Prostacyclin in diarrhoea-associated haemolytic uraemic syndrome

The role of prostacyclin (PGI₂) in the pathogenesis of haemolytic uraemic syndrome (HUS) is controversial. In part, confusion has been caused by failure to distinguish between two main sub-types of the syndrome: extrinsic, diarrhoea-associated HUS (D+ HUS), usually caused by infection with verocytotoxin-producingEscherichia coli orShigella dysenteriae, and the heterogeneous group of non-prodromal forms where intrinsic factors predominate (D– HUS). This paper critically reviews data confined to D+ HUS. Two methods have been used to assess PGI₂ synthesis; the generation of PGI₂ from endothelium in the presence of HUS plasma in vitro and the measurement of stable metabolites in body fluids. No concensus could be reached with regard to the former. The reported increase of PGI₂ stable metabolites in plasma may represent reduced clearance or increased carriage by plasma lipids. Apparent differences between studies of urinary excretion of PGI₂ metabolites may reflect the way excretion was expressed. If the metabolite concentration is factored for urinary creatinine, it appears that renal excretion and thus renal synthesis of PGI₂ is reduced. However, these are insufficient data on which to attribute the pathogenesis of D+ HUS to disordered PGI₂ metabolism.Presented at the Festschrift for Professor R. H. R. White on March 6, 1992, Birmingham, UK     

Cluster of cases of haemolytic uraemic syndrome due to unpasteurised cheese

A cluster of four patients (1 girl, 3 boys) from a French village (2,000 inhabitants) had acute haemolytic uraemic syndrome (HUS) between March 1992 and May 1993. All had prodromes with fever and diarrhoea, then acute renal failure, anaemia, schistocytosis and thrombocytopenia. Peritoneal dialysis was carried out in three children (duration 3–12 days). The verotoxin VT2 gene was identified by polymerase chain reaction in the stools of two children. Some days prior to the diarrhoea, all children had eaten a cheese made with unpasteurised mixed cows' and goats' milk from the same farm. A case control study showed that the occurrence of HUS was linked to the consumption of this milk product (P=0.006). The VT 2 gene was isolated from the cheese and from the stools of goats and cows from the farm, but not from the stools of farm employees.     

The polymorphonuclear leucocyte count in childhood haemolytic uraemic syndrome

Review of data from 79 children with the haemolytic uraemic syndrome (HUS) showed that the polymorphonuclear leucocyte (PMN) count at presentation in childhood HUS predicts outcome. Logistic regression analysis of several features at presentation identified only the PMN count and the presence of a diarrhoeal prodrome as having a significant effect on the outcome (P<0.01 andP<0.001 respectively). The geometric mean PMN count was significantly raised in 70 children who had typical HUS following a diarrhoeal prodrome (D+cases) compared with that of 9 children who had atypical disease without diarrhoea (D-cases) (t-test on log-transformed data,P<0.005). Fifty-seven children with D+HUS who recovered completely had a significantly lower geometric mean PMN count than D+cases with a bad outcome (P<0.001). Four of these patients, who died in the acute stage of the disease, had a significantly higher mean count than the rest of the D+patients (P<0.001). Multiple regression analysis demonstrated that the PMN count in D+cases was not significantly influenced by haemoglobin concentration, platelet count, length of the prodrome, or the administration of antibiotics in the prodromal period. A high PMN count at presentation in D+HUS indicates a poor prognosis. The data emphasise the heterogeneity of HUS and suggest that PMN participate in the pathogenesis of the disorder in typical D + cases but not in atypical D- cases.     

Serum proteins in the haemolytic uraemic syndrome

In 122 patients with the haemolytic uraemic syndrome (HUS), serum proteins were analysed in the acute phase of the disease (n = 122) and 6 weeks (n = 57) and 6 months (n = 84) later. Total serum protein levels were significantly lower on admission than 6 weeks and 6 months later (P < 0.0001). The same was true for median values of serum albumin (P < 0.0001), ₂-globulins (P < 0.0001) and -globulins (P < 0.001). There was no difference in -globulins, whereas the ₁-globulins were significantly higher in the acute phase (P < 0.0001). There was a significant positive correlation between age and total protein and -globulin levels. Serum total protein and albumin levels displayed a significant positive correlation with serum sodium levels and a significant negative correlation with urinary protein excretion. Patients with oligoanuria had significantly lower serum albumin and significantly higher ₁-globulin levels than those with preserved urine production. Marked differences were observed between patients with (D+) and patients without (D–) prodromal diarrhoea. In D(–) HUS, only albumin and total protein levels were lower on admission, but to a lesser degree than in D(+) HUS. Serum at-globulin levels were significantly higher and (₂-globulin levels significantly lower in D(+) HUS than D(–) HUS. In the D(+) subgroup of patients, by far the largest, there was a significant positive correlation between serum albumin and total protein on the one hand and the duration of the prodrome on the other. Patients with bloody stools had significantly lower serum albumin and total protein levels than those without. Faecal al-antitrypsin concentration measured in 12 HUS patients on admission was found to be significantly increased compared with age-matched controls. This study confirms the existence of hypoproteinaemia in childhood HUS and indicates that intestinal protein loss is an important, albeit not the only, physiopathological mechanism.     

Plasma renin activity in haemolytic uraemic syndrome

Plasma renin activity (PRA) was measured in 50 consecutive patients (aged 4 months to 12 years) admitted during the acute phase of the haemolytic uraemic syndrome (HUS). Blood samples were taken as soon as the diagnosis was made and prior to any diuretic, anti-hypertensive or dialysis treatment. Prodromal diarrhoea was present in all but 3 patients, 17 were anuric and 12 were oliguric. PRA ranged from 0.3 to 24.2 ng/ml per hour and was low compared with values in normal infants and children: in 13 HUS patients PRA was above the median and in 37 it was below the median. PRA was significantly, independently and inversely related to age. There was no correlation, however, with blood pressure, urine output, volume status and serum levels of sodium, potassium and creatinine. Moreover, no relationship was found between PRA and the course of the disease. Our findings do not support the idea that renin activation plays a role in the pathophysiology of the haemolytic uraemic syndrome.     

Clinico-pathological findings in diarrhoea-negative haemolytic uraemic syndrome

This is a retrospective, national clinico-pathological study of past and current patients with haemolytic uraemic syndrome not associated with diarrhoea (D– HUS). Thirty-four patients were analysed and notified by members of the British Association for Paediatric Nephrology in 1998–1999. There was a 2:1 excess of males. Ten presented in infancy. The aetiology included 5 patients with complement abnormalities, 2 patients with complications of pneumococcal infection, and 2 with malignancies. Parental consanguinity was noted in 6 patients. Five children died, 9 developed chronic renal failure, and 10 end-stage renal failure. Only 7 made full recoveries. With a single exception, the pathological findings were unlike the previously reported glomerular thrombosis that is characteristic of diarrhoea-associated HUS, or HUS complicating verocytotoxin-producing Escherichia coli infection. Early and late glomerulopathy could be distinguished. Arteriolar and arterial disease was observed in 8 and 7 patients, respectively. Arterial disease correlated with a poor outcome. The pathology of D– HUS is of prognostic value, but this study was not powered to identify specific aetiological/pathological correlations.This paper was written on behalf of the British Association for Paediatric Nephrology     

Oxidative damage of red blood cells in haemolytic uraemic syndrome

Changes in red blood cell (RBC) lipid peroxidation [measured by malonyl dialdehyde (MDA) concentration], glutathione (GSH) metabolism, antioxidant enzyme activities (catalase, superoxide dismutase, glutathione peroxidase) and haemoglobin (Hb) metabolites (metHb, carboxy Hb) were studied in six children with post-enteropathic (D+) haemolytic uraemic syndrome (HUS) and ten controls. The in vitro effect of hydrogen peroxide [acetyl-phenylhydrazine (APH) test] on GSH and Hb metabolism was also investigated. MDA levels were significantly higher and the antioxidant enzyme activities were lower in HUS patients than in the controls (P<0.01). The oxidised glutathione concentration was significantly higher in the patients than in the control children (26.3±12.6 vs. 10.9±1.8 nmol/g Hb. Percentage values of carboxy Hb and metHb were also higher in HUS (P<0.01). Incubation of RBC with APH induced a more pronounced decrease in the concentration of GSH (P<0.001) and a significant increase (P<0.01) in the level of metHb and carboxy Hb in the HUS patients. This suggests that there is reduced RBC GSH stability in HUS. Utilisation of GSH and antioxidant enzymes leads to increased Hb oxidation and haemolysis. The oxidative damage may have an important role in the pathogenesis of haemolytic anaemia in HUS.     

Neutrophil activation in the haemolytic uraemic syndrome: free and complexed elastase in plasma

There is evidence of neutrophil involvement in the pathogenesis of the haemolytic uraemic syndrome (HUS), and neutrophil release products are thought to cause endothelial cell damage. Elastase is the major lysosmal proteinase liberated by activated neutrophils. In this study we measured both free and complexed elastase. No free elastase activity could be detected in the plasma of patients with diarrhoea-associated (D+) HUS using a specific substrate. However, there was a marked increase in 1-antitrypsin (1-AT) complexed elastase as measured by a newly developed enzyme-linked immunosorbent assay not only in D+ HUS, but also in non-diarrhoea-associated (D-) HUS. This finding is independent of either a high polymorphonuclear leucocyte count or renal failure. This increase in bound elastase together with our sequential data which demonstrate raised 1-AT complexed elastase levels early in the disease process further support the theory that neutrophil activation is one of the key events in the pathophysiology of this disorder.     

Haemolytic uraemic syndrome and pseudomembranous colitis

Two cases of haemolytic uraemic syndrome (HUS) associated with pseudomembranous colitis (PMC) are described. The toxin ofClostridium difficile was detected post mortem in the stool of one patient and the other patient showed a good therapeutic response to oral vancomycin, an antibiotic with established efficacy in the management of PMC. When associated with HUS, PMC is probably an independent specific disease that, in common with many other infections, may activate HUS.     

The neutrophil oxidative burst in diarrhoea – associated haemolytic uraemic syndrome

. Neutrophil-mediated tissue damage has been implicated in the pathogenesis of diarrhoea-associated haemolytic uraemic syndrome (D+ HUS). This study evaluates priming and activation of the neutrophil oxidative burst in D+ HUS using chemiluminescent techniques. Peripheral blood neutrophils from 11 children with acute D+ HUS were examined. No difference was found in the oxidative burst of neutrophils from patients and controls. Serum elastase levels were measured in 8 patients and found to be significantly elevated. Although elastase results suggest neutrophil activation, chemiluminescence studies do not confirm this in the peripheral blood neutrophil. This does not support a significant role for circulating agents in priming and activating the peripheral blood neutrophil. Received August 17, 1995; received in revised form and accepted November 27, 1995     

Treatment of the childhood haemolytic uraemic syndrome with plasma

Seventy-nine children with haemolytic uraemic syndrome (mean age 28 months) were randomly assigned either to a group receiving plasma infusions (plasma group,n=39) or to a group treated conservatively (control group,n=40). The duration of haemolysis, thrombocytopenia and anuria was similar in the two groups. Serum creatinine levels were similar in the two groups at the 1-month follow-up but were higher in the control group at 3 months (plasma group 49±14, control group 66±28 mol/l;P<0.02) and at 6 months (plasma group 48±13, control group 63±21 mol/l;P<0.005). The prevalence of proteinuria was also higher in the control group at the 6-month follow-up (plasma group 17%, control group 46%;P<0.02). However differences were no longer significant after 1 year. Renal tissue was examined in 54 cases (plasma group,n=27; control group,n=27). Diffuse cortical necrosis was present in 7 cases in the control group but was absent in the plasma group (P<0.02). Taking into consideration the higher serum creatinine levels, the higher prevalence of proteinuria during the first 6 months of follow-up in the control group and the presence of diffuse cortical necrosis in this group compared with the plasma group, we conclude that plasma infusions should be regarded as beneficial. Further study is needed to determine which plasma fraction is involved.     

Haemolytic uraemic syndrome and the Thomsen Friedenreich antigen

In three children with haemolytic uraemic syndrome (HUS), evidence of red cell polyagglutinability due to Thomsen Friedenreich antigen (T-antigen) exposure was demonstrated. This was suspected after difficulties in ABO typing and was confirmed using specific antisera. Further supportive evidence included elevation of plasma sialic acid, alteration in red cell surface charge and evidence of T-antigen exposure in the renal biopsy specimen of one patient. Although involvement of this antigen in the pathogenesis of HUS has been associated with a high mortality, all three children have made a complete recovery. With early recognition and subsequent avoidance of plasma products, prognosis of this condition may be improved.     

Renal histopathology in fatal cases of diarrhoea-associated haemolytic uraemic syndrome

 Autopsy material was examined from British children dying early in the course of haemolytic uraemic syndrome (HUS). These presented after 1983, the period in which verocytotoxin-producing Escherichia coli (VTEC) infection was confirmed as the leading cause of diarrhoea-associated (D+HUS) in the United Kingdom. Of 18 cases referred for this study, 3 were found on review to have no history of a diarrhoeal prodrome (D-HUS). In the D+ patients, the median duration from onset of diarrhoea to death was 8 days (range 4–42 days). VTEC infection was confirmed in 6 cases. All had neutrophilia at presentation (median 21, range 15–49.8 × 10⁹/l). The 15 cases had uniform pathological features, consisting of glomerular thromboses and congested rather than ischaemic glomeruli. Arteriolar thromboses were common at the hilum of glomeruli and were sometimes also seen proximally, including in interlobular arteries. There were cortical infarcts in 5 cases with extensive thrombosis. Cases were demonstrated to have significantly greater numbers of neutrophils expressed per 100 glomeruli than controls, when counted using immunohistological stains to neutrophil elastase and CD15. This study showed uniformity of the renal changes in D+ HUS and gave further evidence of the importance of neutrophils in the pathogenesis of the disease. Received November 15, 1996; received in revised form February 25, 1997; accepted February 27, 1997     

Soluble circulating cell adhesion molecules in haemolytic uraemic syndrome

Plasma concentrations of soluble vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-selectin) and intercellular adhesion molecule-1 (sICAM-1) were measured by enzyme-linked immunosorbent assay in four groups of children. Group 1 consisted of 20 patients with acute diarrhoea-associated haemolytic uraemic syndrome (D+HUS), the aetiology of HUS being verocytotoxin-producingEscherichia coli infection in each case. Controls consisted of 11 patients who had previously had D+HUS (group 2), 12 with chronic renal failure (group 3) and 8 healthy controls (group 4). When compared with healthy controls, the acute D+HUS group had higher sVCAM-1 (median 1,875 ng/ml, range 1,200–6,450 ng/ml vs. 1,200 ng/ml, range 975–2,125 ng/ml), von Willebrand factor antigen, (1.9 U/ml, range 0.85–5.1 U/ml vs. 0.55 U/ml, range 0.3–1.57 U/ml), white cell count (WBC, 14.5×10⁹/l, range 7.8–43.1 10⁹/l vs. 8.9 10⁹/l, range 5.7–10.8 10⁹/l) and neutrophil count (PMN, 10.1×10⁹/l, range 4.3–26.5 10⁹/l vs. 4.3 10⁹/l, range 3.7–6.6 10⁹/l), allP<0.005, and sICAM-1 was reduced (230 ng/ml, range 130–340 ng/ml vs. 400 ng/ml, range 260–690 ng/ml),P<0.05. Within the acute D+HUS group there was a significant correlation between sICAM-1 and PMN (r=0.56,P<0.01). There was no correlation between any adhesion molecule and plasma creatinine or von Willebrand factor. Comparing the acute HUS group with children with chronic renal failure, WBC (P<0.001), PMN (P<0.01) and sVCAM-1 (P<0.01) were significantly elevated, but there was no difference between the von Willebrand factor (P=0.08) or the sICAM-1 (P>0.1). sVCAM-1 is elevated and sICAM-1 decreased in acute D+HUS. This pattern of altered adhesion molecule concentration is unlike that in adults with vasculitis and suggests that different endothelial regulatory factors are at play.     

Conversion of renal transplant recipients from cyclosporin (Neoral) to tacrolimus (Prograf) for haemolytic uraemic syndrome

Abstract Five patients with cyclosporin-related haemolytic uraemic syndrome (HUS) following cadaveric renal transplantation were converted from cyclosporin- to ta-crolimus-based immunosuppression. All patients had biochemical, haematological and biopsy evidence of HUS at the time of conversion. Four of the patients showed complete resolution of the syndrome within 1 week of conversion with normalisation of haemoglobin, platelets and lactate dehydrogenase levels. In the fifth patient renal function stabilised with slow resolution of the haematological and biochemical parameters. Four of the five patients are still taking tacrolimus, one having converted back to cyclosporin due to marked hair loss. We conclude that conversion to tacrolimus appears to be an effective treatment for cyclosporin-related HUS following renal transplantation.     

Haemolytic uraemic syndrome associated with faecal cytotoxin and verotoxin neutralizing antibodies

Forty-nine patients with a diagnosis of idiopathic haemolytic uraemic syndrome (HUS) were investigated to determine evidence of infection by verotoxin-producingEscherichia coli (VTEC). Free faecal cytotoxin active on Vero cells (VT) was detected in 15 out of 49 patients (31%). Seroconversion or high titres of VT-neutralizing antibodies were detected in 11 out of 18 patients (61%). The results of the present study suggest an association between HUS and infection by VTEC.     

Role of nitric oxide in a toxin-induced model of haemolytic uraemic syndrome

The role of nitric oxide in the pathogenesis of glomerular thrombotic microangiopathy was explored using an established rat model in which ricin with or without lipopolysaccharide induced glomerular thrombosis. Ricin alone caused a small rise in the plasma concentration of nitric oxide (control 9.2±0.7 μM, ricin 23.3±6.3 μM at 7 h). This increase occurred after the development of glomerular thrombosis. Nitric oxide synthase (NOS) activity in the kidney showed no significant change from control values (control 5.66±2.7 pmol/min per ml homogenate, ricin 7.52±1.8 pmol/min per ml homogenate, total activity). When ricin and lipopolysaccharide were administered together, calcium-independent NOS activity increased whereas calcium-dependent activity decreased (1.22±2.6 pmol/min per ml homogenate). The increase in calcium-independent NOS activity correlated with a high plasma concentration of interleukin-1β in the ricin plus lipopolysaccharide group (4,036.83±1,001.5 pg/ml). These data indicate that thrombus formation in a rat model of haemolytic uraemic syndrome is independent of the effects of nitric oxide. Received: 16 November 1999 / Revised: 16 March 2000 / Accepted: 20 March 2000