KIRK: I need your help. I don’t know what to do. I’m shaking like a spastic colon.
A spastic colon, or colon spasm, describes the situation when the muscles around the small and large intestines spontaneously and suddenly contract, causing pain, cramping, bloating, and an urgent need to use the toilet.
This common condition is strongly associated with irritable bowel syndrome (IBS), which is sometimes known as spastic colon, even though not everyone with IBS gets colon spasms, and not everyone with colon spasms has IBS. It is not always clear what causes it, although a change of diet, more exercise, managing stress, and sometimes medications may be offered as part of a treatment plan.
Kirk’s phrasing may suggest that he suffers from IBS himself.
The Annotated Gilmore Girls 