Constipation and Blood Test Result

I went to the Doctor yesterday to be seen for severe abdominal distention and bloating, sudden weight gain of 25 pounds, stingy sensation on the front of the lower legs, fatigue, constipation, winching pain in the left side, warm and tender abdomen.  They did a KUB and the results showed that I am severely constipated. They gave me Amitiza and Sentakot and I have taken it for two days.  When the doctor called this morning they didn't have my blood test results.  I went and got them and it showed that my BUN is high (30) range 7-25, AST/SGOT (40) range 9-39.  My RBC is low (3.82) range 4.20 to 5.20, high MCV (100.3) 80-96.  I know the BUN test looks at Kidneys and AST/SGOT looks at the Liver.  Are my kidneys and liver being damaged from the constipation or is this just from the toxins in my body from the constipation?  I feel horrible and I am tired of being tired.  Can anyone help me with this?