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Flashcards in Gastrointestinal Deck (50)
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1

A 35-year-old woman who is HIV-positive presents to the physician with jaundice and right upper quadrant abdominal pain. The patient reports having had multiple episodes of jaundice over the past 10 years. A hepatitis panel is positive for HBsAg and anti-HBc IgM, but negative for HBsAb and anti-HAV IgM. Which of the following would most likely be lower than normal in this patient?

Albumin

This patient has a flare-up of her chronic hepatitis B infection, as evidenced by the presence of HBsAg and antiHBc IgM and lack of HBsAb. Hepatitis B typically presents with jaundice and right upper quadrant pain and can be transmitted via parenteral, sexual, and maternal-fetal routes. Chronic hepatitis B is marked by the presence of HBsAg for >6 months. While most patients will develop HBsAb and eliminate HBsAg from the blood, chronically infected patients do not. A patient with HIV may have a history of risky sexual behavior and would be at risk for hepatitis B infection; in fact, chronic HBV infection affects about 10% of HIV-infected patients worldwide. This patient’s chronic liver disease would lead to a decrease in albumin, as it is typically produced by the liver

2

A 1-year-old boy presents to the emergency department with bilious vomiting, bloody stools, and abdominal distention. The new intern orders an abdominal radiograph and abdominal ultrasound. The abdominal radiograph is shown in the image. The abdominal ultrasound shows the superior mesenteric artery and vein twisting in a clockwise fashion. Which of the following conditions is the most likely cause of this patient’s symptoms?

Volvulus

This is an example of volvulus, a twisting of the bowel that results in compression of portions of the intestine by other loops of bowel. In adults, volvulus occurs with equal frequency in both the small and large intestines. In children, volvulus almost always occurs in the small intestine and is often the result of intestinal malrotation that occurred during development of the embryonicgut. This patient has symptoms of advanced volvulus: bilious vomiting, abdominal distention, and bloody stools. On the abdominal radiograph, he exhibits the nonspecifi c “doublebubble,” which is a sign of intestinal obstruction. In the image, the white arrow points to the smaller bubble representing the proximal duodenum, while the black arrow points to the stomach. The twisting of the superior mesenteric artery and vein on abdominal ultrasound are more specifi c for a diagnosis of volvulus as a result of malrotation.

3

A 35-year-old woman that is pregnant with her fourth child comes to the physician because of painful gastrointestinal bleeding for the past month. The pain and bleeding are worse when she defecates. Which of the following is the most likely diagnosis?

External hemorrhoids

This patient has external hemorrhoids. External hemorrhoids are thromboses (blood clots) in the veins of the external rectal venous plexus. Since they originate below the pectinate line, external hemorrhoids receive somatic innervation and are therefore painful. Rectal bleeding is also a common symptom with hemorrhoids. Some of the predisposing factors for hemorrhoids include, but are not limited to, pregnancy, constipation, heavy weight lifting, or any other cause that results in increased intra-abdominal pressure

4

A 45-year-old woman presents to her physician with a 2-day history of right upper quadrant pain, nausea, gas, and vomiting. She reports that her symptoms are worse after she eats a fatty meal. Which of the following substances inhibits the hormone causing her right upper quadrant pain?

Somatostatin 

This patient’s symptoms are classic for gallstone cholecystitis. Somatostatin is released by D cells of the pancreas and gastrointestinal mucosa. It inhibits gastric acid, pepsinogen, insulin, glucagon, pancreatic and small intestine fl uid secretion, and (as in this patient) gallbladder contraction

5

A healthy 25-year-old man comes to the physician for a routine examination. His laboratory tests show a serum bilirubin level of 4 mg/dL and a direct bilirubin level of 0.3 mg/dL. The patient’s liver function tests are normal. Which of the following best explains this patient’s serum and indirect bilirubin levels?

Glucuronosyltransferase deficiency

This patient has an indirect bilirubinemia with a high total serum bilirubin but a normal direct bilirubin. In a healthy 25-year-old individual, this is most likely due to a defi ciency in functional glucuronosyltransferase (GST), otherwise known as Gilbert’s disease. Crigler-Naijar syndrome also results from a defi ciency in this enzyme. Type I Crigler-Naijar syndrome (complete absence of GST) is always fatal, while type II (partial defect) is generally mild with occasional kernicterus. Mild GST deficiency causes an indirect hyperbilirubinemia only, while the other answer choices cause an elevation in both direct and indirect bilirubin levels.

6

A 39-year-old white woman who suffers from polycythemia vera presents to the clinic complaining of severe and constant right upper quadrant pain over the past 2 days. Physical examination reveals an enlarged liver. What other fi nding would most likely be seen at presentation?

Ascites

This is an acute presentation of Budd-Chiari syndrome, or thrombosis of two or more hepatic veins. This condition is associated with hypercoagulable states such as myeloproliferative disorders, inherited coagulation disorders, intra-abdominal cancers, oral contraceptive use, and pregnancy. The increased intrahepatic pressure leading to ascites is present in 90% of patients with Budd-Chiari syndrome. The disease can also present in a subacute manner or in a chronic manner, and diagnosing this condition may then be more challenging because the classic triad of abdominal pain, hepatomegaly, and ascites may not be present.

7

A 30-year-old woman presents to her physician complaining of chest pain and difficulty swallowing. Results of ECG and x-ray of the chest were normal, but the following image was seen during a barium swallow study. Which of the following actions is most likely absent in this patient?

Relaxation of the lower esophageal sphincter

The barium swallow study shows esophageal dilatation and a “bird’s beak” sign of the distal esophagus, which are characteristic of achalasia. This disease presents with difficulty swallowing, abnormal contractions of esophageal muscles, absence of peristalsis, and absence of relaxation of the lower esophageal sphincter on swallowing

8

An unconscious 57-year-old man is brought to the emergency department by ambulance with massive, bright red emesis. On arrival, his blood pressure is 80/40 mm Hg and his heart rate is 124/min. He appears jaundiced with multiple spider angiomas on his chest and arms. He has an enlarged abdomen that is dull to percussion and positive for a fl uid wave. He has splenomegaly and muscle wasting in his extremities. Which of the following vessel anastomoses is responsible for the patient’s bleeding?

Left gastric vein and azygos vein

The patient’s presentation is consistent with ruptured esophageal varices. Portal systemic shunting of blood occurs when the liver becomes so fi brotic that there is an increase in resistance in blood fl ow from the portal vein and portal hypertension develops. When the pressure in the portal system is greater than the venous pressure in the systemic system, blood will fi nd alternate routes to return to the heart. One of those alternate routes is from the left gastric vein into the azygos vein. The veins around the esophagus and upper stomach that carry this blood may become enlarged and rupture, as in this case. Mortality from ruptured esophageal varices approaches 50%, so it is important to look for symptoms of liver disease and portal hypertension in anyone with massive hematemesis. It is also important to screen cirrhotic patients with serial endoscopies to look for varices that can be treated before they rupture.

9

A 43-year-old man with a 20-year history of ulcerative colitis presents to the physician with complaints of worsening bloody diarrhea, progressive fatigue, pruritus, visual disturbances, and arthralgias. On physical examination, he is found to have icteric sclera, fi nger clubbing, and several small ulcerations with necrotic edges on both legs. Endoscopic retrograde cholangiopancreatography (ERCP) shows alternating strictures and dilations of the bile ducts. Which of the following conditions is consistent with these ERCP fi ndings?

Primary sclerosing cholangitis

This patient presents with a number of classic extraintestinal manifestations of ulcerative colitis. Progressive fatigue, pruritus, and icteric sclera are clinical manifestations of primary sclerosing cholangitis, an irreversible condition characterized by infl ammation, obliterative fi brosis, and segmental constriction of intrahepatic and extrahepatic bile ducts seen in patients with ulcerative colitis. On endoscopic retrograde cholangiopancreatography (a radiographic visualization of the pancreatic duct and biliary tree), these bile duct changes are visualized as alternating strictures and dilations, or “beading.”

10

A 17-year-old girl who is being treated with antibiotics for recurrent sinus tract infections presents to the physician with intractable watery diarrhea and cramps. Which of the following is most often associated with this patient’s condition?

Clostridium difficile

Pseudomembranous or antibiotic-associated colitis is an acute colitis characterized by the formation of adherent infl ammatory exudates (pseudomembranes) on the injured mucosa. It is usually caused by the two protein exotoxins (A and B) of Clostridium diffi cile, a bacterium normally found in the gut. This disease commonly occurs in patients after a course of broad-spectrum antibiotic therapy (especially clindamycin). Alteration of the normal colonic fl ora allows these toxinproducing strains to thrive. Patients usually present with severe bouts of watery diarrhea, which can be life threatening. The fi rst step in treating these patients is to immediately discontinue the offending antibiotic.

11

A 65-year-old white woman presents to the emergency department with persistent right upper quadrant pain with nausea and vomiting. Abdominal CT scan reveals a polypoid mass of the gallbladder protruding into the lumen, diffuse thickening of the gallbladder wall, and enlarged lymph nodes. This patient most likely has a history of which of the following?

Gallstones

The patient’s clinical presentation is consistent with adenocarcinoma of the gallbladder. Gallbladder adenocarcinoma is associated with chronic gallbladder infl ammation, typically from a history of gallstones, which can be seen with the thickening of the gallbladder wall on CT. Gallbladder polyps, the polypoid lesion, are also associated with an increased risk of gallbladder adenocarcinoma. The enlarged lymph nodes point to local invasion and spread, which is unfortunately common on initial presentation. Gallbladder cancer is a disease of the elderly and is more common in women than men. Most (90%) patients with gallbladder cancer have concomitant stones. In general, the treatment for adenocarcinoma of the gallbladder is surgical excision but prognosis is generally poor if not found incidentally.

12

Which of the following types of hepatocellular injury is commonly seen after acetaminophen overdose?

Centrilobular necrosis

Acetaminophen is known to cause centrilobular necrosis. This type of necrosis occurs immediately around the terminal hepatic vein. In addition to acetaminophen, centrilobular necrosis can be caused by carbon tetrachloride, bromobenzene, halothane, and rifampin. Diffuse hepatic necrosis has also been reported with acetaminophen toxicity.

13

A 46-year-old woman comes to the physician because of voluminous, malodorous, bulky stools. The diarrhea usually abates on fasting. Fecal analysis shows an increased stool osmolality and fat content (fecal fat excretion 32 g/ day [normal: <7 g/day]). Laboratory tests show a sodium level of 149 mEq/L, potassium of 3.5 mEq/L, chloride of 110 mEq/L, and bicarbonate of 18 mEq/L. Which of the following is the pathologic mechanism most likely responsible for the patient’s presentation?

Malabsorption

The patient’s symptoms, characterized by voluminous, malodorous bulky stools that improve with fasting, combined with increased stool osmolality and 72-hour fecal fat, are suggestive of malabsorption. Malabsorption can result from multiple causes, including defective intraluminal digestion (e.g., pancreatitis), primary mucosal cell abnormalities (e.g., celiac sprue, tropical sprue), reduced small intestinal surface area (e.g., small bowel resection), lymphatic obstruction (e.g., Whipple’s disease), and impaired mucosal cell absorption secondary to an infectious agent (e.g., Giardia lamblia). One of the easier ways to test for malabsorption is to perform a 72-hour fecal fat collection. This involves putting a patient on a 100-g fat diet for 3 days followed by fecal fat measurement in the stool.

14

A 62-year-old woman has had persistent nausea for 5 years with occasional vomiting. Gastrointestinal endoscopy reveals a small area of gastric mucosa in the fundus without rugal folds, and a biopsy demonstrates well-differentiated adenocarcinoma confi ned to the mucosa. Upper gastrointestinal endoscopy performed 5 years ago showed a pattern of gastritis. Microscopy at that time showed chronic infl ammation with the presence of Helicobacter pylori. Which of the following best characterizes this patient’s neoplasm?

Favorable prognosis

This patient has early gastric cancer, defined as adenocarcinoma limited to the gastric mucosa and submucosa. It begins in glandular epithelium, but if allowed to advance may invade muscularis propia. The prognosis for early gastric carcinoma is quite good.

15

A 23-year-old man presents to the physician with abdominal distention and tenderness with no vomiting or diarrhea. Physical examination shows hepatosplenomegaly. Bowel sounds are normal. On questioning, the patient says that he traveled to eastern South America 1 year ago. Several weeks after returning from his trip, he remembers having fever, diarrhea, weight loss, and “funny looking stools.” Ultrasonography shows ascites and hepatic periportal fi brosis. Which of the following is most likely responsible for this patient’s present symptoms?

Portal hypertension

Schistosomiasis is a helminthic disease with hepatic involvement. Schistosoma mansoni cercaria, which are commonly found in fresh waters of South America, penetrate the host’s skin, invade the peripheral vasculature, and eventually settle in the portal or pelvic venous vasculature. Several weeks following infection, patients may develop symptoms similar to the ones described, such as fever, diarrhea, and weight loss; the “funny looking stools” likely represent S. mansoni eggs. Chronic infection may eventually lead to portal hypertension and hepatosplenomegaly, leading in turn to ascites and eventually cirrhosis. In addition, the hepatosplenomegaly leads to esophageal varices, producing bleeding that can often be the first clinical sign

16

A 62-year-old woman with rheumatoid arthritis and no other past medical history comes to the emergency department complaining of severe epigastric pain, nausea, and vomiting. She says that she vomited blood earlier in the day. A gross image of the gastric mucosa is shown. Which of the following is the most likely cause of this patient’s symptoms?

Nonsteroidal anti-inflammatory drugs

The symptoms of upper gastrointestinal bleeding associated with epigastric pain in a patient with rheumatoid arthritis are most consistent with acute erosive hemorrhagic gastritis. The image shows diffusely hyperemic gastric mucosa, a typical fi nding in acute gastritis. Given this patient’s history of rheumatoid arthritis, the most likely cause of her presentation is nonsteroidal antiinfl ammatory drug use. As many as 25% of patients who take daily aspirin for rheumatoid arthritis eventually develop acute gastritis.

17

A 20-year-old man with Crohn’s disease refractory to treatment with high-dose methylprednisolone is started on therapy with infl iximab, a chimeric monoclonal antibody with antiinfl ammatory effects. This drug is administered intravenously every 2 months and produces substantial improvement in the patient’s symptoms between doses. Which of the following best describes infl iximab’s mechanism of action?

Binding to and neutralizing a secreted cytokine

Recent studies have demonstrated the benefit of infliximab for the treatment of Crohn’s disease that is refractory to steroid treatment. It is also approved for use in a variety of other autoimmune diseases such as ulcerative colitis, ankylosing spondilitis, psoriasis, and psoriatic arthritis. Infl iximab is a monoclonal chimeric antibody that binds soluble TNF-α, and as a result blocks its effects. TNF-α is a proinfl ammatory cytokine secreted by macrophages that is found in high concentrations in the stool of Crohn’s patients. The chimeric antibody is 75% human and 25% murine. A single infusion produces a clinical response in 65% of patients. Common side effects are increased susceptibility to upper respiratory infections, headache, and gastrointestional distress.

18

A 2-month-old boy is brought to his pediatrician for a regular check-up. His parents report that he has a poor appetite and is very constipated. He has small bowel movements once a week, which his parents believe are very painful. Although he was at the 75th percentile for both height and weight at birth, he is currently at the 25th percentile for height and is below the 5th percentile for weight. His abdomen is distended, but his bowel sounds are normal and his abdomen does not appear to be tender. Barium enema shows a narrow rectosigmoid with a dilation of the segment above the narrowing, and a rectosigmoid biopsy shows a conspicuous absence of acetylcholinesterasepositive ganglion cells. Which of the following genetic conditions is most commonly associated with this patient’s disease?

Down’s syndrome

This patient suffers from Hirschsprung’s disease, which develops when neural crest cells fail to migrate to the distal colon. Consequently, enteric neurons do not form in a segment of the rectosigmoid; these neurons are normally responsible for relaxation of the rectum to allow defecation. Ten percent of cases of Hirschprung’s disease occur in children with Down’s syndrome, caused by trisomy 21. Children with Down’s syndrome also have an increased risk of duodenal atresia, congenital heart disease, and acute lymphoblastic leukemia

19

An 8-year-old boy presents to the emergency department with a 2-hour history of vomiting after eating dinner at a seafood buffet. Arterial blood gas analysis reveals a pH of 7.50, an bicarbonate level of 34 mEq/L, and partial carbon dioxide pressure of 40 mm Hg. Which of the following best describes the acid-base disturbance occurring in this patient?

Metabolic alkalosis

Vomiting typically induces a metabolic alkalosis due to a loss of hydrogen ions from the stomach, leading to an increase in pH. This leaves an increased bicarbonate concentration (generally >24 mEq/L) in the bloodstream. In this case, the partial carbon dioxide pressure is still normal; thus, no respiratory compensation has occurred, and the patient has uncompensated metabolic alkalosis.

20

A 37-year-old woman is found by police in a confused state and is brought to the emergency department for evaluation. The patient is unable to answer any of the physician’s questions. Physical examination reveals jaundice. Despite aggressive therapy the patient dies. An autopsy is performed and a microscopic view of the patient’s liver is shown in the image. Which of the following conditions is most consistent with these findings?

Alcoholic hepatitis

The image shows fatty change, Mallory bodies, and a neutrophilic infi ltrate. These histopathologic fi ndings, as well as the patient’s jaundice, are consistent with hepatitis seen in severe exposure to alcohol. Intracytoplasmic hyaline inclusions derived from cytokeratin intermediate filaments are called Mallory bodies, which are also seen in primary biliary cirrhosis, Wilson’s disease, chronic cholestatic syndromes, and hepatocellular tumors. Prolonged alcohol abuse may result in alcoholic cirrhosis, an irreversible condition characterized by nodular fibrosis of the liver parenchyma.

21

A 24-year-old man presents to the physician with diarrhea and abdominal cramps. A fecal occult blood test is positive. On questioning, it is learned that the patient went swimming in a lake during a camping trip 2 days ago. A stool sample is sent for laboratory evaluation. This patient is most likely infected with which of the following?

Entamoeba histolytica

Entamoeba histolytica infection presents with bloody diarrhea (dysentery), abdominal cramps with tenesmus, and pus in the stool. It can also cause right upper quadrant pain and liver abscesses. E. histolytica is transmitted via cysts in water (fecaloral transmission). On microscopy, one observes amebas with ingested RBCs. Treatment for E. histolytica infection includes metronidazole and iodoquinol.

22

A 27-year-old man goes to the doctor for an annual physical examination. On rectal examination, masses are palpated. The patient is referred for a colonoscopy, which reveals adenomatous polyps located diffusely throughout the colon. When asked about his family history, the patient states that his father passed away from colon cancer. A diagnosis of familial adenomatous polyposis is suspected, and the patient asks how he got this. Which of the following is the inheritance pattern of this condition?

Autosomal dominant

Familial adenomatous polyposis (FAP) is an autosomal dominant condition characterized by a germline mutation on chromosome 5, specifically at the adenomatous polypsis coli (APC) locus. The APC gene is thought to have tumor suppressive effects, and its loss is associated with more than colonic cancers. Patients with FAP are at increased risk for developing duodenal, gastric, liver, thyroid, and central nervous system neoplasms

23

A 10-year-old girl living in New Jersey is brought to the physician because she has had a fever and headache accompanied by abdominal pain and bloody diarrhea. Her stool smear shows leukocytes. A stool culture incubated at 42º C (107.6º F) in a microaerophilic environment shows many comma-shaped organisms each with a single polar fl agellum. She has no history of recent travel or sick contacts. She has a pet puppy, which the mother says has had diarrhea for the past week. Based on the above information, the physician suspects bacterial gastroenteritis. The organism responsible for this patient’s sickness is thought to be associated with the possible later development of which of the following symptoms?

Symmetric ascending muscle weakness beginning in the distal lower extremities

Guillain-Barré syndrome is characterized by rapidly progressing ascending paralysis. It is an autoimmunemediated illness that can occur following a variety of infectious diseases, such as cytomegalovirus, Epstein-Barr virus, HIV, mycoplasma pneumonia, and gastroenteritis caused by Campylobacter jejuni. C. jejuni gastroenteritis is characterized by bloody diarrhea together with the fi nding of comma-shaped organisms with a single polar fl agellum when cultured at 42º C (107.6º F) in a microaerophilic environment. Other enteric pathogens with this morphology include bacteria of the Vibrio genus (V. cholera and V. parahaemolyticus). These species, however, are not endemic to the United States, and would not be expected in a patient without a recent travel history. Domestic animals serve as a source of C. jejuni, which are then transmitted to humans via the fecaloral route

24

A 2-year-old girl who has recently been adopted from an impoverished family is brought to the clinic by her adopted parents. They are concerned because the child seems to be having trouble with her vision at in low-light conditions. The vitamin most likely deficient in this child is absorbed by the gastrointestinal system using what mechanism?

Micelle-mediated transport

This patient has vitamin A deficiency, which is characterized by early symptoms of night blindness, dry conjunctivae, and gray plaques, or late symptoms of corneal ulceration and necrosis leading to perforation and blindness. This deficiency is typically seen in children and pregnant women whose diets are deficient in vitamin A, especially those from Southeast Asia. Vitamin A deficiency can also result from malabsorption following intestinal surgery, especially of the ileum. Vitamins A, D, E, and K (the fat-soluble vitamins) are absorbed in the small intestine and absorption requires micelles formed with bile salts

25

A 46-year-old white woman with rheumatoid arthritis presents with severe pruritus. She denies any history of alcohol or drug use. On physical examination, she is found to have icteric sclera, palpebral xanthomas, and hepatomegaly. She tests positive for antimitochondrial antibody and increased alkaline phosphatase activity. Which of the following is most likely responsible for this patient’s presentation?

Destruction of intrahepatic bile ducts

The triad of jaundice (icteric sclera), hypercholesterolemia (palpebral xanthomas), and pruritus with positive antimitochondrial antibody titers and elevated alkaline phosphatase activity is classic for primary biliary cirrhosis. Primary biliary cirrhosis is a cholestatic disease with chronic, progressive, and often fatal liver injury characterized by the destruction of medium-sized intrahepatic bile ducts with eventual liver failure. Liver transplantation is the defi nitive treatment.

26

A 10-year-old boy presents to the pediatrician with weight loss and multiple purpuric lesions all over his body. The patient has bulky, greasy yellow stools associated with abdominal pain and fl atulence that most often occurs after meals. Which of the following will most likely be seen on bowel biopsy?

Diffuse severe atrophy and blunting of the villi

This patient’s clinical presentation is consistent with celiac disease. The physical exam would most likely reveal an anorexic-appearing child with temporal wast-ing and multiple nonblanching purpuric lesions located on the upper and lower extremities, called dermatitis herpetiformis. Celiac disease (gluten-sensitive enteropathy) is characterized by blunting and atrophy of the small bowel villi and lymphocytic infi ltrates resulting in malabsorption of most nutrients, accounting for the symptoms and physical fi ndings present in this patient. The gliadin fraction in wheat is responsible for disease activation. Thus, introduction of cereals into the diet is responsible for most patients’ presentations. Discontinuation of gliadin-containing foods such as cereals usually results in complete remission.

27

A 26-year-old man with hepatitis C is being medically treated while he awaits liver transplantation. One of the drugs he is taking causes him to have periodic fevers and chills and a sense of depression that he did not have prior to treatment. Which of the following is most likely responsible for this patient’s adverse effects?

Pegylated interferon

Pegylated interferon is a cytokine derivative that improves the body’s antiviral response. It is used in the treatment of hepatitis B and C. Adverse effects of interferon therapy include a fl u-like reaction that manifests as episodic fevers and chills, as well as occasional profound depression. As a result, interferon is contraindicated in severely depressed or suicidal patients. Although interferon is not a cure for hepatitis, it is recommended to slow the progression of cirrhotic liver disease in some patients. Pegylated interferon is a longer-acting form of interferon.

28

A 19-year-old man presents to the emergency department with a new onset of right lower quadrant abdominal pain. On physical examination, the patient has a temperature of 38.5° C (101.3° F) and a WBC count of 13,000/mm³. Flexion at his hip elicits pain. Release of manual pressure on the abdomen causes more pain than deep palpation. Which of the following is also most likely present in this patient?

Nausea and vomiting

New onset of right lower quadrant abdominal pain in a young patient with a fever and an elevated WBC count is suggestive of appendicitis. Patients with appendicitis typically present with periumbilical or right lower quadrant abdominal pain. Fifty to sixty percent will also present with nausea and vomiting. They may also exhibit a psoas sign (pain on hip fl exion) and rebound tenderness.

29

A 4-year-old child is brought to the pediatrician because of abdominal pain, vomiting, and diarrhea containing mucus and blood. The child has a fever of 39.4° C (103° F). On stool culture, the causative organism is shown to be a non-lactose-fermenting and non-hydrogen sulfi de-producing bacterium. Which of the following is most likely responsible for the child’s illness?

Shigella species

Shigella species produce gastroenteritis characterized by abdominal pain, bloody diarrhea, and nausea and/or vomiting. Additionally, since Shigella species invade intestinal epithelial cells, the illness is accompanied by fever. Shigella is a nonlactose fermenter, and it does not produce gas or hydrogen sulfi de. Shigella infection usually affects preschool-age children and populations in nursing homes. Transmission occurs by the fecal-to-oral route via fecally contaminated water and hand-to-hand contact.

30

A 42-year-old man visits his primary care physician to discuss possible cholesterol-lowering agents. His last blood test showed that he had elevated LDL cholesterol and triglyceride levels. The physician decides to prescribe gemfi brozil and schedules the man for a follow-up visit in 1 month. Which of the following results are likely to be seen on this patient’s next blood test?

A large decrease in triglycerides, a slight decrease in LDL cholesterol, and a slight increase in HDL cholesterol

Gemfibrozil functions mainly to reduce the circulating level of triglycerides. It is a fi bric acid derivative that acts on peroxisome proliferator-activated receptor-α protein to increase the activity of lipoprotein lipase and facilitate enhanced clearance of triglycerides. There is also a slight reduction in cholesterol synthesis.