An infant with history of diarrhoea 5 days back has urea 200 mg% and creatinine 5 mg%. The platelet count is 90000. Fragmented R.B.C s are found in the peripheral smear. The most possible diagnosis –
The clues in this question are -

History of diarrhoea        
Raised BUN and creatinine
Thrombocytopenia 
Fragmented RBCs in the peripheral smear  

All these suggest the diagnosis of HUS.
HUS
TTP
ITP
Hemolytic anemia