Risk Factors for Contrast Reactions — MCQs
I/V contrast is not used in -
Which of the following contrast agents is PREFERRED in a patient with renal dysfunction for the prevention of contrast-induced nephropathy?
Adverse reactions following whole-cell pertussis immunization include:
Which of the following is NOT a characteristic feature of anaphylactic shock?
Which of the following statements about contrast in radiography is true:
Which of the following suture materials has the least tissue reaction?
Which type of suture is primarily used for the repair of a complete perineal tear?
Which research method is most appropriate for studying the progression of a disease over time?
All of the following are true regarding congenital dislocation of the hip except which of the following?
Which of the following is not a risk factor for cholangiocarcinoma?
Risk Factors for Contrast Reactions Indian Medical PG Practice Questions and MCQs
Question 1: I/V contrast is not used in -
- A. IVP
- B. Myelography (Correct Answer)
- C. MRI
- D. CT scan
Explanation: ***Myelography*** - Myelography involves injecting contrast material directly into the **subarachnoid space** of the spinal canal to visualize nerve roots and the spinal cord, and therefore does not use intravenous contrast. - The contrast in myelography is typically **iodinated non-ionic contrast** injected intrathecally, not intravenously. *IVP* - **Intravenous Pyelogram (IVP)** is a radiological procedure that specifically uses **intravenous iodinated contrast** to visualize the kidneys, ureters, and bladder. - The contrast is excreted by the kidneys, highlighting the urinary tract structures on X-ray images. *MRI* - While many MRI scans do not require contrast, **intravenous gadolinium-based contrast agents** are commonly used to enhance visualization of certain pathologies like tumors, inflammation, or vascular anomalies. - The contrast is administered intravenously to accumulate in areas with increased vascularity or disrupted blood-brain barrier. *CT scan* - **CT scans** frequently utilize **intravenous iodinated contrast** to improve the visibility of blood vessels, organs, and various lesions like tumors or inflammatory processes. - The contrast enhances density differences between tissues, making pathologies more conspicuous.
Question 2: Which of the following contrast agents is PREFERRED in a patient with renal dysfunction for the prevention of contrast-induced nephropathy?
- A. Iso-osmolar contrast (Correct Answer)
- B. High osmolar contrast
- C. Ionic contrast
- D. Low osmolar contrast
Explanation: ***Iso-osmolar contrast*** - **Iso-osmolar contrast agents** (e.g., iodixanol) have an osmolality of ~290 mOsm/kg, which is identical to that of plasma. - **This is the PREFERRED choice** in patients with renal dysfunction as multiple studies demonstrate the lowest risk of contrast-induced nephropathy (CIN). - The iso-osmolar formulation minimizes osmotic stress on renal tubules and reduces the risk of acute kidney injury. - **Current guidelines recommend iso-osmolar agents as first-line** in high-risk patients with pre-existing renal impairment. *Low osmolar contrast* - **Low osmolar contrast agents** have osmolality of 600-900 mOsm/kg, which is significantly lower than high osmolar agents but still 2-3 times higher than plasma. - While **acceptable and safer than high osmolar agents**, they are not as optimal as iso-osmolar contrast for patients with renal dysfunction. - These agents are widely used and represent a reasonable alternative when iso-osmolar agents are not available. *High osmolar contrast* - **High osmolar contrast agents** have osmolality >1400 mOsm/kg (about 5 times that of plasma). - They carry the **highest risk of contrast-induced nephropathy** due to severe osmotic load and direct tubular toxicity. - **Contraindicated or strongly avoided** in patients with pre-existing renal dysfunction. *Ionic contrast* - **Ionic contrast** refers to the chemical structure (dissociates into ions) rather than osmolality. - Can be either high or low osmolar—the ionic nature alone does not determine renal safety. - The critical factor for nephrotoxicity prevention is osmolality, not ionic charge.
Question 3: Adverse reactions following whole-cell pertussis immunization include:
- A. Fever
- B. Anaphylaxis
- C. Local swelling
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** are well-documented adverse reactions following whole-cell pertussis immunization. *Fever* - **Fever** is a common systemic adverse reaction following whole-cell pertussis immunization, occurring in **10-50%** of recipients - It usually presents within the first **24-48 hours** after vaccination due to the immunostimulatory components of the vaccine - Generally mild and self-limiting, resolving within 1-2 days *Anaphylaxis* - **Anaphylaxis** is a rare but severe allergic reaction that can occur after whole-cell pertussis vaccination (approximately **1 in 1,000,000** doses) - It is an **IgE-mediated type I hypersensitivity reaction** requiring immediate medical intervention with intramuscular epinephrine - Usually occurs within **minutes to hours** after vaccination *Local swelling* - **Local swelling** at the injection site is a very common adverse reaction, occurring in **>50%** of recipients - This reaction is typically mild, localized to the injection site, and represents a normal inflammatory response - Usually resolves spontaneously within **2-3 days** without specific treatment
Question 4: Which of the following is NOT a characteristic feature of anaphylactic shock?
- A. Angioedema
- B. Urticarial rash
- C. Pedal edema (Correct Answer)
- D. Flushing
Explanation: ***Pedal edema*** - While **edema** can occur in anaphylaxis due to increased vascular permeability, **pedal edema** (swelling primarily in the lower extremities) is not a defining characteristic or a primary life-threatening feature of anaphylactic shock. - Anaphylactic shock primarily manifests with systemic symptoms like **hypotension**, **bronchospasm**, and widespread **urticaria** or **angioedema**, rather than isolated peripheral swelling [1], [3]. *Angioedema* - **Angioedema** is a common and often serious feature of anaphylaxis, involving swelling of deeper layers of the skin and mucous membranes [1]. - It can affect the **lips**, **face**, **throat**, and **airway**, potentially leading to airway obstruction [3]. *Urticarial rash* - An **urticarial rash**, or **hives**, is a hallmark cutaneous manifestation of anaphylaxis, characterized by itchy red welts [2]. - It is caused by the release of histamine and other mediators that increase capillary permeability, leading to fluid leakage into the skin [2], [3]. *Flushing* - **Flushing** is a common early symptom of anaphylaxis, characterized by sudden redness and warmth of the skin [1]. - It results from widespread **vasodilation** caused by mediator release, such as histamine [3].
Question 5: Which of the following statements about contrast in radiography is true:
- A. Gadolinium cannot cross an intact blood brain barrier
- B. Iohexol is a high osmolar contrast media
- C. Non-ionic contrast agents are always high osmolar
- D. Ionic monomers have three iodine atoms per two particles in solution (Correct Answer)
Explanation: ***Ionic monomers have three iodine atoms per two particles in solution*** - **Ionic monomeric contrast agents** (e.g., diatrizoate, iothalamate) dissociate in solution, producing **two particles** (one cation and one anion containing three iodine atoms) per molecule. - This dissociation results in a **high osmolality** compared to non-ionic agents, as osmolality is determined by the number of particles in solution. *Gadolinium cannot cross an intact blood brain barrier* - This statement is **FALSE** - **Gadolinium-based contrast agents CAN cross the blood-brain barrier when it is compromised**. - They are used in MRI precisely because they extravasate into tissues where the **blood-brain barrier is disrupted**, such as in tumors, inflammation, or infections. - However, they do **not cross an intact BBB** due to their size and hydrophilicity. *Iohexol is a high osmolar contrast media* - **Iohexol** is a **non-ionic, low osmolality contrast medium** (LOCM). - Its non-ionic nature means it does not dissociate in solution, leading to a significantly lower osmolality compared to older ionic agents. *Non-ionic contrast agents are always high osmolar* - **Non-ionic contrast agents** are characterized by their molecular structure which **does not dissociate into ions** in solution. - This property makes them **low osmolar** or **iso-osmolar**, meaning they have fewer particles in solution compared to ionic agents, thereby reducing osmolality.
Question 6: Which of the following suture materials has the least tissue reaction?
- A. Silk
- B. Cotton / Linen
- C. Chromic catgut
- D. Stainless steel (Correct Answer)
Explanation: ***Stainless steel*** - **Stainless steel** is a **monofilament** suture with the **lowest tissue reactivity** due to its inert nature. - It is often used in situations requiring maximal strength and minimal biological interaction, such as abdominal wall closure or orthopedic procedures. *Silk* - **Silk** is a **multifilament, natural, non-absorbable** suture and is known for its **moderate tissue reactivity** due to its braided structure and organic origin. - While it provides good knot security, its reactivity makes it unsuitable for areas where minimal foreign body reaction is paramount. *Cotton / Linen* - **Cotton and linen** sutures are **natural, multifilament, non-absorbable** materials that exhibit significant **tissue reactivity**. - Their fibrous nature can lead to considerable inflammatory response and are rarely used in modern surgical practice. *Chromic catgut* - **Chromic catgut** is a **natural, absorbable** suture treated with chromium salts to prolong its absorption time, but it still triggers a **significant inflammatory response** as it is absorbed by enzymatic digestion. - Its high tissue reactivity makes it less ideal for situations requiring minimal foreign body reaction compared to synthetic or metallic sutures.
Question 7: Which type of suture is primarily used for the repair of a complete perineal tear?
- A. Monocryl
- B. Catgut
- C. Silk
- D. Vicryl (Correct Answer)
Explanation: ***Correct Answer: Vicryl (Polyglactin 910)*** - **Vicryl is the gold standard suture material** for repair of complete perineal tears (third and fourth-degree) - It is a **synthetic absorbable braided suture** with excellent tensile strength that maintains tissue support during critical healing phase - **Absorption profile**: Loses 50% tensile strength by 2 weeks, completely absorbed in 56-70 days, ideal for perineal tissue healing - **Minimal tissue reaction** and low infection risk compared to natural sutures - **Recommended by RCOG and ACOG guidelines** for layer-by-layer repair of perineal tears involving anal sphincter *Incorrect: Monocryl* - Monocryl (Poliglecaprone 25) is a fast-absorbing monofilament suture primarily used for **subcuticular skin closure** - Not the first choice for deep tissue repair of complete perineal tears - Has faster absorption (90-120 days) which may not provide adequate support for sphincter repair *Incorrect: Catgut* - Catgut is a natural absorbable suture that was **historically used but is now largely obsolete** - **Higher tissue reaction**, increased infection risk, and unpredictable absorption make it unsuitable - Modern synthetic sutures like Vicryl have replaced catgut in current obstetric practice *Incorrect: Silk* - Silk is a **non-absorbable suture** that is inappropriate for perineal repair - Would require removal and carries risk of chronic foreign body reaction - Never used for internal structures in perineal reconstruction
Question 8: Which research method is most appropriate for studying the progression of a disease over time?
- A. Cohort Study (Correct Answer)
- B. Cross sectional study
- C. Randomized Control Trials
- D. Interventional Studies
Explanation: ***Cohort Study*** - A **cohort study** observes a group of individuals over a period of time, allowing researchers to track the **natural progression of a disease** from exposure through onset and various stages. - This design is ideal for investigating the **incidence** of disease and identifying risk factors over time. *Cross sectional study* - A **cross-sectional study** assesses exposure and outcome at a **single point in time**, providing a snapshot. - It cannot establish temporality or observe disease progression, as it does not follow individuals over time. *Randomized Control Trials* - **Randomized controlled trials (RCTs)** are primarily designed to evaluate the **effectiveness of interventions** or treatments by comparing outcomes between an experimental group and a control group. - While they follow participants over time, their main goal is not to study the natural progression of an untreated disease. *Interventional Studies* - **Interventional studies** involve manipulating an exposure or treatment to observe its effect, often to test a hypothesis about a causal relationship. - While they track outcomes over time, their focus is on the impact of the intervention rather than the natural history or progression of a disease without intervention.
Question 9: All of the following are true regarding congenital dislocation of the hip except which of the following?
- A. It is always bilateral (Correct Answer)
- B. Asymmetric thigh folds may be seen
- C. Galeazzi sign and Ortolani's test may be positive
- D. Oligohydramnios is a known risk factor for congenital dislocation of the hip
Explanation: ***It is always bilateral*** - **Congenital dislocation of the hip (CDH)** is more commonly **unilateral**, with a predilection for the left hip. - While it can be bilateral, stating it is *always* bilateral is incorrect. - **Bilateral CDH** occurs in only about 20% of cases. *Asymmetric thigh folds may be seen* - **Asymmetric thigh folds** are a common soft sign of **developmental dysplasia of the hip (DDH)**, though they can also be seen in normal infants. - This asymmetry is due to the femoral head's abnormal position, leading to unequal skin fold distribution on the affected side. *Galeazzi sign and Ortolani's test may be positive* - The **Galeazzi sign** (also known as the Allis sign) indicates limb length discrepancy, often seen in unilateral hip dislocation when the knees are flexed. - **Ortolani's test** is a specific maneuver used to reduce a dislocated hip, producing a characteristic *clunk* as the femoral head re-enters the acetabulum. *Oligohydramnios is a known risk factor for congenital dislocation of the hip* - **Oligohydramnios** (decreased amniotic fluid) is a well-established risk factor for CDH due to restricted fetal movement and abnormal intrauterine positioning. - Other risk factors include **breech presentation**, **female sex**, **firstborn child**, and **family history**. - **Polyhydramnios** (excess amniotic fluid) is NOT associated with increased risk of CDH.
Question 10: Which of the following is not a risk factor for cholangiocarcinoma?
- A. Thorotrast
- B. Radon
- C. Dioxin
- D. Aflatoxin (Correct Answer)
Explanation: ***Aflatoxin*** - **Aflatoxin** is a potent **hepatocarcinogen** produced by *Aspergillus* species that is specifically and strongly linked to **hepatocellular carcinoma (HCC)** [1], NOT cholangiocarcinoma. - This is the **most clearly unrelated** risk factor to cholangiocarcinoma among the options, as its carcinogenic mechanism targets hepatocytes specifically [1], [2]. - It contaminates crops in warm, humid regions and is a well-established cause of liver cancer in endemic areas [1]. *Thorotrast* - **Thorotrast** (thorium dioxide) was a radioactive contrast agent used until the 1950s that **IS a known risk factor** for cholangiocarcinoma. - Due to prolonged retention in the liver and biliary system, it significantly increases the risk of both **cholangiocarcinoma** and **hepatic angiosarcoma** [3]. - Its use was discontinued precisely because of its strong carcinogenic potential. *Radon* - **Radon** is a naturally occurring radioactive gas that is primarily and overwhelmingly associated with **lung cancer** from inhalation exposure. - While a potent carcinogen, it has **no established epidemiological link** to cholangiocarcinoma due to its route of exposure and target organ. *Dioxin* - **Dioxins** are environmental pollutants with documented carcinogenic effects. - While some studies have explored potential links to various cancers, dioxin is **not recognized as an established risk factor** for cholangiocarcinoma in major medical references. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 876-877. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 331-332. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 216-217.
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