Abdominal Pain Case 3

A 64-year-old man with a history of coronary artery disease (CAD) comes to the emergency department with the acute onset of severe, constant, Lower abdominal pain and rectal bleeding. He reports that he previously has had several episodes of similar, but less severe pain.

About 12 hours after the onset of pain, the patient began passing copious bright red blood per rectum. He denies nausea, vomiting, sick contacts, or foreign traveI. Initial physical examination reveals a distressed man, who is afebrile, but tachypneic, with scant diffuse abdominal tenderness to palpation. Rectal examination is positive for blood. Laboratory studies reveal a metabolic acidosis with an elevated serum Iactate.

Q 1

Which of the following is the most likely diagnosis?

/ A. Colon carcinoma

/ B. Infectious colitis

/ C. Inflammatory bowel disease

/ D. Ischemic colitis

/ E. Necrotizing enterocolitis

Q 2

The lactate produced from the anaerobic metabolism in the infarcted gut will likely be which of the following?

/ A. Exhaled as a fruity odor

/ B. Incorporated into glycogen in the liver

/ C. Incorporated into myoglobin in muscle

/ D. Incorporated into urea in the urine

/ E. Secreted by the kidneys unchanged

Q 3

If this patient's disease were drug-induced, which of the following agents would most likely be responsible?

/ A. Acetaminophen

/ B. Amiodarone

/ C. Cocaine

/ D. Dexamethasone

/ E. Nitroglycerin

Q 4

While the patient is in the emergency department, the pain becomes increasingly severe. Several hours after his initial examination, the patient becomes febrile and is now exquisitely tender to palpation. He writhes in pain when the physician jostles the bed. Air is seen under the diaphragm in an upright chest x-ray film. These new findings suggest which of the following?

/ A. Abdominal aortic aneurysm

/ B. Bowel obstruction

/ C. Cholecystitis

/ D. Hypovolemia

/ E. Perforation with peritonitis

Q 5

Upon surgical exploration of the abdomen, the colon is dull and dusky from the mid transverse colon to the rectum. The patient has occluded

which of the following vessels?

/ A. Celiac trunk

/ B. Cystic artery

/ C. External iliac artery

/ D. Inferior mesenteric artery

/ E. Superior mesenteric artery

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Abdominal Pain Case 3 Answers

A1

The correct answer is D. A patient with severe abdominal pain and rectal bleeding with an unremarkable physical examination is likely suffering from ischemic colitis. "Pain out-of-proportion to examination" is a classic finding for ischemic colitis. The previous episodes of less severe pain represent ischemic angina. An infarction has occurred, as indicated by the rise in serum lactate secondary to the colon's anaerobic metabolism. The history of coronary artery disease also suggests this diagnosis, as the atherosclerotic processes that contribute to his CAD are also likely present in his abdominal vasculature.

Colon cancer (choice A) would produce less acute symptoms, but occasionally, colon cancer may present acutely with obstructive symptoms. Patients may have bleeding and abdominal pain, but the pain is typically intermittent and accompanied by nausea, vomiting, abdominal distention, and absence of flatus.

Infectious colitis (choice B) is incorrect. While patients may have bleeding and abdominal pain, nothing in the history suggests a disease of infectious origin (no sick contacts or foreign travel). The acute onset also suggests a vascular event, rather than an infectious one.

Inflammatory bowel disease (IBD) (choice C) is incorrect because while the patient reports previous episodes, an elderly man with IBD would likely have a chronic history of abdominal pain and bleeding.

Necrotizing enterocolitis (choice E) affects premature infants and would not be relevant in this setting.

A2

The correct answer is B. Lactate is converted into glucose, and then glycogen in the liver by a process know as the Cori cycle.

Choice A is incorrect, as lactate would not be exhaled. A fruity odor on the breath would be a sign of ketoacidosis.

While some of the carbon from the lactate may be incorporated into peptides via Krebs intermediates (e.g., choice C), the vast majority would be left as carbohydrate.

Urea (choice D) represents a means of eliminating nitrogenous waste.

Choice E is wrong, as the kidneys would retain the lactate, rather than excreting it.

A3

The correct answer is C. Cocaine is a sympathomimetic drug that indirectly acts on both the alpha and beta adrenergic receptors on the vasculature. As such, cocaine may cause vasospasm in the abdominal vasculature leading to infarction and ischemic colitis. Similar vasospastic events may occur in the coronary vasculature, leading to myocardial infarction.

Acetaminophen (choice A) is an analgesic, and would not play a role in producing ischemic colitis.

Amiodarone (choice B) is an antiarrhythmic, and would not contribute to ischemic colitis.

Dexamethasone (choice D) is a steroidal anti-inflammatory drug. Not only would this medication not cause ischemic colitis, it might mask the symptoms due to its potent anti-inflammatory properties.

Nitroglycerin (choice E) is a venodilator, and would not contribute to ischemic colitis. As a venodilator, nitroglycerin is used to treat coronary ischemia by reducing cardiac preload.

A4

The correct answer is E. This patient has experienced a bowel perforation. Air under the diaphragm in an upright chest film provides definitive evidence that a hollow viscus has ruptured. Air near the liver on a left lateral decubitus (patient lays with the left side down) is an alternative study to demonstrate perforation. Spillage from the perforated bowel has irritated and inflamed the peritoneum, resulting in peritonitis. Symptoms of peritonitis include extreme, sharp pain exacerbated by jostling (patients often report that the bumpy ride to the emergency department caused extreme pain). Patients will be exquisitely tender to palpation and percussion and may have abdominal rigidity. Fever typically accompanies peritonitis.

While an abdominal aortic aneurysm or AAA (choice A) presents as acute abdominal pain, this pain is described as tearing and may radiate to the back. A pulsatile abdominal mass may be palpated. The air on the chest film is also inconsistent with AAA.

This patient does not have bowel obstruction (choice B). Signs and symptoms of bowel obstruction include: nausea, vomiting, intermittent abdominal pain, hypovolemia, abdominal distention, absence of flatus, and a "step ladder" bowel pattern on abdominal films.

Cholecystitis (choice C) typically presents as right upper quadrant (RUQ) pain, fever, and jaundice. Patients usually have a history of colicky RUQ pain.

While the patient is at risk for hypovolemia (choice D), none of the symptoms listed typify hypovolemia. Signs and symptoms of mild to moderate hypovolemia include malaise, dry mouth, thirst, decreased skin turgor, tachycardia, hypotension, and decreased urine output.

A5

The correct answer is D. The inferior mesenteric artery distributes blood to the embryologic hindgut. This includes the distal 1/3 of the transverse colon to the rectum. The rectum is spared because it receives circulation from the inferior rectal artery (not mesenteric).

The celiac trunk (choice A) supplies the embryologic foregut. The first three branches include the splenic artery, the left gastric artery, and the common hepatic artery. This patient has no findings in this distribution.

The cystic artery (choice B) supplies the gall bladder. There are no gall bladder findings in this case.

The external iliac artery (choice C) gives rise to the vessels of the lower extremity. Symptoms of occlusion or stenosis might include buttock and thigh pain exacerbated by walking. Severe stenosis might give patients buttock and thigh pain, even at rest.

The superior mesenteric artery (choice E) supplies the embryologic hindgut. This extends from the duodenum to the proximal 2/3 of the transverse colon