question: If alcohol dehydrates you, why does it make urine clear?
comment: It dehydrates you by *forcing* you to urinate, so your body is pushing out more fluid than it usually would which is why the urine is clear.
passages: Any deterioration in liver function reduces its ability to process the recirculated urobilinogen. The excess that remains in the blood is filtered out by the kidneys and appears in urine. When hemolytic disorders occur the amount of unconjugated bilirubin that is present in the blood increases causing an increase in hepatic excretion of conjugated bilirubin, resulting in increased amounts of urobilinogen that in turn causes an increase in reabsorption, recirculation and renal excretion.
   Section::::Formation of urine.:Reabsorption.
  
  Tubular reabsorption is the process by which solutes and water are removed from the tubular fluid and transported into the blood. It is called "reabsorption" (and not "absorption") both because these substances have already been absorbed once (particularly in the intestines) and because the body is reclaiming them from a postglomerular fluid stream that is well on its way to becoming urine (that is, they will soon be lost to the urine unless they are reclaimed).
   In renal physiology, reabsorption or tubular reabsorption is the process by which the nephron removes water and solutes from the tubular fluid (pre-urine) and returns them to the circulating blood. It is called "reabsorption" (and not "absorption") both because these substances have already been absorbed once (particularly in the intestines) and because the body is reclaiming them from a postglomerular fluid stream that is well on its way to becoming urine (that is, they will soon be lost to the urine unless they are reclaimed). Substances are reabsorbed from the tubule into the peritubular capillaries. This happens as a result of sodium transport from the lumen into the blood by the Na/KATPase in the basolateral membrane of the epithelial cells. Thus, the glomerular filtrate becomes more concentrated, which is one of the steps in forming urine. Reabsorption allows many useful solutes (primarily glucose and amino acids), salts and water that have passed through Bowman's capsule, to return to the circulation. These solutes are reabsorbed isotonically, in that the osmotic potential of the fluid leaving the proximal convoluted tubule is the same as that of the initial glomerular filtrate. However, glucose, amino acids, inorganic phosphate, and some other solutes are reabsorbed via secondary active transport through cotransport channels driven by the sodium gradient.
   The color and volume of urine can be reliable indicators of hydration level. Clear and copious urine is generally a sign of adequate hydration. Dark urine is a sign of dehydration. The exception occurs when diuretics are consumed, in which case urine can be clear and copious and the person still be dehydrated.
  
  Section::::Uses.
  
  Section::::Uses.:Source of medications.
   Albumin (when ionized in water at pH 7.4, as found in the body) is negatively charged. The glomerular basement membrane is also negatively charged in the body; some studies suggest that this prevents the filtration of albumin in the urine. According to this theory, that charge plays a major role in the selective exclusion of albumin from the glomerular filtrate. A defect in this property results in nephrotic syndrome leading to albumin loss in the urine. Nephrotic syndrome patients are sometimes given albumin to replace the lost albumin.
  
  Section::::Structure.
   Urea is usually excreted as a waste product from the kidneys. However, when plasma blood volume is low and ADH is released the aquaporins that are opened are also permeable to urea. This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water. Urea can then re-enter the nephron and be excreted or recycled again depending on whether ADH is still present or not.
   Osmolality of blood increases with dehydration and decreases with overhydration. In normal people, increased osmolality in the blood will stimulate secretion of antidiuretic hormone (ADH). This will result in increased water reabsorption, more concentrated urine, and less concentrated blood plasma. A low serum osmolality will suppress the release of ADH, resulting in decreased water reabsorption and more concentrated plasma.
   Urine varies in appearance, depending principally upon a body's level of hydration, as well as other factors. Normal urine is a transparent solution ranging from colorless to amber but is usually a pale yellow. In the urine of a healthy individual the color comes primarily from the presence of urobilin. Urobilin is a final waste product resulting from the breakdown of heme from hemoglobin during the destruction of aging blood cells.
   Diabetic cataract formation follows an increase in sugars in the lens. The excess sugar within the lens is reduced by aldose reductase to its alcohol, but the lens capsule is relatively impermeable to sugar alcohols. Because of the excess sugar alcohol (polyol), the lens imbibes water, causing osmotic imbalance. Eventually, increased sodium and decreased potassium levels and decreased glutathione levels lead to cataract formation. Topical administration of aldose reductase inhibitors have been shown to prevent the cataract in rats.
  
  Section::::Asthma and COPD.
   Turbid (cloudy) urine may be a symptom of a bacterial infection, but can also be caused by crystallization of salts such as calcium phosphate.
  
  Section::::Characteristics.:pH.
  
  The pH normally is within the range of 5.5 to 7 with an average of 6.2. In persons with hyperuricosuria, acidic urine can contribute to the formation of stones of uric acid in the kidneys, ureters, or bladder. Urine pH can be monitored by a physician or at home.
   Infection, disease, medicines, or food can all affect urine color temporarily. For instance, cloudy or milky urine usually accompanied by bad smell possibly indicates urinary tract infection, excessive discharge of crystals, fat, white blood cells, red blood cells, or mucus.
  
  Dark urine that looks brown but clear might be a warning sign of a serious liver disease like hepatitis or cirrhosis. In which, an excess of bilirubin being discharged through urine.
   The amount of protein being lost in the urine can be quantified by collecting the urine for 24 hours, measuring a sample of the pooled urine, and extrapolating to the volume collected.
  
  Also a urine dipstick test for proteinuria can give a rough estimate of albuminuria. This is because albumin is by far the dominant plasma protein, and bromophenol blue the agent used in the dipstick is specific to albumin.
  
  Section::::Treatment.
   In some cases, reabsorption is indirect. For example, bicarbonate (HCO) does not have a transporter, so its reabsorption involves a series of reactions in the tubule lumen and tubular epithelium. It begins with the active secretion of a hydrogen ion (H) into the tubule fluid via a Na/H exchanger:
  
  BULLET::::- In the lumen
  
  BULLET::::- The H combines with HCO to form carbonic acid (HCO)
  
  BULLET::::- Luminal carbonic anhydrase enzymatically converts HCO into HO and CO
  
  BULLET::::- CO freely diffuses into the cell
  
  BULLET::::- In the epithelial cell
   The drug causes a reddish discoloration of the urine (chromaturia), which can look like blood in the urine.
  
  Section::::Properties.
  
  Hydroxocobalamin acetate occurs as odorless, dark-red orthorhombic needles. The injection formulations appear as clear, dark-red solutions. It has a distribution coefficient of 1.133 × 10-5 and a pKa of 7.65.
  
  Section::::Causes of deficiency.
  
  Injection of hydroxocobalamin is used to rectify the following causes of vitamin B deficiency (list taken from the drug prescription label published by the U.S. Food and Drug Administration)
   The two main types of dialysis, hemodialysis and peritoneal dialysis, remove wastes and excess water from the blood in different ways. Hemodialysis removes wastes and water by circulating blood outside the body through an external filter, called a dialyzer, that contains a semipermeable membrane. The blood flows in one direction and the dialysate flows in the opposite. The counter-current flow of the blood and dialysate maximizes the concentration gradient of solutes between the blood and dialysate, which helps to remove more urea and creatinine from the blood. The concentrations of solutes normally found in the urine (for example potassium, phosphorus and urea) are undesirably high in the blood, but low or absent in the dialysis solution, and constant replacement of the dialysate ensures that the concentration of undesired solutes is kept low on this side of the membrane. The dialysis solution has levels of minerals like potassium and calcium that are similar to their natural concentration in healthy blood. For another solute, bicarbonate, dialysis solution level is set at a slightly higher level than in normal blood, to encourage diffusion of bicarbonate into the blood, to act as a pH buffer to neutralize the metabolic acidosis that is often present in these patients. The levels of the components of dialysate are typically prescribed by a nephrologist according to the needs of the individual patient.
   Theophylline is excreted unchanged in the urine (up to 10%). Clearance of the drug is increased in children (age 1 to 12), teenagers (12 to 16), adult smokers, elderly smokers, as well as in cystic fibrosis, and hyperthyroidism. Clearance of the drug is decreased in these conditions: elderly, acute congestive heart failure, cirrhosis, hypothyroidism and febrile viral illness.
   Section::::History.
  
  The first known description of the medicine appears in the "Historia general de las cosas de la Nueva España" (1560–1564) by the Spanish Franciscan missionary and ethnographer Bernardino de Sahagún. In the most famous surviving manuscripts of the work, the Florentine Codex, Sahagún called it by its Nahuatl name, "coatli", given by Aztec healers. He described its unusual property of turning the color of water that comes in contact with it to bright blue: ""...patli, yoan aqujxtiloni, matlatic iniayo axixpatli" [...it is a medicine, and makes the water of blue color, its juice is medicinal for the urine]".
   Urine is difficult to detect as many of the naturally occurring compounds within urine are unstable and react freely with common disinfectants like chlorine, creating a large number of disinfection by-product (DBP) compounds from the original organic chemicals in urine.
   Reabsorption is a two-step process beginning with the active or passive extraction of substances from the tubule fluid into the renal interstitium (the connective tissue that surrounds the nephrons), and then the transport of these substances from the interstitium into the bloodstream. These transport processes are driven by Starling forces, diffusion, and active transport.
  
  Section::::Formation of urine.:Reabsorption.:Indirect reabsorption.
   Filtration depends on a number of factors including the pH of the urine, it having been shown that the drugs that act as weak bases are increasingly excreted as the pH of the urine becomes more acidic, and the inverse is true for weak acids. This mechanism is of great use when treating intoxications (by making the urine more acidic or more alkali) and it is also used by some drugs and herbal products to produce their interactive effect.
  
  Section::::Pharmacokinetic interactions.:Excretion interactions.:Bile excretion.
   In addition to the Fogerty originals, "Bayou Country" also features a storming version of Little Richard's "Good Golly Miss Molly" with slightly changed lyrics; instead of the result of the gift of a diamond ring being, "When she hugs me, her kissin' make me ting-a-ling-a-ling," John Fogerty sang, "Would you pardon me a kissin' and a ting-a-ling-a-ling?" The raucous "Keep On Chooglin'", laced with sexual innuendo, would become a concert show-stopper for the band.
  
  Section::::Reception.
   Briefly, to excrete free water from urine, the urine flow (which is solute clearance + free water clearance) will equal the rate of solute excretion divided by the urine osmolality. With a diet of only solute poor beer, only about 200–300 mOSM (normal 750 mOSM to greater than 900 mOSM) of solute will be excreted per day, capping the amount of free water excretion at four liters. Any intake above 4 liters would lead to a dilution of the serum sodium concentration and thus hyponatremia.
   The kidney's resorptive mechanisms are particularly energetic, using nearly 100% of the O supplied. Thus, the kidney is particularly sensitive to reduction in blood supply.
   The kidneys help maintain the water and salt level of the body. Any significant rise in plasma osmolality is detected by the hypothalamus, which communicates directly with the posterior pituitary gland. An increase in osmolality causes the gland to secrete antidiuretic hormone (ADH), resulting in water reabsorption by the kidney and an increase in urine concentration. The two factors work together to return the plasma osmolality to its normal levels.
   Diuretics, sometimes known as ‘water pills’, are drugs which draw excess fluid from the tissues of the body and convert it into urine. They are used for the swelling and bloating of premenstrual syndrome, for treating high blood pressure and, in older people, for heart failure caused by weakening of the heart’s pumping mechanism. Diuretics are used to pass drug test because they increase the amount of urine produced by the body. By increasing the amount of urine, it dilutes any drugs in the urine, which makes it harder to identify drugs. Examples of diuretics and masking agents are: bumetanide, chlorothiazide, furosemide, hydrochlorothiazide, probenecid, spironolactone (canrenone), triameterene, and trichlormethiazide.
  
raw_presuppositions: Urine shouldn't be clear after drinking.
raw_corrections: Urine is clear because alcohol forces you to urinate more often than needed. 