Having four hospitalized patients over the weekend is rare. Four cats: two icteric (jaundiced, see my very first post) and two obstructed (urinary).
Jaundice is not a disease, but rather a symptom of disease. Almost invariably caused by liver disease - all sorts of liver disease - but a patient can also become jaundiced from pancreatitis (inflammation of the pancreas) or when red blood cells are destroyed by the immune system (called immune-mediated hemolytic anemia).
The obstruction in two of the cats were urinary in nature. Typically, in cases of urinary obstruction, crystals or actual stones (called urolithes) block the urethra and prevent a cat from urinating. It can be partial or complete. Imagine not being able to pee. Typically male cats are affected because, just like men, the urethra is longer and thinner and therefore easier to get blocked. Feeding a cat a high-quality, low-ash diet can prevent crystals from forming.
One of the jaundiced cats is not doing well but the other three will far likely recover.
This is a radiograph of a cat with a moderately distended bladder from urinary obstruction.