We thank you for your question. As you state, the standardized Peritoneal Equilibration Test (PET) is based on the work by Twardowski in which the fill volume was 2 liters (1).
 
We are not aware of a guideline recommending a minimum fill volume for a PET. The authors of the European Renal Best Practice Guidelines advise: “For the testing of the peritoneal membrane transport characteristics, using the usual fill volume of the individual patient is recommended, as this reflects what is going on in this patient in clinical practice. It should be considered, however, that changing fill volume can change the observed transport status” (2, page 2056).
 
As an example, we answered a related question almost a year ago. The question posted to the ISPD website then was concerning the PET for a patient whose weight was 30 kg and usual PD prescription was a 1 L fill. Our one suggestion then was to try to obtain access to a computer program such as PD Adequest, which will allow you to enter different fill volumes. In that situation, we advised that the patient’s 1 L fill volume should be entered. Note that the ensuing PET result will be based on predictive modeling and called a “Simulated PET” (as compared to an “Actual PET”).
 
1.Twardowski ZJ, Nolph KD, Khanna R et al. Peritoneal equilibration test. Peril Dial Bull 1987; 7: 138-147.
 
2. Van Biesen W, Heimburger O, Krediet R, Rippe B, La Milia V, Covic A, Vanholder R, ERBP Working Group on Peritoneal Dialysis. Evaluation of peritoneal membrane characteristics: clinical advice for prescription management by the ERBP working group. Nephrology Dialysis Transplantation. 2010 Jul 1;25(7):2052-62. Available at: https://academic.oup.com/ndt/article/25/7/2052/1870054