Abdominal and Pelvic Radiology — MCQs

Abdominal and Pelvic Radiology Indian Medical PG Practice Questions and MCQs

Question 271: What type of CT scan is used to characterize the chemical composition of kidney stones?

A. Spiral CT
B. Multidetector CT
C. Dual-source CT (Correct Answer)
D. HRCT

Explanation: **Explanation:** **Dual-source CT (DSCT)**, a form of Dual-Energy CT (DECT), is the gold standard for the non-invasive characterization of kidney stone composition. It utilizes two X-ray sources operating at different energy levels (typically 80 kVp and 140 kVp) simultaneously. Because different chemical elements (e.g., Calcium vs. Uric Acid) attenuate X-rays differently at varying energy levels, the scanner can calculate the **effective atomic number (Z-eff)** of the stone. This allows clinicians to differentiate between uric acid stones and non-uric acid stones (calcium oxalate, cystine, or struvite), which is vital for management, as uric acid stones can often be dissolved medically (alkalinization) without surgery. **Analysis of Incorrect Options:** * **Spiral (Helical) CT:** This refers to the continuous rotation of the X-ray tube as the patient moves through the gantry. While it is the standard for detecting the *presence* and *location* of stones (NCCT KUB), it cannot determine chemical composition. * **Multidetector CT (MDCT):** This refers to a scanner with multiple rows of detectors. It provides high-speed, thin-slice imaging but, like Spiral CT, relies on a single energy source, making it unable to distinguish between stones of similar densities but different chemical makeups. * **HRCT (High-Resolution CT):** This technique uses very thin slices and specific reconstruction algorithms to visualize fine structural details, primarily used for **interstitial lung diseases**, not for abdominal stone analysis. **Clinical Pearls for NEET-PG:** * **Gold Standard for Stone Detection:** Non-Contrast CT (NCCT) is the most sensitive test for urolithiasis. * **Hounsfield Units (HU):** While HU can suggest stone hardness (e.g., >1000 HU suggests Calcium Oxalate Monohydrate), it often overlaps between stone types. DSCT is far more specific. * **Indinavir Stones:** These are the only kidney stones that are typically **radiolucent on CT scan**.

Question 272: What is the investigation of choice for retroperitoneal soft tissue sarcomas?

A. MRI
B. CT Scan (Correct Answer)
C. USG
D. PET scan

Explanation: **Explanation:** **1. Why CT Scan is the Correct Answer:** Contrast-Enhanced Computed Tomography (CECT) of the abdomen and pelvis is the **investigation of choice** and the gold standard for evaluating retroperitoneal soft tissue sarcomas (STS). Its superiority lies in its ability to provide high-resolution anatomical detail, determine the organ of origin, and assess the relationship of the tumor to major retroperitoneal vessels (like the aorta and IVC). It is also essential for staging, as it can simultaneously detect common sites of metastasis (e.g., lungs) and evaluate the contralateral kidney's function. **2. Why Other Options are Incorrect:** * **MRI (Option A):** While MRI offers superior soft-tissue contrast and is preferred for sarcomas of the **extremities** or pelvic floor, it is generally considered a second-line or adjunct modality in the retroperitoneum due to motion artifacts and longer acquisition times. * **USG (Option B):** Ultrasound is often the initial screening tool for an abdominal mass, but it lacks the depth of penetration and detail required to map the extent of a retroperitoneal tumor or plan surgical resection. * **PET Scan (Option D):** PET scans are not used for primary diagnosis. They are reserved for grading high-grade tumors, detecting distant recurrence, or monitoring response to chemotherapy. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common retroperitoneal sarcoma:** Liposarcoma (followed by Leiomyosarcoma). * **Biopsy Protocol:** If a biopsy is required, a **CT-guided core needle biopsy** is preferred. Fine Needle Aspiration (FNA) is generally avoided as it cannot provide the tissue architecture needed for grading. * **Surgical Goal:** The mainstay of treatment is "En-bloc" surgical resection with negative margins (R0 resection). * **Key Landmark:** The retroperitoneal space is located behind the posterior parietal peritoneum; displacement of the ureters or major vessels anteriorly is a classic radiological sign of a retroperitoneal mass.

Question 273: A previously healthy 61-year-old woman presents with a 3-week history of altered bowel habit and rectal bleeding. She refuses to undergo colonoscopy. Which of the following is the next best investigation?

A. CT colonography (Correct Answer)
B. CT abdomen and pelvis
C. Barium enema
D. Barium meal follow-through

Explanation: **Explanation:** The clinical presentation of altered bowel habits and rectal bleeding in a 61-year-old is highly suspicious for **Colorectal Carcinoma (CRC)**. While colonoscopy is the gold standard for diagnosis and biopsy, **CT Colonography (CTC)**, also known as "Virtual Colonoscopy," is the preferred alternative when a patient refuses or cannot tolerate conventional colonoscopy. **Why CT Colonography is the Correct Choice:** * **High Sensitivity:** CTC uses thin-slice CT data and 3D reconstruction to detect polyps and masses >10mm with sensitivity comparable to optical colonoscopy. * **Non-Invasive:** It does not require sedation and carries a much lower risk of perforation compared to traditional colonoscopy. * **Staging Capability:** Unlike barium studies, CTC can simultaneously evaluate the bowel wall, extraluminal extension, and distant metastases (TNM staging). **Analysis of Incorrect Options:** * **B. CT Abdomen and Pelvis:** A standard contrast-enhanced CT without specific colonic distension (air/CO2) has poor sensitivity for detecting small mucosal lesions or early-stage tumors. * **C. Barium Enema:** Historically used, but now largely replaced by CTC. It has lower sensitivity for small polyps and cannot provide information regarding extraluminal spread or lymphadenopathy. * **D. Barium Meal Follow-Through:** This is used to evaluate the **small intestine** (e.g., Crohn’s disease). It is not an appropriate investigation for suspected rectal or colonic pathology. **High-Yield Clinical Pearls for NEET-PG:** * **Apple Core Sign:** The classic radiological appearance of annular constricting colorectal carcinoma on barium studies. * **Screening:** In average-risk individuals, screening for CRC should begin at age 45. * **Contraindication:** CTC is contraindicated in patients with acute diverticulitis or recent bowel surgery due to the risk of perforation during insufflation.

Question 274: A 40-year-old male complains of recurrent urinary tract infections. An X-ray KUB shows a radio-opaque shadow. What is the most likely diagnosis?

A. Ureteric pathology (Correct Answer)
B. Prostate pathology
C. Testicular pathology
D. Stricture urethra

Explanation: ### Explanation **Correct Option: A. Ureteric pathology** The presence of a **radio-opaque shadow** on an X-ray KUB (Kidney, Ureter, Bladder) in a patient with recurrent urinary tract infections (UTIs) most commonly signifies a **urinary calculus**. Since the ureter lies within the anatomical field of a KUB film, a stone lodged in the ureter (ureterolithiasis) will appear as an opacity. Recurrent UTIs are a frequent complication of urolithiasis due to urinary stasis and nidus formation for bacteria. **Why other options are incorrect:** * **B. Prostate pathology:** While prostatic calculi exist, they are usually small, multiple, and located behind the symphysis pubis. Most common prostate pathologies (like BPH or Cancer) are soft-tissue changes not visible as distinct radio-opaque shadows on a standard X-ray. * **C. Testicular pathology:** The testes are located in the scrotum, which is generally outside the primary field of a standard KUB. Testicular pathologies (like tumors or torsion) are evaluated via Ultrasound/Doppler, not X-ray. * **D. Stricture urethra:** A stricture is a narrowing of the urethral lumen. It is a soft-tissue abnormality and is **radiolucent**. It requires a Retrograde Urethrogram (RGU) for visualization, not a plain X-ray. **High-Yield Clinical Pearls for NEET-PG:** * **90% of urinary stones** are radio-opaque (Calcium oxalate > Calcium phosphate > Magnesium ammonium phosphate/Struvite). * **Pure Uric Acid, Xanthine, and Indinavir stones** are radiolucent (not seen on X-ray). * **Phleboliths** (calcified pelvic veins) are the most common mimics of ureteric stones; they often have a "lucent center." * **Investigation of Choice:** Non-contrast CT (NCCT) KUB is the gold standard for detecting all types of urinary stones.

Question 275: What is true regarding the barium study of ileocecal tuberculosis?

A. String sign (Correct Answer)
B. Goose neck sign
C. Right-sided obstruction
D. Pulled up cecum

Explanation: **Explanation:** Ileocecal tuberculosis (TB) is the most common form of intestinal TB, primarily affecting the ileocecal junction due to the abundance of lymphoid tissue (Peyer's patches) and physiological stasis. **1. Why "String Sign" is correct:** The **String Sign of Kantor** refers to a persistent, narrow, thread-like appearance of the terminal ileum on a barium study. This occurs due to intense irritability and spasm of the inflamed segment, which prevents the lumen from filling completely. While also seen in Crohn’s disease, it is a classic radiological feature of ileocecal TB. **2. Analysis of Incorrect Options:** * **Goose neck sign:** This is incorrect because the characteristic finding in TB is the **Goose-head appearance** (or inverted umbrella sign), where the terminal ileum enters a contracted, shrunken cecum at a right angle. "Goose neck" is not a standard term for this pathology. * **Right-sided obstruction:** While TB can cause strictures, the barium study typically shows rapid emptying of the irritable segment (Stierlin’s sign) rather than a simple right-sided obstruction pattern. * **Pulled up cecum:** While the cecum does become contracted and fibrosed (conical cecum), the term "pulled up" is less specific than the physiological spasm represented by the String Sign in the context of this question's focus on barium dynamics. **High-Yield Clinical Pearls for NEET-PG:** * **Stierlin’s Sign:** Rapid emptying of the inflamed terminal ileum into the cecum due to irritability (the segment appears empty or poorly filled). * **Fleischner Sign:** An inverted umbrella appearance caused by a thickened ileocecal valve protruding into a narrowed cecum. * **Conical Cecum:** A shrunken, fibrosed cecum that has lost its normal pouch-like contour. * **Differential Diagnosis:** Always differentiate from **Crohn’s Disease**. TB typically involves the ileocecal valve (making it incompetent), whereas Crohn’s often spares the valve.

Question 276: Bilateral spider leg appearance of the kidney in IVP is characteristic of which condition?

A. Hydronephrosis
B. Polycystic kidney disease (Correct Answer)
C. Medullary sponge kidney
D. Renal cell carcinoma

Explanation: **Explanation:** The **"Spider Leg Appearance"** on Intravenous Pyelogram (IVP) is a classic radiological sign of **Autosomal Dominant Polycystic Kidney Disease (ADPKD)**. This appearance occurs because multiple large, fluid-filled cysts within the renal parenchyma exert pressure on the collecting system. This causes the renal pelvis and calyces to become elongated, stretched, narrowed, and attenuated, mimicking the thin, spindly legs of a spider. **Analysis of Options:** * **Polycystic Kidney Disease (Correct):** As explained, the bilateral enlargement of the kidney by numerous cysts distorts the calyces into elongated, thin structures. * **Hydronephrosis:** This condition presents with **dilatation** of the renal pelvis and calyces (clubbing of calyces), rather than the stretching/thinning seen in ADPKD. * **Medullary Sponge Kidney:** Characterized by the **"Paintbrush appearance"** or "Bouquet of flowers" due to ectasia (dilatation) of the collecting ducts in the renal pyramids. * **Renal Cell Carcinoma:** While it can cause stretching of calyces, it is typically **unilateral** and presents as a localized mass effect rather than the diffuse, bilateral "spider leg" deformity. **High-Yield Clinical Pearls for NEET-PG:** * **ADPKD:** Associated with Berry aneurysms (Circle of Willis), hepatic cysts, and mitral valve prolapse. * **Swiss Cheese Appearance:** The characteristic appearance of ADPKD on a Nephrogram. * **Pancake Kidney:** A fusion anomaly where both kidneys are fused into a single mass in the pelvis. * **Rim Sign:** Seen in severe hydronephrosis on IVP.

Question 277: A middle-aged male, a diagnosed case of chronic ulcerative colitis, presents to the emergency department with fever and diarrhea for one week, and acute onset abdominal pain for six hours. An erect abdominal X-ray was taken as shown. What is the likely diagnosis?

A. Pseudomembranous colitis
B. Adenocarcinoma of the colon
C. Pneumatosis intestinalis
D. Toxic megacolon (Correct Answer)

Explanation: ***Toxic megacolon*** - A patient with **chronic ulcerative colitis** presenting with fever, diarrhea, and acute abdominal pain strongly suggests **toxic megacolon**, a life-threatening complication. - The erect abdominal X-ray would show **colonic dilatation >6 cm** with **loss of haustral markings**, pathognomonic features of this condition. *Pseudomembranous colitis* - Typically caused by **Clostridioides difficile** infection, often following antibiotic therapy, which is not mentioned in this case. - While it can cause fever and diarrhea, it rarely presents with the **severe colonic dilatation** seen on imaging in toxic megacolon. *Adenocarcinoma of the colon* - Usually presents with **gradual onset** symptoms like weight loss, changes in bowel habits, and occult bleeding over months. - Would not cause the **acute severe dilatation** and systemic toxicity seen in this emergency presentation. *Pneumatosis intestinalis* - Characterized by **gas within the bowel wall** creating a linear lucency pattern on X-ray, not colonic dilatation. - Typically associated with **ischemic bowel disease** or severe inflammation, but doesn't match the clinical presentation of toxic megacolon.

Question 278: All are true about the radiological features of intestinal obstruction except?

A. The small intestines are said to be dilated if the loops of bowel have a diameter of > 3 cm.
B. The large bowel is said to be dilated if it is > 5 cm for distal bowel and > 9 cm for proximal bowel.
C. Volvulus and mesenteric ischemia have characteristic signs on abdominal films. (Correct Answer)
D. The absence of air-fluid levels on plain supine radiographs does not rule out the presence of an obstruction.

Explanation: **Explanation:** The diagnosis of intestinal obstruction relies heavily on the **"3-6-9 Rule"** and specific radiographic patterns. **Why Option C is the correct answer (The False Statement):** While certain conditions like sigmoid volvulus show a classic "coffee bean sign," **mesenteric ischemia** is notoriously difficult to diagnose on plain abdominal films. In its early, critical stages, the X-ray is often normal or shows non-specific gas patterns. Characteristic signs like *pneumatosis intestinalis* (air in the bowel wall) or portal venous gas are late, pre-terminal findings. Therefore, plain films lack the sensitivity and specificity required to diagnose mesenteric ischemia reliably; CT angiography is the gold standard. **Analysis of Incorrect Options (True Statements):** * **Option A & B:** These follow the **3-6-9 Rule** for bowel dilatation: Small bowel >3 cm, Large bowel >6 cm (distal/colon), and Cecum >9 cm (proximal). These are standard diagnostic thresholds on imaging. * **Option D:** Air-fluid levels are best seen on **erect** films. A **supine** radiograph may only show dilated, gas-filled loops without clear fluid levels. Furthermore, in "closed-loop" or "fluid-filled" obstructions, there may be very little intraluminal gas, making air-fluid levels absent despite a high-grade obstruction. **NEET-PG High-Yield Pearls:** * **Step-ladder pattern:** Classic sign of small bowel obstruction on erect films (multiple air-fluid levels). * **Valvulae Conniventes:** Thin mucosal folds crossing the full width of the small bowel (distinguishes it from haustra). * **String of Beads sign:** Small bubbles of gas trapped between valvulae conniventes in a fluid-filled small bowel; highly specific for obstruction. * **Coffee Bean Sign:** Pathognomonic for Sigmoid Volvulus. * **Bird’s Beak Sign:** Seen on contrast enema in Volvulus.

Question 279: The "string sign" on imaging is suggestive of which of the following conditions?

A. Toxic Megacolon
B. Hypertrophic Pyloric Stenosis (HPS) (Correct Answer)
C. Ulcerative Colitis
D. Irritable Bowel Syndrome (IBS)

Explanation: ### Explanation **Correct Answer: B. Hypertrophic Pyloric Stenosis (HPS)** The **"String Sign"** is a classic radiological finding in Hypertrophic Pyloric Stenosis (HPS). It is seen on a Barium swallow study when the contrast passes through a severely narrowed and elongated pyloric canal. The hypertrophy of the circular muscle of the pylorus causes luminal constriction, leaving only a thin "string" of contrast visible. **Analysis of Incorrect Options:** * **A. Toxic Megacolon:** Characterized by massive colonic dilation (usually >6 cm) and loss of haustral markings. The classic sign is a "distended, air-filled colon" on a plain X-ray, not a string sign. * **C. Ulcerative Colitis:** Chronic inflammation leads to the loss of haustral folds and shortening of the colon, resulting in the **"Lead Pipe"** appearance. (Note: A "String Sign" can be seen in **Crohn’s Disease** due to terminal ileum narrowing, but it is not a feature of Ulcerative Colitis). * **D. Irritable Bowel Syndrome (IBS):** This is a functional disorder; imaging is typically normal and does not show structural narrowing or the string sign. **High-Yield Clinical Pearls for NEET-PG:** * **HPS Presentation:** Typically occurs in first-born males (3–6 weeks old) with **non-bilious, projectile vomiting**. * **Physical Exam:** A palpable, firm, mobile mass in the epigastrium known as the **"Olive sign."** * **Metabolic Profile:** Hypochloremic, hypokalemic metabolic alkalosis (due to loss of HCl from vomiting). * **Other HPS Signs:** * **Beak Sign:** Contrast entering the proximal end of the narrowed canal. * **Shoulder Sign:** Bulging of the pyloric muscle into the antrum. * **Double Track Sign:** Two thin streaks of barium separated by a radiolucent mucosal fold. * **Investigation of Choice:** Ultrasound (Criteria: Pyloric muscle thickness >3-4 mm or length >14-16 mm).

Question 280: A middle-aged patient presents with a complaint of right hypochondrial pain. An X-ray shows an elevated right hemidiaphragm. Which of the following is NOT a possible diagnosis?

A. Subphrenic abscess
B. Acute cholecystitis (Correct Answer)
C. Pyogenic liver abscess
D. Amoebic liver abscess in the right lobe

Explanation: **Explanation:** The elevation of a hemidiaphragm on a chest or abdominal X-ray is typically caused by either **phrenic nerve palsy**, **intrathoracic volume loss** (e.g., collapse), or **intra-abdominal pathology** that exerts upward pressure or causes reactive irritation of the diaphragmatic muscle. **Why Acute Cholecystitis is the Correct Answer:** In **Acute Cholecystitis**, the inflammation is localized to the gallbladder, which is situated on the inferior surface of the liver, well away from the diaphragmatic pleura. While it causes significant right hypochondrial pain and tenderness (Murphy’s sign), it typically does not involve the superior surface of the liver or the subphrenic space. Therefore, it does not cause the mass effect or diaphragmatic irritation required to elevate the hemidiaphragm. **Analysis of Incorrect Options:** * **Subphrenic Abscess (Option A):** An accumulation of infected fluid between the liver and the diaphragm directly pushes the diaphragm upward and causes reactive paralysis/splinting. * **Pyogenic & Amoebic Liver Abscesses (Options C & D):** Large abscesses, especially those located in the superior segments of the right lobe of the liver, cause hepatomegaly and localized inflammatory changes that frequently result in an elevated right hemidiaphragm and occasionally a reactive pleural effusion. **NEET-PG High-Yield Pearls:** * **Eventration of Diaphragm:** A congenital condition where the diaphragm is thin/weak (muscular aplasia), leading to permanent elevation. * **Phrenic Nerve Palsy:** Most common cause of a newly elevated hemidiaphragm; confirmed by the **Sniff Test** (paradoxical upward movement of the paralyzed side during inspiration under fluoroscopy). * **Amoebic Liver Abscess:** Classically presents with "anchovy sauce" pus; elevation of the right hemidiaphragm is a classic radiological sign.

Practice by Chapter

Imaging of Liver

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Gastrointestinal Tract Imaging

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Renal and Urinary Tract Imaging

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Adrenal Imaging

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Male Pelvic Imaging

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Abdominal Trauma Imaging

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Acute Abdomen Imaging

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Imaging of Peritoneal Cavity and Retroperitoneum

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