The characters combine to form “pull stomach,” an incredibly descriptive phrase for the experience of diarrhea, where something feels like it's being forcefully pulled out from the abdomen.
While 拉肚子 is a straightforward medical term, its usage is tied to Chinese cultural views on food and health. In China, digestive health is a frequent topic of conversation, and it's often linked directly to what one has eaten. It's very common to hear someone blame a case of 拉肚子 on a specific meal, particularly food considered “unclean” (不干净 - bù gānjìng), “oily” (太油 - tài yóu), or something that has caused an imbalance according to Traditional Chinese Medicine (TCM). For example, eating too much “cold” (凉 - liáng) food like watermelon or raw vegetables, especially on a hot day, might be blamed for causing diarrhea. This contrasts with the Western biomedical approach, which would focus exclusively on bacteria or viruses. Therefore, when someone says they have 拉肚子, the immediate follow-up question is often “你吃了什么？” (Nǐ chī le shénme? - What did you eat?). This directness is also a cultural point. While an English speaker might use a euphemism like “I have an upset stomach” or “I'm not feeling well,” a Chinese speaker will typically just say “我拉肚子了” (Wǒ lā dùzi le) without any sense of it being crude or TMI (too much information). It's simply a factual statement about one's health.
拉肚子 is the most common and colloquial term used in virtually all daily situations.