[The influence of empty-bed days on the median hospital stay in internal medicine]. 
To evaluate the epidemiology of delays in patients hospitalized in a department of internal medicine in a hospital of third level (high technology, end-stem of Spanish health system), its influences in hospital length of stay and the leading reasons which we named Gap Days.  We studied all patients admitted through emergency ward for internal medicine during Oct 93-June 94.  Gap Day was defined as the day passed as inpatient in which no intravenous route, isolation, artificial feeding, fever, impairing of clinic steady-state were needed or waited and any diagnostic tools were used.  We counted Gap Day from the second day and from de third day for histopathology that we ordered the explorations.  In a nonselected group days of delay to arrive written data were measured while the results were known for personal request.  144 patients had a mean length of stay of 9.52 (SD 5.41) days.  Gap Days occurred in 97 (67%) patients (Mean 3.85 SD 2.80) with a mean length of stay 10.71 SD 5.09 days, while patients without Gap Days had a mean length of stay of 7.14 SD 5.29 days (p < 0.001).  Patients with higher Gap Days were those with symptoms related to hematological system (p = 0.002), nephrourological system (p = 0.011) and a hematological diagnostic (p = 0.003) on admission.  On discharge patients with hematological diagnostic had also higher Gap Days (p = 0.017).  They had higher Gap Days also patients with two symptoms or more on admission (3.63 SD 2.96, p = 0.016), patients who lived alone (5.33 SD 3.42, p = 0.050) and patients with no concordance between diagnostic on admission and discharge (4.06 SD 3.41, p < 0.01).  In 37 patients written data arrived 2.14 SD 1.06 days later after to know the results for personal request.  Gap Days are an important factor to prolong the length of stay in internal medicine.  They are influenced by number of symptoms on admission, concordance between diagnostics on admission and discharge, hematological diagnostics and some social and functioning hospital factors.