Initial diagnostic workup approach US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Initial diagnostic workup approach. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Initial diagnostic workup approach US Medical PG Question 1: A 65-year-old man is brought to the emergency department from his home. He is unresponsive. His son requested a wellness check because he had not heard from his father in 2 weeks. He reports that his father was sounding depressed during a telephone call. The paramedics found a suicide note and a half-empty bottle of antifreeze near the patient. The medical history includes hypertension and hyperlipidemia. The vital signs include: blood pressure 120/80 mm Hg, respiratory rate 25/min, heart rate 95/min, and temperature 37.0°C (98.5°F). He is admitted to the hospital. What do you expect the blood gas analysis to show?
- A. Non-anion gap metabolic acidosis
- B. Metabolic alkalosis
- C. Respiratory acidosis
- D. Anion gap metabolic acidosis (Correct Answer)
- E. Mixed acid-base disorder
Initial diagnostic workup approach Explanation: ***Anion gap metabolic acidosis***
- The patient's history of **antifreeze ingestion** indicates likely exposure to **ethylene glycol**, which is metabolized into toxic acids (glycolic and oxalic acid).
- These accumulating acids lead to an **increased anion gap metabolic acidosis**.
*Non-anion gap metabolic acidosis*
- This type of acidosis typically results from **bicarbonate loss** (e.g., severe diarrhea) or **excessive chloride intake**, which is not indicated by the antifreeze ingestion.
- It involves a normal anion gap because other unmeasured anions do not accumulate.
*Metabolic alkalosis*
- This imbalance is characterized by an **increase in bicarbonate** or a significant loss of acid, often due to vomiting or diuretic use.
- Antifreeze poisoning directly leads to acid accumulation, precisely the opposite of metabolic alkalosis.
*Respiratory acidosis*
- This occurs due to **hypoventilation** and subsequent buildup of CO2, leading to increased carbonic acid.
- While respiratory rate is elevated, the primary problem here is metabolic due to toxin ingestion, not respiratory CO2 retention.
*Mixed acid-base disorder*
- While a mixed disorder is possible in complex cases, the presentation with antifreeze poisoning is classically dominated by a **severe anion gap metabolic acidosis**.
- There is no clear indication of a separate primary respiratory or alkalotic disorder at onset to warrant a "mixed" label as the primary anticipated finding.
Initial diagnostic workup approach US Medical PG Question 2: A 36-year-old male is taken to the emergency room after jumping from a building. Bilateral fractures to the femur were stabilized at the scene by emergency medical technicians. The patient is lucid upon questioning and his vitals are stable. Pain only at his hips was elicited. Cervical exam was not performed. What is the best imaging study for this patient?
- A. AP and lateral radiographs of hips
- B. Lateral radiograph (x-ray) of hips
- C. Magnetic resonance imaging (MRI) of hips, knees, lumbar, and cervical area
- D. Anterior-posterior (AP) and lateral radiographs of hips, knees, lumbar, and cervical area
- E. Computed tomography (CT) scan of cervical spine, hips, and lumbar area (Correct Answer)
Initial diagnostic workup approach Explanation: ***Computed tomography (CT) scan of cervical spine, hips, and lumbar area***
- In **high-energy trauma** (fall from height), a CT scan is the **gold standard** for evaluating the **spine and pelvis**, providing detailed cross-sectional images superior to plain radiographs.
- Since the **cervical exam was not performed**, cervical spine imaging is **mandatory** per ATLS (Advanced Trauma Life Support) protocols. High-energy falls carry significant risk of **cervical spine injury** even without obvious neurological symptoms.
- CT allows comprehensive assessment of **hip fractures, pelvic injuries, and the entire spine** (cervical, thoracic, lumbar), identifying both obvious and **subtle fractures** that may be missed on plain films.
- This approach provides the most **efficient and thorough evaluation** in the acute trauma setting, allowing for appropriate surgical planning and ruling out life-threatening spinal instability.
*AP and lateral radiographs of hips*
- Plain radiographs provide **limited detail** and may **miss subtle fractures**, particularly in complex areas like the pelvis and acetabulum.
- This option **fails to address cervical spine clearance**, which is essential in all high-energy trauma patients, especially when cervical exam has not been performed.
- Radiographs are insufficient for **comprehensive trauma evaluation** after a fall from height.
*Lateral radiograph (x-ray) of hips*
- A single lateral view is **grossly insufficient** for evaluating hip and pelvic fractures, providing only a **two-dimensional perspective** that can miss significant injuries.
- This option **completely neglects spinal evaluation**, which is dangerous in an uncleared trauma patient with a high-energy mechanism.
*Magnetic resonance imaging (MRI) of hips, knees, lumbar, and cervical area*
- While MRI excels at evaluating **soft tissues, ligaments, and bone marrow**, it is **not the initial imaging modality** for acute bony trauma due to longer scan times and lower sensitivity for acute fractures compared to CT.
- MRI is **time-consuming and impractical** in the emergency setting for initial fracture assessment, potentially delaying definitive treatment.
- CT is superior for evaluating **acute skeletal injuries** in the trauma bay.
*Anterior-posterior (AP) and lateral radiographs of hips, knees, lumbar, and cervical area*
- Multiple plain radiographs have **limited sensitivity** for complex or non-displaced fractures, particularly in the **spine and pelvis**, making them inadequate for high-energy trauma evaluation.
- Obtaining multiple radiographic views requires **numerous patient repositionings**, which risks further injury if **spinal instability** is present.
- Plain films provide significantly **less diagnostic information** than CT scanning for trauma assessment.
Initial diagnostic workup approach US Medical PG Question 3: A 58-year-old man presents to the emergency department with a chief complaint of ringing in his ears that started several hours previously that has progressed to confusion. The patient denies any history of medical problems except for bilateral knee arthritis. He was recently seen by an orthopedic surgeon to evaluate his bilateral knee arthritis but has opted to not undergo knee replacement and prefers medical management. His wife noted that prior to them going on a hike today, he seemed confused and not himself. They decided to stay home, and roughly 14 hours later, he was no longer making any sense. Physical exam is notable for a confused man. The patient's vitals are being performed and his labs are being drawn. Which of the following is most likely to be seen on blood gas analysis?
- A. pH: 7.30, PaCO2: 15 mmHg, HCO3-: 16 mEq/L (Correct Answer)
- B. pH: 7.37, PaCO2: 41 mmHg, HCO3-: 12 mEq/L
- C. pH: 7.41, PaCO2: 65 mmHg, HCO3-: 34 mEq/L
- D. pH: 7.47, PaCO2: 11 mmHg, HCO3-: 24 mEq/L
- E. pH: 7.31, PaCO2: 31 mmHg, HCO3-: 15 mEq/L
Initial diagnostic workup approach Explanation: ***pH: 7.30, PaCO2: 15 mmHg, HCO3-: 16 mEq/L***
- This blood gas analysis shows a **low pH** (acidemia), **low PaCO2** (hypocapnia), and **low HCO3-** (bicarbonate). This pattern is consistent with a **primary metabolic acidosis** with a **compensatory respiratory alkalosis**.
- In this clinical scenario, the patient likely has **salicylate toxicity** (aspirin poisoning). Salicylate toxicity initially causes respiratory alkalosis due to direct stimulation of the respiratory center, followed by a high anion gap metabolic acidosis as salicylates interfere with cellular metabolism. This specific ABG reflects a mixed disorder where metabolic acidosis is predominant and respiratory compensation is attempting to raise the pH. The **tinnitus** and **confusion** are classic symptoms of salicylate toxicity.
*pH: 7.37, PaCO2: 41 mmHg, HCO3-: 12 mEq/L*
- This blood gas shows a **normal pH**, **normal PaCO2**, and **low HCO3-**. This suggests a **compensated metabolic acidosis**, where the body has fully compensated to bring the pH back to normal.
- While the patient likely has metabolic acidosis from salicylate toxicity, full compensation to a normal pH is less characteristic of an acute, severe presentation with significant neurological symptoms.
*pH: 7.41, PaCO2: 65 mmHg, HCO3-: 34 mEq/L*
- This blood gas shows a **normal pH**, **high PaCO2**, and **high HCO3-**. This indicates a **compensated respiratory acidosis**, where the kidneys have compensated for chronic CO2 retention.
- This pattern is not consistent with salicylate toxicity, which typically causes **respiratory alkalosis** early on, and later **metabolic acidosis**.
*pH: 7.47, PaCO2: 11 mmHg, HCO3-: 24 mEq/L*
- This blood gas analysis shows a **high pH** (alkalemia), **very low PaCO2** (severe hypocapnia), and a **normal HCO3-**. This indicates a **primary respiratory alkalosis** with no significant metabolic compensation.
- While salicylate toxicity can cause respiratory alkalosis, severe confusion and the progression of symptoms suggest a more advanced stage, usually involving a metabolic acidosis component, making a pure, uncompensated respiratory alkalosis less likely.
*pH: 7.31, PaCO2: 31 mmHg, HCO3-: 15 mEq/L*
- This blood gas shows a **low pH**, **low PaCO2**, and **low HCO3-**. This also indicates a **metabolic acidosis** with **respiratory compensation**.
- However, compared to pH 7.30, PaCO2 15 mmHg, and HCO3- 16 mEq/L, this option shows slightly **less severe respiratory compensation** (PaCO2 is higher), which is less typical for the profound respiratory stimulation seen in severe salicylate poisoning. The chosen correct option demonstrates a more characteristic and maximal respiratory compensation for the degree of metabolic acidosis.
Initial diagnostic workup approach US Medical PG Question 4: A mother presents to the family physician with her 16-year-old son. She explains, "There's something wrong with him doc. His grades are getting worse, he's cutting class, he's gaining weight, and his eyes are often bloodshot." Upon interviewing the patient apart from his mother, he seems withdrawn and angry at times when probed about his social history. The patient denies abuse and sexual history. What initial test should be sent to rule out the most likely culprit of this patient's behavior?
- A. Complete blood count
- B. Sexually transmitted infection (STI) testing
- C. Blood culture
- D. Urine toxicology screen (Correct Answer)
- E. Slit lamp examination
Initial diagnostic workup approach Explanation: ***Urine toxicology screen***
- The patient's presentation with **declining grades**, **cutting class**, **weight gain**, **bloodshot eyes**, and **irritability** are classic signs of **substance abuse** in an adolescent.
- A **urine toxicology screen** is the most appropriate initial test to detect common illicit substances, especially given the clear signs pointing towards drug use.
*Slit lamp examination*
- This test is used to examine the **anterior segment of the eye**, including the conjunctiva, cornea, iris, and lens.
- While the patient has **bloodshot eyes**, this specific test would be more relevant for ruling out ocular infections or injuries, not for diagnosing the underlying cause of systemic behavioral changes.
*Complete blood count*
- A **complete blood count (CBC)** measures different components of the blood, such as red blood cells, white blood cells, and platelets.
- A CBC is a general health indicator and while it can detect infections or anemia, it is not specific or sensitive enough to identify the cause of the behavioral changes described.
*Sexually transmitted infection (STI) testing*
- Although the patient denies sexual history, all adolescents presenting with certain risk factors or symptoms may warrant STI testing in a broader health assessment.
- However, in this scenario, the primary cluster of symptoms (poor grades, cutting class, bloodshot eyes, irritability) points more directly to substance abuse than to an STI.
*Blood culture*
- A **blood culture** is used to detect the presence of bacteria or other microorganisms in the bloodstream, indicating a systemic infection (sepsis).
- The patient's symptoms are not indicative of an acute bacterial bloodstream infection, and a blood culture would not be the initial test for the presented behavioral changes.
Initial diagnostic workup approach US Medical PG Question 5: An investigator is studying muscle tissue in high-performance athletes. He obtains blood samples from athletes before and after a workout session consisting of short, fast sprints. Which of the following findings is most likely upon evaluation of blood obtained after the workout session?
- A. Decreased concentration of NADH
- B. Increased concentration of H+ (Correct Answer)
- C. Decreased concentration of lactate
- D. Increased concentration of insulin
- E. Increased concentration of ATP
Initial diagnostic workup approach Explanation: ***Increased concentration of H+***
- During **anaerobic metabolism** in high-intensity exercise like sprints, pyruvate is converted to **lactate** by **lactate dehydrogenase** to regenerate NAD+. This process produces H+, leading to a decrease in pH and an increase in H+ concentration in the blood.
- The accumulation of **hydrogen ions (H+)** contributes to metabolic acidosis, muscle fatigue, and the burning sensation experienced during intense exertion.
- Blood gas analysis would show **decreased pH** and **increased H+ concentration**.
*Decreased concentration of NADH*
- NADH is primarily an **intracellular metabolite** and is not typically measured in blood samples as it does not circulate freely in significant concentrations.
- Within muscle cells during anaerobic glycolysis, NADH is consumed by lactate dehydrogenase to convert pyruvate to lactate, regenerating NAD+ for continued glycolysis.
- This option is not a realistic blood finding from a clinical laboratory perspective.
*Decreased concentration of lactate*
- **High-intensity sprints** primarily rely on **anaerobic metabolism**, which rapidly produces **lactate** from pyruvate.
- Therefore, the concentration of lactate in the blood would significantly **increase** after such a workout, not decrease.
- Elevated blood lactate is a hallmark finding after intense anaerobic exercise.
*Increased concentration of insulin*
- **Insulin** levels typically **decrease** during exercise, especially high-intensity exercise, due to **sympathetic nervous system activation** and the body's need to mobilize glucose from liver glycogen and fatty acids.
- Exercise promotes glucose uptake through **insulin-independent mechanisms** (GLUT4 translocation via AMP-activated protein kinase).
- Increased insulin would be counterproductive during intense exercise when glucose mobilization is needed.
*Increased concentration of ATP*
- ATP does not circulate in blood in measurable concentrations as a typical laboratory finding.
- Within muscle cells, ATP is rapidly **consumed** during intense exercise to fuel muscle contraction.
- While cells work to maintain ATP levels through anaerobic glycolysis and the creatine phosphate system, net ATP does not accumulate in the blood.
Initial diagnostic workup approach US Medical PG Question 6: A 24-year-old woman presents to the emergency department for evaluation of lower abdominal pain. She endorses 6 hours of progressively worsening pain. She denies any significant past medical history and her physical examination is positive for non-specific, diffuse pelvic discomfort. She denies the possibility of pregnancy given her consistent use of condoms with her partner. The vital signs are: blood pressure, 111/68 mm Hg; pulse, 71/min; and respiratory rate, 15/min. She is afebrile. Which of the following is the next best step in her management?
- A. Surgical consultation
- B. Admission and observation
- C. Obtain a pelvic ultrasound
- D. Serum hCG (Correct Answer)
- E. Abdominal CT scan
Initial diagnostic workup approach Explanation: ***Serum hCG***
- Despite the patient's claim of consistent condom use, **pregnancy must be ruled out** in any woman of reproductive age presenting with lower abdominal pain. **Ectopic pregnancy** is a life-threatening condition that can present this way.
- A **serum hCG** is more sensitive than a urine test and can detect very early pregnancies, which is crucial for prompt diagnosis and management.
*Surgical consultation*
- Surgical consultation would be premature without a definitive diagnosis or clear signs of an acute surgical abdomen, such as peritonitis or hemodynamic instability.
- Initial diagnostic steps are necessary to identify the cause of the pain before considering surgical intervention.
*Admission and observation*
- While observation might be necessary, it's not the immediate next best step. Without a diagnosis, observation alone may delay critical interventions for conditions like ectopic pregnancy.
- Admission for observation typically follows initial diagnostic workup when the diagnosis is uncertain but not immediately life-threatening.
*Obtain a pelvic ultrasound*
- A pelvic ultrasound is an important diagnostic tool for evaluating pelvic pain, but it should be performed only **after pregnancy has been ruled out** or confirmed.
- If the patient is pregnant, a pelvic ultrasound would be used to assess for intrauterine or ectopic pregnancy. If she is not pregnant, the ultrasound would help identify other gynecological causes of pain.
*Abdominal CT scan*
- An abdominal CT scan is less specific for gynecological causes of pain and exposes the patient to **ionizing radiation**, making it a less ideal initial step compared to ruling out pregnancy.
- It might be considered if the initial workup for gynecological causes is negative or if there are concerns for other intra-abdominal pathology.
Initial diagnostic workup approach US Medical PG Question 7: A trauma 'huddle' is called. Morphine is administered for pain. Low-flow oxygen is begun. A traumatic diaphragmatic rupture is suspected. Infusion of 0.9% saline is begun. Which of the following is the most appropriate next step in management?
- A. Chest fluoroscopy
- B. Barium study
- C. CT of the chest, abdomen, and pelvis (Correct Answer)
- D. MRI chest and abdomen
- E. ICU admission and observation
Initial diagnostic workup approach Explanation: ***CT of the chest, abdomen, and pelvis***
- A suspected **traumatic diaphragmatic rupture** requires a comprehensive imaging study to assess the diaphragm, surrounding organs, and potential associated injuries.
- **CT scan** of the chest, abdomen, and pelvis provides detailed anatomical information, can identify herniated abdominal contents, and is essential for surgical planning in trauma settings.
*Chest fluoroscopy*
- While fluoroscopy can detect diaphragmatic motion, it is **less sensitive** for identifying tears or herniated contents in the **acute trauma setting**.
- It does not provide the comprehensive view of surrounding organs and associated injuries often needed in trauma.
*Barium study*
- A barium study is primarily used to evaluate the **gastrointestinal tract**, but it is generally **not the initial imaging modality** for diaphragmatic rupture due to its limited ability to visualize the diaphragm itself or other solid organ injuries.
- It would be performed after suspicion is increased or for very specific indications, not as a primary diagnostic tool.
*MRI chest and abdomen*
- While MRI offers excellent soft tissue contrast, its use in **acute trauma** is limited by **longer acquisition times**, potential contraindications with metallic implants (though less common in acute trauma), and lower availability compared to CT.
- CT remains the **gold standard** for rapid, comprehensive imaging in unstable trauma patients.
*ICU admission and observation*
- While observation in the ICU is important for monitoring and supportive care, it is **not the next step for diagnosis** of a suspected diaphragmatic rupture.
- Definitive diagnosis through imaging (CT) is crucial before determining specific management strategies, including potential surgical intervention.
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