The following looks at systematic absorption of hydrocortisone rectal foam administration. Should be very similar to your budesonide foam.
"Only a very small part of the rectal dose (100 mg) was absorbed; the mean absolute bioavailability was 3.1% in healthy volunteers and 4.5% in patients."
Source:
Pharmacokinetics and rectal bioavailability of hydrocortisone acetate after single and multiple administration in healthy subjects and patients
https://pubmed.ncbi.nlm.nih.gov/11361050/