Abdominal Pain Case 5

A 17-year-old boy is taken to the emergency department because he has developed severe abdominal pain. The pain began abruptly several hours previously, and was felt initially in the periumbilical region, but later shifted to the right lower quadrant. The boy had initially felt somewhat nauseous, but this has passed. On physical examination, he is noted to have localized pain on cough and to be running a low-grade fever.

Q 1

Examination of the abdomen demonstrates right lower quadrant tenderness at the junction of the middle and outer thirds of the line joining the umbilicus to the anterior superior spine of the iliac. This location is known as which of the following?

/ A. Gubernaculum

/ B. Langer's line

/ C. Linea alba

/ D. McBurney's point

/ E. Tunica albuginea

Q 2

Which of the following is the most likely diagnosis?

/ A. Appendicitis

/ B. Diverticulitis

/ C. Gallstones

/ D. Rectal ulcer

/ E. Renal colic

Q 3

The patient also exhibits an increase in pain in the right lower quadrant from the passive extension of the right hip joint. This finding suggests that the inflammation also involves which of the following?

/ A. BIadder

/ B. External oblique muscle

/ C. Femur

/ D. IIiopsoas muscle

/ E. Transverse abdominal muscle

Q 4

The patient is prepared for immediate surgery. Cefotaxime is administered before, during, and after surgery. The specimen, once removed, is sent to the laboratory for pathology and bacteriologic culture. A malodorous pus surrounds the serosa of the surgical specimen, and a mixed gram-negative flora is cultured. Rapid enzyme tests for beta-Iactamase production are positive. Which of the following drugs should be added to the initial cefotaxime regimen?

/ A. Bacitracin

/ B. CIavulanic acid

/ C. CIindamycin

/ D. Isoniazid

/ E. Vancomycin

Q 5

The patient's postoperative recovery is uneventfuI, but 10 days after discharge, he returns to his physician complaining of continuous low-grade fever. An abscess is drained transrectally, and organisms are cultured from the pus. Which of the following is an attribute of this organism that makes it an important abscess former?

/ A. It is an anaerobe

/ B. It is an intracellular pathogen

/ C. Its endotoxin lacks 2,3-ketodeoxyoctonate

/ D. Mycolic acid

/ E. Prodigious capsule

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Abdominal Pain Case 5 Answers

A1

The correct answer is D. The point described is McBurney's point, which overlies the location of the appendix in most individuals.

The gubernaculum (choice A) is the fibrous cord that connects the primordial testis or ovary to the anterolateral abdominal wall.

Langer's lines (choice B) are the cleavage lines of the skin.

The linea alba (choice C) is a sheet-like aponeurosis that covers the anterior abdominal wall.

The tunica albuginea (choice E) is a tough fibrous coat that covers the testis.

A2

The correct answer is A. This patient has a typical presentation for appendicitis, and the diagnosis is confirmed by the presence of localized tenderness at McBurney's point.

Diverticulitis (choice B) is usually a disease of middle-aged or older individuals and most commonly affects the left-lower quadrant.

Symptomatic gallstone disease (choice C) causes pain and tenderness in the right upper quadrant.

Rectal ulcer (choice D) causes pain with stool movement, but does not usually produce tenderness identifiable on abdominal examination.

Renal colic (choice E) usually produces flank or lower back pain.

A3

The correct answer is D. This patient has a "positive psoas sign," which is an increase in pain from passive extension of the right hip joint. This maneuver stretches the iliopsoas muscle, which lies behind the appendix and can become secondarily inflamed when the appendiceal inflammation extends through the serosa. The psoas sign is clinically useful in both confirming the appendix as the probable origin of the patient's pain, and indicating that the inflammation is transmural and that the risk of rupture and peritonitis is increased.

The bladder (choice A) is located more medially, and is usually not affected by appendicitis.

The external oblique (choice B) and transverse abdominal (choice E) muscles are in the anterior and lateral abdominal walls, and do not usually become inflamed with appendicitis.

The femur (choice C) is moved during the extension of the right hip joint, but is not the source of the pain.

A4

The correct answer is B. Clavulanic acid is a beta-lactamase inhibitor, which when administered with beta lactam agents, irreversibly binds and inactivates bacterial beta-lactamases, thereby permitting the companion drug to disrupt bacterial cell wall synthesis. Suspected appendicitis is usually treated with prompt appendectomy, since delay is associated with increased risk of potentially life-threatening peritonitis and sepsis.

Bacitracin (choice A) is not correct, since this drug inhibits bacterial cell wall synthesis by binding to and inhibiting the dephosphorylation of a membrane-bound lipid pyrophosphate. Gram-negative bacteria are resistant to this agent, and it would not have a synergistic effect if administered with a third generation cephalosporin.

Clindamycin (choice C) is not correct, because this drug blocks protein elongation by binding to the 50S ribosome. Although it is effective against anaerobic gram-negative bacilli, it would not have a complementary effect when administered with a third generation cephalosporin.

Isoniazid (choice D) is not correct because it inhibits the synthesis of mycolic acids for the cell wall of actively dividing Mycobacteria. It would not be effective in the flora of this patient's gut, nor would it act synergistically with third generation cephalosporins.

Vancomycin (choice E) is not correct because it disrupts cell wall synthesis in growing gram-positive bacteria. It would not be effective against the flora of this patient's gut, nor would it act synergistically with third generation cephalosporins.

A5

The correct answer is E. Prevotella (Bacteroides) is a frequent cause of abscesses in the intestinal tract because it is a normal flora organism and produces a large capsule, which impedes phagocytosis.

Although the genus is anaerobic (choice A), it is not this attribute which causes its formation of abscesses.

Prevotella is extracellular, not an intracellular pathogen (choice B).

Although Prevotella does indeed have this type of endotoxin (choice C), the absence of this molecule decreases the toxicity of the toxin, and does not contribute to its proclivity toward abscess formation.

Mycobacteria, and not other genera such as Prevotella, are known for their long-chain fatty acids (mycolic acids; choice D).

Abdominal Pain Case 4

A 45-year-old man goes to an emergency department because he is experiencing severe abdominal pain, which is radiating straight through to his back. The pain began several hours after an admitted alcoholic binge, and has not changed in position, although it has become worse.

Q 1

Which of the following would be the most likely cause of this type of pain?

/ A. Acute appendicitis

/ B. Acute hepatitis

/ C. Acute pancreatitis

/ D. Chronic hepatitis

/ E. Myocardial infarction

Q 2

In addition to alcohol use, which of the following is a common predisposing factor for this patient's disease?

/ A. Biliary tract stones

/ B. Duodenal cancer

/ C. Gastric carcinoma

/ D. Kidney stones

/ E. Peptic ulcer

Q 3

Marked serum elevation of which of the following markers would most strongly substantiate the likely diagnosis?

/ A. Acid phosphatase

/ B. Amylase

/ C. Aspartate aminotransferase

/ D. AIkaline phosphatase

/ E. Creatinine kinase

Q 4

The patient has a severe course that requires treatment in an ICU. CIinically, he appears similar to patients with sepsis, with fever, elevated white count, hypotension, increased pulse rate, shallow and rapid breathing, oliguria, and a blunted sensorium, in addition to his pain and abdominal tenderness. These clinical findings are most likely related to which of the following?

/ A. Activation of the inflammatory cascade

/ B. AIcohol withdrawal symptoms

/ C. AIIergic reaction to alcohol

/ D. Drug toxicity effect

/ E. Secondary infection with mixed flora gut bacteria

Q 5

The patient's condition resolves in about two weeks, but he continues to drink after leaving the hospitaI. When seen several years later, he has had a number of similar episodes, and now has chronic severe abdominal pain. CT scan demonstrates a single, smooth-walled, fluid filled space in the tail of the pancreas, which can be reached by the radiologist for CT-guided aspiration with an approach from the back. The fluid aspirated is yellowish, clear, and acellular. Which of the following is the most likely diagnosis?

/ A. Pancreatic microcystic adenoma

/ B. Pancreatic mucinous cystadenocarcinoma

/ C. Pancreatic mucinous cystadenoma

/ D. Pancreatic pseudocyst

/ E. Pancreatic solid-cystic tumor

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Abdominal Pain Case 4 Answers

A1

The correct answer is C. The typical pain described occurs in approximately 50% of patients with acute pancreatitis. Other patients may have milder pain or even, uncommonly, pain first felt in the lower abdomen.

The pain of acute appendicitis (choice A) is often felt first as referred pain near the umbilicus, with tenderness on palpation in the left lower quadrant.

Acute hepatitis (choice B) can cause pain referred to the right shoulder.

Chronic hepatitis (choice D) does not usually cause pain.

Myocardial infarction (choice E) can cause substernal pain and pain radiating to the left shoulder.

A2

The correct answer is A. The overwhelmingly most common predisposing factors for acute pancreatitis are gallstones (more specifically tiny ones that lodge in the extrahepatic bile duct system) and alcohol abuse.

Rarely, nearby cancers (choices B and C) can occlude the pancreatic duct system and cause a secondary acute pancreatitis.

Kidney stones (choice D) have no relationship with pancreatitis.

Peptic ulcers (choice E) that erode into the pancreas can uncommonly secondarily inflame the pancreas

A3

The correct answer is B. The usual markers for pancreatitis are amylase and lipase. Marked elevation of amylase usually means either pancreatic disease or salivary gland disease; lipase will be elevated in pancreatic disease but not salivary gland disease. If you see elevated amylase on a USMLE question, you should think of pancreatitis or salivary gland disease (mumps, salivary gland stone). However, you should be aware, for your general medical knowledge, that modest elevations of amylase can be seen in a much wider variety of settings (often reflecting either subclinical pancreatic damage or hemoconcentration of pancreatic enzymes), including GI obstruction, mesenteric thrombosis and infarction, macroamylasemia (a genetic condition with abnormal amylase), renal disease, ruptured tubal pregnancy, lung cancer, acute alcohol ingestion, and following abdominal surgery.

Associate acid phosphatase (choice A) with diseases involving the prostate and, to lesser degrees, bone, the heart, platelets, and the liver.

Associate aspartate aminotransferase (choice C) with diseases of the heart, muscle, liver, pancreas (though not as important for diagnosis as amylase and lipase), and brain.

Associate alkaline phosphatase (choice D) with diseases of bone, liver, and to lesser degrees, lung and heart.

Associate creatinine kinase (choice E) with diseases of the heart, muscle, brain, and the general body (trauma, surgery).

A4

The correct answer is A. Acute pancreatitis can either be relatively mild, or a severe condition that may cause death. It is thought that, in severe cases, leakage of enzyme-containing pancreatic secretions into the tissues/and or blood stream causes cleavage of precursors, thus strongly activating the complement and inflammatory cascades. These, in turn, produce abundant cytokines, which worsen the symptoms. The clinical result is similar to sepsis, with risk of multi-organ failure and death. The treatment of acute pancreatitis is primarily supportive, and may include careful attention to fluid resuscitation, oxygen supplementation, cardiovascular support, dialysis, management of electrolyte abnormalities, pain control, and total parenteral nutrition.

Alcohol allergy (choice C) or withdrawal (choice B) do not play any additional part in most of these symptoms once the pancreatitis has developed.

Infection (choice E) and drug toxicity (choice D) are also not a necessary part of the clinical picture, although physicians may worry that the patient's general clinical status is masking other, potentially more treatable, problems.

A5

The correct answer is D. Pancreatic pseudocyst is a fairly common complication of both acute and chronic pancreatitis, and appears to develop when trapping of pancreatic digestive juices (containing amylase, lipase, and proteases) causes a "digestion" of part of the pancreas, leaving a fluid filled cystic space. The term "pseudocyst", rather than "cyst", is used by purists because the space does not have an epithelial lining, and is hence not a "true cyst". Pseudocysts are usually solitary and typically measure 5-10 cm in diameter. They can be surgically excised (and the surrounding tissue will typically show evidence of chronic pancreatitis in long-standing cases) or sometimes, if the anatomy is favorable, drained into adjacent hollow viscera. Some are medically managed if small.

Most true neoplasms of the pancreas contain (often large numbers of) smaller, multiple, cysts. These tumors can be benign or malignant, and the ones with mucus-secreting epithelium (choices B and C) are more common than those with a serous lining (choices A and E).

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

Abdominal Pain Case 2

A 47-year-old woman presents to the emergency department with cra mping/colicky abdominal pain. The current episode of pain began several hours ago, following a fatty meaI. The pain began slowly, and rose in intensity to a plateau over the course of several hours. The patient reports that she had had several other episodes of similar pain during the past several months, with long intervening periods of freedom from pain. On physical examination, she is noted to have tenderness to deep palpation in the right upper quadrant of the abdomen near the rib cage. The patient also reports that she is experiencing shoulder/back pain at a site she identifies near the right lower scapula, but no tenderness can be elicited during the back and shoulder examination.

Q 1

Which of the following organs is the most likely source of this woman's pain?

/ A. Appendix

/ B. Diaphragm

/ C. Esophagus

/ D. Gallbladder

/ E. Stomach

Q 2

Which of the following techniques would be most appropriate to demonstrate the patient's most likely diagnosis?

/ A. Colonoscopy

/ B. CT scan of the abdomen

/ C. Esophagoduodenoscopy

/ D. MRI scan of the abdomen

/ E. UItrasonography

Q 3

Following appropriate diagnostic studies, the patient is taken to the surgical suite. During the surgery, the surgeon inserts his fingers from

right to left behind the hepatoduodenal ligament. As he does so, his fingers enter which of the following?

/ A. Ampulla of Vater

/ B. Common bile duct

/ C. Epiploic foramen

/ D. Greater peritoneal sac

/ E. Portal vein

Q 4

During the cholecystectomy, the surgeon ligates the cystic artery. This is typically a branch of which of the following?

/ A. Gastroduodenal artery

/ B. Left gastroepiploic artery

/ C. Right gastroepiploic artery

/ D. Right hepatic artery

/ E. Superior pancreaticoduodenal artery

Q 5

Pathologic examination of the specimen removed by the surgeon demonstrates the presence of numerous yellow stones (shown above).

These are most likely composed primarily of which of the following?

/ A. Bilirubinate

/ B. Calcium phosphate

/ C. Cholesterol

/ D. Cystine

/ E. Struvite

Q 6

If this patient had a small stone lodge near the ampulla of Vater, which of the following complications would be most likely to occur?

/ A. Crohn disease

/ B. Diabetes mellitus

/ C. Pancreatitis

/ D. Peptic ulcer

/ E. Polyarteritis nodosa

Q 7

If this patient had refused surgical treatment, which of the following would be the most appropriate pharmacotherapy to provide definitive

treatment and thereby relieve associated pain?

/ A. Ampicillin

/ B. CIofibrate

/ C. Meperidine

/ D. Oxycodone

/ E. Ursodiol

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Abdominal pain Case 2 Answers

A1

The correct answer is D. This woman most likely has gallstones. Cholelithiasis, or the formation of calculi (gallstones) within the gallbladder, is very common in the United States, with over 500,000 cholecystectomies being performed yearly. While many cases of gallstone disease are symptomatic, right upper quadrant pain with referral of the pain to the lower right scapula should specifically suggest gallbladder disease. The pattern of episodes of several hours of pain followed by long periods of freedom from pain is also typical of symptomatic gallstone disease.

The appendix (choice A) would most likely cause lower abdominal pain.

Pain from irritation of the diaphragm (choice B) can cause right upper quadrant pain and referred pain in the supraclavicular area (rather than the subscapular pain of biliary colic). The absence of right upper quadrant tenderness to palpation, and the history of pain after a fatty meal also argue against this diagnosis.

Esophageal pain (choice C) related to regurgitation of gastric contents (heartburn) can occur postprandially, but tends to radiate into the neck, throat, or even face.

Peptic ulcer pain of gastric origin (choice E) is usually described as causing burning, gnawing, or hunger, and may be relieved by eating.

A2

The correct answer is E. Real-time ultrasonography, with 98% sensitivity and 95% specificity, is considered the method of choice for diagnosing possible gallbladder stones.

Colonoscopy (choice A) and esophagoduodenoscopy (choice C) might be helpful for excluding alternative diagnoses, but would not themselves establish a diagnosis of gallstone disease.

CT (choice B) and MRI (choice D) scans of the abdomen are expensive tests whose use is not warranted, since real-time ultrasonography performs as well or better.

A3

The correct answer is C. The space behind the stomach, hepatoduodenal ligament, and hepatogastric ligament is the omental bursa. This space can be entered by passing through the epiploic foramen of Winslow, as described in the question stem.

The common bile duct enters the duodenum through the ampulla of Vater (choice A).

The hepatoduodenal ligament contains the common bile duct (choice B), the portal vein (choice E), and the hepatic artery.

The greater peritoneal sac (choice D) lies anterior to the stomach and hepatoduodenal ligament.

A4

The correct answer is D. The cystic artery is generally a branch of the right hepatic artery.

The gastroduodenal artery (choice A) is a branch of the (common) hepatic artery.

The left gastroepiploic artery (choice B) is a branch of the splenic artery.

The right gastroepiploic artery (choice C) is a branch of the gastroduodenal artery.

The superior pancreaticoduodenal artery (choice E) is a branch of the gastroduodenal artery.

A5

The correct answer is C. The stones are gallstones, and their yellow color indicates that they are composed of cholesterol. Cholesterol stones are the most common form of gallstones. Risk factors include female sex, multiparity, obesity, increased age (female, fat, forty, and fertile) and North American Indian race.

Bilirubinate (choice A) gallstones, which are usually associated with hemolytic anemias, are less common, brown, rather than yellow, and often faceted.

Calcium phosphate (choice B), cystine (choice D), and struvite (choice E) composition can be seen in kidney stones

A6

The correct answer is C. A small gallstone obstructing the pancreatic outflow is a well-known cause of acute pancreatitis. The other conditions listed are not caused by gallstones

A7

The correct answer is E. The question is asking, "Which of the following will eradicate a gallstone?" When a gallstone is eliminated the pain will subsequently be eliminated. This question is NOT asking, "which of the following is the most appropriate form of pain control?". Ursodiol (ursodeoxycholic acid) is a hydrophilic bile acid that is used to dissolve small (<>

Analgesics and antibiotics, such as ampicillin (choice A), are administered when appropriate, but do not help eradicate the stones.

Clofibrate (choice B) is an antihyperlipidemic that is associated with the development of gallstones. High-risk patients, such as diabetics and the elderly, should be watched closely.

As a side note, if this question were asking: "which of the following is the most appropriate form of pain control in this patient", the most appropriate answer would be meperidine. Meperidine (choice C) is the narcotic of choice since it causes the least amount of spasm of the sphincter of Oddi. In other words, meperidine is preferred over oxycodone (choice D).

Abdominal Pain Case 1

A 27-year-old woman goes to an emergency room with severe abdominal pain. She had previously experienced similar episodes of pain that Iasted several hours to a few days, but this episode is the most severe. She has also been experiencing nausea, vomiting, and constipation.

The physician is left with the impression that she is agitated and somewhat confused, and an accurate history is difficult to elucidate. The patient is sent for emergency laparotomy, but no pathology is noted at surgery. Following the unrevealing surgery, an older surgeon comments that he had once seen a similar case that was actually due to porphyria.

Q 1

The porphyrias are biochemical abnormalities in which of the following pathways?

/ A. GIycogen degradation

/ B. Heme synthesis

/ C. Lipoprotein degradation

/ D. Nucleotide degradation

/ E. Urea cycle

Q 2

Following the surgery, the decision is made to screen for the porphyrias that cause acute neurovisceral symptoms. Which of the following

tests would be most likely to be used?

/ A. Erythrocyte porphyrins

/ B. Total fecal porphyrins

/ C. Total plasma porphyrins

/ D. Total urinary porphyrins

/ E. Urinary porphobilinogen

Q 3

Which of the following are the three most common forms of porphyria?

/ A. Acute intermittent porphyria, erythropoietic protoporphyria, and porphyria cutanea tarda

/ B. Acute intermittent porphyria, hepatoerythropoietic porphyria, and variegate porphyria

/ C. Congenital erythropoietic porphyria, delta-aminolevulinic acid dehydratase-deficient porphyria, and hepatoerythropoietic porphyria

/ D. Erythropoietic protoporphyria, hereditary coproporphyria, and porphyria cutanea tarda

/ E. Hereditary coproporphyria, variegate porphyria, and X-Iinked sideroblastic anemia

Q 4

This patient is found to have increased levels of both delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) in blood. Follow-up studies demonstrate low PBG deaminase in erythrocytes. AIso, additional history is elicited, revealing that the woman had started a very low carbohydrate diet about one week before being admitted to the hospitaI. Which of the following is the most likely diagnosis?

/ A. Acute intermittent porphyria

/ B. Congenital erythropoietic porphyria

/ C. Erythropoietic protoporphyria

/ D. Porphyria cutanea tarda

/ E. X-Iinked sideroblastic anemia

Q 5

Which of the following drugs would be most likely to induce an attack of abdominal pain in this patient?

/ A. Acetaminophen

/ B. Aspirin

/ C. Barbiturate

/ D. GIucocorticoid

/ E. Insulin

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Abdominal Pain Case 1 Answers:

A1

The correct answer is B. The porphyrias are a group of rare, related diseases that have in common a block in the heme synthesis pathway. The block is usually partial rather than complete, and thus many of these patients have only intermittent symptoms. Most cases of porphyria present with either a neurovisceral pattern (including both psychiatric symptoms and abdominal pain) or with photosensitive skin lesions. These two patterns are associated with different forms of porphyria.

Associate abnormalities of glycogen degradation (choice A) with the glycogen storage diseases, such as von Gierke disease, Pompe disease, and Forbes disease.

Associate abnormalities of lipoprotein degradation (choice C) with some forms of hyperlipoproteinemia (notably Type I).

Associate abnormalities of nucleotide degradation (choice D) with gout and Lesch-Nyhan syndrome.

Associate abnormalities of the urea cycle (choice E) with congenital hyperammonemia, citrullinemia, and argininosuccinic academia

A2

The correct answer is E. The acute neurovisceral porphyrias are those that tend to present with severe abdominal pain, often accompanied by neuropsychiatric symptoms. The best tests to use for screening of these diseases are urinary porphobilinogen (PBG, either random or 24 hour) and urinary delta-aminolevulinic acid (ALA, either random or 24 hour).

Erythrocyte porphyrins (choice A) are used for follow-up in the photosensitive types of porphyria.

Total fecal porphyrins (choice B) are used for follow-up evaluation after screening tests for either the photosensitive porphyrias or the acute neurovisceral porphyrias are positive.

Total plasma porphyrias (choice C) are useful for first line screening of the photosensitive porphyrias, and are used for further evaluation after screening in the acute neurovisceral porphyrias.

Total urinary porphyrins (choice D) are used for further evaluation after screening for acute neurovisceral porphyries

A3

The correct answer is A. The porphyrias are complex diseases that can easily appear overwhelming. A very useful point to know (both clinically and for the USMLE) is that the three most common forms are acute intermittent porphyria, erythropoietic protoporphyria, and porphyria cutanea tarda. Acute intermittent porphyria tends to present with acute neurovisceral symptoms. Erythrocytic protoporphyria tends to present acutely with painful skin lesions. Porphyria cutanea tarda tends to present with chronic blistering skin lesions. The other types listed in various choices are also porphyrias, but are less common.

A4

The correct answer is A. These laboratory findings are most consistent with acute intermittent porphyria, which is due to PBG deaminase deficiency. Patients usually, but not always, have a deficiency of erythrocyte PBG deaminases. (Some cases have also been described in which the enzyme deficiency is limited to liver.) The condition is an autosomal dominant disorder that typically becomes symptomatic in women after puberty, and then often only if a precipitating event (dieting, use of certain drugs, premenstrual) is also present. Symptoms during the attacks can include abdominal symptoms (pain, nausea, vomiting, constipation, diarrhea, abdominal distension, ileus), which are thought to be due to the effects of this condition on visceral nerves. Other symptoms that may be mediated neurologically include incontinence, urinary retention, tachycardia, diaphoresis, hypertension, muscle weakness, psychiatric symptoms, seizures, and rarely, severe paralysis, respiratory insufficiency, and death. Both intravenous glucose (oral is often inadequate due to poor intestinal function) and exogenous heme supplementation can suppress the heme biosynthetic mechanism, and tend to ameliorate the acute attack. Patients should be cautioned to diet gently, as intense dieting can precipitate attacks.

Congenital erythropoietic porphyria (choice B) is characterized by severe skin blistering that usually begins after birth, pink to dark-brown urine, normal ALA and PBG, and increased porphyrins (primarily uroporphyrin I and coproporphyrin I) in urine, plasma, and erythrocytes.

Erythropoietic protoporphyria (choice C) is characterized by cutaneous photosensitivity that begins early in life and high protoporphyrin in erythrocytes and bone marrow.

Porphyria cutanea tarda (choice D) is characterized by photosensitivity with skin blistering, elevated plasma porphyrins, and elevated urine porphyrins (mostly uroporphyrin and heptacarboxylporphyrin).

The very rare X-linked sideroblastic anemia (choice E), due to a deficiency of delta-aminolevulinic acid synthase, can clinically resemble acute intermittent porphyria, and is characterized by elevated levels of urinary ALA and coproporphyrin.

A5

The correct answer is C. Some symptomatic episodes of acute porphyria (including acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and aminolevulinic acid dehydratase porphyria) are triggered by drug ingestion, and administration of drugs to undiagnosed patients can cause an acute exacerbation of an ongoing attack of acute porphyria. Drugs considered unsafe for use in these patients notably include alcohol, anticonvulsants, barbiturates, many other sedatives, and sulfonamide antibiotics. Of particular concern are the sedative agents, since it may be very tempting to give an obviously agitated patient a sedative to allow easier examination of the patient. Many other drugs are also on the lists of potentially dangerous drugs in these patients. Once the diagnosis is established, the patient should be instructed to always inform her/his physician of her condition, and ask that the safety of drugs prescribed in patients with porphyria be checked. Many of the drugs that can induce or exacerbate an attack of porphyria do so by increasing the activity of the cytochrome P450 system, which indirectly triggers an increase in heme biosynthesis. The other medications listed in the choices are "safe" in these patients.