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Infection, Pharmacology & VTE MCQs

Practice Set 23 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 441

Topic: Infection, Pharmacology & VTE

The mother of a 26-month-old boy reports that he has been unwilling to bear weight on his left lower extremity since he awoke this morning. She denies any history of trauma. He has a temperature of 99.4 degrees F (37.4 degrees C), and examination reveals that abduction of the left hip is limited to 30 degrees. Laboratory studies show a WBC of 11,000/mm3 and an erythrocyte sedimentation rate of 22 mm/h. A radiograph of the pelvis is shown in Figure 13. Management should consist of

Pediatrics 2001 Practice Questions: Set 1 (Solved) - Figure 23

. aspiration of the hip.
. a bone scan.
. an MRI scan.
. bed rest, frequent temperature checks, and reevaluation in 24 to 48 hours.
. hospital admission and placement in traction.

Correct Answer & Explanation

. bed rest, frequent temperature checks, and reevaluation in 24 to 48 hours.

Explanation

The most likely diagnosis is transient synovitis. Initial management should consist of bed rest and serial observation to rule out atypical septic arthritis of the hip. In an unreliable family situation, hospitalization for bed rest and observation may be indicated. Other disorders such as proximal femoral osteomyelitis, leukemia, juvenile rheumatoid arthritis, pelvic osteomyelitis, diskitis, and arthralgia secondary to other inflammatory disorders should be considered. However, these disorders are unlikely because of the paucity of abnormal clinical signs exhibited by the patient. On the other hand, transient synovitis of the hip in children is a diagnosis of exclusion; other possibilities should be explored if the patient's symptoms do not follow a typical course and resolve in 4 to 21 days.

Question 442

Topic: Infection, Pharmacology & VTE

An 11-year-old boy has had a fever and pain and swelling over the lateral aspect of his right ankle for the past 3 days. Examination reveals warmth, swelling, and tenderness over the lateral malleolus, and he has a temperature of 103.2 degrees F (39.5 degrees C). Laboratory studies show a WBC count of 13,200/mm3 with 61% neutrophils, an erythocyte sedimentation rate of 112 mm/h, and a C-reactive protein of 15.7. Radiographs and a T2-weighted MRI scan are shown in Figures 13a through 13c. Aspiration yields 1 mL of purulent fluid. Management should now consist of

. oral antibiotics and a follow-up office appointment the next day.
. incision and drainage of the distal fibular metaphysis.
. indium-labeled WBC scan.
. antituberculous medication for 6 months.
. three-phase technetium Tc 99m bone scan.

Correct Answer & Explanation

. incision and drainage of the distal fibular metaphysis.

Explanation

The initial signs and symptoms of acute hematogenous osteomyelitis vary widely but usually include fever, bone pain, and impaired use of the involved extremity. In lower extremity infections, the child may limp or refuse to walk. Examination often reveals bone tenderness. In more advanced cases, erythema, warmth, and swelling may be present. The WBC and neutrophil counts are not always elevated, but the erythocyte sedimentation rate will be abnormal in more than 90% of patients. When the infection is diagnosed early, before a subperiosteal abscess has formed, antibiotics alone may be adequate to treat the infection. This patient has a more advanced infection, however, with the MRI scan revealing a subperiosteal abscess that was confirmed by aspiration. When an abscess is present, surgical drainage is generally indicated to remove devitalized tissue and to enhance the efficacy of the antibiotics. Further studies, such as bone or indium scans, are not necessary and will delay definitive treatment. Scott RJ, Christofersen MR, Robertson WW Jr, et al: Acute osteomyelitis in children: A review of 116 cases. J Pediatr Orthop 1990;10:649-652.

Question 443

Topic: Infection, Pharmacology & VTE
Figure 33 shows the venogram of a patient who has a long history of alcohol abuse. Warfarin should be used cautiously because of the interaction with which of the following factors?
. II
. V
. VI
. VII
. VIII

Correct Answer & Explanation

. VII

Explanation

Warfarin acts by inhibiting clotting factors II, VII, IX, and X. The actual mechanism of action is by inhibition of hepatic enzymes, vitamin K epoxide, and perhaps vitamin K reductase. This inhibition results in lack of carboxylation of vitamin K-dependent proteins (II, VII, IX, X). The anticoagulant effect of warfarin can be reversed with vitamin K or fresh-frozen plasma. The use of alcohol may lead to liver dysfunction and an even more limited margin of available factors.

Question 444

Topic: Infection, Pharmacology & VTE

A 7-year-old boy sustained an acute puncture wound of the foot after stepping barefoot on a piece of glass 1 day ago. His mother states that she is not sure if she got the piece of glass out; however, she reports that his immunizations are up-to-date. Examination reveals that the wound is slightly erythematous, less than 1 mm in length on the heel, and is not currently draining. What is the next most appropriate step im management?

Foot & Ankle 2006 Practice Questions: Set 1 (Solved) - Figure 4

. Antibiotic coverage for pseudomonas
. Tetanus booster
. Radiographs of the foot
. MRI to evaluate for possible abscess or osteomyelitis
. Surgical debridement of the wound

Correct Answer & Explanation

. Radiographs of the foot

Explanation

The child has an up-to-date tetanus; therefore, a booster is not recommended. Pseudomonas coverage is most likely not needed because the child was barefoot. It is too early to evaluate for abscess or osteomyelitis with MRI, and a formal debridement is rarely indicated without signs of an abscess or a retained foreign body. Radiographs with soft-tissue penetration should be obtained to check for a retained foreign body. Richardson EG (ed): Orthopaedic Knowledge Update: Foot and Ankle 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 199-205.

Question 445

Topic: Infection, Pharmacology & VTE
A 30-year-old patient has had severe left hip pain and difficulty ambulating, necessitating the use of a cane, for the past 6 months. A photomicrograph of the femoral head sectioned at the time of surgery is shown in Figure 31. What is the most likely diagnosis?
. Renal osteodystrophy
. Pyogenic osteomyelitis
. Osteoarthritis
. Osteonecrosis
. Tuberculosis osteomyelitis

Correct Answer & Explanation

. Osteonecrosis

Explanation

The photomicrograph demonstrates a wedge-shaped infarct with femoral head collapse; therefore, the diagnosis is osteonecrosis of the femoral head. Perthes disease and osteoarthritis do not involve a wedge-shaped defect. Tuberculosis of the hip joint results in greater destruction of the articular cartilage.

Question 446

Topic: Infection, Pharmacology & VTE

A 6-year-old boy with acute hematogenous osteomyelitis of the distal femur is being treated with intravenous antibiotics. The most expeditious method to determine the early success or failure of treatment is by serial evaluations of which of the following studies?

Pediatrics Board Review 2007: High-Yield MCQs (Set 2) - Figure 12

. CBC count with differential
. MRI
. CT
. Radiographs
. C-reactive protein (CRP)

Correct Answer & Explanation

. C-reactive protein (CRP)

Explanation

Successful antibiotic treatment of osteomyelitis should lead to a rapid decline in the CRP. The CRP should decline after 48 to 72 hours of appropriate treatment. Imaging studies will take much longer to show resolution of bone infection. Unkila-Kallio L, Kallio MJ, Eskola J, et al: Serum C-reactive protein, erythrocyte sedimentation rate, and white blood cell count in acute hematogenous osteomyelitis of children. Pediatrics 1994;93:59-62.

Question 447

Topic: Infection, Pharmacology & VTE

A 45-year-old man who has had recurrent pain and swelling of the left Achilles tendon insertion for the past 10 years reports that physical therapy and activity modification have provided relief in the past. He now has continued pain despite these efforts. He also reports occasional bouts of dysuria that he attributes to a history of prostatitis. He also notes recent eye irritation that he attributes to allergies. A lateral heel radiograph is shown in Figure 33. Which of the following laboratory studies would best aid in diagnosis?

Foot & Ankle 2006 Practice Questions: Set 3 (Solved) - Figure 18

. Glucose tolerance test
. CBC count with differential
. Urethral swab and culture
. HLA-B27
. Antiphospholipid antibody

Correct Answer & Explanation

. HLA-B27

Explanation

Reiter's syndrome is a seronegative spondyloarthropathy characterized most commonly by a triad of asymmetric arthritis, urethritis, and uveitis. Tendon ensethopathies can also be present. It is most often seen in men and is associated with a positive HLA-B27 marker. Rheumatoid arthritis does not usually present with these features; more commonly it causes forefoot pain and synovitis of the metatarsophalangeal joints. A CBC count with differential would be helpful in a situation of possible infection. The urethral swab would help to diagnose a gonococcal infection which can cause a monoarticular septic arthritis. Antiphospholipid antibody is associated with a hypercoaguable state and increased risk of deep venous thrombosis.

Question 448

Topic: Infection, Pharmacology & VTE

What is the typical MRI signal intensity of bone marrow affected by acute osteomyelitis?

Anatomy 2005 Practice Questions: Set 1 (Solved) - Figure 26

. Decreased on T1-weighted imaging, increased on T1-weighted imaging with gadolinium enhancement, increased on T2-weighted imaging
. Decreased on T1-weighted imaging, increased on T1-weighted imaging with gadolinium enhancement, decreased on T2-weighted imaging
. Increased on T1-weighted imaging, increased on T1-weighted imaging with gadolinium enhancement, increased on T2-weighted imaging
. Increased on T1-weighted imaging, increased on T1-weighted imaging with gadolinium enhancement, decreased on T2-weighted imaging
. Increased on T1-weighted imaging, decreased on T1-weighted imaging with gadolinium enhancement, decreased on T2-weighted imaging

Correct Answer & Explanation

. Decreased on T1-weighted imaging, increased on T1-weighted imaging with gadolinium enhancement, decreased on T2-weighted imaging

Explanation

The classic MRI findings of osteomyelitis are a decrease in the normally high signal intensity of marrow on T1-weighted images and normal or increased signal intensity on T2-weighted images. This is the result of replacement of marrow fat by inflammatory cells and edema, which causes lower signal intensity than fat on T1-weighted images and higher signal intensity than fat on T2-weighted images. The addition of gadolinium to a T1-weighted sequence reveals increased signal intensity in the hyperemic marrow. Unger E, Moldofsky P, Gatenby R, et al: Diagnosis of osteomyelitis by MR imaging. Am J Roentgenol 1988;150:605-610. Dormans JP, Drummond DS: Pediatric hematogenous osteomyelitis: New trends in presentation, diagnosis and treatment. J Am Acad Orthop Surg 1994;2:333-341.

Question 449

Topic: Infection, Pharmacology & VTE

A 52-year-old woman reports mild pain localized to the left sternoclavicular joint. History is notable for chronic renal failure requiring dialysis for the last 5 years. A clinical photograph, chest radiograph, and bone scan are shown in Figures 58a through 58c. What is the most likely diagnosis?

. Pseudogout
. Spontaneous subluxation
. Postmenopausal arthritis
. Chronic osteomyelitis
. Friedreich's disease

Correct Answer & Explanation

. Chronic osteomyelitis

Explanation

Spontaneous swelling with the appearance of joint subluxation may be associated with an acute, subacute, or chronic bacterial infection of the sternoclavicular joint. Common causes of infection include bacteremia, rheumatoid arthritis, alcoholism, intravenous drug use, and chronic debilitating diseases. Subclavian vein catheterization and renal dialysis can predispose patients to sepsis and osteomyelitis of the sternoclavicular joint. Renoult B, Lataste A, Jonon B, et al: Sternoclavicular joint infection in hemodialysis patients. Nephron 1990;56:212-213.

Question 450

Topic: Infection, Pharmacology & VTE

A 5-year-old girl has had a low-grade fever, right hip and buttock pain, and a right-sided limp for the past 5 days. Examination shows diffuse tenderness and extreme pain on range of motion of the hip. Laboratory studies show a peripheral WBC count of 13,500/mm3 and an erythrocyte sedimentation rate of 55 mm/h. A radiograph is shown in Figure 46a, and an axial postgadolinium T1-weighted MRI scan with fat suppression and an axial T2-weighted fast spin echo MRI scan are shown in Figures 46b and 46c. What is the most likely diagnosis?

. Soft-tissue abscess of the gluteii
. Septic hip
. Pelvic fracture
. Acute osteomyelitis of the pelvis
. Eosinophilic granuloma of the pelvis

Correct Answer & Explanation

. Acute osteomyelitis of the pelvis

Explanation

MRI findings of acute osteomyelitis include a decrease in the normally high signal intensity of bone marrow on T1-weighted imaging; however, a postgadolinium T1-weighted image with fat suppression will show osteomyelitis as a bright marrow signal compared to the surrounding fat. Osteomyelitis is also brighter than normal fat on T2-weighted imaging. There is no rim-enhancing lesion suggesting an abscess, although myositis is seen in the obturator internus and short external rotators. The clinical scenario and imaging studies do not support the diagnosis of septic hip, eosinophilic granuloma, or pelvic fracture. Dormans JP, Drummond DS: Pediatric hematogenous osteomyelitis: New trends in presentation, diagnosis and treatment. J Am Acad Orthop Surg 1994;2:333-341.

Question 451

Topic: Infection, Pharmacology & VTE

A 10-year-old boy who has had progressive low back and right buttock pain for the past 3 days is now unable to bear weight on the right side secondary to pain. He has a temperature of 101.3 degrees F (38.5 degrees C). Examination reveals full hip range of motion; but he reports pain on the right side with external rotation. Pain is elicited with compression of the iliac wings and with direct palpation of the right sacroiliac (SI) joint. An MRI scan of the pelvis shows no abscess, but there is inflammation of the SI joint. Management should consist of

. nonsteroidal anti-inflammatory drugs.
. bed rest.
. bed rest, blood cultures, and IV antibiotics.
. right SI joint aspiration.
. right SI joint fusion.

Correct Answer & Explanation

. bed rest, blood cultures, and IV antibiotics.

Explanation

The clinical presentation and MRI findings are consistent with an acute infection of the SI joint. Bed rest and nonsteroidal anti-inflammatory drugs alone are insufficient to treat the problem. Staphylococcus aureus is the causative organism in most of these infections; therefore, unless there is an unusual factor in the history such as IV drug use, immune system compromise, or unusual travel, SI joint aspiration is unnecessary. It is often difficult to enter the SI joint, even under radiographic guidance. Management should consist of hospital admission and IV antibiotics. Blood cultures may be positive and should be obtained prior to starting antibiotics. Surgical fusion of the SI joint is not indicated. Morrissey RT: Bone and Joint Sepsis in Pediatric Orthopaedics. Philadelphia, PA, JB Lippincott, 1990. Beaupre A, Carroll N: The three syndromes of iliac osteomyelitis in children. J Bone Joint Surg Am 1979;61:1087-1092.

Question 452

Topic: Infection, Pharmacology & VTE

A 24-year-old man who works at a local oyster and clam farm sustained a laceration on his hand at work. Examination reveals a cellulitic index finger without evidence of tenosynovitis. After appropriate irrigation and debridement, what antibiotic is most appropriate?

. Amoxicillin
. Vancomycin
. Clindamycin
. Ceftazadime
. Cefazolin

Correct Answer & Explanation

. Ceftazadime

Explanation

Injuries involving brackish water and shellfish can have devastating consequences caused by Vibrio vulnificus infections. Patients may have a severe invasive infection, with three main clinical features: primary septicemia, wound infection, and gastroenteritis. Antibiotic administration is crucial because mortality rates of up to 50% have been observed with Vibrio septicemia. The current recommendation is to give a third-generation cephalosporin such as ceftazadime. Chiang SR, Chuang YC: Vibrio vulnificus infection: Clinical manifestations, pathogenesis, and antimicrobial therapy. J Microbiol Immunol Infect 2003;36:81-88.

Question 453

Topic: Infection, Pharmacology & VTE

A 3-year-old girl has had wrist pain, a fever, and has refused to move her right wrist for the past 10 days. She has an oral temperature of 102 degrees F (38.7 degree C). Laboratory studies show an erythrocyte sedimentation rate of 50 mm/h, a WBC count of 11,000/mm3, and a left shift. AP and lateral radiographs are shown in Figures 57a and 57b. What is the most likely diagnosis?

. Leukemia
. Eosinophilic granuloma
. Acute osteomyelitis
. Ewing's sarcoma
. Nonossifying fibroma

Correct Answer & Explanation

. Acute osteomyelitis

Explanation

The most likely diagnosis is acute osteomyelitis. She may also have a septic wrist; however, the lytic lesion in the distal radius has the typical presentation and radiographic appearance of metaphyseal osteomyelitis. In this area of sluggish vascular flow, low oxygen tension, and low pH, bacterial seeding is common and is the usual origin of metaphyseal osteomyelitis. Leukemia and Ewing's sarcoma can present as a lytic lesion with an elevated erythrocyte sedimentation rate, but they are much less common than osteomyelitis and are less focal and more destructive in appearance. Nonossifying fibroma is typically metaphyseal and eccentric; however, it is well circumscribed and uncommon in the upper extremity. Eosinophilic granuloma does not typically present with inflammatory indicies. Dormans JP, Drummond DS: Pediatric hematogenous osteomyelitis: New trends in presentation, diagnosis and treatment. J Am Acad Orthop Surg 1994;2:333-341.

Question 454

Topic: Infection, Pharmacology & VTE
Rivaroxaban is a medication commonly prescribed for deep vein thrombosis prophylaxis following total joint arthroplasty. What is its specific mechanism of action in the coagulation cascade?
. Inhibits antithrombin III
. Direct thrombin (Factor IIa) inhibitor
. Direct Factor Xa inhibitor
. Vitamin K epoxide reductase inhibitor
. Enhances tissue plasminogen activator

Correct Answer & Explanation

. Direct Factor Xa inhibitor

Explanation

Rivaroxaban and Apixaban are Direct Oral Anticoagulants (DOACs) that specifically and reversibly inhibit Factor Xa. Dabigatran is a direct thrombin (Factor IIa) inhibitor. Warfarin acts by inhibiting vitamin K epoxide reductase.

Question 455

Topic: Infection, Pharmacology & VTE

A 58-year-old male with long-standing poorly controlled type 2 diabetes presents with a unilaterally swollen, red, and warm foot without skin ulceration. Radiographs reveal fragmentation and subluxation at the tarsometatarsal joints. Which imaging modality is most sensitive and specific for differentiating acute Charcot neuroarthropathy from underlying osteomyelitis in this scenario?

. Technetium-99m bone scan
. Three-phase bone scan
. Gallium-67 scan
. Non-contrast MRI
. Indium-111 labeled leukocyte scan combined with Technetium-99m sulfur colloid marrow scan

Correct Answer & Explanation

. Indium-111 labeled leukocyte scan combined with Technetium-99m sulfur colloid marrow scan

Explanation

Differentiating Charcot arthropathy from osteomyelitis can be difficult, as both show increased uptake on a standard bone scan and marrow edema on MRI. The combination of an Indium-111 labeled leukocyte (WBC) scan and a Technetium-99m sulfur colloid marrow scan is the most highly specific test. In osteomyelitis, there is discordant uptake (increased WBC uptake, decreased sulfur colloid uptake due to marrow replacement by infection). In Charcot arthropathy, there is concordant uptake.

Question 456

Topic: Infection, Pharmacology & VTE

A 72-year-old male is scheduled for an elective total hip arthroplasty. He has a history of non-valvular atrial fibrillation and is currently taking Rivaroxaban. To minimize bleeding risk while avoiding prolonged periods without protection, pharmacokinetic guidelines suggest normal-renal-function patients should stop a direct oral anticoagulant (DOAC) approximately how many half-lives before major surgery?

. 1 half-life
. 2-3 half-lives
. 4-5 half-lives
. 7-10 half-lives
. 14 half-lives

Correct Answer & Explanation

. 4-5 half-lives

Explanation

Pharmacokinetically, a drug is considered to have undergone near-complete clinical elimination (approx 94-97% cleared) after 4 to 5 half-lives. For direct oral anticoagulants (DOACs) like Rivaroxaban or Apixaban in a patient with normal renal function, current perioperative guidelines recommend stopping the drug 48 to 72 hours prior to procedures with a high risk of bleeding, which corresponds to roughly 4-5 half-lives.

Question 457

Topic: Infection, Pharmacology & VTE
A 55-year-old male with long-standing, poorly controlled type 2 diabetes presents with a red, hot, swollen right foot. He denies any recent trauma, fevers, or systemic illness. Laboratory studies reveal a normal white blood cell count, ESR of 25 mm/h, and CRP of 1.0 mg/L. Radiographs demonstrate soft tissue swelling, profound joint subluxation at the tarsometatarsal joints, and bony fragmentation without focal osteopenia. What is the most appropriate initial treatment?
. Intravenous antibiotics and surgical debridement
. Oral antibiotics and non-weight bearing
. Immediate open reduction and internal fixation of the midfoot
. Total contact casting and strict non-weight bearing
. Primary below-knee amputation

Correct Answer & Explanation

. Total contact casting and strict non-weight bearing

Explanation

This patient presents with Stage I (Developmental/Fragmentation phase) Charcot arthropathy, characterized by a red, hot, swollen foot, joint laxity, and radiographic fragmentation and debris. Normal inflammatory markers and lack of systemic signs help distinguish this from acute osteomyelitis or septic arthritis. The gold standard initial treatment for an acute Charcot neuroarthropathy is immobilization and offloading, typically achieved via a total contact cast, until the active inflammatory phase subsides and the bones begin to consolidate (Stage II/III).

Question 458

Topic: Infection, Pharmacology & VTE

A 40-year-old male presents with an acutely swollen and painful knee. Arthrocentesis yields cloudy yellow fluid. Fluid analysis reveals a white blood cell count of 65,000 cells/ยตL with 85% polymorphonuclear leukocytes (PMNs). Gram stain is negative. Which of the following is the most likely diagnosis?

. Osteoarthritis
. Traumatic hemarthrosis
. Septic arthritis
. Lyme arthritis
. Gout

Correct Answer & Explanation

. Septic arthritis

Explanation

Synovial fluid analysis is critical for distinguishing joint pathologies. Fluid with >50,000 WBC/ยตL and >75% PMNs is highly suspicious for septic arthritis. Although crystalline arthropathies (gout, pseudogout) and severe inflammatory arthropathies can occasionally produce counts this high, septic arthritis must be the presumed diagnosis until proven otherwise. Note: Lyme arthritis can also present with very high WBC counts (averaging 60,000 cells/ยตL), but septic arthritis remains the most urgent and likely diagnosis in an acutely swollen, hot joint without a specific tick exposure history.

Question 459

Topic: Infection, Pharmacology & VTE

A 55-year-old male with poorly controlled diabetes mellitus presents with a swollen, erythematous, and painless left foot.

Radiographs show fragmentation and subluxation of the midfoot. To differentiate between acute Charcot arthropathy and superimposed osteomyelitis, an MRI is obtained. Which of the following MRI findings is highly specific for osteomyelitis in this setting?

. Diffuse bone marrow edema
. Significant joint effusion
. Subchondral cysts
. Presence of a sinus tract or the 'ghost sign'
. Periarticular soft tissue edema

Correct Answer & Explanation

. Presence of a sinus tract or the 'ghost sign'

Explanation

Differentiating Charcot arthropathy from osteomyelitis on MRI can be challenging as both present with marrow edema. However, finding a sinus tract extending from a skin ulcer to the bone, or the 'ghost sign' (disappearance of a bone on T1-weighted images that reappears on T2 or post-contrast images), is highly specific for osteomyelitis.

Question 460

Topic: Infection, Pharmacology & VTE

When utilizing a posteromedial approach to the proximal tibia for the fixation of a complex tibial plateau fracture, the surgical interval is developed between which of the following structures?

. Medial head of the gastrocnemius and the soleus
. Semimembranosus and the medial collateral ligament
. Medial head of the gastrocnemius and the pes anserinus
. Tibialis posterior and the flexor digitorum longus
. Tibialis anterior and the medial tibial crest

Correct Answer & Explanation

. Medial head of the gastrocnemius and the pes anserinus

Explanation

The posteromedial approach to the proximal tibia involves an internervous interval (though practically an intermuscular interval) between the medial head of the gastrocnemius (innervated by the tibial nerve) posteriorly and the pes anserinus (sartorius, gracilis, semitendinosus) anteriorly. Retracting the pes anteriorly and the medial gastrocnemius posteriorly protects the neurovascular bundle and provides excellent exposure to posteromedial tibial plateau fragments.

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