From MedlinePlus Genetics
The life expectancy of people with MMIHS is shorter than normal, often due to malnutrition, overwhelming infection (sepsis), or the failure of multiple organs.

Another abnormality in some people with MMIHS is intestinal malrotation, in which the intestines do not fold properly. Instead, they twist abnormally, often causing a blockage. Individuals with MMIHS can also develop problems with the kidneys or the ureters, which are the ducts that carry urine from the kidneys to the bladder.

The reduced ability to pass urine also contributes to painful distention of the abdomen. Many people with MMIHS require placement of a tube (urinary catheter) to remove urine from the bladder.

After birth, the continued impairment of peristalsis (hypoperistalsis) often causes a digestive condition called intestinal pseudo-obstruction. This condition, which mimics a physical blockage (obstruction) of the intestines but without an actual blockage, leads to a buildup of partially digested food in the intestines. This buildup can cause abdominal swelling (distention) and pain, nausea, and vomiting. The vomit usually contains a green or yellow digestive fluid called bile. Because digestion is impeded and the body does not get the nutrients from food, nutritional support is usually needed, which is given through intravenous feedings (parenteral nutrition). While some affected individuals rely solely on intravenous feedings, others require it only on occasion. Long-term use of parenteral nutrition can lead to liver problems.

Some of the major features of MMIHS can be recognized before birth using ultrasound imaging. Affected fetuses have an enlarged bladder (megacystis) because it does not empty. In addition, the large intestine (colon) is abnormally narrow (microcolon) because of a shortage of functional muscle lining it. Intestinal and bladder problems persist throughout life.

Megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is a severe disorder affecting the muscles that line the bladder and intestines. It is characterized by impairment of the muscle contractions that move food through the digestive tract (peristalsis) and empty the bladder.  https://medlineplus.gov/genetics/condition/megacystis-microcolon-intestinal-hypoperistalsis-syndrome