bluuebunny/crossref_metadata_2025 huggingface dataset:
Clostridium difficile
Authors: Eyre David W. , Wilcox Mark H.
Published: February 2020

Clostridium difficile (recently renamed as Clostridioides difficile) is a Gram-positive spore-forming anaerobic bacillus that is ubiquitous in nature, and particularly common in healthcare environments. Its spores are part of the colonic flora in about 2–3% of healthy adults, with colonization rates increasing, typically up to 10–20%, during hospitalization. Disease occurs when the organism shifts from quiescent spores to replicating vegetative cells with toxin (A and B) production; this happens when there is inhibition of the resident colonic flora (gut microbiome) by prescribed antibiotics, although cases can occur when no such precipitant is identified. C. difficile infection is now recognized as the most important bacterial enteric pathogen in wealthier countries, epidemics, and outbreaks of which are common, most notoriously now due to the ribotype 027 (NAP-1) strain that is associated with more severe disease and poor outcomes.
Nocardiosis
Authors: Hay Roderick J.
Published: February 2020

Nocardia species—Nocardia asteroides, N. brasiliensis, and N. otidiscaviarum—are Gram-positive, filamentous, partially acid-fast bacteria. They are occasionally detectable in environmental sources such as soil, but they rarely cause infections in humans, although they can give rise to a variety of different diseases. In healthy individuals, most commonly in the tropics, they can present with cutaneous abscesses or subcutaneous infections (actinomycetoma) in which the organisms are present as clusters of filaments or grains. In immunocompromised patients they cause a disseminated or localized deep infection, with particular sites affected being the lungs or brain. Diagnosis of Nocardia infection depends on culture, although histopathology is very useful in Nocardia actinomycetomasiii. Antibiotic treatment is typically with a sulphonamide (often as co-trimoxazole for lung infections), but combinations of drugs are usually given because the responsiveness of Nocardia species is very variable.
Syphilis
Authors: Read Phillip , Donovan Basil
Published: February 2020

Syphilis results from infection with the spirochaete Treponema pallidum subsp. pallidum, for which humans are the only known natural host. In adults it is transmitted primarily by sexual contact. The organism gains entry into the body through small breaks in the skin or the intact mucosal surfaces of the genitals, mouth, or anus, and is able to invade and survive in a wide variety of tissues.

Since the availability of penicillin, syphilis has become primarily (>90%) a disease of less affluent countries or of minority subpopulations in more affluent countries with poor access to healthcare. It is also a disease of people with rapid rates of partner change (e.g. men who have sex with men and commercial sex workers).
Rickettsioses
Authors: Griffiths Karolina , Eldin Carole , Raoult Didier , Parola Philippe
Published: February 2020

Rickettsioses are mild to life-threatening zoonoses caused by obligate intracellular bacteria of the order Rickettsiales (family Rickettsiaceae). Arthropods, including ticks, fleas, and mites, are implicated as their vectors, reservoirs, or amplifiers. With an increasing number of new pathogens and recognition of new pathogenicity and affected geographical areas over the past few decades, there is a better understanding of the scope and importance of these pathogens, particularly as a paradigm to understanding emerging and remerging infections. The taxonomy has undergone numerous changes, with now three main groups classified as rickettsioses according to morphological, antigenic and metabolic characteristics: (1) Rickettsioses due to the bacteria of the genus Rickettsia, including the spotted fever group, typhus groups (Rickettsiaceae), (2) Ehrlichioses and Anaplasmoses due to bacteria of the Anaplasmataceae and (3) scrub typhus due to Orientia tsutsugamushi.
Coxiella burnetii infections (Q fever)
Authors: Marrie Thomas J.
Published: February 2020

Q fever is a zoonosis caused by Coxiella burnetii, an intracellular Gram-negative spore-forming bacterium, the common animal reservoirs of which are cattle, sheep, and goats. Rats and mice have been implicated as reservoirs in some areas. In French Guiana the three-toed sloth is the reservoir. C. burnetti is trophic for the endometrium and mammary glands of female animals, and during pregnancy the organism reaches very high concentrations in the placenta such that at the time of parturition organisms are aerosolized and contamination of the environment occurs. Inhalation of even one microorganism can result in infection. Diagnosis is confirmed by serological testing: in acute disease antibodies to phase II antigen are higher than those to phase I, whereas the reverse is true in chronic disease.
Paracoccidioidomycosis
Authors: Shikanai-Yasuda M.A.
Published: February 2020

Paracoccidioidomycosis is a systemic endemic mycosis caused by dimorphic fungus found in soil and in a variety of animals, and transmitted to humans by inhalation. It is restricted geographically to Central and South America, where it is the most common endemic chronic human mycosis, acquired in rural and periurban areas. In its chronic form is is more frequqnt in men than women (10:1) and in the acute form, it is equally distributed among boys and girls (children, adolescents and young adults) areas. It involves the lung and mucous membranes, adrenal, gastrointestinal, central nervous system and other organs in thechronic form and the phagocytic mononuclear system in the acute form. Diagnosis is made by direct microscopy or culture from sputum, plus histopathology.and/or serology, which is useful for therapeutic control. Treatment is required for long courses of oral drugs (itraconazole or sulfamethoxazole– trimethoprim) for non severe cases) or intravenous amphotericin B or other amphotericin formulations in severe cases followed by oral drugs.for severe cases. Sequels are represented by microstomia, laryngeal/tracheal/bronchial stenosis, pulmonary emphysema/fibrosis, respiratory insufficiency, and cor pulmonale.
Human African trypanosomiasis
Authors: Brun Reto , Blum Johannes
Published: February 2020

Human African trypanosomiasis (sleeping sickness) is caused by subspecies of the protozoan parasite Trypanosoma brucei. The disease is restricted to tropical Africa where it is transmitted by the bite of infected tsetse flies (Glossina spp.). Control programmes in the 1960s were very effective, but subsequent relaxation of control measures led to recurrence of epidemic proportions in the 1980s and 1990s. Control is now being regained. Untreated human African trypanosomiasis is almost invariably fatal. Specific treatment depends on the trypanosome subspecies and the stage of the disease. Drugs used for stage 1 include pentamidine and suramin, and for stage 2 include melarsoprol, eflornithine, and nifurtimox, but regimens are not standardized, and treatment is difficult and dangerous; all of the drugs used have many side effects, some potentially lethal.
Cutaneous filariasis
Authors: Burnham Gilbert
Published: February 2020

The cutaneous filariae are transmitted by biting insects. Some, such as Onchocerca volvulus, are transmitted by Simulium flies and can cause debilitating conditions such as visual impairment and disfiguring skin conditions. The Mansonella infections are transmitted either by Simulium flies or biting midges (genus Culicoides), but consequences of infections are general mild. Loa loa is transmitted by the bite of the Chrysops fly. Loaisis is manifest by adult worms periodically passing beneath the sclera and by subcutaneous swellings, usually of the forearm. Onchocerciasis, or river blindness, historically occurred in 34 countries in Africa, Yemen, and Latin America. It is estimated that 18 million people are infected, and 87 million at risk of infection. Most are in Africa. Mass treatment with ivermectin has now greatly lessened the ocular burden of infection.
Strongyloidiasis, hookworm, and other gut strongyloid nematodes
Authors: Brown Michael
Published: February 2020

Strongyloides stercoralis and hookworms are common soil-transmitted nematodes in tropical and subtropical regions. After the organisms penetrate exposed skin, most infections are asymptomatic, but heavy infections can result in significant morbidity. The roundworm S. stercoralis infects an estimated 30 million to 100 million people. Infection is persistent and may present decades after exposure. Diagnosis is usually by microscopy or culture of stool; serology is useful as a screening test. Treatment is typically with ivermectin or albendazole. Improved sanitation and appropriate footwear can reduce the acquisition of infection. Hookworm infections, mainly caused by Ancylostoma duodenale and Necator americanus, affect more than 500 million people, predominantly in sub-Saharan Africa and Asia. Population-based control programmes, using single-dose antihelmintic therapies, aim to reduce anaemia, and improve childhood growth and cognitive development in countries with high prevalence of soil-transmitted helminths.
Cestodes (tapeworms)
Authors: Knight Richard
Published: February 2020

Adult tapeworms maintain anchorage to the host small-gut mucosa by means the scolex, a holdfast structure. The rest of the body forms the strobila and consists of a chain of flattened proglottids, which proliferate just behind the scolex. The life cycle then includes larval stages in one or more intermediate hosts. Many species of tapeworm, all zoonoses, infect humans as adult worms or larval stages. Serious disease can result when larval stages occur accidentally in humans, whereas infections by the adult stages often cause little harm. Two groups of cestode infect humans: the Cyclophyllidea and the Pseudophyllidea. The former have a terrestrial life cycle and cystic larvae; the latter have an aquatic cycle and worm-like larvae.
Urethritis
Authors: Horner Patrick
Published: February 2020

Urethritis is defined as detectable urethral inflammation in the presence of symptoms or an observable urethral discharge. It is conventionally classified into gonococcal urethritis (GU, caused by Neisseria gonorrhoeae) and non-gonococcal urethritis (NGU, caused by Chlamydia trachomatis, Mycoplasma genitalium, and other causes, but with no known pathogen detected in over 30% of cases). Diagnosis is by urethral smear and microbiological investigations. Treatment with appropriate antibiotics should be given only to those with proven urethritis, and the diagnosis and its implications should be discussed with the patient. Partner notification is essential, not only to prevent re-infection but also to prevent onward transmission from partner(s) and the development of complications if left untreated.
Genital ulceration
Authors: French Patrick , Patel Raj
Published: February 2020

Genital ulceration can be caused by many common and rare sexually transmitted infections (STIs), dermatological conditions, and trauma. Key to making a specific diagnosis that will direct treatment is a standard sexual and travel history followed by appropriate diagnostic tests. Genital ulcer disease is a major risk factor for the acquisition and transmission of HIV. Various classifications and algorithms are proposed to help identify pathogens and guide immediate management, but care must be taken when working through these.
Anogenital lumps and bumps
Authors: de Vries Henry J.C. , Lacey Charles J.N.
Published: February 2020

Anogenital lesions can be related to sexually transmitted infections, physiological variants that worry the patient, or dermatological conditions unrelated to infection. The clinical diagnostic approach is based on the colour of the lesion and the skin layer involved (epidermis, dermis, or subcutaneous fat compartment). A strong element of pattern recognition is involved in accurate diagnosis. This can only be learnt with experience, but is essential for determination of appropriate treatment. In this chapter the most common anogenital dermatological diagnoses are discussed using an approach based on the colour of the lesion and the skin layer involved. Many of these infections are asymptomatic, enabling ongoing transmission. Some sexually transmitted infections cause symptoms, especially in the anogenital region, and therefore need to be considered in the differential diagnosis of patients presenting with anogenital lesions.
Diving medicine
Authors: Denison David M. , Glover Mark A.
Published: February 2020

Diving remains the principal means of exploring and exploiting shallower underwater zones. Immersion and rapid change in pressure with depth cause most problems unique to diving. Gas density, partial pressures, and solubility vary proportionately with ambient pressure. At elevated partial pressure, nitrogen becomes narcotic, as can other inert gases, and contaminants barely detectable at the surface can become toxic. Hyperoxia irritates the lungs and the central nervous system, sometimes causing generalized seizures. A safe gas mixture at depth can become hypoxic as the partial pressure of oxygen decreases during the return to surface. Ventilation is compromised at depth and failure of CO2 elimination increasingly limits activity. Some divers are not distressed by elevated CO2, but this does not protect them from its toxic effects.
Air pollution and health
Authors: Kurmi Om P. , Lam Kin Bong Hubert , Ayres Jon G.
Published: February 2020

The term ‘occupational and environmental health’ includes any act of emission of any substance, likely to be hazardous in nature, which is either not originally present or is present in a higher concentration than normal in the natural atmosphere. Most air pollutants are generated from human activities (e.g. energy, transportation, industry, agriculture), but natural events in the living (e.g. methane emissions in wetlands) and non-living environment (e.g. volcanic eruptions) also contribute to atmospheric air pollution, although their relative importance has declined since the Industrial Revolution and the advent of modern fossil fuel-based economies. Pollutants may be classified as (1) primary (emitted directly into the atmosphere) or secondary (formed in the air through chemical reactions with other pollutants and gases); (2) indoor or outdoor; (3) gaseous or particulate.
Cold
Authors: Stroud Michael A.
Published: February 2020

Humans are poorly adapted to cold, which can cause hypothermia, non-freezing cold injury, and frostbite. Hypothermia occurs especially with wind and wetting, and is seen indoors in older people and those who are thin. Non-freezing cold injury occurs when skin temperatures below 12°C are maintained for prolonged periods, particularly in water. This causes paralysis of nerve and muscle, which can be permanent (e.g. trench foot). Meanwhile, with frostbite the frozen tissues initially appear hard, white, and anaesthetic, but with rewarming become swollen, painful, and blistered. There may be irreversible necrosis, but initial appearances can be misleading and hence early amputation should be avoided. Once thawed, frostbite treatment is similar to that for burns.
Drowning
Authors: Fenner Peter J.
Published: February 2020

Drowning is a major preventable cause of death, most frequently in children and in developing countries. Aspiration (whether of salt or fresh water) is usual in drowning and near-drowning (known as non-fatal, or submersion injury) and leads to cardiac arrest within a few minutes. Death or severe neurological impairment occurs after submersion for more than 5–10 min, but much longer durations may be tolerated in hypothermic conditions. Prognosis cannot reliably be predicted, but cardiovascular status is a better prognostic indicator than neurological presentation. Patients who are neurologically responsive at the scene of immersion, in sinus rhythm and with reactive pupils, have good outcomes. Those who are asystolic on arrival at hospital and remain comatose for more than 3 h have a poor prognosis unless they are hypothermic. Patients with a normal chest radiograph on admission usually survive.
Disasters: Earthquakes, hurricanes, floods, and volcanic eruptions
Authors: Baxter Peter J.
Published: February 2020

Natural disasters (including earthquakes, volcanic eruptions, hurricanes, floods) cause tens of thousands of deaths and adversely affect the lives of hundreds of millions of people every year. The trend is for the impacts to increase alongside the continuing expansion of human populations into regions at risk and with environmental degradation making human settlements more vulnerable, especially in heavily urbanized areas and megacities. This reckless development is going on in most countries of the world, even in places prone to natural disasters. Recent remarkable advances in forecasting weather-related disasters (hurricanes and floods) have to be matched with adequate disaster preparedness in those communities at high risk if they are to be translated into effective warnings, especially in low-income countries. Earthquakes remain notoriously unpredictable and have the greatest mortality toll of all natural disasters.
Poisonous plants
Authors: Eddleston Michael , Persson Hans
Published: February 2020

Many plants contain toxic substances—heterogeneous in chemical composition and diverse in toxic effects. When classifying plant poisonings, a pragmatic approach is to look at the main clinical effects, but it should be emphasized that few plant toxins produce just one type of symptom and that symptomatology is often multiple, with some features predominating. Ingestion of, or contact with, poisonous plants is common but serious plant poisoning is rare worldwide because most plant exposures are accidental: the majority occur in small children, the ingested dose is usually small, and no treatment is required. Treatment of severe plant poisoning includes careful decontamination and symptomatic and supportive care. Specific antidotes are only available for poisoning by plants containing belladonna alkaloids (physostigmine), cardiac glycosides (digoxin-specific Fab fragments), and cyanogenic agents (dicobalt edetate, hydroxocobalamin).
Vitamins
Authors: Hill Tom R. , Bender David A.
Published: February 2020

The vitamins are a disparate group of organic compounds that are required in small amounts (mg or µg per day) for the maintenance of normal health and metabolic integrity. Four vitamins (A, D, E, and K) are lipid soluble, while the others are water-soluble. Determining how much of any particular vitamin is required for health is not straightforward, a standard technique being to deprive volunteers of the vitamin in question until there is detectable metabolic change and then replete with graded doses of the vitamin until normal metabolism is restored, with the reference intake (recommended daily intake or amount or recommended dietary allowance) set at 2× standard deviation above the average requirement.
Severe malnutrition
Authors: Jackson Alan A.
Published: February 2020

Severe malnutrition is the consequence of systemic deficiency of energy and nutrients over a prolonged period: in children development is stunted and the individual is at risk of fatal (often clinically ‘silent’) infection and other illnesses. It is a medical and societal emergency: mortality is high, despite attempts to provide appropriate care.

When severe malnutrition affects several individuals in a society, it reflects a state in which basic needs and justice are not met. Severe malnutrition may also result from clinical disorders affecting a single person with gastrointestinal disease, poor appetite, or reduced food intake for other reasons. The World Health Organization has produced guidelines for facility-based care of patients suffering severe malnutrition, and this chapter explains the diagnosis, treatment, and management of the condition, along with its possible complications.
Disorders of galactose, pentose, and pyruvate metabolism
Authors: Cox Timothy M.
Published: February 2020

Inborn errors of galactose metabolism—galactose is principally found as free lactose in dairy products. Three inborn errors of galactose metabolism are recognized: (1) galactokinase deficiency (‘galactose diabetes’)—a very rare condition which impairs the assimilation of dietary galactose such that the free sugar and its metabolites appear in plasma and urine; (2) classical galactosaemia (galactose-1-phosphate uridylyltransferase deficiency)—the commonest (1/47 000 births) and most important disorder. High concentrations of galactose in the plasma and tissues lead to aberrant glycosylation of glycoproteins and other glycoconjugates, including lipids. The principal manifestations are a bactericidal defect associated with neonatal Escherichia coli sepsis; failure to thrive; and—in older patients—growth retardation, mental retardation, renal Fanconi’s syndrome, jaundice, and hepatosplenomegaly: without exclusion of lactose and galactose, death with cirrhosis is the rule. (3) Uridine diphosphate galactose-4´-epimerase deficiency—a rare but often harmless disorder which may be identified by neonatal screening. Rarely, cataract, sensorineural deafness and impaired psychomotor development with hepatorenal features of classical galactosaemia occur, with favourable responses to the galactose exclusion diet. Pentosuria—essential pentosuria is an asymptomatic, autosomal recessive trait affecting glucuronate metabolism, principally found in Ashkenazi Jews. Disorders of pyruvate metabolism—deficiency of the pyruvate dehydrogenase complex is the most common inherited disorder with lactic acidaemia, most often due to deficiency of the E1α subunit inherited as a dominant X-linked character. Presentation is with overwhelming neonatal acidosis; moderate lactic acidosis with progressive neurological features; or—in male children and young adults—an indolent neurological course without overt acidosis but with episodes of cerebellar ataxia induced by carbohydrate administration. Pyruvate carboxylase deficiency causes lactate/pyruvate acidosis with a necrotizing encephalopathy resembling Wernicke’s encephalopathy. Hypoglycaemia may complicate intercurrent infections and starvation.
The acute phase response and C-reactive protein
Authors: Pepys Mark B.
Published: February 2020

The acute phase response—trauma, tissue necrosis, infection, inflammation, and malignant neoplasia induce a complex series of nonspecific systemic, physiological, and metabolic responses including fever, leucocytosis, catabolism of muscle proteins, greatly increased de novo synthesis and secretion of a number of ‘acute phase’ plasma proteins, and decreased synthesis of albumin, transthyretin, and high- and low-density lipoproteins. The altered plasma protein concentration profile is called the acute phase response. Acute phase proteins—these are mostly synthesized by hepatocytes, in which transcription is controlled by cytokines including interleukin 1, interleukin 6, and tumour necrosis factor. The circulating concentrations of complement proteins and clotting factors increase by up to 50 to 100%; some of the proteinase inhibitors and α1-acid glycoprotein can increase three- to fivefold; but C-reactive protein (CRP) and serum amyloid A protein (an apolipoprotein of high-density lipoprotein particles) are unique in that their concentrations can change by more than 1000-fold. C-reactive protein—this consists of five identical, nonglycosylated, noncovalently associated polypeptide subunits. It binds to autologous and extrinsic materials which contain phosphocholine, including bacteria and their products. Ligand-bound CRP activates the classical complement pathway and triggers the inflammatory and opsonizing activities of the complement system, thereby contributing to innate host resistance to pneumococci and probably to recognition and safe ‘scavenging’ of cellular debris. Clinical features—(1) determination of CRP in serum or plasma is the most useful marker of the acute phase response in most inflammatory and tissue damaging conditions. (2) Acute phase proteins may be harmful in some circumstances. Sustained increased production of serum amyloid A protein can lead to the deposition of AA-type, reactive systemic amyloid.
Amyloidosis
Authors: Pepys Mark B. , Hawkins Philip N.
Published: February 2020

Amyloidosis is the clinical condition caused by extracellular deposition of amyloid in the tissues. Amyloid deposits are composed of amyloid fibrils, abnormal insoluble protein fibres formed by misfolding of their normally soluble precursors. About 30 different proteins can form clinically or pathologically significant amyloid fibrils in vivo as a result of either acquired or hereditary abnormalities. Small, focal, clinically silent amyloid deposits in the brain, heart, seminal vesicles, and joints are a universal accompaniment of ageing. Clinically important amyloid deposits usually accumulate progressively, disrupting the structure and function of affected tissues and lead inexorably to organ failure and death. There is no licensed treatment which can specifically clear amyloid deposits, but intervention which reduces the availability of the amyloid fibril precursor proteins can arrest amyloid accumulation and may lead to amyloid regression with clinical benefit. Pathology—amyloid fibrils bind Congo red dye producing pathognomonic green birefringence when viewed in high-intensity cross-polarized light, and the protein type can be identified by immunostaining or proteomic analysis. Amyloid deposits always contain a nonfibrillar plasma glycoprotein, serum amyloid P component, the universal presence of which is the basis for use of radioisotope-labelled serum amyloid P component as a diagnostic tracer. Clinicopathological correlation—amyloid may be deposited in any tissue of the body, including blood vessels walls and connective tissue matrix; clinical manifestations are correspondingly diverse. Identification of the amyloid fibril protein is always essential for appropriate clinical management. The specific types of amyloidosis covered in this chapter are reactive systemic (AA) amyloidosis, monoclonal immunoglobulin light chain (AL) amyloidosis, and hereditary systemic amyloidoses (including familial amyloid polyneuropathy).
Normal and abnormal sexual differentiation
Authors: Ahmed S. Faisal , Lucas-Herald Angela K.
Published: February 2020

Human sex development follows an orderly sequence of embryological events coordinated by a cascade of gene expression and hormone production in a time- and concentration-dependent manner. Underpinning the entire process of fetal sex development is the simple mantra: sex chromosomes (XX or XY) dictate the gonadotype (ovary or testis), which then dictates the somatotype (female or male phenotype). The constitutive sex in fetal development is female. Disorders of sex development (DSD) can be classified into three broad categories based on the knowledge of the karyotype: sex chromosome abnormality (e.g. X/XY, mixed gonadal dysgenesis); XX DSD (e.g. congenital adrenal hyperplasia); XY DSD (e.g. partial androgen insensitivity syndrome).
Physiological changes of normal pregnancy
Authors: Williams David J.
Published: February 2020

Almost every maternal organ system makes a physiological adaptation to pregnancy for optimal pregnancy outcome. An understanding of these adaptations brings insight into the aetiology of gestational syndromes and helps the clinician to manage pregnant women with pre-existing chronic illness. Physiological adaptations in pregnancy include: (1) cardiovascular—cardiac output increases by 30–40%; (2) respiratory—oxygen consumption increases by 20%; and (3) renal—glomerular filtration rate increases by 55%. Biochemical and endocrine changes in pregnancy include altered normal ranges for many important metabolic and endocrine laboratory tests, among other implications. Awareness of these changes is essential, both for recognition of disease in pregnancy and to prevent inappropriate pursuit of test results that are normal in pregnancy. Long-term implications of pregnancy syndromes, such as pre-eclampsia and gestational diabetes mellitus for example, can be considered exaggerated responses to pregnancy that resolve after childbirth, but herald hypertension and diabetes mellitus in later life.
Renal disease in pregnancy
Authors: Wiles Kate
Published: February 2020

Pregnancy leads to extensive and complex physiological changes in the kidney and renal system. This chapter explores the various complications that can occur in the renal system of the pregnant woman, including acute kidney injury, chronic kidney disease, and urinary tract infection. The causes of acute kidney injury in pregnancy are as those in the non-pregnant patient, but additional pregnancy-related pathologies must be considered, including pre-eclampsia and HELLP syndrome. Microangiopathic haemolytic anaemias (haemolytic uraemic syndrome and thombotic thrombocytopenic purpura) are rare but can be triggered by pregnancy or the post-partum state. Failure of the renal system to adapt to pregnancy is hypothesized to lead to the increase in adverse maternal and fetal outcomes seen in women with chronic kidney disease. Asymptomatic bacteriuria affects 2–10% of pregnant women and is associated with increased risks of symptomatic infection, preterm birth, low birth weight, and perinatal mortality. Antibiotic treatment mitigates these risks.
Radiology of the gastrointestinal tract
Authors: Moloney Fiachra , Maher Michael
Published: February 2020

The widespread introduction of endoscopic techniques has reduced the need for radiological examination of the intestinal tract and has almost completely rendered imaging of the stomach obsolete. There remains, however, a substantial role for radiological imaging in the investigation of the small and large bowel in the diagnosis of abdominal and gastrointestinal disease. The small intestine may be examined by a number of radiological techniques, including plain films, barium contrast studies, ultrasonography, CT, MRI, and nuclear medicine. Barium studies (follow-through or small-bowel enema) can provide good morphological detail of the mucosal surface of the bowel; cross-sectional imaging (usually CT or MRI) is required for disease in the wall of the bowel or outside it. CT is increasingly used as the primary investigation in suspected bowel obstruction. Nuclear medicine studies have a major role in the examination of the small bowel for the presence of inflammatory conditions, and for demonstration of potential bleeding sources. Colonoscopy has revolutionized imaging approaches to the colon because of its proven diagnostic efficacy and the added facility for biopsy of diffuse mucosal pathology and focal mucosal lesions, but is associated with a small risk of perforation. The use of barium enema continues to decline steadily. The advent of multidetector CT that allows three-dimensional reconstruction has led to a large number of new applications, including virtual colonoscopy or colonography, use of which is steadily increasing and is particularly valuable in the setting of unsuccessful or incomplete optical colonoscopy, although it is disadvantaged by inability to perform biopsy.
Structure and function of the liver, biliary tract, and pancreas
Authors: Gelson William , Gimson Alexander
Published: February 2020

The liver, sited in the right upper quadrant of the abdomen, comprises eight segments, each of which is a complete functional unit with a single portal pedicle and a hepatic vein. Within the functional segments, the structural unit is the hepatic lobule, a polyhedron surrounded by four to six portal tracts containing hepatic arterial and portal venous branches from which blood perfuses through sinusoids, surrounded by walls of hepatocytes that are a single cell thick and lined by specialized endothelial cells with ‘windows’ (fenestrae), to the centrilobular region and the central hepatic veins. Bile secreted through the canalicular membrane of the hepatocyte collects in biliary canaliculi, from which it passes through the biliary tract into the gut. The liver secretes bile, which aids digestion by emulsifying lipids, and has a central role in metabolism of (1) bilirubin, from haem; (2) bile salts, the principal mechanism for clearance of cholesterol; (3) carbohydrates; (4) amino acids and ammonia; (5) proteins, most circulating plasma proteins being produced by hepatocytes; and (6) lipid and lipoproteins. The pancreas lies in the retroperitoneum and is composed of (1) an exocrine portion centred on acini, producing an alkaline secretion containing digestive enzymes including serine proteases, exopeptidases, and lipolytic enzymes, draining through a ductal system into the duodenum; and (2) the islets of Langerhans, which secrete insulin (also glucagon, somatostatin, and pancreatic polypeptide).
Portal hypertension and variceal bleeding
Authors: Robertson Marcus , Hayes Peter
Published: February 2020

Portal hypertension refers to a pathological elevation of pressure in the veins that carry blood from the splanchnic organs to the liver which, in developed countries, most commonly results from increased intrahepatic resistance to portal flow as a result of liver cirrhosis. Portal hypertension is associated with development of many of the complications of cirrhosis and confers a poor prognosis. Acute variceal bleeding is a life-threatening medical emergency which remains a leading cause of death in patients with cirrhosis. Endoscopic variceal ligation and endoscopic variceal obturation remain the treatments of choice for bleeding oesophageal and gastric varices respectively. Advances in care including prophylactic antibiotics, vasoactive drugs, and transjugular intrahepatic portosystemic shunt in patients with bleeding refractory to early endoscopic management has improved the mortality rate, which is now estimated at 15 to 20%. Secondary prophylaxis of variceal bleeding with nonselective β-blockers and/or endoscopic variceal ligation reduces recurrent bleeding and has been demonstrated to improve survival.
Alcoholic liver disease
Authors: Forrest Ewan
Published: February 2020

The incidence of alcoholic liver disease (ALD) follows the trend of per capita alcohol consumption, with hepatic injury which extends from fatty liver to alcoholic hepatitis and cirrhosis. It is unclear how alcohol causes liver disease, but postulated mechanisms include (1) oxidative stress and acetaldehyde generated by the metabolism of ethanol, and (2) innate and adaptive immune responses. Factors determining the susceptibility to liver disease in heavy drinkers are believed to include a variety of host and environmental factors, with genetic factors increasingly recognized. Clinical manifestations are extremely variable, and some patients remain relatively well while others suffer the effects of severe hepatic failure. Although patients can come to light with a life-threatening complication, most often they develop symptoms which are not immediately related to the liver, such as nonspecific digestive symptoms or psychiatric complaints. The key to the early recognition of alcohol-related disease is having a high index of suspicion, with confirmation by (1) direct questioning for alcohol history and alcohol-related symptoms; (2) clinical examination for signs of chronic liver disease; (3) supportive investigations, including aspartate aminotransferase, which is less than 500 IU/litre and greater than the alanine aminotransferase level; and (4) liver biopsy, which may be required in some cases of diagnostic uncertainty and to confirm the stage of the disease, revealing alcoholic fatty liver, alcoholic hepatitis, or cirrhosis. Management is governed by the stage and severity of the liver disease, but always includes abstinence and adequate nutritional support. In selected patients with severe acute alcoholic hepatitis, corticosteroids can reduce short-term mortality. Transplantation remains the only effective treatment for advanced alcoholic cirrhosis, although this remains controversial, mainly because of concerns about post-transplant recidivism.
The liver in systemic disease
Authors: Neuberger James
Published: February 2020

The liver is affected in many systemic diseases, with important examples being cardiovascular diseases—raised venous pressure can lead to hepatic congestion. Hepatomegaly is frequent in moderately severe heart failure. Cardiac cirrhosis is a rare complication. Pulmonary diseases—conditions that involve the liver as well as the lungs include cystic fibrosis, sarcoidosis, and α1-antitrypsin deficiency. Gastrointestinal diseases—inflammatory bowel disease is associated with a range of hepatic pathology including fatty change, pericholangitis, sclerosing cholangitis, autoimmune hepatitis, cirrhosis, and (rarely) amyloidosis. Hepatobiliary disease associated with total parenteral nutrition varies from a mild, asymptomatic disease to jaundice, cirrhosis, and liver failure. Coeliac disease may rarely present with abnormal liver tests. Obesity, especially in association with the metabolic syndrome, may be associated with nonalcoholic hepatitis and steatohepatitis. Endocrine diseases—autoimmune hepatitis and primary biliary cholangitis may be associated with autoimmune endocrine disorders. Both hypothyroidism and hyperthyroidism can cause abnormalities of liver function, which are usually mild. Haematological diseases—conditions associated with abnormal blood clotting, such as protein C or S deficiency and paroxysmal nocturnal haemoglobinuria, may lead to Budd–Chiari syndrome (hepatic vein thrombosis). The liver may be involved in both non-Hodgkin’s lymphoma and leukaemia. Infectious diseases—agents that particularly affect the liver (e.g. viral hepatitis) are discussed elsewhere although many systemic infections also infect the liver. Abnormal liver function may occur during many systemic infections, but it is rare for patients with sepsis to present primarily with liver symptoms, although jaundice, abnormal liver function tests, or (very rarely) fulminant hepatic failure may be the principal presenting feature. Rheumatological diseases—hepatic disease may either be a consequence of treatment or occur in association with other autoimmune diseases.
Chronic heart failure: Definitions, investigation, and management
Authors: Cleland John G.F. , Clark Andrew L.
Published: February 2020

Heart failure is a common clinical syndrome, predominantly a disease of older people, often presenting with breathlessness, fatigue, and peripheral oedema. Its pathophysiology is complex, with a common feature being salt and water retention, possibly triggered by a relative fall in renal perfusion pressure. Common aetiologies include ischaemic heart disease, hypertension, and valvular heart disease. New treatments have improved prognosis substantially over the past two decades. Early diagnosis relies on a low threshold of suspicion and screening of people at risk. Treatable causes for heart failure should be identified and corrected. Pharmacological therapy is given to improve symptoms and prognosis. Diuretic therapy is the mainstay for control of congestion and symptoms, but its effect on long-term prognosis is unknown. For patients with HFrEF, either angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or angiotensin receptor–neprilysin inhibitors, combined with β-blockers and mineralocorticoid receptor antagonists (triple therapy) provide both symptomatic and prognostic benefit.
Coronary heart disease: Epidemiology and prevention
Authors: Danaei Goodarz , Rahimi Kazem
Published: February 2020

Coronary heart disease (CHD) is now the leading cause of death and disability globally. Despite recent declines in age-adjusted death rates from CHD, the number of CHD deaths have been increasing due to a combination of growth in population numbers and their longevity. In addition, manifestation and outcome of CHD varies substantially between and within countries. Unlike many other common medical conditions that disable and kill and remain unpreventable, CHD is to a large extent preventable. There are strong, unconfounded relationships between several risk factors and CHD mortality and non-fatal myocardial infarction. The most important risk factors for CHD are smoking, high blood pressure, dyslipidaemia, diabetes, physical inactivity, unhealthy diet, and obesity. Controlling these risk factors, even in middle-aged individuals, through lifestyle changes, medical treatment, or public health interventions, may reduce CHD incidence by almost one-half.
Cholesterol embolism
Authors: Dudley Christopher
Published: February 2020

Cholesterol embolism occurring after vascular surgery or intra-arterial angiographic procedures is not uncommon, but is often unrecognized. The clinical features mimic several conditions, including contrast nephropathy and systemic vasculitis, and—if misdiagnosed—can result in the inappropriate use of powerful immunosuppressive drugs. A high index of suspicion is required when an elderly patient with widespread vascular disease develops a non-specific systemic illness with progressive renal impairment, particularly after vascular surgery or arteriography. Biopsy of affected tissue, especially skin or kidney, is diagnostic—showing biconvex, needle-shaped cholesterol clefts within the lumen of arteries or arterioles. Treatment is supportive and the prognosis is often poor.
Cardiac arrest
Authors: Perkins Gavin D. , Soar Jasmeet , Nolan Jerry P. , Gabbott David A.
Published: February 2020

Cardiovascular disease is the most common cause of sudden cardiac arrest, which causes over 60% of adult coronary heart disease deaths. Most cardiac arrests are preventable. Survival depends on early recognition and prompt initiation of chest compressions and ventilations (cardiopulmonary resuscitation), and early defibrillation if appropriate. High-quality cardiopulmonary resuscitation is defined by compressions to a depth of 5–6 cm, at a rate of 100–120 per minute, full release of pressure between compressions and minimal interruptions to chest compression. Drugs have a limited role in treating cardiac arrest. If initial resuscitation is successful the quality of post-resuscitation care determines the patient’s final outcome. Use emergency care treatment plans to record in advance, recommendations for emergency treatments, including CPR.
Sedation and analgesia in the ICU
Authors: Reade Michael C.
Published: February 2020

Patients undergoing mechanical ventilation or other forms of invasive organ support in an intensive care unit should ideally be free of pain, anxiety, and delirium, sufficiently cooperative or sedated to enable safe delivery of essential aspects of their care; sufficiently awake such that tracheal extubation is not unnecessarily delayed; and left with few or no unpleasant memories of their illness and treatment. This ideal is often not achieved. Management should be based on an analgesia-first, delirium-control, sedation-minimization approach. Identifying intensive care unit-associated delirium is not straightforward: most delirious intensive care patients are not agitated, and ‘hypoactive’ delirium can mask substantial psychological distress. Various assessment scales can be used to quantitate, monitor, and communicate sedation and sedation goals, and similar tools can be employed to identify delirium.
Palliative and end-of-life care in the ICU
Authors: Levin Phillip D. , Sprung Charles L.
Published: February 2020

What happens when organ support leads to prolongation of life, but with no hope of ultimate survival, or survival with unacceptable quality of life? For many—but not all—patients, families, and physicians, prolongation of life with little or no hope of a good quality of life is considered worse than death. This chapter looks at the cultural milieu in determining the responses and needs of all parties in regard to end-of-life care. Excellent communication is required to prevent potential conflicts and provide both the medical team and the patient/family with peace of mind. The decision to institute palliative or end-of-life care should, if at all possible, always be reached via a negotiating process between the medical staff and the patient or their family. The best protection against conflict comes from a good bedside manner reflecting patience with the family, honesty, and some optimism.
The upper respiratory tract
Authors: Shah Pallav L. , Stradling J.R. , Craig S.E.
Published: February 2020

The upper respiratory tract extends from the anterior nares to the larynx and comprises (1) the nose—with the main function as first-line defence against problems with incoming air, acting as a coarse particle filter and a conditioner (temperature and humidity) of the air, and with the sense of smell helping to detect noxious substances that are best avoided. (2) The pharynx—this has to act as a rigid tube when used for breathing, but during swallowing it has to be a collapsible tube capable of peristalsis, a combination of functions which is achieved by complex innervation and musculature. Subepithelial collections of lymphoid tissue in the pharynx are ideally suited to process inhaled and swallowed antigens. (3) The larynx—this has three important functions: communication, protection of the airway, and dynamic control of lung volume.
Airways and alveoli
Authors: Wagner Peter D. , Shah Pallav L.
Published: February 2020

The lung is the organ of gas exchange, providing the means of transferring oxygen (O2) from the air to the blood by passive diffusion for subsequent distribution to the tissues, and of similarly removing metabolically produced carbon dioxide (CO2) from the blood, which is then exhaled to the atmosphere. The lungs are enclosed within the thoracic cavity. Inspiration is driven by contraction of the intercostal muscles and the diaphragm, which expands the ribcage in both anteroposterior and lateral dimensions, such that the pressure inside the thoracic cavity but external to the lungs is reduced to below that of the air, which is thereby drawn in. Lung diseases of many types commonly affect each of the steps involved in gas exchange, and the clinical consequences can usually be readily understood if the structure–function relationships are known.
The clinical presentation of respiratory disease
Authors: Kemp Samuel , Hopkin Julian
Published: February 2020

Respiratory disease can present in many ways, with variations attributable to many factors. The clinical presentation directs diagnostic hypothesis making, the choice of diagnostically discriminating investigations, and the most appropriate management. If a detailed history is not taken, the patient not observed carefully and examined diligently, and the information from these sources is not analysed correctly, then inappropriate investigation and management is likely. Common symptoms of respiratory disease are breathlessness, cough, haemoptysis, and pleuritic chest pain, details of which can point to particular diagnoses. An account of environmental exposures at work and home, and of family history, is critically important in some cases. In chronic respiratory disease, where breathlessness and disability are to be assessed, walking with the patient and observing exercise tolerance and distress (and pulse oximetry) can provide valuable information.
Upper airway obstruction
Authors: Hull James H. , Hind Matthew
Published: February 2020

The upper airway is anatomically defined by the carina inferiorly and pharynx superiorly, with pathology predominately arising from the trachea and larynx. Obstruction of the upper airway may arise because of a fixed structural pathology such as tracheal stenosis or malignancy, but can arise following loss of normal function (e.g. inappropriate vocal cord adduction). A high index of suspicion is required to make the diagnosis because the clinical features of upper airway obstruction can mimic other respiratory conditions. Calculation of the ratio of forced expiratory volume in one second to peak expiratory flow (Empey index) may identify patients with unsuspected upper airway obstruction.

Acute upper airway obstruction is a medical emergency and usually caused by aspiration, oedema (allergic, hereditary, and acquired angio-oedema, smoke inhalation), or infection (croup, epiglottitis, quinsy, retropharyngeal abscess). Non-acute causes of upper airway obstruction include malignancy, tracheal stenosis, tracheal compression, dynamic large airway collapse, and laryngeal dysfunction.