Thank you for the query. Severe diarrhea can lead to considerable fluid loss and cause dehydration. The kidney perfusion is hampered in such situations, and the subject may develop a condition, which is known as Pre-renal failure or Acute Kidney Injury, in which there is a sudden, gross derangement of renal parameters (urea, creatinine) and decreased urinary output. However, such patients may be revived with generous intravenous fluid administration, at the right time, before irreversible renal damage occurs. Also, if a patient already has a diseased kidney due to some conditions like diabetes mellitus or hypertension, such a situation may cause an aggravation, also known as the Acute on Chronic renal failure. There is another type of infective diarrhea (due to E.coli) which may lead to the devlopment of Hemolytic Uremic Syndrome, which might also lead to failing kidneys. Old age and comorbidities, may aggravate any of the situations. Hope this helps you.