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ABPS Diagnostic Radiology study materials
ABPS Diagnostic Radiology study resources

ABPS Diagnostic Radiology practice questions

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Question 1Thoracic Radiology

On a frontal chest radiograph, the right heart border is formed mainly by which structure?

  1. Right ventricle
  2. Right atrium Correct answer.
  3. Superior vena cava
  4. Ascending aorta

Explanation

The right heart border on a frontal radiograph is formed by the right atrium, with the superior vena cava above it. The right ventricle forms the anterior cardiac border and does not contribute to the right silhouette edge.

Question 2Thoracic Radiology

A patient with fever and cough has a chest radiograph showing a dense lobar opacity with air bronchograms in the right upper lobe. Which pattern does this represent?

  1. Atelectasis
  2. Consolidation Correct answer.
  3. Pneumothorax
  4. Pleural effusion

Explanation

Consolidation fills alveoli while airways remain aerated, producing air bronchograms within an opacity. Lobar atelectasis usually causes volume loss and displaces fissures, while effusion blunts the costophrenic angle.

Question 3Thoracic Radiology

Which radiographic sign is most characteristic of a tension pneumothorax?

  1. Bilateral hilar enlargement
  2. Mediastinal shift away from the affected side Correct answer.
  3. Blunting of the ipsilateral costophrenic angle
  4. Increased opacity of the affected hemithorax

Explanation

Tension pneumothorax raises intrathoracic pressure, shifting the mediastinum away from the side of the pneumothorax. The affected hemithorax is hyperlucent, not opaque, and the costophrenic angle is not the key finding.

Question 4Thoracic Radiology

A chest radiograph shows blunting of the left costophrenic angle with a meniscus-shaped opacity. What is the most likely cause?

  1. Lobar pneumonia
  2. Pleural effusion Correct answer.
  3. Pulmonary embolism
  4. Pneumoperitoneum

Explanation

A meniscus-shaped opacity blunting the costophrenic angle is the classic appearance of a pleural effusion. Fluid collects dependently and rises along the lateral chest wall, creating the meniscus.

Question 5Thoracic Radiology

Which finding on a chest radiograph most suggests left atrial enlargement?

  1. Double right heart border
  2. Widened paratracheal stripe
  3. Enlarged right hilum
  4. Splaying of the carina with a double contour on the right Correct answer.

Explanation

Left atrial enlargement produces a double right heart border and widens the carinal angle as the atrium enlarges. These signs reflect the atrium's position posteriorly and to the right.

Question 6Thoracic Radiology

A patient with a known malignancy develops multiple round pulmonary nodules of varying sizes. Which diagnosis is most likely?

  1. Pulmonary alveolar proteinosis
  2. Sarcoidosis
  3. Metastatic disease Correct answer.
  4. Tuberculosis

Explanation

Multiple pulmonary nodules of varying sizes suggest hematogenous metastases. Sarcoidosis tends to produce perilymphatic nodules, and alveolar proteinosis produces ground-glass or crazy-paving opacity.

Question 7Thoracic Radiology

Which radiographic finding is most consistent with a right lower lobe collapse?

  1. Blunting of the left costophrenic angle
  2. Hyperinflation of the right upper lobe
  3. Elevation of the right hemidiaphragm with a triangular opacity Correct answer.
  4. Shift of the trachea to the left

Explanation

Right lower lobe collapse causes volume loss with elevation of the right hemidiaphragm and a triangular opacity at the right base. The minor fissure may also descend.

Question 8Thoracic Radiology

A chest radiograph shows a continuous veil-like opacity over the entire hemithorax with contralateral mediastinal shift. What is the diagnosis?

  1. Total lung collapse Correct answer.
  2. Pneumonia
  3. Pulmonary edema
  4. Massive pleural effusion

Explanation

Complete opacification of a hemithorax with ipsilateral mediastinal shift indicates total lung collapse. A massive effusion also opacifies the hemithorax but shifts the mediastinum away from the opacity.

Question 9Thoracic Radiology

A patient with long-standing mitral stenosis has a chest radiograph showing prominent upper lobe vessels and Kerley B lines. Which process do these findings reflect?

  1. Pulmonary arterial hypertension
  2. Air trapping
  3. Interstitial fibrosis from prior infection
  4. Pulmonary venous hypertension Correct answer.

Explanation

Cephalization of pulmonary vessels and Kerley B lines reflect elevated pulmonary venous pressure. These are signs of pulmonary venous hypertension, often from left heart disease.

Question 10Thoracic Radiology

Which structure forms the left border of the mediastinum on a frontal chest radiograph just below the aortic arch?

  1. Left ventricle
  2. Main pulmonary artery Correct answer.
  3. Descending aorta
  4. Left atrium

Explanation

The main pulmonary artery forms the left mediastinal border below the aortic arch. The left atrial appendage and left ventricle lie below it.

Question 11Thoracic Radiology

A chest radiograph in a trauma patient shows a widened mediastinum and an abnormal aortic contour. Which injury should be suspected?

  1. Aortic injury Correct answer.
  2. Diaphragmatic hernia
  3. Rib fracture
  4. Pneumothorax

Explanation

A widened mediastinum with an abnormal aortic contour after trauma raises concern for traumatic aortic injury. Further evaluation with CT angiography is typically indicated.

Question 12Thoracic Radiology

Which chest radiographic finding is most typical of a large hiatal hernia?

  1. Apical cavitation
  2. Bilateral basal opacities
  3. A retrocardiac air-fluid level Correct answer.
  4. Unilateral hilar enlargement

Explanation

A hiatal hernia often presents as a retrocardiac mass containing an air-fluid level. The stomach herniates through the esophageal hiatus into the thorax.

Question 13Thoracic Radiology

A chest radiograph shows a solitary pulmonary nodule with a popcorn-like calcification. Which diagnosis is most likely?

  1. Metastasis
  2. Hamartoma Correct answer.
  3. Bronchogenic carcinoma
  4. Carcinoid tumor

Explanation

Popcorn-like calcification within a solitary nodule is characteristic of a hamartoma. This benign pattern reflects chondroid calcification.

Question 14Thoracic Radiology

Which radiographic feature best distinguishes a lung abscess from a cavitating carcinoma?

  1. Air-fluid level with surrounding consolidation Correct answer.
  2. Spiculated margins
  3. Thick irregular wall
  4. Satellite nodules

Explanation

A lung abscess typically shows a cavity with an air-fluid level and surrounding consolidation. Cavitating carcinoma more often has a thick, irregular wall without prominent surrounding consolidation.

Question 15Thoracic Radiology

A patient with sarcoidosis is most likely to show which pattern on chest radiography?

  1. Bilateral hilar lymphadenopathy Correct answer.
  2. Unilateral pleural effusion
  3. Apical cavitation
  4. Lower lobe honeycombing

Explanation

Sarcoidosis classically produces bilateral hilar lymphadenopathy, sometimes with right paratracheal adenopathy. Parenchymal disease, when present, tends to be perilymphatic and upper/mid zone predominant.

Question 16Thoracic Radiology

Which finding on a chest radiograph is most consistent with a pneumoperitoneum?

  1. Free gas under the right hemidiaphragm Correct answer.
  2. Air within the pleural space
  3. Air within the pericardium
  4. Air within the mediastinum

Explanation

Pneumoperitoneum appears as free subdiaphragmatic gas, typically best seen under the right hemidiaphragm on an upright film. It is a sign of hollow viscus perforation.

Question 17Thoracic Radiology

A chest radiograph demonstrates a deep sulcus sign on the right. What does this indicate?

  1. Right diaphragmatic paralysis
  2. Right pneumothorax Correct answer.
  3. Right pleural effusion
  4. Right lower lobe collapse

Explanation

The deep sulcus sign indicates a pneumothorax, particularly in a supine patient where air collects anteriorly and dependently. It appears as an unusually deepened costophrenic sulcus.

Question 18Thoracic Radiology

Which radiographic sign suggests a pulmonary embolism?

  1. Hampton hump Correct answer.
  2. Deep sulcus sign
  3. Kerley B lines
  4. Silhouette sign

Explanation

A Hampton hump is a wedge-shaped peripheral opacity due to pulmonary infarction from embolism. It is a relatively insensitive but characteristic sign.

Question 19Thoracic Radiology

A chest radiograph shows a ring shadow with an air-fluid level in the right lower lobe. Which diagnosis is most likely?

  1. Pleural effusion
  2. Pulmonary edema
  3. Pneumothorax
  4. Lung abscess Correct answer.

Explanation

A thick-walled cavity with an air-fluid level in a dependent lobe suggests a lung abscess. Aspiration-related abscesses favor the lower lobes and posterior segments.

Question 20Thoracic Radiology

Which finding best indicates cardiomegaly on a frontal chest radiograph?

  1. Cardiothoracic ratio greater than 0.5 Correct answer.
  2. Cardiothoracic ratio greater than 0.3
  3. Transverse cardiac diameter greater than 10 cm
  4. Widened azygos vein

Explanation

Cardiomegaly is suggested when the cardiothoracic ratio exceeds 0.5 on an erect frontal radiograph. This assumes a reasonably inspiratory film and no significant rotation.

Question 21Thoracic Radiology

A chest radiograph shows a continuous diaphragm sign. What does this indicate?

  1. Pneumomediastinum Correct answer.
  2. Pneumothorax
  3. Atelectasis
  4. Pleural effusion

Explanation

The continuous diaphragm sign occurs when mediastinal air outlines the central portion of the diaphragm, making it visible continuously across the midline. It indicates pneumomediastinum.

Question 22Thoracic Radiology

Which radiographic feature most suggests a benign solitary pulmonary nodule?

  1. Diffuse central calcification Correct answer.
  2. Interval growth over two years
  3. Pleural tail sign
  4. Spiculated margins

Explanation

Diffuse central or popcorn-like calcification in a nodule favors a benign etiology. Spiculation, pleural tagging, and interval growth raise concern for malignancy.

Question 23Thoracic Radiology

A patient with achalasia has a chest radiograph showing an absent gastric air bubble and a retrocardiac air-fluid level. Which mechanism explains the absent gastric bubble?

  1. Pyloric stenosis
  2. Failure of the lower esophageal sphincter to relax Correct answer.
  3. Excess gastric acid production
  4. Diaphragmatic paralysis

Explanation

Achalasia involves failure of lower esophageal sphincter relaxation, causing esophageal dilatation and retained contents. This can obscure or displace the gastric air bubble.

Question 24Thoracic Radiology

Which radiographic sign is characteristic of right upper lobe collapse?

  1. Hampton hump
  2. Deep sulcus sign
  3. Continuous diaphragm sign
  4. Golden S sign Correct answer.

Explanation

The Golden S sign describes the reverse-S contour formed by a collapsed right upper lobe with a central mass. It can also occur with right upper lobe collapse without mass.

Question 25Gastrointestinal and Abdominal Radiology

A 24-year-old man presents with right lower quadrant pain. Ultrasound shows a blind-ending, non-compressible tubular structure measuring 7 mm in diameter with surrounding hyperechogenicity. What is the most appropriate next step in management?

  1. CT abdomen and pelvis with IV contrast
  2. Oral antibiotics and outpatient follow-up
  3. Repeat ultrasound in 6 weeks
  4. Appendectomy Correct answer.

Explanation

A non-compressible appendix greater than 6 mm with periappendiceal inflammatory change is diagnostic of acute appendicitis, and the standard treatment is appendectomy. Imaging is already diagnostic, so further cross-sectional imaging is unnecessary.

Question 26Gastrointestinal and Abdominal Radiology

Which radiographic feature most reliably distinguishes a small bowel obstruction from a large bowel obstruction on an abdominal radiograph?

  1. Dilated loops located centrally
  2. Valvulae conniventes crossing the entire bowel lumen Correct answer.
  3. Absence of gas in the rectum
  4. Presence of multiple air-fluid levels

Explanation

Valvulae conniventes (plicae circulares) traverse the entire width of the small bowel lumen, whereas colonic haustra are incomplete bands that do not cross the full lumen. This morphology, not the number of air-fluid levels or loop position, reliably identifies small bowel.

Question 27Gastrointestinal and Abdominal Radiology

A patient with chronic hepatitis C undergoes surveillance ultrasound. Which finding most increases the likelihood that a focal hepatic lesion represents hepatocellular carcinoma?

  1. Arterial phase hyperenhancement with washout on portal venous phase Correct answer.
  2. Peripheral nodular enhancement with centripetal fill-in
  3. Well-defined anechoic lesion with posterior acoustic enhancement
  4. Homogeneous hyperechogenicity in a non-cirrhotic liver

Explanation

In a cirrhotic liver, a lesion showing arterial phase hyperenhancement followed by washout on portal venous or delayed phases meets noninvasive LI-RADS criteria for HCC. Peripheral nodular centripetal enhancement instead characterizes a hemangioma.

Question 28Gastrointestinal and Abdominal Radiology

A 62-year-old woman has a 9 cm heterogeneous left renal mass with a tumor thrombus extending into the renal vein. Which imaging feature best predicts surgical resectability?

  1. Size of the primary renal mass
  2. Degree of tumor enhancement
  3. Presence of calcification within the mass
  4. Tumor thrombus level within the IVC Correct answer.

Explanation

The cephalad extent of venous tumor thrombus determines surgical approach and resectability, with suprahepatic or intracardiac extension requiring more complex techniques. Primary tumor size and enhancement do not define the venous resection margin.

Question 29Gastrointestinal and Abdominal Radiology

Which finding on abdominal CT is the most specific sign of acute pancreatitis?

  1. Diffuse pancreatic enlargement
  2. Pancreatic duct dilation
  3. Peripancreatic fat stranding Correct answer.
  4. Peripancreatic fluid collections

Explanation

Peripancreatic fat stranding reflects peripancreatic inflammation and is among the most specific CT signs of acute pancreatitis. Enlargement and fluid collections are supportive but less specific.

Question 30Gastrointestinal and Abdominal Radiology

A 55-year-old man with a history of alcohol abuse presents with epigastric pain. CT shows a 4 cm fluid collection in the pancreatic body with a well-defined enhancing wall, 5 weeks after the onset of symptoms. What is the most likely diagnosis?

  1. Pancreatic adenocarcinoma
  2. Walled-off necrosis
  3. Acute peripancreatic fluid collection
  4. Pancreatic pseudocyst Correct answer.

Explanation

A well-defined encapsulated fluid collection arising more than 4 weeks after acute pancreatitis, without solid necrotic debris, is a pseudocyst. Earlier than 4 weeks the same collection is termed an acute peripancreatic fluid collection.

Question 31Gastrointestinal and Abdominal Radiology

Which CT feature is most characteristic of autoimmune pancreatitis?

  1. Multiple small cystic lesions
  2. Marked pancreatic atrophy with ductal calculi
  3. Sausage-shaped pancreas with a capsule-like rim Correct answer.
  4. Diffuse irregular calcifications

Explanation

Autoimmune pancreatitis classically produces a diffusely enlarged, sausage-shaped pancreas with a hypoattenuating capsule-like rim and delayed enhancement. Calcifications and atrophy are features of chronic pancreatitis.

Question 32Gastrointestinal and Abdominal Radiology

A 48-year-old woman has a 3 cm well-circumscribed mass in the pancreatic tail. MRI shows high T1 signal and progressive enhancement on dynamic sequences. What is the most likely diagnosis?

  1. Mucinous cystic neoplasm
  2. Solid pseudopapillary neoplasm
  3. Serous cystadenoma
  4. Neuroendocrine tumor Correct answer.

Explanation

Pancreatic neuroendocrine tumors are typically hypervascular, well-circumscribed, and show high T1 signal from their cellularity, with avid arterial enhancement. Serous and mucinous neoplasms are cystic.

Question 33Gastrointestinal and Abdominal Radiology

Which imaging modality is the reference standard for detecting and staging choledocholithiasis?

  1. Abdominal radiograph
  2. Endoscopic ultrasound Correct answer.
  3. Magnetic resonance cholangiopancreatography
  4. Transabdominal ultrasound

Explanation

Endoscopic ultrasound has the highest sensitivity and specificity for common bile duct stones and allows concurrent therapeutic intervention. MRCP is highly sensitive but slightly less so for small stones and lacks therapy.

Question 34Gastrointestinal and Abdominal Radiology

A 70-year-old man has painless jaundice. CT shows a dilated intrahepatic biliary tree with a normal-caliber pancreatic duct and a mass at the hepatic hilum. Which finding best characterizes a Klatskin tumor?

  1. Mass at the confluence of the right and left hepatic ducts Correct answer.
  2. Mass at the ampulla of Vater
  3. Mass in the gallbladder fundus
  4. Mass in the pancreatic head

Explanation

A Klatskin tumor is a perihilar cholangiocarcinoma arising at the confluence of the right and left hepatic ducts. It causes intrahepatic biliary dilation without extrahepatic dilation or pancreatic duct dilation.

Question 35Gastrointestinal and Abdominal Radiology

A 30-year-old woman has a 12 cm heterogeneous mass in the right hepatic lobe with a central scar. MRI shows a central scar that is hyperintense on T2 and enhances on delayed images. What is the most likely diagnosis?

  1. Hepatocellular carcinoma
  2. Fibrolamellar carcinoma
  3. Focal nodular hyperplasia Correct answer.
  4. Hepatic adenoma

Explanation

Focal nodular hyperplasia classically shows a central scar that is T2 hyperintense and enhances on delayed imaging, with the lesion becoming isointense to liver on hepatobiliary phase.

Question 36Gastrointestinal and Abdominal Radiology

Which CT finding is the most reliable sign of hepatic steatosis?

  1. Dilated intrahepatic bile ducts
  2. Enlarged common bile duct
  3. Hepatic attenuation greater than 60 HU
  4. Hepatic attenuation lower than splenic attenuation Correct answer.

Explanation

On unenhanced CT, liver attenuation less than that of the spleen indicates hepatic steatosis. Normal liver is slightly hyperattenuating relative to the spleen.

Question 37Gastrointestinal and Abdominal Radiology

A 40-year-old man with portal hypertension has a 2 cm nodule in a cirrhotic liver. Which imaging feature, when present, allows a noninvasive diagnosis of HCC without biopsy?

  1. Capsule appearance without enhancement
  2. T2 hyperintensity
  3. Arterial hyperenhancement with portal venous washout Correct answer.
  4. Restricted diffusion

Explanation

LI-RADS defines definite HCC in at-risk patients by arterial phase hyperenhancement with washout and/or capsule appearance. T2 hyperintensity and restricted diffusion are ancillary features.

Question 38Gastrointestinal and Abdominal Radiology

A 65-year-old man has a 5 cm mass in the cecum. Which imaging finding most strongly suggests malignant rather than inflammatory cecal wall thickening?

  1. Short segment of asymmetric thickening with loss of wall stratification Correct answer.
  2. Fat stranding confined to the pericecal fat
  3. Long segment of symmetric thickening
  4. Preserved stratification of the bowel wall

Explanation

Malignant thickening is typically focal, asymmetric, and destroys the normal stratified wall architecture. Inflammatory thickening tends to be longer, symmetric, and preserves stratification.

Question 39Gastrointestinal and Abdominal Radiology

Which feature on CT most reliably distinguishes a diverticular abscess from a colonic neoplasm?

  1. Presence of a fluid collection with an enhancing rim
  2. Location in the left lower quadrant
  3. Presence of gas within the collection Correct answer.
  4. Associated colonic wall thickening

Explanation

Extraluminal gas within a fluid collection strongly favors an abscess from perforated diverticulitis. Neoplasms may show wall thickening and even necrosis but rarely contain gas.

Question 40Gastrointestinal and Abdominal Radiology

A 28-year-old man has a 2 cm exophytic mass in the right kidney with a central scar and spoke-wheel enhancement. What is the most likely diagnosis?

  1. Angiomyolipoma
  2. Oncocytoma Correct answer.
  3. Renal cell carcinoma
  4. Renal cyst

Explanation

Renal oncocytoma classically shows a central stellate scar and spoke-wheel vascular enhancement, though the diagnosis is often confirmed after resection. Angiomyolipoma contains macroscopic fat.

Question 41Gastrointestinal and Abdominal Radiology

Which finding is most consistent with a simple renal cyst on ultrasound?

  1. Hypoechoic lesion with internal septations
  2. Hyperechoic lesion with shadowing
  3. Complex lesion with mural nodule
  4. Anechoic lesion with posterior acoustic enhancement Correct answer.

Explanation

A simple cyst is anechoic, has a thin imperceptible wall, and shows posterior acoustic enhancement. Septations, nodules, and internal echoes indicate complexity.

Question 42Gastrointestinal and Abdominal Radiology

A patient with sudden flank pain and hematuria has a CT showing a wedge-shaped, non-enhancing renal cortical defect. What is the most likely diagnosis?

  1. Renal laceration
  2. Acute pyelonephritis
  3. Renal infarction Correct answer.
  4. Renal abscess

Explanation

Renal infarction produces a wedge-shaped, non-enhancing cortical defect, often with a cortical rim sign from collateral capsular flow. Pyelonephritis shows striated enhancement, and abscess shows a rim-enhancing collection.

Question 43Gastrointestinal and Abdominal Radiology

Which CT finding is the most sensitive indicator of acute adrenal hemorrhage in a trauma patient?

  1. Enlarged, high-attenuation adrenal gland Correct answer.
  2. Adrenal calcification
  3. Adrenal cyst
  4. Adrenal nodule with low attenuation

Explanation

Acute adrenal hemorrhage appears as an enlarged gland with high attenuation from fresh blood. Calcification and low-attenuation lesions indicate chronic or cystic processes.

Question 44Gastrointestinal and Abdominal Radiology

A 50-year-old woman has a 3 cm left adrenal mass with attenuation of 5 HU on unenhanced CT. What is the most appropriate next step?

  1. MRI with chemical shift imaging
  2. Adrenalectomy
  3. PET-CT
  4. No further imaging needed; consistent with a benign adenoma Correct answer.

Explanation

An adrenal mass with unenhanced attenuation less than 10 HU is lipid-rich and consistent with a benign adenoma, requiring no further imaging in an otherwise asymptomatic patient.

Question 45Gastrointestinal and Abdominal Radiology

Which imaging finding most strongly suggests a malignant adrenal mass?

  1. Irregular margins with heterogeneous enhancement Correct answer.
  2. Delayed contrast washout greater than 60%
  3. Homogeneous low attenuation on unenhanced CT
  4. Size of 2 cm

Explanation

Irregular margins, heterogeneity, and delayed washout favor malignancy. Benign adenomas are homogeneous, low attenuation, and show rapid washout.

Question 46Gastrointestinal and Abdominal Radiology

A 35-year-old woman has a 6 cm right ovarian mass with a fat-fluid level on MRI. What is the most likely diagnosis?

  1. Endometrioma
  2. Serous cystadenoma
  3. Hemorrhagic cyst
  4. Mature cystic teratoma Correct answer.

Explanation

A fat-fluid level is highly specific for a mature cystic teratoma (dermoid), which contains macroscopic fat. Endometriomas show T1 hyperintensity without fat suppression.

Question 47Gastrointestinal and Abdominal Radiology

A 60-year-old man has a 4 cm abdominal aortic aneurysm with a crescent of high attenuation in the wall on unenhanced CT. What does this finding most likely represent?

  1. Impending rupture Correct answer.
  2. Mural thrombus
  3. Retroperitoneal fibrosis
  4. Atherosclerotic plaque

Explanation

A high-attenuation crescent in the aneurysm wall represents acute intramural hemorrhage and signals impending rupture. It is a sign requiring urgent evaluation.

Question 48Gastrointestinal and Abdominal Radiology

Which CT feature is most characteristic of acute mesenteric ischemia due to arterial occlusion?

  1. Thickened, enhancing bowel wall
  2. Increased mural enhancement
  3. Pneumatosis intestinalis Correct answer.
  4. Dilated bowel with air-fluid levels

Explanation

Pneumatosis intestinalis and portal venous gas are late but highly specific signs of transmural bowel infarction in acute mesenteric ischemia. Early ischemia may show decreased or absent mural enhancement.

Question 49Genitourinary Radiology

Which renal mass is most likely when a CT shows a large, heterogeneous tumor with macroscopic fat and calcification arising from the kidney?

  1. Oncocytoma
  2. Angiomyolipoma Correct answer.
  3. Renal cell carcinoma
  4. Renal cyst

Explanation

Macroscopic fat within a renal mass is the hallmark of angiomyolipoma, a benign tumor composed of vessels, smooth muscle, and fat. Large ones can be heterogeneous and contain calcification, but the presence of bulk fat is the defining feature.

Question 50Genitourinary Radiology

On an excretory-phase CT, which finding best confirms that a fluid collection communicates with the renal collecting system?

  1. Internal septations within the collection
  2. Delayed opacification of the collection by excreted contrast Correct answer.
  3. A thin enhancing rim around the collection
  4. Mass effect displacing the kidney

Explanation

Communication with the collecting system is demonstrated by contrast entering the collection on delayed excretory images. This distinguishes a calyceal diverticulum or forniceal rupture from a simple cyst or abscess.