The peritoneal fluid it is an ultrafiltrate of plasma, also known as ascitic fluid. The accumulation of this fluid in the peritoneal cavity is called ascites, which can be caused by liver cirrhosis, neoplastic processes, congestive heart failure, tuberculous or pyogenic peritonitis, pancreatitis or nephrosis, among others..
Peritoneal fluid can accumulate due to an imbalance between hydrostatic and oncotic pressure, modifying the volume between the intravascular and extravascular compartments..
Depending on the results of the studies, it is possible to determine if it is a transudate or an exudate and, therefore, elucidate the possible cause of ascites..
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Normal peritoneal fluid is a transudate. It is characterized by low protein concentration, plasma-like glucose, few leukocytes, no fibrin clots, and few or absent red blood cells..
Likewise, it contains very low concentrations of some enzymes, such as: lactate dehydrogenase (LDH), adenosine deaminase (ADA), amylase.
The peritoneal fluid is located in the peritoneal cavity and is delimited between the visceral peritoneal membrane and the parietal peritoneal membrane..
The function of the peritoneal fluid is to lubricate the parietal and visceral peritoneal membrane, avoiding friction of the organs in the abdominal cavity..
On the other hand, the peritoneal membrane functions as a filter, that is, it is semi-permeable and maintains a balance with the flow of extracellular fluid..
Under normal conditions, the peritoneal fluid that diffuses into the peritoneal cavity is then reabsorbed into the subdiaphragmatic lymph nodes. This maintains a balance between the amount that is produced and that which is reabsorbed..
The peritoneal membrane lines the abdominal cavity. This has a visceral and a parietal leaf.
The former has a larger surface area and is supplied by the mesenteric arteries and continues towards the portal vein, while the parietal peritoneum has a smaller surface area and is supplied mainly by the arteries and veins of the abdominal wall..
Transdiaphragmatically there is a constant drainage of the lymphatic circulation that absorbs fluid.
When there is an increase in portal pressure, together with an increase in the renal reabsorption of sodium, the plasma volume increases, which leads to the production of excess lymph.
The accumulated peritoneal fluid must be analyzed from the physical, biochemical and cytological point of view. These characteristics will determine if it is a transudate or exudate.
Transudate is simply the accumulation of fluid, without inflammation and / or infection. That is, there are no significant changes in its composition. There is also no involvement of the peritoneum. Example of ascites with a characteristic of transudate: cardiac ascites, ascites due to nephrotic syndrome and ascites due to cirrhosis.
In general, excess fluid with transudate characteristics is caused by a decrease in plasma proteins (hypoproteinemia), which translates into a reduction in osmotic pressure and an increase in capillary permeability and venous pressure. All of this increases water retention while lymphatic pressure decreases..
Finally, the obstruction of the lymph circulation causes excess fluid in the peritoneal cavity. The volume can be up to several liters, which significantly distens the patient's abdomen.
In the exudates there is not only accumulation of fluid, but also other factors that drastically modify the composition of the peritoneal fluid participate.
In the exudates, in addition to the lymphatic obstruction, there is a direct involvement of the peritoneum, which can be due to: an infectious and inflammatory process or infiltration or necrosis. Infections can be caused by bacteria, fungi, viruses or parasites.
Examples of ascites with fluid with exudate characteristics are: pancreatic ascites, peritoneal carcinoma, and peritoneal tuberculosis, among others..
Peritoneal fluid should be studied to determine the etiology of excess fluid in the peritoneal cavity. The sampling is done through a procedure called paracentesis..
The peritoneal fluid can be performed the following studies: cytochemical analysis, Gram, BK, culture and biopsy.
The cytochemical analysis clarifies whether it is in the presence of a transudate or exudate. Establishing this difference is of crucial importance in order to know the possible causes and establish an accurate therapeutic procedure to be followed..
On the other hand, the peritoneal fluid is sterile by nature, therefore, it should not contain any type of microorganisms.
In this sense, the Gram is a quick tool to test the possibility of an infection, being especially useful in secondary peritonitis. For its part, BK can help in the rapid diagnosis of peritoneal tuberculosis, while culture is the study that confirms the existence or absence of infection.
20-50 ml of sample are taken depending on the number of analyzes indicated. 10 ml should be inoculated in a blood culture bottle for aerobic microorganisms, and 10 ml in a blood culture bottle for anaerobes..
The rest of the peritoneal fluid sample is deposited in several sterile tubes to perform Gram and BK, cytochemical, etc..
The blood culture bottles are incubated for 24-48 hours. The contents of the bottle should be seeded in enriched culture media, such as: blood agar and chocolate agar, where most microorganisms grow.
A Mac Conkey plate for Gram negatives and a Sabouraud agar plate for fungal research can also be attached..
If peritoneal tuberculosis is suspected, the sample can be collected in a sterile tube and from there inoculated directly onto the Löwenstein-Jensen medium..
The sample is collected in sterile tubes. The cytochemical analysis includes the physical aspects, the biochemical analysis and the cytological study.
The parameters observed in the physical study are: appearance of the liquid, color, density. The basic biochemical study includes glucose, proteins and LDH. However, other metabolites can be attached such as: amylase, albumin, ADA, among others..
Density: 1.006-1.015.
Appearance: Transparent.
Color: light yellow.
Rivalta reaction: negative.
Proteins: < de 3 g%.
Albumin: < de 1,5 g/dl.
Glucose: normal, similar to plasma.
LDH: low (< 200 UI/L).
Amylase: value similar to or less than plasma.
ADA: < 33 U/L.
Fibrinogen: absent.
Coagulation: never.
Cell count: < 3000 cel/mm3
Neoplastic cells: absent.
Bacteria: absent.
Leukocytes: few.
Red blood cells: scarce.
Density: 1.018-1.030.
Appearance: cloudy.
Color: dark yellow or whitish.
Rivalta reaction: positive.
Proteins:> 3 g%.
Albumin:> 1.5 g / dl.
Glucose: decreased.
LDH: increased, especially in neoplastic processes (> 200 IU / l).
Amylase: increased in case of pancreatitis.
ADA (adenosine deaminase enzyme):> 33 U / L in case of tuberculous ascites.
Bilirubin: increased (indicated only when the color of the liquid is dark yellow or brown).
Fibrinogen: present.
Coagulation: frequent.
Cell count:> 3000 cells / mm3
Neoplastic cells: common.
Bacteria: common.
Leukocytes: abundant.
Red blood cells: variables.
It has been noted that the peritoneal fluid may turn cloudy, white (chylous), but with low cell counts. This is due to the administration of certain calcium antagonist drugs, such as: lercanidipine, manidipine, dihydropyridines, nifedipine, without associated infection..
Chylous ascites (increased triglycerides and chylomicrons) can have other causes, such as: neoplasms, nephrotic syndrome, pancreatitis, liver cirrhosis, among others. It is also called lymphatic ascites..
If the fluid is cloudy and there are a large number of leukocytes, peritonitis should be considered. Peritonitis can be spontaneous, secondary, or tertiary.
Spontaneous or primary peritonitis is produced by microorganisms that come from a bacterial translocation (passage of bacteria from the intestine to the mesenteric ganglia). This is how the bacteria pass into the lymph, the peritoneal fluid and the systemic circulation..
This process is favored by a significant increase in the intestinal microbiota, an increase in the permeability of the intestinal mucosa, and a decrease in local and systemic immunity..
Bacterial peritonitis occurs in a large percentage in patients with liver cirrhosis.
The most isolated microorganism is Escherichia coli, however, others are available, such as: Staphylococcus aureus, Enterobacter cloacae, Klebsiella pneumoniae, Enterococcus faecalis, Enterococcus faecium, among others.
Secondary peritonitis is caused by the passage of septic content into the peritoneal cavity through a fissure in the gastrointestinal wall. The causes of wall rupture can be traumatic, post-surgical, gastric ulcer perforation, acute appendicitis, among others..
Whereas, tertiary peritonitis is difficult to diagnose. It can be caused by an unresolved or persistent primary or secondary peritonitis. Occasionally, low pathogenic bacteria or fungi are isolated, but without finding the primary infectious focus. It can also be diffuse, without an infectious agent.
Tertiary peritonitis has a poor prognosis, it usually has a high mortality despite the installation of aggressive treatment.
Presence of bacteria in the peritoneal fluid with a low white blood cell count. It may be due to the onset of spontaneous bacterial peritonitis, or a secondary infection with an extraperitoneal origin.
The main cause is previous pulmonary tuberculosis. It is believed that it can affect the peritoneum mainly by lymphatic dissemination and secondly by hematogenous route.
The Mycobacterium tuberculosis it can reach the intestine by swallowing infected sputum. This involves the intestinal submucosa, the intramural, regional and mesenteric nodes..
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