‘Lightning bum’ is surging – the 6 surprising causes and when you MUST see a doctor

EVER been minding your own business when a lightning bolt of pain lances through your bum? The sudden cramp can make you stagger, wince or gasp - but you might think you've imagined it all when it fades seconds later. But it's not your head. In fact, you've probably just been struck by proctalgia fugax...