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Pathology (from Greek pathos, feeling, pain, suffering; and logos, study of; see also -ology) is the study of the processes underlying disease and other forms of illness, harmful abnormality, or dysfunction. Within biology but also a branch of medicine, it means specifically the study and diagnosis of the structural and functional changes in molecules, cells, tissues and organs that underlie disease. Pathology as a field of knowledge hence forms the basis of the scientific reasoning behind the practice of medicine.
Scope of pathology
The primary goal of pathology is the study of the four main aspects of a disease:
- Etiology: what causes the disease
- Pathogenesis: the mechanism by which a certain etiological factor causes disease
- Morphologic changes: the structural changes induced in the cells, tissues and organs
- Clinical significance: the functional consequences of the morphologic changes
Because the public rarely meets pathologists, their work is not well understood. Pathology is a large and diverse field that allows a pathologist to participate in multiple areas of the field or focus their scope to a specific area. Essential to everyday surgeries, pathologists are responsible for processing and reporting on all specimens generated during surgery. Tissue samples are taken from the submitted specimens, stained, and processed for microscopic evaluation. Microscopic examination searches for disease of any type and this information is returned to the surgeon via a pathology report. They, along with Pathologists' Assistants and Medical Technologists, process specimens at medical laboratories for interpretations. In other words, when a doctor refers to a "laboratory result", they are not referring to a number generated by a black box; instead, it is the interpretation of a value by a pathologist or a technologist. It is also important to understand that a different laboratory might produce a different value on the same specimen. Pathologists are also called upon to perform autopsies; they are usually assisted by Dieners. Autopsies represent less than 5% of the workload of a typical modern pathologist. There exists a subspecialty in pathology that allows for the training of medical examiners who wish to pursue forensics.
Pathologists usually do not see patients, but do on occasion such as when performing bone marrow biopsies and aspirates or fine needle aspirations of superficial nodules. Thus, it is best considered a form of diagnostic medicine. In addition to the diagnosis of disease, including cancer, and the administration of medical laboratories, pathologists often participate in the teaching of medical students (pathology is a core course in the medical curriculum). Pathologists express their opinion as a pathology report addressed to the doctor requesting it. Since pathologists most often communicate with other doctors, they are sometimes nicknamed "the doctor's doctor." Pathology is often considered the most scientific branch of medicine because of the available avenues of research involving human material. Finally, the circulation of laboratory data is a central issue in medical informatics and the current tendency towards electronic medical records.
Tools of pathology
The techniques used most often in the study of the disease process and hence diagnosis are:
- Gross pathology: the recognition of disease based on macroscopic examination of surgical specimens generated at the time of surgery or at autopsy.
- Histology: the microscopic study of tissues. Histopathology is the science of diagnosing diseases on the basis of the histological aspect of the diseased tissues.
- Cytology: the study of detached cells. Cytopathology is the science of diagnosing diseases on the basis of the cytological aspects of detached cells.The most common application of this technique is the Pap smear.
- Clinical chemistry: the gathering, detection, and reporting of an incredible array of chemical measures found by the analysis of collected body samples.
- Immunology: the use of specific immune markers and antibodies to aid in the diagnosis of disease.
- Flow cytometry: analysis of a process that allows for the identification of specific cells.
- Molecular Biology techniques, like PCR and FISH are increasingly useful to diagnose diseases, especially microbiological and cancer diagnoses.
Branches of pathology
In the United States, pathologists are medical doctors (MD) or doctors of osteopathic medicine (DO), that have completed a four year undergraduate program, four years of medical school training, and four to five years of postgraduate training in the form of a pathology residency. Training may be within two primary specialties, as recognized by the American Board of Pathology:
- Anatomic Pathology, the science of diagnosing diseases based on the appearance of tissues, both gross and microscopic.
- Clinical Pathology, the science of diagnosing diseases based on the analysis of body fluids like blood, urine, etc.
Most pathologists seek a broad based training in both fields and thus require four years of postgraduate training known as residency. Board certification examination is required. Boarding requirements are set by the American Board of Pathology. Following the general training, many pathologists continue on to more specialized training within specific fields of pathology. This speciality training is termed a fellowship. Multiple fellowship opportunities are available within both Anatomical and Clinical Pathology. Examples of fellowhips include General Surgical Pathology, Gastrointestinal Pathology, Genitourinary pathology, Hematopathology, Dermatopathology, Microbiology, and Clinical Chemistry. These are but a few of the numerous fields within pathology. Some of the speciality areas of pathology are board certified while others are not. Pathologists, like all other medical doctors, require a medical license from the State they are working in to practice their field. This entails meeting continuing medical education requirements to maintain licensure.
Most of the work of investigative pathologists is carried out in the laboratory. Tissue culture, polymerase chain reaction (PCR), ELISA, western blot, southern blot, northern blot and many other biotechnological methods are required to identify differences between normal and disease states in different cell types with regards to DNA, RNA, and protein as well as determining the influence of these differences on the organism as a whole.
- Speech pathology is an unrelated area mostly involved in helping patients with stroke or speech impediments.
- Psychopathology is also used in mental health, denoting the study of mental illness.
- Anatomy, either gross or microscopic (histology)
- Nosology: the science of classifying, or naming, diseases
- Epidemiology: the science of associating diseases with risk factors, regardless of known pathological relationships. An epidemiological association is often the first step in establishing an etiological (causal) relationship between a risk factor and a disease.
Other uses of "pathology"
Pathological is used to describe a person's actions in such a way as to credit the action to a disease process, e.g. pathological purchasing or pathological consumption, pathological narcissism, pathological liar, pathological gambling, pathological jealousy. Pathological is also used casually, to signify an abnormal state, e.g. a "pathological attitude" or a "pathological woman hater".
Pathological is also used in mathematics, physics, and statistics to describe an exceptionally (or awkwardly, or inconveniently) atypical example or set of data, often one which does not abide by rules or succumb to treatment that other similar cases usually do:
- Pathological (mathematics)
- Pathological science
- Immunohistochemistry protocols and troubleshooting
- United States and Canadian Academy of Pathology
- Pathology notes for Med students
- Pathology Service Associates, LLC
- College of American Pathologists
- Royal College of Pathologists (UK)
- Pathological Society
Advance practice nursing - Audiology - Dentistry - Dietetics - Emergency medical services - Epidemiology - Medical technology - Midwifery - Nursing - Occupational therapy - Optometry - Osteopathic medicine - Pharmacy - Physical therapy (Physiotherapy) - Physician - Physician assistant - Podiatry - Psychology - Public health - Respiratory therapy - Speech and language pathology
Physician specialties: Anesthesiology - Dermatology - Emergency medicine - General practice (Family medicine) - Internal medicine - Neurology - Nuclear medicine - Occupational medicine - Pathology - Pediatrics - Physical medicine and rehabilitation (Physiatry) - Preventive medicine - Psychiatry - Radiation oncology - Radiology - Surgery
Medical subspecialties: Allergy and immunology - Cardiology - Endocrinology - Gastroenterology - Hematology - Infectious disease - Intensive care medicine (Critical care medicine) - Medical genetics - Nephrology - Oncology - Pulmonology - Rheumatology
Major subfields of biology
Anatomy - Astrobiology - Biochemistry - Bioinformatics - Botany - Cell biology - Ecology - Developmental biology - Evolutionary biology - Genetics - Genomics - Marine biology - Human biology - Microbiology - Molecular biology - Origin of life - Paleontology - Parasitology - Pathology - Physiology - Taxonomy - Zoology
Pathology: Tumors, neoplasia, and oncology (C00-D48, 140-239)
Hyperplasia - Cyst - Pseudocyst - Hamartoma - Benign neoplasm
Anus - Bladder - Blood - Bile duct - Bone - Brain - Breast - Cervix - Colon/rectum - Endometrium - Esophagus - Eye - Gallbladder - Head/Neck - Liver - Kidney - Larynx - Lung - Mediastinum (chest) - Mouth - Ovaries - Pancreas - Penis - Prostate - Skin - Small intestine - Stomach - Tailbone - Testicles - Thyroid
Pathology: hematology (primarily C81-C96/200-208, D45-D47, D50-D77/280-289)
nutritional anemia: Iron deficiency anemia, Plummer-Vinson syndrome, Megaloblastic anemia (Pernicious anemia)
coagulopathy: DIC • Hemophilia (A, B, C, XIII) • Von Willebrand disease
WHO-I Langerhans cell histiocytosis - non-Langerhans-cell histiocytosis/WHO-II (Juvenile xanthogranuloma, Hemophagocytic lymphohistiocytosis) - malignant histiocytic disorders/WHO-III (Acute monocytic leukemia, Malignant histiocytosis, Erdheim-Chester disease)
Asplenia/hyposplenism - Methemoglobinemia
Endocrine pathology of psychological interest (E00-35)
thyroid Hypothyroidism (Iodine deficiency, Cretinism, Congenital hypothyroidism, Goitre) - Hyperthyroidism (Graves-Basedow disease, Toxic multinodular goitre) - Thyroiditis (De Quervain's thyroiditis, Hashimoto's thyroiditis)
Nutritional pathology (E40-68, 260-269)
Obesity - Hypervitaminosis A - Hypervitaminosis D
amino-acids Phenylketonuria - Alkaptonuria - Ochronosis - Tyrosinemia - Maple syrup urine disease - Propionic acidemia - Methylmalonic acidemia - Isovaleric acidemia - Primary carnitine deficiency - Cystinuria - Cystinosis - Hartnup disease - Homocystinuria - Citrullinemia - Hyperammonemia - Glutaric acidemia type 1
carbohydrates Lactose intolerance - Glycogen storage disease (type I, type II, type III, type IV, type V), Fructose intolerance, Galactosemia
Lipid storage disorders Gangliosidosis - GM2 gangliosidoses (Sandhoff disease, Tay-Sachs disease) - GM1 gangliosidoses - Mucolipidosis type IV - Gaucher's disease - Niemann-Pick disease - Farber disease - Fabry's disease - Metachromatic leukodystrophy - Krabbe disease - Neuronal ceroid lipofuscinosis - Batten disease - Cerebrotendineous xanthomatosis - Wolman disease - Cholesteryl ester storage disease
List of fatty acid metabolism disorders - Hyperlipidemia - Hypercholesterolemia - Familial hypercholesterolemia - Xanthoma - Combined hyperlipidemia - Lecithin cholesterol acyltransferase deficiency - Tangier disease - Abetalipoproteinemia
mineral metabolism Disorders of calcium metabolism - Hypophosphatemia - Hypophosphatasia - Wilson's disease - Menkes disease - Hypermagnesemia - Hypomagnesemia - Hypercalcaemia - Hypocalcaemia
fluid, electrolyte and acid-base balance Electrolyte disturbance - Hypernatremia - Hyponatremia - Respiratory acidosis - Metabolic acidosis - Lactic acidosis - Hypervolemia - Hypokalemia - Hyperkalemia - Mixed disorder of acid-base balance - Hyperchloremia - Hypochloremia - Dehydration
porphyrin and bilirubin Acatalasia - Gilbert's syndrome - Crigler-Najjar syndrome - Dubin-Johnson syndrome - Rotor syndrome - Porphyria (Acute intermittent porphyria, Gunther's disease, Porphyria cutanea tarda, Erythropoietic protoporphyria, Hepatoerythropoietic porphyria, Hereditary coproporphyria, Variegate porphyria)
glycosaminoglycan Mucopolysaccharidosis - Hurler syndrome - Hunter syndrome - Sanfilippo syndrome - Morquio syndrome
glycoprotein I-cell disease - Pseudo-Hurler polydystrophy - Aspartylglucosaminuria - Fucosidosis - Alpha-mannosidosis - Sialidosis
other Alpha 1-antitrypsin deficiency - Cystic fibrosis - Familial Mediterranean fever - Lesch-Nyhan syndrome
Eye disease - pathology of the eye (H00-H59, 360-379)
lacrimal system: Dacryoadenitis - Epiphora - Dacryocystitis
orbit: Exophthalmos - Enophthalmos
|Optic nerve and visual pathways||
Optic neuritis - Papilledema - Optic atrophy - Leber's hereditary optic neuropathy - Dominant optic atrophy - Optic disc drusen - Glaucoma - Toxic and nutritional optic neuropathy - Anterior ischemic optic neuropathy
accommodation and refraction
Paralytic strabismus: Ophthalmoparesis - Progressive external ophthalmoplegia - Palsy (III, IV, VI) - Kearns-Sayre syndrome
Other strabismus: Esotropia/Exotropia - Hypertropia - Heterophoria (Esophoria, Exophoria) - Brown's syndrome - Duane syndrome
|Visual disturbances and blindness||
Amblyopia - Leber's congenital amaurosis - Subjective (Asthenopia, Hemeralopia, Photophobia, Scintillating scotoma) - Diplopia - Scotoma - Anopsia (Binasal hemianopsia, Bitemporal hemianopsia, Homonymous hemianopsia, Quadrantanopia) - Color blindness (Achromatopsia, Dichromacy, Monochromacy) - Nyctalopia (Oguchi disease) - Blindness/Low vision
Trachoma - Onchocerciasis
See also congenital
Pathology of respiratory system (J, 460-519)
|Acute upper respiratory infections|
|Influenza and Pneumonia|
|Other acute lower respiratory infections|
|Other diseases of upper respiratory tract||
Vasomotor rhinitis · Hay fever · Atrophic rhinitis · Nasal polyp · Deviated septum · Adenoid hypertrophy · Peritonsillar abscess · Vocal fold nodule · Laryngospasm
|Chronic lower respiratory diseases||
Emphysema · COPD · Asthma · Status asthmaticus · Bronchiectasis
|Lung diseases due to external agents||
Pneumoconiosis (Coalworker's pneumoconiosis, Asbestosis, Silicosis, Bauxite fibrosis, Berylliosis, Siderosis) · Byssinosis · Hypersensitivity pneumonitis (Farmer's lung, Bird fancier's lung)
|Other, principally affecting
Acute respiratory distress syndrome · Pulmonary edema · Hamman-Rich syndrome · Interstitial lung disease
|Suppurative and necrotic conditions
of lower respiratory tract
Lung abscess · Pleural effusion · Empyema
Pneumothorax · Hemothorax · Hemopneumothorax · Mendelson's syndrome · Respiratory failure · Atelectasis · Mediastinal emphysema · Mediastinitis
see also congenital (Q30-Q34, 748)
Oral Pathology: Oral pathology (K00-K14, 520-529)
Anodontia/Hypodontia - Hyperdontia - abnormalities of size and form of teeth (Concrescence, Fusion, Gemination, Dens evaginatus/Talon cusp, Dens invaginatus, Enamel pearl, Macrodontia, Microdontia, Taurodontism) - disturbances in tooth formation (Dilaceration, Regional odontodysplasia, Turner's hypoplasia) - other hereditary disturbances in tooth structure (Amelogenesis imperfecta, Dentinogenesis imperfecta, Dentin dysplasia)
|Hard, Soft and Periapical Tissues|
Malocclusion - Micrognathism - Prognathism - Retrognathism - Temporomandibular joint disorder
Odontogenic keratocyst - Torus mandibularis - Torus palatinus - Cherubism - Ameloblastoma
|Lip and Oral mucosa||
Angular cheilitis - Erythroplakia - Hairy leukoplakia - Leukoplakia
Urinary system - Pathology - Nephrology (N00-N39, 580-599)
|Diseases of the glomerulus||
Glomerulonephritis - Focal segmental glomerulosclerosis - Membranoproliferative glomerulonephritis - Membranous glomerulonephritis - Nephritic syndrome - Post-streptococcal glomerulonephritis - Nephrotic syndrome (Minimal change disease) - IgA nephropathy - Lupus nephritis - Diabetic nephropathy - Rapidly progressive glomerulonephritis
|Tubulointerstitial diseases of the kidney||
Interstitial nephritis - Pyelonephritis - Hydronephrosis - Pyonephrosis - Balkan nephropathy - Reflux nephropathy
Acute renal failure (Acute tubular necrosis) - Chronic renal failure
|Diseases of the renal tubule and
other disorders of kidney and ureter
Renal osteodystrophy - Nephrogenic diabetes insipidus - Renal tubular acidosis - Nephroptosis - Ureterocele
|Other diseases and
disorders of urinary system
|Tumors of the kidney||
Renal cell carcinoma - Wilms' tumor (children)
See also congenital conditions (Q60-Q64, 753)