Urinalysis, chest x-ray, serological tests for syphilis and HIV, and any additional required or requested investigations
are compulsory for Immigration medical examination for Canada.
according to Section 9.2 DMP Handbook:
Failure to apply the guidelines and instructions presented in the DMP Handbook and provided by CIC may require a re-medical.
Therefore in order to be in a safe side, you should go to DMP and tell that your urine was not collected for the lab test.