Diabetes insipidus (DI), alternately called arginine vasopressin deficiency (AVP-D) or arginine vasopressin resistance (AVP-R), is a condition characterized by large amounts of dilute urine and increased thirst. The amount of urine produced can be nearly 20 liters per day. Reduction of fluid has little effect on the concentration of the urine. Complications may include dehydration or seizures.
The urinary system, also known as the urinary tract or renal system, consists of the kidneys, ureters, bladder, and the urethra. The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, control levels of electrolytes and metabolites, and regulate blood pH. The urinary tract is the body's drainage system for the eventual removal of urine. The kidneys have an extensive blood supply via the renal arteries which leave the kidneys via the renal vein. Each kidney consists of functional units called nephrons. Following filtration of blood and further processing, wastes exit the kidney via the ureters, tubes made of smooth muscle fibres that propel urine towards the urinary bladder, where it is stored and subsequently expelled from the body by urination. The female and male urinary system are very similar, differing only in the length of the urethra.
Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then travels down the axon terminating in the posterior pituitary, and is released from vesicles into the circulation in response to extracellular fluid hypertonicity (hyperosmolality). AVP has two primary functions. First, it increases the amount of solute-free water reabsorbed back into the circulation from the filtrate in the kidney tubules of the nephrons. Second, AVP constricts arterioles, which increases peripheral vascular resistance and raises arterial blood pressure.
Polyuria is excessive or an abnormally large production or passage of urine. Increased production and passage of urine may also be termed as diuresis. Polyuria often appears in conjunction with polydipsia, though it is possible to have one without the other, and the latter may be a cause or an effect. Primary polydipsia may lead to polyuria. Polyuria is usually viewed as a symptom or sign of another disorder, but it can be classed as a disorder, at least when its underlying causes are not clear.
Diuresis is the excretion of urine, especially when excessive (polyuria). The term collectively denotes the physiologic processes underpinning increased urine production by the kidneys during maintenance of fluid balance.
Polydipsia is excessive thirst or excess drinking. The word derives from the Greek πολυδίψιος (poludípsios) "very thirsty", which is derived from πολύς + δίψα. Polydipsia is a nonspecific symptom in various medical disorders. It also occurs as an abnormal behaviour in some non-human animals, such as in birds.
Desmopressin, sold under the trade name DDAVP among others, is a medication used to treat diabetes insipidus, bedwetting, hemophilia A, von Willebrand disease, and high blood urea levels. In hemophilia A and von Willebrand disease, it should only be used for mild to moderate cases. It may be given in the nose, by injection into a vein, by mouth, or under the tongue.
Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the blood. Early symptoms may include a strong feeling of thirst, weakness, nausea, and loss of appetite. Severe symptoms include confusion, muscle twitching, and bleeding in or around the brain. Normal serum sodium levels are 135–145 mmol/L. Hypernatremia is generally defined as a serum sodium level of more than 145 mmol/L. Severe symptoms typically only occur when levels are above 160 mmol/L.
The syndrome of inappropriate antidiuretic hormone secretion (SIADH), also known as the syndrome of inappropriate antidiuresis (SIAD), is characterized by a physiologically inappropriate release of antidiuretic hormone (ADH) either from the posterior pituitary gland, or an abnormal non-pituitary source. Unsuppressed ADH causes a physiologically inappropriate increase in solute-free water being reabsorbed by the tubules of the kidney to the venous circulation leading to hypotonic hyponatremia.
Demeclocycline is a tetracycline antibiotic which was derived from a mutant strain of Streptomyces aureofaciens.
Nocturia is defined by the International Continence Society (ICS) as “the complaint that the individual has to wake at night one or more times for voiding .” The term is derived from Latin nox, night, and Greek [τα] ούρα, urine. Causes are varied and can be difficult to discern. Although not every patient needs treatment, most people seek treatment for severe nocturia, waking up to void more than 2–3 times per night.
Primary polydipsia and psychogenic polydipsia are forms of polydipsia characterised by excessive fluid intake in the absence of physiological stimuli to drink. Psychogenic polydipsia which is caused by psychiatric disorders, often schizophrenia, is often accompanied by the sensation of dry mouth. Some forms of polydipsia are explicitly non-psychogenic. Primary polydipsia is a diagnosis of exclusion.
Vasopressin receptor 2 (V2R), or arginine vasopressin receptor 2, is a protein that acts as receptor for vasopressin. AVPR2 belongs to the subfamily of G-protein-coupled receptors. Its activity is mediated by the Gs type of G proteins, which stimulate adenylate cyclase.
The actions of vasopressin are mediated by stimulation of tissue-specific G protein-coupled receptors (GPCRs) called vasopressin receptors that are classified into the V1 (V1A), V2, and V3 (V1B) receptor subtypes. These three subtypes differ in localization, function and signal transduction mechanisms.
Aquaporin-2 (AQP-2) is found in the apical cell membranes of the kidney's collecting duct principal cells and in intracellular vesicles located throughout the cell. It is encoded by the AQP2 gene.
A fluid or water deprivation test is a medical test which can be used to determine whether the patient has diabetes insipidus as opposed to other causes of polydipsia. The patient is required, for a prolonged period, to forgo intake of water completely, to determine the cause of the thirst.
Specific gravity, in the context of clinical pathology, is a urinalysis parameter commonly used in the evaluation of kidney function and can aid in the diagnosis of various renal diseases.
Nephrocalcinosis, once known as Albright's calcinosis after Fuller Albright, is a term originally used to describe the deposition of poorly soluble calcium salts in the renal parenchyma due to hyperparathyroidism. The term nephrocalcinosis is used to describe the deposition of both calcium oxalate and calcium phosphate. It may cause acute kidney injury. It is now more commonly used to describe diffuse, fine, renal parenchymal calcification in radiology. It is caused by multiple different conditions and is determined by progressive kidney dysfunction. These outlines eventually come together to form a dense mass. During its early stages, nephrocalcinosis is visible on x-ray, and appears as a fine granular mottling over the renal outlines. It is most commonly seen as an incidental finding with medullary sponge kidney on an abdominal x-ray. It may be severe enough to cause renal tubular acidosis or even end stage kidney disease, due to disruption of the kidney tissue by the deposited calcium salts.
Central diabetes insipidus, recently renamed arginine vasopressin deficiency (AVP-D), is a form of diabetes insipidus that is due to a lack of vasopressin (ADH) production in the brain. Vasopressin acts to increase the volume of blood (intravascularly), and decrease the volume of urine produced. Therefore, a lack of it causes increased urine production and volume depletion.
Adipsia, also known as hypodipsia, is a symptom of inappropriately decreased or absent feelings of thirst. It involves an increased osmolality or concentration of solute in the urine, which stimulates secretion of antidiuretic hormone (ADH) from the hypothalamus to the kidneys. This causes the person to retain water and ultimately become unable to feel thirst. Due to its rarity, the disorder has not been the subject of many research studies.
