Generally speaking, the selection of membrane area is based on body surface area, while taking into account CKD-MBD, residual renal function, etc. The body surface area can be calculated using the Fujimoto formula below.
For example, a dialysis patient weighing 50 kg and 160 cm tall has a body surface area of 1.46 m² calculated using the Fujimoto formula. This patient should then choose a 1.5 m² dialyzer.
The membrane area is positively correlated with the body surface area. In response to differences in patient physique, the dialyzer membrane area is also divided into different types ranging from 0.5 to 2.5 m². For newborns and infants, a dialyzer with a smaller membrane area is required, and a blood purification method with less impact on the body (such as continuous hemodiafiltration) is selected. Currently in Japan, the minimum dialyzer membrane area is 0.1 m² and the maximum is 3.0 m².
Among Japanese people, few patients have a body surface area exceeding 2.5 m², and for patients with a body surface area exceeding 2.5 m², dialysis adequacy can be achieved by increasing blood flow, dialysis time, and dialysate flow rate.