🇨🇦 MCCQE1,2 | #Case_218 | #answer
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✅ D

🔎 Explanation

The differential diagnosis of urinary retention in the elderly is broad. While most causes are benign and readily treated, the physician must be vigilant in looking for conditions that require urgent intervention. This patient presents with many possible causes of urinary retention, with the most common being benign prostatic hyperplasia. Acute prostatitis, especially in a male with an enlarged prostate, is another relatively common reason for obstructive symptoms. This patient’s physical examination and abnormal urinalysis support this diagnosis, but his normal vital signs and lack of fever suggest he can be treated with an oral fluroquinolone and does not require hospital admission for intravenous therapy. Medications such as oral decongestants can contribute to urinary retention in men with enlarged prostate glands, and should be used with caution and discontinued if obstructive symptoms occur. Obstipation (severe constipation caused by intestinal obstruction) with stool impaction is another relatively common reason for urinary retention in the elderly and can be treated with manual disimpaction and enemas. In this patient, the presence of increasing low back pain and leg weakness, and the findings of anal sphincter laxity and numbness in the perianal area on examination, suggest the presence of a serious neurologic etiology such as cauda equina syndrome. Urgent diagnosis and treatment are necessary to reduce morbidity, and MRI should be performed immediately. The presence of a mildly elevated post-void residual is not an indication for urgent decompression with a Foley catheter

🇨🇦 MCCQE1,2 | #Case_219
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A 55-year-old male with coronary artery disease undergoes coronary artery bypass grafting (CABG). The operation is uneventful, but 2 hours after the surgery he suddenly spikes a fever to 40.0˚C (104.0˚F). The patient’s pulse rate is 110 beats/min and his blood pressure is 140/85 mm Hg. He remains on the ventilator and does not awaken during the episode. The physical examination is otherwise unremarkable except for his surgical incisions. He has no history of recent infection prior to the surgery and his WBC count is not elevated. Apart from hypertension and coronary artery disease, his past medical and surgical histories are negative. The most likely explanation for this patient’s fever is:

a) Transient bacteremia
b) Aspiration pneumonia
c) Urosepsis
d) Malignant hyperthermia
e) Post-pericardiotomy syndrome

🇨🇦 MCCQE1,2 | #Case_219 | #answer
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✅ D

🔎 Explanation

Malignant hyperthermia is an inherited myopathy in which abnormalities of skeletal-muscle sarcoplasmic reticulum cause an increase in intracellular calcium levels, resulting in sustained muscular contraction and a hypermetabolic state. This condition is most often triggered by inhalational anesthetics (e.g., halothane) or by succinylcholine, used for muscle paralysis. It results in a sudden rise in temperature, tachycardia, increased muscle tone, and eventual muscle rigidity. If unrecognized and untreated, there is a downward spiral with rhabdomyolysis, acidosis, renal failure, cardiovascular instability, and death. It usually presents in the operating room or the recovery room, and prompt recognition and treatment with dantrolene, along with cooling the patient, reduces morbidity and mortality risks. While urosepsis, pneumonia, and bacteremia are possible complications of the surgery, none of these is the most likely cause of fever in this scenario. Post-pericardiotomy syndrome (Dressler’s syndrome) occurs at least 2 weeks postoperatively and is manifested by low-grade fever and chest pain.

🇨🇦 MCCQE1,2 | #Case_220
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A 27-year-old female who recently delivered a baby girl at your department through Ceasarian section suddenly seems confused. She also presents with excessive sweating, and hand twitching. Her past medical history is significant for asthma managed with albuterol as needed. She is allergic to latex. She takes no other medications but regularly uses 2 supplements: St John’s Wort and 5-HTP. Prior to the C-section she received an epidural anesthesia with bupivacaine. Her post-surgery pain was managed with meperidine. On physical examination her vital signs are T: 39.1°C, BP: 140/90 mmHg; HR: 110/min; respirations 17/min. Knee and ankle reflexes are overactive. Clonus is noted. Which of the following is the best explanation for her current condition?

a) She has neuroleptic malignant syndrome
b) It is caused by the pre-C-section anesthesia and genetic predisposition
c) It is caused by cytokine release after child birth via C-section
d) Interaction between meperidine and supplements occured
e) She suffers from anxiety and panic attack because of her surgery

🇨🇦 MCCQE1,2 | #Case_220 | #answer
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✅ D

🔎 Explanation

This patient underwent C-section and post-surgical pain management consisted of meperidine (Demerol). Given her history of regular use of supplements such as 5-hydroxytryptophan (also known as 5-HTP) and St John’s Wort and the current symptoms she has of elevated temperature, tachycardia, altered mental status, and hyperreflexia, she most likely has serotonin syndrome (serotonin toxicity). This is a life-threatening drug reaction that may occur because of an overdose of SSRI or because of interactions between drugs, tricyclic antidepressants and monoamine oxidase inhibitors for example. Other drugs that have been associated with serotonin syndrome are:

✔Drugs that have direct 5-HT stimulation: Buspirone, Carbamazepine, and Triptans

✔Drugs that have direct 5-HT release from stored vesicles: MAOIs, Cocaine, Levodopa, Codeine, Dextromethorphan.

✔Decreased 5-HT reuptake: SSRI, trazodone, TCA, meperidine, amphetamine, and hypericum species such as St John’s wort

✔Decreased 5-HT degradation: MAOIs and St John’s wort

Therefore the best explanation for her current symptoms is interaction between meperidine and her supplements (choice D).

⚠ She has neuroleptic malignant syndrome (choice A) is incorrect. This patient has not been on antipsychotic medications.

⚠ Pre C-section anesthesia and genetic predisposition (choice B) is incorrect. Anesthesia that causes malignant hyperthermia in patients with genetic predisposition is usually succinylcholine when given to patients with ryanodine receptor mutations.

⚠ Cytokine release after child birth via C-section (choice C) might cause fever but it would not explain altered mental status and clonus.

⚠ Anxiety and panic attack because of surgery (choice E) is unlikely to cause the cardiovascular and CNS symptoms observed in this patient.

🔖 Key point:

Serotonin syndrome is defined based on Sternbach criteria or the Hunter criteria and this may be summarized as being
characterized by hyperthermia, tachycardia, hyperreflexia, and altered mental status. It is caused by drug interactions, especially drugs that may cause increased serotonin levels

🇨🇦 MCCQE1,2 | #Case_221
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A 68-year-old woman presents to your department with worsening dyspnea. Past medical history includes COPD, coronary artery disease, and Stage III chronic kidney disease. Her brain natriuretic peptide is 1200 pg/mL (normal < 100 pg/mL). Which of the following medications would be part of effective management of this condition?

a) Inhaled ipratropium bromide
b) Peritoneal dialysis
c) Mannitol
d) Nesiritide
e) Diltiazem

🇨🇦 MCCQE1,2 | #Case_221 | #answer
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✅ D

🔎 Explanation

This patient presents with dyspnea and has elevated brain natriuretic peptide (BNP). The BNP is secreted by the brain and heart ventricles and is elevated in traumatic brain injury, left ventricular dysfunction, and congestive heart failure (CHF). In the patient with dyspnea, overlapping or even conflicting historical, physical, and radiographic findings often hinder the differentiation between cardiac and noncardiac etiology. Initial misdiagnosis occurs in approximately 15-20% of patients presenting to the emergency department with dyspnea secondary to an acute exacerbation of CHF. This misdiagnosis may incur clinically significant morbidity and mortality. The primary value of BNP testing in the ED is its diagnostic value in the differential diagnosis of acute dyspnea and possible CHF. BNP levels > 400 pg/mL are suggestive of CHF. Since this patient has no history of traumatic brain injury and is presenting with elevated BNP, the most likely cause is decompensated CHF. Nesiritide (choice D) is a recombinant form of human BNP used to treat dyspnea due to CHF and would be part of a comprehensive management plan in the treatment of this patient. Although plasma BNP levels are increased in patients with HF, such patients are sodium avid and have increased systemic vascular resistance. Moreover, available tests for BNP may be not specific enough to differentiate measurements of active and inactive forms of BNP. Bioactive BNP forms may be low in patients with CHF. Nesiritide produces dose-dependent balanced arteriolar and venous dilation (at 13,000 pg/mL levels) and has been shown to result in rapid reduction in ventricular filling pressures and reversal of heart failure symptoms such as dyspnea. BNP measurements are not indicated in patients receiving nesiritide treatment. If BNP is used as a diagnostic marker to rule in CHF, the level must be determined before nesiritide therapy is started.

⚠ Inhaled ipratropium bromide (choice A) would be used in an acute exacerbation of COPD. The elevated BNP helps us determine the cause of dyspnea in this patient, it is cardiogenic in nature and CHF is the most likely diagnosis.

⚠ Peritoneal dialysis (choice B) would be done if the patient had end-stage renal disease or acute renal failure. No findings suggest this diagnosis in this patient.

⚠ Mannitol (choice C) is incorrect. Circulatory overload due to expansion of extracellular fluid is a serious adverse effect of mannitol. As a consequence, pulmonary edema can be precipitated in a patient with diminished cardiac reserve.

⚠ Diltiazem (choice E) is a calcium channel blocker and is contraindicated in patients with CHF and abnormal LV
ejection fraction. While measurements of LV ejection fraction of this patient are not mentioned, studies have shown that there’s a negative linear correlation between BNP and LV ejection fraction, and high BNP levels can predict decreased LV ejection fraction levels. Use of diltiazem has been shown to have negative outcomes in CHF.

🔖Key point:

BNP can be used to differentiate cardiogenic dyspnea from non-cardiogenic dyspnea. BNP levels > 400 pg/mL are suggestive of CHF. Paradoxically, nesiritide, a recombinant BNP, is used to treat dyspnea in CHF

🇨🇦 MCCQE1,2 | #Case_222
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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 findings?

(A) Cholelithiasis
(B) Pancreatic carcinoma
(C) Primary biliary cirrhosis
(D) Primary hemochromatosis
(E) Primary sclerosing cholangitis

🇨🇦 MCCQE1,2 | #Case_222 | #answer
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✅ E

🔎 Explanation

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 inflammation, obliterative fibrosis, 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.”

⚠Answer A is incorrect. Cholelithiasis, also known as gallstones, is not associated with ulcerative colitis. Endoscopic retrograde cholangiopancreatography may be used to visualize a ductal stone but is not a modality of choice for gallstone detection.

⚠Answer B is incorrect. Pancreatic carcinoma is not associated with ulcerative colitis. On endoscopic retrograde cholangiopancreatography, it is characterized by a double-duct sign that results from tumor obstruction of both the common bile duct and the main pancreatic duct, not beading.

⚠Answer C is incorrect. Primary biliary cirrhosis is a nonsuppurative, granulomatous destruction of medium-sized intrahepatic bile ducts. It is not associated with ulcerative colitis. Endoscopic retrograde cholangiopancreatography findings in this condition are nonspecific.

⚠Answer D is incorrect. Primary hemochromatosis is a familial defect in control of iron absorption with massive accumulation of hemosiderin in hepatic and pancreatic parenchymal cells. This condition is not associated with ulcerative colitis and has no specific endoscopic retrograde cholangiopancreatography findings

🇨🇦 MCCQE1,2 | #Case_223
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A 31-year-old man comes to the physician for a follow-up examination. He has tingling and numbness of his legs for the past 10 days. He has also felt more tired than normal. Three months ago, he was diagnosed with pulmonary tuberculosis and started on antituberculosis therapy. He appears pale. Vital signs are within normal limits. Examination shows dry scaly lips and cracks at the corner of the mouth. Neurological examination shows normal muscle strength. Sensation to pinprick and light touch is decreased over the lower extremities. Deep tendon reflexes are 2+ bilaterally. His hemoglobin concentration is 10.4 g/dL and mean corpuscular volume is 76 μm3. Administration of which of the following is most likely to have prevented this patient's current symptoms?

a) Iron
b) Pyridoxine
c) Folic acid
d) Vit B12
e) IVIG

🇨🇦 MCCQE1,2 | #Case_223 | #answer
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✅ B

🇨🇦 MCCQE1,2 | #Case_224
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A 48-year-old woman comes to the emergency room with chest pain. She describes the pain as a squeezing sensation in her chest with radiation to the left shoulder. The episode began about 15 minutes ago when she was sitting reading a book. She has had this pain before, typically in the evenings, though prior episodes usually resolved after a couple of minutes. Her pulse is 112/min, blood pressure is 121/87 mmHg,and respiratory rate is 21/min. An ECG shows ST-segment elevations in the inferior leads. Serum troponins are negative on two successive blood draws and the ECG shows no abnormalities 30 minutes later. Which of the following is the best long-term treatment for this patient's symptoms?

A) Clopidogrel
B) Diltiazem
C) Aspirin
D) Enalapril
E) Metoprolol

🇨🇦 MCCQE1,2 | #Case_224 | #answer
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✅ B

🔎 Explanation

Calcium channel blockers such as diltiazem are the first-line treatment for vasospastic angina. They are effective for both acute attacks and prophylaxis. In addition to CCBs, lifestyle modifications should be attempted, such as smoking cessation and abstaining from stimulants.

🇨🇦 MCCQE1,2 | #Case_225
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A 4-year-old female patient is brought to you by her parents on account of having knee pain over the past few days. The mother says she noticed the girl started limping 2 days ago, referring pain in her left knee and also had fever, which was not controlled by paracetamol. She refers that the girl has been irritable, has not been eating well, and she is not as happy as she usually is. She reports no relevant medical history. On examination, she has a temperature of 38.7°C, a heart rate of 123 bpm, and a respiratory rate of 23 /minute. You notice a markedly swollen, red, tender, painful and warm left knee, which has very limited and painful mobility and no other remarkable signs. Which of the following diagnostic tests is the best for excluding septic arthritis as a diagnosis?

a) Blood culture
b) ESR and CRP
c) Gram stain of synovial fluid
d) WBC count of the synovial fluid
e) X-ray

🇨🇦 MCCQE1,2 | #Case_225 | #answer
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✅ B

🔎 Explanation

ESR and CRP (choice B) together have a negative predictive value of almost 90 percent. Of these, the one with the greatest negative predictive value by it self is CRP. This means that negative results in CRP (usually less than 1mg/dL) and ESR (less than 20 mm/hr) mean that the patient is very unlikely to have septic arthritis. Also, CRP is better for monitoring response to treatment of septic arthritis than other methods.

⚠ The blood culture (choice A) of a patient with septic arthritis only turns out to be positive in 40-50 percent of the cases, giving it a very poor negative predictive value.

⚠ Gram stain of synovial fluid (choice C) is not reliable for the diagnosis or exclusion of septic arthritis. 50 percent of synovial fluid aspirations are sterile in cases of septic arthritis confirmed with clinical and laboratory findings, including positive blood culture.

⚠ Generally speaking, synovial fluid WBC counts (choice D) of more than 50 000 cells/microL with a predominance of polymorphonuclear leukocytes indicates a greater likelihood of the patient having septic arthritis. However, the synovial fluid WBC count is neither sensitive nor specific for the diagnosis of septic arthritis. It may happen to be much lower in unusual causes of bacterial arthritis (eg. Brucella), and it may exceed 50 000 cells/microL in patients with juvenile idiopathic arthritis, serum sickness, or reactive arthritis.

⚠ Normal X-ray (choice E) does not exclude the diagnosis of Septic Arthritis, therefore it has a poor negative predictive value. It does not add much to the diagnostic evaluation of Septic Arthritis. However, it may be a valuable adjunct to the examination of the hip, mainly to compare the contralateral joint.

🔖 Key point:

ESR and CRP together have a negative predictive value of almost 90 percent. This means that negative results in CRP and ESR mean that the patient is very unlikely to have septic arthritis

🇨🇦 MCCQE1,2 | #Case_226
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A 13-year-old white female reports a 6 month history of intermittent abdominal cramping, with each episode becoming progressively worse. Based on her history, there is no obvious relationship to eating, voiding, or defecating. She report that she has not yet begun menstruating and is not sexually active. Her weight has been stable. She appears to be in mild emotional distress about being the “last girl in her class to have a period”. She is in no physical discomfort and her vital signs are normal. Secondary sexual characteristics appear to be developing normally. She is in the 57th percentile for height and the 65th percentile for weight. A complete physical examination confirms your presumptive diagnosis. The therapeutic procedure of choice would be:

a) Appendectomy
b) Colonoscopy
c) Hymenotomy
d) Cystoscopy
e) Paracentesis

🇨🇦 MCCQE1,2 | #Case_226 | #answer
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✅ C

🔎 Explanation

The key to making a diagnosis of imperforate hymen, aside from the obvious finding on physical examination, lies in the systematic drawing of inferences. One can speculate that this patient’s recurrent crescendo abdominal cramping represents six menstrual sheddings, with no egress from the body. Her delay in menarche, despite normal growth parameters, offers another clue that the structural amenorrhea is present. Amounts of retained blood vary among patients; up to 3000 mL have been reported. A large volume can accumulate without causing any permanent damage, and subsequent fertility is usually normal. Hymenotomy will relieve the pressure, and normal menses should ensue

🇨🇦 MCCQE1,2 | #Case_227
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A 57-year-old black female has a partial resection of the colon for cancer. The surgical specimen has clean margins, and there is no lymph node involvement. There is no evidence of metastasis. You recommend periodic colonoscopy for surveillance, and also plan to monitor which one of the following tumor markers for recurrence?

a) Prostate-specific antigen (PSA)
b) Cancer antigen 27-29 (CA 27-29)
c) Cancer antigen 125 (CA-125)
d) Carcinoembryonic antigen (CEA)
e) Alpha-fetoprotein

🇨🇦 MCCQE1,2 | #Case_227 | #answer
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✅ D

🔎 Explanation

Carcinoembryonic antigen (CEA) (choice D) is a marker for colon, esophageal, and hepatic cancers. It is expressed in normal mucosal cells and is overexpressed in adenocarcinoma, especially colon cancer. Though not specific for colon cancer, levels above 10 ng/mL are rarely due to benign disease. CEA levels typically return to normal within 4-6 weeks
after successful surgical resection.

⚠ Prostrate-specific antigen (PSA) (choice A) is a marker that is used to screen for prostate cancer. It is elevated in more than 70% of organ-confined prostrate cancers.

⚠ Cancer antigen 27-29 (CA 27-29) (choice B) is a tumor marker for breast cancer. It is elevated in about 33% of
early-stage cancers and about 67% of late-stage breast cancers

⚠ CA-125 (choice C) is a marker for ovarian cancer. Although it is elevated in 85% of ovarian cancers, it is elevated in only 50% of early-stage ovarian cancers.

⚠ Alpha-fetoprotein (choice E) is a marker for hepatocellular carcinoma and nonseminomatous germ cell tumor, and is elevated in 80% of hepatocellular carcinomas

🇨🇦 MCCQE1,2 | #Case_228
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A 55-year-old white female presents with redness at the scar from a lumpectomy performed for stage I cancer of her right breast 4 months ago. The patient has completed radiation treatments to the breast. She is afebrile and there is no axillary adenopathy. There is no wound drainage, crepitance, or bullous lesions. Which of the following organisms would be the most likely cause of cellulitis in this patient?

a) Non-group A Streptococcus
b) Pneumococcus
c) Clostridium perfringens
d) Escherichia coli
e) Pasteurella multocida

🇨🇦 MCCQE1,2 | #Case_228 | #answer
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✅ A

🔎 Explanation

Cellulitis in patients after breast lumpectomy is thought to be related to lymphedema. Axillary dissection and radiation predispose to these infections. Non-group A hemolytic Streptococcus is the most common organism associated with this infection. The onset is often several weeks to several months after surgery. Pneumococcus is more frequently a cause of periorbital cellulitis. It is also seen in patients who have bacteremia with immunocompromised status. Immunocompromising conditions would include diabetes mellitus, alcoholism, lupus, nephritic syndrome, and some hematologic cancers.
Clostridium and Escherichia coli are most frequently associated with crepitant cellulitis and tissue necrosis. Pasteurella multocida cellulitis is most frequently associated with animal bites, especially cat bites.