膀胱上口，《灵》《素》未言有无，后世聚讼纷纭，或言有上口而无下口者，乃以“气化则能出”之句而误会也，若
无下口，焉得气一化则遂若此通利哉？是无下口之说不必论矣。或言有下口而无上口者，张景岳、李士材俱主是说。因
景岳、士材之书，近世风行海内，故人皆以为无上口矣。第无上口，则交肠之易位而出者，粪从何处入于膀胱乎？张三
锡以为上下俱有口者是矣，但语焉而未详也。夫水道既从小肠下口以入膀胱，则清浊不分者，何独并于大肠之水泻，人
所常有，而粪入膀胱之交肠，患者甚少乎？谛思其故，必系膀胱有上口而常闭，乃为平人之常，水之入于膀胱者，仍是
三焦化入，而非从上口以入者也。或腑气大虚，则力乏而窍不能闭，或邪热伤腑，则热主开泄而窍亦不能闭，以致粪从
小肠下口入于膀胱上口，并随小便而出矣，譬如人身之外窍，亦有常闭而不通者，脐孔与两耳、两乳，无故则常闭而不
开，有故则或出脓血，或通乳汁，膀胱之上口，亦可以类推矣。世人皆以为无上口者，一则宗景岳、士材之书，一则见
兽脬之止有下口也。不思天地之生物，各有不同者，如毛虫则五脏俱全，羽虫则无肺而无前阴，即人身亦有不同者，男
子肋骨二十有四，女子肋骨二十有八，男子头骨八块，女子头骨六块，人与人尚有异焉，人与兽岂无异乎？
膀胱的上口，《灵枢》和《素问》中并未明确说明其是否存在，后世对此争论不休。有人说只有上口而没有下口，这是误解了“气化则能出”这句话的意思；如果没有下口，气一旦气化怎么能如此通畅地排出呢？因此，没有下口的说法是不必讨论的。
有人说有下口而没有上口，张景岳和李士材都支持这种观点。因为景岳和士材的书籍在近世风行全国，所以人们都认为膀胱没有上口。但是，如果没有上口，那么发生交肠病（肠道与膀胱位置互换或相通）时，粪便从哪里进入膀胱呢？张三锡认为上下都有口才是正确的，但他说得不够详细。
既然水道从小肠的下口进入膀胱，那么清浊不分的情况，为什么唯独伴随大肠的水泻常见于人，而粪便进入膀胱的交肠病却很少见呢？仔细思考其中的原因，一定是因为膀胱有上口且平时处于闭合状态，这才是健康人的常态。水液进入膀胱，仍然是由三焦气化作用转化而入，而不是从上口进入的。
如果腑气极度虚弱，力量不足导致窍道无法闭合；或者邪热损伤腑脏，热性主开泄，导致窍道也无法闭合，致使粪便从小肠下口进入膀胱上口，并随着小便一起排出。这就像人体体表的孔窍一样，也有平时闭合不通的情况，比如肚脐眼、两耳、两乳，无故时通常闭合不开，有病时则会流出脓血或分泌乳汁。膀胱的上口，也可以这样类推。
世人之所以都认为膀胱没有上口，一方面是因为尊崇景岳、士材的著作，另一方面是因为看到动物膀胱只有下口。他们没考虑到天地所生的生物，各有不同之处。例如毛虫类五脏俱全，羽虫类没有肺也没有前阴；即使是人身也有不同，男子肋骨有二十四根，女子肋骨有二十八根；男子头骨八块，女子头骨六块，人与人尚且有差异，人与动物难道没有区别吗？
The upper orifice of the Bladder (Pang Guang, 膀胱) is not explicitly mentioned as existing or non-existing in the *Ling Shu* (Spiritual Pivot) and *Su Wen* (Basic Questions), leading to endless debates in later generations. Some argue that there is an upper orifice but no lower orifice; this is a misunderstanding of the phrase "when Qi transforms, it can exit." If there were no lower orifice, how could the Qi transform and discharge so smoothly? Therefore, the theory that there is no lower orifice need not be discussed.
Others argue that there is a lower orifice but no upper orifice, a view supported by Zhang Jingyue and Li Shicai. Because the works of Jingyue and Shicai became popular throughout the country in recent times, people generally believed that the Bladder has no upper orifice. However, if there were no upper orifice, in cases of *Jiao Chang* disease (Intestinal-Bladder Fistula/Displacement), from where would feces enter the Bladder? Zhang Sanxi considered the view that both upper and lower orifices exist to be correct, but his explanation was not detailed.
Since water pathways enter the Bladder via the lower orifice of the Small Intestine, why is it that when clear and turbid substances are not separated, it commonly accompanies watery diarrhea from the Large Intestine, whereas *Jiao Chang* disease, where feces enter the Bladder, is rare? Upon careful consideration, the reason must be that the Bladder possesses an upper orifice which is normally closed; this is the normal state of a healthy person. Water entering the Bladder is transformed and entered through the Qi transformation of the Triple Burner (San Jiao, 三焦), not through the upper orifice.
If the Qi of the Fu organs is severely deficient, lacking strength to keep the orifice closed, or if pathogenic heat damages the Fu organ, causing the orifice to open due to the dispersing nature of heat, then feces may enter the upper orifice of the Bladder from the lower orifice of the Small Intestine and be discharged along with urine. This is analogous to the external orifices of the human body, which also remain normally closed and unpatent. For instance, the umbilicus, ears, and breasts are usually closed unless pathology exists, at which point pus/blood or milk may be secreted. The upper orifice of the Bladder can be inferred similarly.
People generally believe there is no upper orifice for two reasons: first, they revere the works of Jingyue and Shicai; second, they observe that animal bladders only have a lower orifice. They fail to consider that living beings created by Heaven and Earth vary greatly. For example, hairy animals possess all five Zang organs, while feathered animals lack lungs and anterior yin openings. Even among humans, differences exist: men have twenty-four ribs, while women have twenty-eight; men have eight cranial bones, while women have six. Since differences exist between individuals, how much more so between humans and animals?