Organizational Approach to Abdominal Diseases
- Most information about imaging abdominal disorders, including the gastrointestinal and genitourinary systems, fits neatly into an organ-by-organ framework. However, this approach makes it difficult to discuss diseases or conditions with manifestations throughout the abdomen and beyond. For this reason, some conditions are best discussed from a systemic perspective. Doing so provides a more accurate portrayal of these entities and avoids unwanted redundancy.
- Because many systemic disorders affect lymph node groups, neural structures, or major vessels throughout the abdomen, medical illustrations provide a helpful reminder of important anatomical considerations.
- Multiple endocrine neoplasia syndromes are caused by genetic defects and affect ~ 1 in 5,000-50,000 people. These syndromes predispose patients to tumor development within 2 or more components of the endocrine system.
- Among the most interesting and challenging of the congenital syndromes are the phakomatoses or neurocutaneous syndromes. These include neurofibromatosis, tuberous sclerosis, and von Hippel-Lindau disease. As the name implies, these patients are at risk for many benign and malignant neoplasms affecting the skin, CNS, and multiple abdominal viscera. Although all of these exhibits an autosomal dominant pattern of inheritance, many affected individuals have no positive family history. Neurofibromatosis is the most common of the phakomatoses (1 in 3,000), while von Hippel is the least common (1 in 30,000-50,000).
- Systemic infections (including AIDS, tuberculosis, and mononucleosis) are discussed, along with important clues to help identify the infectious and neoplastic diseases they may cause or simulate.
- Degenerative conditions, such as sarcoidosis and vascular disorders, are rarely limited to a single organ. These are presented in all their guises, along with tips as to how to address differential diagnoses.
- Foreign bodies may be encountered throughout the gastrointestinal and genitourinary system and are well-known to be found repeatedly in certain individuals. Keys to recognition on imaging and avoiding common pitfalls are covered here.
- Many malignant neoplasms are, by their very nature, systemic processes, such as lymphoma, leukemia, and malignant melanoma. Therefore, taking a systemic approach to such diagnoses gives us the opportunity to bring together some general principles about the presentation, diagnosis, and management of these important diseases.
- While some conditions, such as systemic hypotension or hypervolemia, do not represent disease per se, they can result in important clinical and imaging abnormalities that must be recognized to avoid misguided patient management.
- Finally, with the continued evolution of systemic anticancer therapies, quantification of tumor burden using imaging, such as computed tomography (CT) and magnetic resonance (MR), is increasingly being used to assess the effectiveness of anticancer drugs. This requires unified evaluation and disease-specific treatment response criteria are discussed and compared to provide a practicing radiologist an overview of the methodology.
- Plain radiography maintains an important role for surveillance of some generalized disease processes, such as the osseous and visceral manifestations of sickle cell anemia or cystic fibrosis.
- Ultrasound is an important imaging tool for the evaluation of biliary, vascular, gynecologic, and scrotal pathology, but it lacks both sensitivity and specificity in evaluating other processes, especially bowel pathology.
- CT has become the essential tool for the comprehensive evaluation of most traumatic, inflammatory, and neoplastic abdominal processes. In patients with cancer, for instance, the ability to quickly and accurately examine different anatomic areas (thorax, abdomen, and pelvis), organs, and structures of different composition (e.g., lung, liver, and bone) is a tremendous advantage. Thus, there is continued growth and popularity of CT even in this era of powerful "competing" modalities, such as positron emission tomography (PET) and MR imaging. PET and MR imaging do serve an important role as problem-solving tools for evaluating abdominal pathology. MR, with its excellent soft tissue characterization, is particularly helpful in evaluating masses within solid abdominal organs.
- Catheter angiography remains the most accurate means of identifying certain vascular disorders and often results in catheter-based therapies in the same setting. For vasculitides, which routinely affect vessels throughout the body, angiography maintains an essential diagnostic and therapeutic role.
Related Differential Diagnoses