Clinical Anatomy — MCQs
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Which structure can be palpated through the anterior wall of the rectum, directly in front of the rectum in the midline, during a rectal examination of a 27-year-old woman?
Through which route does prostate cancer primarily spread to the vertebral column?
Most commonly utilized intercostal space for pericardiocentesis is:
Liver biopsy is performed through the 8th intercostal space at the midaxillary line to avoid injury to which structure?
All of the following are boundaries of Trautman's triangle except:
In an infant, bone marrow biopsy is typically done from which site?
Clinical Anatomy Indian Medical PG Practice Questions and MCQs
Question 141: Which structure can be palpated through the anterior wall of the rectum, directly in front of the rectum in the midline, during a rectal examination of a 27-year-old woman?
- A. Bladder
- B. Body of uterus
- C. Cervix of uterus (Correct Answer)
- D. Pubic symphysis
Explanation: Cervix of uterus - The cervix is located posterior to the bladder and inferior to the body of the uterus, making it palpable through the anterior rectal wall via the rectovaginal septum [2]. - Its firm, rounded structure can be felt as a distinct nodule directly anterior to the rectum in the midline during a digital rectal examination. - This is a standard clinical finding in pelvic examination. Bladder - The bladder is anterior to the uterus and cervix; an empty bladder is usually not palpable through the anterior rectal wall. - A distended bladder would be palpable, but it would be a soft, fluctuating mass, not a firm structure like the cervix. Body of uterus - The body of the uterus is superior to the cervix and in the typical anteverted position (normal in ~80% of women), it is angled anteriorly and superiorly, generally beyond the reach of a digital rectal exam for direct palpation through the anterior rectal wall [1]. - In the less common retroverted uterus, the body may be palpable through the posterior fornix of the vagina or through the rectum, but this is not the typical anatomical relationship. Pubic symphysis - The pubic symphysis is a bony joint located at the very anterior aspect of the pelvis, far too anterior and superior to be palpable through the anterior wall of the rectum. - It forms the anterior boundary of the bony pelvis, while the rectum is situated posteriorly within the pelvic cavity.
Question 142: Through which route does prostate cancer primarily spread to the vertebral column?
- A. None of the options
- B. Batson plexus (Correct Answer)
- C. Inferior hypogastric plexus
- D. Superior hypogastric plexus
Explanation: Batson plexus - The Batson plexus is a valveless network of veins that connects the deep pelvic veins (including those draining the prostate) to the internal vertebral venous plexuses. - The absence of valves in this plexus allows for the retrograde flow of tumor cells, facilitating the direct spread of prostate cancer to the vertebral column and other bones without passing through the pulmonary circulation. Inferior hypogastric plexus - The inferior hypogastric plexus is a nerve plexus containing sympathetic and parasympathetic fibers, primarily involved in innervating pelvic organs. - It is a neural structure, not a vascular pathway, and therefore does not play a direct role in the hematogenous spread of cancer cells. Superior hypogastric plexus - The superior hypogastric plexus is also a nerve plexus, located anterior to the sacral promontory, involved in autonomic innervation of pelvic organs. - Like the inferior hypogastric plexus, it is a neural structure and not a venous pathway for metastatic spread of cancer. None of the options - This option is incorrect because the Batson plexus is a well-established and critically important route for the metastatic spread of prostate cancer to the vertebral column. - The involvement of this valveless venous system is a hallmark in understanding the predilection of prostate cancer for bone metastases.
Question 143: Most commonly utilized intercostal space for pericardiocentesis is:
- A. Left 5th Intercostal Space (Correct Answer)
- B. Left 6th Intercostal Space
- C. Right 5th Intercostal Space
- D. Right 6th Intercostal Space
Explanation: ***Left 5th Intercostal Space*** - This is the most commonly utilized **intercostal space** for pericardiocentesis when an intercostal approach is chosen. - The needle is inserted at the **left 5th intercostal space, just lateral to the left sternal border** (parasternal line). - This location provides direct access to the **pericardial sac** while minimizing risks to the lungs, internal mammary artery, and other vital structures. - The needle is advanced posteriorly and medially toward the pericardial space. *Left 6th Intercostal Space* - While sometimes used, the **6th intercostal space** is generally considered less optimal than the 5th space. - The lower position increases the risk of diaphragmatic injury or inadvertent entry into the abdominal cavity. - The 5th intercostal space provides a more direct angle to the pericardial sac. *Right 5th Intercostal Space* - The right side is typically avoided for pericardiocentesis due to the anterior position of the **right ventricle** on the right side of the chest. - This increases the risk of **ventricular puncture** and cardiac injury. - The left-sided approach is anatomically safer. *Right 6th Intercostal Space* - Similar to the right 5th intercostal space, the right-sided approach carries higher risk of complications. - The proximity to the **right ventricle** and liver makes this approach less favorable. - It is not a standard route for pericardiocentesis due to increased risk of **iatrogenic injury**.
Question 144: Liver biopsy is performed through the 8th intercostal space at the midaxillary line to avoid injury to which structure?
- A. Lung
- B. Pleural cavity (Correct Answer)
- C. Subdiaphragmatic space
- D. Gall bladder
Explanation: Liver biopsy is performed through the 8th intercostal space at the midaxillary line to avoid injury to which structure? ***Pleural cavity*** - Liver biopsy is performed at the **8th intercostal space at the midaxillary line** during **arrested expiration** to avoid injury to the **pleural cavity containing lung tissue**. - At this level, the **inferior margin of the lung** is typically at or above the 8th rib, retracting further upward during expiration. - The **costodiaphragmatic recess** (the potential space where parietal pleura of the chest wall meets the diaphragmatic pleura) extends down to approximately the **10th intercostal space** at the midaxillary line. [1] - By choosing the 8th intercostal space during expiration, the needle passes through the **apposed pleural membranes** (where no lung parenchyma is present), then through the **diaphragm** directly into the **liver**. - This technique minimizes the risk of **pneumothorax** by avoiding lung tissue while still accessing the liver through the thoracic route. [1] *Lung* - The lung's inferior border at the midaxillary line typically reaches the **8th rib** (or 8th intercostal space), but during **expiration**, it retracts upward. - While avoiding lung injury is important, the specific anatomical landmark used is the **pleural recess** below the lung margin, not the lung itself. [1] - The correct choice of intercostal space ensures the needle trajectory is **below the lung parenchyma**. *Subdiaphragmatic space* - The needle **must pass through** the subdiaphragmatic space to reach the liver; this space is not avoided but rather is part of the intended pathway. - The subdiaphragmatic space contains the liver and is the target region for the biopsy. *Gall bladder* - The gall bladder is located on the **inferior surface of the right lobe of the liver**, typically in a more **anterior and medial position**. - The **midaxillary line** approach at the 8th intercostal space targets the **posterior-lateral aspect** of the liver, well away from the gall bladder. - While avoiding the gall bladder is important to prevent **bile peritonitis**, this is achieved by the **lateral positioning**, not specifically by the choice of the 8th intercostal space.
Question 145: All of the following are boundaries of Trautman's triangle except:
- A. Inferior petrosal sinus (Correct Answer)
- B. Sigmoid sinus
- C. Superior petrosal sinus
- D. Bony labyrinth
Explanation: ***Inferior petrosal sinus*** - The **inferior petrosal sinus** is not a boundary of Trautman's triangle. This triangle is an important surgical landmark in approaches to the **posterior fossa**. - Its boundaries are formed by the **superior petrosal sinus**, the **sigmoid sinus**, and the **bony labyrinth** (specifically the posterior semicircular canal). *Sigmoid sinus* - The **sigmoid sinus** forms one of the key **posterior borders** of Trautman's triangle. - This sinus is a major dural venous sinus that drains into the **internal jugular vein**. *Superior petrosal sinus* - The **superior petrosal sinus** forms the **superior border** of Trautman's triangle. - It runs along the superior border of the petrous part of the temporal bone and drains primarily into the **cavernous sinus**. *Bony labyrinth* - The **bony labyrinth**, specifically the posterior aspect of the petrous bone containing the **posterior semicircular canal**, forms the **anterior boundary** of Trautman's triangle. - This boundary is crucial for identifying the *internal auditory canal* and the *facial and vestibulocochlear nerves*.
Question 146: In an infant, bone marrow biopsy is typically done from which site?
- A. Sternum
- B. Iliac crest
- C. Tibia (Correct Answer)
- D. Posterior superior iliac spine
Explanation: Tibia - The proximal tibia (specifically the anteromedial surface) is the preferred site for bone marrow aspiration and biopsy in infants under 12-18 months of age. - This site provides easy access, has abundant cellular marrow in young infants, and has a flat, accessible surface for needle insertion. - The procedure is safer in infants at this site due to the larger bone surface area relative to body size and lower risk of complications compared to other sites. - As the child grows older (typically after 18-24 months), the tibial marrow becomes less active and the iliac sites become preferred. Posterior superior iliac spine - The PSIS (or posterior iliac crest) becomes the primary site in older children and adults, but is not preferred in infants. - In infants, the iliac crest is small, largely cartilaginous, and difficult to palpate and access safely. - Access requires proper positioning and is technically more challenging in the infant population. Iliac crest - The anterior or posterior iliac crest is commonly used in older children (>2 years) and adults for bone marrow procedures. - In infants, this site presents the same challenges as the PSIS: small size, cartilaginous nature, and difficult anatomical access. - Once the pelvis is adequately ossified (after infancy), the iliac crest becomes the preferred site due to abundant marrow and safety. Sternum - The sternum is avoided in infants and children due to the high risk of penetrating into the mediastinum and potentially injuring vital structures (heart, great vessels). - The thin sternal bone in infants and the proximity of mediastinal organs make this an unsafe site. - Sternal puncture may be used in adults but is contraindicated in pediatric populations.
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