Laboratory investigation of peritoneal fluids: an updated practical approach based on the available evidence

Even though analysis of peritoneal fluids (PF) is often requested to medical laboratories for biochemical and morphological tests, there is still no mutual agreement on what the most appropriate way is to manage PF samples and which tests should be appropriately executed. In this update, we tried to identify the most useful tests for PF analysis to establish best practice indications. We performed a literature review and examined available guidelines to select the most appropriate tests by an evidence-based approach. Accordingly, the basic PF profile should include (1) serum to effusion albumin gradient and (2) automated cell counts with differential analysis. This profile allows to determine the PF nature, differentiating between 'high-albumin gradient' and 'low-albumin gradient' effusions, which helps to identify the pathophysiological process causing the ascites formation. Restricted to specific clinical situations, additional tests can be requested as follows: PF lactate dehydrogenase (LDH) and glucose, to exclude (LDH) or confirm (glucose) secondary bacterial peritonitis; PF total protein, to differentiate ascites of cardiac origin from other causes; PF (pancreatic) amylase, for the identification of pancreatic ascites; PF bilirubin, when a choleperitoneum is suspected; PF triglycerides, in differentiating chylous from pseudochylous ascites and PF creatinine, to detect intraperitoneal urinary leakage.

Malignant peritoneal mesothelioma and Crohn disease

AIMS

Mesothelial reaction simulating peritoneal diffuse malignant mesothelioma (MM) has been reported in the setting of Crohn ileitis. To our knowledge, peritoneal MM arising in patients with inflammatory bowel disease (IBD) has not been reported. The purpose of this study is to report the clinicopathological characteristics of patients with peritoneal MM and IBD.

METHODS

A database of approximately 3800 MM was reviewed for cases of MM in patients with IBD.

RESULTS

Three patients (0.08%) with peritoneal MM and Crohn disease (CD) were identified, including two women and one man ranging in age from 56 to 65 years. All had a long-standing history of diarrhoea and an established diagnosis of CD of 3 years or greater duration. Two had epithelial MM and one had biphasic MM. Only one had documented asbestos exposure.

CONCLUSIONS

Peritoneal MM occurs rarely in patients with IBD, but interestingly, has only been observed in the setting of CD and not in patients with ulcerative colitis. Chronic inflammation has been associated with the development of MM in rare instances and these three cases suggest that CD with transmural inflammation may also be a precursor. The precise role of CD-related transmural inflammation in the carcinogenesis of peritoneal MM remains to be determined.

Comparison of genomic abnormality in malignant mesothelioma by the site of origin

AIMS

Malignant mesothelioma (MM) results from the accumulation of a number of acquired genetic events at the onset. In MM, the most frequent changes are losses in 9p21, 1p36, 22q12 and 14q32, and gains in 5p, 7p and 8q24 by comparative genomic hybridisation analysis. We have examined various genomic losses and gains in MM and benign mesothelial proliferation by fluorescence in situ hybridisation (FISH) analysis. 9p21 deletion was reported to be less frequent in peritoneal than in pleural MMs. This study analysed various genomic losses and gains in MM by the site of origin using FISH analysis.

MATERIALS AND METHODS

We performed FISH analysis using paraffin-embedded tissues from 54 cases (40 pleural and 14 peritoneal) of MMs and compared the frequency of genomic abnormality by the site of origin.

RESULTS

9p21 deletion was shown in 34 of 40 cases (85%) of pleural MMs, and was less frequent in five of 14 cases (36%) of peritoneal MMs (p<0.001) by FISH analysis. By contrast, 5p15 and 7p12 amplification was more significantly frequent in peritoneal than in pleural MMs. No difference between the two sites of MM in other genes was found.

CONCLUSIONS

9p21 homozygous deletion assessed by FISH has been reported to be useful for differentiating MM from reactive mesothelial proliferation, but it should be noted that 9p21 deletion was less frequent in peritoneal MM. Our study suggests that the pathway of the genetic abnormality might vary between pleural and peritoneal MM.

BRIGE FORMATION AND CYTOPLASMIC FLOW BETWEEN PHAGOCYTIC CELLS

A simple chamber was constructed for observation of cells at 37°C and under high magnification. Rabbit peritoneal histiocytes observed in this chamber manifested a constant interaction, which lasted as long as the preparation itself. This interaction consisted of formation of cytoplasmic bridges and flow of cytoplasm between the cells. Lung macrophages formed bridges both between themselves, and with peritoneal histiocytes. On the other hand, no bridges were noticed between histiocytes and polymorphonuclears or fibroblasts. BCG bacteria were observed passing from one histiocyte to another. Autoradiographic studies suggest that RNA may be transferred from one cell to another. The possible significance of these observations is discussed.

ELECTRON MICROSCOPY OF IN VITRO ENDOCYTOSIS OF T2 PHAGE BY CELLS FROM RABBIT PERITONEAL EXUDATE

Macrophages from rabbit peritoneal exudate cells incubated in vitro with T₂ bacteriophage from 10 up to 120 minutes show phage particles adsorbed to cell membranes, in the process of being engulfed by means of rhopheocytosis, micropinocytosis, and phagocytosis, and localized within dense vacuoles, semi-dense vacuoles, and clear vacuoles of the cytoplasm. The electronmicrographs suggest that newly formed endocytic vacuoles containing phage particles fuse with one another and also fuse with dense bodies of the cytoplasm as they migrate towards the cell interior, thus yielding larger vacuoles of varying densities containing higher concentrations of phage. The polymorphonuclear cells present in a small proportion in the peritoneal exudate cells also endocytosed phage particles. The T₂ particles are found in large cytoplasmic vacuoles surrounded by an electron-opaque material presumably derived from cytoplasmic granules. No disintegration of T₂ phage within the macrophage following incubations up to 120 minutes could be demonstrated; however, disrupted phage particles were noted within cytoplasmic vacuoles of polymorphonuclear leucocytes after 15 minutes' incubation.

LYSOSOMAL ACID HYDROLASES IN MICE INFECTED WITH BCG

Experiments are reported dealing with the increase of lysosomal acid hydrolases induced by BCG infection. Acid hydrolases were determined quantitatively in peritoneal MP, liver homogenate, and plasma of normal and BCG-infected mice. A significant increase of acid phosphatase, beta-glucuronidase, and cathepsin was found in MP and liver homogenate of BCG-infected mice. In plasma also a significant increase of acid phosphatase and beta-glucuronidase was noticed. The results of the determination of the enzymes in centrifugally separated subcellular fractions of liver homogenate indicated clearly that the acid hydrolases associated mainly with the "large granular" fraction, which consists of mitochondria, lysosomes, and microsomes and that infection with BCG caused significant increase of the enzymes specifically in this fraction. Differences in the pattern of location among centrifugally separated fraction of liver homogenate were observed between acid phosphatase and the other two acid hydrolases. MP cultured in vitro doubled their acid phosphatases content within 24 hours, whereas beta-glucuronidase rather decreased in the same cells.