Sun City - Louis Oosthuizen had to fight kidney stones the morning prior to the opening round of the Nedbank Golf Challenge as he fired to the top of the leaderboard at Sun City on Thursday.
SA's top ranked golfer carded a superb opening round of 63, nine shots under par, to take a three-shot lead into Friday.
Oosthuizen confessed that he almost did not play as he battled with kidney stones which resulted in treatment in Rustenburg on Wednesday.
"The whole of yesterday, I spent my time in the hospital in Rustenburg. At 3am, I was on my knees next to the toilet. I really thought I wasn't going to tee off this morning, I thought it was going to be a horrible week for me," Oosthuizen told reporters after his round on Thursday.
"I slowed everything down, it (the pain) wasn't that bad, it got better during the round... I'm very chuffed with the round."
Oosthuizen has had success before at the Gary Player Country Club as the then young Mossel Bay-born golfer claimed the Dimension Data Pro-Am in 2007.
The 37-year-old admitted that being back in Sun City had brought back good memories and helped his stellar bogey-free round.
"I just love the golf course, my first win on the Sunshine Tour was on this course at the Dimension Data. Every time I play here, it brings back good memories," said Oosthuizen.
Oosthuizen hopes to repeat his performance again in Round 2.
"I'm hoping for a pretty similar thing tomorrow gameplay wise, just try and get as many birdie opportunities as I can," he said.
Thomas Detry is Oosthuizen's nearest rival, as the Belgian golfer carded a 6-under 66.
South African's Ernie Els and Zander Lombard sit T4 alongside defending champion Lee Westwood on 4-under 68.
Leading scores after first round of EPGA Nedbank Golf Challenge Thursday at par-72 Gary Player Country Club in Sun City (RSA unless noted):
63 - Louis Oosthuizen
66 - Thomas Detry(BEL)
67 - Guido Migliozzi (ITA)
68 - Ernie Els, Zonder Lombard, Lee Westwood (ENG)
69 - Jorge Campillo (ESP), George Coetzee, Tommy Fleetwood (ENG), Joachim Hansen (DEN), Marcus Kinhult (SWE), Jason Scrivener (AUS), Sebastian Soderberg (SWE), Richard Sterne, Paul Waring (ENG), Oliver Wilson (ENG)
70 - Nacho Elvira (ESP), Martin Kaymer (GER), Kurt Kitayama (USA), Mikko Korhonen (FIN), Alvaro Quiros (ESP), Aaron Rai (ENG), Erik van Rooyen, Shubhankar Sharma (IND)