Review article: the aetiology, investigation and management of diarrhoea in the HIV-positive patient

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1 Alimentary Pharmacology and Therapeutics Review article: the aetiology, investigation and management of diarrhoea in the HIV-positive patient N. A. Feasey*,, P. Healey à & M. A. Gordon* *Department of Gastroenterology, University of Liverpool, Liverpool, UK. Malawi-Liverpool-Wellcome Trust Major Overseas Programme, Blantyre, Malawi. à Department of Radiology, Royal Liverpool University Hospital, Liverpool, UK. Correspondence to: Dr M. A. Gordon, University of Liverpool Gastroenterology Unit, Henry Wellcome Laboratories, Nuffield Building, Crown Street, Liverpool L69 3GE, UK. Publication data Submitted 2 February 2011 First decision 23 March 2011 Resubmitted 28 June 2011 Accepted 30 June 2011 EV Pub Online 20 July 2011 This commissioned review article was subject to full peer-review. SUMMARY Background Diarrhoea is a common presentation throughout the course of HIV disease. Aim To review the literature relating to aetiology, investigation and management of diarrhoea in the HIV-infected adult. Methods The PubMed database was searched using major subject headings AIDS or HIV and diarrhoea or intestinal parasite. The search was limited to adults and to studies with >10 patients. Results Diarrhoea affects 40 80% of HIV-infected adults untreated with antiretroviral therapy (ART). First-line investigation is by stool microbiology. Reported yield varies with geography and methodology. Molecular and immunological methods and special stains have improved diagnostic yield. Endoscopy is diagnostic in 30 70% of cases of pathogen-negative diarrhoea and evidence supports flexible sigmoidoscopy as a first line screening procedure (80 95% sensitive for CMV colitis), followed by colonoscopy and terminal ileoscopy. Radiology is useful to assess severity, distribution, complications and to diagnose HIV-related malignancies. Side effects and compliance with ART are important considerations in assessment. There is a good evidence base for many specific therapies, but optimal treatment of cryptosporidiosis is unclear and only limited data support symptomatic treatments. Conclusions The immunological response to HIV infection and antiretroviral therapy remains incompletely understood. Antiretroviral therapy regimens need to be optimised to suppress HIV while minimising side effects. Effective agents for management of cryptosporidiosis are lacking. There is an urgent need for enhanced regional diagnostic facilities in countries with a high prevalence of HIV. The ongoing roll-out of antiretroviral therapy in low-resource settings will continue to change the aetiology and management of this problem, necessitating ongoing surveillance and study. Aliment Pharmacol Ther 2011; 34: doi: /j x

2 N. A. Feasey et al. INTRODUCTION Both acute and chronic diarrhoea have been recognised as major complications of human immunodeficiency virus (HIV) infection and the acquired immunodeficiency syndrome (AIDS) since the early days of the pandemic, being described as slim disease in Africa as a result of the combination of watery diarrhoea and weight loss that was characteristic. 1 Definitions of chronic diarrhoea vary, but an accepted one is the abnormal passage of three or more loose or liquid stools per day for more than 4 weeks and or a daily stool weight greater than 200 g day. 2 While acute bacterial gastroenteritis causes blood stream invasion and death more frequently in HIV-infected than in immune-competent patients, chronic diarrhoea is also a massive problem for HIV patients untreated with antiretroviral therapy (ART). Case series from industrialised countries in the preantiretroviral (ARV) era (therefore involving untreated patients) show that 40 80% of HIV-infected patients will experience diarrhoea. 3 5 Human immunodeficiency virus has an impact on intestinal infection at all stages (by plasma CD4 count), with additional aggregation of disease in individuals who have increased susceptibility to diarrhoeal infection irrespective of CD4 count. 6 While HIV associated diarrhoea is most frequently caused by an opportunistic infection, there are many non-infectious causes which should also be considered. As the list of aetiological agents has grown both with increased experience of HIV and as powerful antiretroviral therapy (ART) has developed, so too has the array of investigations and therapeutics available to manage diarrhoea in HIV infection. THE IMPACT OF HIV ON THE GASTROINTESTINAL TRACT The Human Immunodeficiency Virus (HIV) causes progressive immunosuppression as a consequence of its tropism for CD4 + T-lymphocytes which progressively decline because of apoptosis. Following acute infection, there is a sharp initial fall in the plasma CD4 count, which is followed by recovery and then a progressive deterioration in the plasma CD4 count. Monitoring this deterioration in plasma CD4 count is the major surrogate marker of immune status and is often the principal tool in guiding the timing of initiation of ART. Plasma CD4 T-lymphocyte count is, however, an imperfect measure of immune status for a number of reasons; one of these is that the majority of CD4 + T-cells do not reside in plasma, but in mucosal surfaces, particularly the gut, where they form a major target for HIV in early infection prior to the development of a CD8+ T-cell response. Furthermore, the immunosuppression seen in HIV is extremely complex and consequent on the effects of HIV viraemia on multiple branches of the immune system. The mucosal surface of the gut is a unique interface through which water and nutrients are absorbed during digestion, where multiple commensal bacteria thrive and which forms a structural and immunological barrier against infection. It is not surprising that HIV infection causes profound changes in the GI mucosa and its functions, given the concentration of cells susceptible to HIV infection found there, nor that the GI tract is consequently a major reservoir for HIV and also a focus of viral reproduction from the earliest days of infection. 7 9 AETIOLOGY OF DIARRHOEA The aetiology of diarrhoea in HIV-infected patients is multi-factorial. Although opportunistic infections are an obvious cause to consider, there are also many noninfectious causes of diarrhoea in HIV. There is a lack of high quality prospective studies of the aetiology of diarrhoea in countries with the highest prevalence of HIV and some of the early studies, although of high quality, were constrained by both the limits of understanding of the range of opportunistic infections and the diagnostic technology available early in the HIV epidemic. Table 1 summarises studies of the aetiology of diarrhoea in HIV and Figure 1 schematically represents potential causes of diarrhoea in HIV by disease stage. INFECTIONS Different claims have been made about the relative importance of bacteria, viruses and protozoan parasites in the aetiology of infectious diarrhoea complicating HIV in different studies. A number of factors have affected the results of these studies, including the stage of HIV infection, the range of diagnostic tests available at the time of the study and the geographical location of the study. It is important to note that opportunistic infections may still be found in patients who are taking antiretroviral therapy, partly because of poor adherence. 10 Bacterial infection Human immunodeficiency virus infected patients are at risk of acute diarrhoea from the same bacterial agents of enterocolitis as those who are HIV negative. They are, however, at greater risk of prolonged infection and of invasive disease, particularly from nontyphoid Salmonellae 11 12, 13 and from Campylobacter jejuni. Recurrent invasive nontyphoid Salmonella (NTS) disease 588 Aliment Pharmacol Ther 2011; 34:

3 Review: diarrhoea in HIV-positive patients Table 1 Summary of studies of aetiology of diarrhoea in HIV-infected adults Study Subject Location Cohort size Technique Major findings Saksirisampant et al. 131 Intestinal parasites Thailand 90 stool samples Microscopy & PCR 46% positive for parasites, of which: 30% Cr.hominis, 4%Cr. meleagridis, 6%E. bieneusi 2% B. hominis, 1% C. cayetensis, 1% I. belli Goncalves et al. 132 Causes of diarrhoea case control study Dillingham et al. 133 Mortality: HIV associated diarrhoea Brazil 40 patients with diarrhoea, 60 without Microscopy, culture EIA & PCR Calicivirus, C. parvum & G. lamblia significantly associated with diarrhoea Haiti 288 patients Stool microscopy 33% had an enteric pathogen identified: Cryptosporidium spp., Giardia spp., I. belli, C. cayetanensis, and E. histolytica. Chacin-Bonilla et al. 134 Microsporidiosis Venezuela 103 patients Stool microscopy Microsporidial infections were detected in 14% and 38% had other parasitic pathogens. Chacin-Bonilla et al. 135 Cyclospora cayetanensis Venezuela 71 patients Stool microscopy Cyclospora oocysts were found in 10% Blanshard et al. 136 Chronic diarrhoea UK 155 patients Examination of stools, duodenal, jejunal and rectal biopsy specimens and duodenal aspirate for bacterial, protozoal and viral pathogens Blanshard and Gazzard 137 Pathogen negative diarrhoea UK 39 patients Follow-up of above cohort 83% had 1 pathogen: stool analysis identified the most pathogens (47%). Rectal biopsy necessary for the diagnosis of CMV and adenovirus. Duodenal biopsy was as helpful as jejunal biopsy and detected some treatable pathogens missed by other methods. Electron microscopy, impression smears and duodenal aspirate yielded little extra information. 2 small bowel neoplasm, 3 CMV Aliment Pharmacol Ther 2011; 34:

4 N. A. Feasey et al. Table 1 (Continued) Study Subject Location Cohort size Technique Major findings Sorvillo et al. 138, 139 _ENREF_83 Risk factors for Isosporiasis and cryptosporidiosis US 16,351 patients Data from AIDS surveillance analysed Isosporiasis was reported in 1%, linked to recent travel or immigration. Cotrimoxazole prevents. Cryptosporidiosis was reported in 4% Grohmann et al. 28 Enteric viruses US 222 stool samples TEM, gel electrophoresis, and EIA for rotaviruses, adenoviruses, caliciviruses, picobirnaviruses, & astroviruses Viruses detected in 35% percent of 109 faecal specimens from patients with diarrhoea and 12% of 113 specimens from those without diarrhoea (P < 0.001) Chacin-Bonilla et al. 140 Cryptosporidiosis Venezuela 29 patients 3 stool samples patient 41% had cryptosporidosis Eeftinck Schattenkerk et al. 141 Microsporidiosis Holland 55 patients with unexplained diarrhoea Janoff et al. 142 Adenovirus colitis US 51 patients with diarrhoea Upper GI endoscopy 27% had microsporidiosis TEM of tissue biospy 7% had adenovirus Greenson et al. 143 Enteric infection US 22 patients with diarrhoea Connolly et al. 34 Pathogen negative diarrhoea UK 33 patients with diarrhoea Stool negative, analysis of endoscopic biopsies using light and electron microscopy, viral culture, Distal duodenal biopsy, comprehensive barium studies, microbiological examination of six further stool samples and repeat rectal histology Mycobacterium avium-intracellulare and microsporidia were the most common occult agents in study patients with diarrhoea (5 each) Cryptosporidia were identified on five occasions, cytomegalovirus on four, Giardia lamblia on two and herpes simplex, Campylobacter jejuni, Salmonella enteritidis and Entamoeba histolytica once each. Rene et al. 144 Cytomegalovirus France 18 HIV patients with diarrhoea ante mortum Autopsy 7 had CMV colitis 590 Aliment Pharmacol Ther 2011; 34:

5 Review: diarrhoea in HIV-positive patients Diarrhoea related to HIV seroconversion Causes of diarrhoea as HIV disease progresses Causes of diarrhoea related to ART Viral load without ART CD4 count without ART CD4 count after commencing ART HIV seroconversion ART side effects Viral load (copies/ml) Bacterial infection Tuberculosis Isospora belli CD 4 count weeks Cyclospora cayatanensis Strongyloides Cryptosporidia GI malignancies microsporidia Time since infection MAC, CMV 10 years Figure 1 Scheme showing causes of diarrhoea at different stages of HIV disease: following HIV seroconversion, CD4 count recovers to a set point, then falls gradually over 5 0 years. The coloured boxes schematically indicate causes of diarrhoea at different stages of HIV infection based on CD4 + T-lymphocyte count (blue line). The black dotted line indicates the impact of starting ART on CD4 count and the overlap between different categories after starting ART highlights the potential diagnostic difficulty at that time. has been considered an AIDS defining illness since 1985, 14, 15 and advanced HIV-disease is associated with a fold increased risk of invasive and multisite Salmonella infections. 16 Diarrhoea may be a less prominent feature of Salmonella infection in the setting of HIV. 11 Campylobacter jejuni is another organism commonly associated with diarrhoea in immunocompetent individuals which is an important cause of invasive disease and morbidity and mortality in HIV-infected individuals. The average incidence of Campylobacter among patients with AIDS has been found to be 39 times higher than in noninfected people, 13 furthermore HIV-infected individuals are much more likely to have debilitating disease requiring prolonged courses of antimicrobials and in one series the mortality of invasive disease was 33%. 12 Other species of this genus have also been implicated in diarrhoea in HIV. Other bacterial pathogens recognised to cause diarrhoea more frequently in HIV-infected patients include Escherichia coli, Shigella sp and Clostridium difficile. One study of trends in the aetiology of diarrhoea proposed that C. difficile is the most common cause of diarrhoea in HIV-infected adults in the US. 17 Lymphogranuloma venereum (LGV), caused by serovars L1 L3 of Chlamydia trachomatis, is endemic in Africa and the Carribean, and was rare in industrialised countries prior to It is currently re-emerging as a sexually transmitted infection among men who have sex with men (MSM), and HIV is a risk factor for susceptibility. WhilE genital LGV causes painful groin lymphadenopathy, gut mucosal infection can cause an ulcerative rectocolitis, and adenopathy of the deep nodes which drain the rectum may go unnoticed until they coalesce to form a bubo, which may rupture and fistulate. The clinical picture and histology may both mimic Crohn s disease and clinicians must be alert to the potential for misdiagnosis and mistreatment in this setting. It is likely that depletion of mucosal CD4 cells plays a critical role 18, 19 is susceptibility to LGV in HIV. Mycobacterial infection The likelihood of developing extra-pulmonary and disseminated infections with Mycobacterium tuberculosis and nontuberculous mycobacteria increases as HIV-associated immunosuppression progresses. Gastrointestinal infection with numerous species of Mycobacteria may occur in HIV. Both Mycobacterium tuberculosis and nontuberculous mycobacterial infection may present with 20, 21 diarrhoea. While diarrhoea is a relatively uncom- Aliment Pharmacol Ther 2011; 34:

6 N. A. Feasey et al. mon symptom of tuberculosis, it is more commonly a feature of disseminated infection with members of the Mycobacterium avium complex (MAC). Disseminated MAC infection occurs in advanced HIV and is frequently associated with diarrhoea, which was reported to be symptom in 17% of cases in one series. 22 Parasitic infection Numerous parasitic infections are known to cause diarrhoea in association with HIV. These include parasites previously described to have pathogenic potential in HIV negative patients (Giardia lamblia, Entamoeba histolytica, Blastocystis hominis, Strongyloides stercoralis and other soil transmitted helminths) and a number of parasites either newly discovered or not previously thought to have significant pathogenic potential, including Isospora belli, Cryptosporidium parvum, Cyclospora cayetanensis, and microsporidia particularly Enterocytozoon bienneusi and Encephalocytozoon intestinalis. These organisms have subsequently been identified as pathogens in otherwise healthy people. The first three are intestinal spore forming protozoa which cause intracellular infection and which can lead to severe intestinal injury and prolonged diarrhoea in advanced HIV, 23 while microsporidia have recently been reclassified as fungi. While some studies have linked parasitic infection with progressive immunosuppression, 24 others have questioned this association and suggested that diarrhoeal infections aggregate in HIV-infected individuals irrespective of CD4 count. 6 Certainly risk factors for exposure to parasitic infection, particularly socio-economic status and access to safe water and adequate sanitary facilities need to be considered when assessing an HIV-infected patient with diarrhoea. Viral infection A number of viruses have been implicated in the aetiology of diarrhoea in HIV-infected patients and the list has grown and changed as advances have been made in diagnostic virology. One of the first viral OIs to be listed as an AIDS defining illness was Cytomegalovirus (CMV). 25 CMV affects multiple organs in end stage HIV and in the GIT can cause colitis. The hallmark is diarrhoea which may be bloody and accompanied by weight loss, fever and abdominal pain. In early and pre-art cases series, CMV was a cause of approximately 15% of HIV associated diarrhoea. 26 The risk of CMV disease in HIV is at its greatest as the CD4 count falls below L, consequently CMV related disease has rapidly declined with the roll out of ART. 27 As with protozoal OIs, the list of viral infections associated with diarrhoea has grown substantially and now includes astrovirus, picobirnavirus, caliciviruses (both norovius and sapovirus) and adenoviruses. 28 While these viruses have been found significantly more frequently in the faeces of patients with both HIV and diarrhoea than in that of patients with HIV alone, causality has yet to be proven for all of them, particularly picobirnavirus. 28 Diarrhoea is also a well documented feature of HIV 29, 30 seroconversion illness itself. This is important to recognise as a combined antibody antigen HIV test may be negative during a seroconversion illness and if this diagnosis is suspected, the HIV test should be repeated 12 weeks after the initial test. Fungi Candida species are frequently isolated from the stool of HIV-infected patients 31 and have been implicated in antibiotic associated diarrhoea; 32 however, their role in the aetiology of diarrhoea remains unclear and further studies are needed into the role of yeasts in HIV-associated diarrhoea. Systemic dimorphic fungal infection can affect the gastrointestinal tract causing diarrhoea, for example disseminated infection with Histoplasmosis. 33 PATHOGEN-NEGATIVE DIARRHOEA The concept of pathogen-negative diarrhoea has evolved as the understanding of the breadth of OIs which cause diarrhoea has evolved. One study of patients classified as having pathogen-negative diarrhoea on entry to the study observed that in the majority of the more severe cases, an infectious cause was ultimately identified, 34 furthermore this study preceded the first reports of intestinal microsporidiosis as a cause of diarrhoea in HIV. 35 The hunt for novel infectious causes of enteropathy in HIV-infected patients continues. The role of HIV itself Despite this, it is clear that there are changes in the bowel attributable to HIV disease itself, which have important functional significance. Massive and progressive depletion of gastrointestinal effector memory CD4 + T lymphocytes is seen early in the course of HIV disease, and the simian model disease SIV. 36 The suggested mechanisms are direct infection of cells and bystander cell death. One of the most important consequences of this loss of gut mucosal CD4 cells is a failure to maintain the epithelial barrier function of the gut mucosa. 37 This mucosal damage enables microbial products to translocate across the bowel. LPS levels in both HIV and SIV have been found to be elevated and are 592 Aliment Pharmacol Ther 2011; 34:

7 Review: diarrhoea in HIV-positive patients temporarily reduced following neomycin treatment. 38 Translocated microbial products such as LPS, peptidoglycan and viral genomes may cause chronic gastrointestinal and systemic immune activation through stimulation of the innate immune system via Toll-like receptors. The resultant activated T-cells in turn are a further target for HIV, thus driving a vicious circle in the immunopathogenesis of HIV disease. 39, 40 The impact of HIV infection of the gut mucosa may therefore extend to influence overall progression of the disease systemically. These changes, however, also have significant functional consequences for the gut itself and also may be linked to the longstanding observations that there is a jejunal enteropathy termed HIV enteropathy, associated with mild villous atrophy and crypt hyperplasia Increased permeability and decreased absorption for sugars, vitamin B12 and bile have been described, even in the absence of detectable opportunistic infections, associated with chronic diarrhoea and malnutrition in HIV A third subset of T-lymphocytes has recently been discovered and characterised, which act through IL-17 to coordinate gut mucosal protection against infection. The loss of the TH17 subset of CD4 cells from the gut mucosa is thought to be particularly important during HIV 49 and in addition to the consequences for HIV disease progression described above, the loss of IL- 17-producing T cells has been shown to permit invasion and dissemination of nontyphoidal Salmonella from the gut in an SIV model. 50 Another suggested mechanism for HIV-related diarrhoea has been rapid intestinal transit due to damage to the autonomic nervous system; HIV is known to be neurotropic and a generalised autonomic neuropathy in advanced HIV is well described. 51 Increased transit time, however, does not correlate well with symptomatic diarrhoea. 45 HIV-associated inflammatory bowel disease, which has been defined as a non-infectious colitis refractory to standard treatment for inflammatory bowel disease is characterised by colitis 52 or caecitis (typhlitis) 53 and may also cause pathogen-negative diarrhoea. HIV-associated malignancy Human immunodeficiency virus-associated gastrointestinal malignancies may also present with pathogen-negative diarrhoea. 4 Non-Hodgkin B-cell lymphoma and Kaposi sarcoma are both AIDS-defining and are considered noninfectious, although their pathogenesis is ultimately related to oncogenic herpes viruses such as EBV and HHV8. Non-Hodgkin lymphomas (NHL) are fold increased among HIV-infected patients, commonly EBVrelated, and the categories most likely to affect the GI tract are Burkitt and Burkitt-like lymphomas 54, 55 and diffuse large B-cell lymphomas (DLBCL), which frequently present with extra-nodal involvement including of the GI tract, reflected by a predominance of gastrointestinal symptoms including diarrhoea. 56 Primary effusion lymphoma (PEL) is known to be HIV-related and an extracavitary, solid variant has recently been described which commonly affects the gastrointestinal tract and is HHV8-associated, with frequent EBV co-infection. 57 Hodgkin lymphoma is also 10-fold over-represented in HIV, although it is not AIDS-defining and its incidence in HIV has a nonlinear relationship with CD4 count and disease stage. 58 Cases present with advanced disease, extranodal disease and B symptoms, but not typically with diarrhoea or luminal GI disease. 57 The importance of the GI-related non-aids defining malignancies Hodgkin Lymphoma and anal carcinoma is increasing with the advent of HAART as patients are living longer. Kaposi sarcoma, caused by HHV8, is AIDS-defining and is a multifocal disease which very frequently involves the GI sub-mucosa. While GI involvement is often 59, 60 asymptomatic, Kaposi s may present with diarrhoea, GI bleeding (since it is a very vascular tumour), perforation, intussusception or obstruction. Pancreatic disease Human immunodeficiency virus infection may have multiple effects impairing exocrine pancreatic action, which in turn may contribute to chronic diarrhoea through impaired fat absorption. Factors associated with pancreatic disease include OIs, viral hepatits, HIV itself and ART, 61 although the principal culprit, didanosine, is rarely used now. One study found measurement of faecal elastase to assess pancreatic exocrine insufficiency to enable treatment with oral pancreatic enzyme therapy to be useful in the management of chronic diarrhoea. 62 Antiretroviral therapy as a cause of diarrhoea In 1987, Zidovudine (AZT) became the first pharmacological agent with proven efficacy against HIV. 63 In the late 1990s, combination ART became the standard of care to combat the rapid emergence of drug-resistance and it has been so successful that patients diagnosed early in the course of HIV infection can expect a near normal lifespan. 64 Multiple classes of ARVs are now available; however, these agents are not without side effect and diarrhoea is a common consequence of ART which may be severe enough to lead to discontinuation of ARVs. 65 While diarrhoea has been associated with all three main classes of ARVs; nucleoside reverse transcrip- Aliment Pharmacol Ther 2011; 34:

8 N. A. Feasey et al. tase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs), perhaps the most problematic agents are the PIs, particularly ritonavir, 66 which is used to boost levels of other PIs. 67 The dosage of ritonavir and dosing schedules of PIs is a subject of major interest. 68 INVESTIGATION An algorithmic approach to investigation and management of chronic diarrhoea in HIV is shown in Figure 2. To guide management, an accurate history concerning the patient s HIV, their treatment history and their professional and recreational exposure to pathogens and their travel history should be sought. All of the pathogens listed are transmitted by the faecal-oral route and are all potentially sexually transmitted. This information is equally important for clinicians and medical scientists considering which tests to perform. Additional features of the history and examination may help distinguish between small or large-bowel diarrhoea, and the possibility of complications. Although molecular diagnostics are predicted to enhance the sensitivity of investigations in the future, the majority of first-line clinical diagnostic tests routinely available are still based on microscopy and culture. Microbiological investigation Upon making a diagnosis of HIV, the most basic investigations necessary are a plasma CD4 count and HIV viral load (see Figure 2). The CD4 count will help to assess the degree of immunosuppression and thus clarify the spectrum of OIs to which the patient susceptible. The viral load is the most useful parameter of response to ARVs and in early treatment failure will increase before the CD4 count starts to decline. Initial clinical assessment including: Severity Drug history CD4 count and HIV Viral Load Stool examination: 3 samples over 10 different days Microscopy for ova, cysts & parasites (ZN stain, trichrome stain) Bacterial culture C. difficile screen Specific virology and protozoal PCR Empirical or specific treatment for: Infectious agents Start or optimise ARVs to: control VL, minimise drug side effect Review all other drugs, withdraw suspect drugs Pathogen negative diarrhoea? Flexible sigmoidoscopy: Biopsies for histology, standard and mycobacterial culture and CMV PCR Colonoscopy with terminal ileoscopy (or consider gastroscopy) Cross sectional imaging (malignancy, disease extent, complications, tissue biopsy) consider : double contrast upper GI barium study consider : complete TB diagnostic work-up Specific treatment for: Additional infectious agents identified HIV-associated malignancies Mycobacterial disease Supportive management Antimotility agents, adsorbents, cholestyramine, octreotide, etc Figure 2 Algorithm showing the management approach to the HIV patient with diarrhoea. 594 Aliment Pharmacol Ther 2011; 34:

9 Review: diarrhoea in HIV-positive patients Investigation of faeces Microbiological investigation of faeces should be the first investigation of diarrhoea. Different specimens provide different challenges to a diagnostic microbiology laboratory; faecal culture is made challenging by the difficulty of ensuring that the pathogen or pathogens among a diverse array of bacteria is identified. A faecal sample should be collected and submitted soon as possible after the onset of symptoms. While a 1 2 g specimen is sufficient for routine culture, more is required for the array of tests which may be necessary in the context of HIV and diarrhoea. Specimens of faeces should be transported to the laboratory and processed as soon as possible, because a number of important pathogens such as Shigella species may not survive the ph changes that occur in faeces specimens which are not promptly delivered to the laboratory, even if refrigerated. 69 Three samples over no more than a 10 day period are recommended for detection of parasites, although more may be necessary, especially if Giardia is suspected. No more than one specimen per day should be submitted as shedding of ova and cysts tends to be intermittent. 70 Once received by a diagnostic laboratory, specimen processing depends on the clinical context, but should include culture on a media which favours selection of Salmonella sp and Shigella sp and a second which selects for Campylobacter sp. Consideration should be given to testing for Clostridium difficile toxins A and B. Recovery of mycobacteria from stool is uncommon therefore mycobacterial stool culture is not recommended. 69 Stool should be examined using direct microscopy for the ova and cysts of protozoal parasites; however, a screen for Cryptosporidia, Cyclospora, Isospora and microsporidia requires a specific request as these organisms require specific stains. A modified acid fast stain is used to look for the oocysts of cryptosporidia, isospora and cyclospora, although the sensitivity is unknown and operator dependant. Examining multiple specimens increases sensitivity. 23 Diagnosis of microsporidia is also challenging, in part because their size (1 2 lm) makes them difficult to differentiate from faecal debris by light microscopy. 71 Improved methods include microscopy following staining with modified trichrome stain 72 with or without a chemofluorescence brightener such as calcoflour white; however, the gold standard test remains transmission electron microscopy (TEM) on small bowel biopsy specimens. Other methods include antigen and antibody based detection methods and nucleic acid amplification techniques. 71 Nucleic acid amplification tests are increasingly used in the diagnosis of sexually acquired infection. Since 2005 several such tests have become available for the diagnosis of LGV from anal swabs. The clinician must consider the diagnosis of LGV to make the diagnosis. Virology Diagnosis of the viral infections which cause diarrhoea is complex and species specific. While TEM (performed on tissue) and viral culture enable the identification of new viruses and viruses not expected in a given clinical context (i.e. non-enteric adenoviruses causing diarrhoea in HIV positive patients), the skills required for these techniques are rarely used outside of reference laboratories. Increasingly, viral infections are diagnosed using enzyme-immunoassay (EIA), latex agglutination kits or polymerase chain reaction (PCR) performed on stool, blood or tissue. In the context of CMV, assays for CMV DNA or antigen in blood are superior to culture for documenting viraemia 73 and few UK laboratories use CMV culture. Further prospective studies are required to determine whether PCR of blood or tissue is the most sensitive assay for diagnosing intestinal CMV, 74 however histology gives the best indication of disease severity. The rapid reduction in the cost of whole genome sequencing may make mass sequencing a viable diagnostic option in the near future. This approach will also enable the discovery of novel viruses. Other microbiology In addition to stool samples, blood should be taken for culture from febrile or septic patients and consideration should be given to mycobacterial blood culture. If TB is suspected, alternative microbiological specimens should be sought including mucosal biopsy, lymph node tissue or ascites for histology and culture, combined with radiological evidence of TB, including a chest X-Ray in all patients ( The role of rapid PCR-based diagnostic tests for TB is likely to expand. Blood for specific serology, antigen testing or PCR may be useful; however, patients with advanced HIV may lose the ability to mount an antibody response to the point where serology is negative. Endoscopy There has been much debate about the usefulness or necessity for pan-endoscopy to investigate stoolnegative diarrhoea in HIV. Not all studies are directly comparable, since sensitivity clearly depends not only on the extent of examination, but on the associated microbiological methods used for both stool and biopsy material, which have improved over time. Geo- Aliment Pharmacol Ther 2011; 34:

10 N. A. Feasey et al. graphical location, disease stage, the underlying risk factor for HIV and the advent of HAART may also be confounders in these studies. Endoscopy yields an additional diagnosis in 30 70% of stool-negative cases, depending on methods and the completeness of study. Unsurprisingly, diagnostic yield is highest when there are worse symptoms, and at lower CD4 count. The commonest additional or new diagnoses uncovered by endoscopy are CMV colitis, microsporidiosis and giardia infection. There is a general consensus that 85 90% of cases of CMV colitis will be detected using 4, 34, flexible sigmoidoscopy and biopsy alone and flexible sigmoidoscopy is generally considered a necessary and adequate first-line assessment in stool-negative diarrhoea. There are, however, a smaller number of studies suggesting that proximally distributed CMV colitis or other colonic diagnoses may be missed and full colonoscopy (preferably with terminal ileoscopy) is warranted if severe or functionally debilitating symptoms persist. 26, 78 Although some studies have suggested that biopsy of the small bowel, either at duodenoscopy or terminal ileoscopy, is necessary to reliably diagnose microsporidiosis, 76 improved microbiological stool methods such as PCR or trichrome stain mean that the necessity for small bowel biopsy is now reduced. The high pick-up rate for microsporidiosis in the terminal ileum, combined with the detection of proximally distributed CMV colitis, means that colonoscopy with terminal ileoscopy is a logical second-line investigation and may obviate the need for upper GI endoscopy. The decreasing utility of upper GI endoscopy to diagnose pathogens in HIV is confirmed in other recent studies. 79 Radiology Radiology of opportunistic infections and inflammatory disease. Interpretation of diagnostic imaging of the HIV-infected patient presenting with diarrhoea can be challenging as the appearances are usually nonspecific. 80 The most common findings in infectious diarrhoea are of oedematous and ulcerated mucosa. The distribution and type of ulcers and the extent of disease when correlated with the degree of immunosupression can aid in narrowing the wide differential diagnosis of the various infectious pathogens, but endoscopic samples need to be obtained for histopathological or microbiological investigation to make a definitive diagnosis. 81, 82 Literature on the appearances of the bowel in patients with diarrhoea and HIV is sparse. Imaging of mucosal detail, such as the pattern and distribution of ulcers and oedema, is best seen in barium studies. Mucosal detail is not apparent on CT or MRI and the appearances of the bowel are not pathogen specific. CT or MRI scanning is undertaken in patients with more severe disease to assess disease distribution, potential complications, for staging tumours and to aid intervention. If these modalities are unavailable, ultrasound may demonstrate small and large bowel thickening. 83 While a tissue or microbiological diagnosis must be sought, imaging can suggest certain diagnoses. Tuberculosis commonly affects the ileocaecal region resulting in mural thickening of the terminal ileum and caecum. Skip areas in the small bowel may mimic Crohn s disease with luminal narrowing and proximal dilatation, but the presence of skip lesions with ileocaecal involvement is strongly suggestive of TB. Necrotic mesenteric lymphadenopathy can be seen on CT and is also suggestive of TB infection. 84 Advanced disease results in the classic appearance of a conical small caecum. Colonic involvement results in segmental ulcers, strictures and polypoid hypertrophic lesions. Mycobacterium avium affects the jejunum with thickening of the folds, but there is no ulcer as MAI is not associated with tissue destruction. Normal appearances are seen in 25% of infected patients undergoing CT. 85 Cytomegalovirus infection most commonly affects the colon and radiological appearances vary depending on the severity. Bowel wall thickening, ulcers and irregular folds are seen on barium studies and CT. With increasing severity of disease, large ulcers, nodular defects and pseudo-membranes may develop. Tumour like lesions may develop which may be indistinguishable from neoplasia. 86 Thrombosis secondary to vasculitis with subsequent ischaemia may result in penetrating ulcers and subsequent perforation. 87 Histoplasmosis also affects the colon, particularly the ascending colon. The thickening of the bowel and pericolonic inflammatory change can mimic carcinoma. 88 Human immunodeficiency virus-related typhlitis (caecitis) is localised inflammation of the caecum with symmetric wall thickening, pneumatosis and pericolonic inflammation. This can extend to involve the terminal ileum and ascending colon. 89 Diagnosis takes account of and is based on the entire clinical picture, rather than by imaging alone. CT imaging is particularly useful to exclude a perforation or abscess and to guide intervention. 90 Radiology of neoplastic lesions. The lesions of Kaposi sarcoma are submucosal in location and can affect any 596 Aliment Pharmacol Ther 2011; 34:

11 Review: diarrhoea in HIV-positive patients part of the gastrointestinal tract, most commonly the duodenum. Barium studies in the early stages may be negative as the lesions are submucosal and diagnosis may be more readily achieved endoscopically. When advanced, both barium studies and CT may demonstrate larger flat or polypoid submucosal masses with or without ulcers and associated fold thickening. Enhancing lymph nodes are seen commonly in patients with disseminated disease which may aid diagnosis. Otherwise, the lesions may mimic other neoplastic lesions such as carcinoma, metastases or lymphoma or infections. 91 Acquired immunodeficiency syndrome-related non- Hodgkins lymphoma (NHL) in HIV has been found to affect extra-nodal sites in 86% of abdominal CT scans, the commonest being the GI tract. 92 Primary B-cell lymphoma in HIV patients often affects the distal small bowel. Thickening of the distal ileum, mass like lesions, ulcers and aneurysmal dilatation may be seen on CT with extension of tumour into the adjacent mesentery and lymph nodes. Barium studies are nonspecific demonstrating polypoid mass lesions, ulcers and infiltrative change or nodularity. Intussusception and bowel obstruction may occur and the appearances may be indistinguishable from carcinoma. 93 The patterns and distribution of intestinal findings on CT imaging of small bowel NHL are not distinguishable from those seen in HIV-uninfected cases. 94 Other investigations A diagnosis of Mycobacterium tuberculosis (MTB) complex can be inferred from a localised immune reaction to intradermal injection of Mycobacterial purified protein derivative (PPD, the tuberculin test). More sophisticated ex-vivo tests based on detection of interferon gamma release in response to two antigens specific to MTB (and which are not found in the BCG vaccine) have recently been introduced. Interferon gamma release assays (IGRAs) may be more sensitive than intradermal PPD in HIVinfected adults. 95 More work needs to be carried out to define the role of IGRAs in the diagnosis of extrapulmonary TB in HIV-infected adults and no studies have focused on the use of IGRAs in intestinal tuberculosis. Despite this, a positive tuberculin-test or IGRA may be of value in supporting a diagnosis of MTB, 96 while a negative result should be interpreted with caution. MANAGEMENT AND OUTCOMES Treatment of infectious diarrhoea by aetiology The first steps in managing diarrhoea in the context of HIV are the same as those taken in managing any acute diarrhoea; to evaluate which pathogens the patient is at risk of by taking a careful history and to assess and manage dehydration, although known HIV infection should lower the threshold for using antimicrobial therapy. There is increasing, but geographically heterogeneous resistance to multiple antimicrobials among enteric pathogens, making recommendation of an empirical antimicrobial unrealistic, instead expert local advice should be sought or local guidelines consulted in the management of the critically ill patient. Ultimately, identification of specific organisms by culture will enable antimicrobial susceptibility testing to be performed. Lymphogranuloma venereum proctocolitis caused by Chlamydia trachomatis requires a prolonged course of therapy. Either doxycycline or a macrolide is recommended, although there are no clinical trials to guide the use of macrolides. There is also interest in fluoroquinolones, although again, trial data are lacking. Mycobacterial infection Gastrointestinal infection with M. tuberculosis is treated in the same fashion as pulmonary tuberculosis, initially using a four drug regimen involving rifampicin, isoniazid, pyrazinamide and ethambutol dosed according to patient weight for 2 months followed by a further 4 months of rifampicin and isoniazid. 97 Following culture of M. tuberculosis, sensitivity testing should be performed to refine the antituberculous regimen if resistance is detected. Treatment of MAI consists of a macrolide, rifamycin and ethambutol given three times weekly for noncavitary disease and daily with or without an aminoglycoside for cavitary disease. 98 Antimycobacterial therapy for MAI should not be stopped until immune reconstitution with ART has occurred. 99 Protozoal and fungal infections Despite a drive to diagnose HIV earlier and the introduction of ART, protozoal infections continue to cause diarrhoeal disease in HIV-infected patients and they frequently present a therapeutic challenge. The drugs of choice for Giardiasis are metronidazole (2 g day for 3 days) or tinidazole (2 g once), with a cure rate of %. 100 Nitazoxanide is an alternative with an 81% success rate. 101 There are inadequate and conflicting trials of specific therapy for cryptosporidiosis with both nitazoxanide and paroromycin. A recent Cochrane meta-analysis of seven trials including 130 adults with HIV concluded that although nitaxozanide reduces the load of parasites and may be useful in immunocompetent individuals, the effect was not significant for HIV-infected patients. Despite this, Aliment Pharmacol Ther 2011; 34:

12 N. A. Feasey et al. the use of nitaxozanide should be considered in very sick HIV-infected patients with Cryptosporidiosis. 102 Trials of paroromycin have included even fewer HIV-infected patients and the same meta-analysis found no statistically significant effect. Further trials are unquestionably warranted; however, the mainstay of treatment is effective immune reconstitution with ART The treatment of Isoporiasis and Cyclospora is more straightforward. Both pathogens are susceptible to cotrimoxazole, which may resolve symptoms in up to 100% of patients. 106 In the case of intolerance or allergy to sulphonamides, ciprofloxacin may be used, although it is less effective, resolving only 87% cases. 106 The main specific therapy for microsporidiosis is albendazole. While Encephalitozoon intestinalis responds well to albendazole 400 mg b.d. for 3 weeks, which caused clinical resolution and parasite clearance in 4 4 patients in one study, 107 Enterocytozoon bieneusi does not. Albendazole should still be tried, but supportive therapy with fluids and early initiation of ART are crucial. As with cryptosporidiosis, immune reconstitution can lead to complete clearance of microsporidia. 103 Anti-viral therapy Specific anti-viral therapy is available for CMV colitis using IV ganciclovir or oral valganciclovir. Alternatively foscarnet and cidofovir have been approved, but there are no clinical trials to support a specific therapy for CMV colitis. Immune reconstitution is an essential component of treating CMV disease. Prophylactic therapy Cotrimoxazole remains a useful prophylactic agent in HIV-infected patients. While in the developed world, it is primarily used to prophylax against PCP and toxoplasma encephalitis in the profoundly immunosuppressed (plasma CD4 count less than L), it will also prevent isospora diarrhoea. 108 Cotrimoxazole is used much earlier in the course of HIV in developing countries (plasma CD4 count less than L). This is in part due to its prophylactic role against malaria, but it also prevents diarrhoea. 109 Secondary prophylaxis is recommended by the CDC for the prevention of recurrent nontyphoid Salmonella sepsis, but not for other enteric bacterial pathogens. 108 Antiretroviral therapy The treatment of HIV was revolutionised initially by the introduction of Zidovudine AZT and subsequently by combination ART. Now multiple classes of ARVs are available and what was once a terminal illness should now be regarded as a chronic, treatable medical disorder. Current regimens for ARV naive patients are well tolerated with low pill burdens. In the early days of HIV therapy, the consensus was that treatment was unnecessary until the CD4 count fell to around L. This decision was based on the perceived risk of OIs at CD4 counts of L or less, the severe side effects of early regimens and the cost of ART. Current guidelines recommend that ART should start before the CD4 count falls below L, 110 with many experts advocating even earlier treatment, 111 although this remains controversial. Antiretroviral therapy rapidly reduces plasma HIV viral load enabling the CD4 + T-lymphocyte population to reconstitute and there is good evidence that this reduces chronic diarrhoea in HIV-infected individuals, often very rapidly. 112 Sampling of gut tissue reveals a rapid fall in viral load, 112 which suggest that the virus has a central role in HIV-associated diarrhoea. There is robust evidence of both a general reduction in gastrointestinal OIs 113 with the introduction of ART and of improvement in the outcome from infection with specific OIs. Infections caused by pathogens which have no specific treatment may resolve following the introduction of ART including cryptosporidiosis and microsporidiosis, 103 while the treatment of other OIs for which specific therapy is available (i.e. CMV colitis) is enhanced by the introduction of ART. 27 Lastly, recurrence of invasive bacterial infections such as Salmonellosis has been shown to cease following introduction of ART. 114 Despite the clinical improvement that is frequently seen, the picture at a GI cellular level is more complex. The completeness of gastrointestinal reconstitution is controversial with some studies showing good CD4 T- cell repletion, while others have suggested that it is both poor and much slower than the improvement in plasma CD4 count 40 and that in the long term, patients with poor GI CD4 reconstitution have ongoing immune activation. One possible explanation for this is the observation that some GI CD4 cells have been observed to produce HIV years after initiation of ART. 115, 116 A second possibility is that fibrotic damage to GI lymphoid tissue prior to initiation of ART may be such that the ability to replace CD4 T-cells in the GIT is permanently impaired 40 and early initiation of ART certainly fosters a 115, 116 more complete CD4 reconstitution in the GIT. Although gut mucosal CD4 depletion does not completely reconstitute following antiretroviral therapy, possibly because of the deposition of collagen in GALT, Aliment Pharmacol Ther 2011; 34:

13 Review: diarrhoea in HIV-positive patients many of the functional consequences, including permeability defects, are measurably reversed. 118 Symptomatic treatment of chronic diarrhoea Chronic diarrhoea in Western populations is now increasingly rare due to the introduction of ART early in the course of HIV infection. Despite exhaustive investigation of diarrhoea and initiation of ART, diarrhoea may persist or even result from HIV therapy and empirical treatment may be required. Antimotility agents (loperamide, diphenoxylate and codeine) and adsorbents (bismuth subsalicylate, kaolin pectin and attapulgite) have anecdotally been found to be useful. Antimotility agents increase gut transit time, giving more time for fluid reabsorption and while narcotic analgesics should be avoided because of their addictive nature, loperamide and diphenoxylate may be useful, although studies are lacking. A recent Cochrane review highlighted the lack of evidence for these agents and the need for further studies. 119 Cholestyramine may be beneficial if diarrhoea is caused by malabsorption of bile salts. 120 Other measures studied include zinc or other micronutrient supplementation, mesalazine (mesalamine) and curcumin. Randomised controlled trials of zinc supplementation 121 and mesalazine 122 in adults revealed no benefit, while a small study of the turmeric extract curcumin revealed a benefit in five of six patients. 123 A Cochrane review has concluded that micronutrient supplementation offers no reduction in morbidity (including diarrhoea) or mortality among HIV-infected adults. 124 One more recent study of broader micronutrient supplementation did not result in significant reduction in diarrhoea, although there was a very modest reduction in severe infectious diarrhoea. 125 Supplementation with vitamin A and zinc, however, has failed to significantly reduce gut permeability or markers of microbial translocation. 126 Although octreotide has been used for symptomatic control of diarrhoea in HIV enteropathy, the results of trials are inconsistent In the case of HIV-related colitis, thalidomide has been used with success in individual patients, 52 but randomised controlled trials are lacking. Typhlitis or caecitis has been successfully managed with bowel rest, IV fluids and broad spectrum antibiotics. 130 Discussion of chemotherapy for mitotic lesions is beyond the scope of this review, but the expert opinion of an oncologist should be sought in the case of discovery of an HIV-related malignancy as the cause of diarrhoea and it should be remembered that tight control of HIV viraemia forms an essential part of the treatment of these cancers. CONCLUSIONS Human immunodeficiency virus infection impacts upon the gastrointestinal tract in a variety of ways and there is an incomplete understanding of the mechanisms by which it does this. The aetiology of diarrhoea in HIV infection is diverse and includes the direct effects of the virus upon the GIT, infection with both obligate and opportunistic enteropathogens, malignant and other non-infectious causes and as a consequence of anti-viral therapy. In addition, HIV-infected patients are still susceptible to unrelated but common causes of diarrhoea including irritable bowel disease and drug side effects. A multidisciplinary approach to diagnosis and management is therefore best practice and in the best interests of the patient. Faecal microbiology remains the principal and firstline investigation for diarrhoea in HIV-infected patients. Tests typically available routinely include microscopy, culture and enzyme immunoassays. In recent years, the cost of genome sequencing technology has plummeted and its increasing availability is revolutionising microbiology. Failure to detect pathogens by currently available diagnostic microbiology may lead to a need for complex radiology or the judicious use of endoscopy and tissue biopsy. Flexible sigmoidoscopy is generally acknowledged to be an appropriate first-line investigation in stool-negative cases, and full colonoscopy with visualisation and biopsy of the terminal ileum, rather than gastroduodenoscopy is generally a reasonable second-line endoscopic investigation. Radiological findings are often nonspecific but useful to detect disease severity, distribution and complications, and some HIV-related malignancies. While current research suggests that people diagnosed with HIV infection today might expect to live a normal life if adherent to their therapy, ARVs may themselves cause diarrhoea and further research is needed to optimise drug dosage, particularly with protease inhibitors. A good evidence-base for symptomatic management of HIV-related diarrhoea is also lacking. The greatest burden of HIV infection falls on Sub-Saharan African countries where there are limited diagnostic facilities. National and regional prevalence studies of enteropathogens are needed, both to inform regional and national treatment strategies and to highlight the true burden of disease attributable to neglected or newly discovered pathogens. The intestinal parasites also number among the neglected tropical diseases and new therapies for these pathogens are urgently needed for both HIVinfected and uninfected patients. Aliment Pharmacol Ther 2011; 34: