Hives result from dilation of capillaries which allow fluid to flow out into the surrounding tissue which is the epidermis. They resolve when the body absorbs this fluid. The border of a hive is described as polycyclic, or made up of many circles, and changes as fluid leaks out and then is absorbed. Pressing on a hive causes the skin to blanch (turn pale as blood flow is interrupted), distinguishing it from a bruise or papule. Hives may appear immediately or after a delay. Hives can last for a few minutes or a few days, and vary from person to person. Also, a burning sensation occurs. A serious reaction is most likely to occur for patients where the hives occur with less than 3 minutes of exposure (during a cold test). Cause
The hives are a histamine reaction in response to cold stimuli, including a drastic drop in temperature, cold air, and cold water. There are many causes for cold hives, most are idiopathic (meaning they have no known cause). Some rare conditions can cause cold hives, and it can be useful to test for these conditions if the cold hives are in any way unusual. Scientists from the USA National Institutes of Health have identified a genetic mutation in three unrelated families that causes a rare immune disorder characterized by excessive and impaired immune function: immune deficiency, autoimmunity, inflammatory skin disorders and cold-induced hives (cold urticaria). "The mutation discovered occurs in a gene for phospholipase C-gamma2 (PLCG2), an enzyme involved in the activation of immune cells.
Emphysematous cystitis is a rare type of infection of the bladder wall by gas-forming bacteria or fungi. The most frequent offending organism is E. coli. Other gram negative bacteria, including Klebsiella and Proteus are also commonly isolated. Fungi, such as Candida, have also been reported as causative organisms. Citrobacter and Enterococci have also been found to cause emphysematous cystitis. Although it is a rare type of bladder infection, it is the most common type of all gas-forming bladder infections. The condition is characterized by the formation of air bubbles in and around the bladder wall. The gas found in the bladder consists of nitrogen, hydrogen, oxygen, and carbon dioxide. The disease most commonly affects elderly diabetic and immunocompromised patients. The first case was identified in a post-mortem examination in 1888. Signs and symptoms
Signs and symptoms of emphysematous cystitis include air in the bladder wall, altered mental status, severe abdominal pain, weakness, dark urine, dysuria, fever, lethargy, vomiting, as well as white blood cells and bacteria in the urine. Where some patients may be asymptomatic, others may present with septic shock. Symptoms can vary greatly from patient to patient, which makes the disease difficult to diagnose. In some cases of emphysematous cystitis, patients do not even claim to have any urinary symptoms. Urinary symptoms can include blood in the urine, increased urinary frequency, urgency, occasional incontinence, difficulty voiding, and burning sensation. Emphysematous cystitis is often indicated in patients who have air in the urine. In some cases, emphysematous cystitis can cause thickening of the bladder wall.