Italian Matteo Berrettini battled stomach cramps and frequent trips to the toilet before winning his way through to the second round of the Australian Open on Monday.

The seventh seed held on to beat American Brandon Nakashima in a three-hour-10-minute struggle 4-6, 6-2, 7-6 (7/5) 6-3 on Margaret Court Arena.

Berrettini, who lost to Novak Djokovic in last year's Wimbledon final, called the trainer after losing the opening set but rallied to take the match in four sets.

Berrettini scrawled "Imodium grazie!" on the courtside camera lens after completing his victory, but not until after making three emergency toilet breaks during the match.

The 25-year-old will now face American wild card Stefan Kozlov in the second round.

"I've been feeling sick with my stomach, let's say that," Berrettini said.

"It was really hard to play, especially the third and fourth set."