Abdominal bulge

Question
Hi! My parents dog is a very large German shepherd mix and he has developed a palpable, and now visual, bulge on the left side of his belly. He is 8-9 years old.  The bulge is closer to his hind leg and is not especially firm, but I try not to put too much pressure on it. It has grown steadily for the past 6 months and is now about the size of a small grapefruit. The dog has not shown any changes in behavior and seems normal otherwise. The bulge feels like it is internal, rather than superficial  The dog has an unusually long torso and has always had trouble with constipation.  It is an outdoor dog. Could it be a simple case of worms in the stomach?  He has about 15 acres to roam, so I haven't seen his feces.  Any other ideas?  My folks probably won't spring for a vet trip.  Thanks!!

Answer
Without an veterinarian's examination, an abdominal X-ray and possibly an ultrasound of the belly, it is difficult to diagnose anything on the internet.  A mass that big could suggest a tumor in the belly and the most common one in older dogs is called a hemangiosarcoma of the spleen.