It is suspected he has a lingering kidney infection left over from when he had the tooth abscess. This led to dehydration, which then led to constipation.
he has elevated BUN/Creatinine levels, partly due to loss of kidney function, partly due to dehydration. He is on fluids to correct the dehydration and antibiotics to deal with the infection. By this time tomorrow we will know what can be corrected and what is chronic kidney damage.