Menu

Infection, Pharmacology & VTE MCQs

Practice Set 44 of 68

This practice set contains high-yield board review questions covering key concepts in Infection, Pharmacology & VTE. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 861

Topic: Infection, Pharmacology & VTE

A 55-year-old male presents with severe foot pain, erythema, swelling, and warmth, primarily affecting the first metatarsophalangeal (MTP) joint. He has a history of poorly controlled hypertension and kidney stones. Aspiration of the joint reveals negatively birefringent needle-shaped crystals. What is the most likely diagnosis?

. Septic arthritis.
. Pseudogout.
. Rheumatoid arthritis.
. Gout.
. Cellulitis.

Correct Answer & Explanation

. Gout.

Explanation

The clinical presentation (acute, severe pain, erythema, swelling of the first MTP joint - 'podagra'), patient history (hypertension, kidney stones, often associated with hyperuricemia), and synovial fluid analysis showing negatively birefringent needle-shaped crystals are pathognomonic for gout. Septic arthritis would show a high WBC count and positive cultures. Pseudogout (CPPD) shows positively birefringent rhomboid-shaped crystals. Rheumatoid arthritis is typically polyarticular and chronic. Cellulitis would not have crystals on aspiration.

Question 862

Topic: Infection, Pharmacology & VTE

Which of the following imaging modalities is most sensitive for detecting early osteomyelitis?

. Plain radiographs.
. CT scan.
. MRI.
. Bone scintigraphy (technetium-99m).
. Ultrasound.

Correct Answer & Explanation

. MRI.

Explanation

MRI is generally considered the most sensitive imaging modality for detecting early osteomyelitis, often demonstrating changes within 24-48 hours of infection onset. It provides excellent soft tissue contrast, allowing visualization of marrow edema, abscess formation, and soft tissue involvement. Plain radiographs may take 7-10 days to show changes. CT scans are good for bony detail but less sensitive for early marrow changes. Bone scintigraphy is sensitive but not very specific for infection versus other bone activity. Ultrasound can detect soft tissue abscesses but is not ideal for bone marrow changes.

Question 863

Topic: Infection, Pharmacology & VTE

A patient undergoing total hip arthroplasty for osteoarthritis is at highest risk for which of the following complications in the immediate postoperative period?

. Periprosthetic fracture.
. Avascular necrosis of the femoral head.
. Heterotopic ossification.
. Deep vein thrombosis (DVT) and pulmonary embolism (PE).
. Loosening of the prosthetic components.

Correct Answer & Explanation

. Deep vein thrombosis (DVT) and pulmonary embolism (PE).

Explanation

Patients undergoing major orthopedic surgery, especially total hip arthroplasty, are at highest risk for deep vein thrombosis (DVT) and subsequent pulmonary embolism (PE) in the immediate postoperative period. Prophylactic anticoagulation is standard to mitigate this risk. Periprosthetic fracture, avascular necrosis (of the patient's remaining bone, not a complication of the replaced head), heterotopic ossification, and loosening are also potential complications, but DVT/PE represents the most critical and life-threatening immediate postoperative risk requiring strict preventative protocols.

Question 864

Topic: Infection, Pharmacology & VTE

In the management of septic arthritis, what is the most critical initial step after diagnosis?

. Initiate broad-spectrum oral antibiotics.
. Immobilize the joint in a position of comfort.
. Perform emergent joint aspiration and start empiric IV antibiotics.
. Administer intra-articular corticosteroids.
. Schedule elective arthroscopy for debridement.

Correct Answer & Explanation

. Perform emergent joint aspiration and start empiric IV antibiotics.

Explanation

Septic arthritis is a joint emergency. The most critical initial step after suspicion is emergent joint aspiration to confirm the diagnosis (cell count, Gram stain, culture) and immediately initiate empiric intravenous antibiotics. Delay in treatment can lead to rapid cartilage destruction and long-term joint damage. Oral antibiotics are insufficient initially. Intra-articular corticosteroids are contraindicated. Immobilization provides comfort but doesn't treat the infection. Elective arthroscopy might be needed for drainage/debridement but only after aspiration and antibiotics are started.

Question 865

Topic: Infection, Pharmacology & VTE

A 70-year-old patient undergoing rehabilitation after proximal femur fracture fixation reports a new, exquisitely tender lump at the base of his prior appendectomy scar. He has no vomiting but feels nauseated and has increased pain with defecation. A small incisional hernia with Richter incarceration is suspected. Which post-operative risk is significantly amplified due to this acute abdominal pathology?

. Deep vein thrombosis (DVT)
. Non-union of the femur fracture
. Surgical site infection of the fracture site
. Delirium and prolonged hospital stay due to sepsis and emergency surgery
. Hardware failure at the fracture site

Correct Answer & Explanation

. Delirium and prolonged hospital stay due to sepsis and emergency surgery

Explanation

The most significantly amplified post-operative risk in this scenario is delirium and prolonged hospital stay due to sepsis and emergency surgery. An acute, strangulated Richter hernia necessitates emergency abdominal surgery, which is a major physiological stressor. For an elderly, already compromised patient with a recent orthopedic surgery, this significantly increases the risk of post-operative complications like delirium, pneumonia, cardiac events, and sepsis, leading to a much longer and more complex hospital course, often derailing rehabilitation. While DVT and fracture-related issues are risks, the acute abdominal emergency presents an immediate and severe systemic challenge amplifying overall morbidity.

Question 866

Topic: Infection, Pharmacology & VTE

A 55-year-old male presents with severe pain and swelling in his great toe metatarsophalangeal (MTP) joint. On examination, the joint is exquisitely tender, erythematous, and warm. Fluid aspiration reveals negatively birefringent, needle-shaped crystals. What is the most appropriate long-term management to prevent recurrent attacks?

. NSAIDs (e.g., ibuprofen)
. Colchicine
. Allopurinol
. Corticosteroids
. Low-purine diet only

Correct Answer & Explanation

. Allopurinol

Explanation

The patient presents with an acute attack of gout, confirmed by negatively birefringent, needle-shaped urate crystals. While NSAIDs, colchicine, and corticosteroids are used for acute symptom relief, allopurinol is the cornerstone of long-term management to prevent recurrent attacks by decreasing uric acid production. It is a xanthine oxidase inhibitor. NSAIDs, colchicine, and corticosteroids treat the acute inflammation but do not alter the underlying hyperuricemia. A low-purine diet is helpful but usually insufficient alone for long-term control.

Question 867

Topic: Infection, Pharmacology & VTE

A 4-year-old child presents with a high fever, refusal to bear weight, and exquisite pain on hip range of motion. Blood tests show elevated white blood cell count and C-reactive protein. What is the most urgent diagnostic and therapeutic step?

. Hip MRI
. Joint aspiration
. Antibiotics and observation
. Skeletal traction
. Blood cultures and NSAIDs

Correct Answer & Explanation

. Joint aspiration

Explanation

The symptoms are highly suggestive of septic arthritis of the hip, which is a surgical emergency. The most urgent diagnostic and therapeutic step is joint aspiration to confirm the diagnosis (cell count, Gram stain, culture) and guide antibiotic therapy. Following aspiration, empiric intravenous antibiotics should be started, and surgical debridement (arthrotomy or arthroscopy) is typically performed urgently to prevent articular cartilage destruction and long-term complications. MRI is useful for diagnosis but less immediate than aspiration. Antibiotics and observation alone are insufficient. Skeletal traction is not primary management. Blood cultures are important, but NSAIDs are not a definitive treatment for infection.

Question 868

Topic: Infection, Pharmacology & VTE

Which of the following is the most sensitive imaging modality for detecting early osteomyelitis?

. Plain radiographs
. CT scan
. MRI
. Bone scintigraphy (Tc-99m)
. Ultrasound

Correct Answer & Explanation

. MRI

Explanation

Magnetic Resonance Imaging (MRI) is the most sensitive imaging modality for detecting early osteomyelitis. It can identify bone marrow edema and inflammation even before changes are visible on plain radiographs or CT scans. Bone scintigraphy is also sensitive but less specific than MRI, especially in children or when differentiating from other inflammatory conditions. Plain radiographs show changes only after significant bone destruction (typically 10-14 days). CT is good for cortical bone detail but less sensitive for early marrow changes.

Question 869

Topic: Infection, Pharmacology & VTE

A patient undergoes a total knee arthroplasty (TKA). Postoperatively, they develop calf pain, swelling, and a positive Homan's sign. Duplex ultrasound confirms a deep vein thrombosis (DVT). What is the most appropriate initial management?

. Aspirin
. Placement of an inferior vena cava (IVC) filter
. Initiation of therapeutic anticoagulation (e.g., LMWH or direct oral anticoagulant)
. Warfarin only
. Compression stockings and observation

Correct Answer & Explanation

. Initiation of therapeutic anticoagulation (e.g., LMWH or direct oral anticoagulant)

Explanation

The most appropriate initial management for confirmed deep vein thrombosis (DVT) following TKA is the initiation of therapeutic anticoagulation. Low molecular weight heparin (LMWH) or direct oral anticoagulants (DOACs) are commonly used. An IVC filter is generally reserved for patients with contraindications to anticoagulation or recurrent pulmonary embolism despite adequate anticoagulation. Aspirin is used for prophylaxis but not treatment of established DVT. Warfarin requires a longer time to reach therapeutic levels, so it's usually started with a bridging agent. Compression stockings are adjunctive, not definitive treatment.

Question 870

Topic: Infection, Pharmacology & VTE

What is the most common cause of septic arthritis in adults?

. Staphylococcus epidermidis
. Streptococcus pneumoniae
. Escherichia coli
. Neisseria gonorrhoeae
. Staphylococcus aureus

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Staphylococcus aureus is by far the most common causative organism for septic arthritis in adults (and children). It accounts for 70-80% of cases. Staphylococcus epidermidis is common in prosthetic joint infections but less so in native joint septic arthritis. Neisseria gonorrhoeae is a common cause in young, sexually active individuals but not overall the most common. Streptococcus pneumoniae and E. coli are less frequent causes in general.

Question 871

Topic: Infection, Pharmacology & VTE

Which bone is most commonly affected by osteomyelitis in IV drug users?

. Femur
. Tibia
. Humerus
. Vertebral bodies
. Calcaneus

Correct Answer & Explanation

. Vertebral bodies

Explanation

Intravenous drug users (IVDU) are particularly susceptible to hematogenous osteomyelitis of the vertebral bodies, often caused by Staphylococcus aureus or Pseudomonas aeruginosa. This is due to direct inoculation of bacteria into the bloodstream and subsequent spread to the highly vascular vertebral bodies. While long bones can be affected, the spine is a notably common site in this population.

Question 872

Topic: Infection, Pharmacology & VTE

What is the primary concern for a patient with an unstable Colles fracture undergoing surgical fixation who is also on anticoagulant therapy (e.g., warfarin)?

. Increased risk of nonunion
. Higher chance of CRPS development
. Increased bleeding risk during and after surgery
. Difficulty in achieving adequate fracture reduction
. Increased risk of deep vein thrombosis (DVT)

Correct Answer & Explanation

. Increased bleeding risk during and after surgery

Explanation

The primary concern for a patient on anticoagulant therapy undergoing surgical fixation for a Colles fracture is an increased bleeding risk during and after surgery. This necessitates careful preoperative management to optimize coagulation status, often involving temporary cessation or bridging therapy, to minimize hematoma formation and blood loss. Anticoagulants do not directly affect fracture reduction or nonunion rates, nor are they a primary risk factor for CRPS or DVT (in fact, they reduce DVT risk).

Question 873

Topic: Infection, Pharmacology & VTE

Which of the following is the most common cause of osteomyelitis in healthy adults?

. Staphylococcus aureus
. Pseudomonas aeruginosa
. Salmonella species
. Mycobacterium tuberculosis
. Escherichia coli

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Staphylococcus aureus is by far the most common causative organism for osteomyelitis in both children and adults, regardless of the route of infection (hematogenous, contiguous, or direct inoculation). Pseudomonas is often seen in puncture wounds or intravenous drug users. Salmonella is associated with sickle cell disease. Mycobacterium tuberculosis causes Pott's disease (spinal tuberculosis) and other chronic forms of osteomyelitis. E. coli can cause osteomyelitis, especially in immunocompromised or elderly patients, but less frequently than S. aureus.

Question 874

Topic: Infection, Pharmacology & VTE

Which of the following imaging modalities is considered the most sensitive for detecting early signs of osteomyelitis in the appendicular skeleton?

. Plain radiographs
. CT scan
. MRI with contrast
. Technetium bone scan (Tc-99m)
. Gallium scan (Ga-67)

Correct Answer & Explanation

. MRI with contrast

Explanation

MRI with contrast is the most sensitive and specific imaging modality for detecting early signs of osteomyelitis, particularly marrow edema, inflammation, and abscess formation in the appendicular skeleton. It can detect changes within 3-5 days of infection. Plain radiographs are typically normal in the first 10-14 days. CT is good for cortical bone destruction and sequestrum but less sensitive for early soft tissue and marrow changes. Technetium bone scans are highly sensitive but less specific. Gallium scans are more specific for infection but have lower spatial resolution and are less commonly used as a first-line diagnostic tool than MRI.

Question 875

Topic: Infection, Pharmacology & VTE

A 65-year-old female presents with severe pain, swelling, and redness in her left great toe, acutely worsening over the past 24 hours. She has a history of hypertension and takes a diuretic. Synovial fluid aspiration shows negatively birefringent, needle-shaped crystals. What is the definitive long-term pharmacologic treatment to prevent future attacks?

. NSAIDs
. Colchicine
. Prednisone
. Allopurinol
. Probenecid

Correct Answer & Explanation

. Allopurinol

Explanation

The clinical picture and synovial fluid analysis (negatively birefringent, needle-shaped crystals) confirm a diagnosis of gout. While NSAIDs, colchicine, and prednisone are used to treat acute attacks, allopurinol is the definitive long-term pharmacologic treatment forpreventionof future attacks by decreasing uric acid production. Probenecid is also a uricosuric agent but acts differently. Allopurinol is typically initiated once the acute attack has resolved.

Question 876

Topic: Infection, Pharmacology & VTE

What is the most common pathogen responsible for septic arthritis in a healthy adult?

. Staphylococcus epidermidis
. Streptococcus pyogenes
. Neisseria gonorrhoeae
. Staphylococcus aureus
. Pseudomonas aeruginosa

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Staphylococcus aureus is by far the most common pathogen responsible for septic arthritis in healthy adults, as well as in children and those with prosthetic joints. While other bacteria can cause septic arthritis, S. aureus accounts for the majority of cases. Neisseria gonorrhoeae is common in young, sexually active individuals but less overall than S. aureus. S. epidermidis is common in prosthetic joint infections but less so in native joint septic arthritis.

Question 877

Topic: Infection, Pharmacology & VTE

Methicillin-resistant Staphylococcus aureus (MRSA) demonstrates resistance to standard beta-lactam antibiotics primarily through which of the following mechanisms?

. Production of an extended-spectrum beta-lactamase enzyme
. Upregulation of transmembrane efflux pumps to clear the antibiotic
. Alteration of penicillin-binding protein 2a (PBP2a) encoded by the mecA gene
. Mutation in the DNA gyrase target site
. Significant thickening of the peptidoglycan cell wall (glycocalyx)

Correct Answer & Explanation

. Alteration of penicillin-binding protein 2a (PBP2a) encoded by the mecA gene

Explanation

MRSA resistance is mediated by the mecA gene, which encodes for a novel penicillin-binding protein, PBP2a. This altered protein has a very low affinity for beta-lactam antibiotics (such as penicillins and cephalosporins), allowing the bacteria to synthesize its cell wall even in the presence of these drugs. DNA gyrase mutations relate to fluoroquinolone resistance.

Question 878

Topic: Infection, Pharmacology & VTE
An orthopaedic surgeon is evaluating a 70-year-old patient scheduled for an elective total hip arthroplasty. The patient is currently taking Rivaroxaban for non-valvular atrial fibrillation. What is the specific mechanism of action of this medication?
. Inhibits thrombin (Factor IIa) directly
. Potentiates Antithrombin III activity
. Inhibits the Vitamin K epoxide reductase complex
. Directly and reversibly inhibits Factor Xa
. Irreversibly blocks ADP (P2Y12) receptors on platelets

Correct Answer & Explanation

. Directly and reversibly inhibits Factor Xa

Explanation

Rivaroxaban (as well as Apixaban and Edoxaban) is a Direct Oral Anticoagulant (DOAC) that acts by directly and reversibly inhibiting Factor Xa, preventing the conversion of prothrombin to thrombin. Dabigatran is a direct thrombin (IIa) inhibitor. Warfarin inhibits Vitamin K epoxide reductase. LMWH and unfractionated heparin potentiate Antithrombin III. Clopidogrel blocks P2Y12 ADP receptors.

Question 879

Topic: Infection, Pharmacology & VTE

A 2-year-old child presents with an acute septic arthritis of the knee. The synovial fluid Gram stain is negative, but a targeted PCR panel is positive. Which of the following fastidious organisms is increasingly recognized as the most common cause of septic arthritis in children aged 6 months to 4 years?

. Staphylococcus aureus
. Haemophilus influenzae type B
. Kingella kingae
. Streptococcus pneumoniae
. Neisseria gonorrhoeae

Correct Answer & Explanation

. Kingella kingae

Explanation

Kingella kingae is a fastidious Gram-negative organism that has emerged as the most common cause of septic arthritis and osteomyelitis in children under 4 years old. It is difficult to isolate on traditional culture but is readily identified via nucleic acid amplification (PCR).

Question 880

Topic: Infection, Pharmacology & VTE

According to the Kocher criteria, which of the following is NOT one of the classic four predictors for distinguishing septic arthritis from transient synovitis in a pediatric hip?

. Non-weight-bearing on the affected side
. Erythrocyte sedimentation rate (ESR) > 40 mm/hr
. White blood cell (WBC) count > 12,000/mm^3
. Fever > 38.5 C
. C-reactive protein (CRP) > 2.0 mg/dL

Correct Answer & Explanation

. C-reactive protein (CRP) > 2.0 mg/dL

Explanation

The original Kocher criteria include non-weight-bearing, ESR > 40, WBC > 12,000, and fever > 38.5 C. While CRP is an excellent inflammatory marker used extensively today, it was not part of the original four parameters defined by Kocher.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page