Differential diagnosis of diarrhoea in patients with neuroendocrine tumours:A systematic review

BACKGROUND Approximately 20% of patients with neuroendocrine tumours(NETs) develop carcinoid syndrome(CS),characterised by flushing and diarrhoea.Somatostatin analogues or telotristat can be used to control symptoms of CS through inhibition of serotonin secretion.Although CS is often the cause of diarrhoea among patients with gastroenteropancreatic NETs(GEP-NETs),other causes to consider include pancreatic enzyme insufficiency(PEI),bile acid malabsorption and small intestinal bacterial overgrowth.If other causes of diarrhoea unrelated to serotonin secretion are mistaken for CS diarrhoea,these treatments may be ineffective against the diarrhoea,risking detrimental effects to patient quality of life.AIM To identify and synthesise qualitative and quantitative evidence relating to the differential diagnosis of diarrhoea in patients with GEP-NETs.METHODS Electronic databases(MEDLINE,Embase and the Cochrane Library) were searched from inception to September 12,2018 using terms for NETs and diarrhoea.Congresses,systematic literature review bibliographies and included articles were also hand-searched.Any study designs and publication types were eligible for inclusion if relevant data on a cause(s) of diarrhoea in patients with GEP-NETs were reported.Studies were screened by two independent reviewers at abstract and full-text stages.Framework synthesis was adapted to synthesise quantitative and qualitative data.The definition of qualitative data was expanded to include all textual data in any section of relevant publications.RESULTS Forty-seven publications(44 studies) were included,comprising a variety of publication types,including observational studies,reviews,guidelines,case reports,interventional studies,and opinion pieces.Most reported on PEI on/after treatment with somatostatin analogs;9.5%-84% of patients with GEP-NETs had experienced steatorrhoea or confirmed PEI.Where reported,14.3%–50.7% of patients received pancreatic enzyme replacement therapy.Other causes of diarrhoea reported in patients with GEP-NETs included bile acid malabsorption(80%),small intestinal bacterial overgrowth(23.6%-62%),colitis(20%) and infection(7.1%).Diagnostic approaches included faecal elastase,breath tests,tauroselcholic(selenium-75) acid(Se HCAT) scan and stool culture,although evidence on the effectiveness or diagnostic accuracy of these approaches was limited.Assessment of patient history or diarrhoea characteristics was also reported as initial approaches for investigation.From the identified evidence,if diarrhoea is assumed to be CS diarrhoea,consequences include uncontrolled diarrhoea,malnutrition,and perceived ineffectiveness of CS treatment.Approaches for facilitating differential diagnosis of diarrhoea include improving patient and clinician awareness of non-CS causes and involvement of a multidisciplinary clinical team,including gastroenterologists.CONCLUSION Diarrhoea in GEP-NETs can be multifactorial with misdiagnosis leading to delayed patient recovery and inefficient resource use.This systematic literature review highlights gaps for further research on prevalence of non-CS diarrhoea and suitability of diagnostic approaches,to determine an effective algorithm for differential diagnosis of GEP-NET diarrhoea.     

A novel strategy for the detection and definition of HLA-specific antibodies in patients awaiting renal transplantation

Abstract Conventional testing for HLA-specific antibodies employs complement-dependent cytotoxicity (CDC) which is labour intensive and dependent on a supply of viable lymphocytes. Our strategy to minimise CDC screening is initially to screen sera by ELISA (Quikscreen) to detect HLA Class I-specific antibodies. Negative sera are then screened by flow cytometry (FCS) using lymphoblastoid cell line pools to detect HLA Class II-specific antibodies. Only Quikscreen-or FCS-positive sera are then tested by CDC and, when indicated, with an ELISA kit (PRA-STAT) for specificity definition. Of 3680 sera, 886 (24.1%) were Quikscreen positive. Of the 2794 Quikscreen-negative sera, 374 (13.4%) were FCS positive. Therefore, only 1265 of the 3680 (34.3%) sera contained HLA-specific antibodies requiring specificity definition. This novel screening strategy has significantly reduced the CDC workload of the laboratory whilst enabling the detection of additional HLA-specific antibodies.     

Suppression of serum antibody responses by pertussis toxin after respiratory tract colonization by Bordetella pertussis and identification of an immunodominant lipoprotein

Pertussis toxin (PT), a virulence factor secreted by Bordetella pertussis, contributes to respiratory tract infection and disease caused by this pathogen. By comparing a wild-type (WT) B. pertussis strain to a mutant strain with an in-frame deletion of the ptx genes encoding PT (DeltaPT), we recently found that the lack of PT confers a significant defect in respiratory tract colonization in mice after intranasal inoculation. In this study, we analyzed serum antibody responses in mice infected with the WT or DeltaPT strain and found that infection with the DeltaPT strain elicited greater responses to several B. pertussis antigens than did infection with the WT, despite the lower colonization level achieved by the DeltaPT strain. The same enhanced antibody response was observed after infection with a strain expressing an enzymatically inactive PT; but this response was not observed after infection with B. pertussis mutant strains lacking filamentous hemagglutinin or adenylate cyclase toxin, nor when purified PT was administered with the DeltaPT inoculum, indicating a specific role for PT activity in this immunosuppressive effect. In particular, there were consistent strong serum antibody responses to one or more low-molecular-weight antigens after infection with the DeltaPT strain. These antigens were Bvg independent, membrane localized, and also expressed by the closely related pathogens Bordetella parapertussis and Bordetella bronchiseptica. Two-dimensional gel electrophoresis and mass spectrometry were used to identify one of the immunodominant low-molecular-weight antigens as a protein with significant sequence homology to peptidoglycan-associated lipoprotein in several other gram-negative bacterial species. However, a serum antibody response to this protein alone did not protect mice against respiratory tract infection by B. pertussis.     

Macrophage migration inhibitory factor (MIF) gene polymorphism is associated with susceptibility to but not severity of inflammatory polyarthritis

The aim of the study was to investigate whether polymorphisms of macrophage migration inhibitory factor (MIF) determine susceptibility to or severity of inflammatory polyarthritis (IP). Genotypes for a single-nucleotide polymorphism (MIF-173*G/C) and a tetranucleotide (CATT)(n) repeat mapping to the promoter region of the MIF gene were compared between UK Caucasian IP cases (n=438) and controls (n=343). Both polymorphisms were also investigated for association with features of disease activity and severity at baseline and by 5 years. The MIF-173*C allele (OR 1.7, 95% CI 1.3-2.4, P=1.8 x 10(-4)) and the CATT(7) allele (OR 1.5, 95% CI 1.0-2.1, P=0.02) were found to be associated with increased susceptibility to IP. Furthermore, presence of the haplotype containing both associated polymorphisms was associated with a three-fold increase risk of developing IP. No association with disease severity or activity either at baseline or by 5 years was detected for either of the promoter polymorphisms studied. In conclusion, MIF is a susceptibility gene for the development of IP. The same alleles previously reported to be associated with susceptibility to juvenile idiopathic arthritis account for the increased risk. The promoter polymorphisms of MIF, investigated in this study, do not influence the severity of disease outcome by 5 years.     

Clostridium difficile colitis mimicking acute peritonitis

Five patients receiving penicillin V potassium or a cephalosporin antibiotic for 18 hours to 22 days developed fever, marked leukocytosis, and signs and symptoms that suggested right-lower-quadrant peritoneal irritation. All underwent emergency laparotomy, at which dilatation and inflammation of the ascending colon were found. Only one of the patients had profuse diarrhea, and two patients had no diarrhea prior to laparotomy. Postoperatively, Clostridium difficile colitis was diagnosed by stool toxin assay and was confirmed in one case by proctosigmoidoscopic biopsy results. Antibiotic-associated colitis must be considered in any patient who develops peritoneal signs while or after receiving antibiotics. Over a two-year period, the "acute abdomen" presentation accounted for 5.2% of all patients with C difficile colitis at our institutions. Early proctosigmoidoscopy or stool examination for C difficile or its toxin may avoid unnecessary laparotomy in such patients.     

Spontaneous resolution of an in utero perirenal urinoma associated with posterior urethral valves

Ultrasound imaging of a 26-week-gestation fetus demonstrated a large, nonemptying bladder. At 27 weeks, a distended, thick-walled bladder, left hydronephrosis, and a perirenal urinoma were present, without ascites. Observation was undertaken, as the amniotic fluid volume was normal. At 29 weeks, the left perirenal fluid collection persisted but, at 30 weeks, was absent. After delivery at 36 weeks, no ultrasound evidence for perirenal urinoma or ascites was present. Isotope renal scan showed preserved renal function bilaterally. This case illustrates that in utero urinomas associated with posterior urethral valves can resolve spontaneously, with preservation of renal function.