🇨🇦 MCCQE1,2 | #Case_131
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A 57-year-old man underwent pneumonectomy to remove an epithelioma. Complete blood count, renal and liver functions tests were normal. He was prescribed 100units/kg of low molecular weight heparin (LMWH) as prophylaxis against venous thrombosis. His calculated daily dose of 6000 units was given subcutaneously, twice daily. Which one of the following is recommended for monitoring of the anticoagulant effects of LMWH?

a) Measurement of international normalized ratio (INR)
b) Measurement of activated partial thromboplastin time (aPPT)
c) Measurement of plasma antifactor Xa levels
d) Measurement of serum levels of LMWH
e) No monitoring is required

🇨🇦 MCCQE1,2 | #Case_131 | #answer
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✅ E

🔎 Explanation

No monitoring is required (choice E) for the anticoagulant effect of LMWH. The anticoagulant response to LMWH is predictable and monitoring is thus not necessary in most patients. Monitoring is indicated only in obese patients and those with renal impairment. This patient's renal function was normal and he was not obese (his body weight is 60 kg as inferred from the calculated daily dose of LMWH).

⚠ Education point measurement of INR (choice A) is not the correct choice. Even if monitoring were indicated, INR would not be suitable for monitoring the anticoagulant effect of LMWH. LMWHs act by catalyzing inhibition of factor Xa and measurement of INR is not markedly affected by this inhibition.

⚠ Measurement aPPT (choice B) is not the correct choice. Even if monitoring were indicated, aPPT would not be the best way to monitor the anticoagulant effect of LMWHs because these anticoagulants have little effects on aPPT. aPPT is the method of choice for monitoring the effects of unfractionated heparin (UFH) rather than LMWHs. UFH inhibits both Xa and thrombin and can thus, affect aPPT. LMWHs on the other hand inhibit factor Xa only and their effect on aPPT is minimal.

⚠ Measurement of plasma antifactor Xa levels (choice C) is not the correct choice even though this would be the method of choice for monitoring the anticoagulant effect of LMWHs if this were indicated.

⚠ Measurement of serum levels of LMWH (choice D) is not the correct choice. Because the major side effect of LMWHs is bleeding and because of predictability of the anticoagulant response to LMWHs, measurement of serum levels of these anticoagulant is not required. Also, because LMWHs are eliminated almost exclusively through the kidney, measurement of serum levels is not required in patients with normal renal function like our patient.

🔖Key point:

In patients with normal renal function and those who are not obese, monitoring the anticoagulant effect of LMWHs is not required

🇨🇦 MCCQE1,2 | #Case_132
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The parents of a 40-day-old infant bring her to your clinic because she has had a persistent fever for the past 2 days with rectal temperatures between 38.1°C (100.5°F) and 38.9°C (102.0°F). She has been fussy and wants to be held, but has been nursing well. She is crying when you enter the room, and on examination she has good skin turgor and capillary refill. The examination does not reveal any obvious source of infection. By the time you complete the examination the infant is resting quietly in her father’s arms. You obtain a CBC and urinalysis. The WBC count is 12,500/mm³ (N 5000-19,500) with an absolute neutrophil count of 8500/mm³ (N 1000-9000). The urinalysis is within normal limits. Which one of the following would be most appropriate at this time?

a) Home care and parental observation only, as long as the temperature remains under 39.0°C
b) Home care and reevaluation in 24 hours
c) Oral antibiotics and reevaluation in 24 hours
d) A complete sepsis workup, including blood cultures, stool studies, a chest radiograph, and cerebrospinal fluid studies
e) Hospital admission and adequate antibiotic treatment and fluid resuscitation

🇨🇦 MCCQE1,2 | #Case_132 | #answer
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✅ B

🔎 Explanation

Most children will be evaluated for a febrile illness before 36 months of age, with the majority having a self-limited viral illness. For the management of febrile infants, the most commonly used criteria in practice are the Rochester criteria. Clinical assessment involves deciding whether a child appears toxic. The clinical features that define toxicity include irritability, lethargy, and decreased social interaction. Nontoxic-appearing febrile infants 29-90 days of age who have a negative screening laboratory workup, including a CBC with differential and a normal urinalysis, can be sent home and followed up in 24 hours(choice B). Occasionally it may be important to obtain blood cultures and stool studies, or a chest film if indicated by the history or examination, and spinal fluid studies if empiric antibiotics are to be given. This infant’s clinical status did not indicate that any of these additional studies should be performed and empiric antibiotic treatment is not planned. For example, if a child has diarrhea, stool studies are usually done.

⚠ Home care and parental observation only, as long as the temperature remains under 39.0°C (choice A) is incorrect. Observation with no follow-up is an appropriate strategy in nontoxic children, but only if the child is 3-36 months of age and the temperature is under 39°C. Nontoxic children 3-36 months of age should be reevaluated in 24-48 hours if the temperature is over 39°C. Although a positive response to antipyretics has been considered an indication of a lower risk of serious bacterial infection, there is no correlation between fever reduction and the likelihood of such an infection.

⚠ Oral antibiotics and reevaluation in 24 hours (choice C) is incorrect. This child is considered low risk, therefore, lumbar puncture or empiric antibiotic therapy are not recommended. For children whose condition warrants antibiotherapy and re-evaluation in 24 hours, lumbar puncture should be done before antibiotics to avoid affecting sensitivity studies.

⚠ A complete sepsis workup, including blood cultures, stool studies, a chest radiograph, and cerebrospinal fluid studies (choice D) should be done for any infant younger than 29 days, and any infant or child with a toxic appearance regardless of age. They should undergo a complete sepsis workup and be admitted for observation until culture results are obtained or the source of the fever is found and treated.

⚠ Hospital admission and adequate antibiotic treatment and fluid resuscitation (choice E) are not recommended in this non-toxic child with initial studies showing no abnormality.

🇨🇦 MCCQE1,2 | #Case_133
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A 26-year-old female presents with lower abdominal pain and vaginal bleeding. Her last menstrual period was 7 weeks ago. A urine pregnancy test is positive, and a quantitative beta-hCG level is 2500 mIU/mL. Intravaginal ultrasonography shows no evidence of an intrauterine gestational sac. Baseline laboratory tests, including a CBC, liver function tests, and renal function tests, are all normal. She is treated with a single dose of intramuscular methotrexate at 50 mg/m² of body surface. Day 4 lab results show quantitative beta-hCG level of 2800 mIU/mL on day 4. Seven days later, the patient presents for reevaluation, and her quantitative beta-hCG is found to be 2640 mIU/mL. Which one of the following is the most appropriate next step?

a) A repeat dose of methotrexate, 50 mg/m² of body surface
b) Methotrexate, 1 mg/kg every other day, plus leucovorin, 0.1 mg/kg on alternate days
c) Repeat transvaginal ultrasonography to evaluate for a viable intrauterine pregnancy
d) Laparoscopy with salpingostomy
e) Expectant management

🇨🇦 MCCQE1,2 | #Case_133 | #answer
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✅ A

🔎 Explanation

Management of ectopic pregnancy with methotrexate is appropriate in patients who have a beta-hCG level < 5,000
mIU/mL; who are without liver or renal disease, immune or platelet compromise, or significant pulmonary disease; and who are reliable and able to follow up daily if necessary. If the beta-HCG level has not dropped at least 15% from the day-4 level, administer a second IM dose of methotrexate (50 mg/m2) on day 7, and observe the patient. If no drop has occurred by day 14, surgical therapy is indicated. Laparoscopy with salpingostomy is the preferred method. Expectant management is appropriate only if a patient has a beta-hCG level < 1000 mIU/mL that is declining.

🇨🇦 MCCQE1,2 | #Case_134
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A 25-year-old male is brought to the emergency department after he was thrown off his motorcycle following a collision with an automobile. He was stabilized by paramedics, who brought him to the ED. While he denies any loss of consciousness, he describes a sensation of wanting to urinate but being physically unable to.On physical examination, his abdomen is diffusely tender to palpation. There is blood at the meatus of the penis. After fluid resuscitation, a radiograph of the pelvis is taken and demonstrates a fracture of the pubic symphysis. What is the most appropriate next step in the investigation of this patient’s genitourinary tract’s injury?

a) Ultrasonography
b) Retrograde urethrography
c) Abdominal and pelvic CT scan
d) Urethral catheterization
e) Voiding cystourethrography

🇨🇦 MCCQE1,2 | #Case_134 | #answer
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✅ B

🔎 Explanation

This patient’s history of traumatic injury to the pelvis, his inability to urinate, and the findings of blood at the urethral meatus are suggestive of urethral injury. In males, the urethra is divided into the anterior and posterior sections by the urogenital diaphragm. Most pelvic fractures resulting from road traffic accidents are associated with injuries to the posterior urethra. Similar to any other trauma case, initial management should start with stabilizing the patient by giving fluid resuscitation to those with blood loss and hypotension. Presence of blood at meatus precludes any attempt at urethral instrumentation, until the entire urethra is adequately imaged. Retrograde urethrography (choice B) is considered the gold standard imaging for evaluating urethral injury and is the best next step in the management of this patient.

⚠ Ultrasonography (choice A) is not a routine investigation in the initial assessment of urethral injuries but can be very useful in determining the position of the pelvic hematomas and the high-riding bladder when a suprapubic catheter is indicated.

⚠ Abdominal and pelvic CT scan (choice C) is useful in defining the distorted pelvic anatomy after severe injury and assessing associated injuries of penile crura, bladder, kidney, and intraabdominal organs. However, it is not part of initial assessment of urethral injury and would not be the best next step in the evaluation of this patient.

⚠ Urethral catheterization (choice D) is contraindicated in pelvic injuries with blood at the urethral meatus as it could convert a partial tear into a complete one. Retrograde urethrography should be done first.

⚠ Voiding cystourethrography (choice E) is done after about 4 weeks when a delayed repair is being considered. This allows urethral healing and is preceded by suprapubic cystostomy as it is performed through the suprapubic catheter. Therefore, voiding cystourethrography would not be the next step in the management of this patient as the suprapubic catheter would have to be in place few weeks earlier first.

🔖Key point:

Traumatic injury to the pelvis, inability to urinate, and blood at the penis meatus are suggestive of urethral injury. Retrograde urethrography is considered the gold standard imaging for evaluating urethral injury.

🇨🇦 MCCQE1,2 | #Case_135
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A 21-year-old bisexual man has a 4 week history of intermittent diarrhea, urethral discharge, and pain in the right knee and left second toe. He has several oral ulcers, iritis, a scaly papular rash on palms and soles, onycholysis, swelling of the left second toe, heat and swelling of the right knee and a clear urethral discharge. The results of Gram-stain and culture of urethral discharge are negative. Rheumatoid factor is not present. The most likely diagnosis is:

a) Reiter’s syndrome
b) Gonococcal arthritis
c) Behcet disease
d) Psoriatic arthritis
e) Acquired immune deficiency syndrome

🇨🇦 MCCQE1,2 | #Case_135 | #answer
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✅ A

🔎 Explanation

Reiter's syndrome (reactive arthritis) is inflammation of the joints and tendon attachments at the joints, often accompanied by inflammation of the eye's conjunctiva or iris and the mucous membranes, such as those of the mouth and genitourinary tract, and by a distinctive rash. Reiter's syndrome is also called reactive arthritis because the joint inflammation appears to be a reaction to an infection originating in the intestine or genital tract. This syndrome is most common in men aged 20 to 40. Typically, symptoms begin 7 to 14 days after the infection. Inflammation of the urethra result either directly from infection of the urethra or even from a reaction to the intestinal infection. In men, inflammation of the urethra causes moderate pain and a discharge from the penis or a rash on the glans of the penis (balanitis circinata). The prostate gland may be inflamed and painful. The genital and urinary symptoms in women, if any occur, are usually mild, consisting of a slight vaginal discharge or uncomfortable urination. The conjunctiva become red and inflamed, causing itching or burning and excessive tearing. Joint pain and inflammation may be mild or severe. Several joints are usually affected at once, especially the knees, toe joints, and areas where tendons are attached to bones, such as at the heels. Small, painless or tender sores can develop in the mouth.

Note: The classic triad of symptoms (conjunctivitis, urethritis, and arthritis), found in only one third of patients with reactive arthritis, has a sensitivity of 50.6% and a specificity of 98.9%

🇨🇦 MCCQE1,2 | #Case_136
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A 20-year-old man was found to have an isolated elevation of serum bilirubin of 50µmol/L when baseline liver function tests were ordered prior to prescribing phenytoin for treatment of epilepsy. More than 97% of bilirubin was of the unconjugated type. Complete blood count was normal. Apart from daily consumption of one to two drinks of alcohol for the last three years, and the recently diagnosed epilepsy, his medical history was otherwise unremarkable. Physical examination was normal. Which of the following disorders is most likely to be the cause of jaundice in this patient?

a) Hereditary spherocytosis
b) Autoimmune hemolytic anemia
c) Gilbert’s syndrome
d) Alcoholic hepatitis
e) Glucose 6-phosphate dehydrogenase deficiency (G6PD)

🇨🇦 MCCQE1,2 | #Case_136 | #answer
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✅ C

🔎 Explanation

Gilbert’s syndrome (choice C), which is more common in males in their early adult life, is usually discovered incidentally when liver function tests are done for purposes other than suspected liver disease. Typically, hyperbilirubinemia is mild (< 51µmol/L) and more than 95% of bilirubin is of the unconjugated type in Gilbert’s syndrome. Hyperbilirubinemia in patients with Gilbert’s syndrome is due to deficiency of uridine diphosphate-glucouronosyl transferase that is responsible for conjugation of bilirubin in the liver. Other than the raised serum bilirubin, liver function tests and complete blood count are usually normal in this syndrome. Our patient had most of these features and Gilbert’s syndrome is thus, the most likely diagnosis. The high prevalence of Gilbert’s syndrome (about 8%) also puts this syndrome on the top of the list of causes of isolated hyperbilirubinemia.

⚠ Hereditary spherocytosis (choice A), autoimmune hemolytic anemia (choice B) and G6PD (choice E) are incorrect choices. In these disorders, unconjugated hyperbilirubinemia is caused by hemolysis (hemolytic jaundice) and complete blood count would show high reticulocyte count and low hemoglobin concentration. In our patient CBC was normal.

⚠ Alcoholic hepatitis (choice D) is not the correct choice. Although hyperbilirubinemia is usually mild in alcoholic hepatitis, levels of serum transaminases are moderately elevated. In our patient serum level of these enzymes are normal and alcoholic hepatitis is an unlikely cause of his hyperbilirubinemia. The fact that our patient drinks alcohol is not enough to establish a causal relation between alcohol consumption and liver disease. In addition, for alcohol consumption to cause liver disease, consumption of more than three drinks per day for ten years is usually required.

🔖Key point:

The cause of isolated hyperbilirubinemia in an apparently healthy young man is Gilbert’s syndrome until proven otherwise.

🇨🇦 MCCQE1,2 | #Case_137
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A 56-year-old female presents for a routine visit. An otherwise normal physical examination reveals a 2-cm right-sided thyroid nodule. Her TSH levels are normal. She has no history of neck irradiation, and there is no family history of thyroid cancer. You recommend:

a) A fine-needle aspiration biopsy
b) Suppression of the nodule with levothhyroxine (Synthroid)
c) Removal of the nodule
d) A serum calcitonin level
e) A radioactive iodine uptake test and a thyroid scan

🇨🇦 MCCQE1,2 | #Case_137 | #answer
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✅ A

🔎 Explanation

In the absence of risk factors for cancer, a patient with a normal TSH level who is found to have a thyroid nodule on physical examination should have a fine-needle aspiration biopsy. Independent of morphology, fine-needle aspiration provides the most direct and specific information about a thyroid nodule

🇨🇦 MCCQE1,2 | #Case_138
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A 30-year-old white male complains of several weeks of nasal stuffiness, purulent nasal discharge, and facial pain. He does not respond to a 3-day course of trimethoprim/ sulfamethoxazole (Bactrim, Septra). Follow-up treatment with 2 weeks of amoxicillin/clavulanate (Augmentin) is similarly ineffective. Of the following diagnostic options, which one is most appropriate at this time?

a) Pulmonary function testing
b) Coronal CT of the sinuses
c) Culture and sensitivity testing of the discharge
d) Erythrocyte sedimentation rate
e) Complete Blood Count

🇨🇦 MCCQE1,2 | #Case_138 | #answer
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✅ B

🔎 Explanation

This patient has a clinical presentation consistent with acute sinusitis. Failure to respond to adequate antibiotic therapy suggests either a complication, progression to chronic sinusitis, or a different, confounding diagnosis. The diagnostic procedure of choice in this situation is coronal CT of the sinuses, due to its increased sensitivity and competitive cost when compared with standard radiographs. Cultures of the nasal discharge give unreliable results because of bacterial contamination from the resident flora of the nose. The other options listed do not contribute to the diagnosis and treatment of sinusitis

🇨🇦 MCCQE1,2 | #Case_139
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A 30-year-old male patient presents to your clinic with an ulcer on his penis. The ulcer (1x1cm) is non-tender, has a raised border and indurated base. Painless inguinal lympadenopathy is detected on physical exam. The rest of the examination is unremarkable and the review of systems is normal. What is the best diagnostic test to order for this patient?

a) Blood culture
b) Dark field microscopy
c) FTA-Abs
d) RPR
e) VDRL

🇨🇦 MCCQE1,2 | #Case_139 | #answer
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✅ B

🔎 Explanation

A painless ulcer on the genitalia is primary syphilis (Chancre) until proven otherwise. Patients with primary syphilis are best diagnosed with dark field microscopy of the lesion scraping that shows the spirochetes with its characteristic cork screw appearance. VDRL, RPR and FTA-Abs are tests looking for antibodies against syphilis. These are not helpful in primary syphilis; it takes a few weeks for these antibodies to appear in the serum. They are the diagnostic modalities of choice in secondary and tertiary syphilis. Blood culture is never helpful for syphilis as spirochetes can not be cultured.

⚠ Although the incidence of syphilis has decreased nowadays, it is frequently tested. Know its diagnostic tests and its treatment and do not forget the false positive VDRL in an SLE patient

🇨🇦 MCCQE1,2 | #Case_140
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A 40-year-old obese black male presents with a history of excessive daytime drowsiness. He readily falls asleep when reading or watching television. He admits to nearly crashing his car twice in the past month because he briefly fell sleep behind the wheel. Most frightening to the patient have been episodes characterized by sudden loss of muscle tone, lasting about 1 minute, associated with laughing. An overnight sleep study shows decreased sleep latency and no evidence of obstructive sleep apnea. Appropriate treatment includes which one of the following?

a) Methylphenidate (Ritalin)
b) Zolpidem (Ambien) at bedtime
c) Carbidopa/levodopa (Sinemet)
d) Weight reduction
e) Avoidance of daytime napping

🇨🇦 MCCQE1,2 | #Case_140 | #answer
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✅ A

🔎 Explanation

The clinical history and laboratory findings presented are consistent with a diagnosis of narcolepsy. Methylphenidate and other stimulant drugs remain the pharmacologic agents of choice in managing this disorder. Since there is no evidence of obstructive sleep apnea, weight reduction would not be expected to address his sleep problem. In general, sedatives, hypnotics, and alcohol should be avoidep. Periodic daytime naps may help to reduce symptoms

🇨🇦 MCCQE1,2 | #Case_141
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An 77-year-old man becomes "senile" over a period of 3 or 4 weeks. He used to be active and managed all of his financial affairs. Now, he stares at the wall, barely talks, and sleeps most of the day. His daughter recalls that he fell off his rocking chair about a week before the mental changes began. Which of the following would a CT scan of his head most likely show?

a) Chronic epidural hematoma
b) Chronic subdural hematoma
c) Diffuse intracerebral bleeding
d) Frontal lobe infarction
e) Generalized, severe brain atrophy