Case-based MCQ

🇨🇦 MCCQE1,2 | #Case_155 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation About 80% of kidney stones are composed of calcium, and the remainder are composed of various substances, including uric acid, cystine, xanthine and struvite. Struvite stones, a mixture of magnesium, ammonium, and phosphate, are also called infection stones, because they form only in infected urine. Calcium-containing stones are radiopaque and will show up on a plain abdominal x-ray, but pure uric acid, indinavir-induced, and cystine calculi are relatively radiolucent on plain radiography

🇨🇦 MCCQE1,2 | #Case_155 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 45-year-old man enters the hospital because of an episode of acute flank pain and hematuria. Abdominal radiograph reveals a stone in the right kidney. An intravenous urogram shows the stone to be nonobstructing. Which type of kidney stone is most likely to have caused this patient's condition? ❤Calcium oxalate 💛Uric acid 💚Xanthine 💙Struvite 💜Cystine

🇨🇦 MCCQE1,2 | #Case_154 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Hospital management of acute exacerbations of asthma should include inhaled short-acting bronchodilators in all patients. Systemic corticosteroids are recommended for all patients admitted to the hospital. The efficacy of oral prednisone has been shown to be equivalent to that of intravenous methylprednisolone. Oxygen should also be considered in most patients. Antibiotics are not recommended in the treatment of asthma exacerbations unless there is a comorbid infection. Inhaled ipratropium bromide is recommended for treatment in the emergency department, but not in the hospital. Chest physical therapy and methylxanthines are not recommended in the treatment of acute asthma exacerbations.

🇨🇦 MCCQE1,2 | #Case_154 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 24-year-old female with a past history of asthma presents to the emergency department with an asthma exacerbation. Treatment with an inhaled bronchodilator and ipratropium (Atrovent) does not lead to significant improvement, and she is admitted to the hospital for ongoing management.On examination she is afebrile, her respiratory rate is 24/min, her pulse rate is 92 beats/min, and oxygen saturation is 92% on room air. She has diffuse bilateral inspiratory and expiratory wheezes with mild intercostal retractions. Which one of the following should be considered in the acute management of this patient? ❤Chest physical therapy 💛Inhaled fluticasone/salmeterol 💚Oral azithromycin 💙Systemic corticosteroids 💜Oral theophylline

🇨🇦 MCCQE1,2 | #Case_153 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Ulcerative colitis and Crohn's disease are the two major types of inflammatory bowel diseases. Non-caseating granulomas are pathognomonic of CD, and not seen in UC. However, it should be noted that they are present in most and not all patients with CD. ⚠ Crypt abscesses may be seen in both UC and CD. ⚠ Elevated ESR is a very non-specific marker of inflammation; it can be elevated in inflammatory, neoplastic and rheumatic diseases. ⚠ Hyperplastic polyps are inflammatory polyps that denote chronic inflammatory diseases; they are non specific lesions. ⚠ Pseudomembranes are the hallmarks of Clostridium difficile colitis.

🇨🇦 MCCQE1,2 | #Case_153 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 35-year-old man businessman presents to your clinic complaining of intermittent abdominal cramps and diarrhea of two months duration. The episodes of diarrhea have increased in frequency recently and have been associated with blood per stool in the last few days. After a detailed history and physical exam, you ordered several blood tests which were significant for a microcytic anemia and elevated ESR. Colonoscopy reveals extensive disease from terminal ileum to the rectum with multiple ulcerations. Biopsies of the lesions reveal the presence of non-caseating granulomas. Which of the following findings would suggest Crohn’s disease rather than ulcerative colitis? ❤Crypt abscess 💛Elevated ESR 💚Hyperplastic polyps 💙Non caseating granulomas 💜Pseudomembranes

🇨🇦 MCCQE1,2 | #Case_152 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ C 🔎 Explanation Neuroblastoma is a cancer arising in the adrenal gland or less often from the extra-adrenal sympathetic chain, including the retroperitoneum, chest, and neck. Diagnosis is based on biopsy When sensitive assays are used, 90 to 95% of tumors produce sufficient catecholamines to increase urinary metabolites. This provides a great advantage in confirming the diagnosis of neuroblastoma, as well as in following disease activity in the care of patients with secreting tumors. The two enzymes primarily responsible for the catabolism of catecholamines are catechol-O-methyl transferase and monoamine oxidase. Dopa and dopamine are converted primarily to homovanillic acid, whereas norepinephrine and epinephrine are converted primarily to vanillylmandelic acid. Most laboratories involved in neuroblastoma diagnosis measure levels of both homovanillic acid and vanillylmandelic acid in the urine. Because of the varied clinical presentation, neuroblastoma can be confused with other neoplasms as well as nonneoplastic conditions. Diagnosis of the 5 to 10% of tumors that do not produce catecholamines is particularly difficult, as is that of the 1 % or so in which the primary tumor is not obvious. The conventional diagnostic imaging modalities include plain radiography, bone scintigraphy, CT, and MRI. The potential specificity and sensitivity of metaiodobenzylguanidine (MIBG) scintigraphy for evaluation of bone and soft-tissue involvement of neuroblastoma are attractive

🇨🇦 MCCQE1,2 | #Case_152 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 You suspect a neuroblastoma in a 4-year-old boy with headaches and hypertension. Which one of the following investigations provides a great advantage in confirming the diagnosis, as well as in following disease activity in the care of patients with secreting tumors? ❤Serum alpha-fetoprotein 💛Serum ferritin and lactate dehydrogenase 💚Levels of homovanillic acid and vanillylmandelic acid in the urine 💙Serum catecholamines 💜MRI or CT scan of the involved area of the body

🇨🇦 MCCQE1,2 | #Case_151 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation Lower urinary tract obstruction in a newborn or young boy should be assumed to be caused by posterior urethral valves (choice B) until proven otherwise. These valves consist of folds of mucosa obstructing the urethra at the prostatic level. A lower abdominal mass may represent a markedly distended urinary bladder. The diagnosis can be confirmed by voiding cystourethography or by endoscopy of the urethra. The prognosis depend on the extent of renal damage at the time of diagnosis

🇨🇦 MCCQE1,2 | #Case_151 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A week-old white male is brought to your office because of “irritability”. The physical examination is normal except for a suprapubic mass. When the mother is questioned, she tells you that the infant has a dribbling urinary stream. The most likely diagnosis is: ❤Wilms’ tumor 💛Posterior urethral valves 💚Urinary tract infection 💙Spina bifida occulta involving the sacral plexus 💜Horseshoe kidney

🇨🇦 MCCQE1,2 | #Case_150 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation The radial nerve provides cutaneous innervation to the dorsum of the hand. As such, an injury to that nerve can cause deficient sensation on the dorsum (back of) the hand. Because she has intact sensation on the palmar surface of her hand, her median and ulnar nerves are not likely injured.

🇨🇦 MCCQE1,2 | #Case_150 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 45-year-old female presents with a history of a direct blow over the shaft of her left humerus. Her x-ray shows a spiral fracture of the distal third of the humerus. On examination of her hand, sensation is intact on the palmar side but absent on the dorsum of her hand. Which one of the following nerves is most likely injured? ❤Axillary nerve 💛Musculocutaneous nerve 💚Median nerve 💙Radial nerve 💜Ulnar nerve

🇨🇦 MCCQE1,2 | #Case_149 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation The most common cause for a cystic enlargement of the ovary in a reproductive age woman is a functional cyst (follicular or corpus luteum). These are thin walled and usually resolve or rupture spontaneously. Any cystic mass 6 cm or less can be followed for two cycles. Some texts recommend using oral contraceptive pills to decrease the gonadotropin stimulation of the ovary during this time, but there is no literature that shows any improvement over simple observation. -If the mass persists, further evaluation and possible surgical intervention is indicated. Laparoscopic surgery is less invasive and just as successful as laparotomy. -As most cystic masses in the adnexa are functional cysts that resolve spontaneously, no other workup is indicated at this time

🇨🇦 MCCQE1,2 | #Case_149 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 19-year-old nulligravid healthy woman comes to see you for her annual Pap smear and routine health care maintenance. During your routine pelvic exam, you note that she has a 5-cm cystic, nontender, mobile mass in her left adnexa. Rectovaginal exam confirms this and does not note any abnormalities in the cul-de-sac. Transvaginal ultrasonography results are consistent with pelvic exam findings. Which of the following is the most appropriate next step? ❤Laparotomy with ovarian cystectomy 💛Repeat ultrasound in 2 months 💚MRI scan of the pelvis 💙Serum CA-125 💜Laparoscopy with ovarian cystectomy

🇨🇦 MCCQE1,2 | #Case_148 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation A history of kitten scratch (choice A) in this patient would suggest diagnosis of cat scratch disease. Patients with cat scratch disease typically present with tender lymphadenopathy usually of a single lymph node that is tender, red, and warm. Most of these patients usually develop a few red-brown papules at the site of cat scratch days before development of lymphadenopathy. Some patients may also have hepatosplenomegaly. Our patient showed most of these symptoms and signs, and a history of kitten scratch supports the diagnosis of cat scratch disease. This disease is caused Bartonella henselae, which is transmitted from cat to humans. ⚠ Working in the forest (choice B) is less likely to support a specific diagnosis in this patient. Working in the forest would support the diagnosis of Lyme disease. However, the symptoms and signs of this patient are not suggestive of such a diagnosis. Most patients with Lyme disease present with erythema migrans, which classically starts with a single maculae or papulae at the site of tick bite. The eruption then expands over days to weeks rather than disappearing within days as in our patient. Patients with this disease usually report flu-like symptoms within a week after infection with Borrelia burgdorferi, inoculated by the tick. Lyme disease is not usually associated with lymphadenopathy but may be accompanied by lymphocytomas, which are almost always located in the ear lobe or breast nipple. Also, Lyme disease is usually not associated with hepatosplenomegaly. For all these reasons Lyme disease is an unlikely diagnosis and working in the forest is not likely to support specific diagnosis in this patient. ⚠ Residence in Rocky mountain region (choice C) would support the diagnosis of Rocky Mountain spotted fever. However, the symptoms and sings of this patient are not suggestive of this disease. Rocky Mountain spotted fever, a disease caused by Rickettsia rickettsia and transmitted by Dermacentor ticks, typically presents with rash that begins on the wrist and ankles and then spreads to arms legs and trunk. The rash also involves the palms and soles. ⚠ Having a sibling with Hodgkin’s lymphoma (choice D) is not likely to support a specific diagnosis in this patient. Hodgkin’s lymphoma presents with painless, non-tender enlargement of lymph nodes usually in the cervical region. Siblings of patients with Hodgkin’s lymphoma have a 3 to 7 time increase in the risk of developing this disease. However, this diagnosis is not supported by symptoms and signs of this patient. ⚠ History of flu-like symptoms in the past two months (choice E) is not likely to support a specific diagnosis in this patient. This symptom typically occurs in patients with Lyme disease and Rocky Mountain spotted fever. Both of these diseases are unlikely in this patient (see explanation above). 🔖 Key point: With tender lymphadenopathy and hepatosplenomegaly preceded by localized rash, cat scratch disease should be strongly suspected and history of exposure to cats or kittens sought.

🇨🇦 MCCQE1,2 | #Case_148 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 21-year-old man presented to his family physician with a swelling in his left axilla. He recalls that about two weeks ago he observed red papules on the back of his left hand, which were not tender or painful disappeared in about two days. Physical examination: heart rate 91 beat per minute, respiratory rate 16 per minute, blood pressure 124/76 mmHg and body temperature 37.2°C. An enlarged tender, erythematous, warm single lymph node could be palpated in his left axilla. Both liver and spleen were slightly enlarged. The rest of his physical examination was normal. Which of the following pieces of history is most likely to support your presumptive diagnosis in this patient? ❤Kitten scratch 💛Working in the forest 💚Residence in Rocky mountain region 💙Having a sibling with Hodgkin’s lymphoma 💜History of flu-like symptoms in the past two months

🇨🇦 MCCQE1,2 | #Case_147 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Infectious keratitis must be considered in the differential diagnosis for anyone presenting with pain, redness, and tearing of the eyes. Contact lens users are more prone to infectious keratitis and the causative organism is usually bacterial but can be viral, fungal or protozoan. Urgent ophthalmology referral is needed to exclude or confirm the diagnosis of infectious keratitis and to determine the causative organism (choice D). ⚠ Regular use of topical anesthetic is not a form of therapy for a patient with infectious keratitis (choice A). ⚠ Use of topical steroids (choice B and C) prior to determining the microbial origin and appropriate antimicrobial therapy can worsen the condition. Indiscriminate use of topical steroids for infectious keratitis can lead to blindness. ⚠ Topical antibiotic treatment alone (choice E) may not only be ineffective but also delay appropriate treatment if the causative organism is viral, fungal or protozoan; and should be considered only if urgent ophthalmology opinion is not possible. 🔖 Key point: A diagnosis of infectious keratitis should be considered in a patient presenting with painful red eye and urgent ophthalmology opinion should be sought. If the patient is wearing contact lenses, it should be discontinued until the red eye has completely resolved

🇨🇦 MCCQE1,2 | #Case_147 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 24-year-old man presents to the emergency department with severe pain, redness and tearing from his right eye for 12 hours duration. He is a regular contact lens user and his visual acuity with the contact lenses on is 20/20 for each eye. How would you treat this patient? ❤Prescribe topical analgesics and review in 24 hours 💛Prescribe topical antibiotic and steroid combination and review in 24 hours 💚Prescribe topical antibiotic and steroid combination with topical anesthetics 💙Remove the contact lens and request urgent ophthalmology opinion 💜Remove the contact lens and treat with topical antibiotics

🇨🇦 MCCQE1,2 | #Case_146 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Contact dermatitis is one of the most common inflammatory skin diseases in the industrialized world. Contact dermatitis can be of four categories: irritant contact dermatitis, photocontact dermatitis, contact urticaria and allergic contact dermatitis. This is a classical patient of allergic contact dermatitis (ACD). It can appear anywhere on the body, depending on the allergen responsible. For example, the usual sites of nickel allergy are on the abdomen from snaps on pants or buckles, and the wrists and earlobes from jewelry. The symptoms usually appear after 12-48 hours after exposure, which include erythematous papules, edema, and vesiculation. There may be tremendous itching and the lesions may involve beyond the areas of first contact. A long-lasting ACD may show lichenification and hyperpigmentation of the affected skin. A patch testing is a provocation test to identify hypersensitivity (type-IV) to potential agents that may cause contact dermatitis. It takes 48-96 hours to formulate the result. After 48 hours the initial reading is taken and after 96 hours the final result is formulated. The patch test may be positive or negative. Positive results are expressed as 1+, 2+, or 3+. This test even may be +/- when only macular erythema is noted. A 2+ reaction means that patch reaction contains papules (choice D), which is a discrete elevation of skin of ≤ 1 cm diameter. ⚠ No change (choice A) or no evidence of skin changes is considered a negative reaction. ⚠ Only erythema (choice B) or redness over the area is not a definitive landmark that’s why it is not reportable. ⚠ Redness or erythema and edema (choice C) is reported as 1+ response. Here the area of skin will be red and edematous or elevated than the surrounding normal skin. ⚠ If the reaction contains vesicles or bullae (choice E), the report will be 3+. A small area (≤ 1 cm in diameter) with fluid-filled blister is termed as vesicle. When the area is larger (> 1 cm in diameter) with fluid-filled blister is termed as bullae 🔖 Key point: A patch testing is a provocation test to identify hypersensitivity (type-IV) to potential agents that may cause contact dermatitis. A 1+ reaction consists of erythema and edema, 2+ reaction contains papules, and a 3+ reaction has vesicles or bullae

🇨🇦 MCCQE1,2 | #Case_146 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 36-year-old female school teacher presents to you with a history of itching, swelling, and redness over the extensor aspect of forearm just above the wrist for few days, notable after wearing her new watch. She explains that the day after wearing the new watch first, the itching started and immediately the area increased beyond the watch-margin. On examination, there is hyperpigmentation over the area and itching mark is also evident. You advised a “patch test”. Suppose the report is 2+, then how will you remark it? ❤No change 💛Erythema only 💚Erythema and edema 💙Papules 💜Vesicle or bullae