Hello, * The post-surgical issue with dark urine and severe pain, indicates possible inflammation inside the abdomen, most likely biliary system. * In my clinic, I recommend to undertake basic lab panel and later if requires MRI of the abdomen & pelvis as it provides much-needed information than right now. * Diet advise would be bland, vegan diet with plenty of liquids till the recovery. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Bhagyesh V. Patel, General Surgeon