Case-based MCQ

🇨🇦 MCCQE1,2 | #Case_145 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ C 🔎 Explanation This patient’s clinical picture with abdominal pain that radiates to the groin, severe lower back pain, passing crystals in urine, and costovertebral angle tenderness are suggestive of nephro-ureterolithiasis. Moreover, given his history of taking amlodipine and fenofibrate, drugs known to be secondary uricosurics, and clear KUB, the most likely chemical composition of these stones is uric acid. Uric acid kidney stones are the known most common cause of radiolucent kidney stones. Uric acid is a weak acid, with an ionization constant of acid (pK) of 5.8. At pH levels below the pK, uric acid is predominately found in a nonionized form. The urate ion is more soluble than the nonionized molecule. When the concentration of uric acid in urine exceeds its solubility at the urine pH, uric acid changes from a compound dissolved in solution to an insoluble precipitate. Like any other type of kidney stone, the initial therapy is urine dilution with large water intake. Since uric acid crystals form at acidic pH, uric acid urolithiasis management also consists of alkalinizing the urine with either potassium citrate (choice C) or bicarbonate. Sodium urate is 15 times more soluble than uric acid. At a urine pH level of 6.8, 10 times as much sodium urate as uric acid is present. At a urine pH level of 7.8, 100 times as much urate as uric acid is present. ⚠ Increased fluids and acetohydroxamic acid (choice A) would be beneficial in struvite kidney stones. Struvite stones are associated with urease positive infectious agents, the most common of which is Proteus mirabilis. ⚠ Increased fluids and pyridoxine (choice B) therapy is more beneficial in calcium oxalate kidney stones; it would not be the most effective treatment of uric acid urolithiasis. ⚠ Increased fluids and vitamin C (choice D) is incorrect. Limitation of vitamin C ingestion is advised in patients with calcium oxalate stones because it is known to increase the risks of formation of these stones. It is not the most effective therapy for uric acid kidney stones. ⚠ Increased fluids and hydrochlorothiazide (choice E) therapy is recommended for calcium oxalate stones as hydrochlorothiazide is known to decrease calcium excretion. Hydrochlorothiazide has a tendency to cause hyperuricemia and also causes potassium loss. This hypokalemic effect would lead to reduction of citrate, which would decrease urine pH and shift the balance towards uric acid formation and the worsening of the patient’s condition. 🔖 Key point: Uric acid kidney stones are radiolucent and are not visible on KUB. The best management of these stones is hydration and alkalinization of urine with potassium citrate or bicarbonate.

🇨🇦 MCCQE1,2 | #Case_145 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 48-year-old male presents to your department with complaints of abdominal pain that radiates to his groin the last few days. He also noticed a severe gnawing lower back pain yesterday and while urinating passed what looked like sand. Past medical history is significant for hypertension treated with amlodipine and hypertriglyceridemia treated with fenofibrate. Vital signs show temperature of 37.5°C, BP 145/75 mmHg, heart rate 110bpm, and respirations 19/min. On physical examination he has costovertebral angle tenderness. The KUB is normal. After pain management, which of the following would be the most effective combination therapy of this patient's condition? ❤Increased fluids and acetohydroxamic acid 💛Increased fluids and pyridoxine 💚Increased fluids and potassium citrate 💙Increased fluids and vitamin C 💜Increased fluids and hydrochlorothiazide

🇨🇦 MCCQE1,2 | #Case_144 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation This patient is diagnosed with gastritis secondary to Helicobacter pylori infection. It usually presents with abdominal pain that worsens with food intake, heartburn or esophageal reflex, diarrhea, nausea and vomiting. Various tests can be used to make the diagnosis including esophagogastroduodenoscopy, H. pylori fecal antigen test, and H. pylori serology. Treatment should be given to patients with positive results. Treatment with triple therapy should be administered for 10-14 days. The treatment regimens are omeprazole, amoxicillin, and clarithromycin (OAC) (choice E) - for 10 days; bismuth subsalicylate, metronidazole, and tetracycline (BMT) for 14 days; and lansoprazole, amoxicillin, and clarithromycin (LAC), which is approved for either 10 days or 14 days of treatment. 4 weeks after treatment, carbon-13 urea breath test should be done to confirm eradication. ⚠ Clarithromycin, omeprazole, and fluconazole (choice A) is incorrect. Fluconazole, an antifungal is not part of the treatment regimen to eradicate bacteria. ⚠ A combination of erythromycin, esomeprazole, and metronidazole (choice B) has greater likelihood of failure, given erythromycin decreased efficacy in acid environment. Its derivative, clarithromycin is more acid-resistant and is the preferred macrolide in H. pylori eradication. ⚠ Amoxicillin-clavulanate, ranitidine, and bismuth (choice C) is incorrect. Most tested regimens that have amoxicillin also include clarithromycin, moreover, PPI are stronger acid inhibitors than antihistamines. ⚠ Bismuth, omeprazole, and metronidazole (choice D) is incorrect. Most tested regimens with metronidazole also include either tetracycline or clarithromycin. 🔖 Key point: For H. pylori eradication the most common regimens are omeprazole, amoxicillin, and clarithromycin (OAC) for 10 days; bismuth subsalicylate, metronidazole, and tetracycline (BMT) for 14 days; and lansoprazole, amoxicillin, and clarithromycin (LAC), which is approved for either 10 days or 14 days of treatment

🇨🇦 MCCQE1,2 | #Case_144 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 48-year-old male presents to your department because he has had pressure-like sensation in the upper abdomen for the last 3 weeks with abdominal pain that worsens with eating food. The pain sometimes radiates to the chest. Physical examination reveals upper abdominal tenderness on deep palpation. In the course of work up an endoscopy with biopsy is performed and reveals gastritis with Helicobacter pylori infection. What is the best treatment regimen to eradicate this infection? ❤Clarithromycin, omeprazole, and fluconazole 💛Erythromycin, esomeprazole, and metronidazole 💚Amoxicillin-clavulanate, ranitidine, and bismuth 💙Bismuth, omeprazole, and metronidazole 💜Omeprazole, amoxicillin, and clarithromycin

🇨🇦 MCCQE1,2 | #Case_143 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Penicillin is the treatment of choice for treating syphilis. For treatment of syphilis during pregnancy, no proven alternatives to penicillin exist. Treatment guidelines recommend desensitization in penicillin-allergic pregnant women (choice D), followed by treatment with penicillin. Syphilis in pregnancy is associated with mental retardation, stillbirth and sudden infant death syndrome; therefore it should be treated promptly. ⚠ Data are insufficient to recommend ceftriaxone (choice A) for treatment of maternal infection and prevention of congenital syphilis. ⚠ Erythromycin (choice C) and azithromycin should not be used, because neither reliably cures maternal infection or treats an infected fetus. ⚠ Tetracyclin (choice E) and doxycycline (choice B) are contraindicated in pregnancy and ceftriaxone is much less effective than penicillin

🇨🇦 MCCQE1,2 | #Case_144 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 An 18-year-old pregnant woman presents to the clinic for a routine checkup. She is at the 5th week of gestation. Except for morning nausea, she denies any problems with her pregnancy so far. The patient is allergic to penicillin. Physical exam is unremarkable and appropriate for gestational age. Routine screening lab tests were ordered. VDRL screening returned positive and was confirmed by the FTA-ABS test.

🇨🇦 MCCQE1,2 | #Case_143 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Meckel’s diverticulum is the most common congenital abnormality of the small intestine. It is prone to bleeding because it may contain heterotopic gastric mucosa. Abdominal pain, distention, and vomiting may develop if obstruction has occurred, and the presentation may mimic appendicitis ⚠ Children with appendicitis (choice A) have right lower quadrant pain, abdominal tenderness, guarding, and vomiting, but not rectal bleeding. ⚠ With acute viral gastroenteritis (choice B), vomiting usually precedes diarrhea (usually without blood) by several hours, and abdominal pain is typically mild and nonfocal with no localized tenderness. ⚠ The incidence of midgut volvulus (choice C) peaks during the first month of life, but it can present anytime in childhood. Volvulus may present in one of three ways: as a sudden onset of bilious vomiting and abdominal pain in the neonate; as a history of “feeding problems” with bilious vomiting that now appears to be due to bowel obstruction; or, less commonly, as a failure to thrive with severe feeding intolerance. ⚠ Necrotizing enterocolitis (choice E) is typically seen in the neonatal intensive-care unit, occurring in premature infants in their first few weeks of life. The infants are ill, and signs and symptoms include lethargy, irritability, decreased oral intake, abdominal distention, and bloody stools. A plain abdominal film showing pneumatosis intestinalis, caused by gas in the intestinal wall, is diagnostic of this disease

🇨🇦 MCCQE1,2 | #Case_143 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A previously healthy 2-year-old male is brought to your office with a 4-hour history of abdominal pain followed by vomiting. Just after arriving at your office he passes bloody stool. A physical examination reveals normal vital signs, and guarding and tenderness in the right lower quadrant. A rectal examination shows blood on the examining finger.

🇨🇦 MCCQE1,2 | #Case_142 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation Acute interstitial nephritis (AIN) is often drug-induced. Discontinuation of medications that are likely to cause AIN is the most important first step in management. If these medications are withdrawn early, most patients can be expected to recover normal renal function. Of the medications listed, ibuprofen is the most likely offending agent, because all NSAIDs are known to be associated with AIN. Development of AIN usually becomes evident approximately 2 weeks after starting a medication and is not dose-related. Other medications strongly associated with AIN include various antibiotics (particularly cephalosporins, penicillins, sulfonamides, aminoglycosides, and rifampin), diuretics, and miscellaneous medications such as allopurinol.

🇨🇦 MCCQE1,2 | #Case_142 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 62-year-old male is admitted to the hospital with acute renal failure. A renal biopsy confirms the diagnosis of acute interstitial nephritis (AIN). Infection and immune-associated causes are ruled out, and you consider medications as a potential cause. Which one of the following would be most likely to cause AIN? a) Chronic daily use of metoprolol (Lopressor) b) Twice-daily use of ibuprofen for 2 weeks c) Initiation of lisinopril (Prinivil, Zestril) therapy 1 week ago d) A 5-day course of azithromycin (Zithromax) 6 months ago e) Intermittent use of acetaminophen, up to 4 g/day

🇨🇦 MCCQE1,2 | #Case_141 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation People who are very old or alcoholic have smaller brains in a skull that has not changed in size; thus, very minimal trauma can make the brain "rattle around" and tear a venous sinus, from which a subdural hematoma very slowly forms. Senility does not occur in a 3 week period. Such marked changes in someone with recent trauma should trigger a search for chronic subdural hematoma

🇨🇦 MCCQE1,2 | #Case_141 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 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

🇨🇦 MCCQE1,2 | #Case_140 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ 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_140 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 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_139 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ 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_139 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 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_138 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ 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_138 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 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