Nigerian President Umaru Yar'Adua has a heart condition, his spokesman has said, after he flew to Saudi Arabia on Monday for medical treatment.

尼日利亚总统Umaru Yar'Adua的发言人称，总统患有心脏疾病，星期一才刚飞往沙特接受治疗。

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The president has had a chronic kidney condition for at least 10 years

Mr Yar'Adua has acute pericarditis（急性心包炎）, or inflammation（发炎，红肿） of the lining² around the heart, his spokesman told the BBC.

He said the president, 58, was responding well to treatment. Officials earlier denied rumours³ that the president was seriously ill.

Mr Yar'Adua has had a chronic（长期的，慢性的） kidney condition for at least 10 years.

He has been unable to perform a number of official duties because of recurring⁴ health problems.

President Yar'Adua has twice been flown to Germany for emergency treatment and it is the second time he has visited hospitals in Saudi Arabia.

He has refused to say exactly what condition he suffers from, and has repeatedly said in interviews that his life is "in the hands of God".

BBC health reporter Michelle Roberts says most cases of pericarditis（心囊炎） clear up with rest and medication within a few weeks, although patients will initially⁵ need to be treated in hospital to check for complications.

Our reporter says occasionally pericarditis is triggered by cancer, which is something doctors need to check for.

Rarely patients may need surgery if the pressure around the heart becomes too great, a complication that could potentially be fatal, she adds.

Presidential spokesman Olusegun Adeniyi said the president felt pains after performing Friday prayers last week.

"At about 3pm Friday November 20, after he returned from the Abuja Central Mosque⁶ where he performed Muslim prayer, President Yar'Adua complained of a left-sided severe chest pain," he said, reports Reuters.

Mr Adeniyi said the initial diagnosis⁷ was pericarditis, which has since been confirmed.

Officials had earlier been quoted as saying the president intended to make the Hajj pilgrimage（朝圣，朝拜） to Mecca this week.

Analysts⁸ say his continued ill-health poses a problem for Nigeria's constitution.

If he were to step down or die, he would be replaced by Vice-President Goodluck Jonathan, who is from the country's southern Niger Delta⁹ region.

But according to the ruling People's Democratic Party's own formula for sharing power among the country's regions, the president must be a northerner.