INTRODUCTION: Nontraumatic acute abdomen (NTAA) in dialysis patients is a challenging issue. The aetiologies of NTAA vary considerably depending on the renal replacement therapy (RRT) modality. Although haematological parameters and contributing factors have been reported to be associated with outcomes for dialysis patients, their clinical effect on the length of hospital stay (LOS) remains unknown. METHODS: We retrospectively analysed 52 dialysis patients (peritoneal dialysis [PD], n = 33; haemodialysis [HD], n = 19) and 30 non-dialysis patients (as controls) between January 2011 and December 2014. To attenuate the selection bias, non-dialysis patients with NTAA were matched to cases at a ratio of 1:1 by age, gender and comorbidities (diabetes mellitus and hypertension). Their demographic characteristics, laboratory data, clinical assessment scores and LOS were analysed. RESULTS: The PD group exhibited a significantly higher neutrophil percentage, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR); longer LOS; and lower lymphocyte percentage and absolute lymphocyte count than the control group. After multivariate analysis adjustment, female gender, longer RRT duration and higher intact parathyroid hormone (iPTH) levels were associated with a lower probability of being discharged home. In the dialysis group, a higher iPTH level (> 313 μg/mL) was positively correlated with longer LOS. iPTH level combined with NLR can be used as a surrogate marker for predicting longer LOS (p < 0.001). CONCLUSION NTAA dialysis patients with female gender, longer RRT duration and higher iPTH levels are prone to experiencing longer LOS. In addition, the combination of iPTH and NLR is a significant determinant for LOS in NTAA dialysis patients.