Gastrointestinal Bleeding case 6

A 2-year-old child is seen in the emergency department because of bright red blood per rectum. This is the third time this has happened, and on the previous episode, no lesion was identified on colonoscopy. During this visit, the child is scheduled for small bowel barium studies,

which show an outpouching of the distal ileum about 2 feet proximal to the cecum.

Q 1

Which of the following is the most likely diagnosis?

/ A. Abnormally located appendix

/ B. Crohn disease

/ C. Diverticulosis

/ D. Meckel diverticulum

/ E. Potter syndrome

Q 2

The prevalence of this patient's anatomic anomaly in the US population is which of the following?

/ A. 2%

/ B. 6%

/ C. 15%

/ D. 40%

/ E. 80%

Q 3

This patient's anatomic anomaly is thought to be embryologically derived from which of the following?

/ A. Mesonephric duct

/ B. Mullerian duct

/ C. Paramesonephric duct

/ D. Vitelline duct

/ E. Wolffian duct

Q 4

Which of the following is the most common type of ectopic tissue seen in this patient's anatomic anomaly?

/ A. Endometrial tissues

/ B. Gastric mucosa

/ C. Jejunal mucosa

/ D. Pancreatic tissue

/ E. Rectal mucosa

Q 5

The ulceration that was the source of bleeding in this patient is most likely related to acid secretion by which of the following cell types?

/ A. Chief cells

/ B. Mucous neck cells

/ C. Parietal cells

/ D. Surface epithelial cells

/ E. Zymogenic cells

Q 6

The acid-secreting cells are stimulated by which of the following hormones?

/ A. Cholecystokinin

/ B. Gastric inhibitory peptide

/ C. Gastrin

/ D. Secretin

/ E. Vasoactive intestinal polypeptide

Q 7

Stimulation of which receptor on the acid-secreting cell leads to increased acid secretion?

/ A. Epinephrine receptor

/ B. Histamine-1 receptor

/ C. Histamine-2 receptor

/ D. Prostaglandin E2 receptor

/ E. Somatostatin receptor

______________________________

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Gastrointestinal Bleeding case 6 answers

A1

The correct answer is D. This patient has a Meckel diverticulum. Meckel diverticula can be asymptomatic through life, or may come to medical attention because of a bleeding peptic ulcer, acute inflammation, rupture, strangulation, or intussusception of the Meckel diverticulum. Diagnosis, as in this case, may be difficult because the ileum is difficult to visualize. In some cases, small bowel barium studies may successfully identify the lesion.

While the appendix (choice A) can have variations in location, these tend to involve the side of the cecum into which it opens. Also, the appendiceal lumen remains narrow in aberrant locations.

Crohn disease (choice B) can involve the distal ileum and cause gastrointestinal bleeding, but would not cause an isolated outpouching of the ileum.

Diverticulosis (choice C) refers to acquired diverticula, and is usually a disease of older individuals.

Potter syndrome (choice E) refers to the cluster of bilateral renal agenesis, oligohydramnios, limb deformities, facial deformities, and pulmonary hypoplasia.

A2

The correct answer is A. The usually cited prevalence for Meckel diverticulum is 2%, although it actually varies from 0.2% to 4%. Many medical students remember five "2s" associated with Meckel diverticulum: 2 inches long, 2 feet from the ileocecal valve, 2% of the population, commonly presents in the first 2 years of life, and may have 2 types of epithelium.

A3

The correct answer is D. The vitelline duct or yolk stalk embryologically connects the midgut to the yolk sac. The duct usually disappears by the seventh gestational week, but if it fails to obliterate, several lesions can be produced, including Meckel diverticulum, a persistent vitelline duct that drains as a fistula through the anterior abdominal wall at the umbilicus, a fibrous band, or a vitelline duct cyst. The other ducts are genital ducts.

The mesonephric (wolffian) duct (choices A and E) develops into seminal vesicles, epididymis, ejaculatory duct, and ductus deferens; the paramesonephric (mullerian) duct (choices B and C) develops into the fallopian tube, uterus, and part of the vagina.

A4

The correct answer is B. Meckel diverticula often have ectopic tissues in them, the most common of which is heterotopic gastric mucosa. The tissues listed in the other choices can also be seen, as well as colonic mucosa.

A5

The correct answer is C. In gastric mucosa, whether in the stomach, or in an ectopic location, it is the parietal cells that secrete acid. This acid secretion is particularly likely to cause peptic ulceration in a Meckel diverticulum or the adjacent ileum, because the secretion of protective mucus is likely to be markedly inadequate in this setting, and the distal small intestinal mucosa is not equipped to handle an acid environment.

The chief cells, also called zymogenic cells (choices A and E) secrete pepsinogen.

The mucous neck cells and surface epithelial cells (choices B and D) secrete mucus.

A6

The correct answer is C. The polypeptide hormone gastrin is secreted by the duodenum and pyloric antrum. Its release is stimulated by the presence of digested protein in the stomach and duodenum. Gastrin stimulates acid secretion from the parietal cells of the gastric glands and pepsinogen secretion from the chief cells.

Cholecystokinin (choice A) is secreted by the endocrine cells of the duodenum and proximal jejunum, and stimulates pancreatic enzyme synthesis and secretion, increases gall bladder emptying, and decreases gastric emptying.

Gastric inhibitory peptide (choice B) inhibits gastrin release and gastric acid secretion, and causes insulin release from the endocrine pancreas.

Secretin (choice D) is produced in the crypts of Lieberkühn of the duodenum, and stimulates pepsinogen secretion from the stomach, and fluid and bicarbonate release from the pancreas.

Vasoactive intestinal polypeptide (choice E) induces smooth muscle relaxation, modifies the composition of pancreatic juice and bile, and inhibits gastric acid secretion and absorption from the intestinal lumen.

A7

The correct answer is C. Acid secretion by parietal cells can be stimulated by the gastrin receptor, the histamine-2 (H2) receptor, and the acetylcholine receptor. Drugs with anti-H2 receptor activity are used to treat peptic ulcer disease. The histamine that stimulates the H2 receptors is probably derived from enterochromaffin cells.

Epinephrine and histamine-1 receptors (choices A and B) do not appear to have a physiologic role in gastric acid secretion.

Substances capable of reducing gastric acid secretion include prostaglandin E₂(choice D), secretin, and somatostatin (choice E).

Gastrointestinal Bleeding case 5

A 47-year-old, darkly pigmented man with a known history of alcohol abuse begins vomiting large quantities of blood and is brought by ambulance to the emergency department.

Q 1

In the emergency department, the man is found to have a temperature of 36.7 C (98.1 F), blood pressure of 65/40 mm Hg and dropping rapidly, a weak pulse of 130/min, and respirations of 29/min. These vital signs suggest that which of the following is developing?

/ A. Congestive heart failure

/ B. Meningitis

/ C. Pneumonia

/ D. Septicemia

/ E. Shock

Q 2

A blood sample is drawn and an IV Iine is started. While the patient is being cross-matched, the physical examination is continued. The patient's sclerae are noted to be icteric and his nail beds and palms have a yellowish hue. A caput medusa

is noted. Which of the following is the most accurate description of a caput medusa?

/ A. Ecchymoses over the mastoid process

/ B. Paradoxical increase in venous distension and pressure during inspiration

/ C. Reflex movement of the eyes in the opposite direction to that in which the head is moved

/ D. Small bony masses found on the terminal phalanges

/ E. Varicose veins radiating from the area of the umbilicus

Q 3

Caput medusa specifically suggests which of the following diagnoses?

/ A. BIadder infection

/ B. Duodenal ulcer

/ C. Gastric ulcer

/ D. Pancreatitis

/ E. Portal hypertension

Q 4

Which of the following is the most common cause of this patient's disorder in the United States?

/ A. Hepatic cirrhosis

/ B. Hepatic vein thrombosis

/ C. Hepatocellular carcinoma

/ D. Metastatic disease to the liver

/ E. Portal vein thrombosis

Q 5

Endoscopic studies demonstrate that this patient has bleeding esophageal varices, and the bleeding is successfully stopped with

sclerotherapy. What percentage of patients with bleeding esophageal varices have another episode of variceal bleeding at a subsequent

time?

/ A. 5%

/ B. 25%

/ C. 40%

/ D. 70%

/ E. 95%

Q 6

Following blood transfusions and sclerotherapy, the patient initially feels reasonably well and is able to converse with medical personneI. Over

the next 12 hours, while he does not begin to rebleed, his mental status deteriorates. Arterial blood levels of which of the following would be

most helpful in confirming the likely diagnosis?

/ A. Ammonia

/ B. Angiotensin l

/ C. Calcitonin

/ D. Carbon monoxide

/ E. Ceruloplasmin

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Gastrointestinal Bleeding case 5 answers

A1

The correct answer is E. The patient's low and dropping blood pressure, tachycardia, high respiratory rate, and slightly below normal body temperature are all consistent with impending shock. At this point, the other conditions listed in the choices have not yet been ruled out, but clinically, the patient should begin to be immediately treated for the shock, even if the therapeutic workup for underlying conditions must be temporarily deferred

A2

The correct answer is E. Medusa was a goddess with snakes instead of hair on her head. The caput medusa (Medusa's head) is an old term still in fairly common use for numerous varicose veins radiating over the abdomen from the area of the umbilicus.

Choice A describes Battle's sign, which is suggestive of basal skull fracture.

Choice B describes Kussmaul's sign, which is seen in constrictive pericarditis.

Choice C describes the doll's eye sign, which is looked for in the evaluation of comatose patients and suggests functional integrity of the brainstem tegmental pathways and cranial nerves involved in eye movement.

Choice D describes Heberden's nodules, which are seen in osteoarthritis.

A3

The correct answer is E. The caput medusa develops when severe portal hypertension induces dilation of the anastomotic channels between the portal venous system and the systemic venous system, some of which involve the superficial veins near the umbilicus. The other answers are distracters.

A4

The correct answer is A. The overwhelmingly most common cause of portal hypertension in the United States is hepatic cirrhosis, which is usually due to either alcoholism or hepatitis viral infection. In this patient's case, the diagnosis of cirrhosis is further clinically substantiated by his jaundice, as evidenced by his sclera, nail beds, and palms. (Look in these areas on individuals in whom dark skin pigmentation may mask the jaundice generally.) The other entities listed are occasional causes of portal hypertension.

A5

The correct answer is D. Patients who have had one episode of bleeding from esophageal varices have an approximately 70% chance of developing a second incident of bleeding, and one third of these episodes of rebleeding is fatal.

A6

The correct answer is A. Hepatic encephalopathy is seen in end-stage cirrhosis patients, and can either present or worsen in the presence of gastrointestinal bleeding. The blood in the upper gastrointestinal tract behaves essentially as a high protein load, and increases the absorption of ammonia and nitrogen, which cannot be appropriately metabolized by the liver. GI bleeding may also predispose for inadequate renal function secondary to hypotension.

Angiotensin I (choice B) is part of the renin-angiotensin-aldosterone system for blood pressure and sodium ion control.

Calcitonin (choice C) is a hormone secreted by the thyroid, which may be increased in medullary carcinoma of the thyroid.

Carbon monoxide (choice D) increases in the blood in smokers.

Ceruloplasmin (choice E) is a copper-carrying protein monitored in patients with Wilson disease.

Gastrointestinal Bleeding case 4

A 25-year-old man presents to the emergency department complaining of passing bright red blood per rectum. He reports no prior episodes of gastrointestinal bleeding, but he has had occasional lower abdominal pain and diarrhea for the past ten months. He reports a 7 kg weight Ioss since the onset of these symptoms. He denies sick contacts. On examination, he is febrile with moderate, diffuse abdominal pain to palpation and percussion. Rectal examination is positive for blood.

Q 1

Which of the following is the most likely diagnosis?

/ A. Chronic pancreatitis

/ B. Duodenal ulcer

/ C. Infectious colitis

/ D. Inflammatory bowel disease

/ E. Ischemic colitis

Q 2

A colonoscopy is performed and mucosal ulceration with bleeding extending continuously from the rectum to the cecum is seen. The terminal

ileum is spared. Had the terminal ileum been affected, the patient would have been at risk for which of the following conditions?

/ A. Diabetes mellitus

/ B. Folate deficiency

/ C. Iron deficiency anemia

/ D. Kwashiorkor

/ E. Pernicious anemia

Q 3

At colonoscopy the colonic mucosa appears granular, and is ulcerated. Numerous crypt abscesses and pseudopolyps are observed. Which of

the following is the most likely diagnosis?

/ A. Celiac disease

/ B. Clostridium difficile colitis

/ C. Crohn disease

/ D. Rectal diverticulosis

/ E. Ulcerative colitis

Q 4

Several months pass and this patient's symptoms progress. He continues to have frequent bloody diarrhea and abdominal pain. Abruptly, this

patient experiences the acute onset of severe abdominal pain and is taken to the emergency department by friends. In the emergency

department, he is febrile, and his abdomen is rigid, with severe pain to palpation and percussion. Laboratory findings are consistent with

dehydration. Amylase and lipase are normaI. Which of the following most likely explains this patient's new findings?

/ A. Abdominal aortic aneurysm rupture

/ B. Acute pancreatitis

/ C. Bowel perforation and peritonitis

/ D. Sepsis from fulminant infectious colitis

/ E. Severe ischemic colitis

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Gastrointestinal Bleeding case 4 answers

A1

The correct answer is D. Patients with inflammatory bowel disease can present with a variety of symptoms. While ulcerative colitis and Crohn disease patients may have distinct presentations, mixed presentations are common. Distinguishing Crohn disease and ulcerative colitis is difficult, based on clinical findings. Symptoms typical for Crohn disease include: abdominal pain, fever, diarrhea, weight loss, and anal disease. Symptoms typical for ulcerative colitis include: bloody diarrhea, fever, and weight loss.

Chronic pancreatitis (choice A) presents as epigastric pain that radiates to the back, weight loss, and steatorrhea. In many cases, a history of alcoholism is present. Thus the location of this patient's pain and his lower GI bleeding are not consistent with chronic pancreatitis.

Duodenal ulcer (choice B) may present as epigastric pain, and with severe disease, severe bleeding may be present. Patients with duodenal ulcer rarely have diarrhea and weight loss. Thus this diagnosis is unlikely.

Infectious colitis (choice C) presents as abdominal pain and bleeding. Many infectious agents may cause GI bleeding, including Salmonella, Shigella, Campylobacter jejuni, and E. coli. The chronic nature of this patient's complaints and the lack of sick contacts suggests a different diagnosis.

Ischemic colitis (choice E) presents as acute onset of severe abdominal pain often with copious bright red blood per rectum. On examination, they display the classic finding of "pain out of proportion to examination." They are typically elderly patients with a history of atherosclerotic or embolic disease.

A2

The correct answer is E. Pernicious anemia is a hypochromic, megaloblastic anemia that may be associated with neurologic complications. It occurs as a result of a lack of vitamin B 12. The B12/intrinsic factor complex is absorbed in the terminal ileum by active transport. If this patient's ulcerative colitis extended into the terminal ileum, this condition could complicate his disease. Crohn disease almost invariably affects the terminal ileum, and this malabsorptive condition is more common in that setting. Ulcerative colitis usually affects only the colon, but ileal extension has been observed.

Diabetes mellitus (choice A) is an endocrine condition, and is unrelated to the absorptive capacity of the terminal ileum.

Folate (choice B) is absorbed in the proximal small intestine. Ileal involvement would not affect its absorption.

Iron (choice C) is also absorbed in the proximal small intestine. Ileal involvement would not affect its absorption.

Kwashiorkor (choice D) is protein malnutrition. Protein is absorbed throughout the small intestine. Ileal involvement would not affect its absorption.

A3

The correct answer is E. Granular, flat mucosa with ulcers, crypt abscesses, and pseudopolyps are characteristic findings in ulcerative colitis.

Celiac disease (choice A) is a disease of the intestine resulting from a hypersensitivity to the protein gluten. The intestinal mucosa is smooth and atrophic.

Clostridium difficile colitis (choice B) or "pseudomembranous colitis" is a colonic infection seen after extensive antibiotic use, which disturbs the colonic flora, promoting overgrowth of C. difficile. Fibrinous pseudomembranes are seen in the colon at colonoscopy.

Endoscopic evaluation of Crohn disease (choice C) reveals swollen mucosa with transverse fissures and linear ulcers. Biopsy findings demonstrate transmural involvement with granuloma formation.

Diverticula are outpouchings of the intestinal mucosa. They may bleed, or they may become infected, leading to a painful condition, diverticulitis. The findings here do not suggest diverticulosis (choice D).

A4

The correct answer is C. This patient's chronic course with acute exacerbation suggests that this patient has viscus perforation with peritonitis secondary to exacerbation of his ulcerative colitis. The inflammatory processes in ulcerative colitis can be so severe that erosion from inflammation can cause colonic perforation. Bowel contents then leak into the peritoneal cavity, causing peritonitis. Peritonitis is characterized by fever, severe abdominal pain, abdominal tenderness to palpation and percussion, and rigidity of the abdominal wall.

Abdominal aortic aneurysm rupture (choice A) presents as abdominal pain that radiates to the back. It is accompanied by hemodynamic instability that may deteriorate to shock. This presentation is not consistent with findings in this patient.

Acute pancreatitis (choice B) can cause severe abdominal pain and fever. The pain, however is usually epigastric and radiating to the back. Typically nausea and vomiting accompany pancreatitis. Amylase and lipase are elevated.

This patient does not display the symptoms of sepsis (choice D). In sepsis, patients are febrile with hemodynamic instability.

Ischemic colitis (choice E) can lead to perforation and peritonitis, and if the patient had symptomatology consistent with ischemic colitis, it could be the source of this patient's peritonitis. This patient did not report bright red blood per rectum, or "pain out of proportion to examination," making ischemic colitis less likely.

Gastrointestinal Bleeding case 3

A 55-year-old man with a history of coronary artery disease and alcoholism presents to the emergency department complaining that he vomited bright red blood twice this morning. He denies previous episodes of bleeding or abdominal pain. On examination, he is a malnourished man in acute distress. His blood pressure is 90/50 mm Hg and his pulse is 110/min. His mucous membranes are dry and his sclera are icteric. Abdominal examination reveals a distended abdomen with an enlarged, palpable spleen. Purplish striae are seen around the umbilicus. On rectal examination, Iarge hemorrhoids are seen, but the stool is negative for blood.

Q 1

Which of the following is the most likely diagnosis?

/ A. Erosive gastritis

/ B. Esophageal varices

/ C. Infectious enteritis

/ D. Mallory Weiss tear

/ E. Peptic ulcer disease

Q 2

Which of the following coagulation factors would most likely be unaffected in this patient?

/ A. Factor ll

/ B. Factor VII

/ C. Factor IX

/ D. Factor XIII

/ E. Von Willebrand's factor

Q 3

Which of the following anatomic relationships provides the basis for the patient's hemorrhoids?

/ A. Coronary vein anastomosis with the esophageal plexus

/ B. Inferior rectal vein anastomosis with the iliac vein

/ C. Paraumbilical vein anastomosis with the inferior epigastric vein

/ D. Superior mesenteric vein anastomosis with the splenic vein

/ E. Superior rectal vein anastomosis with the inferior and middle rectal vein

Q 4

Which of the following structures are found in the portal triad?

/ A. Hepatic vein, common hepatic artery, common bile duct

/ B. Portal vein, celiac artery, common bile duct

/ C. Portal vein, common hepatic artery, common bile duct

/ D. Portal vein, falciform ligament, common bile duct

/ E. Portal vein, sinusoids, bile canaliculi

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Gastrointestinal Bleeding case 3 answers

A1

The correct answer is B. While all of the answer choices listed must be considered in the differential, upper gastrointestinal bleeding from esophageal varices is most likely. This patient displays many of the stigmata of hepatic disease and portal hypertension: icteric sclera, hemorrhoids, distended umbilical veins (caput medusae), and a history of alcoholism. In this setting, esophageal varices would be the most likely. To make this diagnosis definitively, however, one needs to examine the gastrointestinal tract endoscopically.

Erosive gastritis (choice A) is a source of upper gastrointestinal hemorrhage, but it seldom bleeds so profusely that the patient becomes hemodynamically unstable.

Infectious disease in the gastrointestinal tract (choice C) may produce hemorrhage, but it tends to produce lower GI bleeding.

Mallory Weiss tears (choice D) produce upper GI bleeding. This tearing of the gastroesophageal junction occurs in alcoholics, but usually a history of retching precedes bleeding. No such history is elicited here.

Peptic ulcer disease (choice E) can produce brisk upper GI bleeding. It is less likely in this case because this patient has no history of GI pain.

A2

The correct answer is E. Von Willebrand's factor is a coagulation factor produced by the vascular endothelium and megakaryocytes. It is the only protein in the cascade that is not synthesized in the liver. vWF mediates the adhesion of platelets to the vessel wall basement membrane after vascular injury. Patients with a deficiency of von Willebrand's factor have a tendency to bleed. It is an autosomal dominant disease, and the ristocetin cofactor activity test is the best way to clinically assess vWF function.

Factor II (choice A) is produced in the liver. Deficiency is very rare, but can produce spontaneous or posttraumatic bleeding.

Factor VII (choice B) is produced in the liver.Severe factor VII deficiency is a very rare cause of bleeding.

Factor IX (choice C) is produced in the liver. A factor IX deficiency is known as hemophilia B, which is an X-linked disease.

Factor XIII (choice D) is produced in the liver. A deficiency of factor XIII produces delayed bleeding and poor wound healing.

A3

The correct answer is E. The patient's hemorrhoids are a consequence of his portal hypertension. The patient has a cirrhotic liver, which impedes circulation in the portal system. As the pressure rises in the portal system, blood in the portal circulation begins to backflow into the caval circulation. At the sites at which the portal system anastomoses with the caval circulation, venous engorgement occurs. At one such site, the confluence of the superior rectal vein (portal) with the middle and inferior rectal vein (caval), this venous engorgement leads to hemorrhoids.

The coronary vein anastomosis with the esophageal venous plexus (choice A) provides the anatomic basis for the esophageal varices seen in portal hypertension. As pressure builds in the portal system, venous engorgement occurs, and varices are produced in the distal esophagus. These varices can be the site of life-threatening upper GI bleeding.

The anastomosis of the inferior rectal vein with the iliac vein (choice B) is a caval-caval anastomosis and would not be affected by portal hypertension.

The anastomosis of the paraumbilical vein and the inferior epigastric vein (choice C) is the portal-caval anastomosis responsible for the purplish striae or caput medusae seen on this patient's abdomen. This circulatory route is an embryologic remnant, and is only patent when portal pressure rises high enough to re-open this pathway.

The anastomosis of the superior mesenteric vein and the splenic vein (choice D) marks the origin of the portal vein. It may have an elevated pressure, but it is not the basis for hemorrhoids.

A4

The correct answer is C. The portal triad contains the portal vein, common hepatic artery, and common bile duct. It is found in the fold of peritoneum, called the hepatoduodenal ligament, that separates the greater and lesser abdominal sacs.

None of the other choices offer a complete answer:

The hepatic vein (choice A) drains the liver into the inferior vena cava (IVC).

The celiac artery (choice B) supplies blood to the anatomic foregut. One of its branches, the common hepatic artery, travels in the porta hepatis.

The falciform ligament (choice D) is the remnant of the umbilical vein that passes from the anterior abdominal wall to the superior surface of the liver.

Bile canaliculi (choice E) are microscopic channels that drain bile from the hepatocytes.

Gastrointestinal Bleeding case 2

A 9-day-old baby is noted to be lethargic and has been feeding poorly. Over the next day, the baby develops bilious vomiting, a distended tender abdomen, and bloody stools.

Q 1

Which of the following diseases would most likely cause gastrointestinal bleeding in a neonate?

/ A. Crohn disease

/ B. Cystic fibrosis

/ C. Diverticulitis

/ D. Necrotizing enterocolitis

/ E. UIcerative colitis

Q 2

Which of the following is considered the most important risk factor for this patient's disease?

/ A. Perinatal asphyxia

/ B. Polycythemia

/ C. Prematurity

/ D. Respiratory distress syndrome

/ E. Shock

Q 3

A plain radiograph of the abdomen demonstrates gas within the bowel walI (pneumatosis). Which of the following would most likely be

associated with this finding?

/ A. Air in the biliary tract

/ B. BIood in the biliary tract

/ C. Gas in the hepatic veins

/ D. Gas in the mediastinum

/ E. Gas in the portal vein

Q 4

The baby's condition continues to deteriorate, and the decision is made to surgically resect the affected GI segment. Resection of which of the

following areas of the gastrointestinal tract would most likely produce severe long-term malabsorption?

/ A. Ascending colon

/ B. Duodenum

/ C. Jejunum

/ D. Stomach

/ E. Terminal ileum

Q 5

The baby's resected gastrointestinal segment would be most likely to show which of the following on pathologic examination?

/ A. Distended macrophages with PAS-positive granules in the submucosa

/ B. Gangrenous intestinal wall

/ C. Granuloma formation

/ D. Neoplastic epithelial proliferation

/ E. Outpouching of intestinal mucosa through the muscular layer

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Gastrointestinal Bleeding case 2 answers

A1

The correct answer is D. Necrotizing enterocolitis is a feared complication of infancy. It has an incidence of 1 to 5% in neonatal intensive care unit admissions. The condition is a necrotizing disease of the small intestine, and sometimes, the colon. The pathogenesis is still not clear, but may involve an ischemic insult leaving the bowel susceptible to bacterial overgrowth. Necrotizing enterocolitis may develop suddenly, with features suggesting neonatal sepsis, or more slowly, over a period of one or two days. The case description illustrates typical features.

Crohn disease (choice A) and ulcerative colitis (choice E) may present as early as in the teenage years, but not usually in infancy.

Cystic fibrosis (choice B) is a cause of meconium ileus and later malabsorption, but does not typically present with gastrointestinal bleeding.

Diverticulitis (choice C) is usually a disease of middle-aged to older adults.

A2

The correct answer is C. Prematurity is the most important risk factor for necrotizing enterocolitis, although term infants also sometimes develop the condition. Clinical series have reported that between 60 and 95% of affected babies are premature, and the incidence is markedly increased in babies born at lower gestational ages.

Many other purported risk factors have also been cited but seem to have a lesser effect, including perinatal asphyxia (choice A), respiratory distress syndrome (choice D), umbilical catheterization, hypothermia, shock (choice E), patent ductus arteriosus, cyanotic congenital heart disease, polycythemia (choice B), thrombocytosis, anemia, exchange transfusion, congenital GI anomalies, chronic diarrhea, non-breast milk formula, nasojejunal feedings, hypertonic formula, and colonization with necrogenic bacteria. It may simply be that any already fragile baby, particularly if premature, who has other significant underlying disease, is at increased risk for developing necrotizing enterocolitis.

A3

The correct answer is E. Portal venous gas is seen in association with pneumatosis intestinalis, most commonly with necrotizing enterocolitis. The physiology of this is that the portal vein, via the mesenteric veins, drains nutrient-rich blood from the gut to the liver. In the case of necrosis with air in the bowel wall, air migrates into the portal venous system and to the liver. On CT, this has the characteristic appearance of peripheral lucencies following the portal venous system intrahepatically. In cases of more severe pneumatosis, the bowel may rupture and lead to pneumoperitoneum.

Note: Although this item may have seemed difficult, it was, in essence, a straightforward pathophysiology question, i.e., "Where would gas in the wall of the intestine go?" The distracter explanations give additional information concerning the radiographic appearance of the other conditions (the following will most likely NOT be tested on Step I of the USMLE).

Pneumobilia, or air in the biliary tract (choice A), would be seen after instrumentation of the biliary system, such as after an endoscopic retrograde cholangiopancreatogram (ERCP). Other causes include a gas-forming infection within the biliary tree or previous sphincterotomy (endoscopic opening of the sphincter of Oddi). Pneumobilia has a distinct appearance on CT: there is gas located centrally in the liver within the ducts.

Hemobilia, or blood in the biliary tract (choice B), would be seen after instrumentation of the biliary system, such as after an endoscopic retrograde cholangiopancreatogram (ERCP), from a biliary or hepatic tumor, or secondary to a hypocoagulable state. Hemobilia is found at endoscopy, and is generally not visible on plain radiographs. High attenuation material may be seen within the bile ducts on a CT scan, suggesting hemobilia.

Hepatic venous gas (choice C) would not be seen with pneumatosis because the hepatic veins drain the liver into the inferior vena cava (IVC). Gas from the bowel wall gets trapped in the portal veins and does not traverse the liver to get into the hepatic veins.

Pneumomediastinum (choice D) is usually from thoracic trauma causing rupture of the esophagus or pneumothorax. Gas within the soft tissues of the head and neck may dissect to the mediastinum. Rarely, pneumoperitoneum may lead to secondary pneumomediastinum. Pneumatosis without pneumoperitoneum would not lead to pneumomediastinum.

A4

The correct answer is E. Babies with early necrotizing enterocolitis are sometimes successfully managed medically with fluids, bowel rest, and correction of anemia and thrombocytopenia that may have developed secondary to the gastrointestinal bleeding. Surgical resection may be necessary in more severe cases of necrotizing enterocolitis, but may have a mortality of 30-40% in these deathly ill infants. Unfortunately, necrotizing enterocolitis most often affects the terminal ileum, which is also the site most necessary to prevent long-term malnutrition. In practice, more than 50% of the bowel must usually be removed before substantial malabsorption occurs. The ileum is the site that is most active in nutrient (particularly fats) absorption, vitamin B12 absorption, and conjugated bile salt absorption.

The ascending colon (choice A) is good at absorbing water and has a small capacity for absorbing carbohydrates.

The duodenum (choice B) and jejunum (choice C) are also important absorptive sites, but are less of a long-term problem because the ileum appears to usually have the capacity to replace their absorptive function after proximal small intestine resection.

Nutrient absorption does not usually occur in the stomach (choice D).

A5

The correct answer is B. The intestinal wall in early necrotizing enterocolitis shows edema, hemorrhage, and necrosis. In more advanced disease, gangrenous necrosis of the full bowel thickness is seen, and necrotic inflammatory debris may adhere to the mucosal surface. Some cases show evidence of reparative change, such as epithelial regeneration and granulation tissue formation, suggesting that the lesion may have evolved over several days before becoming clinically obvious.

Choice A is a feature of Whipple disease.

Choice C is a feature of Crohn disease.

Choice D is a feature of colonic polyps and cancers.

Choice E is a feature of diverticulitis.

Gastrointestinal Bleeding case 1

A 60-year-old man comes to the emergency department complaining of bright red blood per rectum. The bleeding began abruptly several hours prior to his visit. He has light-headedness when he stands up rapidly, but has no abdominal pain, cramping, fever, nausea, or vomiting. He has no history of previous episodes of bleeding or abdominal pain, but has a history of coronary artery disease and takes aspirin as a "blood thinner." He is afebrile, slightly hypotensive and tachycardic, but stable. On examination, he has decreased skin turgor, and dry mucous membranes. He has no abdominal tenderness. Rectal examination is positive for gross blood.

Q 1

Which of the following is the most likely diagnosis?

/ A. Arteriovenous malformation

/ B. Diverticulitis

/ C. Infectious colitis

/ D. Ischemic colitis

/ E. UIcerative colitis

Q 2

After the patient has stabilized, a colonoscopy is performed to elucidate the origin of the bleeding. Several star-shaped branching vessels

measuring 0.2 to 1.0 cm are seen in the colonic submucosa. BIeeding is stopped by electrocoagulation. A diagnosis of lower gastrointestinal

bleeding is given. Which anatomic landmark demarcates upper gastrointestinal bleeding from lower gastrointestinal bleeding?

/ A. IIeocecal valve

/ B. Ligament of Treitz

/ C. Papilla of Vater

/ D. Pylorus

/ E. Splenic flexure of the colon

Q 3

The aspirin taken by this patient represents a contributor to his condition. Which of the following best describes the mechanism of action of

aspirin?

/ A. Aspirin decreases the serum level of factor VIII

/ B. Aspirin decreases the serum level of factor IX

/ C. Aspirin irreversibly inhibits platelets

/ D. Aspirin irreversibly inhibits thrombin

/ E. Aspirin reversibly inhibits platelets

/ F. Aspirin reversibly inhibits thrombin

Q 4

Which of the following is an important mechanism in short-term blood pressure maintenance?

/ A. BIood pressure regulation occurs slowly by endocrine mechanisms only

/ B. Decreased stretch in the carotid bodies decreases sympathetic and increases parasympathetic discharge to the heart

/ C. Decreased stretch in the carotid bodies increases sympathetic and decreases parasympathetic discharge to the heart

/ D. Decreased stretch in the carotid sinus decreases sympathetic and increases parasympathetic discharge to the heart

/ E. Decreased stretch in the carotid sinus increases sympathetic and decreases parasympathetic discharge to the heart

Q 5

Normal saline is administered to this patient and his blood pressure and heart rate normalize. One of the goals in fluid resuscitation is to

optimize cardiac parameters according to Starling's Law. Starling's Law describes which of the following?

/ A. The relationship between end diastolic volume and contractility

/ B. The relationship between heart rate and stroke volume

/ C. The relationship between preload and afterload

/ D. The relationship between stroke volume and end systolic volume

/ E. The relationship between systemic vascular resistance and cardiac output

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Gastrointestinal Bleeding case 1 answers

A1

The correct answer is A. Painless hematochezia or bright red lower GI bleeding can come from many sources. While bright red lower GI bleeding tends to indicate lower GI bleeding (bleeding distal to the ligament of Treitz), brisk upper GI bleeding can also be the source. The clinical manifestations of such bleeding range from negligible to hemodynamic instability, depending upon the rate of bleeding. The differential diagnosis for painless hematochezia includes AV malformations, gastric erosions, esophageal varices, esophagitis, duodenal or gastric ulcer, hemorrhoids, diverticulosis, and colonic neoplasm.

Diverticulitis (choice B) occurs when a colonic outpouching or diverticulum becomes inflamed. Patients tend to be elderly and present with fever, abdominal pain, and abdominal tenderness on examination. While painful, these lesions do not bleed significantly (unlike their uninflamed counterparts in diverticulosis).

Infectious colitis (choice C) may present as rectal bleeding, but this bleeding is typically accompanied by pain, cramping, and fever. Causative organisms may include Salmonella, Shigella, Campylobacter jejuni, E. coli, and Entamoeba histolytica.

Ischemic colitis (choice D) may have rectal bleeding, but the hallmark of ischemic colitis is severe abdominal pain out of proportion to examination findings.

Ulcerative colitis (choice E) presents as abdominal pain and diarrhea, which may be bloody or nonbloody. In addition, the onset of the disease tends to be earlier, so this patient would likely have had previous episodes of pain

A2

The correct answer is B. The ligament of Treitz, or the peritoneal ligament, which separates the third (retroperitoneal) portion of the duodenum from the fourth (peritoneal) portion of the duodenum, traditionally demarcates upper GI bleeding from lower GI bleeding. Bleeding proximal to this landmark tends to produce melena or black tarry stools. Bleeding distal to this landmark tends to produce hematochezia or red blood per rectum.

The ileocecal valve (choice A) separates the terminal ileum from the cecum.

The papilla of Vater (choice C) is where the pancreatic duct and common bile duct empty into the duodenum.

The pylorus (choice D) is the sphincter separating the stomach from the duodenum.

The splenic flexure of the colon (choice E) marks the transition from transverse colon to the descending colon.

A3

The correct answer is C. Patients with gastrointestinal bleeding must be assessed for anatomic as well as physiologic and pharmacologic sources of bleeding. Aspirin acts as an anticoagulant by irreversibly inhibiting platelets, preventing the formation of a clot by blocking platelet adhesion and aggregation. Since this platelet mass acts as a matrix for fibrin clot formation, blocking platelets prevents clot formation. This mechanism has been utilized in patients with atherosclerotic disease to prevent intravascular clot formation, but may aggravate bleeding conditions such as this.

Aspirin does not decrease the serum level of factor VIII (choice A). Factor VIII deficiency is the pathophysiology behind hemophilia A.

Factor IX deficiency (choice B) is associated with hemophilia.

Aspirin does not inhibit thrombin (choices D and F). Thrombin is the enzyme responsible for cleaving fibrinogen to fibrin.

Aspirin's effects on platelets are not reversible (choice E), and a new population of functional platelets must replace the inhibited platelets before coagulation is fully restored.

A4

The correct answer is E. As blood pressure falls in this patient with hypovolemia, many short term and long term mechanisms work to raise the falling pressure. In the short term, the baroreceptors found in the carotid sinus and aortic arch regulate blood pressure by modulating the autonomic nervous system. As pressure falls in this patient, the baroreceptors sense this change as a decrease in stretch in the vessel walls. Afferent fibers from the baroreceptors then "report" this change to the medullary cardiovascular center. This center responds by increasing sympathetic discharge and decreasing parasympathetic discharge to the heart and resistance vessels. This acts to restore the blood pressure by increasing heart rate, stroke volume, and vascular resistance.

While endocrine mechanisms (choice A) restore mean arterial pressure for the long term, the sympathetic mechanisms outlined above restore pressure toward baseline much more rapidly.

Choices B and C are incorrect. The carotid bodies contain chemoreceptors (not stretch receptors) that detect changes in PO₂, PCO₂, and pH. They restore these parameters to normal by acting through the medullary centers to change heart rate, stroke volume, vascular resistance, and ventilatory parameters.

The decrease in pressure triggers an increase in sympathetic discharge and decrease in parasympathetic discharge (compare with choice D).

A5

The correct answer is A. Starling's law of the heart describes the relationship between end diastolic volume or preload and cardiac contractility. It states that cardiac contractility is maximized at a particular preload. It also states that cardiac contractility declines as the preload is increased or decreased from this optimum. The basis for this principle is that at a particular preload, the myocardium is "stretched" to a point that maximizes the number of actin and myosin units that may interact in a given contraction.

Choice B is incorrect. Heart rate x stroke volume = cardiac output

Choice C is incorrect. Preload is related to end diastolic volume and passive wall tension exerted on the diastolic ventricle.

Choice D is incorrect. End diastolic volume - end systolic volume = stroke volume

Choice E is incorrect. Mean arterial pressure = cardiac output x total peripheral resistance.