Tom Dumoulin survived an untimely call of nature to hold on to the lead of the Giro d'Italia as Vincezno Nibali claimed a narrow stage 16 victory ahead of Mikel Landa.
Dumoulin went into Tuesday's 222-kilometre ride from Rovetta to Bormio with a lead of two minutes and 41 seconds over his nearest challenger Nairo Quintana (Movistar).
But the Sunweb rider's hopes looked set to be dealt a significant and unusual blow as he was forced to pull over to a stop and strip down his kit to relieve apparent stomach discomfort with 33km remaining.
That stoppage saw the general classification group, featuring Quintana, Nibali (Bahrain - Merida) and Thibaut Pinot (FDJ) gain significant time on the Dutchman.
Nibali eventually caught Team Sky rider Landa, the sole survivor of a break that had featured more than 20 riders, with 10km left, and that pair had a lead of more than three minutes over Dumoulin at one point.
But, as Nibali edged Landa in a sprint to the line, Dumoulin recovered to come home just two minutes and 18 seconds down.
Quintana finished third - 12 seconds off the pace - giving Dumoulin a lead of 31 seconds in the overall standings after an extremely trying day.
"I had to fight and fight and fight, and take conclusions after the finish. That's what I did. I'm very disappointed."
GOOD DAY / BAD DAY
Though he did not claim the stage victory, Landa received ample reward for his magnificent efforts. The Spaniard earned the Cima Coppi prize for topping the highest peak in the Giro - the Passo dello Stelvio - and was also first up the final ascent to claim maximum King of the Mountains points and the climber's jersey before being caught by Nibali on the descent.
The Cipo Scarponi prize, named after Astana rider Michele Scarponi who was tragically killed in training for the Giro, went to his former team-mate Luis Leon Sanchez for cresting the summit of the first climb, the Passo del Mortirolo
Dumoulin may have kept hold of the Maglia Rosa, but his advantage has been cut significantly and he will need to recover quickly from any ailment ahead of stage 17 on Wednesday.
1. Vincenzo Nibali (Bahrain - Merida) 6:24:22
2. Mikel Landa (Team Sky)
3. Nairo Quintana (Movistar) +0:12
4. Domenico Pozzovivo (AG2R La Mondiale) + 0:24
5. Ilnur Zakarin (Katusha Alpecin) +0:32
1. Tom Dumoulin (Team Sunweb) 70:14:18
2. Nairo Quintana (Movistar) +0:31
3. Vincenzo Nibali (Bahrain - Merida) +1:12
4. Thibaut Pinot (FDJ) +2:38
5. Ilnur Zakarin (Katusha Alpecin) +2:40
1. Fernando Gaviria (Quick-Step Floors) 325
2. Jasper Stuyven (Trek Segafredo) 192
3. Sam Bennett (Bora-Hansgrohe) 117
KING OF THE MOUNTAINS
1. Mikel Landa (Team Sky) 124
2. Luis Leon Sanchez (Astana) 108
3. Omar Fraile (Dimension Data) 85
There is no respite for Dumoulin or any of the field, with a wavy 219km route from Tirano to Canazei featuring three technical climbs making up stage 17.