Anuria is the production of urine less than 50ml every 24 hours. There are numerous causes for anuria, such as renal impairment, urinary tract obstruction (kidney stones), pharmaceutical agents or severe infections (septicemia).  Anuria is a symptom, not a disease. The patient often complains about weakness, fatigue, lack of appetite, vomiting tendency and dyspnea.

Oliguria is low urine output (less than 400ml per 24 hours for adults). It is due to acute renal impairment. Causes involved may be numerous, such as: 

• Dehydration
• Excessive Drop of Blood Pressure 
• Severe heart failure
• Renal diseases
• Nephrotoxic medication
• Urinary tract obstruction (due to kidney stones, cancer etc)