Free USMLE Step 2 CK Surgery practice questions

This man meets the clinical criteria for staphylococcal toxic shock syndrome: fever of at least 38.9 C, hypotension, diffuse macular erythroderma, and involvement of 3 or more organ systems (gastrointestinal, mucosal hyperemia, central nervous system, renal, hematologic and muscle). Nasal packing is a classic nonmenstrual source: S. aureus colonizing the retained foreign body produces the superantigen TSST-1, which nonspecifically activates a large fraction of T cells and triggers a cytokine storm with capillary leak. The local site often looks bland, and blood cultures are usually negative. As with a retained tampon, the single most important intervention after resuscitation is source control: remove the packing immediately, which stops ongoing toxin production at its origin. Aggressive fluids, norepinephrine for refractory hypotension, broad empiric antibiotics, and clindamycin (or linezolid) to inhibit toxin synthesis complete the core management.

B is wrong because imaging should not delay removal of an obvious foreign body source; CT is considered later only if a sinus or deep collection is suspected. C is wrong because IVIG may be considered as an adjunct in severe or refractory toxic shock, especially streptococcal TSS, but it never takes priority over source control. D is wrong because glucocorticoids have no proven benefit in TSS and are not part of standard therapy. E is wrong because any packing left in the nose, impregnated or not, remains a nidus for toxin-producing staphylococci; the packing must be removed, not replaced.

This patient has neurogenic shock from a cervical spinal cord injury. Weakness and loss of sensation in the hands and legs, absent rectal tone and shallow breathing point to a high cervical lesion. Injury above about T6 interrupts sympathetic outflow from the thoracolumbar cord, so arterial and venous tone fall and SVR drops. The cardiac accelerator fibers (T1 to T4) are also lost, leaving vagal tone unopposed. The result is the signature combination of hypotension with bradycardia and warm, dry, well-perfused skin, rather than the tachycardia and cold, clammy skin of hemorrhage.

Neurogenic shock remains a diagnosis of exclusion in trauma, because a cord injury does not protect against concurrent bleeding. Here the search is complete: no external hemorrhage, a negative FAST, a stable pelvis and clean chest and pelvic films. Treatment is fluids, then a vasopressor with alpha and beta activity such as norepinephrine to keep the MAP in the target range, and atropine or pacing for symptomatic bradycardia, while the spine is immobilized.

B. Hemorrhagic shock would produce tachycardia, a narrow pulse pressure and cool, vasoconstricted skin, and the evaluation found no source of bleeding. C. Spinal shock is the temporary loss of reflexes and flaccid paralysis below the level of injury; it explains the areflexia but is a neurologic, not a hemodynamic, term and does not itself mean hypotension. D. Cardiac tamponade causes obstructive shock with jugular venous distention, tachycardia and a pericardial effusion on FAST. E. Tension pneumothorax would cause unilateral absent breath sounds, tachycardia and distended neck veins, and the chest film is normal.

A slowly growing, painless, mobile parotid mass with intact facial nerve function in a middle-aged woman, with FNA showing epithelial and myoepithelial cells in chondromyxoid stroma, is a pleomorphic adenoma, the most common salivary gland tumor. It is benign, but it should be removed because it keeps growing and carries a small long-term risk of malignant transformation (carcinoma ex pleomorphic adenoma). The tumor has an incomplete capsule with fingerlike projections (pseudopodia) that extend beyond it, so simple shelling out leaves tumor behind and leads to multifocal recurrence. The standard operation for a tumor in the superficial lobe is superficial (or partial) parotidectomy with a cuff of normal tissue and identification and preservation of the facial nerve, which lies between the superficial and deep lobes.

A. Enucleation, by any approach, has a high recurrence rate because the capsular projections are left behind, and recurrent disease is multinodular and harder to cure. C. External beam radiation therapy is used as adjuvant treatment for salivary malignancies or recurrent disease, not as primary treatment of a benign, resectable tumor. D. Total parotidectomy with facial nerve sacrifice is reserved for malignant tumors that directly involve the nerve; sacrificing a functioning nerve for a benign tumor causes needless facial paralysis. E. Observation allows continued growth, makes later surgery more difficult, and accepts the risk of malignant change in a healthy young patient.

A well-encapsulated, homogeneous anterior mediastinal mass in a 51-year-old with normal germ cell tumor markers and no lymphadenopathy or B symptoms has the typical appearance of a thymoma. When imaging shows a resectable, encapsulated tumor, the standard of care is complete surgical resection: total thymectomy with en bloc removal of the mass (by sternotomy or a minimally invasive approach in experienced hands). Preoperative needle biopsy is avoided because breaching the capsule can seed the pleura or the needle tract, and a small core often cannot reliably distinguish thymoma subtypes anyway; the resected specimen provides the diagnosis and stage. Acetylcholine receptor antibodies were appropriately checked first so that occult myasthenia could be controlled before anesthesia, preventing a postoperative myasthenic crisis. Radiation is added afterward only for invasive or incompletely resected tumors.

A. Core needle biopsy is reserved for masses that appear unresectable or atypical (to plan induction therapy) or when lymphoma or germ cell tumor is suspected. B. Surveillance is not appropriate for a solid 4 cm thymic mass, because thymomas are malignant neoplasms with a potential for local invasion and pleural spread. C. Definitive radiation is used for patients who cannot undergo surgery or as adjuvant therapy, not as primary treatment of a resectable tumor. D. Neoadjuvant chemotherapy is considered for locally advanced, unresectable thymic tumors, not for a small encapsulated one.

This is an infected clenched-fist injury (fight bite). When a fist strikes teeth, oral flora are driven through a small laceration into the metacarpophalangeal joint capsule and extensor tendon sheath; when the fingers extend, the tendon slides back and seals the inoculum inside. The result is septic arthritis, extensor tenosynovitis or osteomyelitis, often with a misleadingly small wound and a delayed, evasive history. Management is radiography, surgical exploration and irrigation, and antibiotics.

The organisms are mixed: Eikenella corrodens, viridans streptococci, Staphylococcus aureus and oral anaerobes (Prevotella, Fusobacterium). Intravenous ampicillin-sulbactam covers all of them, including beta-lactamase-producing anaerobes and staphylococci, and is the standard regimen for an established human-bite infection. Uninfected fight bites receive oral amoxicillin-clavulanate prophylaxis. If the patient has risk factors for MRSA, vancomycin can be added, but it is not a substitute for ampicillin-sulbactam.

B. Clindamycin covers staphylococci, streptococci and anaerobes, but Eikenella corrodens is intrinsically resistant to clindamycin, so clindamycin alone is a classic error after human bites. C. Cefazolin covers staphylococci and streptococci but has unreliable activity against Eikenella and oral anaerobes. D. Vancomycin alone covers gram-positive organisms, including MRSA, but misses Eikenella and gram-negative anaerobes. E. Metronidazole covers anaerobes only; Eikenella is resistant to it, and it does not treat staphylococci or streptococci.

This woman has hidradenitis suppurativa (HS): recurrent painful nodules and abscesses in the axillae and groins, double-ended comedones, rope-like scars and sterile cultures, with obesity and smoking as risk factors. The right axilla now has an established sinus tract (tunnel) with two openings in a region of otherwise separated lesions, which is Hurley stage II disease.

HS begins with follicular occlusion and rupture, and the inflammation burrows into epithelialized tunnels. Incision and drainage opens only the acute collection and leaves the epithelialized tract behind, so the lesion recurs in the same spot, exactly what has happened four times here. The procedure of choice for a recurrent, localized tract is deroofing: under local anesthesia, a probe is passed through the tunnel, its roof is removed, the gelatinous base is curetted, and the wound heals by secondary intention with low recurrence and good cosmetic and functional results. Medical therapy (topical clindamycin, oral tetracyclines, or a biologic if refractory) continues alongside to limit new lesions, and smoking cessation and weight loss help control disease activity.

A. Repeat incision and drainage gives short-term relief of a fluctuant abscess, but this lesion is a chronic tract without fluctuance, and drainage would again leave the tunnel behind. B. Wide excision of the whole axilla with grafting or flap closure is reserved for diffuse, interconnected Hurley III disease; it is excessive for a single tract. C. Intralesional triamcinolone rapidly settles a single acutely inflamed nodule but does not remove an established epithelialized tunnel. E. Laser hair removal may reduce new follicular lesions in mild disease but does not treat an existing sinus tract.

The timing of postoperative fever usually narrows the cause, and fever within the first 24 hours is most often benign or related to the operation itself. A very early fever with pain out of proportion, systemic toxicity (tachycardia, hypotension), tense dusky or bronze skin, edema beyond the erythema, gray dishwater drainage, and crepitus, however, is a necrotizing soft tissue infection of the wound. Clostridium perfringens (gas gangrene, especially after bowel surgery) and group A Streptococcus cause rapidly progressive infections that can declare within hours of surgery; polymicrobial infections are also common, and diabetes is a major risk factor. Hyponatremia, leukocytosis above 15,000/mm3, and rising creatinine are typical laboratory clues. This is a surgical emergency: resuscitation, broad-spectrum antibiotics including clindamycin for toxin suppression, and emergent operative debridement, with repeat debridement as needed.

A is wrong because atelectasis does not cause wound findings, crepitus, or septic shock, and current evidence suggests it is not itself a cause of fever. B is wrong because an ordinary incisional infection presents around days 5 to 7 with erythema and purulent drainage, not within 24 hours with crepitus and shock. C is wrong because anastomotic leak typically declares on days 5 to 7 with peritonitis, and his abdomen is soft. D is wrong because malignant hyperthermia requires a volatile anesthetic or succinylcholine and presents intraoperatively or soon after with rising end-tidal CO2 and rigidity, not with wound necrosis.

The Ottawa ankle and foot rules are highly sensitive decision rules that tell which acutely injured ankles and feet need radiographs. They have two parts. Ankle films are needed for bony tenderness at the posterior edge or tip of the distal 6 cm of either malleolus, or inability to bear weight for 4 steps both immediately and in the ED. Foot films are needed for bony tenderness at the base of the fifth metatarsal or the navicular, or the same inability to bear weight. This patient walked more than 4 steps and has no malleolar bony tenderness, so the ankle portion is negative; her ATFL tenderness is ligamentous. However, she has point tenderness at the base of the fifth metatarsal, which is a positive foot rule. Inversion is the classic mechanism for an avulsion fracture of the fifth metatarsal base (pulled off by the peroneus brevis and lateral plantar aponeurosis) or a Jones fracture at the metaphyseal-diaphyseal junction, which has a high nonunion risk and different management. Foot radiographs (AP, lateral, and oblique) are therefore indicated.

A. Skipping imaging with RICE is correct only when every Ottawa criterion is negative; the fifth metatarsal tenderness makes this unsafe. B. Ankle films alone may not adequately show the fifth metatarsal base and are not indicated by her negative ankle examination. D. MRI is not a first-line study for acute ankle trauma; it is reserved for persistent symptoms suggesting osteochondral, syndesmotic, or occult injuries after initial radiographs. E. Ultrasound can show ligament tears, but ligament status does not change the initial treatment of a lateral sprain and it does not replace radiographs to exclude fracture.