Vascular Access for Hemodialysis — MCQs
The most common cause of acquired AV fistula is:
The largest component of the total peripheral resistance is due to:
Which one of the following is not a wound closure technique?
The procedure of choice for the evaluation of an aneurysm is:
All are true about GFR except:
What does the measurement of Glomerular Filtration Rate (GFR) help determine in kidney function?
What is the significance of the term 'Corona mortis' in human anatomy?
In which of the following locations should the incision be made for the saphenous cutdown procedure in an obese patient with no visible or palpable superficial veins, requiring intravenous fluids in shock?
Which of the following conditions does NOT increase the risk of deep vein thrombosis (DVT)?
Allen's test is used to diagnose which condition?
Vascular Access for Hemodialysis Indian Medical PG Practice Questions and MCQs
Question 1: The most common cause of acquired AV fistula is:
- A. Bacterial infection
- B. Fungal infection
- C. Blunt trauma
- D. Penetrating trauma (Correct Answer)
Explanation: ***Penetrating trauma*** - **Penetrating trauma** is the most common cause of **acquired AV fistulas** due to direct injury to adjacent artery and vein. - This type of injury can result from causes like **gunshot wounds, stab wounds, or iatrogenic procedures** (e.g., catheterizations). *Bacterial infection* - While infections can cause vascular damage, they are **not the most common cause** of acquired AV fistulas. - Infections like **endocarditis** or localized abscesses can lead to vascular erosion, but this is less frequent than trauma. *Fungal infection* - **Fungal infections** are a much rarer cause of vascular damage leading to AV fistulas compared to bacterial infections or trauma. - They typically occur in immunocompromised individuals or in specific settings, not as a common cause of acquired AV fistulas. *Blunt trauma* - **Blunt trauma** can cause vascular injury, but it is **less likely to directly create an AV fistula** compared to penetrating trauma. - Blunt force is more commonly associated with vessel rupture, dissection, or pseudoaneurysm formation, rather than a direct connection between an artery and a vein.
Question 2: The largest component of the total peripheral resistance is due to:
- A. Venules
- B. Arterioles (Correct Answer)
- C. Capillaries
- D. Precapillary sphincters
Explanation: ***Arterioles*** - **Arterioles** are the primary site of **resistance** in the cardiovascular system due to their relatively small diameter and the significant ability of their **smooth muscle** walls to constrict or dilate. - This resistance plays a crucial role in regulating **blood flow** to various organs and contributes to **mean arterial pressure**. *Venules* - **Venules** are primarily involved in collecting blood from capillaries and have relatively low resistance compared to arteries and arterioles. - While they contribute to capacitance, their impact on **total peripheral resistance** is minimal. *Capillaries* - Although **capillaries** have very small diameters, their sheer number in parallel reduces the overall resistance of the capillary bed. - The primary function of capillaries is **exchange** of nutrients and waste, not primarily resistance. *Precapillary sphincters* - **Precapillary sphincters** control blood flow *into* capillaries from arterioles, acting as gates. - While they regulate flow to specific capillary beds, they are not the largest *component* of total systemic resistance; the **arterioles themselves** are.
Question 3: Which one of the following is not a wound closure technique?
- A. Composite graft
- B. Vascular graft (Correct Answer)
- C. Partial thickness skin graft
- D. Musculocutaneous flap
Explanation: ***Vascular graft*** - A **vascular graft** is a tube-like structure used to bypass or replace a diseased or damaged blood vessel. - Its primary purpose is to **restore blood flow**, not to close a wound on the body surface or replace missing tissue. *Partial thickness skin graft* - A **partial thickness skin graft** involves transplanting the epidermis and a portion of the dermis to cover a wound. - This is a common and effective technique for **wound closure**, particularly for large surface area wounds or burns. *Composite graft* - A **composite graft** is a graft consisting of multiple tissue types, such as skin, cartilage, and fat, often used for reconstruction. - This is a direct method of **wound closure** and tissue replacement, particularly in areas requiring structural support and soft tissue coverage. *Musculocutaneous flap* - A **musculocutaneous flap** involves the transfer of skin, subcutaneous tissue, and an underlying muscle to cover a wound. - This is a versatile **wound closure technique** that provides robust soft tissue coverage and blood supply to complex defects.
Question 4: The procedure of choice for the evaluation of an aneurysm is:
- A. Computed tomography (Correct Answer)
- B. Ultrasonography
- C. Magnetic resonance imaging
- D. Angiography
Explanation: ***Computed tomography*** **Computed tomography (CT)**, particularly **CT angiography (CTA)**, is widely considered the procedure of choice for evaluating aneurysms due to its **rapid acquisition**, **high spatial resolution**, and ability to visualize the vessel lumen and surrounding structures. **Key advantages:** - Particularly useful for assessing aneurysm size, morphology, thrombus formation, and rupture - Excellent for both emergent and elective settings - Widely available and fast imaging acquisition - Provides comprehensive anatomical detail *Ultrasonography* **Ultrasonography** is an excellent and cost-effective **screening tool for abdominal aortic aneurysms (AAA)** because it is non-invasive and does not involve radiation. However, its utility is limited for: - Complex aneurysms requiring detailed anatomical information - Less accessible locations (e.g., thoracic, cerebral aneurysms) - **Operator dependence** and **limited field of view** restrict its use as a definitive diagnostic tool *Magnetic resonance imaging* **Magnetic resonance imaging (MRI)** and **magnetic resonance angiography (MRA)** provide excellent soft tissue contrast without ionizing radiation and can accurately evaluate aneurysm morphology and flow characteristics. However, MRI is: - More time-consuming and expensive - May be contraindicated in patients with metallic implants or claustrophobia - Less suitable for initial acute evaluation compared to CT *Angiography* **Angiography**, traditionally a catheter-based invasive procedure, provides detailed images of the vessel lumen and is excellent for evaluating precise anatomy and planning endovascular repair. While it offers highly detailed images, its: - Invasiveness - Exposure to radiation and contrast agents - Potential for complications These factors typically reserve it for **interventional planning** or when non-invasive methods are inconclusive, rather than as the primary diagnostic tool.
Question 5: All are true about GFR except:
- A. 30-40% decrease after 70 years of age
- B. GFR is dependent on height in children
- C. Chronic Kidney Disease (CKD) is defined as GFR < 60 ml/min/1.73 m² for 3 months or more.
- D. Best estimated by creatinine clearance (Correct Answer)
Explanation: ***Best estimated by creatinine clearance*** - While **creatinine clearance** can be used as a measure of GFR, it is not the *best* estimate; it tends to slightly **overestimate** GFR due to tubular secretion of creatinine. [1] - The gold standard for measuring GFR involves methods like **inulin clearance**, but in clinical practice, GFR is often *estimated* using equations based on **serum creatinine** (e.g., CKD-EPI, MDRD). [2] *30-40% decrease after 70 years of age* - **Aging** is associated with a physiological decline in GFR, with a general decrease often cited as 30-40% after the age of 70 years. - This decline is part of the normal **age-related changes in renal function**. *GFR is dependent on height in children* - In children, GFR is often adjusted for **body surface area (BSA)**, which is calculated based on both **height and weight**, making height an important factor. [1] - This adjustment is crucial for accurate assessment of renal function in a growing pediatric population. *Chronic Kidney Disease (CKD) is defined as GFR < 60 ml/min/1.73 m² for 3 months or more.* - This statement accurately reflects the widely accepted definition of **Chronic Kidney Disease (CKD)** according to clinical guidelines. [3] - A GFR below this threshold sustained for more than three months indicates persistent kidney damage or dysfunction.
Question 6: What does the measurement of Glomerular Filtration Rate (GFR) help determine in kidney function?
- A. Heart rate
- B. Recovery from shock
- C. Stage of kidney disease (Correct Answer)
- D. Blood volume
Explanation: Stage of kidney disease - A low GFR indicates impaired kidney function, helping to classify the severity and stage of chronic kidney disease (CKD) [1]. - Monitoring GFR over time is crucial for assessing disease progression and guiding treatment strategies [1]. *Heart rate* - Heart rate is a measure of cardiac function and is not directly assessed by GFR. - Kidney function can indirectly affect heart rate over time (e.g., in advanced kidney disease with fluid overload), but GFR itself doesn't measure it. *Recovery from shock* - While kidney function is important during shock, GFR primarily measures the kidney's filtration capacity at a given moment. - Recovery from shock involves many physiological parameters beyond just kidney filtration, such as blood pressure and organ perfusion. *Blood volume* - Blood volume is regulated by many mechanisms, including hormonal systems (e.g., renin-angiotensin-aldosterone system) and fluid intake/excretion. - Although kidneys play a role in fluid balance, GFR specifically measures the rate of filtration of blood plasma, not the overall blood volume [1].
Question 7: What is the significance of the term 'Corona mortis' in human anatomy?
- A. Anastomosis between superior and inferior gluteal arteries
- B. A ligament connecting the pubic symphysis
- C. A nerve crossing the pelvic brim
- D. Anastomosis between obturator and inferior epigastric vessels (Correct Answer)
Explanation: ***Anastomosis between obturator and inferior epigastric vessels*** - **Corona mortis**, meaning "crown of death" in Latin, refers to a clinically significant vascular anastomosis that passes over the superior pubic ramus. - This anastomosis usually occurs between the **obturator artery** (a branch of the internal iliac artery) and the **inferior epigastric artery** (a branch of the external iliac artery), posing a risk of severe hemorrhage during surgical procedures in the retropubic space [1]. *Anastomosis between superior and inferior gluteal arteries* - While gluteal arteries do anastomose, they form a crucial part of the **cruciate anastomosis of the thigh**, not the corona mortis. - This anastomosis is important for blood supply to the hip joint and thigh musculature, far removed from the retropubic space. *A ligament connecting the pubic symphysis* - The pubic symphysis is connected by ligaments such as the **superior and arcuate pubic ligaments**, which provide stability to the joint. - These are fibrous structures and do not represent a vascular anastomosis. *A nerve crossing the pelvic brim* - Several nerves cross the pelvic brim, such as the **obturator nerve** or the **femoral nerve**, but these are neural structures. - The term corona mortis specifically refers to a **vascular connection**, not a nerve.
Question 8: In which of the following locations should the incision be made for the saphenous cutdown procedure in an obese patient with no visible or palpable superficial veins, requiring intravenous fluids in shock?
- A. Anterior to the medial malleolus (Correct Answer)
- B. Posterior to the lateral malleolus
- C. Anterior to the lateral malleolus
- D. On the dorsum of the foot
Explanation: ***Anterior to the medial malleolus*** - The **greater saphenous vein** consistently runs anterior, one finger breadth to the medial malleolus, making this a reliable site for incision even when veins are not visible or palpable, particularly in **obese patients** or those in shock. - This location allows for direct access to a relatively large vein, crucial for rapid **intravenous fluid administration** in an emergency. *Posterior to the lateral malleolus* - This location is typically associated with the **small saphenous vein**, which is generally smaller and more variable in its superficial course, making it less dependable for cutdown in an emergent situation. - Incision here carries a higher risk of damaging the **sural nerve**, leading to sensory deficits. *Anterior to the lateral malleolus* - The veins in this region are usually smaller and less surgically significant for a **saphenous cutdown** required for rapid fluid infusion. - Accessing a suitable vein here is often more challenging and time-consuming, especially in an obese patient. *On the dorsum of the foot* - While veins on the **dorsum of the foot** are commonly used for routine IV access, they are smaller and more prone to collapse during shock, making them inadequate for rapid, high-volume fluid resuscitation. - The superficial location also makes them more susceptible to accidental dislodgement during patient movement.
Question 9: Which of the following conditions does NOT increase the risk of deep vein thrombosis (DVT)?
- A. Hip fracture and prolonged immobilization
- B. Young age (< 25 years) (Correct Answer)
- C. Deficiency of Protein C and Protein S
- D. Factor V Leiden mutation
Explanation: The risk of developing Deep Vein Thrombosis (DVT) is governed by **Virchow’s Triad**: endothelial injury, stasis of blood flow, and hypercoagulability. ### Why "Young age (< 25 years)" is the correct answer: Age is a significant independent risk factor for DVT. The incidence of venous thromboembolism (VTE) is extremely low in children and young adults (approximately 1 in 10,000) and increases exponentially with age. This is due to age-related changes such as decreased vessel wall elasticity, increased plasma levels of clotting factors, and higher rates of comorbidities or immobility. Therefore, being under 25 is considered a **protective factor** rather than a risk factor. ### Explanation of Incorrect Options: * **Hip fracture and prolonged immobilization:** These represent two arms of Virchow’s Triad. Surgery/trauma causes endothelial injury, while immobilization leads to venous stasis. Orthopedic surgeries (hip/knee) carry the highest risk of DVT among all surgical procedures. * **Deficiency of Protein C and Protein S:** These are natural anticoagulants that inhibit Factors Va and VIIIa. Their deficiency leads to a state of **hereditary thrombophilia**, significantly increasing the risk of clot formation. * **Factor V Leiden mutation:** This is the **most common inherited cause** of hypercoagulability. It involves a mutation that makes Factor V resistant to inactivation by activated Protein C (APC resistance). ### NEET-PG High-Yield Pearls: * **Most common inherited risk factor for DVT:** Factor V Leiden mutation. * **Most common acquired risk factor for DVT:** Recent surgery or trauma. * **Gold Standard Investigation for DVT:** Contrast Venography (though Duplex Ultrasound is the initial investigation of choice). * **Trousseau’s Sign:** Migratory thrombophlebitis associated with visceral malignancy (most commonly pancreatic cancer).
Question 10: Allen's test is used to diagnose which condition?
- A. Thoracic outlet syndrome
- B. Palmar arch insufficiency (Correct Answer)
- C. Superior vena cava syndrome
- D. Coarctation of the aorta
Explanation: **Explanation:** **Allen’s Test** is a clinical bedside assessment used to evaluate the **patency of the radial and ulnar arteries** and the adequacy of the **dual blood supply to the hand via the palmar arches**. 1. **Why Option B is Correct:** The test is performed by asking the patient to clench their fist while the clinician compresses both the radial and ulnar arteries at the wrist. When the patient opens their hand (which appears blanched), the clinician releases pressure from one artery (usually the ulnar). If the palm flushes (reperfuses) within 5–15 seconds, the arch is patent. If the hand remains pale, it indicates **palmar arch insufficiency** or ulnar artery occlusion. This is mandatory before procedures like **Radial Artery Harvesting** (for CABG) or **Arterial Blood Gas (ABG)** sampling to ensure the hand remains viable if the radial artery is compromised. 2. **Why Other Options are Incorrect:** * **Thoracic Outlet Syndrome (TOS):** Diagnosed using **Adson’s test**, Roos test, or Wright’s maneuver, which assess compression of the neurovascular bundle at the neck/shoulder. * **Superior Vena Cava (SVC) Syndrome:** Characterized by facial puffiness and dilated neck veins; diagnosed via clinical signs (Pemberton’s sign) and CT imaging. * **Coarctation of the Aorta:** Identified by radio-femoral delay and rib notching on X-ray. **High-Yield Clinical Pearls for NEET-PG:** * **Modified Allen’s Test:** The standard version used today where only one artery is released at a time. * **Normal Refill Time:** Less than 7 seconds is considered normal; 7–15 seconds is equivocal; **>15 seconds is abnormal**. * **Alternative:** If Allen’s test is inconclusive, **Pulse Oximetry** or **Doppler Ultrasound** can be used for more objective assessment.
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