Is the prayer of a patient suffering from fatty liver, irritable bowel syndrome, gases, abdominal fermentation, pain, and constipation, which causes him to lose his devotion and concentration in prayer, valid?

Humility (Khushu') and focus are very important in prayer; they are its spirit and its fruit. However, Allah the Almighty did not make them a condition for the prayer's validity. Thus, a Muslim should strive to achieve humility in prayer and will not be held accountable for what is beyond their capacity.