question about medicines my daughter is taking

Dear Med Help,
   my 13-yr-old daughter has been diagnosed with endometriosis (March 23rd), which causes pain for her. She was recently put on Aygestrin, which seems to have stopped her pain for the time being. However, due to the recurring nature of endometriosis-associated pain, we anticipate that her pain may return. During her pain episodes, she takes diclofenac on an as-needed basis, which is effective at stopping her pain every day, but only after the 3rd dose. When she is in pain, she takes 50 mg. of diclofenac in the morning, 25 mg. three hours later, and 25 mg. three hours after that. About an hour later, she is out of pain for the rest of the day. She then takes 50 mg at bed-time, for a total of 150 mg. per day. She has taken diclofenac on a periodic basis since Feb. 10th, 2011, usually for up to 2-3 weeks at a time (she stops taking diclofenac when her pain episode subsides). My question is:
1) Is diclofenac safe? We know about the possible gastro-intestinal side effects, but the diclofenac is enteric-coated and has never caused my daughter any stomach or intestinal problems (no pain, no blood in stool, etc.). I also know from my own research that GI effects (e.g., gastritis, ulceration) with diclofenac are rare, especially in young adolescents (the article I came across reported a .03% incidence of gastrointestinal effects due to diclofenac). I have heard different things about diclofenac from different doctors. I recently heard from one pediatric anesthesiologist that long-term use of diclofenac can cause potential liver and/or kidney problems, and this doctor ordered blood tests to test for liver and kidney function. I was under the impression that liver and/or kidney problems are rare for this age group (13 years old); besides, she has only been using it since February, and I thought that it took years of use of diclofenac (and other NSAIDS) before they could potentially cause liver and/or kidney problems.
What is your opinion on diclofenac?

[Burton Dunaway, PharmD]

The safety and effectiveness of diclofenac in pediatric patients has not been established. But, severe complications such as liver or kidney problems are extremely rare in adults. Renal toxicity is usually only a concern in patients with impaired kidney function, heart failure, liver dysfunction, the elderly, and in patients taking other medications that affect the kidney. Liver  complications can occur at any time in patients taking diclofenac, but routine liver tests  will usually alert the physician before irreversable organ damage occurs. When NSAIDS such as diclofenac are use intermittently, the risk of complications are reduced.