Tom Dumoulin saw his overall Giro d’Italia lead cut to 31 seconds after an unscheduled toilet stop during stage 16, which was won by Vincenzo Nibali.
The Dutch Sunweb rider began Tuesday with a two minutes 41 seconds advantage but stopped temporarily 33km from the finish to deal with “stomach problems”.
Controversially, the rest of the riders did not wait for him and carried on.
Italian Nibali’s stage win takes him third in the overall standings, behind Dumoulin and Colombian Nairo Quintana.
The defending champion held off Team Sky’s Mikel Landa in a sprint finish after escaping from Quintana during a high-speed final descent into Bormio.
Dumoulin said he was “very disappointed” and “very angry” immediately after the race, but later wrote on Twitter that he was not upset that the “other teams didn’t really wait”.
“A day to quickly forget! Good legs, but very disappointed that I lost two minutes because nature called,” he added.
“It was not the moment or the time in the race anymore to come to a complete shutdown because nature called me.”
Wednesday’s stage 17 is a 219km race from Tirano to Canazei.
Stage 16 result
1. Vincenzo Nibali (Ita/Bahrain) 6hr 24min 22sec
2. Mikel Landa (Spa/Team Sky) same time
3. Nairo Quintana (Col/Movistar) +12secs
4. Domenico Pozzovivo (Ita/AG2R) +24secs
5. Ilnur Zakarin (Rus/Katusha) +32secs
6. Davide Formolo (Ita/Cannondale) +1min 26secs
7. Bauke Mollema (Ned/Trek) +1min 35secs
8. Bob Jungels (Lux/Quick_Step) same time
9. Adam Yates (GB/Orica)
10. Thibaut Pinot (Fra/FDJ)
Overall classification after stage 16
1. Tom Dumoulin (Ned/Sunweb) 70hrs 14mins 48secs
2. Nairo Quintana (Col/Movistar) +31secs
3. Vincenzo Nibali (Ita/Bahrain) +1min 12secs
4. Thibaut Pinot (Fra/FDJ) +2mins 38secs
5. Ilnur Zakarin (Rus/Katusha) +2mins 40secs
6. Domenico Pozzovivo (Ita/AG2R) +3mins 05secs
7. Bauke Mollema (Ned/Trek) +3mins 49secs
8. Bob Jungels (Lux/Quick-Step) +4mins 35secs
9. Steven Kruijswijk (Ned/LottoNL) +6mins 20secs
10. Adam Yates (GB/Orica) +7mins