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Adrenal Masses

Etiology Adrenal masses may be neoplastic, infectious, or hemorrhagic ( Box 71-1 ). Neoplasia is the most common cause for an adrenal mass seen on imaging. An incidentally detected adrenal mass as well as an adrenal mass in a patient with known malignancy elsewhere is most commonly due to a benign adenoma. Box 71-1 Causes of Adrenal Masses Benign Lesions Common Adenoma (lipid-rich) Adenoma (lipid-poor) Myelolipoma…

Enlarged Adrenal Glands

Recent technical advances in computed tomography (CT) and magnetic resonance imaging (MRI) have resulted in improved detection of subtle changes in adrenal gland morphology. The different morphologic patterns of adrenal gland enlargement on imaging can be classified as follows ( Figure 70-1 ): Diffuse enlargement Focal nodule or mass in a limb Multiple nodules in the gland Nodule with a smaller nodule within the nodule, the…

Urinary Tract Anomalies and Variants

Etiology Urinary tract anomalies encompass a wide range of abnormalities from the multiple varied components of the urinary tract—the renal parenchyma, the collecting system, the bladder, the urethra, and the vasculature. Anomalies result from alterations in the normal embryologic development of the urinary system. Detecting these anomalies requires an understanding of the embryologic development of the urinary system. Prevalence and Epidemiology Overall, it is estimated that…

Benign and Malignant Bladder Lesions

The urinary bladder is composed of the following four layers: 1. Urothelium: Transitional epithelium 2. Lamina propria: Vascular layer of connective tissue deep to the urothelium 3. Muscularis propria: Detrusor muscle 4. Adventitia: Connective tissue The bladder is an extraperitoneal organ with a serosal (peritoneal) covering present only over the dome. The remainder of the bladder is surrounded by perivesical fat. This chapter reviews the benign…

Benign and Malignant Ureteral Strictures

A ureteral stricture is a narrowing of the ureter that results in a functional obstruction. It may be the result of a variety of benign and malignant causes, which may be classified as intrinsic or extrinsic processes. The clinical presentation of patients with ureteral strictures depends on the cause of the stricture and the severity and duration of the associated obstruction. In acute ureteral obstruction, pain…

Urinary Tract Obstruction

Etiology Urinary tract obstruction (UTO) is a syndrome that may be caused by a wide range of pathologic processes. It may vary in the following: Degree: May be partial or complete. Site: May be unilateral or bilateral and may occur at any level of the urinary tract from the calyces to the urethral meatus. Duration: May be acute or chronic. Demographics: Common causes vary among prenatal,…

Renal Vascular Diseases

Renovascular Hypertension Etiology The most common cause of renovascular hypertension is renal artery stenosis, which may be caused by atherosclerosis (70% to 90%) or less commonly by fibromuscular dysplasia (10% to 30%). Rare causes of renal artery stenosis include arteritis, arterial dissection, and neurofibromatosis. Prevalence and Epidemiology Renovascular hypertension pertains to the causal relationship between renal artery stenosis and its clinical consequences, namely, hypertension and/or renal…

Diffuse Renal Parenchymal Diseases

Renal failure may be classified as prerenal when secondary to a reduction in the renal perfusion pressure gradient, renal when the result of intrinsic disease of the renal parenchyma, and postrenal when secondary to an abnormality of urine outflow. Prerenal renal failure may arise from alterations in renal artery perfusion or venous drainage. Renal artery stenosis results in decreased perfusion. Renal vein thrombosis results in increased…

Benign, Malignant, and Cystic Focal Renal Lesions

This chapter discusses benign and malignant renal lesions ( Box 63-1 ) with a separate note on cystic lesions based on the Bosniak classification. Box 63-1 Benign and Malignant Focal Renal Lesions Benign Lesions Simple renal cyst Oncocytoma Angiomyolipoma Leiomyoma Mesoblastic nephroma Adenoma Malignant Lesions Renal parenchymal tumors, including renal cell carcinoma subtypes Urothelial carcinoma Secondary renal tumors Lymphoma and leukemia Metastatic lesions Pediatric malignant tumors…

Imaging of the Kidneys and Urinary Tract

Anatomy Overview The Kidney The kidneys are paired retroperitoneal organs that primarily function in the excretion of metabolic waste. They are bean shaped with a convex lateral border and a concave medial surface known as the renal hilum. On intravenous contrast-enhanced studies, sequential enhancement of the renal vasculature, cortex, medulla, and collecting system occurs. In the early nephrographic phase, also called the corticomedullary phase, there is…

Lymph Node Imaging Techniques and Clinical Role

Lymph Node Imaging Techniques Imaging evaluation of lymph nodes forms an integral component of staging of various malignancies, including lymphomas, and is also helpful in the evaluation of certain infective and inflammatory processes within the abdomen. This has special relevance in the abdomen because the lymph node system in this region is not readily accessible for clinical examination or tissue sampling. Therefore, accurate identification and characterization…

Diffuse Splenic Lesions

Normal Variants and Congenital Anomalies The spleen begins to develop during the fifth week of embryogenesis when mesenchymal cells aggregate between the two leaves of the dorsal mesogastrium to form a lobulated embryonic spleen. Rotation of the stomach and growth of the dorsal mesogastrium translocate the spleen from the midline to the left side of the abdominal cavity. The left aspect of the mesogastrium fuses with…

Focal Splenic Lesions

Splenic Cysts Non-Neoplastic and Nonparasitic Splenic Cysts Etiology Non-neoplastic and nonparasitic splenic cysts are classified into primary (i.e., epithelial, true) and secondary (i.e., pseudocysts, false) cysts, depending on the presence or absence of the internal epithelial lining. Primary or epithelial cysts are considered congenital or developmental in origin. Trauma is the most likely etiologic factor of pseudocysts or secondary cysts, and other causes are considered to…

Gallbladder and Bile Duct Functional Imaging

Technical Aspects Functional imaging of the gallbladder and bile ducts is a valuable tool, providing critical information for the management of conditions of the biliary system. Modern functional techniques are noninvasive and can permit earlier and improved disease characterization resulting in appropriate and timely patient care. Ultrasonography is typically used as the initial modality for assessment of the biliary tree because it is fast, inexpensive, and…

Focal Gallbladder Wall Thickening

Focal gallbladder wall thickening is often an imaging diagnosis and encompasses a wide variety of differential diagnoses. Polypoid lesions of the gallbladder form an important group of conditions that are included in the differential diagnosis of focal gallbladder wall thickening and can be divided into neoplastic and non-neoplastic groups ( Figure 57-1 ). The neoplastic group includes adenomas, leiomyomas, neurofibromas, and gallbladder carcinoma. The non-neoplastic group…

Diffuse Gallbladder Wall Thickening

Diffuse gallbladder wall thickening is commonly encountered in diagnostic settings. The ability of ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) to directly visualize the thickened gallbladder wall ascertains the importance of this condition. Ultrasound is the initial imaging technique for evaluation of suspected gallbladder disease. CT plays the role of a problem-solving tool in inconclusive ultrasound examinations, in staging of diseases, and as the…

Extrahepatic Bile Duct Tumors

Etiology The exact pathogenesis of bile duct carcinoma has not been described, but predisposing factors are similar to those causing intrahepatic bile duct neoplasms. It is believed that long-standing inflammation causes metaplasia and, finally, carcinogenesis. Prevalence and Epidemiology Tumors of the biliary tract constitute 2% of all cancers found at autopsy. The vast majority of bile duct tumors are extrahepatic (87% to 92%). Patients are typically…

Intrahepatic Bile Duct Tumors

Etiology The exact pathogenesis of bile duct carcinoma has not been described, but predisposing factors include long-standing inflammation, parasitic infestation, toxin and drug exposures, and genetic abnormalities. It is believed that repeated inflammation leads to chronic bile duct injury with formation of premalignant lesions. DNA alterations secondary to genetic mutations, bile salt exposure, or other carcinogens can predispose to biliary epithelial proliferation and subsequent tumorigenesis. Intrahepatic…

Tumors of the Gallbladder

Etiology The precise cause of gallbladder carcinoma is unknown, but cholelithiasis and pancreaticobiliary malformations are major risk factors. Gallstones and reflux of pancreaticobiliary enzymes are thought to result in chronic repetitive inflammation of the gallbladder mucosa that, over time, may undergo malignant transformation into invasive carcinoma. Prevalence and Epidemiology Gallbladder carcinoma is the most common primary biliary tract cancer and sixth most common gastrointestinal malignancy. It…

Dilated Bile Ducts

Etiology Biliary dilatation can occur as a result of biliary obstruction, from an altered functional state (e.g., after cholecystectomy or with sphincter of Oddi dysfunction), or uncommonly as a result of a choledochal cyst. The role of imaging is to identify a bile duct obstruction and define its level and cause. The cause may be intraluminal, mural, or extrinsic ( Figure 52-1 ). Cholangiographic and cross-sectional…