CT Anatomy — MCQs
All of the following statements about spontaneous CSF leak are true, except:
Choose the best method of diagnosis for the clinical sign represented in the image.
IOC for Acute Aortic Dissection in a Clinically Unstable patient is?
Which of the following is not felt with a digital rectal examination?
Which of the following statements about CT imaging is the MOST accurate?
Hounsfield unit is zero for which of the following?
In an ultrasound of the abdomen, which structure is best seen posterior to the stomach?
Which of the following statements about the umbilical cord is incorrect?
Which of the following statements is true about the diaphragm's anatomy?
Haustrations are present in -
CT Anatomy Indian Medical PG Practice Questions and MCQs
Question 1: All of the following statements about spontaneous CSF leak are true, except:
- A. Fluorescin Dye can be used intrathecally for diagnosis of site of leak
- B. MRI (Gadolinium enhanced) T1 images are best for diagnosis of site of leak
- C. Most common site of CSF leak is fovea ethmoidalis (Correct Answer)
- D. Beta 2 transferrin estimation is highly specific for diagnosis
Explanation: ***Most common site of CSF leak is fovea ethmoidalis*** - The **fovea ethmoidalis** is actually the **most common site for iatrogenic injury** during sinus surgery, but is **rarely the source of spontaneous CSF leaks.** - **Spontaneous CSF leaks** typically occur in the **cribriform plate** or the **sphenoid sinus**, usually due to congenital defects or increased intracranial pressure. *Fluorescin Dye can be used intrathecally for diagnosis of site of leak* - **Intrathecal fluorescein** can be used to visually locate the site of a CSF leak during endoscopy. - However, it carries a small risk of **neurotoxicity**, including seizures, and is therefore used cautiously and often diluted. *MRI (Gadolinium enhanced) T1 images are best for diagnosis of site of leak* - **High-resolution CT cisternography** with intrathecal contrast is generally considered the **gold standard** for precisely localizing CSF leaks, especially bony defects. - While MRI can show fluid collections and some dural defects, it is often **less definitive** for pinpointing the exact leak site compared to CT cisternography. *Beta 2 transferrin estimation is highly specific for diagnosis* - **Beta-2 transferrin** is a highly specific marker for CSF, as it is found almost exclusively in CSF, perilymph, and aqueous humor. - Its presence in nasal or ear discharge definitively confirms the fluid as CSF, making it a very reliable diagnostic test.
Question 2: Choose the best method of diagnosis for the clinical sign represented in the image.
- A. Serum copper
- B. Serum ceruloplasmin (Correct Answer)
- C. Karyotyping
- D. PCR
Explanation: ***Serum ceruloplasmin*** - The image shows a **Kayser-Fleischer ring**, a greenish-brown discoloration in the periphery of the cornea, which is pathognomonic for **Wilson's disease**. - **Wilson's disease** is a genetic disorder of copper metabolism characterized by **low serum ceruloplasmin** levels (the primary copper-carrying protein in the blood) and increased copper deposition in various tissues. *Serum copper* - While Wilson's disease involves copper accumulation, **total serum copper** can be normal or even elevated due to widespread tissue damage releasing copper into the circulation, making it an unreliable diagnostic marker on its own. - A low serum copper level can be seen, but it is not as specific as low ceruloplasmin, as much of the copper in serum is bound to ceruloplasmin. *Karyotyping* - **Karyotyping** is used to analyze the number and structure of chromosomes and is primarily indicated for diagnosing chromosomal abnormalities, such as Down syndrome or Turner syndrome. - It is not relevant for diagnosing metabolic disorders like Wilson's disease, which is caused by a mutation in a single gene (ATP7B), not a chromosomal aberration. *PCR* - **PCR (Polymerase Chain Reaction)** is a technique used to amplify DNA sequences and can be used for genetic testing to identify specific mutations. - While genetic testing for the **ATP7B gene** mutation is a confirmatory test for Wilson's disease, it is not the primary or best method for initial diagnosis, especially when classic clinical signs and biochemical markers (like low ceruloplasmin) are present.
Question 3: IOC for Acute Aortic Dissection in a Clinically Unstable patient is?
- A. NCCT
- B. TEE (Correct Answer)
- C. MRI
- D. CT-Angio
Explanation: ***TEE (Transesophageal Echocardiography)*** - **TEE is the investigation of choice** for acute aortic dissection in **hemodynamically unstable patients** due to its **portability and rapidity**. - Can be performed at the **bedside** without transporting the critically ill patient, minimizing risk. - Provides rapid diagnosis (5-10 minutes) with **>95% sensitivity and specificity** for detecting intimal flap and false lumen. - Simultaneously assesses **complications** such as aortic regurgitation, pericardial effusion/tamponade, and ventricular function. - Particularly excellent for visualizing the **ascending aorta** and aortic root. *CT-Angio* - **CT angiography** is the **investigation of choice** for acute aortic dissection in **hemodynamically STABLE patients**. - Provides excellent anatomical detail of the entire aorta, clearly showing the intimal flap, true and false lumens, and branch vessel involvement. - Requires **patient transport** to the radiology department, which is **unsafe in unstable patients**. - Best for comprehensive surgical planning in stable patients. *MRI* - **MRI** offers the highest anatomical detail and is considered the gold standard for **chronic dissection follow-up**. - Its lengthy acquisition time (30-60 minutes) and incompatibility with monitoring equipment make it **unsuitable for acutely unstable patients**. *NCCT* - **Non-contrast CT** may show indirect signs like the **hyperdense crescent sign** in the aortic wall. - Cannot reliably differentiate true and false lumens or assess the full extent of dissection. - Insufficient for definitive diagnosis or management planning.
Question 4: Which of the following is not felt with a digital rectal examination?
- A. Seminal vesicles
- B. Prostate
- C. Rectovesical pouch
- D. Ureter (Correct Answer)
Explanation: ***Ureter*** - The **ureters** are too deep and medially located to be reliably palpated during a **digital rectal examination** (DRE). - They are typically not accessible through the rectal wall due to their anatomical position posterior to the urinary bladder and prostate (in males). *Seminal vesicles* - The **seminal vesicles** are located superior to the prostate and can sometimes be palpated, especially if enlarged or inflamed. - They are adjacent to the posterior surface of the bladder and anterior to the rectum. *Prostate* - The **prostate gland** is directly anterior to the rectum and is the primary structure evaluated during a **DRE**. - Its size, consistency, and any nodules or tenderness can be assessed. *Rectovesical pouch* - The **rectovesical pouch** is the peritoneal reflection between the rectum and the bladder in males. - While not a distinct organ to "feel," pathology within this space (e.g., fluid collections, masses) can sometimes be appreciated as a fullness or mass effect above the prostate via the DRE.
Question 5: Which of the following statements about CT imaging is the MOST accurate?
- A. Water has a Hounsfield unit (HU) of zero. (Correct Answer)
- B. CT head dose remains constant regardless of the protocol used.
- C. CT cannot detect gallstones under any circumstances.
- D. CT uses unfiltered x-ray beams.
Explanation: ***Water has a Hounsfield unit (HU) of zero.*** - The **Hounsfield unit (HU)** scale is a quantitative scale used to describe radiodensity in CT scans, where **water is defined as 0 HU**. - This establishes a crucial reference point for measuring the attenuation of other tissues, which can range from approximately **-1000 HU for air** to **+1000 HU or more for dense bone**. *CT head dose remains constant regardless of the protocol used.* - The **radiation dose** in CT scans is highly variable and depends significantly on the **protocol used**, including factors like mA, kVp, pitch, and scan length. - **Dose optimization techniques** and protocol adjustments are routinely employed to minimize patient exposure while maintaining diagnostic image quality. *CT cannot detect gallstones under any circumstances.* - While **ultrasound (US)** is the primary modality for detecting gallstones, CT can visualize them, especially if they are **calcified** or of mixed composition. - **Non-calcified gallstones** may be more challenging to detect on CT, but they are not impossible to see, particularly with current generation scanners and appropriate windowing. *CT uses unfiltered x-ray beams.* - CT scanners use **filtered x-ray beams** to provide higher quality images and reduce patient dose. - **Filtration (e.g., aluminum or copper)** removes low-energy x-rays, which would otherwise be absorbed by the patient without contributing to image formation.
Question 6: Hounsfield unit is zero for which of the following?
- A. Dense bone
- B. Air
- C. Fat
- D. Water (Correct Answer)
Explanation: ***Water*** - The **Hounsfield Unit (HU)** scale is a quantitative scale used to describe radiodensity in **computed tomography (CT)** scans. - **Water** is defined as having a Hounsfield Unit of **0**, serving as the reference point for the scale. *Dense bone* - **Dense bone** has a very high radiodensity, typically ranging from **+700 to +3000 HU**. - Its high HU value reflects its strong attenuation of X-rays due to its high density and calcium content. *Air* - **Air** has the lowest radiodensity on the Hounsfield scale, typically ranging from **-1000 to -900 HU**. - This negative value indicates that it attenuates X-rays even less than water. *Fat* - **Fat** typically has Hounsfield Units ranging from **-120 to -60 HU**. - This makes it less dense than water but significantly denser than air.
Question 7: In an ultrasound of the abdomen, which structure is best seen posterior to the stomach?
- A. Pancreas (Correct Answer)
- B. Gallbladder
- C. Spleen
- D. Liver
Explanation: ***Pancreas*** - The **pancreas** is retroperitoneal and lies transversely across the posterior abdominal wall, making it located directly posterior to the stomach. - In ultrasound, the stomach, when filled with fluid, can act as an acoustic window to visualize the pancreas behind it. *Gallbladder* - The **gallbladder** is typically nestled in a fossa on the inferior surface of the liver, anterior to the duodenum and often anterior or inferior to the stomach [1]. - It is not positioned directly posterior to the stomach, but rather more to the right and inferior [1]. *Spleen* - The **spleen** is located in the left upper quadrant, superior and posterior to the stomach, but typically more lateral and posterior than directly behind it. - While it has a close relationship with the stomach, it is usually not considered "best seen posterior to the stomach" in the same straight-on fashion as the pancreas. *Liver* - The **liver** is primarily located in the right upper quadrant, largely anterior and superior to the stomach. - While a small portion of the left lobe of the liver can be anterior to the stomach, the bulk of the liver is not posterior to it.
Question 8: Which of the following statements about the umbilical cord is incorrect?
- A. Two arteries and one vein
- B. Contains Wharton's jelly
- C. Typically 50 to 60 cm long
- D. Two veins and one artery (Correct Answer)
Explanation: ***Two veins and one artery*** - This statement is incorrect because the typical umbilical cord contains **two umbilical arteries** and **one umbilical vein**. - **Two veins and one artery** would represent a rare anomaly, often associated with other congenital malformations. *Two arteries and one vein* - This is the **normal anatomical configuration** of the umbilical cord, consisting of **two umbilical arteries** and **one umbilical vein**. - The arteries carry deoxygenated blood and waste products from the fetus to the placenta, while the vein carries oxygenated blood and nutrients from the placenta to the fetus. *Contains Wharton's jelly* - **Wharton's jelly** is a gelatinous substance found within the umbilical cord, surrounding the blood vessels. - Its primary function is to protect the umbilical vessels from compression and knotting, ensuring continuous blood flow. *Typically 50 to 60 cm long* - The average length of a term umbilical cord is indeed between **50 and 60 centimeters**. - Variations in length can occur, with excessively short or long cords potentially leading to obstetric complications.
Question 9: Which of the following statements is true about the diaphragm's anatomy?
- A. The left side of the diaphragm is significantly pushed down by the heart.
- B. The right side of the diaphragm is lower than the left side.
- C. The liver pushes the right side of the diaphragm upward, making it higher than the left side. (Correct Answer)
- D. Hernias are more common on the right side due to structural weaknesses.
Explanation: ***The liver pushes the right side of the diaphragm upward, making it higher than the left side.*** - The **large mass of the liver**, located beneath the right hemidiaphragm, elevates it. - This anatomical arrangement results in the **right dome of the diaphragm** being typically ½ to 1 inch higher than the left. *The left side of the diaphragm is significantly pushed down by the heart.* - While the heart rests on the **central tendon** of the diaphragm, its primary effect is not to significantly push down the left hemidiaphragm to make it lower than the right. - The heart's position influences the central tendon and left dome, but the **liver's position** on the right is the dominant factor in hemidiaphragm height. *Hernias are more common on the right side due to structural weaknesses.* - This statement is **incorrect**; **diaphragmatic hernias**, particularly congenital ones like **Bochdalek hernias**, are actually more common on the **left side** (80-90% of cases). - This left-sided predisposition is due to the **earlier closure of the right pleuroperitoneal canal** during embryological development, making the left side more susceptible to persistent defects. *The right side of the diaphragm is lower than the left side.* - This statement is incorrect; the **right side is typically higher** than the left. - The presence of the **liver** beneath the right hemidiaphragm accounts for this elevated position.
Question 10: Haustrations are present in -
- A. Duodenum
- B. Ileum
- C. Jejunum
- D. Colon (Correct Answer)
Explanation: ***Colon*** - **Haustrations** are characteristic sacculations or pouches that give the colon its segmented appearance [1]. - They are formed by the tonic contractions of the **teniae coli**, which are three distinct bands of longitudinal smooth muscle found in the muscularis externa of the colon. *Duodenum* - The duodenum is the first part of the small intestine and is characterized by **plicae circulares (circular folds)** and **villi**, not haustrations. - Its primary role is chemical digestion and initial absorption, with a smooth, folded inner surface. *Ileum* - The ileum is the final and longest part of the small intestine, featuring **Peyer's patches** (lymphoid nodules) and prominent plicae circulares [2], but lacks haustrations. - Its main function is the absorption of vitamin B12 and bile salts [2]. *Jejunum* - The jejunum is the middle section of the small intestine, known for its tall and numerous **plicae circulares** and villi, making it highly efficient for nutrient absorption. - It does not possess haustrations, which are unique to the large intestine.
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