My Husband Has Suffered For Months With Chronic Abdominal Wall

My husband has suffered for months with chronic abdominal wall pain across a broad area centered between the sternum and umbilicus. His doctor seems unconcerned about it. His liver function is normal on bloodtests, kidney function low. His abdomen is distended, we all suppose due to fat and water retention (he has CHF and DM type 2, central obesity, has a pacemaker.) If cutaneous nerve entrapment is supposed to be on the right, thats not it. Would arterial ischemia or hernia or abscess or cancer show up on his regular blood tests? Should he get a colonoscopy? Is there a certain specialist for whom we should get a referral from his primary? Do you have another idea?