Lower abdominal cross-sections US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Lower abdominal cross-sections. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Lower abdominal cross-sections US Medical PG Question 1: During a surgical procedure to repair an abdominal aortic aneurysm, the surgeon must be careful to avoid injury to which of the following arterial structures that originates near the level of the renal vessels?
- A. Left renal artery (Correct Answer)
- B. Celiac trunk
- C. Right renal artery
- D. Superior mesenteric artery
Lower abdominal cross-sections Explanation: ***Left renal artery***
- The **left renal artery** arises from the aorta usually just below the superior mesenteric artery, making it susceptible to injury during an **abdominal aortic aneurysm (AAA) repair** if the aneurysm extends proximally.
- Its proximity to the typical location of AAA, often near or involving the **infrarenal aorta**, necessitates careful identification and protection during clamping or graft placement.
*Celiac trunk*
- The **celiac trunk** originates higher up from the aorta, typically at the level of **T12-L1 vertebrae**, well above the common infrarenal AAA repair site.
- While important, it is generally less directly threatened during a typical infrarenal AAA repair compared to arteries immediately adjacent to or within the aneurysm sac.
*Right renal artery*
- The **right renal artery** also originates from the aorta near the level of the renal veins, but it is typically located more posteriorly and usually passes behind the inferior vena cava.
- Although it can be at risk, the left renal artery's course is often more anterior and directly in the field of dissection for the **aortic neck** during AAA repair.
*Superior mesenteric artery*
- The **superior mesenteric artery (SMA)** originates from the aorta proximal to the renal arteries, typically around the L1 vertebral level.
- While crucial, its origin is usually cephalad to the infrarenal aneurysm neck, making it generally less prone to direct injury during infrarenal AAA repair, though flow must be monitored.
Lower abdominal cross-sections US Medical PG Question 2: A 51-year-old woman comes to the physician because of progressively worsening lower back pain. The pain radiates down the right leg to the lateral side of the foot. She has had no trauma, urinary incontinence, or fever. An MRI of the lumbar spine shows disc degeneration and herniation at the level of L5–S1. Which of the following is the most likely finding on physical examination?
- A. Difficulty walking on heels
- B. Exaggerated patellar tendon reflex
- C. Diminished sensation of the anus and genitalia
- D. Diminished sensation of the anterior lateral thigh
- E. Weak Achilles tendon reflex (Correct Answer)
Lower abdominal cross-sections Explanation: ***Weak Achilles tendon reflex***
- A herniated disc at **L5-S1** typically compresses the **S1 nerve root**, which is responsible for the **Achilles tendon reflex**.
- **S1 radiculopathy** presents with weakness in plantarflexion, diminished or absent Achilles reflex, and sensory loss in the **lateral foot** (matching the patient's symptoms).
*Difficulty walking on heels*
- Difficulty walking on heels (**dorsiflexion weakness**) is primarily associated with **L4-L5 disc herniation** compressing the **L5 nerve root**.
- This symptom indicates **L5 radiculopathy**, which affects the tibialis anterior muscle, not S1.
*Exaggerated patellar tendon reflex*
- An exaggerated patellar tendon reflex (**hyperreflexia**) indicates an **upper motor neuron lesion** or spinal cord compression above the lumbar region.
- A disc herniation at **L5-S1** causes a **lower motor neuron lesion** with diminished reflexes, not hyperreflexia.
*Diminished sensation of the anus and genitalia*
- This symptom, along with urinary incontinence and saddle anesthesia, is characteristic of **cauda equina syndrome**, a surgical emergency.
- The patient lacks urinary incontinence and the specific unilateral pain pattern points to isolated **S1 radiculopathy**, not cauda equina syndrome.
*Diminished sensation of the anterior lateral thigh*
- Sensory loss in the **anterior lateral thigh** is associated with compression of the **lateral femoral cutaneous nerve** or **L2-L4 nerve roots**.
- This pattern is not consistent with **L5-S1 disc herniation**, which causes sensory changes in the lateral foot and posterior leg.
Lower abdominal cross-sections US Medical PG Question 3: A child is in the nursery one day after birth. A nurse notices a urine-like discharge being expressed through the umbilical stump. What two structures in the embryo are connected by the structure that failed to obliterate during the embryologic development of this child?
- A. Kidney - large bowel
- B. Liver - umbilical vein
- C. Bladder - small bowel
- D. Pulmonary artery - aorta
- E. Bladder - umbilicus (Correct Answer)
Lower abdominal cross-sections Explanation: ***Bladder - umbilicus***
- A **urine-like discharge** from the umbilical stump indicates a **patent urachus**, which is the embryonic remnant of the allantois.
- The **allantois** (which becomes the urachus) is an embryonic structure that connects the **fetal bladder** to the **umbilicus** during development.
- Normally, the allantois obliterates after birth to form the **median umbilical ligament**, but failure to obliterate results in a patent urachus allowing urine to discharge through the umbilicus.
*Kidney - large bowel*
- These two structures are not directly connected by an obliterating embryonic structure relevant to urine discharge from an umbilical stump.
- The kidneys form urine, and the large bowel is part of the digestive tract, with no direct embryonic communication to the umbilicus for urine expression.
*Liver - umbilical vein*
- The umbilical vein connects the **placenta to the fetal liver** (and ductus venosus) to transport oxygenated blood, not urine.
- Failure of the umbilical vein to obliterate would result in a patent umbilical vein, typically presenting as a vascular anomaly, not urine discharge.
*Pulmonary artery - aorta*
- These structures are connected by the **ductus arteriosus** in fetal circulation, bypassing the pulmonary circulation.
- While important for fetal development, a patent ductus arteriosus (PDA) is a cardiovascular anomaly and would not manifest as urine discharge from the umbilical stump.
*Bladder - small bowel*
- While both structures are involved in waste elimination, there is no normal embryonic structure directly connecting the bladder and small bowel that obliterates to prevent urine discharge from the umbilicus.
- An abnormal connection between the bladder and bowel would typically involve a **fistula** and present with stool in urine or urine in stool, not umbilical discharge.
Lower abdominal cross-sections US Medical PG Question 4: A CT scan of the abdomen reveals a mass in the pancreatic uncinate process. Which of the following structures is most likely to be compressed by this mass?
- A. Common bile duct
- B. Portal vein
- C. Splenic vein
- D. Superior mesenteric vein (Correct Answer)
Lower abdominal cross-sections Explanation: ***Superior mesenteric vein***
- The **uncinate process** of the pancreas hooks around the **superior mesenteric vessels**. Therefore, a mass in this region would most directly compress the **superior mesenteric vein (SMV)** and artery (SMA).
- Compression of the SMV can lead to **venous outflow obstruction** from the small intestine, potentially causing **bowel ischemia** or edema.
*Common bile duct*
- The **common bile duct** passes through the **head of the pancreas**, not typically the uncinate process.
- Compression of the common bile duct would more commonly be associated with masses in the **head of the pancreas**, leading to **jaundice**.
*Portal vein*
- The **portal vein** is formed by the union of the **splenic vein** and the **superior mesenteric vein**, generally posterior to the neck of the pancreas.
- While pancreatic masses can affect the portal vein, a mass specifically in the uncinate process would more directly impinge on the SMV before significantly affecting the main portal vein, which is superior and posterior to the uncinate process.
*Splenic vein*
- The **splenic vein** runs along the **posterior aspect of the body and tail of the pancreas**.
- A mass in the uncinate process, located at the inferior margin of the head, is relatively distant from the splenic vein.
Lower abdominal cross-sections US Medical PG Question 5: A 22-year-old Caucasian male is stabbed in his left flank, injuring his left kidney. As the surgeon undertakes operative repair, she reviews relevant renal anatomy. All of the following are correct regarding the left kidney EXCEPT?
- A. The left kidney has a longer renal vein than the right kidney
- B. The left kidney underlies the left 12th rib
- C. The left kidney moves vertically during deep breathing
- D. The left kidney has a longer renal artery than the right kidney (Correct Answer)
- E. The left kidney lies between T12 and L3
Lower abdominal cross-sections Explanation: ***The left kidney has a longer renal artery than the right kidney***
- The **aorta** lies to the left of the midline, so the **right renal artery** must traverse a greater distance to reach the right kidney.
- Therefore, the right renal artery is longer than the left renal artery.
*The left kidney has a longer renal vein than the right kidney*
- The **inferior vena cava (IVC)** is positioned to the right of the midline, requiring the **left renal vein** to cross the aorta to drain.
- This anatomical arrangement makes the left renal vein longer than the right renal vein.
*The left kidney underlies the left 12th rib*
- The kidneys are retroperitoneal organs, and the 12th rib provides significant posterior protection for **both kidneys**.
- The superior pole of the left kidney typically extends to the level of the **11th and 12th ribs**.
*The left kidney moves vertically during deep breathing*
- The kidneys are surrounded by **perirenal fat** and are influenced by the diaphragm's movement.
- During **deep inspiration**, the diaphragm descends, causing both kidneys to move vertically by 2-3 cm.
*The left kidney lies between T12 and L3*
- The kidneys are situated in the retroperitoneum, generally extending from the level of the **T12 vertebra** to the **L3 vertebra**.
- The left kidney is typically positioned slightly higher than the right kidney.
Lower abdominal cross-sections US Medical PG Question 6: A 57-year-old woman comes to the physician because of several years of recurrent pelvic pain and constipation. She has increased fecal urgency and a sensation of incomplete evacuation following defecation. She has had no problems associated with urination. Her last menstrual period was 6 years ago. She has had three uncomplicated vaginal deliveries. Physical examination shows normal external genitalia. Speculum examination of the vagina and the cervix shows bulging of the posterior vaginal wall during Valsalva maneuver. Weakness of which of the following structures is the most likely cause of this patient's symptoms?
- A. Cardinal ligament
- B. Uterosacral ligament
- C. Bulbospongiosus muscle
- D. Pubocervical fascia
- E. Rectovaginal fascia (Correct Answer)
Lower abdominal cross-sections Explanation: ***Rectovaginal fascia***
- The patient's symptoms of recurrent pelvic pain, constipation, increased fecal urgency, and incomplete evacuation, along with **posterior vaginal wall bulging** during Valsalva, are classic signs of a **rectocele**.
- A rectocele results from the weakening or tearing of the **rectovaginal fascia** (also known as the rectovaginal septum), which normally separates the rectum from the vagina and provides support.
*Cardinal ligament*
- The **cardinal ligament** (transverse cervical ligament) primarily provides support to the **cervix and uterus**, preventing uterine prolapse.
- While pelvic organ prolapse is possible, weakness of the cardinal ligament would typically manifest as **uterine prolapse** or anterior vaginal wall bulging (cystocele), not posterior vaginal bulging related to bowel symptoms.
*Uterosacral ligament*
- The **uterosacral ligaments** originate from the cervix and insert into the sacrum, primarily supporting the **uterus and upper vagina**.
- Weakness in these ligaments can contribute to **uterine prolapse** and some forms of vault prolapse after hysterectomy, which are not the primary issues described here.
*Bulbospongiosus muscle*
- The **bulbospongiosus muscle** is part of the superficial perineal pouch and surrounds the vaginal and urethral openings, contributing to **clitoral erection** and tightening the vaginal introitus.
- Weakness of this muscle is not directly associated with rectocele formation or the specific bowel symptoms reported by the patient.
*Pubocervical fascia*
- The **pubocervical fascia** supports the **bladder and urethra**, separating them from the vagina from the front.
- Weakness in this fascia leads to a **cystocele** (prolapse of the bladder into the vagina), which would typically cause urinary symptoms like stress incontinence, not bowel symptoms and posterior vaginal bulging.
Lower abdominal cross-sections US Medical PG Question 7: An MRI of a patient with low back pain reveals compression of the L5 nerve root. Which of the following muscles would most likely show weakness during physical examination?
- A. Tibialis posterior
- B. Tibialis anterior (Correct Answer)
- C. Gastrocnemius
- D. Quadriceps femoris
Lower abdominal cross-sections Explanation: ***Tibialis anterior***
- The **L5 nerve root** primarily innervates muscles responsible for **dorsiflexion** of the foot, with the **tibialis anterior** being the primary dorsiflexor.
- Weakness of the tibialis anterior would manifest as difficulty lifting the front of the foot, potentially leading to a **foot drop** gait.
*Tibialis posterior*
- The **tibialis posterior** is primarily innervated by the **tibial nerve** (S1-S2) and is responsible for **plantarflexion** and **inversion** of the foot.
- Weakness in this muscle would not be the most likely presentation of L5 nerve root compression.
*Gastrocnemius*
- The **gastrocnemius** muscle is primarily innervated by the **tibial nerve** (S1-S2) and is a powerful **plantarflexor** of the foot.
- Weakness in this muscle would indicate an S1 or S2 nerve root issue, not typically L5.
*Quadriceps femoris*
- The **quadriceps femoris** is innervated by the **femoral nerve**, predominantly originating from the **L2, L3, and L4 nerve roots**.
- Weakness would manifest as difficulty extending the knee, which is not characteristic of L5 compression.
Lower abdominal cross-sections US Medical PG Question 8: A 72-year-old male presents to a cardiac surgeon for evaluation of severe aortic stenosis. He has experienced worsening dyspnea with exertion over the past year. The patient also has a history of poorly controlled hypertension, diabetes mellitus, and hyperlipidemia. An echocardiogram revealed a thickened calcified aortic valve. The surgeon is worried that the patient will be a poor candidate for open heart surgery and decides to perform a less invasive transcatheter aortic valve replacement. In order to perform this procedure, the surgeon must first identify the femoral pulse just inferior to the inguinal ligament and insert a catheter into the vessel in order to gain access to the arterial system. Which of the following structures is immediately lateral to this structure?
- A. Lymphatic vessels
- B. Femoral vein
- C. Sartorius muscle
- D. Pectineus muscle
- E. Femoral nerve (Correct Answer)
Lower abdominal cross-sections Explanation: ***Femoral nerve***
- The **femoral nerve** lies lateral to the **femoral artery** within the **femoral triangle**.
- The order of structures from **lateral to medial** under the inguinal ligament is remembered by the mnemonic **NAVEL**: **N**erve, **A**rtery, **V**ein, **E**mpty space, **L**ymphatics.
*Lymphatic vessels*
- **Lymphatic vessels** and nodes are located most medially within the femoral triangle, medial to the femoral vein.
- This position is not immediately lateral to the femoral artery.
*Femoral vein*
- The **femoral vein** is located immediately medial to the **femoral artery**.
- It would not be found immediately lateral to the femoral artery.
*Sartorius muscle*
- The **sartorius muscle** forms the lateral boundary of the **femoral triangle** but is not immediately adjacent and lateral to the femoral artery within the triangle itself.
- The femoral nerve is enclosed within the iliopsoas fascial compartment, which runs deep to the sartorius.
*Pectineus muscle*
- The **pectineus muscle** forms part of the floor of the **femoral triangle**, but it is deep to the neurovascular structures.
- It is not immediately lateral to the femoral artery.
Lower abdominal cross-sections US Medical PG Question 9: A 12-year-old boy is brought to the emergency room by his mother with complaints of abdominal pain and fever that started 24 hours ago. On further questioning, the mother says that her son vomited twice and has constipation that started approximately 1 and one-half days ago. The medical history is benign. The vital signs are as follows: heart rate 103/min, respiratory rate of 20/min, temperature 38.7°C (101.66°F), and blood pressure 109/69 mm Hg. On physical examination, there is severe right lower quadrant abdominal tenderness on palpation. Which of the following is the most likely cause for this patient’s symptoms?
- A. Luminal obstruction due to a fecalith (Correct Answer)
- B. Ascending infection of the urinary tract
- C. Telescoping of bowel segment causing intestinal obstruction
- D. Twisting of testes on its axis, hampering the blood supply
- E. Immune-mediated vasculitis associated with IgA deposition
Lower abdominal cross-sections Explanation: ***Luminal obstruction due to a fecalith***
- The classic presentation of **appendicitis** in a 12-year-old boy, including **abdominal pain**, fever, vomiting, constipation, and **right lower quadrant tenderness**, is most commonly caused by **luminal obstruction** due to a **fecalith**.
- This obstruction leads to inflammation, bacterial overgrowth, and edema of the appendix, resulting in the described symptoms.
- Other causes of appendiceal luminal obstruction include **lymphoid hyperplasia** and, less commonly, parasites or tumors.
*Ascending infection of the urinary tract*
- While urinary tract infections (UTIs) can cause fever and abdominal pain, the **severe, localized right lower quadrant tenderness** and specific progression of symptoms (vomiting, constipation) are less typical than for appendicitis.
- UTIs are usually associated with **dysuria, frequency, and urgency**, which are not mentioned here.
*Telescoping of bowel segment causing intestinal obstruction*
- This describes **intussusception**, which typically presents in **younger children (6 months to 3 years)** with **colicky abdominal pain**, vomiting, and **currant jelly stools**.
- While it can cause abdominal pain and vomiting, the **age of the patient**, **localized right lower quadrant tenderness**, and absence of classic signs make appendicitis more likely.
*Twisting of testes on its axis, hampering the blood supply*
- This describes **testicular torsion**, which presents with **sudden, severe scrotal pain**, swelling, and tenderness, sometimes with referred abdominal pain.
- The primary complaint of **abdominal pain** with associated vomiting, fever, and right lower quadrant tenderness makes appendicitis a more likely diagnosis.
*Immune-mediated vasculitis associated with IgA deposition*
- This refers to **Henoch-Schönlein purpura (HSP)**, which typically presents with a **palpable purpuric rash** on the lower extremities and buttocks, **arthralgia**, abdominal pain, and sometimes renal involvement.
- The absence of a rash and key features of HSP makes this diagnosis less likely than appendicitis.
Lower abdominal cross-sections US Medical PG Question 10: A 16-year-old boy presents to the emergency department with abdominal pain and tenderness. The pain began approximately 2 days ago in the area just above his umbilicus and was crampy in nature. Earlier this morning, the pain moved laterally to his right lower abdomen. At that time, the pain in the right lower quadrant became severe and constant and woke him up from sleep. He decided to come to the hospital. The patient is nauseous and had a low-grade fever of 37.8°C (100.1°F). Other vitals are normal. Upon physical examination, the patient has rebound tenderness but a negative psoas sign while the remaining areas of his abdomen are non-tender. His rectal exam is normal. Laboratory tests show a white cell count of 15,000/mm3. Urinalysis and other laboratory findings were negative. What conclusion can be drawn about the nerves involved in the transmission of this patient’s pain during the physical exam?
- A. His pain is transmitted bilaterally by somatic afferent nerve fibers of the abdomen.
- B. His pain is transmitted by somatic afferent nerve fibers located in the right flank.
- C. His pain is transmitted by the pelvic nerves.
- D. His pain is transmitted by right somatic nerve fibers. (Correct Answer)
- E. His pain is mainly transmitted by the right splanchnic nerve.
Lower abdominal cross-sections Explanation: ***His pain is transmitted by right somatic nerve fibers.***
- The **migration of pain from the periumbilical region to the right lower quadrant** and becoming **severe and constant** indicates parietal peritoneal irritation.
- **Somatic nerve fibers** innervate the parietal peritoneum and are responsible for transmitting **sharp, localized pain** typically associated with appendicitis in the right lower quadrant.
*His pain is transmitted bilaterally by somatic afferent nerve fibers of the abdomen.*
- While **visceral pain** from the initial appendiceal inflammation can be perceived bilaterally in the periumbilical region due to **bilateral innervation of visceral organs**, the **localized right lower quadrant pain** signifies involvement of **unilaterally innervated parietal peritoneum**.
- The physical exam findings of **rebound tenderness** strongly suggest **localized peritoneal inflammation**, which is transmitted by **unilateral somatic nerves** at the site of inflammation, not bilaterally across the abdomen.
*His pain is transmitted by somatic afferent nerve fibers located in the right flank.*
- The **right flank** refers to the lateral aspect of the abdomen, while the pain is specifically localized to the **right lower quadrant**.
- Although somatic nerves are involved, stating "right flank" is **too broad and imprecise** given the very specific localization of the pain to the right lower quadrant where the inflamed appendix is typically situated.
*His pain is transmitted by the pelvic nerves.*
- **Pelvic nerves** primarily carry parasympathetic fibers and visceral afferent fibers from pelvic organs, not the somatic pain from the parietal peritoneum in the right lower quadrant.
- Pain from **pelvic organs** or **pelvic peritoneum** would be transmitted via these nerves, but the localized pain here is distinctly higher than typical pelvic organ pain.
*His pain is mainly transmitted by the right splanchnic nerve.*
- **Splanchnic nerves** primarily carry **visceral afferent fibers** responsible for the dull, poorly localized, initial periumbilical pain of appendicitis.
- They do not transmit the **sharp, well-localized somatic pain** associated with parietal peritoneal irritation, which is characteristic of the pain migrating to the right lower quadrant.
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