Background: Delayed gastric emptying (DGE) is the most prevalent complication after pancreatoduodenectomy (PD). The International Study Group of Pancreatic Surgery (ISGPS) published a consensus definition that defines DGE by clinical criteria (days of nasogastric intubation and first postoperative day solid food is tolerated). It has been suggested that diagnosis of DGE of clinical relevant grades B and C requires objectivation by a diagnostic test. Multiple tests are available to assess gastric emptying. Aim of this study was to review the literature of diagnostic studies that were directed to assess gastric emptying in the early post-operative period after PD and to derive potential universal diagnostic test criteria that define DGE. Methods: A systematic search by using the MESH terms ‘pancreatoduodenectomy’, ‘(delayed) gastric emptying’, ‘diagnostic techniques and procedures’ of the medical databases Medline and Embase was performed to identify relevant papers. Results: Twenty-six papers that examined gastric emptying after PD were identified. In these studies 6 different tests were used. Nine studies (n = 384 patients) used gastric emptying scintigraphy with a radionuclide-labelled test meal to directly measure gastric emptying rate. Six of these formulated (different) reference values of normal emptying rate. A contrast passage study was used in 6 studies (n = 164 patients), of which 1 formulated objective criteria of delayed contrast passage. Indirect measurement of gastric emptying by paracetamol absorption test (based on rapid absorption of paracetamol in the small intestine) was used in 6 studies (n = 122 patients), of which 1 provided reference values for delayed emptying. Six studies (n = 109 patients), 4 from 1 center, indirectly assessed gastric emptying function by manometry (measuring gastric contraction pattern [phase III of the migrating motor complex]). Two studies (n = 124 patients) assessed gastric function by H2 breath test (measuring small bowel transit time), and another 2 studies (n = 9 patients) by electrogastrography. The studies’ heterogeneity in methodology and DGE definitions and lack of correlation with the clinical situation hampered defining universal criteria for the different diagnostic tests.Conclusions: Direct measurement of gastric emptying after PD by scintigraphy seems the most acknowledged test that might diagnose DGE. However, universal criteria could not be deducted due to the heterogeneous methodology of the different studies and lack of correlation with the clinical situation. Further studies are needed to establish these criteria and to determine the exact role of a diagnostic study in defining DGE.