Severe abdominal pain 18 month old

[wonderingmum]

11 days ago my 18 month old son has bright red blood (approx 5ml max) in the rectal area of a wet but not soiled diaper.  This happened with 2 diapers in a row.
As he was happy and healthy with no other symptoms I was not too worried.  4 days ago he had severe colic like abdominal pain and a fever.  He had the pain for about 20-30 mins then it went.  He was still unhappy and in a little pain then an hour later it happened again the 3rd time I took him to the after hours doctor but it had stopped by the time we arrived. He said tummy felt fine and prescribed paracetamol.  The next  day he was fine all day but I kept giving him paracetamol for fever. The morning after, it happened again so I took him straight to the hospital accident and emergency.  They kept him in for observation and gave ibuprofen for the pain and did a urine test.
Today 2 days later the results came back with bacterial infection but WBC is normal.  He is still feverish and wakes crying in the night - not the agonizing pain but fever and not happy.
The doc has ordered an ultra sound but that will be weeks away.
Any ideas what is wrong with my boy??

[margypops]

If the urine test came back positive for the infection they gave him meds , sounds like it is taking its course .

[wonderingmum]

His bowel motions are normal in frequency and consistancy....

[margypops]

Could it be food related, has he eaten anything different before this started ?,

[margypops]

As to the blood , has he been constipated , it may also cause tummy pains and gas .however it would not cause fever . It does sound like a bacterial infection ..so all they ate treating him with is Iburofen and you have to wait weeks?