonia) in the systemic circulation due to liver failure. Lactulose administered orally (or rectally) is converted to lactic acid in the intestine, leading to acidification in the gut and promoting the conversion of absorbable ammonia (NH3) to nonabsorbable ammonium (NH4+). Because ammonium is not absorbed in the intestine and is instead excreted in feces, lactulose reduces the overall systemic load of ammonia.
A 44-year-old woman with hypothyroidism comes to the physician because of a 1-month history of tingling in her feet and poor balance. Her only medication is levothyroxine. Physical examination shows conjunctival pallor and an ataxic gait. Proprioception and sense of vibration are decreased in her toes bilaterally. Laboratory studies show macrocytic anemia and normal thyroid hormone levels. Histological evaluation of tissue samples obtained by esophagogastroduodenoscopy reveals atrophic changes of the gastric body and fundus with normal antral mucosa. Which of the following structures is most likely being targeted by antibodies in this patient?
Pernicious anemia is a common cause of vitamin B12 deficiency and is associated with both anti-parietal cell antibodies and anti-intrinsic factor antibodies. Antibody-mediated destruction of parietal cells leads to decreased intrinsic factor production, resulting in impaired vitamin B12 absorption in the terminal ileum, and subsequent vitamin B12 deficiency, as seen in this patient. Vitamin B12 deficiency classically manifests with macrocytic anemia, peripheral neuropathy, and symptoms of subacute combined degeneration of spinal cord.
A 37-year-old woman comes to the physician because of a 6-month history of weight loss, bloating, and diarrhea. She does not smoke or drink alcohol. Her vital signs are within normal limits. She is 173 cm (5 ft 8 in) tall and weighs 54 kg (120 lb); BMI is 18 kg/m2. Physical examination shows bilateral white spots on the temporal half of the conjunctiva (bitot spots due to vit A deficiency), dry skin, and a hard neck mass in the anterior midline that does not move with swallowing. Urinalysis after a D-xylose meal shows a normal increase in renal D-xylose excretion. Which of the following would have been most likely to prevent this patient’s weight loss?
This patient’s hard, immobile neck mass in the anterior midline is suggestive of Riedel thyroiditis, which is associated with other IgG4-related systemic diseases. Vitamin A deficiency along with her weight loss, diarrhea, and physiologic increase in urinary D-xylose excretion indicate exocrine pancreatic insufficiency, most likely due to autoimmune pancreatitis. Pancreatic enzyme replacement would be the preventative treatment.
Because absorption of D-xylose in the intestine does not rely on the breakdown by pancreatic enzymes, a normal increase in urinary D-xylose excretion indicates a healthy intestinal mucosa. In conditions associated with damage to the intestinal mucosa, oral administration of D-xylose will result in increased fecal D-xylose excretion.
This patient has iron deficiency anemia (progressive fatigue, dyspnea, conjunctival pallor, microcytic anemia, positive stool occult blood) secondary to a well-differentiated, sporadic, right-sided colorectal carcinoma.
A gain-of-function mutation in which of the following genes is most likely involved in the pathogenesis of this patient’s condition?
Most sporadic cases of colorectal carcinoma arise from the chromosomal instability pathway (i.e., the adenoma-carcinoma sequence). In this pathway, a loss-of-function mutation of the tumor suppressor gene APC results in decreased intercellular adhesion and increased epithelial proliferation. Next, a gain-of-function mutation in the KRAS proto-oncogene results in unregulated cellular signaling and cellular proliferation, which predisposes to adenoma formation. Finally, loss-of-function mutations of additional tumor suppressor genes (e.g., TP53, DCC) results in malignant transformation of an adenoma to a carcinoma.
An investigator is studying gastric secretions in human volunteers. Measurements of gastric activity are recorded after electrical stimulation of the vagus nerve. Which of the following sets of changes is most likely to occur after vagus nerve stimulation?
Stimulation of the vagus nerve activates gastric G cells via gastrin-releasing peptide (GRP). G cells produce and release gastrin, which stimulates parietal cells directly and through histamine release from enterochromaffin-like cells. Vagus nerve stimulation also leads to ACh-mediated direct activation of parietal cells and inhibition of somatostatin-producing D cells. The resulting activation of proton pumps in parietal cells increases acid production, which lowers gastric pH.
This patient with dyspepsia, early satiety, and weight loss, most likely has gastric cancer. The endoscopy and biopsy findings indicate a localized gastric adenocarcinoma (intestinal-type gastric cancer).
Which of the following is the strongest predisposing factor for this patient’s condition?
Dietary nitrates are converted to nitrites by oral commensals, and if the diet is low in antioxidants, these nitrites can be converted in the acidic, protein-rich environment of the stomach to nitrosamine compounds (e.g., dimethylnitrosamine), most of which are highly carcinogenic. Increased consumption of smoked, dried, fried, and preserved foods (especially meat), which contain low levels of antioxidants and high levels of nitrates, nitrites, and nitrosamines, is a significant risk factor for the development of gastric adenocarcinoma
A 45-year-old woman comes to the physician because of a 3-month history of mild right upper abdominal pain. She has not had any fevers, chills, or weight loss. There is no personal or family history of serious illness. Medications include transdermal estrogen, which she recently started taking for symptoms related to menopause. Abdominal examination shows no abnormalities. Ultrasonography of the liver shows a well-demarcated, homogeneous, hyperechoic mass surrounded by normal liver tissue (cavernous hemangioma of the liver). A biopsy of the lesion would put this patient at greatest risk for which of the following complication?
Hepatic hemangioma (HH) is a benign tumor composed of cavernous vascular spaces of variable size that are lined by flat endothelial cells. HHs are most common in women between the ages of 30–50 years and may enlarge in response to elevated estrogen levels (e.g., due to pregnancy, hormonal therapy). Most HHs are asymptomatic and diagnosed incidentally on imaging. Because the tumor is highly vascular, biopsy carries a high risk of severe hemorrhage in patients with HHs and is not recommended unless the diagnosis is uncertain.
A 68-year-old man with atrial fibrillation comes to the emergency department with acute-onset severe upper abdominal pain. He takes no medications. He is severely hypotensive. Despite maximal resuscitation efforts, he dies. Autopsy shows necrosis of the proximal portion of the greater curvature of the stomach caused by an embolic occlusion of an artery. The embolus most likely passed through which of the following vessels?
Splenic Artery
