Medical Q&A : find your quiz answers here !

Which of the following is the first-line treatment for primary hyperparathyroidism?

A. Bisphosphonates
B. Calcimimetics
C. Parathyroidectomy
D. Vitamin D supplementation

The first-line treatment for primary hyperparathyroidism is:

C. Parathyroidectomy

Explanation:
Primary hyperparathyroidism is a condition characterized by excessive secretion of parathyroid hormone (PTH) due to one or more hyperfunctioning parathyroid glands. The definitive treatment is parathyroidectomy, especially in patients who meet surgical criteria or are symptomatic.

Key Points:

1. Indications for Parathyroidectomy:
   
   • Symptomatic hypercalcemia.
   • Osteoporosis or fractures.
   • Kidney stones (nephrolithiasis).
   • Hypercalciuria with reduced kidney function.
   • Age <50 years or serum calcium >1 mg/dL above the upper normal limit.
2. Other Treatments:
   
   • Bisphosphonates: Used to manage bone loss but do not address the underlying problem.
   • Calcimimetics (e.g., cinacalcet): Effective in reducing calcium levels in patients who cannot undergo surgery, particularly in secondary hyperparathyroidism or parathyroid carcinoma.
   • Vitamin D supplementation: Useful for concurrent vitamin D deficiency but not as a primary treatment for hyperparathyroidism.

Parathyroidectomy remains the gold standard for definitive management in appropriate candidates.

 

Which antibiotic is most commonly associated with Clostridium difficile infection?

A- Penicillin
B- Ciprofloxacin
C- Clindamycin
D- Metronidazole

The correct answer is:

Clindamycin
Explanation:
Clostridium difficile (C. difficile) infection (CDI) is a condition often associated with the use of antibiotics, which disrupt the gut microbiota, allowing C. difficile to proliferate and produce toxins.

1. Clindamycin is the antibiotic most strongly linked to CDI. It is a broad-spectrum antibiotic that disrupts normal gut flora significantly, creating an environment conducive to C. difficile overgrowth.
   
   
2. Other Antibiotics Associated with CDI:
   
   • Fluoroquinolones (e.g., Ciprofloxacin): Increasingly recognized as a cause of CDI in the past decade.
   • Cephalosporins (e.g., Ceftriaxone): Broad-spectrum activity can also disrupt gut flora.
   • Penicillins: Broad-spectrum forms like amoxicillin-clavulanate have been linked to CDI but less so compared to clindamycin.
3. Metronidazole: This is not a risk factor for CDI but is instead used as a treatment option for mild-to-moderate cases of the infection.
   

Clinical Note:
Antibiotic stewardship is critical to reduce the incidence of CDI. Avoiding unnecessary use of high-risk antibiotics, especially in elderly or immunocompromised patients, is essential for prevention.

 

1. What is the first-line treatment for hypertensive emergency?

A- Labetalol
B- Enalapril
C- Nifedipine
D- Furosemide

Correct Answer: Labetalol
Explanation:
A hypertensive emergency is a severe elevation in blood pressure (BP) (typically >180/120 mmHg) with evidence of acute or ongoing target organ damage, such as hypertensive encephalopathy, stroke, myocardial infarction, pulmonary edema, or acute kidney injury.

First-line treatment in hypertensive emergency:

1. Goal:
   
   • Lower the mean arterial pressure (MAP) by no more than 25% within the first hour to avoid ischemia.
   • Further reduce BP to 160/100-110 mmHg within the next 2-6 hours.
2. Labetalol:
   
   • Mechanism: A combined alpha-1 and beta-blocker that reduces BP without causing reflex tachycardia.
   • Advantages:
     • Can be administered intravenously, allowing precise titration.
     • Fast onset of action (within 5 minutes).
     • Suitable for most hypertensive emergencies, including those involving neurological or cardiovascular complications.

Why not the others?

1. Enalapril:
   
   • An angiotensin-converting enzyme (ACE) inhibitor.
   • Administered orally or intravenously.
   • Onset is slower (1-4 hours), making it unsuitable for immediate BP control.
   • Not commonly used in acute hypertensive emergencies.
2. Nifedipine:
   
   • A dihydropyridine calcium channel blocker.
   • Oral formulations have been used historically, but sublingual or immediate-release nifedipine can lead to excessive and unpredictable BP lowering, increasing the risk of ischemia.
   • No longer recommended for hypertensive emergencies.
3. Furosemide:
   
   • A loop diuretic.
   • Useful in cases of hypertensive emergencies associated with fluid overload or pulmonary edema.
   • Not appropriate as monotherapy for acute BP reduction, as it does not directly address the acute BP rise or provide immediate control.

 

Which of the following is the gold standard for diagnosing obstructive sleep apnea?

A- Overnight oximetry
B- Polysomnography
C- Home sleep apnea test
D- Epworth Sleepiness Scale
The gold standard for diagnosing obstructive sleep apnea (OSA) is:

Correct Answer: Polysomnography (PSG)
Explanation:
Polysomnography (PSG) is an overnight sleep study conducted in a sleep lab that provides the most comprehensive assessment of sleep patterns, respiratory events, oxygen levels, heart rate, and brain activity. It allows for direct measurement of apnea-hypopnea index (AHI), arousals, and sleep architecture, making it the most definitive test for OSA.

Why Not the Other Options?

1. Overnight Oximetry – Not the gold standard
   
   • Measures oxygen saturation levels overnight, detecting intermittent desaturation that may suggest OSA.
   • Limitation: Cannot differentiate between central vs. obstructive sleep apnea and does not measure airflow or effort.
2. Home Sleep Apnea Test (HSAT) – Useful but not the gold standard
   
   • Used for moderate-to-high suspicion of OSA in patients without other comorbid conditions.
   • Measures airflow, respiratory effort, and oxygen levels, but lacks detailed brain activity, sleep staging, and arousal assessment.
   • Less accurate in detecting mild OSA and central sleep apnea.
3. Epworth Sleepiness Scale (ESS) – Screening tool, not diagnostic
   
   • A subjective questionnaire assessing daytime sleepiness.
   • Helpful in identifying OSA risk, but does not confirm the diagnosis.

Key Takeaway:

• Polysomnography remains the gold standard for diagnosing obstructive sleep apnea due to its ability to provide the most detailed and accurate assessment of sleep-related breathing disorders.

 

What is the most common cause of macrocytic anemia?
A- Iron deficiency
B- Vitamin B12 deficiency
C- Anemia of chronic disease
D- Thalassemia

The correct answer is: Vitamin B12 deficiency

Explanation:
Macrocytic anemia is characterized by an increased mean corpuscular volume (MCV) > 100 fL. The most common cause of macrocytic anemia is Vitamin B12 deficiency, followed closely by Folate deficiency.

Why is Vitamin B12 deficiency the most common cause?

• B12 is essential for DNA synthesis, particularly in rapidly dividing cells such as red blood cells (RBCs). When B12 is deficient, nuclear maturation is impaired, leading to large, immature RBC precursors (megaloblasts) in the bone marrow.
• This results in megaloblastic anemia, a subtype of macrocytic anemia.
• Causes include pernicious anemia, malabsorption (e.g., Crohn’s disease, celiac disease), chronic alcoholism, and dietary deficiency (especially in strict vegetarians/vegans).
• Other features include neurological symptoms (e.g., peripheral neuropathy, ataxia, dementia) due to impaired myelin synthesis.

Why not the other options?

1. Iron deficiency → Leads to microcytic anemia (low MCV, typically <80 fL), not macrocytic.
2. Anemia of chronic disease → Usually results in normocytic or microcytic anemia, not macrocytic.
3. Thalassemia → A genetic disorder causing microcytic anemia (low MCV due to defective hemoglobin synthesis), not macrocytic.

 

Which of the following is the recommended treatment for latent tuberculosis infection?

A- Isoniazid
B- Rifampin
C- Ethambutol
D- Pyrazinamide

the recommended treatment for latent tuberculosis infection (LTBI) is:

Answer: Isoniazid (INH)
However, Rifampin (RIF) is also used as an alternative regimen in certain cases.

Explanation:
Latent tuberculosis infection (LTBI) occurs when a person is infected with Mycobacterium tuberculosis but does not show symptoms and cannot transmit the disease. The goal of treatment is to prevent progression to active TB disease.

First-Line Treatment Options for LTBI:

1. Isoniazid (INH) for 6-9 months (Preferred regimen)
   
   • Dose: 300 mg/day for adults
   • Duration: 6 or 9 months (9 months preferred for higher efficacy)
   • Effectiveness: Reduces the risk of developing active TB by 90%.
   • Side Effects: Hepatotoxicity, peripheral neuropathy (prevented with pyridoxine/B6 supplementation)
2. Rifampin (RIF) for 4 months (Alternative regimen)
   
   • Used for patients who cannot tolerate INH or in settings with high INH resistance.
   • Shorter duration (4 months) improves adherence.
   • Contraindications: Interactions with many drugs (e.g., oral contraceptives, anticoagulants).
3. Isoniazid + Rifapentine for 3 months (3HP regimen)
   
   • Once-weekly dose supervised (directly observed therapy or self-administered)
   • Shortens treatment, increasing adherence.
   • Not recommended in HIV patients on certain antiretrovirals.

Incorrect Options:

• Ethambutol → Used for active TB but not in LTBI treatment.
• Pyrazinamide → Part of the first-line regimen for active TB, not LTBI.

 

1. What is the most common presenting symptom of aortic dissection?

A- chest pain
B- Syncope
C- Abdominal pain
D- back pain

Most Common Presenting Symptom of Aortic Dissection:
Answer: chest pain
Explanation:
Aortic dissection is a life-threatening condition characterized by the tearing of the aortic wall, leading to blood entering the false lumen and separating the layers of the vessel. The most common presenting symptom is sudden, severe chest pain, often described as tearing, ripping, or stabbing in nature. This pain is typically located in the anterior chest for ascending aortic dissections and in the back or between the scapulae for descending aortic dissections.

Why Not the Other Options?

• Syncope: While aortic dissection can cause syncope due to rupture, cardiac tamponade, or cerebrovascular involvement, it is not the most common presenting symptom.
• Abdominal Pain: This can occur if the dissection extends to the abdominal aorta, but it is less common than chest pain.
• back pain: back pain is a frequent symptom, particularly in descending dissections, but chest pain remains the most common initial presentation.

 

1. Which of the following is the most common cause of conductive hearing loss in adults?

A- Otosclerosis
B- Cholesteatoma
C- Otitis media
D- Tympanic membrane perforation

Answer: Otosclerosis
Explanation:
Otosclerosis is the most common cause of conductive hearing loss in adults. It is a progressive disease of the middle earwhere abnormal bone remodeling leads to fixation of the stapes in the oval window, preventing sound transmission to the inner ear.

Why Not the Other Options?

• Cholesteatoma: While cholesteatoma can cause conductive hearing loss, it is less common and usually associated with chronic ear infections.
• Otitis Media: This can lead to temporary conductive hearing loss but is more common in children and typically resolves with treatment.
• Tympanic Membrane Perforation: This can cause conductive hearing loss, but it is usually due to trauma, infection, or barotrauma and is not the most frequent cause in adults.

 

1. Which of the following is the most common cause of acute limb ischemia?

A- Embolism
B- Thrombosis
C- Trauma
D- Aneurysm
Correct Answer: Embolism
Explanation:
Acute limb ischemia (ALI) is a sudden decrease in limb perfusion that threatens the viability of the affected extremity. The most common cause of acute limb ischemia is embolism, accounting for approximately 80-90% of cases.

1. Embolism (Most Common Cause)
   
   • Source: The embolus often originates from the heart (cardiac embolism), especially in patients with atrial fibrillation, recent myocardial infarction, valvular disease, or a left ventricular thrombus.
   • Mechanism: The embolus travels through the arterial system and lodges in a distal artery, obstructing blood flow abruptly.
   • Clinical Clues: Sudden onset of pain, pallor, pulselessness, paresthesia, paralysis, and poikilothermia (the "6 Ps" of acute limb ischemia).
2. Thrombosis (Second Most Common Cause)
   
   • Can occur in a preexisting atherosclerotic artery or within a bypass graft.
   • More gradual onset compared to embolic causes.
   • Patients may have a history of peripheral artery disease (PAD) or known arterial stenosis.
3. Trauma (Less Common but Important Cause)
   
   • Can lead to vascular disruption or arterial dissection.
   • Seen in cases of penetrating injuries, fractures, or iatrogenic complications from arterial catheterization.
4. Aneurysm
   
   • While an aneurysm can predispose to thrombosis or act as a source of emboli, it is not the most common primary cause of acute limb ischemia.
   • Popliteal artery aneurysm is a well-known cause of chronic embolization leading to ALI.

Thus, embolism is the most common cause of acute limb ischemia, particularly in patients with atrial fibrillation or recent cardiac events.

 

What is the primary treatment for severe preeclampsia?
A- Magnesium sulfate
B- Labetalol
C- Hydralazine
D- Delivery of the baby

Primary Treatment for Severe Preeclampsia: Delivery of the Baby

The primary and definitive treatment for severe preeclampsia is delivery of the baby. Preeclampsia is a serious pregnancy-related condition characterized by high blood pressure and signs of organ dysfunction, such as proteinuria, liver dysfunction, or thrombocytopenia. When severe preeclampsia occurs, the only way to completely resolve the condition and prevent further complications is delivery, as preeclampsia is a disorder unique to pregnancy and resolves only after the placenta is removed.

Why is Delivery the Primary Treatment?

• Eliminates the Source of the Condition: Preeclampsia is believed to be caused by abnormal placental development and function. Once the baby and placenta are delivered, maternal symptoms begin to improve.
• Prevents Maternal and Fetal Complications: Severe preeclampsia can lead to eclampsia (seizures), stroke, HELLP syndrome (Hemolysis, Elevated Liver enzymes, and Low Platelets), and multi-organ failure in the mother. It also increases the risk of placental abruption, intrauterine growth restriction (IUGR), and fetal distress.
• Timing of Delivery:
  • If severe preeclampsia occurs at or beyond 34 weeks of gestation, immediate delivery is recommended to prevent complications.
  • If severe preeclampsia occurs before 34 weeks, a decision is made based on maternal and fetal status. In stable cases, corticosteroids may be given to accelerate fetal lung maturity, and delivery is planned when the risks of continuing the pregnancy outweigh the benefits.
  • If maternal or fetal conditions deteriorate (e.g., severe hypertension, worsening organ dysfunction, or fetal distress), immediate delivery is necessary regardless of gestational age.

Supportive Treatments for Severe Preeclampsia
Although delivery is the only definitive treatment, supportive management is crucial to prevent maternal and fetal complications before delivery.

1. Magnesium Sulfate (For Seizure Prophylaxis)

• Purpose: Given to prevent progression to eclampsia (seizures).
• Mechanism: Acts as a central nervous system depressant, reducing the risk of seizures.
• Indication: All women with severe preeclampsia should receive magnesium sulfate intravenously (IV) during labor and for 24 hours postpartum.

2. Antihypertensive Medications (For Severe Hypertension)

• Purpose: Reduce the risk of stroke and organ damage caused by severe hypertension (BP ≥ 160/110 mmHg).
• Common Options:
  • Labetalol (IV) – First-line treatment; combined alpha and beta-blocker that lowers BP without reducing uteroplacental blood flow.
  • Hydralazine (IV) – Arteriolar vasodilator used when labetalol is contraindicated.
  • Nifedipine (Oral, Immediate-Release) – Calcium channel blocker that can be used in hypertensive emergencies.
• Caution: BP should not be lowered too aggressively, as this can reduce placental perfusion and cause fetal distress.

 

Which of the following is the most common cause of erythema multiforme?

A- Herpes simplex virus
B- Mycoplasma pneumoniae
C- Drug reactions
D- systemic lupus erythematosus

The most common cause of erythema multiforme (EM) is Herpes simplex virus (HSV).

Explanation:
Erythema multiforme is an acute, immune-mediated condition characterized by targetoid skin lesions. It is classified into two types:

1. Erythema multiforme minor – involves only the skin and is often associated with HSV infection.
2. Erythema multiforme major – involves mucosal surfaces and is less commonly linked to HSV.

Among the given options:

• Herpes simplex virus (HSV): The leading cause of erythema multiforme, especially HSV-1. It triggers an immune response, leading to the characteristic target lesions.
• Mycoplasma pneumoniae: More commonly associated with erythema multiforme major and Stevens-Johnson syndrome (SJS) in children.
• Drug reactions: Though drugs (e.g., sulfonamides, NSAIDs, and anticonvulsants) can cause Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN), they are not the most common cause of erythema multiforme.
• systemic lupus erythematosus (SLE): Can present with skin rashes, but it is not a primary cause of erythema multiforme.

 

What is the most common genetic cause of intellectual disability?
A- Down syndrome
B- Fragile X syndrome
C- Klinefelter syndrome
D- Turner syndrome

Answer: Fragile X Syndrome
Explanation:
Fragile X syndrome is the most common inherited genetic cause of intellectual disability. It is caused by a CGG trinucleotide repeat expansion in the FMR1 gene on the X chromosome, leading to silencing of the gene and impaired production of FMRP, a protein crucial for normal neural development.

Why Not the Other Options?

• Down Syndrome: While Down syndrome (Trisomy 21) is the most common chromosomal cause of intellectual disability, Fragile X syndrome is the most common inherited genetic cause.
• Klinefelter Syndrome (47,XXY): This condition affects males and is associated with mild learning disabilities, but it is not a leading cause of intellectual disability.
• Turner Syndrome (45,X): This condition affects females and is linked to normal intelligence in most cases, although some may have specific learning difficulties, particularly in math and spatial reasoning.

Key Takeaway:

• Fragile X syndrome is the most common inherited genetic cause of intellectual disability.
• Down syndrome is the most common chromosomal cause of intellectual disability but is usually not inherited.

 

Which of the following is the first-line treatment for bacterial vaginosis? A- Metronidazole
B- Clindamycin
C- Doxycycline
D- Fluconazole

Answer: Metronidazole

Explanation:
Bacterial vaginosis (BV) is a condition characterized by an imbalance of the vaginal flora, specifically a decrease in Lactobacillus species and an overgrowth of anaerobic bacteria. The Centers for Disease Control and Prevention (CDC) recommends metronidazole as the first-line treatment for BV because of its effective coverage against the anaerobes typically involved.

• Metronidazole: Administered either orally (500 mg twice daily for 7 days) or as a 0.75% gel intravaginally (once daily for 5 days), it is considered the standard first-line therapy for BV.
• Clindamycin: While also effective, it is generally reserved as an alternative treatment, especially for patients who cannot tolerate metronidazole.
• Doxycycline: Not effective for BV as its antimicrobial spectrum does not adequately cover the anaerobic bacteria involved.
• Fluconazole: Primarily used to treat fungal infections such as candidiasis, not bacterial infections like BV.

Thus, metronidazole remains the first-line treatment choice for bacterial vaginosis.

 

Which of the following is the most common cause of hematuria in adults?

A- Urinary tract infection
B- Kidney stones
C- Bladder cancer
D- Glomerulonephritis

Answer: Urinary tract infection

Explanation:
Hematuria, or the presence of blood in the urine, can result from several pathologies. In the general adult population, especially among women, urinary tract infections (UTIs) are the most frequent cause. In UTIs, inflammation of the urinary tract leads to irritation and subsequent bleeding, which may be microscopic or gross. Although kidney stones, bladder cancer, and glomerulonephritis can also cause hematuria, their incidence is lower compared to UTIs in the adult population overall. Thus, UTIs are recognized as the most common cause of hematuria in adults.

 

1. What is the most common cause of gynecomastia in adult males?

A- Liver cirrhosis
B- Klinefelter syndrome
C- Drug side effects
D- Testicular tumors

Most Common Cause of Gynecomastia in Adult Males: Drug Side Effects
Explanation:
The most common cause of gynecomastia in adult males is drug side effects (medication-induced gynecomastia). Several medications interfere with the normal balance of testosterone and estrogen, leading to increased breast tissue growth in men.

Why Are Drugs the Leading Cause?

• Many drugs can inhibit testosterone production, increase estrogen levels, or block androgen receptors, leading to gynecomastia.
• Some drugs directly stimulate breast tissue growth.
• The likelihood of drug-induced gynecomastia increases with prolonged use and age due to reduced testosterone levels in older men.

Common Drugs Associated with Gynecomastia:

1. Anti-androgens – Used for prostate conditions (e.g., finasteride, bicalutamide, spironolactone).
2. Cardiac and blood pressure medications – Calcium channel blockers, digoxin.
3. Psychotropic drugs – Antipsychotics (e.g., risperidone, haloperidol), antidepressants.
4. Anabolic steroids – Lead to hormone imbalance.
5. Proton pump inhibitors (PPIs) – Cimetidine has weak anti-androgenic properties.
6. Recreational substances – Alcohol, marijuana, heroin.

Other Causes Considered:

1. Liver Cirrhosis
   
   • Cirrhosis leads to impaired estrogen metabolism, resulting in elevated estrogen levels and gynecomastia.
   • While common in chronic liver disease, it is not the most frequent cause in the general adult male population.
2. Klinefelter Syndrome (XXY Syndrome)
   
   • A genetic disorder characterized by testicular failure and low testosterone production.
   • Men with Klinefelter syndrome often develop gynecomastia, but this condition is rare in the general population.
3. Testicular Tumors
   
   • Leydig cell tumors and Sertoli cell tumors can produce estrogen, leading to gynecomastia.
   • Though a serious cause, testicular tumors are relatively uncommon compared to medication-induced gynecomastia.

Conclusion:
Drug side effects are the most common cause of gynecomastia in adult males. Physicians should review a patient’s medication history when evaluating gynecomastia before considering other causes. If drug-induced gynecomastia is suspected, discontinuing or switching medications can help resolve the condition.

 

Which of the following is the most common cause of sudden painless loss of vision in one eye?

A- Retinal detachment
B- Central retinal artery occlusion
C- Optic neuritis
D- Vitreous hemorrhage

Answer:
Central Retinal Artery Occlusion (CRAO)

Explanation:
Central retinal artery occlusion (CRAO) is the most common cause of sudden, painless loss of vision in one eye. It occurs due to an obstruction of blood flow in the central retinal artery, typically from an embolic event (e.g., from carotid artery disease or cardiac sources such as atrial fibrillation).

Key Clinical Features:

• Sudden, painless, and profound loss of vision (often described as a "black curtain descending").
• Afferent pupillary defect (Marcus Gunn pupil) due to retinal ischemia.
• Fundoscopic findings:
  • Pale retina with a cherry-red spot at the fovea.
  • Boxcar segmentation of retinal arteries due to stagnant blood flow.

Why Not the Other Options?

1. Retinal Detachment:
   • Typically causes progressive vision loss with flashing lights (photopsia) and floaters.
   • May have a “curtain effect” over vision but is usually not as sudden and complete as CRAO.
2. Optic Neuritis:
   • Often painful and associated with multiple sclerosis.
   • May have color vision deficits and optic disc swelling.
   • Visual loss progresses over hours to days, unlike the sudden onset of CRAO.
3. Vitreous Hemorrhage:
   • Causes sudden vision loss, often described as floaters or a red haze, but not complete black-out.
   • Common in patients with diabetic retinopathy or retinal tears.

 

Which of the following is the primary treatment for acute angle-closure glaucoma?
A- Timolol eye drops
B- Acetazolamide
C- Laser peripheral iridotomy
D- Pilocarpine eye drops

The primary treatment for acute angle-closure glaucoma is:

✅ Laser peripheral iridotomy

Explanation:
Acute angle-closure glaucoma is a medical emergency that occurs due to a sudden increase in intraocular pressure (IOP) caused by obstruction of aqueous humor outflow. The definitive treatment is laser peripheral iridotomy (LPI), which creates an opening in the peripheral iris to allow fluid drainage and prevent future attacks.

Role of Other Options:

• Timolol eye drops: A beta-blocker that reduces aqueous humor production but does not address the underlying anatomical issue.
• Acetazolamide: A carbonic anhydrase inhibitor that lowers IOP by reducing aqueous humor production; used as an adjunct, not the definitive treatment.
• Pilocarpine eye drops: A miotic agent that constricts the pupil and may help open the trabecular meshwork; used in acute settings but not the primary treatment.

 

1. What is the most common cause of nephrolithiasis?

A- Calcium oxalate stones
B- Uric acid stones
C- Struvite stones
D- Cystine stones

Correct Answer: Calcium oxalate stones
Explanation:
Nephrolithiasis (kidney stones) is a common condition characterized by the formation of crystalline stones in the urinary tract. Calcium oxalate stones are the most common type, accounting for approximately 70-80% of all kidney stones. These stones form due to supersaturation of calcium and oxalate in the urine, which leads to crystal formation.

Risk Factors for Calcium Oxalate Stones:

• Dehydration – Low urine volume increases the concentration of stone-forming minerals.
• High oxalate intake – Found in foods like spinach, nuts, and chocolate.
• Hypercalciuria – Increased calcium excretion in urine, often due to conditions like primary hyperparathyroidism.
• Low citrate levels – Citrate inhibits stone formation by binding calcium.
• Dietary habits – Excessive sodium and animal protein intake can contribute to stone formation.

Why Not the Other Options?

1. Uric Acid Stones (~10% of cases)
   
   • Associated with acidic urine (pH < 5.5), gout, and high purine intake.
   • Unlike calcium oxalate stones, uric acid stones are radiolucent (not visible on X-ray).
2. Struvite Stones (~10-15% of cases)
   
   • Also called infection stones, associated with urease-producing bacteria (e.g., Proteus, Klebsiella).
   • Can grow into large staghorn calculi and are composed of magnesium, ammonium, and phosphate.
3. Cystine Stones (<2% of cases)
   
   • Caused by cystinuria, a rare genetic disorder leading to excessive cystine excretion in urine.
   • Common in younger patients and form hexagonal crystals.

Thus, calcium oxalate stones are the most common cause of nephrolithiasis.

 

Which of the following is the most common type of esophageal cancer worldwide?

A- Adenocarcinoma
B- Squamous cell carcinoma
C- Small cell carcinoma
D- Large cell carcinoma

Correct Answer: Squamous Cell Carcinoma
Explanation:
Squamous cell carcinoma (SCC) is the most common type of esophageal cancer worldwide, particularly in regions such as Asia, Africa, and South America. It typically arises in the upper and middle parts of the esophagus and is strongly associated with risk factors like:

• Tobacco and alcohol use – These are the leading causes of SCC in Western countries.
• Dietary factors – Consumption of foods high in nitrosamines, hot beverages, and deficiencies in vitamins (e.g., vitamin A, C, and riboflavin) contribute to its prevalence.
• Chronic esophageal irritation – Conditions like achalasia, Plummer-Vinson syndrome, and caustic injuryincrease the risk.
• Human papillomavirus (HPV) infection – Some studies suggest a potential link between SCC and HPV infection.

In contrast, adenocarcinoma is more common in developed countries, particularly in North America and Western Europe, where it is associated with Barrett's esophagus and gastroesophageal reflux disease (GERD). Adenocarcinoma primarily affects the lower third of the esophagus and is linked to obesity and a high-fat diet.

Distribution:

• Squamous Cell Carcinoma: Most common worldwide, especially in Asia, Africa, and South America.
• Adenocarcinoma: More prevalent in Western countries, especially in Caucasian males.

Thus, squamous cell carcinoma remains the most common type of esophageal cancer globally despite the increasing incidence of adenocarcinoma in some regions.

 

What is the most common cause of superior vena cava syndrome?

A- Lung cancer
B- Thrombosis
C- Lymphoma
D- Mediastinal fibrosis

The most common cause of superior vena cava syndrome (SVCS) is lung cancer.

Explanation:

• The superior vena cava (SVC) is a large vein that carries blood from the upper body (head, neck, arms, and upper chest) back to the heart.
• SVCS occurs when the SVC is compressed or obstructed, leading to venous congestion in the upper body.

Why is lung cancer the most common cause?

• Lung cancer, particularly small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), is responsible for 60-85% of cases of SVCS.
• The SVC runs through the mediastinum, an area where lung tumors can grow and compress the vein.
• The right lung and mediastinal lymph nodes are in close proximity to the SVC, making them a common site for tumor invasion.

Other Causes of SVCS:

1. Thrombosis (15-20% of cases)
   
   • Caused by indwelling central venous catheters, pacemakers, or implantable defibrillators.
   • Can lead to SVC obstruction due to clot formation.
2. Lymphoma (5-10% of cases)
   
   • Hodgkin’s and Non-Hodgkin’s lymphoma can cause compression or invasion of the SVC.
3. Mediastinal Fibrosis (Rare)
   
   • Often due to chronic inflammation, such as from histoplasmosis or tuberculosis, leading to fibrotic constriction of the SVC.