Evidence-Based Surgery — MCQs
Which of the following is not considered a type of subject bias?
Investigation of choice in an unstable patient with suspected intra-abdominal injury is -
What is the condition commonly known as jumper's knee?
All of the following are done to remove Confounding except:
Incisions for medicolegal autopsy include all except?
In a cohort study conducted with 100 individuals in each group (exposed and non-exposed), out of those exposed to the risk factor, 10 are diseased, and out of those not exposed to the risk factor, only 5 are diseased. What is the relative risk?
Which hernia repair technique emphasizes tension-free repair with mesh reinforcement?
Which of the following statements is false regarding postpartum hemorrhage and pelvic hematomas?
A researcher wants to determine whether there is an association between CRP values and the risk of MI or cancer. Four relative risk (RR) values were plotted $(0.5,1.5,1.7,1.8)$ with respect to CRP levels. What conclusion can be drawn?
Which of the following statements about the management of haematomas is NOT correct?
Evidence-Based Surgery Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is not considered a type of subject bias?
- A. Recall bias
- B. Selection bias (Correct Answer)
- C. Hawthorne bias
- D. Reporting bias
Explanation: ***Selection bias*** - **Selection bias** occurs when participants are chosen or remain in a study in a way that introduces a systematic error, leading to a sample that does not accurately represent the target population. - It is a **study design and sampling issue** that occurs at the **recruitment** or **retention stage**, not a bias arising from the subjects' own behavior or reporting. - Unlike subject biases, selection bias is introduced by the **investigators or study methodology**, not by the participants themselves. *Recall bias* - **Recall bias** is a type of **subject bias** where participants differentially remember and report past exposures based on their outcome status. - Subjects with disease may recall exposures more accurately than healthy controls, introducing **systematic error from the subject's memory**. *Hawthorne bias* - **Hawthorne bias** (observer effect) is a **subject bias** where participants modify their behavior because they know they are being studied. - The **subject's awareness** of observation directly influences their actions, responses, or adherence. *Reporting bias* - **Reporting bias** is a **subject bias** where participants selectively disclose or withhold information based on social desirability, embarrassment, or perceived consequences. - This bias arises from the **subject's decision** about what to report.
Question 2: Investigation of choice in an unstable patient with suspected intra-abdominal injury is -
- A. USG (FAST) (Correct Answer)
- B. CT scan
- C. X-ray abdomen
- D. DPL
Explanation: ***USG*** - **Focused assessment with sonography for trauma (FAST) exam** is the investigation of choice in an **unstable patient** due to its rapid, non-invasive nature and ability to detect free fluid (blood) in the peritoneal, pericardial, and pleural spaces. - It can be performed at the **bedside** without moving the patient, making it ideal for hemodynamically unstable individuals with suspected intra-abdominal injury. *CT scan* - While a **CT scan** provides detailed anatomical information, it requires the patient to be stable enough for transport to a radiology suite and prolonged scanning time. - It is often difficult to obtain in **unstable patients** who may require continuous resuscitation and monitoring. *X-ray abdomen* - An **X-ray abdomen** has limited utility for detecting intra-abdominal injuries and primarily identifies issues like free air under the diaphragm (suggesting hollow organ perforation) or foreign bodies. - It is **not sensitive** for detecting free fluid (hemoperitoneum) or solid organ injuries, which are critical in trauma. *DPL* - **Diagnostic peritoneal lavage (DPL)** is an invasive procedure that involves inserting a catheter into the peritoneal cavity to detect blood or other fluid. - While sensitive, it is **invasive**, can complicate subsequent imaging, and has largely been replaced by the FAST exam due to the latter's non-invasive nature and comparable diagnostic accuracy for free fluid.
Question 3: What is the condition commonly known as jumper's knee?
- A. Inflammation of the patellar tendon at its insertion on the patella.
- B. Tendinopathy of the quadriceps tendon.
- C. Injury to the hamstring tendon.
- D. Patellar tendonitis due to overuse of the patellar tendon. (Correct Answer)
Explanation: ***Patellar tendonitis due to overuse of the patellar tendon.*** - **Jumper's knee** is the common term for **patellar tendonitis**, which specifically refers to inflammation of the patellar tendon. - This condition is frequently caused by **overuse**, especially in activities involving repetitive jumping and landing. *Inflammation of the patellar tendon at its insertion on the patella.* - While jumper's knee does involve inflammation of the patellar tendon, it is more commonly at its insertion on the **tibial tubercle** or specifically its origin at the **inferior pole of the patella**, not necessarily at the patella itself. - This option is less precise as it describes only one aspect of the condition without mentioning the critical role of overuse. *Tendinopathy of the quadriceps tendon.* - **Tendinopathy of the quadriceps tendon** is a distinct condition affecting the tendon above the patella, known as **quadriceps tendinopathy**. - It presents with pain proximal to the patella, differentiating it from jumper's knee, which involves the tendon distal to the patella. *Injury to the hamstring tendon.* - An **injury to the hamstring tendon** would cause pain and symptoms on the posterior aspect of the knee or thigh. - This is completely unrelated to jumper's knee, which is characterized by anterior knee pain.
Question 4: All of the following are done to remove Confounding except:
- A. Randomization
- B. Random Selection
- C. Matching
- D. Blinding (Correct Answer)
Explanation: ***Blinding*** - **Blinding** is a technique used to minimize **bias** (e.g., observer bias, participant bias) by preventing study participants, researchers, or data analysts from knowing treatment assignments. It does **not address confounding variables**. - Blinding ensures that knowledge of the intervention does not influence the outcomes or their assessment, thereby controlling **information bias** and **performance bias**. *Randomization* - **Randomization** is a key method in experimental studies to control for **confounding variables** by distributing them equally among study groups. - It ensures that each participant has an **equal chance** of being assigned to any study group, thus minimizing systematic differences between groups at baseline. *Random Selection* - **Random selection** (or random sampling) is used primarily to create a sample that is **representative** of the larger population, thereby improving **external validity** and **generalizability**. - While it reduces **selection bias**, random selection is **not a standard method for controlling confounding**. Some sources suggest it may help balance unknown confounders compared to convenience sampling, but it is not classified among the primary confounding control methods (randomization, restriction, matching, stratification, multivariable analysis). - In this question context, if we consider standard epidemiological methods, random selection's role in confounding control is indirect at best. *Matching* - **Matching** is a technique used in observational studies to control for known **confounding variables** by selecting controls who are similar to cases with respect to these confounders. - For example, if age and sex are confounders, controls are matched to cases based on these characteristics to ensure comparability and reduce confounding.
Question 5: Incisions for medicolegal autopsy include all except?
- A. 'Y' shaped
- B. Modified 'Y' shaped
- C. Modified 'I' shaped (Correct Answer)
- D. 'T' shaped
Explanation: **Modified 'I' shaped** - The **modified 'I' shaped** incision is not a standard or recognized incision for a medicolegal autopsy. - Standard autopsy incisions are designed to provide comprehensive access while maintaining anatomical integrity as much as possible for future viewing or reconstruction. *'Y' shaped* - The **'Y' shaped incision** is a commonly used incision in medicolegal autopsies, starting at the shoulders and meeting at the xiphoid process, then extending to the pubic symphysis. - This incision allows for optimal exposure of the neck, chest, and abdominal organs. *Modified 'Y' shaped* - The **modified 'Y' shaped incision** is a variation of the standard 'Y' incision, often used to avoid cutting through prominent scars or to provide better access in specific cases. - It maintains the general principle of broad exposure while adapting to individual circumstances. *'T' shaped* - The **'T' shaped incision** is another recognized incision, though less common than the 'Y' shape, primarily used for better exposure of the neck and chest in certain circumstances. - It involves a horizontal incision across the upper chest, intersecting with a vertical midline incision.
Question 6: In a cohort study conducted with 100 individuals in each group (exposed and non-exposed), out of those exposed to the risk factor, 10 are diseased, and out of those not exposed to the risk factor, only 5 are diseased. What is the relative risk?
- A. 2 (Correct Answer)
- B. 1.5
- C. 0.75
- D. 1
Explanation: ***Correct Option: 2*** - The **incidence in the exposed group** is 10/100 = 0.1. - The **incidence in the non-exposed group** is 5/100 = 0.05. - **Relative risk (RR)** is calculated as the ratio of the incidence in the exposed group to the incidence in the non-exposed group: 0.1 / 0.05 = 2. - This indicates that the **exposed group has twice the risk** of developing the disease compared to the non-exposed group. *Incorrect Option: 1.5* - This value would be obtained if the ratio of incidences was 0.075 / 0.05 or 0.1/0.066, which is not consistent with the given data. - An RR of 1.5 indicates a **lesser strength of association** than what is observed in this study. *Incorrect Option: 0.75* - This value would result if the incidence in the exposed group was *lower* than in the non-exposed group (e.g., 0.05 / 0.066), suggesting a **protective effect**. - An RR < 1 implies that exposure is protective rather than a risk factor, which contradicts the given data. *Incorrect Option: 1* - A **relative risk of 1** indicates there is no difference in the risk of disease between the exposed and non-exposed groups. - This would mean the incidence rate in both groups is identical (e.g., 0.1 / 0.1 = 1), which contradicts the provided data where exposed group has higher incidence.
Question 7: Which hernia repair technique emphasizes tension-free repair with mesh reinforcement?
- A. Bassini's repair
- B. Darning repair
- C. Stoppa's preperitoneal repair
- D. Lichtenstein mesh repair (Correct Answer)
Explanation: ***Lichtenstein mesh repair*** - This technique is considered the gold standard for **inguinal hernia repair** due to its emphasis on a **tension-free approach** using a synthetic mesh. - The mesh reinforces the posterior wall of the inguinal canal without putting tension on the surrounding tissues, significantly reducing recurrence rates. *Stoppa's preperitoneal repair* - This is a **preperitoneal repair** technique that uses a large piece of mesh placed in the preperitoneal space to cover bilateral hernias or recurrent hernias, but it's not the primary technique for emphasizing tension-free repair *with mesh* for standard inguinal hernias in the same way Lichtenstein is. - It involves a larger dissection and is typically reserved for more complex cases. *Bassini's repair* - This is a **tension repair** technique where the conjoined tendon is sutured to the inguinal ligament. - It does not involve mesh and is associated with higher recurrence rates and postsurgical pain due to the tension on the tissues. *Darning repair* - This is another **tension repair** technique that involves suturing various muscular and aponeurotic layers together to reinforce the hernia defect. - Like Bassini's repair, it does not use mesh and relies on suturing native tissues under tension, leading to increased recurrence rates and patient discomfort.
Question 8: Which of the following statements is false regarding postpartum hemorrhage and pelvic hematomas?
- A. The vulva is the most common site for pelvic hematoma. (Correct Answer)
- B. Hematomas less than 5 cm can often be managed conservatively.
- C. Uterine atony is the most common cause of postpartum hemorrhage.
- D. The most common artery to form a vulvar hematoma is the pudendal artery.
Explanation: ***The vulva is the most common site for pelvic hematoma.*** - While vulvar hematomas are common, the **vagina is actually the most common site** for puerperal hematomas. - **Retroperitoneal hematomas** are the least common but most dangerous type, often associated with a higher mortality rate due to delayed diagnosis. *Hematomas less than 5 cm can often be managed conservatively.* - **Small, stable hematomas** (typically less than 2-5 cm) that are not expanding can often be managed with observation, pain control, and ice packs. - Close monitoring for continued bleeding, signs of infection, or hemodynamic instability is crucial even with conservative management. *Uterine atony is the most common cause of postpartum hemorrhage.* - **Uterine atony** (failure of the uterus to contract after birth) accounts for approximately 70-80% of all cases of postpartum hemorrhage. - This condition leads to excessive bleeding from the placental site due to the inability of uterine muscle fibers to compress blood vessels effectively. *The most common artery to form a vulvar hematoma is the pudendal artery.* - Vulvar hematomas primarily arise from injury to branches of the **pudendal artery**, particularly during lacerations or episiotomies. - Trauma to the **perineum** during childbirth can cause these arteries or their venous counterparts to bleed into the surrounding loose connective tissue.
Question 9: A researcher wants to determine whether there is an association between CRP values and the risk of MI or cancer. Four relative risk (RR) values were plotted $(0.5,1.5,1.7,1.8)$ with respect to CRP levels. What conclusion can be drawn?
- A. CRP has no relationship
- B. CRP decreases & disease decreases
- C. CRP increases disease/cancer risk (Correct Answer)
- D. No association in first interval
- E. CRP shows protective effect in first interval
Explanation: ***CRP increases disease/cancer risk*** - A **relative risk (RR)** greater than 1 indicates an increased risk of the outcome (MI or cancer) in the exposed group (higher CRP levels) compared to the unexposed group. - The plots show RRs of 1.5, 1.7, and 1.8, all of which are greater than 1, consistently indicating that higher CRP levels are associated with an elevated risk for MI or cancer. - The overall trend across the four intervals demonstrates a positive association between CRP and disease risk. *CRP has no relationship* - This conclusion is incorrect because three of the four plotted RR values (1.5, 1.7, 1.8) are above 1, indicating a positive association or increased risk. - An RR of 1 signifies no relationship, but the majority of values clearly deviate from 1, showing a definite association. *CRP decreases & disease decreases* - While one RR value (0.5) suggests a decreased risk, the majority of the given RRs (1.5, 1.7, 1.8) are greater than 1, indicating an increased risk. - This option would only be true if all or most RR values were less than 1, implying a protective effect, which is not the overall trend here. *No association in first interval* - The first interval shows an RR of 0.5. An RR of 1 indicates no association, while an RR of 0.5 actually indicates a **decreased risk or protective effect**, rather than no association. - Therefore, stating "no association" for the first interval is inaccurate given the definition of relative risk. *CRP shows protective effect in first interval* - While the first interval RR of 0.5 does suggest a protective effect in isolation, this option fails to capture the **overall conclusion** from all four data points. - When interpreting multiple RR values together, the predominant pattern (three values >1) indicates an overall increased risk, making this a misleading conclusion for the study as a whole.
Question 10: Which of the following statements about the management of haematomas is NOT correct?
- A. Haematoma must be operated. (Correct Answer)
- B. Some haematomas require surgical intervention.
- C. GCS assessment is helpful in prognosis.
- D. CT scan is the investigation of choice for acute haemorrhage.
Explanation: ***Haematoma must be operated.*** - This statement is **incorrect** because not all hematomas require surgical intervention. - The decision to operate depends on **size**, **location**, **neurological status**, **mass effect**, and rate of expansion. - Small, asymptomatic hematomas can be managed **conservatively** with serial imaging and close neurological monitoring. - Absolute statements like "must be operated" are incorrect in clinical practice where individualized management is essential. *Some haematomas require surgical intervention.* - This statement is **correct** - many hematomas necessitate surgical evacuation. - Indications for surgery include: **significant mass effect**, **midline shift >5mm**, **neurological deterioration**, **large volume** (>30mL for SDH, >50mL for ICH), or **posterior fossa hematomas** causing brainstem compression. - Surgical intervention aims to relieve intracranial pressure and prevent secondary brain injury. *GCS assessment is helpful in prognosis.* - This statement is **correct** - the **Glasgow Coma Scale (GCS)** is a critical prognostic tool. - GCS is used to assess severity of neurological injury and predict outcomes in head trauma patients. - Lower GCS scores (≤8) indicate severe injury with poorer prognosis, while higher scores suggest better outcomes. - GCS also guides management decisions including need for intubation and intensive monitoring. *CT scan is the investigation of choice for acute haemorrhage.* - This statement is **correct** - **Non-contrast CT (NCCT)** is the gold standard for acute intracranial hemorrhage. - CT is rapid, widely available, and highly sensitive for detecting acute blood. - It helps identify location, size, mass effect, and associated injuries like skull fractures. - MRI has limited role in acute settings but is useful for subacute/chronic hemorrhage and detecting diffuse axonal injury.
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