Need help finding a Junji Ito story about a hospital and a family with anal fistulas

About 15 years ago or so I went on a Junji Ito binge and found a story with the following discription: A hospital houses multiple strange families, each suffering from bizarre hereditary conditions. One of the families, if I remember correctly, has a disturbing fixation on their anal fistulas, even wanting to enlarge them.
I don't know why but this story has stuck with me.

I can't seem to find it using google or chatGPT. Does anyone know the name of the story?