A 47-year-old woman comes to the emergency department after coughing up 2 cups of bright red blood. A CT angiogram of the chest shows active extravasation from the right bronchial artery. A coil embolization is planned to stop the bleeding. During this procedure, a catheter is first inserted into the right femoral artery. Which of the following represents the correct subsequent order of the catheter route?

Thoracic aorta, right bronchial artery

Thoracic aorta, right superior epigastric artery, right bronchial artery

Thoracic aorta, left ventricle, left atrium, pulmonary artery, right bronchial artery

Thoracic aorta, brachiocephalic trunk, right subclavian artery, right internal thoracic artery, right bronchial artery

Thoracic aorta, right subclavian artery, right internal thoracic artery, right bronchial artery

A 62-year-old man comes to the physician because of a 5-day history of swelling in his left arm. Two months ago, he was diagnosed with a deep venous thrombosis in the left calf. He has had a 7-kg (15-lb) weight loss in the last 3 months. He has smoked 1 pack of cigarettes daily for the past 25 years. His only medication is warfarin. Physical examination shows warm edema of the left forearm with overlying erythema and a tender, palpable cord-like structure along the medial arm. His lungs are clear to auscultation bilaterally. Duplex sonography shows thrombosis of the left basilic and external jugular veins. Which of the following is the most appropriate next step to confirm the underlying diagnosis?

Transesophageal echocardiography

Serum antiphospholipid antibody level

A 67-year-old woman presents with right leg pain and swelling of 5 days’ duration. She has a history of hypertension for 15 years and had a recent hospitalization for pneumonia. She had been recuperating at home but on beginning to mobilize and walk, the right leg became painful and swollen. Her temperature is 37.1°C (98.7°F), the blood pressure is 130/80 mm Hg, and the pulse is 75/min. On physical examination, the right calf is 4 cm greater in circumference than the left when measured 10 cm below the tibial tuberosity. Dilated superficial veins are present on the right foot and the right leg is slightly redder than the left. There is some tenderness on palpation in the popliteal fossa behind the knee. Which of the following is the best initial step in the management of this patient’s condition?

Wells’ clinical probability tool

International normalized ratio (INR)

Computerized tomography (CT) with contrast

Activated partial thromboplastin time (aPTT)

On cardiology service rounds, your team sees a patient admitted with an acute congestive heart failure exacerbation. In congestive heart failure, decreased cardiac function leads to decreased renal perfusion, which eventually leads to excess volume retention. To test your knowledge of physiology, your attending asks you which segment of the nephron is responsible for the majority of water absorption. Which of the following is a correct pairing of the segment of the nephron that reabsorbs the majority of all filtered water with the means by which that segment absorbs water?

Proximal convoluted tubule via passive diffusion following ion reabsorption

Distal convoluted tubule via passive diffusion following ion reabsorption

Distal convoluted tubule via aquaporin channels

Thick ascending loop of Henle via passive diffusion following ion reabsorption

Collecting duct via aquaporin channels

A 43-year-old man presents with acute-onset left flank pain for the past 6 hours. He describes the pain as severe, intermittent, colicky, and “coming in waves”, and he points to the area of the left costovertebral angle (CVA). He says he recently has been restricting oral liquid intake to only 2 glasses of water per day based on the advice of his healer. He also reports nausea and vomiting. The patient has a history of hypertension, gout, and type 2 diabetes mellitus. He is afebrile, and his vital signs are within normal limits. On physical examination, he is writhing in pain and moaning. There is exquisite left CVA tenderness. A urinalysis shows gross hematuria. Which of the following is the next best step in the management of this patient?

Non-contrast CT of the abdomen and pelvis

Contrast CT of the abdomen and pelvis

A 55-year-old man comes to the emergency department because of left-sided chest pain and difficulty breathing for the past 30 minutes. His pulse is 88/min. He is pale and anxious. Serum studies show increased cardiac enzymes. An ECG shows ST-elevations in leads I, aVL, and V5-V6. A percutaneous coronary intervention is performed. In order to localize the site of the lesion, the catheter must pass through which of the following structures?

Left coronary artery → left circumflex artery

Right coronary artery → posterior descending artery

Left coronary artery → left anterior descending artery

Right coronary artery → right marginal artery

Left coronary artery → posterior descending artery

Angiography techniques for USMLE Step 1: High-Yield Anatomy Lessons

Angiography 101 - The Vessel Roadmap

Definition: An invasive diagnostic procedure using iodinated contrast and fluoroscopy (real-time X-ray) to visualize the lumen of blood vessels. Considered the gold standard for vessel mapping and intervention.
Core Principle (Seldinger Technique): The foundational method for safe, percutaneous vascular access. A needle punctures the vessel, a guidewire is passed through the needle, the needle is removed, and a catheter is fed over the wire.
Contrast Agents: Typically iodine-based solutions that are radiopaque (appear white on X-ray). ⚠️ Major risks include Contrast-Induced Nephropathy (CIN) and anaphylactoid reactions.
Common Access Sites:
- Common Femoral Artery (CFA): Traditional choice, large diameter, easy to access.
- Radial Artery: Increasingly preferred due to ↑ patient comfort post-procedure and significantly ↓ risk of bleeding complications.

Seldinger technique for arterial access

⭐ For patients with chronic kidney disease (CKD) or diabetes, the risk of Contrast-Induced Nephropathy (CIN) is significantly elevated. Pre-procedural IV hydration is the most effective preventative measure.

Technique & Access - Getting In

Core Method: Modified Seldinger Technique
- 1. Needle Access: Puncture the target vessel with a hollow needle.
- 2. Guidewire: Pass a flexible guidewire through the needle into the vessel lumen.
- 3. Needle Removal: Withdraw the needle, leaving the guidewire in place.
- 4. Sheath/Catheter: Thread an introducer sheath or catheter over the guidewire.
- 5. Guidewire Removal: Remove the guidewire, leaving the sheath/catheter for access.

Microseldinger Technique Steps

Common Arterial Access Sites
- Common Femoral Artery (CFA): Traditional workhorse. Puncture below the inguinal ligament to avoid retroperitoneal hemorrhage.
- Radial Artery: Preferred for cardiac catheterization (↓bleeding, ↑patient comfort).
- Brachial Artery: Alternative; higher risk of nerve injury and thrombosis.

⭐ Pre-procedure Check: The Allen test must be performed to confirm adequate collateral circulation from the ulnar artery before radial artery cannulation. This mitigates the risk of hand ischemia.

Contrast & Complications - The Aftermath

Contrast-Induced Nephropathy (CIN)
- ⚠️ Highest risk: Pre-existing CKD (eGFR <60), diabetes, dehydration, concurrent nephrotoxins.
- Pathophysiology: Direct tubular toxicity & renal vasoconstriction.
- Prevention: IV hydration (isotonic saline) is key. Consider N-acetylcysteine (antioxidant).
- Course: Serum creatinine (SCr) rises within 24-48 hrs, peaks at 3-5 days, resolves in 7-10 days.
Anaphylactoid/Allergic Reactions
- Acute hypersensitivity; not a true IgE-mediated allergy.
- Symptoms: Urticaria, angioedema, bronchospasm, shock.
- Management: Pre-medicate high-risk patients (prior reaction) with corticosteroids + H1/H2 blockers.
Gadolinium Contrast (MRA)
- ⚠️ Nephrogenic Systemic Fibrosis (NSF): Rare but severe fibrosing disease in patients with GFR <30 mL/min. Avoid gadolinium in this group.

⭐ Metformin & Contrast: Hold metformin on the day of contrast and for 48 hours after. Resume only after re-checking renal function. Risk of lactic acidosis if CIN develops.

Pathophysiology of Contrast-Induced Nephropathy

High‑Yield Points - ⚡ Biggest Takeaways

Seldinger technique is the fundamental method for percutaneous vascular access.

Digital Subtraction Angiography (DSA) provides the clearest images by subtracting pre-contrast bone and soft tissue.

Iodinated contrast is standard; be cautious of contrast-induced nephropathy (CIN), especially in patients with renal disease.

The most common complication is an access site hematoma or bleeding.

Gold standard for diagnosing conditions like vasculitis, aneurysms, and AVMs.

Catheter shape is crucial; Judkins for coronaries, Simmons for tortuous vessels.

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