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Pancreatic Neuroendocrine Tumors (Islet Cell Tumors)

Pancreatic neuroendocrine tumors (PNETs), also known as “islet cell tumors,” represent a group of rare neoplasms of the neuroendocrine cells of the gastropancreatic system ( Fig. 132.1 ). PNETs constitute fewer than 5% of the pancreatic tumors. They may be functioning tumors producing distinct clinical syndromes based on the hormone (gastrin, insulin, and glucagon) produced, or nonfunctioning tumors (60%–90%), diagnosed because of their mass effect or…

Cystic Neoplasms of the Pancreas

The increasing use of abdominal imaging studies such as abdominal ultrasound, computed tomography (CT) scan, and magnetic resonance imaging (MRI) has contributed to the incidental detection of pancreatic cysts, some of which may be malignant and others premalignant or benign. Overall in asymptomatic patients, 2.5% have pancreatic cysts, and the number increases to 10% in those older than 70 years. Once detected, the clinician should not…

Pancreatic Cancer

Clinical Picture Globally, pancreatic cancer causes more than 331,000 deaths per year, ranking as the seventh leading cause of cancer death in both sexes together. In the United States, pancreatic cancer is the fifth leading cause of cancer mortality. In 2018, approximately 55,400 individuals are expected to be diagnosed with pancreatic cancer. Because the 1-year mortality is high, approximately 44,330 will die of pancreatic cancer. In…

Chronic Pancreatitis

Disease Forms and Clinical Picture The cardinal manifestations of chronic pancreatitis (CP) are recurrent or persistent abdominal pain that lasts for months to years, accompanied by diabetes, steatorrhea, and pancreatic calculi. Morphologically, the disease is characterized by destruction and loss of exocrine parenchyma that may be focal, segmental, or diffuse, as well as by fibrosis of the pancreas ( Fig. 129.1 ). These changes may be…

Acute Pancreatitis

Etiology and Clinical Picture Acute pancreatitis (AP), an inflammatory disorder of the pancreas characterized clinically by abdominal pain and biochemically by elevated levels of serum amylase and lipase, may present as a mild, self-remitting disorder or as a fulminant disease with many local and systemic complications. The revised Atlanta classification of 2012 addresses a number of issues of the disease in adults ( Table 128.1 ).…

Cystic Fibrosis

Cystic fibrosis (CF) is a progressive genetic disease transmitted by an autosomal recessive mechanism. Among Caucasians, the frequency is 1 in 2000 to 3000 live births but much less in African Americans (1 : 15,000) and Asian Americans (1 : 30,000). The carrier rate in Caucasians is 1 in 25. Individuals with one copy of the nonfunctioning CF gene are asymptomatic carriers but do not suffer from the disease. Early…

Other Helminth Infections: Trichinella spiralis and Flukes

Trichinosis The most common Trichinella species in the United States is Trichinella spiralis, which is almost worldwide in its distribution. However, other Trichinella species infect humans in Africa and in the arctic regions. Humans become infected by eating undercooked pork meat. The main reservoir is the pig. The life cycle of Trichinella has an intestinal phase and a muscular phase. When the uncooked meat is eaten,…

Tapeworms (Cestodes)

The four clinically important cestodes, or flatworms, are Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), Diphyllobothrium latum (fish tapeworm), and Hymenolepis nana (dwarf tapeworm). The tapeworms live in the intestine of vertebrates (the primary or definitive host) but spend a part of their lifecycle in animals (intermediate hosts). The term proglottid refers to one of the segments of a tapeworm formed by a process of…

Hookworm Disease (Necatoriasis and Ancylostomiasis)

Hookworm disease is caused by either of two nematodes, Necator americanus (New World hookworm) or Ancylostoma duodenale (Old World hookworm). N. americanus is found in the Western Hemisphere in tropical and subtropical areas and also in Africa and Asia. A. duodenale is found in the Mediterranean region and in parts of Europe and Asia; it is rarely, if ever, seen in the Western Hemisphere. The worms…

Strongyloidiasis

Strongyloidiasis, caused by the nematode Strongyloides stercoralis ( S. sterocralis, threadworm), is prevalent in Asia, Africa, Oceania, South America, Southern Europe, and southeastern states of the United States (Kentucky, Virginia, Tennessee, and North Carolina). In the United States, the predisposing factors for the infection include immigrants and military veterans who have lived in endemic areas, and patients with malnutrition, chronic obstructive pulmonary disease (COPD), chronic renal…

Ascariasis

An estimated 807 to 1221 million people in the world are infected with Ascaris lumbricoides, the largest helminth to infect humans. The adult male measures 15 to 25 cm and is smaller than the female, which may be as large as 35 cm. These helminths may live for 10 to 18 months and usually copulate in the lumen of the small intestine; the mature female may produce up…

Enterobiasis

Enterobiasis is caused by the pinworm Enterobius vermicularis. This nematode is probably the most common parasite to host on humans because it flourishes in temperate and tropical climates. The small, spindle-shaped, white round adult worms inhabit the cecum and appendix, and adjacent parts of the large and small intestines; their heads attach to the intestinal mucosa. A male worm measures 2 to 5 mm in length, and…

Intestinal Helminths: Trichuriasis

Intestinal helminths are common worldwide, but the most important and common soil transmitted helminthic infections are by Ascaris lumbricoides, Trichuris trichiura, and the two hookworm species Ancylostoma duodenale and Necator americanus. Trichuris trichiura is commonly known as the “whipworm” because of its morphology. Its life cycle is simpler than that of the other helminths ( Fig. 117.1 ). Trichuris eggs are ingested in contaminated food and…

Giardia lamblia and Other Protozoan Infections

Giardia lamblia, also called Giardia intestinalis (or G. duodenalis ), is a flagellated intestinal protozoan ( Fig. 116.1 ). In the United States an estimated 1.2 million individuals are reported to develop gastrointestinal symptoms annually because of giardial infection. G. lamblia is the most frequently identified intestinal parasite in the United States. Open full size image Fig. 116.1 Giardia lamblia and Other Protozoans. The life cycle…

Amebiasis

Worldwide, amebiasis is caused by Entamoeba histolytica (E. histolytica) and is the third most common parasitic disease, affecting 50 million people and causing 100,000 deaths per year. It is highly prevalent in Central America, South America, Africa, and Asia. In the United States, E. histolytica represents the third most frequently identified protozoan infection from human specimens (1.2 cases per 100,000 persons), following Giardia lamblia and Cryptosporidium…