Hemolytic Uremic Syndrome

Abstract

Hemolytic uremic syndrome (HUS), a common cause of acute renal failure (ARF) in children, consists of triad of microangiopathic haemolytic anemia (MAHA), thrombocytopenia, and ARF. The aim of the present article is to have a recent overview of HUS including its incidence, etiopathogenesis, clinical profile and management. It consists of two types a) Diarrhoea associated i.e. classical also called D+ HUS b) Non-diarrhoea associated i.e. atypical also called D- HUS. D+ HUS is caused mostly by Escherichia coli or occasionally by Shigella dysenteriae. The causes of HUS are infections, genetic defects, systemic diseases and drugs. The atypical form commonly presents with recurrent or chronic persistent attack. Thrombotic microangiopathy (TMA), the pathologic hallmark, includes HUS, atypical HUS (aHUS), thrombotic thrombocytopenic purpura (TTP) which is characterized by endothelial cell damage and microvascular injury. In the vast majority of aHUS susceptibility factors are familial and not acquired. In D+ HUS, following an attack of diarrhoea or dysentery the child abruptly develops pallor, irritability, swelling of body, oligoanuria, hematuria, and hypertension. Central nervous system disturbances like seizure, obtundation and encephalopathy may occur but less common than aHUS or TTP. Diagnosis of HUS is established by presence of MAHA in the peripherl blood smear i.e. schistocytes, burr cells, helmet cells etc. Thrombocytopenia is nearly always seen. ARF is reflected in elevated blood urea and creatinine level. Coagulation studies like prothrombin time (PT), activated partial thromboplastin time (APTT), will be normal unlike disseminated coagulopathy (DIC). D-dimer level will be raised in HUS similar to DIC. Interestingly, direct Coomb’s test will be positive in Streptococcus pneumonia induced D- HUS. With excellent supportive care and often dialysis D+ HUS will show remarkable recovery whereas in addition plasmapheresis or plasma infusion outcome is poor in most of the D-HUS cases. Though incidence of gastroenteritis is very high in our country, only few patients may develop HUS, the reason of which remains unclear. The incidence of HUS as a cause for ARF in India may be reviewed further. Indiscriminate use of antimicrobials is to be avoided as far as possible to prevent HUS related mortality. Facilities for dialysis may be enhanced in most of the health care facilities in our country as a life saving measure to reduce HUS related mortality and morbidity.