Abdomen: MRCEM Primary questions with answers

The Abdomen topic starts with the abdominal wall muscles and the regions used to describe where pain sits. It then moves through the lumbar spine and plexus, gastrointestinal tract, accessory organs, reproductive system, pelvic diaphragm and urinary tract, with trunk dermatomes. Anatomy carries 60 of the 180 questions in MRCEM Primary. Emergency physicians rely on these relations when assessing abdominal pain, trauma and referred pain.

5 free questions below, each with the answer and the full explanation · 292 in the full bank · Last updated after the 27 October 2026 MRCEM Primary sitting.

1. Question 1 · Abdominal Wall Muscles

   A man aged 50 complains of intermittent abdominal pain on lifting and coughing. You suspect a Spigelian hernia. Weakness of which structure is most likely to be responsible?

   1. AFemoral sheath
   2. BTransversus abdominus aponeurosis
   3. CIliopsoas fascia
   4. DInternal inguinal ring
   5. ETransversalis fascia
   Show answer and explanation

   Answer: B. Spigelian hernia is a defect in the transversus abdominis aponeurosis at the linea semilunaris.

   • A: The femoral sheath is involved in femoral hernia.
   • C: Iliopsoas fascia is not involved in Spigelian hernia.
   • D: The internal inguinal ring is the site of indirect inguinal hernia.
   • E: Transversalis fascia weakness gives direct inguinal hernia.

   Full explanation: Abdominal Wall Muscles

   Layers of the Abdominal Wall (external to internal) 

   • Skin 
   • Superficial fascia (Camper’s fascia: Superficial fatty layer Scarpa’s fascia: deep fibrous layer )
   • Muscles 
   • Transversalis fascia 
   • Parietal peritoneum 

   Anterior abdominal wall muscles 

   • The muscles of the anterolateral abdominal wall can be divided into two main groups that lie deep in the superficial fascia. 
   • Three flat muscles: (External oblique, internal oblique and transversus abdominus), located laterally, each flat muscle forms an aponeurosis (a broad, flat tendon) in the anteromedial aspect of the abdominal wall which covers the vertical rectus abdominis muscle. The aponeuroses of all the flat muscles become entwined in the midline, forming the Linea alba.
   • Two vertical muscles: Rectus abdominus and pyramidalis situated near midline of body 
   • Innervation: The anterior abdominal wall muscles are innervated by the anterior rami of T7-T12 and L1.

   External oblique	Largest and most superficial of all Together with the aponeuroses from the internal oblique and the transversus abdominis, the external oblique covers the anterior part of the abdominal wall and forms the linea alba at the midline, The Linea alba extends from the xiphoid process to the pubic symphysis. The lower free border of the external oblique aponeurosis forms the inguinal ligament on each side A part that continues posterior (toward the superior pubic ramus) is termed as the lacunar ligament
   Internal oblique	Lie deep to the external oblique. The aponeurosis of the internal oblique muscle divides into anterior and posterior layers, which pass, respectively, in front of and behind the rectus muscle to reach the Linea alba Note: Inferiorly internal oblique division into anterior and posterior layers is absent, where the aponeuroses of all three muscles pass anterior to the rectus muscles to reach the Linea Alba. Inferiorly, the medial portion of the fused internal oblique and transversus aponeuroses is termed the conjoined tendon.
   Transversus abdominus	Innermost of flat anterior abdominal wall muscles Like the other flat muscles, it contributes aponeurotic fibres to the Linea Alba. Deep to this muscle is a well-formed layer of fascia, called the transversalis fascia.
   Rectus abdominus	The rectus abdominis is long, paired muscle, found either side of the midline in the abdominal wall. It is split into two by the Linea alba. The lateral borders of the muscles create a surface marking known as the Linea semilunaris. At several places, the muscle is intersected by fibrous strips, known as tendinous intersections.
   Pyramidalis	Small triangle shaped muscle, found superficially to the rectus Abdominus, located inferiorly, with its base on the pubis bone, and the apex of the triangle attached to the Linea alba. It acts to tense the Linea alba.

   Other contents

   • Rectus sheath: The rectus sheath is formed by the aponeuroses of the three flat muscles and encloses the rectus abdominis and pyramidalis muscles. It has an anterior and posterior wall for most of its length. 
   • Anterior wall: Formed by the aponeuroses of the external oblique, and of half of the internal oblique. 
   • Posterior wall:  Half of the aponeuroses of the internal oblique and of the transversus abdominis. 
   • Approximately midway between the umbilicus and the pubic symphysis, all the aponeuroses move to the anterior wall of the rectus sheath. At this point, there is no posterior wall to the sheath; the rectus abdominis is in direct contact with the transversalis fascia. Point, where the posterior layer of the rectus sheath ends, is the arcuate line. 

   • Contents of the rectus sheath
   • Rectus abdominus and the pyramidalis muscle 
   • The superior and inferior epigastric vessels 
   • The termination of intercostal nerves T7-T11 
   • The 12th thoracic nerve and the accompanying vessels 

    

   Posterior abdominal wall muscle

   • Important posterior abdominal wall muscles are the psoas major, minor, the iliacus and the quadratus lumborum which each possess a strong fascial covering.  

   Muscle	Function	Innervation
   Psoas major	Flexes thigh at hip joint when trunk is stabilized, flexes trunk against gravity when body is supine	Anterior rami L1 – L3
   Psoas minor	Flexion of the vertebral column	Anterior rami of L1 spinal nerve
   Quadratus lumborum	Depresses and stabilizes twelfth rib, contributes to extension and lateral flexion of vertebral column	Anterior rami of T12 and L1-L4
   Iliacus	Flexes thigh at hip joint when trunk is stabilized, flexes trunk against gravity when body is supine	Femoral nerve L2-L4

    

   Iliacus and Psoas major origin and insertion

   • Iliacus: Originates from surface of the iliac fossa and anterior inferior iliac spine. Its fibres combine with the tendon of the psoas major, inserting into the lesser trochanter of the femur. 
   • Psoas major: Originates from the transverse processes and vertebral bodies of T12 – L5. It then moves inferiorly and laterally, running deep to the inguinal ligament, and inserting to the lesser trochanter of the femur. 

   Clinical pearls

   • Psoas sign: Irritation of iliopsoas muscle, psoas sign positive when thigh is flexed pain is felt in lower abdominal wall, indication of appendicitis. 

    

    

    

2. Question 2 · Male and Female Reproductive System

   A man aged 60 presents to ED complaining of difficulty passing urine and nocturia. On examination, you note the prostate is enlarged and you suspect BPH. Which of the following lobes of the prostate are most likely hypertrophied:

   1. ALateral lobe
   2. BPosterior lobe
   3. CMedian lobe
   4. DAnterior lobe
   5. EPeripheral zone
   Show answer and explanation

   Answer: C. BPH arises from the periurethral glands, classically the median lobe, enlarging and obstructing the urethra.

   • A: Lateral lobes can enlarge, but the median lobe is the classic site.
   • B: The posterior lobe is the area most prone to carcinoma.
   • D: The anterior lobe is fibromuscular with little glandular tissue.
   • E: The peripheral zone is the usual site of carcinoma, not BPH.

   Full explanation: Male and Female Reproductive System

   Male Genital organs:

   Testis and Epididymis:

   Paired structure located within the scrotum 

   • Testis and Epididymis are Suspended in the scrotum by the spermatic cord. 
   • Testes are site of sperm production 
   • Epididymis stores the sperm 

   Anatomic structure:

   • Testis is covered by tunica albuginea which lies beneath the visceral layer of the tunica veginalis 
   • Each testis is composed of seminiferous tubules which produce spermatozoa and interstitial cells (of Leydig) secrete testosterone

   Innervation of testis and epididymis: testicular plexus – a network of nerves derived from the renal and aortic plexus

   Lymphatic drainage:(Important to remember) 

   • Testes lumbar (para-aortic) nodes in the abdomen 
   • scrotum drains to the superficial inguinal nodes. 

   Blood supply: Paired testicular arteries arise from abdominal aorta 

   Clinical pearls:

   Testicular torsion is the twisting of a testis and the spermatic cord, obstructing blood vessels to the testis and causing sudden urgent pain and swelling of the scrotum. 

   • Caused by trauma or spasm of cremasteric muscle. 

   Ductus deferens:

   • Is continuous with the tail of the epididymis and serves to transport sperm to the ejaculatory ducts prior to ejaculation. 
   • Is a thick-walled tube that ascends within the spermatic cord to enter the pelvis at the deep inguinal ring lateral to the inferior epigastric artery. 

     

   Clinical pearls: Vasectomy is the surgical excision of a portion of the vas deferens (ductus deferens) through the scrotum. It stops the passage of spermatozoa. 

   Spermatic cord and contents: 

   • Must remember important spermatic cord covering and contents with rule of “3” 
   • Three arteries, three nerves and three other structures 

   High yield: 

   3 Layered Covering: External Spermatic Fascia (Fascia of External Oblique) Cremaster Muscle (Internal Oblique) Internal Spermatic Fascia (Fascia Transversalis)	3 Arteries: Artery to Ductus Deference Cremasteric Artery Testicular Artery
   3 Nerves: Genitofemoral nerve – Genital Branch Sympathetic Nerve Ilio-Inguinal Nerve (outside the cord)	3 Other Structures: Pampniform Plexus Testicular Veins Testicular Lymphatic

    

   Penis:

   The penis consists of a root (two crura and the bulb of the penis) and the body, which is formed by the single corpus spongiosum which contains the spongy urethra and paired corpora cavernosa.  Its head is called the glans penis which is the terminal part of the corpus spongiosum. 

   Innervation: The penis is supplied by S2-S4 spinal cord segments and spinal ganglia. 

   • Sensory and sympathetic innervation to the skin and glans penis is supplied by the dorsal nerve of the penis, a branch of the pudendal nerve. 
   • Parasympathetic innervation is carried by cavernous nerves from the peri-prostatic nerve plexus and is responsible for the vascular changes which cause erection. 

   Blood supply: Dorsal arteries of the penis, Deep arteries of the penis and Bulbourethral artery branches of the internal pudendal artery. 

   Lymphatic drainage: (Important to remember) 

   • Penile Skin and prepuce: Drain into Superficial inguinal nodes. 
   • Glans penis and penile urethra drain into deep inguinal nodes. 

   Prostate gland:

   largest accessory structure of male reproductive system lies  

   • immediately inferior to the bladder and the internal urethral sphincter 
   • Anterior to the rectum 
   • superior to the external urethral sphincter 

   Functional anatomy: Secretes a fluid that produces the characteristic odor of semen. This fluid, the secretion from the seminal vesicles and the bulbourethral glands, and the spermatozoa constitute the semen or seminal fluid. 

   Prostate has four zones:  

   • Anterior zone: which lies in front of the urethra. 
   • Transitional zone: encompasses the urethra proximal to the ejaculatory ducts and is prone to benign hypertrophy obstructing the internal urethral orifice  
   • Central zone: encompasses the ejaculatory ducts up to the urethra. 
   • Peripheral zone: situated posteroinferior and lateral to the transitional and central zones, forming the main mass of the gland and is thus the most prone to carcinomatous transformation.

      

   Clinical pearls: Hypertrophy of the prostate is a benign enlargement of the prostate that affects older men and occurs most often in the transitional zone, obstructing the internal urethral orifice and thus leading to nocturia (excessive urination at night), dysuria (difficulty or pain in urination), and urgency (sudden desire to urinate). 

   Prostate cancer is a slow-growing cancer that occurs particularly in the peripheral zone. 

   Blood supply: Prostatic arteries derived from internal iliac arteries. 

   Innervation : The prostate receives sympathetic, parasympathetic and sensory innervation from the inferior hypogastric plexus 

   Female genital organs: 

   Ovary:

   Female gonads: Sites of egg production 

   Ovaries Lie on the posterior aspect of the broad ligament on the side wall of the pelvis minor and are bounded by the external and internal iliac vessels.  

   • Not covered by the peritoneum, and thus, the ovum or oocyte is expelled into the peritoneal cavity and then into the uterine tube.  
   • Are not enclosed in the broad ligament, but their anterior surface is attached to the posterior layer of the broad ligament by the mesovarium

   Ligaments of the ovary: 

   Ovarian ligament (Round ligament of ovary) Attaches the ovaries to the lateral wall of uterus 

   Suspensory ligament of ovary: fold of peritoneum extending from the mesovarium to the pelvic wall. Contains neurovascular structures 

   Blood supply: Are supplied primarily by the ovarian arteries, which are contained in the suspensory ligament and anastomose with branches of the uterine artery.  

   Venous drainage: 

   Are drained by the ovarian veins; the right ovarian vein joins the inferior vena cava, and the left ovarian vein joins the left renal vein   

   Innervation: Autonomic: via the ovarian plexus 

   Visceral afferents: accompany the sympathetic fibers to T10 – T12 level of the spinal cord sensory ganglia 

   • Pain is thus referred to the periumbilical region, suprapubic region and groin. 

   Uterine tube:

   The uterine tube extends from the uterus to the ovary and consists of the isthmus, ampulla, and infundibulum. The fimbriated distal end creates currents, drawing an ovulated oocyte into the uterine tube. 

   Note: Ectopic pregnancy most commonly occurs in the ampulla (70% of cases).

    

   Uterus:

   Contains a fundus, body, isthmus and cervix and is supported by ligaments. 

   Relations:

   • Anteriorly: vesicouterine pouch and the urinary bladder 
   • Posteriorly: the rectouterine pouch and the anterior surface of rectum 
   • Laterally: the broad ligament 

   Suspensory ligaments:

   • The uterosacral ligament 
   • The round ligaments 
   • The cardinal ligaments 

   Arterial supply:

   • Uterine arteries: branch of internal iliac artery 
   • Ovarian arteries: branch of the abdominal aorta at the level of L1. 

   Venous drainage:

   Uterine veins: they are formed from the plexus and drain into internal iliac veins 

   Innervation: Autonomic 

   • Hypogastric plexus (sympathetic) 
   • S3-S4 (parasympathetic) 

   Visceral afferents: T11-T12 

   Vagina:

   Relations:

   • Anteriorly: urethral orifice 
   • Posteriorly: The rectum 

   Arterial supply: Uterine arteries supply the superior portion: branch of the internal iliac artery 

   Vaginal artery and internal pudendal arteries supply the middle and inferior parts: branches of the internal iliac artery. 

   Venous drainage: Uterovaginal plexus: drains into internal iliac veins 

   Innervation 

   • Autonomic: inferior hypogastric plexus, pelvic splanchnic, pudendal nerve (all provide parasympathetic Innervation from S2-S4) 
   • Visceral afferents: accompany parasympathetic fibers of inferior hypogastric and pelvic splanchnic nerves to S2-S4. 
   • Somatic afferents: accompany pudendal nerve to S2-S4. 

   Clinical pearls: 

   Digital vaginal examination: 

   Digital vaginal examination allows palpation of the: 

   • urethra and bladder through the anterior fornix of the vagina 
   • the perineal body, rectum, coccyx and sacrum through the posterior fornix 
   • ovaries, uterine tubes, ureters and ischial spines through the lateral fornices

    

3. Question 3 · Gastrointestinal Tract

   A mother brought her five-year-old son into the ED with hematemesis after he swallowed a button battery. CT scan shows it is stuck at T10. Which vessel has been damaged and is bleeding?

   1. AGastroduodenal artery
   2. BRight gastric artery
   3. CInferior mesenteric artery
   4. DSplenic artery
   5. ELeft gastric artery
   Show answer and explanation

   Answer: E. A battery lodged at the left gastro-oesophageal junction erodes the left gastric artery, causing haematemesis.

   • A: The gastroduodenal artery is related to the first part of the duodenum.
   • B: The right gastric artery supplies the lesser curve of the stomach, away from the junction.
   • C: The inferior mesenteric artery supplies the hindgut.
   • D: The splenic artery lies behind the stomach, not at the junction.

   Full explanation: Gastrointestinal Tract

   Stomach:

   • Intraperitoneal organ located between oesophagus and duodenum, lie in epigastrium, umblical and left hypochondrium. 
   • Stomach is divided into four regions 
   • The cardia which surrounds opening of the oesophagus into stomach 
   • The fundus 
   • The body 
   • The Pylorus: Connects the stomach to the duodenum. It is divided into the pyloric antrum, pyloric canal and pyloric sphincter 
   • The pyloric sphincter lies between the pylorus and the first part of the duodenum. It controls of the exit of chyme. 

   Anatomical relation of stomach

   The stomach lies anterior to the stomach bed 

   stomach bed formed by: 

   • Useful mnemonic “Dr. S3 kills patients mercilessly.” 
   • Diaphragm 
   • Splenic flexure 
   • Suprarenal gland (Left) 
   • Splenic artery 
   • Kidney (Left) 
   • Pancreas 
   • Mesocolon (Transverse) 

   Blood supply: 

   The arterial supply to the stomach is derived from all three branches (left gastric, splenic, and common hepatic branches) of the coeliac trunk. 

   Innervation: 

   Parasympathetic from anterior and posterior vagal trunk derived from vagus nerve 

   Sympathetic nerve supply: From the T6 through T9 segments of the spinal cord passes to celiac plexus through the Greater splanchnic nerve mediates epigastric and visceral referred pain from gastric ulcer. 

   Small intestine:

   longest part of the gastrointestinal tract and extends from the pyloric orifice of the stomach to the ileocaecal fold, comprising the duodenum, jejunum and ileum.  

    Duodenum:

   • C shaped structure lying Infront of, and to the right of inferior vena cava and aorta 
   • Duodenum is retroperitoneal organ except for its proximal part 

   Parts of duodenum: 

   First part: The superior (first) part extends from the pyloric orifice of the stomach to the neck of the gallbladder, lies just to the right of the body of vertebra L1, and passes anterior to the inferior vena cava and superior to the head of the pancreas 

   Second part: The Descending (2nd) Part of the duodenum 

   • It lies to the right of the bodies of L1 to L3 vertebrae. Runs inferiorly, curving around the head of the pancreas. It extends from the superior duodenal flexure to the inferior duodenal flexure. 
   • During its descent, it passes right of and parallel with the inferior vena cava. 
   • The common bile duct and main pancreatic duct (these ducts usually unite to form the hepatopancreatic ampulla of Vater) enter the posteromedial wall of this part of the duodenum, about 2/3 of the way along its length. 
   • The lesser duodenal papilla lies about 6-8 cm distal to the pylorus and has at its summit the opening of the accessory pancreatic duct. 

   Third part: The inferior or horizontal part of the duodenum Runs transversely to the left, passing over the IVC, aorta, and L3 vertebra. 

   • It is crossed by the superior mesenteric artery and vein and the root of the mesentery. 
   • Superior to it is the head of the pancreas and its uncinate process. 

   Fourth part: The Ascending (4th) Part of the Duodenum 

   • This ascends on the left side of the aorta anterior to the left renal vessels to the level of L2 vertebra. 
   • Here it meets the jejunum at the duodenojejunal flexure. The duodenojejunal flexure is supported by a fibromuscular band called the suspensory muscle (ligament) of the duodenum (ligament of Treitz). 

   Blood supply: Branches of coeliac trunk and superior mesenteric artery 

   • Proximal to the major duodenal papilla: supplied by the gastroduodenal artery (branch of the common hepatic artery from the coeliac trunk). 
   • Distal to the major duodenal papilla: supplied by the inferior pancreaticoduodenal artery (branch of superior mesenteric artery). 

   Clinical pearls:  

   • Duodenal ulcer: erosion of the mucosa in the duodenum 
   • most likely to occur in the superior portion of the duodenum. 
   • The most common causes of duodenal ulcers are Helicobacter pylori infection and chronic NSAID therapy. 
   • Duodenal ulcer most likely erosion of the gastroduodenal artery 

   Small intestine jejunum and ileum: 

   Jejunum	Ileum
   Begins at the duodenojejunal flexure. Constituting approximately 2/5th of small intestine Lies in the left upper quadrant. Thick intestinal wall	The ileum invaginates into the large intestine at the ileocaecal junction forming the ileocaecal valve, which prevents reflux from the caecum to the ileum Constituting approximately 3/5th of small intestine Lies in the lower right quadrant Thin intestinal wall

   Blood supply: Superior mesenteric artery 

   Clinical pearls:

   Meckel’s Diverticulum:

   • True diverticula of all 3 layers of the small intestines 
   • Caused by incomplete obliteration of the vitelline duct. 
   • Rule of 2s: 2 years old, 2 ft from ileocecal valve, 2 in long, 2% of population 
   • Usually, asymptomatic 
   • Painless bleeding due to an ulcer caused by heterotopic gastric tissue most common presentation in children
   • Obstruction is caused by intussusception, volvulus, and hernia most common presentation in adults.
   • Rich blood supply to Meckle’s diverticulum is from Superior mesenteric artery.
     • Proximal to the major duodenal papilla: supplied by the gastroduodenal artery (branch of the common hepatic artery from the coeliac trunk
     • Distal to the major duodenal papilla: supplied by the inferior pancreaticoduodenal artery (branch of a superior mesenteric artery)

   Large intestine

   • Extends from the ileocecal junction to the anus and is approximately 1.5 m (5 ft) long. Consists of the cecum, appendix, colon, rectum, and anal canal.  
   • Cecum: First part of the large intestine, blind end pouch of the large intestine 
   • It lies in the right iliac fossa. 
   • Surrounded by peritoneum.

   Colon 

   • Has ascending and descending colons that are retroperitoneal and transverse and sigmoid colons that are surrounded by peritoneum (intraperitoneal). 

    

   Ascending Colon:The colon begins as the ascending colon. 

   • Is a retroperitoneal structure which ascends superiorly from the cecum. 
   • When it meets the right lobe of the liver, it turns 90 degrees to move horizontally. This turn is known as the right colic flexure (or hepatic flexure) and marks the start of the transverse colon. 

   Transverse Colon

   • The transverse colon extends from the right colic flexure to the spleen, where it turns another 90 degrees to point inferiorly. This turn is known as the left colic flexure (or splenic flexure)

   Blood supply of colon:

   • Cecum, Appendix, the ascending colon, hepatic flexure and proximal 2/3 of the transverse colon are supplied by the superior mesenteric artery.  
   • Distal 1/3 of transverse colon, Splenic flexure and the descending and sigmoid colons are supplied by the inferior mesenteric artery.  

   Lymphatic nodes:

   • The ascending and transverse colons: superior mesenteric nodes 
   • The descending and sigmoid colons: Inferior mesenteric nodes 
   • Note: Most of the lymph from the superior and inferior mesenteric nodes passes into the intestinal lymph trunks, and on to the cisterna chyli, where it ultimately empties into the thoracic duct. 

   Innervation:

   • Ascending colon and proximal 2/3 of the transverse colon: receive their sympathetic, parasympathetic and sensory supply via nerves from the superior mesenteric plexus. 
   • Distal 1/3 of the transverse colon, descending colon and sigmoid colon: receive their sympathetic, parasympathetic and sensory supply via nerves from the inferior mesenteric plexus: 
   • Parasympathetic innervation via the pelvic splanchnic nerves 
   • Sympathetic innervation via the lumbar splanchnic nerves. 

   Large intestine-Appendix: Is a narrow, hollow, muscular tube with large aggregations of lymphoid tissue in its wall.  

   • suspended from the terminal ileum by a small mesentery, the mesoappendix, which contains the appendicular vessels.  
   • Causes spasm and distention when inflamed, resulting in pain that is referred to the periumbilical region and moves down and to the right.  
   • Has a base that lies deep to McBurney point, which occurs at the junction of the lateral one-third of an imaginary line between the right anterior superior iliac spine and the umbilicus. This is the site of maximum tenderness in acute appendicitis. 
   • Position of appendix: Most common appendix position is retrocaecal followed by pelvic. 
   • It may be: 
   • Posterior to the caecum (retrocaecal)  
   • suspended over the pelvic brim in a pelvic or descending position. 
   • Below the caecum in a subcaecal position 

   Blood supply: Branch of superior mesenteric artery 

   • Note: sympathetic afferent fibres of the appendix arise from T10 of the spinal cord, thus explaining why the visceral pain of early appendicitis is felt centrally within the abdomen in periumbilical region.

   Clinical pearls:

   • Rovsing’s sign: Pain in the right lower quadrant is complained of when palpation pressure is exerted in the left lower quadrant. It is also called referred rebound tenderness and when present is quite helpful in supporting the diagnosis.  
   • Psoas sign: This test is performed by having the patient lie on his left side. The examiner then slowly extends the patient’s right thigh, thus stretching the iliopsoas muscle. This will produce pain to make the sign positive. This indicates presence of irritative inflamed appendix in close proximity to the psoas muscle. This is possible in retrocaecal appendicitis. 
   • Obturator test: Passive internal rotation of flexed right thigh with the patient in supine position will elicit pain. This positive obturator sign is diagnostic of pelvic appendicitis. 

   Rectum and anal canal:

   • Rectum is a part of the large intestine that extends from the sigmoid colon to the anal canal and follows the curvature of sacrum and coccyx. 
   • Rectum is retroperitoneal structure. 
   • In men the rectum lies posterior to the bladder, prostate and seminal vesicle. 
   • In woman lies posterior to uterus, vagina and cervix. 

    

   • Peritoneal Coverings: In the superior third of the rectum, the anterior surface and lateral sides are covered by peritoneum.  
   • The middle third only has an anterior peritoneal covering  
   • Lower 1/3 has no peritoneum associated with it. 
   • In males, the reflection of peritoneum from the rectum to the posterior bladder wall forms the rectovesical pouch.  
   • In females, the peritoneum reflects to the posterior vagina and cervix, forming the rectouterine pouch (pouch of Douglas 

   Blood supply: 

   • Superior rectal artery: terminal continuation of the inferior mesenteric artery. 
   • Middle rectal artery: branch of the internal iliac artery. 
   • Inferior rectal artery: branch of the internal pudendal artery.

   Innervation of Rectum:

   • Sympathetic nervous supply to the rectum is from the lumbar splanchnic nerves and superior and inferior hypogastric plexuses.  
   • Parasympathetic supply is from S2-4 via the pelvic splanchnic nerves and inferior hypogastric plexuses.  

   Lymphatic drainage: Pararectal lymph nodes 

   Clinical pearls:

   Digital rectal examination: Performed by inserting a gloved lubricated finger into the rectum 

   • The anterior wall of the rectum has a number of close anatomical structures, and these structures can therefore be palpated digitally via the rectum.  
   • Most significant are the prostate and seminal vesicles in males, and cervix in females.  
   • Bony structures, such as the sacrum and coccyx, may also be palpated in both sexes. 

   Anal canal: 

   • Lies below the pelvic diaphragm and ends at the anus 
   • Anal sphincter:
   • Internal anal sphincter: Consists of involuntary smooth muscle that surrounds the upper 2/3 of the anal canal. 
   • External anal sphincter: voluntary muscle that surrounds the lower 2/3 of the anal canal (and so overlaps with the internal sphincter). It blends superiorly with the puborectalis muscle of the pelvic floor. 
   • Iin the anal canal, the mucosa is organized into longitudinal folds, known as anal columns. These are joined at their inferior ends by anal valves. The anal valves collectively form an irregular circle known as the pectinate line (or dentate line). This line divides the anal canal into upper and lower parts. 

    

   • Defecation: Is initiated by distention of the rectum, filled from the sigmoid colon, and afferent impulses are transmitted to the spinal cord by pelvic splanchnic nerves. The pelvic splanchnic nerves increase peristalsis (contracts smooth muscles in the rectum). In contrast, sympathetic nerves cause a decrease in peristalsis, maintain tone in the internal sphincter, and contain vasomotor and sensory (pain) fibers. Involves the following: 
   • The intra-abdominal pressure is increased by holding the breath and contracting the diaphragm, the abdominal muscles, and the levator ani, thus facilitating the expulsion of feces. 
   • The puborectalis relaxes, which decreases the angle between the ampulla of the rectum and the upper portion of the anal canal, thus facilitating defecation. 
   • The smooth muscle in the wall of the rectum contracts, the internal anal sphincter relaxes, and the external anal sphincter relaxes to pass the feces. 
   • After evacuation, the contraction of the puborectalis and the anal sphincters closes the anal canal. 

   Neurovascular supply and lymphatic drainage of anal canal:

   Supply	Above pectinate line	Below pectinate line
   Arterial Supply	Superior rectal artery (branch of inferior mesenteric artery	Inferior rectal artery (branch of the internal pudendal artery
   Nerve Supply	Visceral innervation via the inferior hypogastric plexus.	Somatic innervation via the inferior rectal nerves (branches of the pudendal nerve) Sensitive to pain, temperature, touch and pressure.
   Lymphatics	Internal iliac lymph nodes	Superficial inguinal lymph nodes

   Clinical pearls:

   • Hemorrhoids are dilated internal and external venous plexuses around the rectum and anal canal.  
   • Internal hemorrhoids occur above the pectinate line, are covered by a mucous membrane, and their pain fibers are carried by Visceral afferent fibers of the sympathetic nerves. 
   • External hemorrhoids are situated below the pectinate line, are covered by skin, and are more painful than internal hemorrhoids because their pain fibers are carried by Somatic fibers of the inferior rectal nerves. 

    

4. Question 4 · Abdomen

   A male aged 55 Years with a history of hypertension came into the ED with sudden severe abdominal pain. After initial assessment at triage, you suspect abdominal aortic aneurysm. Which one of the following is the most common site of abdominal aortic aneurysm?

   1. ABelow diaphragm
   2. BInfrarenal aorta
   3. CSuprarenal aorta
   4. DAt the level of umbilicus
   5. EEpigastrium
   Show answer and explanation

   Answer: B. The infrarenal aorta is the site of 90 to 99% of abdominal aortic aneurysms.

   • A: Too vague; the aneurysm typically begins below the renal arteries.
   • C: Suprarenal aneurysms are uncommon.
   • D: The umbilicus is a surface landmark, not the usual site.
   • E: Epigastric level corresponds to the suprarenal aorta, uncommon.

   Full explanation

   The most common location of arterial aneurysm formation is the abdominal aorta, while the most common site of abdominal aortic aneurysm is infrarenal aorta (90 to 99%)

5. Question 5 · Urinary Tract

   A man aged 37 presents with acute left flank pain. A plain abdominal X-ray (KUB) shows an opacity near the ureteropelvic junction. What is the most appropriate next investigation?

   1. AMRI abdomen
   2. BUltrasound (USG) abdomen and pelvis
   3. CIntravenous pyelogram (IVP)
   4. DCT abdomen without contrast
   5. EUrinalysis only
   Show answer and explanation

   Answer: B. Ultrasound is a non-invasive, radiation-free, widely available first-line test to confirm stones and assess hydronephrosis.

   • A: MRI is not a first-line test for suspected stones.
   • C: IVP is an older contrast technique, not first-line.
   • D: Non-contrast CT involves radiation; ultrasound is the preferred first-line follow-up here.
   • E: Urinalysis alone cannot show the stone or hydronephrosis.

   Full explanation

   The ureteropelvic junction (UPJ) is a common site for renal calculi (kidney stones). X-ray KUB can detect radiopaque stones, but further imaging is needed for confirmation and to assess complications like hydronephrosis. Ultrasound is a non-invasive, radiation-free, and widely available first-line investigation to evaluate the kidneys, ureters, and bladder. It can detect:

   • Hydronephrosis
   • Renal stones (especially in the renal pelvis)
   • Obstructive uropathy

   Although non-contrast CT (NCCT) is more sensitive and specific for detecting stones, USG is often the first recommended test, especially in initial or uncomplicated cases, and in young or pregnant patients.