The urinary system is the set of structures for the secretion and excretion of waste products of metabolism in animals. In particular, it produces urine to allow the elimination of nitrogenous waste, that is why the animals that produce urine are called ureotelic, unlike other organism species that produce ammonia (ammoniotelic) or uric acid (uricotelic) .
The urea, derived from ammonia, is dissolved with water and converted in the kidneys in urine to be eliminated without creating dangers for the organism. In humans, the urinary tract is made up of: kidneys, excretory channels (chalices, pelvis, ureter), bladder, urethra and sphincter muscles.
The urinary system mainly plays the function of blood clearance and elimination of waste contained therein. This purification takes place in the kidneys, the main organ of the excretory apparatus, consisting of a medullary area including the renal pyramids, and a cortex area.
The basic structural and functional unit of the kidney is the nephron (each kidney contains about one million of them) constituted by the Malpighian corpuscle in turn composed of the glomerulus, which is located in the cortical part of the kidney, the Bowman’s capsule and the renal tubule, a duct (from 4.5 cm to 6.5 cm) placed in parallel with the other adjacent in which we distinguish four portions, each of which has its own function in the formation of urine:
In the glomerulus there is an indiscriminate filtration of plasma: the blood, through the afferent arteriole of the renal circulation, arrives in the glomerulus where, due to the pressure determined by the presence of the efferent arteriole of diameter much smaller and the presence of fenestrations of this vessel that contribute to the variation of pressure, through a filter formed by podocytes. At the end of this process produces the glomerular ultrafiltrate (in the kidneys pass about 79 liters/h of blood, will produce 160-180 liters/day of filtrate) , which, however, must be further filtered before becoming urine (1.5 liters/die). Then it passes into the renal tubule and in this way, from ultrafiltrate are selectively reabsorbed water and sodium ions and other materials secreted, to obtain the urine. The urine is continually formed in the kidneys and conducted through the ureters to the bladder, which can contain up to 400-600 ml of urine. The circular muscles called sphincters have the task of preventing the involuntary leakage of urine. Generally small quantities of urine pass from the ureter to the bladder every 10-15 sec. When this reaches an average of about 150-250 ml, through the signaling of nerve endings has the contraction of the detrusor muscle, which allows the release of the sphincters and the elimination of urine through the urethra. At the level of the connection between the bladder and ureter there is a valve with an anti-reflux mechanism that prevents urine to flow from the bladder to the kidneys and this is a defense against bacterial infections.
The male and female urinary tract is frequently subject to numerous diseases. Among these the most common are:
The urinary tract infections (UTIs ) are very common disease, it is estimated that each year in Italy hit approximately 2-3 million of people. They are rare in adolescents and males at a young age, but are most common in women and in children under the age of 2. They usually arise when pathogenic microorganisms penetrate through the urethra, proliferate and multiply inside the urinary tract and cause acute or chronic inflammation that can affect the urinary bladder and its annexes. There are a wide variety based on the etiology and type of damage caused. UTIs occur most commonly in the lower tract (urethra and bladder) but if left untreated can spread to upper urinary tract (ureters and kidneys). The bladder infection (cystitis) is certainly the most common type of UTI. The urethra infection is called urethritis. The kidney infection or pyelonephritis is a disease that requires urgent treatment as it can lead to the loss of renal function and, in severe cases, even death of the individual if not treated promptly.Pathogens responsible for UTI
The pathogens causing these infections, easily detectable with a simple urine culture, are generally of the species Gram- and in particular the Escherichia coli is the pathogen responsible for 80% of all UTI in adults. It is a bacteria normally present in the colon and, coming from the skin of the genitals and anus, can penetrate through the urethra; then in a lesser degree there are other Enterobacteriaceae such as Proteus, Klebisella, Pseudomonas. Even some Gram+ can cause, to a lesser extent, urinary tract infection and among these the most common are Staphylococcus saprophiticus (in 5-15% of cases) and Staphylococcus aureus.
There are also microorganisms usually normal components of the intestinal flora, genital and/or perineal or those usually responsible for sexually transmitted infections, such as Neisseria gonorrhoeae and Chlamydia trachomatis, Mycoplasma hominid, or fungal infection by Candida albicans. In these cases, detection of the pathogen is usually done by taking a smear of secretions of the urogenital tract and make a microscopic investigation.
As part of UTI cystitis is the most common infection of the lower urinary tract and is an inflammation of the bladder, usually caused by a bacterial infection or more rarely due to trauma, allergies or conditions of decreased immune resistance (eg following radiation therapy). In most cases, cystitis is due to bacterial infections caused by Escherichia coli, but in a smaller number of cases can also be caused by other bacteria such as Proteus, Klebisella, Pseudomonas, Staphylococcus aureus and Staphylococcus saprophiticus that colonize the bladder.
Cystitis affects more frequently women because their urethra is shorter (about 5 cm) than that of men (about 16 cm) and therefore is higher for women the risk of contamination by fecal bacteria that can more easily trace the urethra to the bladder. It is estimated that about 25% of adult women suffer from cystitis at least once a year and that one in two women over a lifetime will suffer at least one episode of acute cystitis. In particular, the incidence increases with age: is very low up to 20 years, and it depends by the high frequency of sexual activity and with pregnancies increases until after menopause. The probability of recurrent cystitis increases with the increase of the number of previous cases, while it decreases if longer is the interval between one episode and the other cystitis. These infections are still frequent in man over 50 years old favorite by prostatic hypertrophy.
When the infection reaches the upper urinary tract then you may have additional symptoms such as chills, high fever, nausea, subcostal pain and vomit.
Cystitis are classified according to the clinical characteristics and the presence or absence of underlying diseases, in complicated and uncomplicated cystitis. The latter, which are the ones of greatest interest, may occur in acute or chronic form.
The acute cystitis usually occurs suddenly and is characterized by urinary urgency, burning especially at the end of urination, pyuria, hematuria, a feeling of heaviness in the lower abdomen, sometimes a mild fever that can become high with chills in case of purulent bladder retention. Generally the acute and uncomplicated cystitis does not cause fever, but if the temperature rises considerably it is possible that the infection has spread to the upper urinary tract. The acute cystitis can also be presented in:
It is the acute inflammation, occasional and transient, of infectious origin of the bladder which is the most common form with a benign course and mostly affects the population of healthy women, that it is estimated at least one episode of that infection, in all women within 40 years of age. The age range would seem to correlate with the period of onset of sexual activity. The incidence of cystitis in man is 100 times lower than that of the woman. This is due to the particular anatomy of man in which the urinary meatus is located in a distinct anatomic area and thanks to the length of the urethra.
It is the acute inflammation of infectious origin of the bladder involving the capillaries of the submucosa. It is considered a form of simple cystitis with its injury characteristics (more advanced and profound of the simple form). It has a wider range of ages ranging from 15 to 80 years, and represents 10% of the total urinary infections. This form can also be caused by exposure to ionizing radiation and the use of some cytotoxic drugs. Unlike the first form, in this there is the appearance of hematuria.
The recurrent or chronic cystitis is generally determined by the evolution of the acute form with the same clinical features of simple cystitis but less intense and more prolonged, with the only difference of the frequency, so that it tends to recur. It was established that three episodes in one year can be the manifestation of recurrent cystitis. These may recur in the form of re-infection if normally appear weeks or months after therapy, or as a recurrence, if they develop a few days after discontinuation of therapy.
The bladder has a considerable resistance to infections and in normal conditions the urine in it is sterile. However, there are some conditions that make the body more susceptible to bacterial attack. These microorganisms can reach the bladder by ascending (slope along the urethra after issuing with feces), descending (down from the kidney) or by blood. Then the cystitis may occur due to the presence of numerous predisposing conditions:
The diagnosis of cystitis and urinary tract infection is based on the examination of the urine, on urine culture and consequently on bacterial counts, analysis which provides the cleansing of the skin around the mouth of the urethra (penis in male and vagina in female) and the collection of the intermediate flow of the urine of the patient. In this way sample contamination by bacteria normally present in the skin is avoided.
The analysis of the urine can detect the presence of white blood cells in the urine (leucocyturia) that, if in high number, are indicative of an active infection. It is possible the execution of an antibiogram in order to determine the type of bacteria responsible for the infection and set accordingly a targeted antibiotic therapy.
If the cystitis does not regress rapidly, if there have been attacks rather frequent or it tends to become chronic is appropriate to examine the entire urinary tract with a cystoscopy or other specialized tests that allow to highlight any other diseases and then to intervene with specific therapies.
A specific examination may be useful especially in children who may have a bladder-urethral reflux, that is an alteration, sometimes congenital, of the locking mechanism between the bladder and the urethra, a condition that easily predisposes to infection.
The majority of urinary tract infections are treated with oral antibiotics, even if in some cases they are also used vaccines, in addition to functional foods and probiotics to restore a normal vaginal bacterial flora and so provide a natural barrier to pathogenic bacteria. Among the antibiotics, the drugs most commonly used are listed below even if the type of drug used and the duration of treatment depend on the type of bacteria responsible for the infection identified by urine culture:
In most cases we note an improvement in symptoms within two days. The use of antibiotic therapy, however, must be considered only in case of actual need, since most of the pathogens tend easily to establish the resistances to these molecules, making vain the treatment and determining the onset of recurrence. These recurrent urinary tract infections can be treated with antibiotics in long duration and low dosage. The execution of a urine culture at end of treatment ensures the elimination of the infection. In case of UTI caused by chlamydia or mycoplasma, the treatment requires a longer duration and are used other types of antibiotics such as tetracycline or doxaciclina. In case of predisposing factors such as calculi or IPB is possible recourse to surgical therapy.
In addition to classical antibiotic therapy there are some simple behavioral precautions that can reduce both the onset of these infections that the attenuation of the characteristic clinical signs. What is often overlooked, but of proven efficacy, is the normal hygiene. These rules alone are responsible for the disappearance of the infection and are also able to reduce the number of infectious episodes. These include:
In patients with cystitis in addition to following the rules listed above is also important to modify the diet, as it has been observed that some dietary factors influence susceptibility to the development of such infections.
To reduce the risk of developing urinary tract infections is therefore important:
The correlation between diet and urinary infections is certainly correlated to two important factors that are hydration and acidification.
Hydration also guarantee a correct functioning of the colon that is charged to the resorption. A regular bowel function in fact hardly encourages the proliferation of fecal bacteria. So it is indicated in these cases the introduction of adequate intakes of foods rich in fibers and in the most resistant cases the association of any fiber supplements that are like ordinary laxatives, but unlike these do not prevent the absorption of fat-soluble vitamins.
It has been noted that what influence the non-proliferation of urinary bacteria is the use of diets with high acid residual. These in fact lower the urinary pH and consequently the non-engraftment to the walls of the bacteria. Our body in fact is able to implement such a defense by light catabolic state , such as overnight fast that acidify the urine but it may sometimes not be enough. One of the acidifying products is the cranberry juice whose effectiveness has been demonstrated recently, pointing out that when taken certainly provides a good supply of fluids and vitamins. A recent study has shown that the daily intake of 300 ml of cranberry juice reduces by about 50% the relapse. In particular, it seems that the component of cranberry juice responsible for this is the amount of vitamin C. The rationale on the use of diets with a high amount of acid also finds its response in infections caused by stones. In order to have an adequate supply of acid residual food should also keep in mind the foods that have the opposite effect that is alkalizing. These in fact are the buffer that is compensate the acidity by neutralizing the effects described above. Therefore it is appropriate to increase the acid residual food and decrease those in alkaline residue.