VATICAN CITY — For an institution devoted to eternal light, the Vatican has shown itself to be a master of smokescreens since Pope Benedict XVI’s shock resignation announcement.

On Thursday, the Vatican spokesman acknowledged that Benedict hit his head and bled profusely while visiting Mexico in March. Two days earlier the same man acknowledged that Benedict has had a pacemaker for years, and underwent a secret operation to replace its battery three months ago.

And as the Catholic world reeled from shock over the abdication, it soon became clear that Benedict’s post-papacy lodgings have been under construction since at least the fall. That in turn put holes in the Holy See’s early claims that Benedict kept his decision to himself until he revealed it.

Vatican secrecy is legendary and can have tragic consequences — as the world learned through the church sex abuse scandal in which bishops quietly moved abusive priests without reporting their crimes.

And the secrecy is institutionalized from such weighty matters to the most trivial aspects of Vatican life.

“You have to understand that actually every Vatican employee and official takes an oath of secrecy when they assume their job,” said John Thavis, author of “The Vatican Diaries,” an investigation into the workings of the Holy See. “And this isn’t something that is taken lightly. They swear to keep secret any office matters and anything pertaining to the pope.”

One of the most famous cases of Vatican secrecy was the Holy See’s efforts to cover up the fact that Pope John Paul I’s dead body was discovered by a nun. The eventual revelation helped fuel conspiracy theories over the death of the pope who ruled for only 33 days in 1978.

The Vatican is so obsessed with secrecy that the first and only official confirmation that John Paul II had Parkinson’s disease was in his death certificate.

The Vatican justifies itself by arguing that its officials are holders of the divine truth, unaccountable to worldly laws. In particular, the pope’s word is the final say on any issue — infallible on some doctrinal matters. But groups representing sex abuse victims, and other Catholics angered by the scandal, have been demanding modern standards of accountability and calling for reforms.

The Vatican brushed aside criticism for keeping quiet about the pope’s December pacemaker procedure, on grounds it was “routine.” One Vatican official said making the operation public would simply have led to a big and unnecessary commotion about the pope’s health. “You can imagine the satellite dishes in St. Peter’s square,” said the official, who spoke on condition of anonymity because he is not authorized to speak to the media.

The front-man for the church’s dance of concealment and disclosure: Vatican spokesman The Rev. Federico Lombardi. In his briefings, Lombardi has been forced into the uncomfortable situation of keeping silent on aspects of the pope’s health and future, only to backpedal when confronted with reports in Italian newspapers.

In the latest disclosure, Turin’s La Stampa newspaper reported Thursday that Benedict hit his head on a sink and bled profusely when he got up in the middle of the night in an unfamiliar bedroom in Leon, Mexico. The report said papal blood stained Benedict’s hair, his pillow and the floor.

Lombardi confirmed the incident but denied it played any role in the pope’s resignation. Still, suspicions are bound to be whetted, since the Vatican newspaper L’Osservatore Romano reported this week that Benedict had taken the decision to resign after the Mexico-Cuba trip, which was physically exhausting for the 85-year-old pope.

Then there’s the question of how many people knew of Benedict’s decision to retire.

On the day of the announcement the Vatican cast it as a bolt from the blue, saying almost nobody knew but Benedict himself. Soon, however, prominent clergymen — one not even Catholic — began changing the tone and saying they were not surprised.

“Knowing the pope well, there was something in the air that this decision of the pope was possible,” said Archbishop Piero Marini, master of papal ceremonies under Pope John Paul II. “So it was not a shock.”

Even the retired Arcbishop of Canterbury, Bishop Rowan Williams, says that based on his last meeting with Benedict a year ago he was not surprise at the decision to step down.

“Because of our last conversation I was very conscious that he was recognizing his own frailty and it did cross my mind to wonder whether this was a step he might think about,” Williams told Vatican Radio.

Renovation work on a convent previously occupied by cloistered nuns has been going on in secret since at least last fall, an issue apparently causing grumbling among cardinals about the choice of arrangements and whether Benedict’s presence on Vatican grounds will allow the retired pope to wield too much influence on his successor.

“I don’t think there was a consultation of the College of the Cardinals about this,” Lombardi said Wednesday, deflecting questions about Benedict’s living arrangements. “The decision and the process of the decision was very limited in the number of persons involved.”

That points to another aspect of Vatican secrecy: The habit of different wings of the Holy See jealously concealing information from one another.

“There is very little cross communication within Vatican departments,” Thavis said, “so one department may know something but that does not mean that the Curia office down the hall knows about it as well.”