Foreman and Chase do the colonoscopy. While poor Ian gets to hear all this, Chase tells Foreman about how come every time someone comes in with Ester-like symptoms, House assumes it's Erdheim-Chester and makes them run all kinds of horrible tests before it turns out that the patient doesn't have Erdheim-Chester or anything remotely serious at all. Outside, Cameron tells Ian's parents that they're testing Ian for something that they're sure he doesn't have. Shouldn't they be in the room holding Ian's hand while two strangers shove a camera up his ass? Foreman sees something that could be a purple papule. Chase argues that it's just a blood blister, and that he doesn't think they should bother with it. Foreman wisely ignores him and does a biopsy.
Over in the lab, Cameron checks the growth under a microscope while Chase paces around, still hoping to be done with this so he can go back to the party. Cameron tells him that while his swimming with sharks story is good, she doubts that woman is waiting for Chase; this gets Cameron a laugh out of Foreman. Apparently Chase has used that line on both of them before. House limps in and asks them what the colonoscopy came back with. It wasn't one of House's purple papules after all -- just Chase's blood blister. I'm sure it still sucks to have blood blisters in your colon, though. House looks at the slide himself and has to admit that there's no Erdheim-Chester there. But he won't give up; he just figures they're looking for something else. A kidney biopsy is next on his roster of painful and seemingly unnecessary tests, especially since Ian's kidneys are thus far perfectly healthy. Chase snaps that Ian isn't Ester and that this is a waste of time. "You're testy when you don't get any fuzz," House retorts in a line that I can't believe got past the censors.
House and Chase enter Ian's room. Chase tells the parents that their kid was negative for Erdheim-Chester. Everyone is relieved, until House shows off Ian's catheter bag, which is filled with brown urine. Chase has to admit that things don't look good for Ian's kidneys after all. Worried glances are exchanged around the room for five minutes before we finally go to commercial.
On the Whiteboard, Ian's newest symptom matches Est(h)er's. House asks what, besides Erdheim-Chester, could have killed Ester and is currently killing Ian. Chase suggests E. coli, which House rejects because he tried it with Ester and it didn't work and he's still certain that they have the same thing. Several suggestions are thrown out for not matching both cases until Cameron hits on lymphoma. House pauses at this and looks disappointed in himself, because it's a good explanation for both cases that he never checked for when Ester was around. He sends the Cottages off to test Ian for it. Cameron mentions paging Cuddy about her patient's progress, which House, of course, orders her not to do. Instead, he'll have Wilson "keep her busy" at the poker table.