The Surdial X haemodialysis machine is manufactured by Nipro Corporation. The information in this notice relates to all serial numbers of this model. The MHRA are aware of instances of Surdial X machines removing excess fluid via ultrafiltration outside of its specification. There is a risk to patients who are unable to tolerate excess fluid removal. Haemodialysis is a treatment given to patients whose kidneys stop working properly. The machines and associated items such as filter and tubing lines perform the function of the human kidney, to clean and filter unwanted substances and fluids from the blood. The manufacturer has previously issued a Field Safety Notice (Nipro FSCA20210730) and are continuing to investigate this matter. The likely root cause is unexpected wear of the ultrafiltration pump.