Case-based MCQ

🇨🇦 MCCQE1,2 | #Case_213 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation The hyperoxia test is used as an early tool to evaluate the cyanotic neonate to determine if the etiology of the cyanosis is cardiac or non-cardiac in origin. A right radial artery (preductal) blood gas is performed with the child inspiring room air and 100% oxygen. The change in PaO2 with the administration of oxygen issued as a guide to determine the etiology of the cyanosis. A PaO2 of less than 150 with the administration of 100% oxygen suggests a cardiac lesion. The cardiac lesions may be further classified based upon the absolute value of the PaO2. A PaO2 of less than 50 on 100% oxygen suggests a cardiac disorder, in which there is restricted pulmonary blood flow or a separate venous and arterial circulation, whereas a PaO2 between 50 and 150 on 100% oxygen suggests that there is no restriction of pulmonary blood flow in the presence of complete mixing of oxygenated and deoxygenated blood. In this case, the PaO2 on 100% oxygen was less than 50, suggesting restricting pulmonary blood flow or a separate circulation

🇨🇦 MCCQE1,2 | #Case_213 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 You are called to evaluate a term newborn in the delivery room. The pregnancy and delivery were uneventful, but the baby has remained cyanotic despite routine delivery room care. A hyperoxia test is performed; the results of which are printed below: FiO2 = 0.21, PaO2 = 30 FiO2 = 1.00, PaO2 = 40 Which statement is the correct interpretation of the test results above? a) The test results suggest that the baby has a cardiac defect involving restricted pulmonary blood flow or a separate circulation b) The baby has a normal PaO2 for a newborn c) The test results suggest that the baby has underlying neurologic disease d) The test results suggest that the baby has a cardiac defect involving complete mixing without restricted pulmonary blood flow

🇨🇦 MCCQE1,2 | #Case_212 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation A positive dipstick for hemoglobin without any RBCs noted in the urine sediment indicates either free hemoglobin or myoglobin in the urine. Since the specimen in this case was a fresh sample, significant RBC hemolysis within the urine would not be expected. Myoglobin is released when skeletal muscle is destroyed by trauma, infarction, or intrinsic muscle disease. ⚠ If the hematuria were due to trauma there would be many RBCs visible on microscopic examination of the urine. ⚠ If a transfusion reaction occurs, haptoglobin binds enough free hemoglobin in the serum to give it a pink coloration. Only when haptoglobin is saturated will the free hemoglobin be excreted in the urine. ⚠ Free hemoglobin resorption from hematomas does not occur. ⚠ Porphyria may cause urine to be burgundy colored, but it is not associated with a positive urine test for hemoglobin

🇨🇦 MCCQE1,2 | #Case_212 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 45-year-old white male is admitted to the intensive-care unit after being pinned in a car wreck for 2 hours. He has sustained several broken bones and crush injuries to both thighs. On admission his urine is clear but the next morning it is burgundy colored. Some fresh urine is drawn from his Foley catheter and sent for analysis, with the following results: Specific gravity. ......... 1.020 pH............................... 6.0 Protein........................ 30 mg/dL (N 1-14) Glucose. .................... negative Hemoglobin................ 4+ Urobilinogen. ............. 0.1 Ehrlich Units (N 0.1-1.0) Bile............................. negative RBCs......................... 1-2/hpf WBCs. ...................... 0-2/hpf Occasional hyaline casts You immediately order a CBC which shows his hematocrit to have dropped 4 percentage points overnight. Visual inspection of the serum shows it is clear. The color of his urine is most likely due to: a) Myoglobinuria b) Hematuria from trauma to the urinary tract c) A transfusion reaction with hemolysis of RBCs and free hemoglobin into the urine d) Hemoglobinuria resulting from reabsorption of hemoglobin from hematomas e) Acute porphyria provoked by trauma

🇨🇦 MCCQE1,2 | #Case_211 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation With this patient’s history of pain out of proportion to physical findings, vomiting, bloody stool, unstable vitals and pneumatosis intestinalis on x-ray you should be highly suspicious of acute mesenteric ischemia (AMI). It is very likely that the source of the AMI was an arterial embolus most likely as a result of the patient’s atrial fibrillation (>75% of emboli originate in the heart). AMI risk factors include: atrial fibrillation, recent MI, valvular heart disease and recent vascular catheterization. The most common anatomic sites for ischemia are “Sudeck’s point” at the sigmoid flexure and “Griffith’s point” at the transverse-descending colon flexure. Immediate surgery is the gold standard for diagnosis but CT, mesenteric angiography, abdominal radiography and ECG are useful for diagnosis. ⚠ Colonoscopy, is not useful for suspected cases of AMI. ⚠ No laboratory test sufficiently rules in or rules out the diagnosis of mesenteric ischemia. Laboratory findings in mesenteric ischemia are nonspecific and generally unreliable. ⚠ Barium enema, is contraindicated. Considering a mortality rate of >50% in cases of AMI, ⚠ Watchful waiting would serve only to render a negligence lawsuit against you. 🔖 Key point: If AMI is suspected surgical exploration should not be delayed

🇨🇦 MCCQE1,2 | #Case_211 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 68-year-old man with a history of diabetes, hypertension and atrial fibrillation is admitted to the ER for severe abdominal pain. He has vomited twice in the last hour and has had one bloody stool. The patient is complaining of severe pain but your exam reveals a soft abdomen. His vitals are: HR:140 bpm, BP:85/60 mmHg, RR:19 rpm, T:38.9°C. An abdominal x-ray shows pneumatosis intestinalis (air in the bowel wall). Which of the following would be your next best step? a) Colonoscopy b) Complete blood count stat c) Barium enema d) Watchful waiting e) Exploratory laparotomy

🇨🇦 MCCQE1,2 | #Case_210 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation Treatment of hypoxemia is critical in the management of COPD and trials have shown a reduction in mortality with the use of oxygen for 15 or more hours daily. ⚠ Inhaled beta-adrenergic agonists and anticholinergic agents, either alone or in combination, provide symptomatic relief but do not prolong survival. ⚠ Theophylline can be used for symptoms inadequately relieved by bronchodilators. ⚠ Inhaled corticosteroids do not appear to alter the rate of decline in lung function in COPD. However, some evidence shows that these agents alleviate symptoms and reduce disease exacerbation. Pulmonary rehabilitation improves quality of life and reduces hospitalizations.

🇨🇦 MCCQE1,2 | #Case_210 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 An 83-year-old male has a long history of COPD. His resting oxygen saturation is 86% on room air. Treatment includes oral bronchodilators, inhaled corticosteroids, inhaled beta-agonists, inhaled anticholinergics, and home oxygen. Which one of his treatments has been shown to prolong survival in cases such as this? a) Oral bronchodilators b) Inhaled corticosteroids c) Inhaled beta-agonists d) Inhaled anticholinergics e) Home oxygen

🇨🇦 MCCQE1,2 | #Case_209 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation Hyperbilirubinemia can occur in up to 60% of term newborns during the first week of life. Early guidelines on management of elevated bilirubin were based on studies of bilirubin toxicity in infants who had hemolytic disease. Current recommendations now support the use of less intensive therapy in term newborns with jaundice who are otherwise healthy. Phototherapy should be initiated when the bilirubin level is above 15 mg/dL for infants at age 29-48 hours old, at 18 mg/dL for infants 49-72, and at 20 mg/dL in infants older than 72 hours. Generally, this problem is not considered pathologic unless it presents during the first hours after birth and the total serum bilirubin rises by more than 5 mg/dL/day or is higher than 17 mg/dL, or if the infant has signs or symptoms suggestive of a serious underlying illness such as sepsis. Fortunately, very few term newborns with jaundice have serious underlying pathology. Physiologic jaundice follows a pattern, with the bilirubin level peaking on the third or fourth day of life and then declining over the first week after birth. Infants with multiple risk factors may develop an exaggerated form of physiologic jaundice, with the total bilirubin level rising as high as 17 mg/dL. Breastfed infants are at an increased risk for exaggerated physiologic jaundice because of relative caloric deprivation in the first few days of life. Compared with formula-fed infants, those who are breastfed are six times more likely to experience moderate jaundice, with the bilirubin rising above 12 mg/dL. For breastfed newborns who have an early onset of hyperbilirubinemia, the frequency of feeding should be increased to more than 10 times per day. If the newborn has a decrease in weight gain, delayed stooling, and continued poor intake, then formula supplementation may be necessary. Breastfeeding should be continued to maintain breast milk production. Supplemental water or dextrose and water should not be given, as this can decrease breast milk production and may place the infant at risk for iatrogenic hyponatremia

🇨🇦 MCCQE1,2 | #Case_209 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A full-term newborn, born 72 hours ago, is noted to be jaundiced. The pregnancy was uneventful and the delivery uncomplicated. The mother has type A-positive blood and the child has type O-positive. The child is breastfed and has lost 9 ounces from a birth weight of 8 lb. He is feeding for 20 minutes every 4 hours, and except for being icteric, has a normal examination. Laboratory evaluation reveals a total serum bilirubin level of 16 mg/dL (N 1.4-8.7), with a conjugated bilirubin level of 1.0 mg/dL. His hemoglobin level is 17.8 g/dL (N 13.4-19.8), his hematocrit is 55% (N 41-65), and his reticulocyte count is 3% (N 3-7). Appropriate management would include: a) Phototherapy b) Exchange transfer c) Blood cultures and antibiotic therapy d) Dextrose and water supplementation e) A recommendation to increase feedings to 10 times a day

🇨🇦 MCCQE1,2 | #Case_208 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation This patient presents with constipation and symptoms suggestive of gastroparesis or delayed gastric emptying. Gastrointestinal motility is reduced in Parkinson’s disease; besides, the medications used to treat this condition can also cause constipation. Patients can have hard, dry stools that are painful to pass due to slowed motility, and delayed emptying of a full bowel due to incoordination of rectal muscles. This could lead to complications such as paralytic ileus, acute bowel obstruction secondary to impaction, volvulus, and Ogilvie’s syndrome. Generally, metoclopramide (choice B) can be used to treat gastroparesis but it is contraindicated in patients with severe Parkinson’s disease such as this patient who was recently evaluated to be in stage 4 on the Hoehn and Yahr scale of this condition. Parkinson’s disease is characterized by loss of pigmented dopaminergic neurons and since this medication is a dopamine antagonist that crosses the brain blood barrier, it would worsen the patient’s condition. ⚠ Ropinirole (choice A) and Pramipexole (choice C) are non-ergoline dopamine agonists and they are used in the treatment of Parkinson’s disease. They are not contraindicated in this patient. ⚠ Domperidone (choice D) is a peripheral dopamine (D2) and (D3) receptor antagonist. Since it doesn’t cross the brain blood barrier like Metoclopramide, it is one of the few dopamine antagonists that can be used as prokinetic to increase gastrointestinal peristalsis and promote gastric emptying in this patient. ⚠ Isradipine (choice E) is a calcium channel blocker used as an antihypertensive medication that has been recently studied for use in treating Parkinson’s disease with promising initial results. It is not contraindicated in this patient. 🔖Key point: Metoclopramide is a dopamine antagonist and should not be used in patients with severe Parkinson's disease.

🇨🇦 MCCQE1,2 | #Case_208 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 72-year-old male presents to your department with complaints of prolonged constipation, early satiety, and gastroesophageal reflux. This has led to feeling bloated most of the time and weight loss. The patient was diagnosed with Parkinson’s disease 5 years ago and is treated with Selegiiline and Levodopa-Carbidopa combination. He was recently evaluated by his neurologist and found to be in stage 4 of the Hoehn and Yahr scale of this disease. Which of the following medication is contraindicated in this patient? a) Ropinirole b) Metoclopramide c) Pramipexole d) Domperidone e) Isradipine

🇨🇦 MCCQE1,2 | #Case_207 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation This patient’s abdominal pain is most likely caused by peptic ulcer disease. His history of abdominal pain, minimal relief with omeprazole, and the laboratory test results that reveal excessive levels of gastrin point to a gastrinoma (i.e.Zollinger Ellison syndrome) as the most likely cause. This patient also has elevated levels of calcium and a family history of nephrolithiasis, which are suggestive of hyperparathyroidism. When all of this is taken into account, we must suspect multiple endocrine neoplasia type I (MEN I). This condition is a constellation of pituitary adenomas, parathyroid tumors, and pancreatic islet cell tumors. Pituitary adenomas secrete prolactin in 25% of patients and growth hormone in 5% of patients. Large pituitary adenomas may cause bitemporal hemianopsia, which is a risk factor for motor vehicle accidents in these patients. Head MRI (choice D) is considered the screening test of choice for pituitary adenomas. ⚠ Abdominal CT scan (choice A) in the study of Zollinger-Ellison syndrome is used in the staging of cancer lesion. At this point, it would not be the best next step. ⚠ Endoscopic ultrasound with biopsy (choice B) is an invasive study that should not be considered as the next step in the evaluation of this patient. Somatostatin receptor scintigraphy would be the best next step in the evaluation of Zollinger-Ellison syndrome but it was not among the choices offered. ⚠ 24-hour urine vanillylmandelic acid (choice C) is useful in evaluating patients suspected of pheochromocytoma. This would be considered in a patient suspected of MEN II. MEN II a is a constellation of pheochromocytoma, parathyroid neoplasia, and medullary carcinoma of the thyroid, while MEN IIb includes pheochromocytoma, medullary thyroid carcinoma, and intestinal neuromas. ⚠ Serum calcitonin (choice E) is also useful in the evaluation of medullary carcinoma of the thyroid in patients with MEN II. 🔖 Key point: Multiple endocrine neoplasia type I is a constellation of pituitary adenomas, parathyroid tumors, and pancreatic islet cell tumors. In a patient who presents with Zollinger-Ellison syndrome and hypercalcemia, a head MRI is indicated to screen the patient for pituitary adenoma

🇨🇦 MCCQE1,2 | #Case_207 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 35-year-old male presents to your department with severe abdominal pain. He had similar complaints 3 months ago and after evaluation he was prescribed omeprazole for peptic ulcer disease. He says that the drug seemed to help a bit initially, but currently he feels his pain is getting worse. He says that the pain is associated with food. His father died at the age of 51 in a car accident. His mother is 58 years old and healthy. He has an older brother with a history of kidney stones. On physical examination he has pain in the epigastric region. Laboratory tests show: Sodium: 140 mmol/L Chloride: 116 mmol/L Potassium: 4.8 mmol/L Bicarbonate: 19 mmol/L Magnesium: 0.85 mmol/L Calcium: 3 mmol/L BUN: 7 mmol/L Creatinine: 200 microg/L Glucose: 5.5 mmol/L Gastrin: 1.1 ng/mL (normal < 100pg/mL) If MEN is suspected, which of the following would be the best choice to arrive at the correct diagnosis? a) Abdominal CT scan b) Endoscopic ultrasound with biopsy c) 24-hour urine vanillylmandelic acid d) Head MRI e) Serum calcitonin

🇨🇦 MCCQE1,2 | #Case_206 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Diffuse, patchy infiltrate is consistent with Pneumocystis jiroveci pneumonia, which is confirmed by methenamine silver stain of lavage or biopsy sample. The first-line treatment of this condition is trimethoprim-sulfamethoxazole for patients with no contraindications to sulfa drugs. In the case of a patient with a sulfa allergy, the firstline treatment is pentamidine. ⚠Answer A is incorrect. Ivermectin is used to treat onchocerciasis (river blindness). It is thought to block the release of microfilariae from gravid female worms. One dose reduces microfilarial counts by up to 95%. ⚠Answer B is incorrect. Metronidazole is used to treat a wide variety of anaerobic bacterial infections. It is also effective against parasitic infections such as Giardia lamblia, Entamoeba histolytica, Gardnerella vaginalis, and Trichomonas vaginalis. ⚠Answer C is incorrect. Penicillin is used to treat a variety of bacterial infections but is not effective in the treatment of Pneumocystis jiroveci pneumonia. ⚠Answer E is incorrect. Protamine is used to treat heparin overdose. It binds to heparin to form a stable complex that has no anticoagulant activity. Used alone, protamine has anticoagulant properties

🇨🇦 MCCQE1,2 | #Case_206 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 40-year-old patient with AIDS presents to the clinic with fatigue and weakness. X-ray of the chest is shown in the image. A methenamine silver stain of a bronchoalveolar lavage specimen reveals multiple organisms. Treatment with trimethoprim-sulfamethoxazole is contraindicated because the patient has a sulfa allergy. Which of the following agents should be used to treat this patient’s infection? a) Ivermectin b) Metronidazole c) Penicillin d) Pentamidine e) Protamine

🇨🇦 MCCQE1,2 | #Case_205 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation Hypernatremia is plasma Na concentration > 145 mEq/L caused by a deficit of water relative to solute. A major symptom is thirst; other clinical manifestations are primarily neurologic (due to an osmotic shift of water out of cells), including confusion, neuromuscular excitability, seizures, and coma. Diagnosis is by measuring serum Na. Severely dehydrated infants must have their circulating blood volume restored first, usually with 0.9% saline in aliquots of 20 mL/kg IV. Treatment is then with 5% D/W/0.3% to 0.45% saline solution IV in volumes equal to the calculated fluid deficit, given over 2 to 3 days to avoid a rapid fall in serum osmolality, which would cause rapid movement of water into cells and potentially lead to cerebral edema. Maintenance fluids should be provided concurrently. The goal of treatment is to decrease serum Na by about 10 mEq/L/day

🇨🇦 MCCQE1,2 | #Case_205 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 6-month-old girl presents with vomiting and diarrhea of acute onset. Her systolic blood pressure is 40 mm Hg, pulse is 160/minute, she has poor peripheral circulation and is very lethargic. Her serum sodium concentration is 158 mmol/L. Which one of the following is the best initial management? a) Intravenous 0.9% saline in aliquots of 20 mL/kg b) Intravenous 5% D/W/0.3% to 0.45% saline solution c) Oral solution containing 50 mmol sodium per liter d) Septic workup e) Hydrocortisone 200 mg intravenously

🇨🇦 MCCQE1,2 | #Case_204 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ C 🔎 Explanation This patient has diabetes with proteinuria and likely has nephrotic syndrome. Among the many sequelae of nephrotic syndrome is hypercoagulability secondary to the loss of antithrombotic proteins in the urine (protein C, S, and antithrombin). These patients are at increased risk for arterial and venous thrombotic complications, including myocardial infarction, pulmonary embolism, deep vein thrombosis, and, as is the case with this patient, unilateral renal vein thrombosis (RVT). Classically, patients with RVT present with flank pain (secondary to distention of the renal capsule), hematuria, and evidence of renal impairment. Timely diagnosis via renal ultrasound, CT, or direct venography, as well as treatment with heparin, is crucial. The disruption of renal blood flow can lead to permanent damage. ⚠Answer A is incorrect. Analgesics and angiotensin-converting enzyme (ACE) inhibitors would do little to address the underlying pathology in this patient. Moreover, ACE inhibition may worsen this patient’s renal failure by decreasing the contralateral kidney’s hyper-filtration. ⚠Answer B is incorrect. These modalities are important tools for the diagnosis and treatment of nephrotic syndrome. High-dose corticosteroids are used to treat minimal change disease, among other causes of nephrotic syndrome, but they will do little to address this patient’s acute complication. ⚠Answer D is incorrect. Spiral CT is useful in diagnosing renal calculi, and administration of a thiazide diuretic is helpful in treating chronic stone formation by decreasing hypercalciuria. This patient does not have findings that are consistent with nephrolithiasis; thus,these treatments would not be helpful. ⚠Answer E is incorrect. Urine culture and antibiotics are appropriate diagnostic and treatment modalities to address acute pyelonephritis. This patient is afebrile, lacks costovertebral angle tenderness, and does not have dysuria or pyuria

🇨🇦 MCCQE1,2 | #Case_204 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 56-year-old woman with a history of diabetes and proteinuria presents to the ED complaining of right groin pain and decreased urine output for the past day. She denies any trauma, fever, or history of kidney stones or urinary tract infections. Her temperature is 37.2°C(99.0°F), blood pressure is 146/90 mm Hg, pulse is 104/min, and respiratory rate is 16/min. Heart and lung examinations are normal; she has no visible rashes and no costovertebral angle tenderness. There is trace ankle edema bilaterally. Laboratory tests show: Na+ 134 mEq/L K+ 4.9 mEq/L Cl− 100 mEq/L HCO3− 24 mEq/L Blood urea nitrogen 38 mg/dL Creatinine 1.6 mg/dL Albumin 2.2 g/dL Urinalysis 3+ blood, 4+ protein, no WBCs, no stones What is the most appropriate next step in management of this patient’s condition? (A) Analgesics and angiotensin-converting enzyme inhibitors (B) Kidney biopsy and high-dose corticosteroids (C) Renal vein ultrasound and heparin (D) Thiazides and spiral CT of the pelvis (E) Urine culture and oral quinolones