A 57-year-old man presents to his family physician for a routine exam. He feels well and reports no new complaints since his visit last year. Last year, he had a colonoscopy which showed no polyps, a low dose chest computerized tomography (CT) scan that showed no masses, and routine labs which showed a fasting glucose of 93 mg/dL. He is relatively sedentary and has a body mass index (BMI) of 24 kg/m^2. He has a history of using methamphetamines, alcohol (4-5 drinks per day since age 30), and tobacco (1 pack per day since age 18), but he joined Alcoholics Anonymous and has been in recovery, not using any of these for the past 7 years. Which of the following is indicated at this time?

Chest computerized tomography (CT) scan

A 81-year-old man presents to his primary care physician with a 4-month history of shortness of breath. He says that he has slowly lost the ability to do things due to fatigue and now gets winded after walking around the house. He also says that his cough has been getting worse and seems to be producing more sputum. He has gained about 5 pounds over the last 6 months. His past medical history is significant for hypertension and diabetes. He has a 40 pack-year smoking history and drinks about 3 drinks per week. Physical exam reveals a cyanotic appearing man with 1+ edema in his legs bilaterally. He also has wheezing on lung auscultation with a prolonged expiratory phase. Which of the following would most likely be seen on a chest radiograph in this patient?

Hyperinflated lungs and loss of lung markings

Perihilar mass with unilateral hilar enlargement

Cardiomegaly and increased bronchial markings

Calcified pleural plaques surrounding the diaphragm

A previously healthy 66-year-old woman comes to the physician because of a 3-day history of fever, cough, and right-sided chest pain. Her temperature is 38.8°C (101.8°F) and respirations are 24/min. Physical examination shows dullness to percussion, increased tactile fremitus, and egophony in the right lower lung field. The remainder of the examination shows no abnormalities. Which of the following is the most likely cause of these findings?

Consolidation of a lung segment

Fluid in the interstitial space

An 8-year-old girl is brought to the physician by her parents for a 10-month history of disturbing dreams and daytime sleepiness. She has difficulty falling asleep and says she sometimes sees ghosts just before falling asleep at night. She has had a 7-kg (15-lb) weight gain during this period despite no changes in appetite. She is alert and oriented, and neurologic examination is unremarkable. During physical examination, she spontaneously collapses after the physician drops a heavy book, producing a loud noise. She remains conscious after the collapse. Polysomnography with electroencephalogram is most likely to show which of the following?

Decreased delta wave sleep duration

A 27-year-old man presents to the emergency department with back pain. The patient states that he has back pain that has been steadily worsening over the past month. He states that his pain is worse in the morning but feels better after he finishes at work for the day. He rates his current pain as a 7/10 and says that he feels short of breath. His temperature is 99.5°F (37.5°C), blood pressure is 130/85 mmHg, pulse is 80/min, respirations are 14/min, and oxygen saturation is 99% on room air. On physical exam, you note a young man who does not appear to be in any distress. Cardiac exam is within normal limits. Pulmonary exam is notable only for a minor decrease in air movement bilaterally at the lung bases. Musculoskeletal exam reveals a decrease in mobility of the back in all four directions. Which of the following is the best initial step in management of this patient?

Radiography of the lumbosacral spine

A 71-year-old man with type 2 diabetes mellitus comes to the physician because of a 9-month history of pain and stiffness in the right knee. He reports that the stiffness lasts approximately 10 minutes after waking up and that the pain is worse in the evening. There is no history of trauma. He is 175 cm (5 ft 9 in) tall and weighs 102 kg (225 lb); BMI is 33 kg/m2. Examination of the right knee shows tenderness in the anteromedial joint line and crepitus during knee movement. Laboratory studies show an erythrocyte sedimentation rate of 15 mm/h and a serum uric acid concentration of 6.9 mg/dL. Which of the following is the most likely finding on imaging of the right knee?

Osteophytes and narrowing of the joint-space

Loculated epiphyseal cyst with thinning of the overlying cortex

Bony ankylosis and bone proliferation at the entheses

Marginal bony erosions and opacification of periarticular soft tissue

Periarticular osteopenia and pannus formation

Common radiologic findings in pathology for USMLE Step 3: High-Yield Anatomy Lessons

Chest Imaging - See-Thru Stories

Chest X-ray: CHF findings (Kerley B lines, edema, effusion)

Air Crescent Sign: Invasive aspergillosis.
Bat Wing Alveolar Opacities: Pulmonary edema.
Kerley B Lines: Septal thickening from pulmonary edema (CHF).
Honeycomb Lung: Idiopathic pulmonary fibrosis (IPF).
Pleural Plaques (calcified): Asbestosis.
"Steeple" Sign (tracheal narrowing): Croup.
"Thumb" Sign (enlarged epiglottis): Epiglottitis.
Ghon Complex: Healed primary tuberculosis.

⭐ Silhouette Sign: Loss of the normal border between thoracic structures indicates the location of an abnormality. For example, loss of the right heart border implies right middle lobe pathology.

Abdominal Views - Gut Instincts

Pneumoperitoneum: Free air under the diaphragm on upright CXR. Indicates perforated viscus (e.g., ulcer).
- Signs: Rigler's sign (both sides of bowel wall visible), falciform ligament sign.
Small Bowel Obstruction (SBO): Dilated loops >3 cm.
- Features: Multiple air-fluid levels, valvulae conniventes (stack of coins).
Large Bowel Obstruction (LBO): Dilated colon >6 cm (cecum >9 cm).
- Features: Haustral markings (don't cross entire diameter).
Ileus: Generalized, uniform dilation of both large and small bowel; air in rectum.

⭐ Rigler's Sign: Also known as the double-wall sign, air on both sides of the bowel wall is a key indicator of pneumoperitoneum, suggesting a significant amount of free intraperitoneal air.

Abdominal X-ray: Rigler's sign in pneumoperitoneum

Neuro-Radiology - Brain Wave Pictures

Electroencephalogram (EEG): Measures brain's electrical activity. Key for seizures, sleep disorders, and encephalopathy.
Wave Frequencies (Fastest to Slowest): 📌 Bats Are Totally Dead
- Beta (>13 Hz): Awake, alert, active thinking.
- Alpha (8-13 Hz): Awake, relaxed, eyes closed. Disappears with eye opening.
- Theta (4-7 Hz): Drowsiness, light sleep.
- Delta (<4 Hz): Deep sleep. Pathologic in awake adults (encephalopathy).

EEG: 3 Hz Spike-and-Wave in Absence Seizure

Pathologic Patterns:
- Spike-and-wave: Epilepsy.
- Periodic sharp waves: Creutzfeldt-Jakob Disease (CJD).
- PLEDs: Herpes Simplex Encephalitis (HSE).

⭐ Absence Seizures: Characterized by generalized 3 Hz spike-and-wave discharges on EEG, often provoked by hyperventilation.

MSK Radiology - Bone-Deep Clues

Degenerative (Osteoarthritis): Asymmetric joint space narrowing, osteophytes, subchondral sclerosis.
Inflammatory (Rheumatoid Arthritis): Symmetric joint space narrowing, periarticular osteopenia, marginal erosions.
Metabolic (Gout): Punched-out "rat-bite" erosions with sclerotic, overhanging margins; soft tissue tophi.
Malignancy Patterns:
- Osteosarcoma: Sunburst pattern, Codman's triangle (periosteal elevation).
- Ewing Sarcoma: "Onion skin" (lamellated) periosteal reaction.
- Multiple Myeloma: "Punched-out" lytic lesions.

⭐ Avascular Necrosis (AVN): A crescent sign on an X-ray of the femoral head is an early indicator, representing a subchondral fracture.

High‑Yield Points - ⚡ Biggest Takeaways

Pneumothorax classically presents with the absence of lung markings peripheral to a visceral pleural line.

Look for Hampton's hump (wedge-shaped infarct) or Westermark sign (oligemia) in pulmonary embolism.

Small bowel obstruction shows dilated loops of bowel (>3 cm) with multiple air-fluid levels.

Acute cholecystitis signs include a thickened gallbladder wall (>3 mm) and pericholecystic fluid.

An enlarged appendix (>6 mm) with periappendiceal fat stranding suggests appendicitis on CT.

Early ischemic stroke may only show a subtle loss of grey-white matter differentiation.

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